DE10325488A1 - Preparing a multielement oxide material useful as catalyst active material, by thermally treating dry blend of ammonium ions and elemental components of oxide material, other than oxygen in atmosphere having low content of molecular oxygen - Google Patents

Abstract

Preparation of catalytically active multielement oxide materials containing niobium and/or tungsten, molybdenum, vanadium, and copper, includes thermally treating a dry blend containing ammonium ions and the elemental components of oxide material, other than oxygen at elevated temperature in an atmosphere having low content of molecular oxygen. A portion of ammonium ions in the dry blend is decomposed at >=160[deg]C with liberation of ammonia. Preparation of catalytically active multielement oxide materials containing niobium and/or tungsten, molybdenum, vanadium, and copper, includes thermally treating a dry blend containing ammonium ions and the elemental components of multielement oxide material, other than oxygen at elevated temperature in an atmosphere having a low content of molecular oxygen. A portion of ammonium ions contained in the dry blend is decomposed at >=160[deg]C with liberation of ammonia. Thermal treatment includes heating the dry blend at =10[deg]C/minute to a decomposition temperature (preferably 240-360[deg]C) and holding at this temperature until >=90 mole% of the total amount of ammonia liberated in the entire course of thermal treatment have been liberated; reducing the molecular content in the atmosphere where thermal treatment takes place is reduced to =0.5 vol.% not later than when the intimate dry blend has reached 230[deg]C and maintaining this low oxygen content until >=20 mole% of the total amount of ammonia liberated in the entire course of thermal treatment have been liberated; taking the dry blend at =10[deg]C/minute out of the decomposition temperature and into the calcination temperature of 380-450[deg]C not earlier than when >=70 mole% of the total amount of ammonia liberated in the entire course of thermal treatment have been liberated; and increasing the content of molecular oxygen in the atmosphere to greater than 0.5-4 vol.% not later than when 98 mole% of the total amount of ammonia liberated in the entire course of thermal treatment have been liberated, and calcining the dry blend at this increased oxygen content of atmosphere in the calcination temperature. The molar fraction of molybdenum is 20-80 mole%, based on the total amount of all elements other than oxygen in the multielement oxide material. The molar ratio of molybdenum to vanadium is 15:1 - 1:1. The molar ratio of molybdenum to copper is 30:1 - 1:3. The molar ratio of molybdenum to the total amount of tungsten and niobium is 80:1 - 1:4.

Description

This The invention relates to a method for producing catalytically active multielement oxide materials, the at least one of the elements Nb and W and the elements Mo, V and Cu contain, the molar Share of the element Mo in the total amount of all of oxygen various elements of the catalytically active multi-element oxide mass Is 20 mol% to 80 mol%, the molar ratio of contained in the catalytically active multielement oxide mass Mo to contained in the catalytically active multielement oxide mass V, Mo / V, is 15: 1 to 1: 1, the corresponding molar ratio Mo / Cu 30: 1 to 1: 3 and the corresponding molar ratio Mo / (total amount from W and Nb) is 80: 1 to 1: 4 and where one from starting compounds that of oxygen various elementary constituents of the multielement oxide mass contain as components, an intimate, also containing ammonium ions, Manufactures dry mix and this in a low in molecular oxygen the atmosphere with increased Temperature treated thermally, at least at temperatures ≥ 160 ° C. a subset of the ammonium ions contained in the intimate dry mixture is decomposed with the release of ammonia.

Also concerns present invention, a process for the preparation of acrylic acid heterogeneously catalyzed partial gas phase oxidation of acrolein using catalysts that mass the aforementioned multi-element oxide contained as catalytically active materials.

The The process described at the outset for the production of catalytic active multielement oxide materials are known as well as their use the available Multielementoxidmassen as active material in catalysts for the heterogeneous catalyzed partial gas phase oxidation of acrolein to acrylic acid.

From the DE-31 19 586 C2 is known to produce a catalytically active multielement oxide mass, which contains the elements Mo and V as a basic component, by producing an intimate, ammonium ion-containing, dry mixture from starting compounds which contain the elementary constituents of the multielement oxide masses, and this at 380 ° C thermally treated in a gas stream containing 1 vol .-% molecular oxygen.

The resulting multi-element oxides are used as active mass for catalysts recommended for the catalytic partial gas phase oxidation of acrolein to acrylic acid.

DATABASE WPI, Week 7512, Derwent Publication Ltd., London, GB; AN 75-20002 & JP-A 49097793 (Asahi Chemical Ind. Co.) September 19, 1974 recommends the thermal treatment of appropriate intimate dry mixtures for the production of relevant multielement oxide active materials with complete exclusion of molecular oxygen. The EP-A 113 156 recommends performing the thermal treatment in an air stream. The EP-A 724481 teaches to carry out the thermal treatment in such a way that the molecular oxygen content at any point in the thermal treatment in the (gaseous) treatment atmosphere is 0.5 to 4% by volume. In the exemplary embodiment, the molecular oxygen content in the thermal treatment atmosphere was 1.5% by volume.

In the exemplary embodiments of FIG EP-A 714700 the thermal treatment of the intimate dry mixture is carried out both in an air stream and in an atmosphere whose molecular oxygen content was 1.5% by volume.

The DE-A 10046928 , the DE-A 19815281 and the EP-A 668104 show that the multielement oxide active compositions mentioned at the outset, which have a multi-phase structure, are particularly suitable as active compositions for catalysts for the heterogeneously catalyzed partial oxidation of acrolein to acrylic acid if at least one phase is separately prepared for the preparation of the intimate dry mixture to be thermally treated and the thermal treatment is carried out in a gas atmosphere which continuously contains 1.5 or 1.4% by volume of molecular oxygen.

adversely The teachings of the prior art are that they are essentially all thermal treatment of the intimate dry mixture at one over the Duration of the thermal treatment essentially constant Recommend the content of molecular oxygen in the associated gas atmosphere.

So preserved relevant multielement oxide active materials are, however, capable of activity and selectivity when used as active compositions in catalysts for the heterogeneously catalyzed Partial oxidation of acrolein to acrylic acid is not fully satisfactory.

The The object of the present invention was therefore an improved Process for the production of relevant multielement oxide active materials for disposal according to which Multielement oxide active materials are obtained when used as active compositions in catalysts for the heterogeneously catalyzed Partial oxidation of acrolein to acrylic acid increased activity and increased selectivity of acrylic acid formation exhibit.

• – das innige Trockengemisch wird mit einer Temperaturrate von ≤ 10°C/min auf eine Zersetzungstemperatur im Zersetzungstemperaturbereich von 240°C bis 360°C erwärmt und so lange in diesem Temperaturbereich gehalten, bis wenigstens 90 mol-% der im Gesamtverlauf der thermischen Behandlung des innigen Trockengemischs aus dem innigen Trockengemisch bei Temperaturen oberhalb von 160°C insgesamt freigesetzten Gesamtmenge M^A an Ammoniak freigesetzt worden sind;
• – spätestens dann, wenn das innige Trockengemisch die Temperatur von 230°C erreicht hat, wird der Gehalt der (Gas) Atmosphäre A, in der sich die thermische Behandlung des innigen Trockengemisches vollzieht, an molekularem Sauerstoff auf einen Wert von ≤ 0,5 Vol.-% abgesenkt und dieser niedere Sauerstoffgehalt so lange aufrechterhalten, bis wenigstens 20 mol-%, bevorzugt wenigstens 30 mol-% und besonders bevorzugt wenigstens 40 mol-% der im Gesamtverlauf der thermischen Behandlung insgesamt freigesetzten Gesamtmenge M^A an Ammoniak freigesetzt worden sind;
• - frühestens dann, wenn > 70 mol-% (häufig wenn ≥ 75 mol-%, oder wenn ≥ 80 mol-%, oder wenn ≥ 85 mol-%, oder wenn ≥ 90 mol-%) der im Gesamtverlauf der thermischen Behandlung insgesamt freigesetzten Gesamtmenge M^A an Ammoniak freigesetzt worden sind, wird das innige Trockengemisch mit einer Rate von ≤ 10°C aus dem Zersetzungstemperaturbereich heraus – und in den Calcinationstemperaturbereich von 380 bis 450°C hineingeführt und
• – spätestens dann, wenn 98 mol-% bzw. 95 mol-% der im Gesamtverlauf der thermischen Behandlung insgesamt freigesetzten Gesamtmenge M^A an Ammoniak freigesetzt worden sind, wird der Gehalt der Atmosphäre A an molekularem Sauerstoff auf > 0,5 Vol.-% bis 4 Vol.-% erhöht

und das innige Trockengemisch bei diesem erhöhten Sauerstoffgehalt der Atmosphäre A im Calcinationstemperaturbereich calciniert.Accordingly, a process for the production of catalytically active multielement oxide compositions which contain at least one of the elements Nb and W and the elements Mo, V and Cu, the molar proportion of the element Mo in the total amount of all non-oxygen elements of the catalytically active multielement oxide composition being 20 mol -% (preferably 30 mol% or 40 mol%) to 80 mol%, the molar ratio of Mo contained in the catalytically active multielement oxide composition to V, Mo / V, 15: 1 to 1 contained in the catalytically active multielement oxide composition : 1, the corresponding molar ratio Mo / Cu 30: 1 to 1: 3 and the corresponding molar ratio Mo / (total amount of W and Nb) is 80: 1 to 1: 4 and in which starting compounds are those of oxygen contain various elementary constituents of the multi-element oxide mass as constituents, produce an intimate, also containing ammonium ion, dry mixture and this in a molecular sow Low-temperature (gas) atmosphere thermally treated at elevated temperature, with at least a portion of the ammonium ions contained in the intimate dry mixture being decomposed with the release of ammonia at temperatures ≥ 160 ° C., which is characterized in that the thermal treatment is carried out as follows:

• - The intimate dry mixture is heated at a temperature rate of ≤ 10 ° C / min to a decomposition temperature in the decomposition temperature range of 240 ° C to 360 ° C and held in this temperature range until at least 90 mol% of the total thermal treatment of the intimate dry mix from the intimate dry mix at temperatures above 160 ° C total amount M ^A of ammonia released;
• - at the latest when the intimate dry mixture has reached the temperature of 230 ° C, the content of (gas) atmosphere A, in which the thermal treatment of the intimate dry mixture takes place, of molecular oxygen to a value of ≤ 0.5 vol .-% lowered and this low oxygen content maintained until at least 20 mol%, preferably at least 30 mol% and particularly preferably at least 40 mol% of the total amount M ^A of ammonia released in the overall course of the thermal treatment have been released;
• - at the earliest if> 70 mol% (often if ≥ 75 mol%, or if ≥ 80 mol%, or if ≥ 85 mol%, or if ≥ 90 mol%) of the total heat treatment as a whole released total amount M ^A of ammonia, the intimate dry mixture is at a rate of ≤ 10 ° C out of the decomposition temperature range - and into the calcination temperature range from 380 to 450 ° C and
• - at the latest when 98 mol% or 95 mol% of the total amount M ^A of ammonia released in the overall course of the thermal treatment has been released, the content of molecular oxygen in the atmosphere A becomes> 0.5 vol.% up to 4% by volume

and calcined the intimate dry mixture at this increased oxygen content of atmosphere A in the calcination temperature range.

Needless to say, are in the inventive method the elements Mo, V, Cu and Nb and / or W (as well as all others possibly contained elements other than oxygen) in the obtainable according to the invention catalytically active multielement oxide mass in oxidic (and not contained in metallic, elementary) form.

The Content of the thermal according to the invention treating intimate dry mixture of ammonium ions is advantageously based on the total molar content of the intimate dry mixture on elemental constituents other than oxygen, later catalytic active multielement oxide mass, at least 5 or at least 10 mol%, preferably at least 20 mol%, particularly preferably at least 30 mol% and very particularly preferably at least 40 mol%. Usually is the ammonium content of the intimate dry mixture obtained in this way ≤ 150 mol% or ≤ 100 mol%, mostly ≤ 90 mol% or ≤ 80 mol%, often ≤ 70 mol% or ≤ 60 mol%.

The Temperature rate at which the intimate dry mixture reaches the decomposition temperature heated will be in the method according to the invention advantageously ≤ 8 ° C / min, preferably ≤ 5 ° C / min, especially preferably ≤ 3 ° C / min, whole particularly preferably ≤ 2 ° C / min or ≤ 1 ° C / min. In As a rule, however, this temperature rate becomes ≥ 0.1 ° C / min, usually ≥ 0.2 ° C / min and often ≥ 0.3 ° C / min or ≥ 0.4 ° C / min.

The The above also applies to the temperature rate at which the intimate dry mix from the decomposition area out - and is led into the calcination range from 380 to 480 ° C.

Preferred according to the invention the decomposition temperature range extends from 280 to 360 ° C and particularly preferably in the range from 300 to 350 ° C. or 310 up to 340 ° C.

Furthermore, the intimate dry mixture in the process according to the invention is advantageously kept in the decomposition temperature range until at least 95 mol%, better up to at least 97 mol% and even better up to at least 99 mol% or the Ge total amount of the total amount M ^A of ammonia released in the overall course of the thermal treatment of the intimate dry mixture.

Usually is in the inventive method the intimate dry mixture starting from room temperature (e.g. 20 ° C, or 25 ° C, or 30 ° C, or 35 ° C, or 40 ° C) heated to the decomposition temperature.

No later than then when the intimate dry mixture reaches the temperature of 230 ° C has in the inventive method the content of the (gas) atmosphere A, which is the thermal treatment of the intimate dry mix carried out in molecular oxygen to a value of ≤ 0.5 vol .-% be lowered.

Preferred according to the invention this decrease in the molecular oxygen content occurs a value of ≤ 0.3 Vol .-% and particularly preferably to a value of ≤ 0.1 vol .-%. It is particularly preferred in this phase of the method according to the invention the content of the atmosphere A disappearing in molecular oxygen. As a rule, this is However, the oxygen content is at values of ≥ 0.05% by volume.

Prefers lies the content of the atmosphere A in the method according to the invention even below the temperature of 230 ° C (e.g. already at temperatures ≥ 200 ° C) at ≤ 0.5% by volume, or ≤ 0.3 vol.%, or. ≤ 0.1 vol% or at 0 vol%. As a rule, however, this oxygen content even below 230 ° C (e.g. also at temperatures <200 ° C) at values of ≥ 0.05 Vol .-% lie.

Below the 230 ° C or 200 ° C can the gas atmosphere A, in which the thermal treatment takes place, but also clearly higher Have oxygen levels. In principle, this content of molecular Oxygen below 230 ° C or 200 ° C in the method according to the invention ≥ 5% by volume, or ≥ 10 Vol .-%, or 15 vol .-%, or ≥ 20 vol .-%, or ≥ 25 Vol .-%, or 30 vol .-%, or more. Also essentially one exclusively from Air or a thermal treatment atmosphere consisting of molecular oxygen is in possible in this temperature range.

According to the invention, the content of molecular oxygen in the atmosphere A of 0,5 0.5% by volume is maintained at least until at least 20 mol%, or 30 mol%, or 40 mol%, preferably up to at least 50 mol% , particularly preferably up to at least 60 mol%, or at least 70 mol%, or at least 80 mol% of the total amount M ^A of ammonia released in the overall course of the thermal treatment.

Experience has shown that the molecular oxygen content in atmosphere A will already be increased to a value> 0.5 vol.% To 4 vol.% Before 95 mol% of the total amount M ^A released in the overall course of the thermal treatment of ammonia have been released. This increase in the oxygen content preferably takes place before 90 mol%, preferably before 85 mol% and particularly preferably at the latest when 80 mol% of the total amount M ^A of ammonia released in the overall course of the thermal treatment has been released.

In other words, expediently according to the invention, the range of the method according to the invention in which the content of molecular oxygen in the atmosphere A is 0,5 0.5% by volume, to the extent that it is up to 20 or 30 or 40 to 80 mol% and preferably up to 50 to 70 mol% of the total amount M ^A of ammonia released in the total course of the thermal treatment have been released.

If the molecular oxygen in the atmosphere A is released at the latest when 98 mol% or 95 mol% of the total amount M ^A of ammonia released in the course of the thermal treatment has been released, to a value ≥ 0.5 vol. % to 4% by volume, this increase is preferably carried out to a ≥ 0.55% by volume to 4% by volume, and particularly preferably to a ≥ 0.6% by volume to 4% by volume amount value. The oxygen content is very particularly preferably increased to a value of 1 to 3% by volume or from 1 to 2% by volume. These increase values also apply to increases in all other released partial amounts of the total released total amounts of ammonia.

The Calcination temperature range extends in the method according to the invention advantageously to a temperature of the intimate dry mixture of 380 to 430 ° C and particularly preferably to such a temperature of 390 to 420 ° C.

The Decomposition temperature range is in the process according to the invention the temperature range after which the decomposition of the im thermal according to the invention ammonium ions to be treated containing an intimate dry mixture largely completed.

in the Calcination temperature range takes place in the method according to the invention the formation of the catalytically active multi-element oxide.

As a rule, the calcination in the calcination temperature range is preferred for at least 10 min wise last at least 20 min and particularly preferably at least 30 min. As a rule, the calcination in the calcination temperature range extends to ≤ 2 h, often ≤ 1.5 h or ≤ 1 h.

To When the calcination is complete, the material to be calcined is normally cooled. In this cooling usually takes place to room temperature (i.e., e.g. to 20 ° C, or to 25 ° C, or to 30 ° C, or to 35 ° C, or to 40 ° C).

Appropriately performed according to the invention cooling off of the calcined material to a value of ≤ 100 ° C Temperature within a period of ≤ 5 h, preferably ≤ 4 h, particularly preferably ≤ 3 h or ≤ 2 H. As a rule, however, this cooling period not less than 0.5 h.

With Cooling is an advantage of the calcination material in a surrounding (gas) atmosphere A, whose Molecular oxygen content ≤ 5% by volume, or ≤ 4 Vol .-%, or ≤ 3 Vol .-%, or ≤ 2 vol .-%, or ≤ 1 Vol .-%, or ≤ 0.5 Vol .-%, preferably ≤ 0.3 Vol .-% or ≤ 0.1 Vol .-% or 0 vol .-%, usually ≥ 0.05 vol .-%. This Oxygen content is then appropriate set if it is still in the calcination temperature range the calcination is started by lowering the temperature lead out of the calcination temperature range.

is the calcined material is cooled to a temperature of ≤ 350 ° C or ≤ 300 ° C or ≤ 250 ° C, further cooling can also in a (gas) atmosphere A take place, the molecular oxygen content of which is> 5% by volume or ≥ 10% by volume, or ≥ 15 vol .-%, or ≥ 20 vol .-%, or ≥ 25 Vol .-%, or ≥ 30 vol .-%, or more.

Also one essentially exclusively Air or molecular oxygen (gas) atmosphere A. when cooling further under this temperature possible.

In addition to the molecular oxygen contents described, the atmosphere A, in which the thermal treatment of the intimate dry mixture takes place, will essentially be composed of the constituent gases escaping from the intimate dry mixture and inert gas. The term “inert gases” is understood to mean all those gases which do not have a chemically reactive effect on the dry mass to be thermally treated according to the invention. Examples of inert gases are N ₂ or noble gases. Water vapor will be present in the atmosphere A in particular if the intimate dry mixture contains water of hydration As a rule, the water vapor content of the atmosphere A will never exceed 20% by volume during the thermal treatment according to the invention, and will generally even be ≤ 10% by volume at all times.

The Ammonia content of the (gas) atmosphere A is in the inventive method normally go through a maximum that is normally ≤ 10 vol .-%, often ≤ 8 vol .-% and mostly ≤ 7 Vol .-% is. Usually however, it becomes above 1% by volume, often above 2% by volume or 3% by volume.

Usually the ammonia content of atmosphere A will go through its maximum, before the intimate dry mix reaches the calcination temperature range has reached.

That in the calcination temperature range is the maximum ammonia content the atmosphere A usually with values ≤ 2 Vol .-%, respectively. ≤ 1 % By volume. However, it is usually at values> 0 vol.% lie.

Averaged over the total duration of the stay of the intimate dry mixture in the calcination temperature range (arithmetically), the NH ₃ content of the atmosphere A will generally be 1 1% by volume, preferably 0,5 0.5% by volume. Over the entire duration of the stay of the intimate dry mixture in the temperature range> 160 ° C, ≤ 360 ° C averaged (arithmetically), the NH ₃ content of atmosphere A is normally 1 or 1.5 or 2 to 8% by volume, usually 1 up to 4 vol .-%.

Usually is in the inventive method the (gas) atmosphere A no external ammonia added. That is, the only source of ammonia is usually the most intimate Dry mixture incorporated ammonium ions. However, it can in the method according to the invention be appropriate continuous (gas) atmosphere A and remove it to a certain extent in a circle (i.e. to thermally treated intimate dry mixture to be recycled).

According to the invention, the calcination is advantageously terminated before MoO ₃ can be detected in the X-ray diffractogram. However, MoO ₃ contents of up to 30% by weight or up to 20% by weight are tolerable in the multi-element oxide active materials obtainable according to the invention.

Next the elements Nb and / or W, as well as Mo, V and Cu can obtainable according to the invention Multi-element oxide active materials additionally e.g. the elements Ta, Cr, Ce, Ni, Co, Fe, Mn, Zn, Sb, Bi, Alkali (Li, Na, K, Rb, Cs), H, alkaline earth (Mg, Ca, Sr, Ba), Si, Al, Ti and Zr included. Naturally However, the multielement oxide active composition can also be used according to the invention consist only of the elements Nb and / or W as well as Mo, V and Cu.

As an active composition for catalysts for heterogeneously catalyzed partial gas phase oxidation of acrolein to acrylic acid (as well as from methacrolein to methacrylic acid and from propane to acrylic acid; the process products according to the invention are likewise suitable for these heterogeneously catalyzed gas phase partial oxidations), particularly suitable catalytically active multielement oxide compositions obtainable according to the invention satisfy the general stoichiometry I below Mo ₁₂ V _a X ¹ _b X ² _c X ³ _d X ⁴ _e X ⁵ _f X ⁶ _g O _n (I), in which the variables have the following meaning:
X ¹ = W, Nb, Ta, Cr and / or Ce,
X ² = Cu, Ni, Co, Fe, Mn and / or Zn,
X ³ = Sb and / or Bi,
X ⁴ = one or more alkali metals (Li, Na, K, Rb, Cs) and / or H,
X ⁵ = one or more alkaline earth metals (Mg, Ca, Sr, Ba),
X ⁶ = Si, Al, Ti and / or Zr,
a = 1 to 6,
b = 0.2 to 4,
c = 0.5 to 18,
d = 0 to 40,
e = 0 to 2,
f = 0 to 4,
g = 0 to 40 and
n = a number determined by the valency and frequency of the elements in I other than oxygen, and
the variables within the specified ranges are to be selected with the proviso that the molar proportion of the element Mo in the total amount of all elements of the multi-element oxide mass (I) other than oxygen is 20 mol% to 80 mol%, the molar ratio of in Mo containing catalytically active multielement oxide composition (I) to V, Mo / V contained in the catalytically active multielement oxide composition (I) is 15: 1 to 1: 1, the corresponding molar ratio Mo / Cu 30: 1 to 1: 3 and the corresponding molar ratio Mo / (total amount of W and Nb) is 80: 1 to 1: 4.

Preferred active multielement oxide materials (I) are those in which the variables are in the following ranges:
X ¹ = W, Nb and / or Cr,
X ² = Cu, Ni, Co and / or Fe,
X ³ = Sb,
X ⁴ = Na and / or K,
X ⁵ = Ca, Sr and / or Ba,
X ⁶ = Si, Al and / or Ti,
a = 2.5 to 5,
b = 0.5 to 2,
c = 0.5 to 3,
d = 0 to 2,
e = 0 to 0.2,
f = 0 to 1,
g = 0 to 15 and
n = a number which is determined by the valency and frequency of the elements in I other than oxygen.

However, the following multielement oxide active materials II are very particularly preferred process products of the process according to the invention: Mo ₁₂ V _a X ¹ _b X ² _c X ⁵ _f X ⁶ _g O _n (II), in which the variables have the following meaning:
X ¹ = W and / or Nb,
X ² = Cu and / or Ni,
X ⁵ = Co and / or Sr,
X ⁶ = Si and / or Al,
a = 3 to 4.5,
b = 1 to 1.5,
c = 0.75 to 2.5,
f = 0 to 0.5,
g = 0 to 8 and
n = a number determined by the valency and frequency of the elements other than oxygen in II, and
the variables within the specified ranges are to be selected with the proviso that the molar proportion of the element Mo in the total amount of all elements of the multielement oxide active composition (II) other than oxygen is 20 mol% to 80 mol%, the molar ratio of in Mo containing catalytically active multielement oxide composition (II) to V, Mo / V, contained in the catalytically active multielement oxide composition (II) is 15: 1 to 1: 1, the corresponding molar ratio Mo / Cu 30: 1 to 1: 3 and the corresponding molar ratio Mo / (total amount of W and Nb) is 80: 1 to 1: 4.

To produce such direct process products according to the invention, the process according to the invention is based on sources (starting compounds) of the constituents other than oxygen which are suitable in a manner known per se, of the desired multielement oxide active composition in the respective stoichiometric ratio desired in the multielement oxide active composition, and generate the most intimate, possible preferably a finely divided, dry mixture which is then subjected to the thermal treatment according to the invention, it being possible for the thermal treatment to take place before or after the shaping to give shaped catalyst bodies of a particular geometry. According to the invention, it advantageously takes place before that. The sources can either already be oxides or those compounds which can be converted into oxides by heating, at least in the presence of oxygen. In addition to the oxides, the main starting compounds are halides, nitrates, formates, oxalates, acetates and car bonate or hydroxides into consideration.

suitable The starting compounds of Mo, V, W and Nb are also their oxo compounds (Molybdate, Vanadate, Wolframate and Niobate) or those of these derived acids. Sources containing oxygen are favorable for the process according to the invention.

The content of ammonium ions in the intimate dry mixture according to the invention can be achieved in a simple manner by incorporating a corresponding amount of ammonium ions into the intimate dry mixture. The ammonium ions can expediently be introduced into the intimate dry mixture, for example, by using the corresponding ammonium oxometalates as sources of the elements Mo, V, W or Nb. Examples include ammonium metaniobate, ammonium metavanadate, ammonium heptamolybdate tetrahydrate and ammonium paratungstate heptahydrate. Of course, ammonium suppliers such as NH ₄ NO ₃ , or NH ₄ Cl, or ammonium acetate, or ammonium carbonate, or ammonium hydrogen carbonate, or NH ₄ OH, or NH ₄ CHO, can also be added to the intimate dry mixture to be thermally treated, regardless of the starting compounds required as sources of the multielement oxide active composition ₂ , or ammonium oxalate can be incorporated.

The intimate mixing of the starting compounds can in principle be carried out in a dry state or done in wet form. If it is done in dry form, the Starting compounds expediently used as fine powder and after mixing e.g. more desired to shaped catalyst bodies Compressed geometry (e.g. tableted), which is then the thermal according to the invention Treatment.

Preferably however, the intimate mixing takes place in wet form. Usually the starting compounds are in the form of an aqueous solution and / or Suspension mixed together. Particularly intimate dry mixes are obtained in the described mixing process if only from in dissolved Form from existing sources and starting compounds is assumed. As a solvent water is preferred. Then the aqueous mass (Solution or suspension) and the intimate dry mixture thus obtained optionally thermally treated directly according to the invention. Preferably the drying process is carried out by spray drying (the outlet temperatures are usually 100 to 150 ° C) and immediately after completion of the aqueous Solution or Suspension. The resulting powder can be pressed directly be shaped. Often turns out however it is for immediate processing as too fine, which is why then adding e.g. Water is appropriately kneaded. frequently When kneading, an addition of a lower organic carboxylic acid (e.g. Acetic acid) as advantageous (typical additional amounts are 5 to 10% by weight based on powder mass used).

The modeling clay is then either the desired Shaped catalyst geometry, dried and then the thermal according to the invention Subjected to treatment (leads to so-called full catalysts) or unformed calcined and then ground to a powder (usually <80 μm, preferably <50 μm, especially preferably <30 μm in which Rule ≥ 1 μm) which usually with the addition of a small amount of water and optionally more common Binder is applied as a moist mass to inert carrier bodies. To When the coating is finished, it is dried again and thus an operational shell catalyst receive. The intimate mixing of the starting compounds takes place in the form of e.g. aqueous Solution, so can with the same also inert porous Carrier body soaked, dried and subsequently to supported catalysts thermal according to the invention be treated. Can be used in the production of coated catalysts coating the carrier body too beforehand the thermal according to the invention Treatment, i.e. e.g. with the moistened spray powder.

For shell catalysts suitable carrier materials are e.g. porous or non-porous Aluminum oxides, silicon dioxide, thorium dioxide, zirconium dioxide, silicon carbide or silicates such as magnesium or aluminum silicate (e.g. steatite of the type C 220 from CeramTec).

The Carrier bodies can be shaped regularly or irregularly be, being regularly shaped Carrier body with clearly developed surface roughness, e.g. Balls or hollow cylinders with a split layer are preferred.

It is suitable to use essentially non-porous, rough-surface, spherical supports made of steatite (for example steatite of the type C 220 from CeramTec), the diameter of which is 1 to 8 mm, preferably 4 to 5 mm. However, it is also suitable to use cylinders as carrier bodies, the length of which is 2 to 10 mm and the outside diameter is 4 to 10 mm. In the case of rings as support bodies, the wall thickness is also usually 1 to 4 mm. Annular support bodies to be used preferably have a length of 2 to 6 mm, an outer diameter of 4 to 8 mm and a wall thickness of 1 to 2 mm. Rings of geometry 7 mm × 3 are also particularly suitable mm × 4 mm (outer diameter × length × inner diameter) as carrier body.

The coating of the carrier body with finely divided multielement oxide active composition obtainable according to the invention or their finely divided flow mass (intimate dry mixture) to be thermally treated according to the invention is generally carried out in a rotatable container, as is known, for example, from DE-A 2909671 , the EP-A 293859 or from the EP-A 714700 is known. The procedure of EP-A 714700 is preferred.

Conveniently, is used to coat the carrier body the powder mass to be applied moistens the carrier body. After applying is usually by means of hot Air dried. The layer thickness of the powder mass applied to the carrier will be convenient in the range 10 to 1000 μm, preferably in the range from 50 to 500 μm and particularly preferably in the range from 150 to 250 μm.

in the In the case of full catalysts, the shaping can, as already mentioned, also before or after performing the thermal according to the invention Treatment.

For example can from the powder form of the multielement oxide active composition obtainable according to the invention or their not yet thermally treated precursor mass (the intimate dry mixture) by compression to the desired one Catalyst geometry (e.g. by tableting, extruding or Extrusion) full catalysts are prepared, where appropriate Tools such as Graphite or stearic acid as a lubricant and / or molding aid and reinforcing agents such as microfibers made of glass, asbestos, silicon carbide or potassium titanate can be added. Suitable unsupported catalyst geometries are e.g. Solid cylinder or Hollow cylinder with an outer diameter and a length of 2 to 10 mm. In the case of the hollow cylinder, the wall thickness is 1 to 3 mm appropriate. Of course you can the full catalyst also have spherical geometry, the spherical diameter Can be 2 to 10 mm.

Of course they can obtainable according to the invention Multielement oxide active materials also in powder form, i.e. not too particular Catalyst geometries shaped as catalysts for the heterogeneous catalyzed partial oxidation of acrolein to acrylic acid, or Methacrolein to methacrylic acid or Propane to acrylic acid be used (e.g. also in a fluidized bed).

However, the process according to the invention is also suitable for producing multielement oxide active materials of the general formula III, [A] _p [B] _q [C] _r (III), in which the variables have the following meaning:
A = Mo ₁₂ V _a X ¹ _b X ² _c X ³ _d X ⁴ _e X ⁵ _f X ⁶ _g O _x ,
B = X ₁ ⁷ Cu _h H _i O _y,
C = X ₁ ⁸ Sb _j H _k O _z ,
X ¹ = W, Nb, Ta, Cr and / or Ce, preferably W, Nb and / or Cr,
X ² = Cu, Ni, Co, Fe, Mn and / or Zn, preferably Cu, Ni, Co and / or Fe,
X ³ = Sb and / or Bi, preferably Sb,
X ⁴ = Li, Na, K, Rb, Cs and / or H. preferably Na and / or K,
X ⁵ = Mg, Ca, Sr and / or Ba, preferably Ca, Sr and / or Ba,
X ⁶ = Si, Al, Ti and / or Zr, preferably Si, Al and / or Ti,
X ⁷ = Mo, W, V, Nb and / or Ta, preferably Mo and / or W,
X ⁸ = Cu, Ni, Zn, Co, Fe, Cd, Mn, Mg, Ca, Sr and / or Ba, preferably Cu and / or Zn, particularly preferably Cu,
a = 1 to 8, preferably 2 to 6,
b = 0.2 to 5, preferably 0.5 to 2.5
c = 0 to 23, preferably 0 to 4,
d = 0 to 50, preferably 0 to 3,
e = 0 to 2, preferably 0 to 0.3,
f = 0 to 5, preferably 0 to 2,
g = 0 to 50, preferably 0 to 20,
h = 0.3 to 2.5, preferably 0.5 to 2, particularly preferably 0.75 to 1.5,
i = 0 to 2, preferably 0 to 1,
j = 0.1 to 50, preferably 0.2 to 20, particularly preferably 0.2 to 5,
k = 0 to 50, preferably 0 to 20, particularly preferably 0 to 12,
x, y, z = numbers which are determined by the valency and frequency of the elements in A, B, C other than oxygen,
p, q = positive numbers
r = 0 or a positive number, preferably a positive number,
where the ratio p / (q + r) = 20: 1 to 1:20, preferably 5: 1 to 1:14 and particularly preferably 2: 1 to 1: 8 and, in the event that r is a positive number, the ratio q / r = 20: 1 to 1:20, preferably 4: 1 to 1: 4, particularly preferably 2: 1 to 1: 2 and very particularly preferably 1: 1,
which the portion [A] p in the form of three-dimensionally extended areas (phases) A of the chemical composition
A: Mo ₁₂ VaX ¹ _b X ² _c X ³ _d X ⁴ _e X ⁵ _f X ⁶ _g O _x ,
the proportion [B] _q in the form of three-dimensionally extended areas (phases) B of the chemical composition
B: X ₁ ⁷ Cu _h H _i O _y and
the proportion [C] _r in the form of three-dimensionally extended areas (phases) C of the chemical composition
C: X ₁ ⁸ Sb _j H _k O _z
included, the areas A, B and optionally C being distributed relative to one another as in a mixture of finely divided A, finely divided B and optionally finely divided C, and
where all variables within the specified ranges are to be selected with the proviso that the molar proportion of the element Mo in the total amount of all elements of the multielement oxide active composition (III) other than oxygen is 20 mol% to 80 mol%, the molar ratio of that in of the catalytically active multielement oxide composition (III) Mo to V, Mo / V contained in the catalytically active multielemetoxide composition (III) is 15: 1 to 1: 1, the corresponding molar ratio Mo / Cu 30: 1 to 1: 3 and the corresponding molar ratio Mo / (total amount of W and Nb) is 80: 1 to 1: 4.

Preferred multielement oxide active materials III are those whose areas A have a composition in the subsequent stoichiometric grid of the general formula IV Mo ₁₂ V _a X ¹ _b X ² _c X ⁵ _f X ⁶ _g O _x (IV), With
X ¹ = W and / or Nb,
X ² = Cu and / or Ni,
X ⁵ = Ca and / or Sr,
X ⁶ = Si and / or Al,
a = 2 to 6,
b = 1 to 2,
c = 1 to 3,
f = 0 to 0.75,
g = 0 to 10, and
x = a number which is determined by the valency and frequency of the elements other than oxygen in (IV).

The used in connection with the multielement oxide active materials III The term "phase" means three-dimensional extensive areas whose chemical composition is different from theirs Environment is different. The phases are not necessarily radiographically homogeneous. As a rule, phase A forms a continuous phase, in which particles of phase B and optionally C are dispersed.

The finely divided phases B and optionally C exist with advantage from particles whose size diameter, i.e. the longest connecting path of two passing through the center of gravity of the particles on the surface the particle located points up to 300 microns, preferably 0.1 to 200 microns, particularly preferably 0.5 to 50 μm and very particularly preferably 1 to 30 μm. But are also suitable Particles with a size diameter of 10 to 80 μm or 75 to 125 µm.

in principle can phases A, B and optionally C in the multielement oxidative compositions obtainable according to the invention III are amorphous and / or crystalline.

It is favorable if phase B consists of crystallites of oxometalates or contains those oxometalate crystallites (= oxide crystallites) which have the X-ray diffraction pattern and thus the crystal structure type of at least one of the following copper molybdates. The location of the associated X-ray diffraction fingerprint is given in brackets.
Cu ₄ Mo ₆ O ₂₀ [A. Moini et al., Inorg. Chem. 25 (21) (1986) 3782-3785],
Cu ₄ Mo ₅ O ₁₇ [index card 39-181 of the JCPDS-ICDD index (1991)],
α-CuMoO ₄ [index card 22-242 of the JCPDS-ICDD index (1991)],
Cu ₆ Mo ₅ O ₁₈ [index card 40-865 of the JCPDS-ICDD index (1991)],
Cu _4-x Mo ₃ O ₁₂ with X = 0 to 0.25 [index cards 24-56 and 26-547 of the JCPDS-ICDD index (1991)],
Cu ₆ Mo ₄ O ₁₅ [index card 35-17 of the JCPDS-ICDD index (1991)],
Cu ₃ (MoO ₄ ) ₂ (OH) ₂ [index card 36-405 of the JCPDS-ICDD index (1991)],
Cu ₃ Mo ₂ O ₉ [index cards 24-55 and 34-637 of the JCPDS-ICDD index (1991)],
Cu ₂ MoO ₅ [index card 22-607 of the JCPDS-ICDD index (1991)].

Phase B preferably contains oxometalates, which have the X-ray diffraction pattern and thus the crystal structure type of the subsequent copper molybdate:
CuMoO ₄ -III with a tungsten structure according to Russian Journal of Inorganic Chemistry 36 (7) (1991) 927-928, Table 1.

Among these are those with the following stoichiometry V Cu ₁ Mo _A W _B V _C Nb _D Ta _E O _y · (H ₂ O) _F (V), With
1 / (A + B + C + D + E): 0.7 to 1.3, preferably 0.85 to 1.15, particularly preferably 0.95 to 1.05 and very particularly preferably 1,
F: 0 to 1,
B + C + D + E: 0 to 1, preferably 0 to 0.7, and
Y is a number which is determined by the valency and frequency of the elements other than oxygen,
prefers.

Among these, those of stoichiometries VI, VII or VIII are particularly preferred: Cu ₁ Mo _A W _B V _C O _y (VI), With
1 / (A + B + C): 0.7 to 1.3, preferably 0.85 to 1.15, particularly preferably 0.95 to 1.05 and very particularly preferably 1,
B + C: 0 to 1, preferably 0 to 0.7, and
y is a number determined by the valency and frequency of elements other than oxygen; Cu ₁ Mo _A W _B O _y (VI), With
1 / (A + B): 0.7 to 1.3, preferably 0.85 to 1.15, particularly preferably 0.95 to 1.05 and very particularly preferably 1,
A, B: 0 to 1 and
y is a number determined by the valency and frequency of elements other than oxygen; Cu ₁ Mo _A W _B O _y (VIII), With
1 / (A + C): 0.7 to 1.3, preferably 0.85 to 1.15, particularly preferably 0.95 to 1.05 and very particularly preferably 1,
A, C: 0 to 1 and
y is a number determined by the valency and frequency of elements other than oxygen.

The production of such oxometalates, for example, discloses EP-A 668 104 ,

Suitable phases B are also those which contain oxometalates of the stoichiometry IX below Cu ₁ Mo _A W _B V _C Nb _D Ta _E O _y (IX), With
1 / (A + B + C + D + E): 0.7 to 1.3, preferably 0.85 to 1.15, particularly preferably 0.95 to 1.05 and very particularly preferably 1,
(B + C + D + E) / A: 0.01 to 1, preferably 0.05 to 0.3, particularly preferably 0.075 to 0.15 and very particularly preferably 0.11 and
y is a number that is determined by the valency and frequency of the elements other than oxygen,
and the structure type referred to as HT-copper molybdate structure, which is characterized by an X-ray diffraction pattern (fingerprint), the most characteristic and most intense diffraction lines, given as interplanar spacings d [Å], are as follows:
6.79 ± 0.3
3.56 ± 0.3
3.54 ± 0.3
3.40 ± 0.3
3.04 ± 0.3
2.96 ± 0.3
2.67 ± 0.2
2.66 ± 0.2
2.56 ± 0.2
2.36 ± 0.2
2.35 ± 0.2
2.27 ± 0.2
2.00 ± 0.2
1.87 ± 0.2
1.70 ± 0.2
1.64 ± 0.2
1.59 ± 0.2
1.57 ± 0.2
1.57 ± 0.2
1.55 ± 0.2
1.51 ± 0.2
1.44 ± 0.2.

In the case, that phase B contains a mixture of different oxometalates a mixture of oxometalates with a tungsten and HT copper molybdate structure prefers. The weight ratio from crystallites with HT copper molybdate structure to crystallites with a tungsten structure can be 0.01 to 100, 0.1 to 10, 0.25 to 4 and 0.5 to 2.

The production of oxometalates IX, for example, discloses the DE-A 195 28 646 ,

Phase C preferably consists of crystallites which have the trirutile structure type of the α- and / or β-copper antimonate CuSb ₂ O ₆ . α-CuSb ₂ O ₆ crystallizes in a tetragonal trirutile structure (E.-O. Giere et al., J. Solid State Chem. 131 (1997) 263-274), while β-CuSb ₂ O _{6 is} a monoclinically distorted trirutil Structure (A. Nakua et al., J. Solid State Chem. 91 (1991) 105-112 or comparative diffractogram in index card 17-284 in the 1989 JCPDS-ICDD index). In addition, phases C are preferred, which have the pyrochlore structure of the mineral Parzite, a copper-antimony oxide hydroxide with the variable composition Cu _y Sb _2-x (O, OH, H ₂ O) _6-7 (y ≤ 2 , 0 ≤ x ≤ 1) (B. Mason et al., Mineral. Mag. 30 (1953) 100-112 or comparison diagram in index card 7-303 of the JCPDS-ICDD index 1996).

In addition, phase C can consist of crystallites which structure the copper antimonate Cu ₉ Sb ₄ O ₁₉ (S. Shimada et al., Chem. Lett. 1983, 1875-1876 or S. Shimada et. Al., Thermochim. Acta 133 (1988) 73-77 or comparison diagram in index card 45-54 of the JCPDS-ICDD index) and / or the structure of Cu ₄ SbO _4.5 (S. Shimada et al., Thermochim. Acta 56 (1982) 73- 82 or S. Shimada et al., Thermochim. Acta 133 (1988) 73-77 or comparison diagram in index card 36-1106 of the JCPDS-ICDD index).

Of course they can Areas C also consist of crystallites that form a mixture of the represent the aforementioned structures.

The intimate dry mixtures on which the multielement oxide active compositions of the general formula III are based and which are to be thermally treated according to the invention can be obtained, for example, as described in the documents WO 02/24327, DE-A 4405514 . DE-A 4440891 . DE-A 19528646 . DE-A 19740493 . EP-A 756894 . DE-A 19815280 . DE-A 19815278 . EP-A 774297 . DE-A 19815281 . EP-A 668104 and DE-A 19736105 is described. According to the invention, only the incorporation of ammonium ions has to be taken into account.

that is, all exemplary embodiments in the abovementioned documents produced intimate dry mixtures can be thermally according to the invention be treated and lead to immediate process products that are excellent for catalysts for the heterogeneously catalyzed partial gas phase oxidation of acrolein suitable for acrylic acid are.

The basic principle of the preparation of intimate dry mixtures which, when treated according to the invention, leads to advantageous multielement oxidative compositions of the general formula III is to use at least one multielement oxide composition B (X ₁ ⁷ Cu _h H _i O _y ) as the starting composition 1 and optionally one or more multielement oxide compositions C ( X ₁ ⁸ Sb _j H _k O _z ) as a starting mass 2 either separately from one another or associated with one another in finely divided form and then the starting masses 1 and optionally 2 with a mixture that swells the elementary constituents of the multielement oxide mass A Mo ₁₂ V _a X _b ¹ X _c ² X _d ³ X _e ⁴ X _f ⁵ X _g ⁶ O _x (A),

Contains in a composition corresponding to stoichiometry A, bringing it into intimate contact in the desired ratio (according to general formula III) and, if necessary, drying the resulting intimate mixture. It is only essential according to the invention that either the sources of the elementary constituents of the multi-element oxide mass A contain ammonium ions and / or when they come into intimate contact, completely decomposable salts containing ammonium ions, such as NH ₄ NO ₃ , NH ₄ Cl, ammonium acetate, etc. are added.

The intimate contact of the constituents of the starting materials 1 and optionally 2 with the mixture containing the sources of the elemental constituents of the multimetal oxide composition A (starting material 3) can be carried out either dry or wet. In the latter case, it is only necessary to ensure that the pre-formed phases (crystallites) B and possibly C do not go into solution. The latter is guaranteed in aqueous medium at pH values that do not deviate too much from 7 and that are usually guaranteed at not too high temperatures. If the intimate contact takes place wet, the final drying step is normally normally to the intimate dry mixture to be thermally treated according to the invention (for example by spray drying). Such a dry mass is automatically obtained during dry mixing. Of course, the finely divided phases B and optionally C can also be incorporated into a plastically deformable mixture which contains the sources of the elementary constituents of the multimetal oxide composition A, as is the case with DE-A 10046928 recommends. Of course, the intimate contact of the constituents of the starting materials 1 and, if appropriate, 2 with the sources of the multielement oxide material A (starting material 3) can also take place in the way that DE-A 19815281 describes.

Appropriately according to the invention, one can also proceed by intimately mixing the sources of multielement oxide mass A (for example dissolving and / or suspending in an aqueous medium and then spray-drying the aqueous mixture) and mixing the resulting finely divided starting mass 3 with the finely divided starting mass 1 and optionally 2 and kneaded together with the addition of water and, if appropriate, other plasticizers. Mixing can take place in a special mixing device outside the kneader or in the kneader itself (changing the direction of rotation). The latter is advantageous. The plasticine is then extruded and the extruded strands are dried. The extruded strands can subsequently be thermally treated according to the invention as described. The resulting calcination material is then normally ground and as in the EP-A 714700 described used for the production of coated catalyst.

As In principle, all sources of the multielement oxide mass A come into consideration, which are also sources for the multielement oxide masses I are suitable.

As Plasticizers are essentially all solvents suitable, which evaporate largely residue-free at temperatures up to about 360 ° C or become largely residue-free decompose.

The plasticizer is expediently chosen such that it wets the finely divided dry mixture from starting materials 1, 3 and, if appropriate, 2 well. In addition to water, suitable plasticizers are carboxylic acids which are branched or straight-chain, saturated or unsaturated can be, for example formic acid and acetic acid, primary or secondary C ₁ to C ₈ alcohols, such as methanol, ethanol, 2-propanol, but also aldehydes or ketones such as acetone and mixtures thereof.

As Kneaders can e.g. continuous screw kneaders or trough kneaders can be used. Continuous screw kneaders have one or more axially parallel, in a cylindrical housing arranged snails on the shaft kneading and transport elements have the material fed to one end of the kneader convey to the outlet end of the kneader and plasticize at the same time and homogenize. Trough kneaders with at least two horizontally mounted rotors, e.g. a so-called double-shovel Trough kneader with two opposite directions rotating kneading blades in a double bowl. The rotors can different shapes such as sigma, masticator, hub shape etc. exhibit. The kneaders can work batchwise or continuously. Alternatively you can high-speed intensive mixers such as ploughshare mixers or tilt mixers or use a comparatively slow running Simpson mixer, which may be equipped with high-speed knife elements.

It is cheap if kneading at temperatures less than 90 ° C, preferably less than 80 ° C and particularly preferably less than 60 ° C. Usually will the temperature during kneading is more than 0 ° C and usually 20 to 45 ° C.

Farther is it convenient if the kneading is less than 10 hours, preferably less than 3 hours and particularly preferably less than 1 hour takes. As a rule, kneading takes more than 15 minutes to take.

The plasticity obtained after kneading ("plastic" or "pasty" denotes a consistency which is coherent and not like a powder consists of discrete particles and only is deformable under the action of a certain force and not, like a solution or suspension, willingly takes the form of a vessel) Mass can immediately form moldings arbitrary geometry shaped and these moldings according to the invention thermally after drying are treated, which immediately obtain full catalysts can be. For this is the use of an extruder (alternatively an Alexanderwerk or an extrusion press can be used). Frequently the extrudate is a strand shape with a diameter of e.g. 1 to 20 mm, often 3 to 10 mm, on one length from e.g. Have 0.5 to 20 cm. The strands can then, as already described, dried, thermally treated, ground and the regrind to shell catalysts are processed. Drying is usually at 50 to 180 ° C, mostly at about 120 to 130 ° C (appropriately in the air flow) become.

As a general rule the finely divided starting materials 1, 2 are advantageous according to the invention from particles whose size diameter d (longest connecting path of two passing through the center of gravity of the particles on the surface the points of the particles)> 0 up to 300 μm, preferably 0.01 to 100 μm and is particularly preferably 0.05 to 20 μm. Of course they can Particle diameter d can also be 0.01 to 150 μm or 0.5 to 50 μm.

It is possible that the starting materials 1, 2 to be used according to the invention have a specific surface O (determined according to DIN 66131 by gas adsorption (N ₂ ) according to Brunner-Emmert-Teller (BET)), which is ≤ 80 m ² / g, frequently ≤ 50 m ² / g or ≤ 10 m ² / g and sometimes ≤ 1 m ² / g. As a rule, O> 0.1 m ² / g.

in principle can the starting materials 1, 2 according to the invention are both amorphous and / or crystalline be used.

It is favorable if the starting materials 1, 2 consist of crystallites of oxometalates B (for example those of the general formulas V to IX) and crystallates of oxometalates C, as described above. As already mentioned, such oxometalates B are, for example, according to the procedures of EP-A 668 104 or the DE-A 19 528 646 available. But also the manufacturing processes of DE-A 44 05 514 and the DE-A 44 40 891 are applicable.

In principle, multi-element oxide masses B containing oxometalates B or consisting of oxometalates B can be produced in a simple manner by generating an intimate, preferably finely divided, dry mixture of suitable elementary constituents according to their stoichiometry and this at temperatures (material material temperatures) of 200 up to 1000 ° C, preferably 250 to 900 ° C or 700 to 850 ° C for several hours under inert gas, for example nitrogen, a mixture of inert gas and oxygen or, preferably, in air, the calcination time being from a few minutes to a few hours. The calcination atmosphere can additionally contain water vapor. Calcination under pure oxygen is also possible. Suitable sources for the elemental constituents of the multimetal oxide mass B are those compounds which are already oxides and / or those compounds which can be converted into oxides by heating, at least in the presence of oxygen. Next the oxides are, in particular, halides, nitrates, formates, oxalates, citrates, acetates, carbonates, amine complex salts, ammonium salts and / or hydroxides (compounds such as NH ₄ OH, (NH ₄ ) ₂ CO ₃ , NH ₄ NO ₃ , NH ₄ CHO ₂ , CH ₃ COOH, NH ₄ CH ₃ CO ₂ or ammonium oxalate, which can decompose and / or decompose into gaseous compounds at the latest during later calcination, can also be incorporated).

The intimate mixing of the starting compounds for the production of multielement oxide masses B can be done in dry or wet form. Is it done in dry form, the starting compounds are expedient used as a fine powder and after mixing and optionally Compacting subjected to calcination. This is preferably done intimate mixing, however, in wet form. Usually the Starting compounds in the form of an aqueous solution and / or suspension with one another mixed. Particularly intimate dry mixtures are described in the Dry process obtained when only in dissolved form existing sources of elementary constituents are assumed. As a solvent water is preferred. Then the aqueous mass obtained dried, the drying process preferably by spray drying the aqueous mixture with outlet temperatures of 100 to 150 ° C. Then will the dried mass is calcined as described above.

A preferred way of producing oxometalates B (X ⁷ ₁ Cu _h H _j O _y with X = Mo u./o. W) is to mix an aqueous solution of ammonium heptamolybolate and ammonium paratungstate with an aqueous ammoniacal solution of copper carbonate (e.g. the composition Cu ( OH) ₂ CO ₃ ) or copper acetate and / or copper formate, drying the resulting mixture, for example spray drying, and calcining the resulting dry mixture, if appropriate after subsequent kneading and extrusion and drying, as described.

In another manufacturing variant of the multielement oxide masses B. the thermal treatment of the mixture of the starting compounds used in a pressure vessel (autoclave) in the presence of super-atmospheric Pressurized water vapor at temperatures in the range of> 100 to 600 ° C. The print area typically extends up to 500 atm, preferably up to 250 atm. This is particularly advantageous when hydrothermal Treatment in the temperature range from> 100 to 374.15 ° C (critical temperature of the Water), in which water vapor and liquid water are among themselves setting presses coexist.

The available multi-element oxide materials as described above B, the oxometalates B of a single structure type or a mixture of oxometalates B of different structure types can contain, or exclusively from oxometalates B of a single structure type or from one Mixture of oxometalates of different structure types exist, can well, if necessary after grinding and / or classification to desired sizes, as Starting mass required according to the invention 1 can be used.

In principle, the multimetal oxide compositions C can be produced in the same way as the multimetal oxide compositions 3. In the case of the multimetal oxide composition C, the intimate dry mixture is advantageously calcined at temperatures (material temperature) of 250 to 1200 ° C, preferably 250 to 850 ° C. The calcination can be carried out under inert gas, for example nitrogen, but also under a mixture of inert gas and oxygen, for example air, or else under pure oxygen. Calcination under a reducing atmosphere is also possible. As such reducing gases, hydrocarbons such as methane, aldehydes such as acrolein or ammonia can be used. However, the calcination can also take place under a mixture of O ₂ and reducing gases, as is the case, for example, in DE-A 4335973 is described. When calcining under reducing conditions, however, it should be noted that the metallic constituents are not reduced to the element. Usually the takes to be reduced to the element. As a rule, the required calcination time (usually a few hours) also decreases with increasing calcination temperature.

According to the invention, preference is given to using multielement oxide materials C which are obtainable by preparing a dry mixture from sources of the elementary constituents of the multielement oxide composition C, which contain at least part, preferably the total amount, of the antimony in the oxidation state +5, and this at temperatures (material material temperatures ) from 200 to 1200 ° C, preferably from 200 to 850 ° C and particularly preferably from 300 to 600 ° C calcined. Such multimetal oxide materials C are z. B. according to the in the DE-A 24 07 677 manufacturing methods described in detail. Among these, the procedure is preferred in which antimony trioxide or Sb ₂ O ₄ in an aqueous medium by means of hydrogen peroxide in an amount which is below or equal to or exceeds the stoichiometric, at temperatures between 40 and 100 ° C. to form antimony (V. ) Oxidized hydroxide oxidized before this oxidation, during this oxidation and / or after this oxidation aqueous solutions and / or suspensions of suitable starting compounds of the remaining elemental constituents of the multimetal oxide mass C, then the resulting aqueous mixture dries (preferably spray-dried, inlet temperature: 200 to 300 ° C, outlet temperature: 80 to 130 ° C, often 105 to 115 ° C ) and then calcined the intimate dry mixture as described.

In the process as just described, for example, aqueous hydrogen peroxide solutions with an H ₂ O ₂ content of 5 to 33% by weight can be used. Subsequent addition of suitable starting compounds of the other elementary constituents of oxometalate C is particularly recommended if they are able to catalytically decompose the hydrogen peroxide. Of course, it would also be possible to isolate the antimony (V) oxide hydroxide from the aqueous medium and, for example, to mix it intimately with suitable finely divided starting compounds of the other elemental constituents of oxometalate C and, if appropriate, further Sb starting compounds, and then calcining this intimate mixture as described.

It is essential that the element sources of oxometalates C are either already oxides, or compounds that can be converted into oxides by heating, if appropriate in the presence of oxygen. In addition to the oxides, halides, nitrates, formates, oxalates, acetates, carbonates and / or hydroxides are therefore particularly suitable as starting compounds (compounds such as NH ₄ OH, (NH ₄ ) ₂ CO ₃ , NH ₄ NO ₃ , NH ₄ CHO ₂ , CH ₃ COOH, NH ₄ CH ₃ CO ₂ or Amtnonium oxalate, which can decompose and / or decompose into gaseous compounds at the latest during the later calcination, can also be incorporated).

In general, the intimate mixing of the starting compounds can also be carried out in dry or wet form for the preparation of oxometalates C. If it is in dry form, the starting compounds are expediently used as finely divided powders. However, the intimate mixing is preferably carried out in wet form. The starting compounds are usually mixed together in the form of an aqueous solution and / or suspension. After the mixing process is complete, the fluid mass is dried and, after drying, calcined. Here, too, drying is preferably carried out by spray drying. After the calcination has taken place, the oxometalates C can be comminuted again (for example by wet or dry milling, for example in a ball mill or by jet milling) and the powder, which generally consists of essentially spherical particles, has the particle size class with a powder available for the invention Multielementoxid (III) desired particle size range lying grain size diameter by separating in a conventional manner to be carried out (eg wet or dry screening). A preferred way of producing oxometalates C of the general formula (Cu, Zn) ₁ Sb _h H _i O _y consists in antimony trioxide and / or Sb ₂ O ₄ in an aqueous medium using hydrogen peroxide first in a, preferably finely divided, Sb (V) compound , for example Sb (V) oxide hydroxide hydrate, the resulting aqueous suspension with an ammoniacal aqueous solution of Zn and / or Cu carbonate (which may have the composition Cu ₂ (OH) ₂ CO ₃ ) or Zn- and / or Cu acetate and / or formate to dry the resulting aqueous mixture, e.g. B. spray drying as described, and the powder obtained, optionally after subsequent kneading with water and subsequent extrusion and drying, as described. Under favorable circumstances, the oxometalates B and the oxometalates C can be produced in a socialized form. In these cases, a mixture of crystals of oxometalates B and crystallites of oxometalates C is obtained, which can be used directly as starting material 1 + 2.

To produce an aqueous solution required as starting material 3, starting from the sources of the elemental constituents already mentioned, the use of elevated temperatures is generally required. Usually temperatures ≥ 60 ° C, mostly ≥ 70 C, but normally ≤ 100 ° C are used. The latter and the following applies in particular if the ammonium heptamolybdate tetrahydrate [AHM = (NH ₄ ) ₆ Mo ₇ O ₂₄ .4H ₂ O] and / or the vanadium source ammonium metavanadate [AMV = NH ₄ VO ₃ ] is used as the Mo element source. As a special difficult, conditions designed, when the element W component of the aqueous training is starting material 3 and ammonium paratungstate [AFW = (NH _{4) 10} W ₁₂ O ₄₁ · 7H ₂ O] in addition to at least one of the two above-mentioned element sources as the starting compound of relevant aqueous solution is used.

It has now surprisingly been found that aqueous solutions prepared as starting material 3 at elevated temperatures during and after the subsequent cooling below the dissolving temperature, even when the Mo element is ≥ 10% by weight and cooling temperatures of up to 20 ° C. or below ( usually not <0 ° C), based on the aqueous solution, are normally stable. That is, no solid precipitates out during or after cooling of the aqueous solution. As a rule, the above statement also applies to correspondingly obtained Mo contents of up to 20% by weight. The same applies to V and W.

Usually is the Mo content of such at temperatures up to 20 ° C or below (usually not below 0 ° C) cooled, as starting mass 3 suitable aqueous solutions, based on the solutions, not more than 35% by weight.

Prominent Findings are attributed to the fact that when loosening with increased Temperature obviously connections of the relevant elements arise the one elevated Water exhibit. This idea is supported by the fact that the one such watery solution obtainable by drying Residue (e.g. spray drying) a correspondingly increased (even at the corresponding low temperatures) solubility in water.

It is therefore expedient to proceed as follows. At a temperature T _L ≥ 60 ° C (e.g. at up to 65 ° C, or at up to 75 ° C, or at up to 85 ° C, or at up to 95 ° C or at ≤ 100 ° C) as a starting mass 3 suitable aqueous solution. After cooling to a temperature T _E <T _L, the finely divided solid starting materials 1, 2 are then incorporated into this aqueous solution. Often T _{L will be} > 70 ° C and T _E ≤ 70 ° C. When accepting somewhat lower dissolving speeds and lower solids contents, however, T _L ≤ 60 ° C is also possible.

The Incorporation of the prepared solid starting materials 1, 2 into the aqueous starting material 3 (aqueous solution or aqueous Suspension or mass made with water) is usually done by adding the starting materials 1, 2 into the, as already stated, cooled aqueous starting material 3 and subsequent mechanical mixing, e.g. using stirring or Dispersing aids, about a period of a few minutes to hours, preferably in one period from 20 to 40 min. As already stated, it is special according to the invention Cheap, if the incorporation of the solid starting materials 1, 2 into the aqueous starting material 3 at temperatures ≤ 70 ° C, preferred at temperatures ≤ 60 ° C and especially preferably at temperatures <40 ° C. In As a rule, the incorporation temperature will be ≥ 0 ° C.

Farther is it convenient if the incorporation of the solid starting materials 1, 2 into an aqueous starting material 3 takes place, the pH at 25 ° C 4 to 7, preferably 5 to 6.5 is. The latter can e.g. B. can be achieved by the aqueous Starting mass 3 adds one or more pH buffer systems. As such For example, an addition of ammonia and acetic acid and / or is suitable formic acid or an addition of ammonium acetate and / or ammonium formate. Of course you can in terms of ammonium carbonate is also used for the aforementioned purpose become. The drying of the starting masses 1, 2 in the watery Initial mass 3 obtained aqueous Mixing is usually done by spray drying. It will be convenient Outlet temperatures of 100 to 150 ° C set. As always in this document can be spray-dried both in cocurrent and in countercurrent become.

own Studies have shown that in the thermal Treating those containing starting materials 1, 3 and optionally 2 intimate dry mix the structure type in the starting masses 1, 2 contained crystallites is essentially preserved, or itself at most converted into other structure types. A fusion of the Components of the starting materials 1, 2 with each other or with those the starting mass 3 does not take place essentially.

This opened, as already indicated above, the possibility after grinding the preformed starting masses 1, 2 the grain class with an im for the multi-element oxide mass (III) desired maximum diameter (usually> 0 up to 300 μm, preferably 0.01 to 100 μm and particularly preferably 0.05 to 20 μm) by means known per se Way to do Classification (e.g. wet or dry sieving) to separate Making the desired Multi-element oxide mass tailor-made use.

in principle can those obtainable according to the invention Multielementoxidmassen III as well as those obtainable according to the invention Multielement oxide active materials I, II in powder form as catalysts for the heterogeneous catalyzed partial gas phase oxidation of acrolein to acrylic acid used (e.g. in a fluidized bed or fluid bed reactor).

As well like the multi-element oxide active materials I, II but also the multi-element oxide active materials III preferably to moldings certain geometry shaped as catalysts for the aforementioned partial oxidation used. The shaping and selection of the geometry can be done as for the multielement oxide active materials I, II have already been described.

That is, either the intimate dry mixture which is still to be thermally treated according to the invention or the multielement oxide active composition III itself obtained from the same according to the invention can be applied to preformed inert catalyst supports. In the former case, the thermal treatment according to the invention is carried out after the catalyst carrier coating made. It is preferably applied to the catalyst support after the thermal treatment according to the invention.

there can the usual Backing materials such as porous or non-porous Aluminum oxides, silicon dioxide, thorium dioxide, zirconium dioxide, silicon carbide or Silicates such as magnesium or aluminum silicate can be used. The carrier body can be regular or irregularly shaped be, being regularly shaped Carrier body with clearly developed surface roughness, e.g. Balls or hollow cylinders are preferred. Suitable is e.g. the use of essentially non-porous, rough-surface, spherical supports Steatite, the diameter of which is 1 to 8 mm, preferably 4 to 5 mm. The Layer thickness of the active composition is expediently in the range 50 up to 500 μm, preferably in the range 150 to 250 μm lying, chosen. It can as a carrier body hollow cylinders (rings) can also be used as already described. It at this point it should be noted that in the manufacture such shell catalysts for coating the support body powder mass to be applied or the carrier body generally with binder moistened and after application, e.g. using hot air, is dried again.

The coating of the carrier bodies is usually carried out in a suitable container for producing the coated catalysts, such as that obtained from the DE-A 29 096 71 or from the EP-A 293 859 is already known. Preferably, as in the EP-A 714700 described coated and given shape.

The method according to the invention can be used in a suitable manner in such a way that the resulting multielement oxide active compositions (III) have a specific surface area of 0.50 to 150 m ² / g, a specific pore volume of 0.10 to 0.90 cm ³ / g and such Show pore diameter distribution that the diameter ranges 0.1 to <1 μm, 1.0 to <10 μm and 10 μm to 100 μm each account for at least 10 of the total pore volume. Also in the EP-A 293 859 can be set as preferred pore diameter distributions.

Of course they can multi-element oxide compositions according to the invention (III) can also be operated as full catalysts. In this regard, it will the intimate dry mixture comprising the starting materials 1, 2 and 3 is preferred immediately to the desired one Compressed catalyst geometry (e.g. by tableting, extruding or extrusion), where appropriate conventional aids, e.g. Graphite or stearic acid as a lubricant and / or molding aid and reinforcing agent such as microfibers made of glass, asbestos, silicon carbide or potassium titanate can be added and thermally according to the invention treated. In general, according to the invention, thermal shaping can also take place here before shaping be treated. Hollow cylinders are preferred all-catalyst geometry with an outer diameter and a length from 2 to 10 mm or 3 to 8 mm and a wall thickness of 1 to 3 mm.

The multielement oxide active compositions obtainable according to the invention are particularly suitable for catalysts with increased activity and selectivity (with a given conversion) for the gas-phase catalytic oxidation of acrolein to acrylic acid. Acrolein, which was generated by the catalytic gas phase partial oxidation of propene, is normally used in the process. As a rule, the reaction gases of this propene oxidation containing acrolein are used without intermediate purification. The gas phase catalytic partial oxidation of acrolein in tube bundle reactors is usually carried out as a heterogeneous fixed bed oxidation. Oxygen, expediently diluted with inert gases (for example in the form of air), is used as the oxidizing agent in a manner known per se. Suitable dilution gases are, for example, N ₂ , CO ₂ , hydrocarbon, recycle reaction gases and / or water vapor. As a rule, in acrolein partial oxidation, an acrolein: oxygen: water vapor inert gas volume ratio of 1: (1 to 3): (0 to 20): (3 to 30), preferably 1 (1 to 3): (0.5 to 10): (7 to 18) set. The reaction pressure is generally 1 to 3 bar and the total space load is preferably 1000 to 3500 Nl / l / h. Typical multi-tube fixed bed reactors are, for example, in the writings DE-A 2830765 . DE-A 2201528 or US-A 3147084 described. The reaction temperature is usually chosen so that the acrolein conversion in a single pass is above 90%, preferably above 98%. Normally, reaction temperatures of 230 to 330 ° C are required.

The multi-element oxide active compositions obtainable according to the invention and the catalysts containing them are particularly suitable for those described in WO 00/53557 and in US Pat DE-A 19910508 High load procedure described. But they are also suitable for the processes of DE-A 10313214 . DE-A 10313213 . DE-A 10313211 . DE-A 10313208 and 10313209.

In addition to the gas phase catalytic partial oxidation of acrolein to acrylic acid, the process products according to the invention are also capable of the gas phase catalytic partial oxidation of other organic compounds, such as, in particular, other alkanes, alkanols, alkanals, alkenes and alkenols (for example propylene, methacrolein, tert. Preferably having 3 to 6 carbon atoms). -Butanol, methyl ether of tert-butanol, isobutene, isobutane or isobutyraldehyde) to olefinically unsaturated aldehydes and / or carboxylic acids, and the corresponding Catalyze nitriles (ammoxidation, especially from propene to acrylonitrile and from isobutene or tert-butanol to methacrylonitrile). The production of acrolein, methacrolein and methacrylic acid may be mentioned by way of example. However, they are also suitable for the oxidative dehydrogenation of paraffinic or olefinic compounds.

to execution the thermal according to the invention Treatment as well as to carry out the Calcinations in the context of the production of starting materials 1 and 2 are basically different types of furnaces such as Tray furnaces, rotary kilns, belt calciners, fluidized bed furnaces or shaft furnaces suitable. Rotary tube furnaces are preferably used for this purpose according to the invention.

example

1. General description of the thermal according to the invention Treatment and for calcination in the context of the production of starting materials 1 and 2 used rotary kiln

A schematic representation of the rotary kiln is shown in the accompanying this document 1 , The following reference numbers refer to them 1 ,

The central element of the rotary kiln is the rotary tube ( 1 ). It is 4000 mm long and has an inside diameter of 700 mm. It is made of stainless steel 1.4893 and has a wall thickness of 10 mm.

On lances are attached to the inner wall of the rotary kiln, one Height of 5 cm and a length of 23.5 cm. They serve primarily the purpose, which is thermal Lift the material to be treated in the rotary kiln and mix it.

On one and the same height of the rotary kiln are equidistant around the circumference (each 90 ° apart) Four lifting lances attached (one quadruple). Along the Rotary kiln are eight such quadruples (each at a distance of 23.5 cm). The stroke lances of two neighboring quadruples are seated against each other on the circumference. At the beginning and end of the rotary kiln (first and last 23.5 cm) there are no lifting lances.

The rotary tube rotates freely in a cuboid ( 2 ), which has four successive, equally long, electrically heated (resistance heating) heating zones in the length of the rotary tube, each of which encloses the circumference of the rotary tube furnace. Each of the heating zones can heat the corresponding rotary tube section to temperatures between room temperature and 850 ° C. The maximum heating output of each heating zone is 30 kW. The distance between the electrical heating zone and the outer surface of the rotary tube is approximately 10 cm. At the beginning and at the end, the rotary tube protrudes approx. 30 cm from the cuboid.

The speed of rotation can be variably set between 0 and 3 revolutions per minute. The rotary tube can be turned left as well as right. When turning to the right, the material remains in the rotary tube, when turning to the left, the material is removed from the entry ( 3 ) to discharge ( 4 ) promoted. The angle of inclination of the rotary tube to the horizontal can be variably set between 0 ° and 2 °. In discontinuous operation, it is actually 0 °. In continuous operation, the lowest point of the rotary tube is at the material discharge. The rotary tube can be rapidly cooled by switching off the electrical heating zones and a fan ( 5 ) is switched on. This sucks through holes in the bottom floor of the cuboid ( 6 ) Ambient air and conveys it through three flaps in the lid ( 7 ) with variably adjustable opening.

The Material entry is over a cellular wheel sluice controls (mass control). The material discharge is, as already mentioned, about the direction of rotation controlled the rotary tube.

at discontinuous operation of the rotary tube can be a quantity of material from 250 to 500 kg can be thermally treated. it is located usually only in the heated part of the rotary tube.

From a lance lying on the central axis of the rotary tube ( 8th ) carry a total of three thermocouples at intervals of 800 mm ( 9 ) vertically into the material. They enable the temperature of the material to be determined. In this document, the temperature of the material is understood to mean the arithmetic mean of the three thermocouple temperatures. Within the material contained in the rotary tube, the maximum deviation of two measured temperatures is expediently less than 30 ° C., preferably less than 20 ° C., particularly preferably less than 10 ° C. and very particularly preferably less than 5 or 3 ° C.

By the rotary tube can gas flows guided by means of which the calcination atmosphere or generally the atmosphere the thermal treatment of the material can be stopped.

The heater ( 10 ) offers the possibility of heating the gas flow into the rotary tube to the desired temperature in advance of its entry into the rotary tube (eg to the temperature desired for the material in the rotary tube). The maximum output of the heater is 1 × 50 kW + 1 × 30 kW. In principle, the heater ( 10 ) act, for example, an indirect heat exchanger. In principle, such a heater can also be used as a cooler. As a rule, however, it is an electric heater in which the gas flow is conducted over metal wires heated by current (expediently a CSN instantaneous heater, type 97D / 80 from C. Schniewindt KG, 58805 Neuerade - DE).

In principle, the rotary tube device provides the possibility of partially or completely circulating the gas flow guided through the rotary tube. The circular line required for this is movably connected to the rotary tube at the rotary tube inlet and at the rotary tube outlet via ball bearings or via graphite press seals. These compounds are flushed with inert gas (eg nitrogen) (sealing gas). The two flushing streams ( 11 ) complete the gas flow through the rotary tube at the inlet to the rotary tube and at the outlet from the rotary tube. The rotary tube expediently tapers at its beginning and at its end and protrudes into the tube of the circular line that leads in and out.

A cyclone is located behind the outlet of the gas flow through the rotary tube ( 12 ), for the separation of solid particles entrained in the gas flow (the centrifugal separator separates solid particles suspended in the gas phase by the interaction of centrifugal and gravity; the centrifugal force of the gas stream rotating as a spiral vortex accelerates the sedimentation of the suspended particles).

The promotion of the cycle gas flow ( 24 ) (the gas circulation) takes place by means of a circulating gas compressor ( 13 ) (Fan), which draws in in the direction of the cyclone and pushes in the other direction. Immediately behind the cycle gas compressor, the gas pressure is usually above one atmosphere. There is a circulating gas outlet behind the circulating gas compressor (via a control valve ( 14 ) cycle gas can be discharged). A cover located behind the outlet (cross-sectional taper by a factor of 3, pressure reducer) ( 15 ) facilitates the outlet.

The pressure behind the rotary tube outlet can be regulated via the control valve. This is done in conjunction with a pressure sensor located behind the rotary tube outlet ( 16 ), the exhaust gas compressor ( 17 ) (Fan), which draws in towards the control valve, the cycle gas compressor ( 13 ) and the fresh gas supply. Relative to the external pressure, the pressure (directly) behind the rotary tube outlet can be set, for example, up to +1.0 mbar above and, for example, down to -1.2 mbar below. That is, the pressure of the gas stream flowing through the rotary tube can be below the ambient pressure of the rotary tube when it leaves the rotary tube.

If the gas flow through the rotary tube is not intended to be circulated at least partially, the connection between the cyclone ( 12 ) and cycle gas compressor ( 13 ) according to the three-way valve principle ( 26 ) closed and the gas flow directly into the exhaust gas purification device ( 23 ) guided. The connection to the exhaust gas cleaning device located behind the cycle gas compressor is also closed in this case according to the three-way valve principle. If the gas flow consists essentially of air, this is in this case via the cycle gas compressor ( 13 ) sucked in ( 27 ). The connection to the cyclone is closed according to the three-way valve principle. In this case, the gas stream is preferably drawn through the rotary tube, so that the internal pressure of the rotary tube is less than the ambient pressure.

at continuous operation of the rotary kiln device, the pressure behind the rotary tube outlet advantageous –0.2 mbar below the external pressure set horizontally. With discontinuous operation of the rotary tube device the pressure behind the rotary tube outlet is advantageously –0.8 mbar below the external pressure set horizontally. The slight negative pressure serves the purpose of a Avoiding contamination of the ambient air with a gas mixture from the rotary kiln.

There are sensors between the cycle gas compressor and the cyclone ( 18 ), which determine, for example, the ammonia content and the oxygen content in the cycle gas. The ammonia sensor preferably works according to an optical measuring principle (the absorption of light of a certain wavelength correlates in proportion to the ammonia content of the gas) and is expediently a device from Perkin & Elmer of type MCS 100. The oxygen sensor is based on the paramagnetic properties of oxygen and is expedient an Oximat from Siemens of the type Oxymat MAT SF 7MB1010-2CA01-1AA1-Z.

Between the aperture ( 15 ) and the heater ( 10 ) Gases such as air, nitrogen, ammonia or other gases can make up the actually recirculated gas fraction ( 19 ) are added. A basic load of nitrogen is often added ( 20 ). With a separate nitrogen / air splitter ( 21 ) can be reacted to the measured value of the oxygen sensor.

The discharged cycle gas component ( 22 ) (Exhaust gas) often contains not completely harmless gases such as NO _x , acetic acid, NH ₃ , etc.), which is why these are normally separated in an exhaust gas cleaning device ( 23 ).

To the exhaust gas is usually initially via a Wash column performed (is essentially a column free of internals, which is in front of its Output contains a separating pack; the exhaust gas and watery spray are guided in cocurrent and in countercurrent (2 spray nozzles with opposite spray direction).

Out coming to the scrubbing column, the exhaust gas is led into a device which contains a fine dust filter (usually a bundle of bag filters) Inside the penetrated exhaust gas is carried away. Then finally in one Muffle burned.

Using a sensor ( 28 ) from KURZ Instruments, Inc., Montery (USA) of the Model 455 Jr type, the amount of the gas flow other than the sealing gas and fed to the rotary tube is measured and regulated (measuring principle: thermal convective mass flow measurement using a temperature anemometer).

at Continuous operation becomes material goods and gas phase in counterflow passed through the rotary kiln.

nitrogen in connection with this example always means nitrogen a purity> 99 % By volume.

2. Production of the starting mass 1 (phase B) with the stoichiometry Cu ₁ Mo _0.5 W _0.5 O ₄

98 l of a 25% by weight aqueous NH ₃ solution were added to 603 l of water. 100 kg of copper (II) acetate hydrate (content: 40.0% by weight of CuO) were then dissolved in the aqueous mixture, giving a clear, deep blue aqueous solution 1 which contained 3.9% by weight of Cu and had room temperature ,

Independent of solution 1, 620 l of water were heated to 40 ° C. While maintaining the 40 ° C 27.4 kg ammonium heptamolybdate tetrahydrate (81.5 wt .-% MoO ₃ ) were within 20 min. dissolved with stirring. Then 40.4 kg of ammonium paratungstate heptahydrate (88.9% by weight WO ₃ ) were added and after heating up to 90 ° C. within 45 min. dissolved at this temperature with stirring. A clear, yellow-orange colored aqueous solution 2 was obtained.

Then was the watery solution 1 into the 90 ° C showing solution 2 stirred in, the temperature of the total mixture did not drop below 80 ° C. The resulting aqueous Suspension was 30 min. at 80 ° C stirred. After that she was using a spray dryer from Niro-Atomizer (Copenhagen) type S-50-N / R spray-dried (gas inlet temperature: 315 ° C, gas outlet temperature: 110 ° C, direct current). The spray powder had a particle diameter of 2 to 50 μm.

• – die thermisch Behandlung erfolgte kontinuierlich mit einem Materialguteintrag von 50 kg/h an Stränglingen;
• – der Neigungswinkel des Drehrohres zur Horizontalen betrug 2°;
• – im Gegenstrom zum Materialgut wurde ein Luftstrom von 75 Nm³/h durch das Drehrohr geführt, der von insgesamt (2 × 25) 50 Nm³/h Sperrgas der Temperatur 25°C ergänzt wurde;
• – der Druck hinter dem Drehrohrausgang lag 0,8 mbar unter dem Außendruck;
• – das Drehrohr rotierte mit 1,5 Umdrehungen/min links herum;
• – es wurde keine Kreisgasfahrweise angewendet;
• – beim ersten Durchgang der Stränglinge durch das Drehrohr wurde die Temperatur der Drehrohraußenwand auf 340°C eingestellt, der Luftstrom wurde mit einer Temperatur von 20 bis 30°C in das Drehrohr geführt;
• – anschließend wurden die Stränglinge mit der selben Durchsatzmenge und abgesehen von den nachfolgenden Unterschieden unter den gleichen Bedingungen durch das Drehrohr geführt: – die Temperatur der Drehrohrwand wurde auf 790°C eingestellt; – der Luftstrom wurde auf eine Temperatur von 400°C erwärmt in das Drehrohr geführt.

100 kg of the light green spray powder obtained in this way were metered into a kneader from AMK (Aachen mixing and kneading machine factory) of the type VIU 160 (Sigma blades) and kneaded with the addition of 8 l of water (residence time: 30 min, temperature: 40 to 50 ° C). The kneaded material was then emptied into an extruder and strands (length: 1-10 cm; length: 1-10 cm; using the extruder (Bonnot Company (Ohio), type: G 103-10 / D7A-572K (6 '' extruder W / packer); The strands were dried on a belt dryer for 1 hour at a temperature of 120 ° C. (material temperature). The dried strands were then thermally treated (calcined) in the rotary kiln described under “1” as follows:

• - The thermal treatment was carried out continuously with a material input of 50 kg / h of strands;
• - The angle of inclination of the rotary tube to the horizontal was 2 °;
• - In counterflow to the material, an air flow of 75 Nm ³ / h was passed through the rotary tube, which was supplemented by a total of (2 × 25) 50 Nm ³ / h sealing gas at a temperature of 25 ° C;
• - The pressure behind the rotary tube outlet was 0.8 mbar below the external pressure;
• - The rotary tube rotated to the left at 1.5 revolutions / min;
• - No gas cycle mode was used;
• - The first time the strands passed through the rotary tube, the temperature of the outer tube of the rotary tube was set to 340 ° C, the air flow was fed into the rotary tube at a temperature of 20 to 30 ° C;
• - The strands were then passed through the rotary tube with the same throughput and apart from the following differences under the same conditions: - The temperature of the rotary tube wall was set to 790 ° C; - The air flow was heated to a temperature of 400 ° C in the rotary tube.

• 1. CuMoO₄-III mit Wolframitstruktur;
• 2. HT-Kupfermolybdat.

The strands, which had a red-brown color, were then ground on a biplex cross-flow classifier mill (BQ 500) from Hosokawa-Alpine (Augsburg) to an average particle diameter of 3 to 5 μm. The initial mass 1 thus obtained had a BET surface area 1 1 m ² / g. The following phases were determined by means of X-ray diffraction:

• 1. CuMoO ₄ -III with a tungsten structure;
• 2. HT copper molybdate.

3. Production of the starting mass ₂ (phase C) with the stoichiometry CuSb ₂ O ₆

52 kg of antimony trioxide (99.9% by weight of Sb ₂ O ₃ ) were suspended in 216 l of water (25 ° C.) with stirring. The resulting aqueous suspension was heated to 80 ° C. The mixture was then stirred for 20 minutes while maintaining the 80 ° C. Then 40 kg of a 30% strength by weight aqueous hydrogen peroxide solution were added over the course of an hour, the 80 ° C. being maintained. While maintaining this temperature, stirring was continued for 1.5 hours. Then 20 l of warm water at 60 ° C. were added and an aqueous suspension 1 was thus obtained. 618.3 kg of an aqueous ammoniacal copper (II) acetate solution (60.8 g of copper acetate per kg of solution and 75 l of a 25% by weight aqueous ammonia solution in the 618.3 kg of solution were introduced into these at a temperature of 70 ° C. ) stirred. The mixture was then heated to 95 ° C. and stirred at this temperature for 30 min. Then 50 l of 70 ° C warm water were added and heated to 80 ° C.

Finally was the watery Spray dried suspension (spray dryer from Niro-Atomizer (Copenhagen), type S-50-N / R, gas inlet temperature 360 ° C, gas outlet temperature 110 ° C, direct current). The spray powder had a particle diameter of 2 to 50 μm.

75 kg of spray powder thus obtained were in a kneader from AMK (Aachen mixing and kneading machines VIU 160 factory (Sigma blades) dosed and with additions kneaded by 12 l of water (residence time: 30 min, temperature 40 to 50 ° C). After that the kneaded material was fed into an extruder (same extruder as for phase B production) emptied and by means of the extruder into strands (length 1-10 cm; Diameter 6 mm). The strands were 1 h on a belt dryer at a temperature of 120 ° C (Material temperature) dried.

• – die thermische Behandlung erfolgte diskontinuierlich mit einer Materialgutmenge von 250 kg;
• – der Neigungswinkel des Drehrohres zur Horizontalen betrug ≈ 0°C;
• – das Drehrohr rotierte mit 1,5 Umdrehungen/min rechts herum;
• – durch das Drehrohr wurde ein Gasstrom von 205 Nm³/h geführt; dieser bestand zu Beginn der thermischen Behandlung aus 180 Nm³/h Luft und 1 × 25 Nm³/h N₂ als Sperrgas; der das Drehrohr verlassende Gasstrom wurde um weitere 1 × 25 Nm³/h N₂ ergänzt; von diesem Gesamtstrom wurden 22–25 Vol.-% ins Drehrohr rückgeführt und der Rest ausgelassen; die Auslassmenge wurde durch das Sperrgas und als Restmenge durch Frischluft ergänzt;
• – der Gasstrom wurde mit 25°C ins Drehrohr geführt;
• – der Druck hinter dem Drehrohrausgangs lag 0,5 mbar unterhalb Außendruck (Normaldruck);
• – die Temperatur im Materialgut wurde zunächst innerhalb von 1,5 h linear von 25°C auf 250°C erhöht; dann wurde die Temperatur im Materialgut innerhalb von 2 h linear von 250°C auf 300°C erhöht und diese Temperatur 2 h gehalten; dann wurde die Temperatur im Materialgut innerhalb von 3 h linear von 300°C auf 405°C erhöht und diese Temperatur anschließend 2 h gehalten; dann wurden die Heizzonen abgeschaltet und die Temperatur innerhalb des Materialgutes durch Aktivierung der Schnellkühlung des Drehrohres durch Ansaugen von Luft innerhalb von 1 h auf eine unterhalb von 100°C liegende Temperatur erniedrigt und schließlich auf Umgebungstemperatur abgekühlt.

250 kg of strands obtained in this way were thermally treated (calcined) in the rotary kiln described under “1”:

• - The thermal treatment was carried out discontinuously with a material quantity of 250 kg;
• - The angle of inclination of the rotary tube to the horizontal was ≈ 0 ° C;
• - The rotary tube rotated clockwise at 1.5 revolutions / min;
• - A gas flow of 205 Nm ³ / h was passed through the rotary tube; at the beginning of the thermal treatment, this consisted of 180 Nm ³ / h air and 1 × 25 Nm ³ / h N ₂ as sealing gas; the gas stream leaving the rotary tube was supplemented by a further 1 × 25 Nm ³ / h N ₂ ; 22-25 vol .-% of this total flow were returned to the rotary tube and the rest were left out; the outlet volume was supplemented by the sealing gas and the remaining volume by fresh air;
• - The gas stream was fed into the rotary tube at 25 ° C;
• - The pressure behind the rotary tube outlet was 0.5 mbar below the external pressure (normal pressure);
• - The temperature in the material was first increased linearly from 25 ° C to 250 ° C within 1.5 h; then the temperature in the material was increased linearly from 250 ° C. to 300 ° C. within 2 hours and this temperature was maintained for 2 hours; the temperature in the material was then increased linearly from 300 ° C. to 405 ° C. in the course of 3 hours and this temperature was then maintained for 2 hours; then the heating zones were switched off and the temperature within the material was reduced to below 100 ° C. within 1 h by activating the rapid cooling of the rotary tube by sucking in air and finally cooled to ambient temperature.

The resulting pulverulent starting mass _{2 had} a specific BET surface area of 0.6 m ² / g and the composition CuSb ₂ O ₆ . The powder X-ray diagram of the powder obtained essentially showed the diffraction reflections of CuSb ₂ O ₆ (comparison spectrum 17-0284 from the JCPDS-ICDD file).

4. Production of the starting mass 3 with the stoichiometry Mo ₁₂ V _3.35 W _1.38

900 l of water were introduced into a stirred kettle at 25 ° C. with stirring. 122.4 kg of ammonium heptamolybdate tetrahydrate (81.5% by weight of MoO ₃ ) were then added and the mixture was heated to 90 ° C. with stirring. Then, while maintaining the 90 ° C., 22.7 kg of ammonium metavanadate and finally 20.0 kg of ammonium paratungstate heptahydrate (88.9% by weight of WO ₃ ) were stirred in first. A clear orange solution was obtained by stirring at 90 ° C. for a total of 80 minutes. This was cooled to 80 ° C. Then, while maintaining the 80 ° C., 18.8 kg of acetic acid (≈ 100% by weight, glacial acetic acid) and then 24 l of 25% by weight aqueous ammonia solution were stirred in first.

The solution stayed clear and orange and was spray-dried spray-dried from Niro-Atomizer (Copenhagen), type S-50-N / R (Gas inlet temperature: 260 ° C, Gas outlet temperature: 110 ° C, DC). The resulting spray powder formed the starting mass 3 and had a particle diameter of 2 to 50 μm.

5. Production of the dry mass to be thermally treated according to the invention with the stoichiometry (Mo ₁₂ V _3.46 W _1.39 ) _0.87 (CuMo _0.5 W _0.5 O ₄ ) _0.4 (CuSb ₂ O ₆ ) _{0, 4}

In a trough kneader from AMK (Aachen mixing and kneading machines Factory) of type VIU 160 with two sigma blades became 75 kg of starting mass 3, 5.2 l of water and 6.9 kg of acetic acid (100 wt .-% glacial acetic acid) submitted and during Kneaded for 22 min. Subsequently 3.1 kg of starting mass 1 and 4.7 kg of starting mass 2 were added and during kneaded for a further 8 min (T ≈ 40 up to 50 ° C).

After that the kneaded material was fed into an extruder (same extruder as for phase B production) and emptied into strands using the extruder (1st up to 10 cm in length, 6 mm diameter). These were on a belt dryer during 1 h dried at a temperature (material temperature) of 120 ° C.

• – die thermische Behandlung erfolgte diskontinuierlich mit einer Materialgutmenge von 306 kg;
• – der Neigungswinkel des Drehrohres zur Horizontalen betrug ≈ 0°;
• – das Drehrohr rotierte mit 1,5 Umdrehungen/min rechts herum;
• – zunächst wurde die Materialguttemperatur innerhalb von 2 h im wesentlichen linear von 25°C auf 100°C erhitzt; während dieser Zeit wird durch das Drehrohr ein (im wesentlichen) Stickstoffstrom von 205 Nm³/h zugeführt. Im stationären Zustand (nach Verdrängung der ursprünglich enthaltenen Luft) ist dieser wie folgt zusammengesetzt: 110 Nm³/h Grundlast-Stickstoff (20), 25 Nm³/h Sperrgas-Stickstoff (11), und 70 Nm³/h rezirkuliertes Kreisgas (19). Der Sperrgas-Stickstoff wurde mit einer Temperatur von 25°C zugeführt. Das Gemisch der beiden anderen Stickstoffströme wurde jeweils mit der Temperatur ins Drehrohr geführt, die das Materialgut im Drehrohr jeweils aufwies.
• – anschießend wurde die Materialguttemperatur mit einer Heizrate von 0,7°C/min von 100°C auf 320°C aufgeheizt; bis zum Erreichen einer Materialguttemperatur von 300°C wurde durch das Drehrohr ein Gasstrom von 205 Nm³/h geführt, der wie folgt zusammengesetzt war: 110 Nm³/h bestehend aus Grundlast-Stickstoff (20) und im Drehrohr freigesetzten Gasen, 25 Nm³/h Sperrgas-Stickstoff (11) und 70 Nm³/h rezirkuliertes Kreisgas (19). Der Sperrgas-Stickstoff wurde mit einer Temperatur von 25°C zugeführt. Das Gemisch der beiden anderen Gasströme wurde jeweils mit der Temperatur ins Drehrohr geführt, die das Materialgut im Drehrohr jeweils aufwies. Ab Überschreiten der Materialguttemperatur von 160°C bis zum Erreichen einer Materialguttemperatur von 300°C wurden aus dem Materialgut 40 mol-% der im Verlauf der gesamten thermischen Behandlung des Materialgutes insgesamt freigesetzten Ammoniakmenge M^A freigesetzt.
• – bei Erreichen der Materialguttemperatur von 320°C wurde der Sauerstoffgehalt des dem Drehrohr zugeführten Gasstromes von 0 Vol.-% auf 1,5 Vol.-% erhöht und über die nachfolgenden 4 h beibehalten. Gleichzeitig wurde die in den vier das Drehrohr beheizenden Heizzonen herrschende Temperatur um 5°C abgesenkt (auf 325°C) und so während der nachfolgenden 4 h aufrechterhalten. Die Materialguttemperatur durchlief dabei ein oberhalb von 325°C liegendes Temperaturmaximum, das 340°C nicht überschritt, bevor die Materialguttemperatur wieder auf 325°C sank. Die Zusammensetzung des durch das Drehrohr geführten Gasstroms von 205 Nm³/h wurde während dieses Zeitraums von 4 h wie folgt geändert: 95 Nm³/h bestehend aus Grundlast-Stickstoff (20) und im Drehrohr freigesetzten Gasen; 25 Nm³/h Sperrgas-Stickstoff (11); 70 Nm³/h rezirkuliertes Kreisgas; und 15 Nm³/h Luft über den Splitter (21). Der Sperrgas-Stickstoff wurde mit einer Temperatur von 25°C zugeführt. Das Gemisch der anderen Gasströme wurde jeweils mit der Temperatur ins Drehrohr geführt, die das Materialgut im Drehrohr jeweils aufwies. Ab Überschreiten der Materialguttemperatur von 300°C bis zum Ablauf der 4 h wurden aus dem Materialgut 55 mol-% der im Verlauf der gesamten thermischen Behandlung des Materialguts insgesamt freigesetzten Ammoniakmenge M^A freigesetzt (damit waren bis zum Ablauf der 4 h insgesamt 40 mol-% + 55 mol-% = 95 mol-% der Ammoniakmenge M^A freigesetzt).
• – mit Ablauf der 4 h wurde die Temperatur des Materialguts mit einer Heizrate von 0,85°C/min innerhalb von etwa 1,5 h auf 400°C erhöht. Anschließend wurde diese Temperatur 30 min aufrechtgehalten. Die Zusammensetzung des dem Drehrohr zugeführten Gasstroms von 205 Nm³/h war während dieser Zeit wie folgt: 95 Nm³/h zusammengesetzt aus Grundlast-Stickstoff (20) und im Drehrohr freigesetzten Gasen; 15 Nm³/h Luft (Splitter (21)); 25 Nm³/h Sperrgas-Stickstoff (11); und 70 Nm³/h rezirkuliertes Kreisgas. Der Sperrgas-Stickstoff wurde mit einer Temperatur von 25°C zugeführt. Das Gemisch der anderen Gasströme wurde jeweils mit der Temperatur ins Drehrohr geführt, die das Materialgut im Drehrohr jeweils aufwies.
• – durch Verringerung der Temperatur des Materialguts wurde die Calcination beendet; dazu wurden die Heizzonen aus- und die Schnellkühlung des Drehrohres durch Ansaugen von Luft eingeschaltet, und die Materialguttemperatur innerhalb von 2 h auf eine unterhalb von 100°C liegende Temperatur erniedrigt und schließlich auf Umgebungstemperatur abgekühlt; mit der Abschaltung der Heizzonen wurde die Zusammensetzung des dem Drehrohr zugeführten Gasstroms von 205 Nm³/h auf folgendes Gemisch verändert: 110 Nm³/h zusammengesetzt aus Grundlast-Stickstoff (20) und im Drehrohr freigesetzten Gasen; 0 Nm³/h Luft (Splitter (21)); 25 Nm³/h Sperrgas-Stickstoff (11); und 70 Nm³/h rezirkuliertes Kreisgas. Der Gasstrom wurde dem Drehrohr mit einer Temperatur von 25°C zugeführt.
• – während der gesamten thermischen Behandlung lag der Druck (unmittelbar) hinter dem Drehrohrausgang 0,2 mbar unterhalb des Außendrucks.

306 kg of the dried strands were then thermally treated in the rotary kiln described under "1" as follows:

• - The thermal treatment was carried out discontinuously with a material quantity of 306 kg;
• - The angle of inclination of the rotary tube to the horizontal was ≈ 0 °;
• - The rotary tube rotated clockwise at 1.5 revolutions / min;
• - First, the material temperature was heated linearly from 25 ° C to 100 ° C within 2 h; during this time, a (substantially) nitrogen flow of 205 Nm ³ / h is fed through the rotary tube. In the steady state (after displacement of the air originally contained), it is composed as follows: 110 Nm ³ / h base load nitrogen ( 20 ), 25 Nm ³ / h sealing gas nitrogen ( 11 ), and 70 Nm ³ / h recirculated cycle gas ( 19 ). The sealing gas nitrogen was supplied at a temperature of 25 ° C. The mixture of the other two nitrogen streams was fed into the rotary tube at the temperature that the material in the rotary tube had.
• - The material temperature was then heated from 100 ° C to 320 ° C at a heating rate of 0.7 ° C / min; until a material temperature of 300 ° C was reached, a gas flow of 205 Nm ³ / h was passed through the rotary tube, which was composed as follows: 110 Nm ³ / h consisting of base load nitrogen ( 20 ) and gases released in the rotary tube, 25 Nm ³ / h sealing gas nitrogen ( 11 ) and 70 Nm ³ / h recirculated cycle gas ( 19 ). The sealing gas nitrogen was supplied at a temperature of 25 ° C. The mixture of the other two gas streams was fed into the rotary tube at the temperature that the material had in the rotary tube. From exceeding the material temperature of 160 ° C to reaching a material temperature of 300 ° C, 40 mol% of the total amount of ammonia M ^A released in the course of the entire thermal treatment of the material were released from the material.
• - When the material temperature of 320 ° C was reached, the oxygen content of the gas stream fed to the rotary tube was increased from 0% by volume to 1.5% by volume and maintained over the subsequent 4 hours. At the same time, the temperature prevailing in the four heating zones heating the rotary tube was lowered by 5 ° C (to 325 ° C) and thus maintained during the following 4 hours. The material temperature passed through a temperature maximum above 325 ° C, which did not exceed 340 ° C before the material temperature dropped again to 325 ° C. The composition of the gas flow through the rotary tube of 205 Nm ³ / h was changed during this period of 4 h as follows: 95 Nm ³ / h consisting of base load nitrogen ( 20 ) and gases released in the rotary tube; 25 Nm ³ / h sealing gas nitrogen ( 11 ); 70 Nm ³ / h recirculated cycle gas; and 15 Nm ³ / h air over the splitter ( 21 ). The sealing gas nitrogen was supplied at a temperature of 25 ° C. The mixture of the other gas streams was fed into the rotary tube at the temperature that the material had in the rotary tube. From exceeding the material temperature of 300 ° C until the end of the 4 h, 55 mol% of the total amount of ammonia M ^A released in the course of the entire thermal treatment of the material was released (thus a total of 40 mol % + 55 mol% = 95 mol% of the amount of ammonia M ^A released).
• - When the 4 h had elapsed, the temperature of the material was increased to 400 ° C in about 1.5 h at a heating rate of 0.85 ° C / min. This temperature was then maintained for 30 minutes. During this time, the composition of the gas flow of 205 Nm ³ / h fed to the rotary tube was as follows: 95 Nm ³ / h composed of base load nitrogen ( 20 ) and gases released in the rotary tube; 15 Nm ³ / h air (splitter ( 21 )); 25 Nm ³ / h sealing gas nitrogen ( 11 ); and 70 Nm ³ / h recirculated cycle gas. The sealing gas nitrogen was supplied at a temperature of 25 ° C. The mixture of the other gas streams was fed into the rotary tube at the temperature that the material had in the rotary tube.
• - The calcination was ended by reducing the temperature of the material; For this purpose, the heating zones were switched off and the rapid cooling of the rotary tube was switched on by sucking in air, and the temperature of the material goods was reduced to a temperature below 100 ° C. within 2 hours and finally cooled to ambient temperature; When the heating zones were switched off, the composition of the gas flow fed to the rotary tube was changed from 205 Nm ³ / h to the following mixture: 110 Nm ³ / h composed of base load nitrogen ( 20 ) and gases released in the rotary tube; 0 Nm ³ / h air (splitter ( 21 )); 25 Nm ³ / h sealing gas nitrogen ( 11 ); and 70 Nm ³ / h recirculated cycle gas. The gas stream was fed to the rotary tube at a temperature of 25 ° C.
• - During the entire thermal treatment, the pressure (immediately) behind the rotary tube outlet was 0.2 mbar below the external pressure.

6. Shape of the multimetal oxide active material

The obtained catalytically in "4." active material was measured using a biplex cross-flow classifier mill (BQ 500) (from Hosokawa-Alpine Augsburg) into a fine powder ground, of which 50% of the powder particles are a sieve with a mesh size 1 to 10 μm happened and its proportion of particles with a longest dimension above 50 μm less than 1%.

Using the ground powder, as in S1 EP-B 714700 annular carrier body (7 mm outer diameter, 3 mm length, 4 mm inner diameter, steatite of the type C220 from CeramTec with a surface roughness Rz of 45 μm). The binder was an aqueous solution of 75% by weight of water and 25% by weight of glycerin.

The Active mass fraction of the resulting coated catalysts was however, in contrast to the aforementioned example S1 to 20 wt .-% (based on the total weight of carrier body and active mass) selected. The relationship powder and binder were adjusted proportionally.

2 shows the percentage of M ^A as a function of the material temperature in ° C. 3 shows the ammonia concentration of the atmosphere A in vol .-% over the thermal treatment depending on the material temperature in ° C.

7. Testing the shell catalysts

The coated catalysts were tested as follows in a model contact tube washed with a salt bath (mixture of potassium nitrate and sodium nitrate):
Model contact tube: V2A steel, 2 mm wall thickness, 26 mm inside diameter, centered a thermo sleeve (to accommodate a thermocouple) with an outside diameter of 4 mm, 1.56 l of the free model contact tube space were filled with the shell catalyst;
The reaction gas mixture had the following starting composition:
4.8% by volume of acrolein, 7% by volume of oxygen, 10% by volume of water vapor, 76% by volume of nitrogen and the remainder a mixture of carbon oxides and oxygenates of propylene.

The Model contact tube was at 2800 Nl / h of reaction gas starting mixture loaded. The temperature of the salt bath was set so that with a single pass an acrolein conversion of 99.3 mol% resulted.

The in this regard required salt bath temperature T was 262 ° C and the selectivity of acrylic acid formation was 96.4 mol% of acrylic acid.

On At this point it should be noted that with these shell catalysts regular loading of tube bundle reactors with 5000 to 40000 contact tubes (wall thickness typically 1 to 3 mm, inner diameter usually 20 to 30 mm, often 21 up to 26 mm, length typically 2 to 4 m) possible which is such that, as a result of the homogeneous manufacture the active mass at an arbitrary picked sample of 12 contact tubes the difference between the arithmetic mean activity and the highest or lowest activity no longer than 8 ° C, frequently not more than 6 ° C, often not more than 4 ° C and cheap make not more than 2 ° C is.

As a measure of the activity of the contact tube feed, the temperature used is that of a salt bath washing around the individual contact tube (mixture of 53% by weight of potassium nitrate, 40% by weight of sodium nitrite and 7% by weight of sodium nitrate), so that once Passage of a reaction gas mixture of 4.8% by volume of acrolein, 7% by volume of oxygen, 10% by volume of water vapor and 78.2% by volume of nitrogen (when the catalyst feed is loaded with 85 Nl acrolein / l catalyst feed · h ) an acrolein conversion of 97 mol% is achieved through the charged catalyst tube (under “l catalyst feed”, the volumes within the catalyst tube are not included where there are pure pre- or post-fillings of inert material, but only the bulk volumes that Contain shaped catalyst body (optionally diluted with inert material).

Such Catalyst feeds are particularly suitable for high acrolein loads (e.g. ≥ 135 Nl / l · h to 350 Nl / l · h and more).

Comparative Example 1

Everything was done as in the example. However, the gas mixture flow fed to the rotary tube contained 95 Nm ³ / h composed of base load nitrogen (i.e. on the way to the material temperature of 100 ° C or 300 ° C). 20 ) and gases released in the rotary tube and 70 Nm ³ / h recirculated cycle gas, but 15 Nm ³ / h air (splitter ( 21 )) and thus 1.5 vol .-% molecular oxygen.

The in the shell catalyst test for an acrolein conversion of 99.3 mol% required salt bath temperature was 268 ° C and Selectivity of Acrylic acid formation was only 94.2 mol%.

Comparative Example 2

Everything was carried out as in the example. During the The total duration of the thermal treatment included that of the rotary tube supplied Gas flow, however, no air (instead of the air flow according to the example was about the splitter is always supplied with an appropriate nitrogen flow.

The in the shell catalyst test for an acrolein conversion of 99.3 mol% required salt bath temperature was 279 ° C and the Selectivity of Acrylic acid formation was only 91.0 mol%.

Claims (24)

Process for the preparation of catalytically active multielement oxide compositions which contain at least one of the elements Nb and W and the elements Mo, V and Cu, the molar proportion of the element Mo in the total amount of all elements of the catalytically active multielement oxide composition other than oxygen being 20 mol% to 80 mol%, the molar ratio of Mo contained in the catalytically active multielement oxide composition to V, Mo / V contained in the catalytically active multielement oxide composition is 15: 1 to 1: 1, the corresponding molar ratio Mo / Cu 30: 1 to 1: 3 and the corresponding molar ratio Mo / (total amount of W and Nb) is 80: 1 to 1: 4 and in which an intimate, including ammonium ion, is obtained from starting compounds which contain the elemental constituents of the multi-element oxide mass other than oxygen containing dry mixture and this in an atmosphere low in molecular oxygen at elevated temperature Treated rmisch, at temperatures ≥ 160 ° C at least a portion of the ammonium ions contained in the intimate dry mixture is decomposed with the release of ammonia, characterized in that the thermal treatment takes place as follows: - The intimate dry mixture is at a temperature rate of ≤ 10 ° C / min heated to a decomposition temperature in the decomposition temperature range of 240 ° C to 360 ° C and held in this temperature range until at least 90 mol% of the total thermal treatment of the intimate dry mix from the intimate dry mix at temperatures above 160 ° C total released total amount M ^A of ammonia have been released; - At the latest when the intimate dry mixture has reached the temperature of 230 ° C., the molecular oxygen content of atmosphere A, in which the thermal treatment of the intimate dry mixture takes place, becomes ≤ 0.5% by volume. lowered and this low oxygen content is maintained until at least 20 mol% of the total amount M ^A of ammonia released in the total course of the thermal treatment has been released; - At the earliest when> 70 mol% of the total amount M ^A of ammonia released in the total course of the thermal treatment has been released, the intimate dry mixture is removed from the decomposition temperature range at a rate of ≤ 10 ° C./min - and into the calcination temperature range from 380 to 450 ° C and - at the latest when 98 mol% of the total amount M ^A of ammonia released in the total course of the thermal treatment has been released, the content of the atmosphere A of molecular oxygen is reduced to> 0.5 vol. -% to 4 vol .-% increased and the intimate dry mixture calcined at this increased oxygen content of the atmosphere A in the calcination temperature range. A method according to claim 1, characterized in that the content of the intimate dry mix to be thermally treated of ammonium ions, based on the total molar content of the intimate Dry mixture of elemental constituents other than oxygen the later catalytically active multielement oxide mass, ≥ 5 mol%. A method according to claim 1 or 2, characterized in that that the temperature rate at which the intimate dry mix is applied to the Decomposition temperature warmed is ≤ 5 ° C / min. Method according to one of claims 1 to 3, characterized in that the temperature rate, with which the intimate dry mixture is heated to the decomposition temperature, ≤ 3 ° C / min. Method according to one of claims 1 to 4, characterized in that that the decomposition temperature range is in the range of 300 up to 350 ° C extends. Method according to one of claims 1 to 5, characterized in that the intimate dry mixture is kept in the decomposition temperature range until at least 95 mol% of the total thermal treatment of the intimate dry mixture from the intimate dry mixture at temperatures above 160 ° C in total released total amount M ^A of ammonia have been released. Method according to one of claims 1 to 6, characterized in that that at the latest then when the intimate dry mixture reaches the temperature of 230 ° C has the content of the atmosphere A of molecular oxygen ≤ 0.3 Vol .-% is. Method according to one of claims 1 to 7, characterized in that the content of the atmosphere A in molecular oxygen is increased to a value> 0.5 vol .-% to 4 vol .-% before 80 mol% of the total thermal treatment total released total amount M ^A of ammonia have been released. Method according to one of claims 1 to 8, characterized in that the content of the atmosphere A in molecular oxygen, at the latest when 98 mol% of the total amount M ^A of ammonia released in the course of the thermal treatment have been released, to a value of 0.6 to 4 vol .-% is increased. Method according to one of Claims 1 to 9, characterized in that the content of molecular oxygen in the atmosphere A, at the latest when 98 mol% of the total amount M ^A of ammonia released in the course of the thermal treatment has been released, to a value of 1 to 3 vol .-% is increased. Method according to one of claims 1 to 10, characterized in that that the calcination temperature range is in the range of 380 to 430 ° C extends. Method according to one of claims 1 to 11, characterized in that that after the end of the calcination, the intimate dry mixture inside a period of ≤ 5 h is cooled to a temperature ≤ 100 ° C. A method according to claim 12, characterized in that cooling up to at least a temperature of 350 ° C. in an atmosphere A, whose molecular oxygen content is ≤ 5% by volume. Method according to one of claims 1 to 13, characterized in that that the ammonia content of the atmosphere A in the course of the thermal treatment goes through a maximum, that ≤ 10 vol .-% is. A method according to claim 14, characterized in that the atmosphere A reaches its maximum ammonia content before the intimate dry mix has reached the calcination temperature range. Method according to one of claims 1 to 15, characterized in that the catalytically active multimetal oxide mass of general stoichiometry I Mo ₁₂ V _a X ¹ _b X ² _c X ³ _d X ⁴ _e X ⁵ _f X ⁶ _g O _n (I), suffice in which the variables have the following meaning: X ¹ = W, Nb, Ta, Cr and / or Ce, X ² = Cu, Ni, Co, Fe, Mn and / or Zn, X ³ = Sb and / or Bi , X ⁴ = one or more alkali metals, X ⁵ = one or more alkaline earth metals, X ⁶ = Si, Al, Ti and / or Zr, a = 1 to 6, b = 0.2 to 4, c = 0.5 to 1 8, d = 0 to 40, e = 0 to 2, f = 0 to 4, g = 0 to 40 and n = a number which is determined by the valency and frequency of the elements in I other than oxygen. Process according to one of Claims 1 to 16, characterized in that the catalytically active multimetal oxide composition is of the general formula III, [A] _p [B] _q [C] _r (III) in which the variables have the following meaning: A = Mo ₁₂ V _a X ¹ _b X ² _c X ³ _d X ⁴ _e X ⁵ _f X ⁶ _g O _x , B = X ⁷ ₁ Cu _h H _i O _y , C = X ⁸ ₁ Sb _j H _k O _z , X ¹ = W, Nb, Ta, Cr and / or Ce, X ² = Cu, Ni, Co, Fe, Mn and / or Zn, X ³ = Sb and / or Bi, X ⁴ = Li, Na, K, Rb, Cs and / or H, X ⁵ = Mg, Ca, Sr and / or Ba, X ⁶ = Si, Al, Ti and / or Zr, X ⁷ = Mo, W, V, Nb and / or Ta, X ⁸ = Cu, Ni, Zn, Co, Fe, Cd, Mn, Mg, Co, Sr and / or Ba, a = 1 to 8, b = 0.2 to 5, c = 0 to 23, d = 0 to 50, e = 0 to 2, f = 0 to 5, g = 0 to 50, h = 0.3 to 2.5 i = 0 to 2 , j = 0.1 to 50, k = 0 to 50, x, y, z = numbers which are determined by the valency and frequency of the elements in A, B, C other than oxygen, p, q = positive numbers, r = 0 or a positive number, where the ratio p / (q + r) = 20: 1 to 1:20, and in the event that r is a positive number, the ratio q / r = 20: 1 to 1 : 20, which is the proportion [A] _p , in the form of three-dimensionally extended regions A of the chemical composition A: Mo ₁₂ V _a X ¹ _b X ² _c X ³ _d X ⁴ _e X ⁵ _f X ⁶ _g O _x , the proportion [B] ₄ in the form of three-dimensionally extended regions B of the chemical composition B: X ⁷ ₁ Cu _h H _i O _y and the optional portion [C] _r in the form of three-dimensionally extended regions C of the chemical composition C: X ⁸ ₁ Sb _j H _k O _z included, the Regions A, B and optionally C are distributed relative to one another as in a mixture of finely divided A, finely divided B and optionally finely divided C. Method according to one of claims 1 to 17, characterized in that that the thermal treatment in a rotary kiln through which a gas stream flows carried out becomes. A method according to claim 18, characterized in that the rotary kiln is operated discontinuously. Method according to one of claims 18 or 19, characterized in that that at least a subset of the gas stream flowing through the rotary tube led in a circle becomes. Method according to one of claims 18 to 20, characterized in that that the pressure of the gas stream flowing through the rotary tube when leaving of the rotary tube is below the ambient pressure of the rotary tube. Process of heterogeneously catalyzed partial oxidation from acrolein to acrylic acid, characterized in that the catalyst used as an active composition an immediate process product according to any one of claims 1 to 21 has. Process of heterogeneously catalyzed partial oxidation from methacrolein to methacrylic acid, characterized in that the catalyst used as an active composition an immediate process product according to any one of claims 1 to 21 has. Process of heterogeneously catalyzed partial oxidation from propane to acrylic acid, characterized in that the catalyst used as an active composition an immediate process product according to any one of claims 1 to 21 has.