US2790838A - Process for pyrolysis of hydrocarbons - Google Patents

Description

April 3 1957 R. J; sc RApER 2,790,838

PROCESS FOR PYROLYSIS OF HYDROCARBONS Filed Jan. 16, 1952 Fig.1"

74 RobepfJSchrader mmvroa ATTORNEYS 2,790,838 PROCESS FOR PYROLYSISOF rrYnnocARnoNs Robert J. Schrader, Longview, Tex., assignor to Eastman Kodak Company, Rochester, N. Y., a corporation of New Jersey Application January 16, 1952, Serial No. 266,733 8 Claims. (Cl. 260-6'79) The present invention relates to a process for pyrolysis of hydrocarbons for the conversion thereof to hydrocarbons of a higher degree of unsaturation. The invention contemplates the manufacture of mixtures of unsaturated hydrocarbons with predetermined amounts of other gases such as carbon monoxide and hydrogen. More particularly, the invention is concerned with a process adapted to produce by means of thermal cracking in the presence of intensely hot gaseous combustion products formed out of contact with a hydrocarbon feed stock, an efliuent gas having a character determined by the composition of the in-gas and of the combustion products and by the conditions employed. The process of the invention is fitted by change of condition to produce gases relatively rich in acetylene, or to produce gases essentially rich in ethylene or propylene, or other olefins or mixtures thereof. Thus the invention specifically is concerned with a process useful for the manufacture of gas mixtures con taining economically recoverable amounts of acetylene and/or propylene and/or ethylene, etc.

It has been known for some time that a number of the practical difficulties encountered in the thermal conversion of hydrocarbon gas to hydrocarbons of a greater degree of unsaturation can be eliminated if the heat for the reaction is supplied to the feed stock by mixture thereof directly with hot gaseous combustion products. Thus, it has been proposed to manufacture unsaturated hydrocarbons with heat supplied from hot combustion gases produced in a Zone out of contact with the feed stock, heat transfer to the feed stock taking place as a result of direct admixture of the hotcombustion gases therewith.

A procedure of the above described type has been discussed for the cracking of normally liquid hydrocarbons containing at least four carbon atoms to produce diolefines. The procedurecontemplates the steps including (1) the combustion of a mixture of gas and air out of contact with the feed stock, to produce a combustion gas mixture, (2) vaporization and preheating of the feed stock, (3) vigorous mixture of the stock and hot combustion products, promoted by a venturi constriction adjacent the point of introduction of the feed and through which pass the gases from the mixing chamber, ('4) completion of the reaction of the constituents of the mixture in an enlarged reaction space, and (5) finally, quenching of the gaseous effluent from the reaction completion space. In this prior process the combustion products are maintained at less than 1650 C. and the cracking is conducted at a reaction temperature within the range of 704 C. to 927 C, preferably at a temperature no greater than about 871 C. The feed stock is preheated, prior to 'admixture with the hot combustion gases, to a temperature of between about 540 C. and 650 'C., so that a temperature difierential of about 720 C. to about 1110 C. exists between the hot combustion gases and the feed stock at the moment just before the two gas streams are contacted.

Other processes along similar lines have been proposed from time to time. In these other processes, however,

precracking of the feed stock (i. e. heating of the stock to or beyond the point at which the carbon-carbon and carbon-hydrogen linkages begin to rupture) or partial combustion of the feed stock have been suggested either as necessary or most desirabl Usually it has been a common aim of the prior workers to provide means whereby too high temperatures are never reached. Operations at high temperatures have been considered dis-tasteful as being opposed to the production of efiicient results, and the art is filled with studied comment relating to the great desirability of maintaining relatively low temperature levels. For instance, it has been suggested that the combustion gases brought into contact with feed which has not been precracked should be at a temperature no higher than about 1700" C.

It is noteworthy that the art seems also to indicate that the differential between the temperature of the hot combustion gases and the temperature of feed stock which is substantially uncracked and free from products of incipient cracking at the moment immediately before contact of the two should not be excessive, that is, should not be greater than about 1100 C., particularly if moderately high reaction temperatures, e. g. 900 C. or more, are to be maintained. Thus, the art seems to teach that not only should the heating gas temperature be confined to a definite maximum, but the differential between it and the feed stock temperature also should not be allowed to exceed a certain maximum.

A very practical disadvantage of the prior processes is caused by the relatively enormous quantities of heating gases required to supply the requisite amount of cracking heat at the temperatures employed. The large percentage of undesirable constituents, i. e. combustion products, in the resulting efiiuent gases therefore makes separation and recovery of the product unsaturates a burdensome and uneconomical task. Another practical disadvantage of the known processes, even where the cracking heat is supplied by substantially oxygen-free combustion products formed out of contact with the feed stock, is carbon formation and deposition within the apparatus.

1 have discovered a method capable of producing vastly improved and commercially feasible results by developing and continuously applying to feed stock substantially free of products of incipient cracking heating gases at temperatures in ranges Well above the ranges heretofore employed or even contemplated. I have found that, in contradiction to suggestions of the prior art, it is possible to obtain exceptionally efiicient results by impressing excessive thermal shock upon the feed stock by operating in new high temperature ranges under the following three conditions: (a) radically high combustion gas temperatures, (l2) extremely high temperature differentials between feedstock and heating gases and (c) instantaneous blending of the feed stock with the ultra-hot combustion gases. I have found it unexpectedly beneficial to maintain together with instantaneous blending excessive differentials of temperature between extremely hot combustion gases and relatively cold feed stock, these dilierentials being of the'order of over 1100 C. to 2900 C. or more, whereby a condition exists which might be identified as thermal shock. The discovery of these advantageous differentials is all the more interesting when it is considered that the difierentials have been found most effective when employed in conjunction with extremely high combustion gas temperatures, moderately high reaction temperatures, absence of any substantial combustion of the feed stock, and avoidance of any substantial amount of incipient cracking in the feed stock fed to the reaction. Achievement of thermal shock is dependent not only upon high temperatures and high temperature differentials, but

3 also upon instantaneous blending of the feed stock with the heating gases.

It appears that the possibility of process capable of continuously producing and utilizing combustion gases at temperatures in the range of 1800 C. to 2900 C. and greater has never been appreciated. I now have developed such a process and have found that operations under the conditions of the invention, including a fast rate of flow of the gases, vigorous mixing and reaction times of short duration are endowed with valuable traits as respects efficiency and percentage of yield. I have also discovered that these procedures have an entirely unexpected versatility in that they are capable of producing a variety of products merely as a result of shifting the substances employed and of shifting the reaction conditions within the new advantageous ranges employed. Thus I am able to manufacture from saturated hydrocarbon feed stocks gaseous etfluents rich in acetylene or rich in olefins such as ethylene and propylene, or rich in a mixture of components comprising a synthesis gas, i. e. olefin or olefins, carbon monoxide and hydrogen.

In my new method, combustion gases atuniform temperatures of 1800 C. and greater, preferably in the range of 2200 C. to 2900 C. are developed and directly applied to relatively cold feed stocks without any substantial combustion of the latter. The heating gases are suddenly and furiously mixed with the feed stock to form a uniformly blended reaction mixture having a resulting temperature, i. e. reaction temperature in the range of 800 C. to 1500 C., and the reaction products are quickly quenched, when necessary, after formation during rapid passage through mixing and reaction completion zones. The invention contemplates utilization in critical portions of the apparatus of a special material capable of withstanding the extremely high temperatures sustained over long periods of time and having no detrimental influence on the reactants. The material possibly may have a bene ficial influence on the reactants under the existing conditions.

It is an object of the present invention to provide a process of the type generally described above in which any gaseous fuel may be employed to produce the requisite hot combustion products, the fuel not being limited to the same hydrocarbon as that comprising the feed stock. It is a further object to provide a process in which the duration of the conversion reaction is in the range of a small fraction of a second to one second, and to provide a process in which the feed stock is not recycled and in which preheating and precracking need not occur prior Y to the principal reaction. In other words, it is an object to secure a process in which a single pass of the hydrocarbon feed stock through the reaction zone sufiices to produce the desired products. Still another object is provision of a process as described above in which changes in the substances fed to the apparatus and/ or minor alterations of conditions serve to produce various types of products.

A fundamental object of the invention is the provision of means whereby direct admixture with a relatively cold and vulnerable feed stock of hot combustion gases maintained at temperatures of and greater than 1800 C. and up to 2900" C. and more can be employed. Another object, consequently is the provision of a means for obtaining and for introducing directly into relatively cold feed stock hot combustion gases continuously maintained at uniform temperatures greater than 1800" C. whereby sudden application of heat to the feed stock at a temperature differential of 1100 C. to 2900 C. and more may be accomplished. It is a further object to provide means for moving gases through a cracking zone of the type described at very high velocities, whereby the advantageous high temperatures can be employed. Accordingly, another obiect is to provide a means capable of producing an instantaneous and homogeneous mixture of gaseous feed stock and gaseous hot combustion products whereby advantageous high velocity flow may be maintained and whereby localized underheating or overheating of the stock may be avoided. Still another object is to conduct a cracking reaction of the type described in which the feed stock is exposed to no substantial amount of oxygen and in which therefore there will be little or no oxidation or combustion of the feed stock. Still other objects will be obvious from the present disclosure.

In keeping with the objects, the invention is founded upon the discovery that a continuous uniform high temperature developed in a heating gas within a combustion zone fabricated of an ultra-high temperature refractory such as stabilized zirconia or thoria suffices upon admixture of the heating gas with a stream of relatively cold hydrocarbon feed stock to supply the shock and heat necessary for proper conversion when thorough and furious mixture of two streams is made to occur instantaneously in a confined refractory mixing zone having a constricted flow promoting outlet, the mixture then being allowed to react at a limited moderately high temperature in a further zone for a fraction of a second or slightly longer and being subsequently immediately quenched. In conformity with the discovery, the apparatus comprises an elongated reaction chamber having at one end a combustion furnace, at the opposite end a quenching zone and having a confined mixing zone, a venturi or equivalent restricted flow-promoting outlet from the mixing zone, and a reaction completion zone situated in order between the ends. The combustion furnace is adapted to exhaust a stream of products at temperatures of l800-2900 C. and greater into the confined mixing zone at the mouth of the venturi throat. Feed stock is continuously discharged into the mixing zone, mixing being facilitated by means of the venturi constriction comprising an outlet through which the products of the mixture must pass from the mixing zone prior to entering the reaction completion zone and subsequently the quenching zone from which the products are finally withdrawn.

A full appreciation of the critical features of the procedure and apparatus is necessary for a true understanding of the invention. It is believed that this appreciation will be obtained more easily from the description below if the latter is studied with the following points in mind:

1. Operation with combustion gases at a high temperature within a range heretofore distasteful to the art is essential to achievement of the efficient cracking contemplated by the invention. The temperatures employed must be in the range of (a) 1800 C. to 2900 C. or more for the combustion gases exhausting from the furnace, and (b) about 800 C. to 1500 C. for the gas mixture issuing from the venturi constriction. The upper temperature, given as 2900" C. or more is approximate since the measurement of temperatures of this magnitude is difficult and may be inaccurate. Additionally it is understood that operations at even higher temperatures than those specified, where possible, are within the spirit of the invention when they are otherwise in accord with its teaching.

2. Operations must be conducted with ultra-high tem perature differentials existing between the hot gaseous combustion products and the feed stock. Thus, the differentials existing at the moment just preceding contact of the two gas streams should be in the range of about 1100" C. to about 2900 C. Although I am not cert-ain of the reaction mechanics induced by these high temperature differentials, it appears that some effect which might be termed thermal shock is influential in producing the desired cracking. While the extremely high temperature of the heating gases employed effectively serves to reduce correspondingly the amount of heating gas required and thereby simplifies the problem of separation of combustion products from the desired unsaturates which are produced, the so-called thermal shock resulting from the excessive temperature differentials is believed to have an effect to some extent .analogou's'to catalysis of the reaction.

3. Operation must be directed to maintenance of reaction times of very short duration. That is, under certain conditions the feed stock must not be allowed to remain at the high temperatures developed for more than a fraction of a second, the critical reaction period limits being about 0.0001 second to about 1 second depending upon other conditions as discussed more fully below. Maximum temperatures being of the essence, limitation of the reaction period is requisite to avoidance of overcracking and elimination of undesirable reactions. The thermal shock effect referred to above is believed to make possible the maintenance of these required conditions. Normally it is advantageous to maintain reaction times of (a) 0.001 to 0.05 second for a product high in acetylene, (b) 0.02 to 0.3 second or longer for a product high in ethylene, and (c) 0.1 to 1.0 second or longer for a product rich in a mixture comprising oxo process synthesis gas constituents. In some instances, particularly in the production of ethylene and synthesis gas, the cracking process can be self-quenching, that is, the 'heat absorbed by the endothermic cracking reactions lowers the temperature of the reaction mixture to the point where no further cracking will take place.

4. Blending of the intensely hot combustion products with the feed stock must be both thorough and instantaneous. This is necessary to avoid localized underheating and overheating of the feed stock and to facilitate short reaction periods. Obviously it is also necessary to capitalize on the temperature differential effect. -I believe that sudden and instantaneous blending of the relatively cool feed stock with the excessively hot combustion products is one of the primary causes of such thermal shock as results in the feed stock.

5. The venturi constriction must be positioned nea to both the combustion furnace exhaust port and the feed stock inlet port whereby the gaseous mixture may be shot through the constriction immediately upon formation. A venturi or its equivalent functions as a flowpromoting constriction joining the mixing zone with the reaction completion zone.

6. The combustion furnace and mixing chamber should be fabricated of thoria or a stabilized zirconia. A significant discovery forming one basis of the invention is the unexpected utility of these refractories. Stabilized zirconia is operative as a furnace wall material at temperatures up to 2600 C. and thoria will serve in the same capacity at temperatures, it is believed, of up to 2900 C. r

The zirconia refractory is advantageous also because of its extremely low thermal conductivity, which allows for the use of much thinner wall sections "in the furnace for a given outside wall temperature. Of equal or more significance, zirconia appears to inhibit the formation of carbon on structural parts of which it is composed. Where combustion gas temperatures are not to be within the most advantageous temperature levels of over 2200 C., but are to be in the range of l800 C. to 29.00" C., more common refractory materials such as magnesia, alumina, and silicon-carbide may be employed.

7. The gaseous reactants entering the apparatus must be passed through at high velocities in order to meet the conditions above. These velocities must be within the range of '(a) 200 ft. per minute to the speed of sound under the existing conditions, but advantageously are about 500 ft./sec. for the combustion gases exhausting from the furnace, and (11) equal to or somewhat less than the above for the gases issuing from the venturi orifice;

8. There need not be any precracking of the feed stock, that is, no constituent of the feed stock need be in a state of incipient cracking, and the stock need not be preheated to as much as 800 C.

9. Partial oxidation or combustion of the feed stock should be avoided as far as possible.

.The apparatus of the invention is illustrated in the accompanying drawings in which:

Fig. 1 is a longitudinal vertical section through a reaction chamber, schematically shown,

Fig. 2 is a transverse section taken on the line 22 of Fig. 1,

Fig. 3 is a transverse section on Fig. 1,

Fig. 4 is a longitudinal vertical section through a portion of another form of reaction chamber shown schematically, and,

Fig. 5 is avertical longitudinal section through a portion of still another form of reaction chamber shown schematically.

Referring to the drawings, in Fig. l, the reaction chamber having a shell 17 is lined with a refractory ceramic-lining wall 1'8 and contains at about its midpoint a body 24 forming a venturi constriction. At one end of the reaction chamber is disposed a combustion furnace having side walls 21 of thoria or stabilized zirconia refractory material. In an end wall of the same material is located a burner 11. "Fuel is supplied to the burner through a line 12, and lines are also provided for steam 1'4 and oxygen 13.

The combustion furnace advantageously is cylindrical in shape and is tapered at its outer end to provide an exhaust port 22, the material surrounding which also comprises thoria or stabilized zirconia. The furnace is spaced from the walls of the reaction chamber and supported 'by means of ceramic supporting members 33 whereby annular channels 19 for passage of feed stock lead between the walls of the combustion furnace and the reaction chamber. The supporting members extend substantially the full length of the furnace. 'Stock inlet passages 16 communicate with the stock channels 19 whereby feed stock can be introduced to the reaction chamber from the exterior thereof, and flange 1'5 is so maintained that the passages 16 are provided. A reaction completion zone, designated by the numeral 25, is located adjacent the venturi constriction formed by body 24 near the center of the reaction chamber. At the opposite end of the chamber is provided a quenching zone, designated by the numeral 26, in which are positioned coolant spray nozzles 28, product withdrawal outlet 30, coolant withdrawal valve 32 and coolant supply lines 31. The venturi body 24 and the reaction chamber lining 18 in the vicinity of the combustion gas exhaust port are fabricated of any suitable refractory material.

The apparatus of Fig. 4 is modified to allow for a the line 3--3 of different type of hydrocarbon inlet passage, and comprises a reaction chamber shell 48, ceramic lining wall 55, venturi body 54, feed stock inlet passage terminating in stock ports 53, refractory furnace having side walls 50, exhaust port 52, burner d7, fuel line 44, oxygen line 45, diluent line 46, and ceramic supporting members (not shown). The inlet point of the venturi is designated by the numeral 56.

In the further modification of Fig. 5, the combustion end of a reaction chamber supports a combustion furnace having a side wall 74, burner 72, fuel line 59, oxygen line and diluent line 71. A ceramic lining is provided for shell 76 of the reaction chamber adjacent venturi body 77 which has a throat '79. Passages for the introduction of feed stock terminate in stock ports 80 and the furnace has a combustion products exhaust port 83.

The apparatus of Fig. 1 is employed for accomplishmerit of the process as follows:

High temperature gases are generated in the furnace by combustion of the fuel and oxygen-containing gas, with the addition of a diluent such as steam, if desired. Combustion gases are formed to issue at a temperature in the range of 1800 C. to 2900 C. or more preferably 2200 C. to 2900" C. at a high rate of speed frorn' the furnace exhaust port and immediately upon issuance mix with feed stock passing into the reaction chamber through the inlets 16 and feed stock channels 19. The relatively cold feed stock is presented to the intensely hot combustion gases and subjected to what I have termed thermal shock at a point immediately adjacent to the venturi throat, into which the combustion gases are continually directed. The venturi constriction achieves turbulence and rapid and vigorous mixing of the gases fed therethrough and the mixture is forced through the venturi throat prior to reaching the reaction completion zone. After passage through the reaction completion zone, the eiiluent gases reach the quench chamber whereupon they are contacted with the spray of fluid coolant and subsequently the cooled products are withdrawn through the product out-let 30, the coolant falling to the lower Zone of the quenching chamber and being Withdrawn along with any solid by-products through the valve 32.

In the modification of Fig. 4 the feed stock is fed into the reaction chamber in a direction perpendicular to the longitudinal axis of the reaction chamber at a point immediately adjacent to the fore part of the venturi constriction. The arrangementof Fig. 5 provides for entry of the feed stock into the combustion gas stream at substantially the center part of the throat of the venturi constriction. The apparatus of Figs. 4 and 5 differs from that of Fig. l primarily in the point of introduction of the feed stock and also in that the feed stock is introduced in a direction perpendicular to the line of flow of the hot combustion gas, whereas in Fig. l the feed stock is introduced more or less tangent to the line of flow of combustion products. In any event, the feed stock is always introduced at a'point which is immediately adjacent to the venturi constriction and closely positioned to the furnace exhaust port, "since the latter also is always immediately adjacent to the venturi constriction.

The feed stock is a hydrocarbon or mixture of hydrocarbons having a lesser degree of unsaturation than the desired product and preferably normally gaseous hydrocarbon feed stock is used. However, the feed stock may be a hydrocarbon liquid capable of being vaporized. Suitable feed stock components are methane, ethane, propane and other of the lower saturated aliphatics, natural gasoline. kerosene, ethylene, propylene and other unsaturated aliphatics. Benzene, substituted benzenes, cyclic saturated hydrocarbons, cyclic olefins, etc., may be cracked without difficulty but usually prove uneconomical except when in petroleum mixtures such as gasolines and naphthas. Additionally, non-vaporizable liquid hydrocarbons may be cracked by the process upon being introduced in liquid form. Thus, heavy oils and the like can be cracked, but should be introduced in the form of small droplets preferably carried in a stream of diluent gas. It should be noted that where a liphatics are concerned, methane is the most difficult hydrocarbon to crack, usually necessitating the establishment of conditions which will result in acetylene as the principal unsaturated product. The longer the chain, the easier the cracking becomes. To the feed stock, which would be non-acetylenic when acetylene is desired and which would be non-ethylenic when ethylene is desired, a diluent such as steam may be added if desired. The feed may be preheated if desirable, but need not be heated to the point where cracking occurs, although the process will function on some hydrocarbons where precracking has been accomplished. It should be noted that Where preheating is kept within the limits outlined, it is highly advantageous, since it serves to reduce the amount of combustion products necessary to supply the heat required for cracking and thereby further simplifies the final problem of product separation and recovery.

Any hydrocarbon fuel will suffice for producing the In other words, gases, liquids, or

combustion gases.

solids may be employed, but gaseous fuels are most ad vantageous. Natural gas particularly makes an excellent fuel, although hydrogen may be used in whole or in part. The hydrocarbon by-products of the present process, i. e. the efiluent gases from which the unsaturates have been removed, constitute a fuel which is excellent because of economy and convenience.

The combustion supporting gas may be any such as would normally be used for the same purpose, and generally will be air or pure oxygen or a mixture of the two. Insofar as proper quantity of the combustion supporting gas is concerned, satisfactory results will be produced if no more than the stoichiometrical quantity is used. In any event, no more than enough for complete combustion should be supplied, and it is in keeping with the concept of the invention that no substantial amount of oxygen be available within the reaction chamber to cause oxidation or partial combustion of the stock.

Of course, a certain amount of uncombined oxygen is always present in the reaction mixture as a result of the dissociation of the carbon dioxide and water formed during combustion, due to the high temperatures occurring, particularly Where the combustion products are maintained at 2590" C. or more. This is true even where less than stoichiometrical amount of oxygen is supplied to the furnace. However, the amount of uncombined oxygen from this source is not of sufficient extent to be detrimental to the reaction, and generally comprises less than 10% by volume of the combustion gases exhausting from the furnace. Generally, somewhat less than the theoretical amount of the combustion supporting gas is supplied, e. g., only 30 percent of the theoretical amount is necessary if proper temperatures are maintained. Where synthesis gas is the desired product, appropriate adjustment of the oxygen to fuel ratio results in adjustment of the ratio of the products hydrogen, carbon monoxide and ethylene.

As stated above, a diluent may be added to the feed stock. It is also generally appropriate to introduce a diluent to the combustion chamber although none is necessary. The most convenient diluent, of course, is steam, but carbon dioxide or nitrogen or other inert gas may be employed. An optimum efficiency in the furnace can be obtained by adding diluent or by adjusting the ratio of oxygen to fuel.

The term reaction temperature as used herein refers to the temperature of the gas stream as recorded at the downstream end of the venturi constriction as the reaction gas mixture exits from the latter. Actually, the proper time for measurement of the real reaction temperature would be at the instant blending of the intensely hot combustion gases with the relatively cold feed stock has been completed and temperature equilibrium has been reached but before any reaction of the gases themselves. Such a reading, if possible, would of course indicate the highest temperature to which the feed stock is raised. However, since there is no such time or point in the process of the invention, due to the fact that cracking takes place in the feed simultaneously with the temperature increase thereof, and further, since the cracking is itself an endothermic reaction, it is impossible to obtain in the gas stream a temperature reading of any considerable accuracy prior to the time the stream passes the vicinity of about the midpoint of the venturi constriction.

In any event, the reaction temperatures as measured at the downstream side of the venturi constriction must be maintained in the range of 800 C. to 1500 C. in accordance with the invention. Of course, the specific temperatures to be used are dependent upon the par ticular reaction desired, the reaction time to be established and upon the other conditions of operation. However, it may be stated that the feed stock temperature together with the corresponding combustion gas temperature which is necessary to give the proper temperature menses differential in accordance with practice of the invention will dictate the relative rates of 'flow of the .two gas streams. These rates of flow, which are of course gov erned to a certain extent also by the nature of the specific gases involved should be such as to provide reaction temperatures of above 800 Czand not more than about 1500 C. whereby to provide economical operation with high yield in accordance with the teaching of the invention. Where acetylene is'desired, the most advantageous combustion gas temperature range has a minimum of 2l00 C. and extends up to 2900 C. or above; for the production of synthesis gas the most advantageous combustion gas temperature range is lower.

Ethylene should be produced at a reaction temperature of from 800 C. to 1000 C. on the down stream side of the venturi, while a reaction temperature of at least about 1000 C. is advantageous for the production of acetylene, but it is to be noted that ultra-high temperature dilferentials, made possible by ultra-high combustion gas temperatures, are necessary in any event for economical cracking in accordance with the concept of the invention. in view of the fact that combustion gas temperatures of above 1800 C. are maintained, there must be no impediment to the flow of gases through the reaction chamber. Such impediments would create calm areas where abnormally long reaction times would prevail. Obviously, the temperature at various points in the apparatus must be maintained below the sintering point of the particular refractories used at those points.

The feed stock may be introduced with a temperature as low as room temperature. If it 'is preheated in order to promote economical operation, it generally will be introduced at about 500 C. to 700 C. Preheating of the fuel, combustion supportinggas, diluent (if used), and feed stock may be carried out if desirable, but preheating of none of these materials is necessary.

Pressure requirements for the conduct of the process have not been determined precisely. However, it has been established that good results may be obtained from a reduction in the partial pressure of the charge. This reduction may be accomplished by adding diluents to the furnace and/ or the feed stock rather than by applying a vacuum. As a matter of fact, the hot gases effectivcly will reduce the partial pressure of the feed stock.

The essential features of the mixing step, that is, the blending of the stream of hot gaseous products of combustion with the feed stock stream have been briefly described above. The feed stock may be introduced under pressure, but generally the combustion gases issue from the furnace exhaust port at such speeds that an aspirating effect may be achieved stock gases. In any event, the angular convergence of the feed stock stream with the stream of hot gases is such that proper blending and complete mixture results from the turbulence produced. The spaced relationship of the furnace exhaust port, feed stock inlets and venturi is critical to complete mixing under high rates of flow The hot combustion products must issue as a forceful jet.

The importance of the venturi constriction, or equivalent, cannot be overemphasized. It achieves an increase in the rate of flow of the gases and in so doing, assists in complete mixture either at a point adjacent to the venturi throat or Within the throat of the venturi itself. It does not appear necessary, however, that the venturi have the exact conformation illustrated in the drawing, and other means to achieve the same effect can be employed, e. g., constriction means which Will produce turbulence without excessive pressure restrictions. The venturi device functions quite differently from the opposed flow suggested in the prior art, however, and it is a requisite that no venturi or equivalent baffle arrangements be .used which severely impede flow of the mixture of gases or tend to promote formation of quiesient regions.

Some cracking reactions are self-quenching. These,

to draw in the feed of course, may be allowed a longer contact time without detriment. However, positive cooling or quenching means normally is used :to great advantage. A means for cooling preferably is employed, such as heat exchangers, etc., but .the most efficient means appears to comprise shock cooling by the application of liquid or fluid coolants. Normally water or steam is employed. The fluid coolant, if liquid, has the additional function of removing solid particles from the gaseous effluent. Thus, carbon and tarry by-products, most of which are valuable, may be recovered from the coolant. The quenching zone itself is formed by a continuation of the side wall 17 of the reaction chamber, but in view of the lower temperatures prevailing therein, need not be lined with refractory. The quencher advantageously may be composed of stainless steel.

The various products which may be obtained are illustrated in the examples given below in which the minor amounts of by-products will be noted. Subsequent to quenching, the gaseous efliuent is subjected to any suitable procedure for separation of the desired constituents. As to the principal products resulting, when a feed stock of aliphatic material containing a double bond is used, the resulting products will be ethylene, hydrogen and carbon monoxide. Where normal butylene is introduced as the feed stock, the process produces ethylene, propylene, hydrogen and carbon monoxide.

The reaction chamber should be a gas-tight unit suitable for operation under either pressure or vacuum. The side walls of the reaction chamber, at least in the forward part thereof (adjacent furnace, mixing zone, venturi and reaction completion zone) are advantageously made cylindrical in shape in 'keeping with the desire to produce 'a smooth flowing gas stream. The side wall lin ing is composed of suitable refractory ceramics.

The stock inlet ports formed by the inner terminus of passages 19 in the apparatus of Fig. l and designated in Figs. 4 and 5 by the numerals 53 and 80, respectively which are seated adjacent to the periphery of the inlet wall or adjacent or within the throat of the venturi refractory as illustrated in the various figures, normally laterally or equi-distantly spaced, are preferably about 6 in number. The flange 15 is an auxiliary part of the outer construction and may be constructed of any suitable material such as stainless steel. The ceramic supporting members 33 should extend the full length of channel 19 and may be composed of any of the refractory materials listed above.

The walls of the furnace are made of thoria or stabilized zirconia in order to achieve the results outlined above.

The burner, because of the lesser temperatures to which it is subjected, may be composed of stainless steel, inconel, or any other suitable metal. Obviously, flow meters, valves, gauges, temperature recorders, heat exchangers, etc. may be employed.

The zirconia refractory material which has been found to be highly advantageous to operation of the presently disclosed process when employed in various parts of the apparatus as described above is a zirconia composition containing a stabilizing material such as calcium. One composition used with success consisted of a calciumstabilized zirconia such as that manufactured by the Norton Company. This material is described in the following tWo publications:

1. Electric furnace fusion and purification of zirconia, by Douglas W. Marshall, Brick and Clay Record, vol. 1l8,No.6,p.62, 1951.

2. Stabilized zirconia, a pure oxide refractory, by Lowell H. Milligan, Brick and Clay Record, vol. 118, No.5, p. 52, 1951.

The invention is further illustrated in the following examples in which the rates of How of gases are expressed in terms of cubic feet per minute at 0 C. and 760 of mercury, and the conversions are calculated on the 1 carbon content, the gas compositions being given in terms of volume of dry gas:

Example 1 In an apparatus of the general arrangement shown in Fig. 4 with a combustion furnace 7 inches in length and 2 inches in internal diameter fabricated of stabilized zirconia, and with a reaction chamber 7 /2 inches in length and 4 inches in diameter equipped with a venturi type construction 6 inches in length with a throat of inches in diameter, 3.23 cubic feet per minute of methane and 1.5 cubic feet per minute of steam were reacted with a combustion gas produced by 0.825 cubic feet per minute of propane and 3.35 cubic feet per minute of oxygen in the presence of 1.6 cubic feet per minute of steam. The reactant methane and steam were preheated to 465 C. Gaseous products were issued from the reaction chamber at 8.97 cubic feet per minute and were immediately quenched with water. These products consistedof 3.6 percent acetylene, 0.8 percent ethylene, 42.4 percent hydrogen, 17.8 percent methane and the remainder essentially products of combustion. The conversions calculated on the methane feed stock were 20 percent to acetylene and 4.4 percent to ethylene with 49.5 percent unreacted methane. There was also 5.6 percent conversion to carbon. In this example, the combustion gases employed in the reaction were at a temperature in the range of 2400 C. to 2600 C.

Example 2 In an apparatus of the general arrangement shown in Fig. 1 with a combustion furnace 7 inches long and 2 inches in internal diameter fabricated of zirconia and containing an outlet passage inch in diameter, and with a reaction chamber 13 inches in length equipped with a venturi of 4 inches in length containing a 1 inch throat, 3.45 cubic feet per minute of methane were continuously pyrolyzed to give conversions of 23.3 percent to acetylene, 2.4 percent to ethylene, 1.8 percent to carbon, and 39.1 percent to unreacted methane. The combustion gas used to bring about this pyrolysis was produced by 0.84 cubic feet per minute of propane and 3.7 cubic feet per minute of oxygen. Diluent steam for the methane amounted to 1.04 cubic feet per minute while furnace steam amounted to 3.15 cubic feet per minute. The methane and steam entering the reaction chamber were preheated to 525 C.

The effiuent gas from the reactor was immediately.

quenched with water. This gas rate was 10.3 cubic feet per minute with a concentration of acetylene of 3.9 percent, a concentration of ethylene of 0.4 percent, a concentration of hydrogen of 44.9 percent and a concentration of unreacted methane of 13.1 percent. In this example the combustion gases employed in the reaction were in the range of about 2400 to 2600 C.

Example 3 Ethane was continuously pyrolyzed in an apparatus similar to that shown in Fig. 1 of the following dimenthe stabilized zirconia furnace was 2 inches in internal diameter, 7 incheslong, with a /2 inch diameter outlet orifice; the reaction chamber was 5 inches in internal diameter, 8% inches in length, equipped with a venturi 6 inches in length with a 1-inch throat. The ethane was introduced at the rate of 2.8 cubic feet per minute in the absence of dilution steam while the combustion gas was produced by burning 0.71 cubic feet per minute of propane with 3.5 cubic feet per minte of oxygen in the presence of 2.4 cubic feet per minute of steam. In this example the ethane was preheated to 475 C. while the fuel, oxygen, and steam supplied to the furnace were not preheated. Quenching of efiluents from the reaction chamber was carried out using steam. The temperature at the downstream end of the venturi using these conditions was 1150 C. and the ofi-gas temperature after steam quenching was 565 C. The ofi-gas analysis was 8.4 percent acetylene, 3.7 percentethylene, 47,2 percent Example 4 With an arrangement generally similar to that shown in Fig. 4, ethane was continuously pyrolyzed. The dimensions of the equipment were as follows: zirconia furnace, 7 inches in length, 2 inches in diameter; stabilized zirconia venturi, 2% inches in length, 4 inch throat; reaction chamber 20 inches in length, and 1 inch in diameter. The fuel for combustion in this case was propane fed at the rate of 0.52 cubic feet per minute while the combustion was supported by 11.0 cubic feet per minute of air preheated to 500 C. No diluent was added to the furnace. The ethane was admitted to the reaction chamber at the rate of 1.90 cubic feet per minute along with dilution steam added at the rate of 1.55 cubic feet per minute. These were preheated to 450 C. Water was used to quench the efiluents which issued from the reaction chamber at a rate of 14.25 cubic feet per minute. The concentration by volume of products in the gas stream was as follows: acetylene4.3 percent, ethylene-4.6 percent, propylene-0.2 percent, hydrogen- 15.6 percent, methane-4.6 percent, ethane-nonc, nitrogen-58.9 percent, combustion products--remainder. The conversion of ethane was as follows: acetyIene-32.2 percent, ethylene-34.4 percent, methane-47.2 percent, carbon11.3 percent and combustion products2.7 percent. In this example the combustion gases employed in the reaction were in the range of about 2050 to 2150 C.

Example 5 In an apparatus similar to that used in Example 3 in design and dimensions, ethane was pyrolzed to give primarily ethylene as follows: 3.22 cubic feet per minute of ethane in the presence of 2.0 cubic feet per minute of dilution steam were pyrolzed with combustion gases produced by burning 0.55 cubic feet per minute of propane with 2.02 cubic feet per minute of oxygen in the presence of 1.25 cubic feet per minute of burner steam. The ethane and dilution steam were preheated to 565 C. while none of the streams fed to the furnace were preheated. With these conditions, the temperature measured l 17.8 percent ethylene, 1 percent propylene, 0.2 percent on the downstream side of the venturi was 875 C. The off-gas rate was 8.03 cubic feet per minute. The effluents were not cooled but issued from the reaction chamber at 685 C. The effluents analyzed 2.4 percent acetylene,

condensables at 40 C., 0.4 percent oxygen, 36.1 percent hydrogen, 13.8 percent methane, 4.8 percent ethane, 7.0 percent carbon dioxide, 15.4 percent carbon monoxide and 1.1 percent nitrogen. The conversion of ethane was 6.0 percent to acetylene, 44.5 percent to ethylene, 17.1

percent to methane, 13.7 percent to carbon, and 2.2 percent to combustion products. In this example, the combustion products were at a temperature range of about 2375 to 2525 C.

Example 6 In an apparatus similar to that shown in Fig. 4, hot

combustion gases were produced from 4.3 cubic feet per minute of hydrogen oxidized by 212 cubic feet per min- I ute of oxygen in the presence of 9.0 cubic feet per minute for each pound of propane. pyrolyzed were acetylene- 13 0.28 pound, ethylene-0.29 pound and propylene-0.016 pound. In this example the combustion gases employed in the reaction were above 2400 C.

Example 7 In an apparatus of the general appearance of that shown in Fig. 5, with a combustion furnace 18 inches in length, and 6 inches in internal diameter fabricated of stabilized zirconia, and with a reaction chamber 18 inches in length with a venturi type constriction 3 /2 inches in length with a 2 /2 inch throat, propane was pyrolyzed to give high yields of acetylene and ethylene. The hot combustion gases were produced by burning 9.7 cubic feet per minute of propane with 43.4 cubic feet per minute of oxygen in the presence of 124 cubic feet per minute of steam. The propane to be cracked was introduced into the reaction chamber at the throat of the venturi at the rate of 26.8 cubic feet per minute in the presence of 49.5 cubic feet per minute of steam. All gas streams entering the furnace were preheated to 600 C. and the reactant gas stream entering the reaction chamber was preheated to 600 C. The products issuing from the reaction chamber were immediately coolcd with water. The effluent stream analyzed 8.8 percent acetylene, 9.4 percent ethylene, 0.2 percent propylene, 13 percent methaue, and 38.7 percent hydrogen. The remainder was essentially products of combustion. For each pound of propane pyrolyzed the following weights of unsaturated materials were produced: Acetylene-0.25 8 pound, ethylene--0.297 pound, and propylene-00095 pound. The combustion gases employed in the reaction in this example were in the range of 20752150 C.

Example 8 Using similar equipment and reactants to those described in Example 7 and only altering the feed rates, even higher yields of unsaturated compounds were made. To the furnace for combustion was fed 7.8 cubic feet per minute of propane, 29.0 cubic feet per minute of oxygen, and 97 cubic feet per minute of steam. The reactant hydrocarbon gas stream consisted of 16.1 cubic feet per minute of propane and 30.0 cubic feet per minute of steam. The products issuing from the reaction chamber analyzed 7.4 percent acetylene, 9.6 percent ethylene, 0.6 percent propylene, 13.0 percent methane, and 40.7 percent hydrogen. The remainder was essentially products of combustion. For each pound of propane pyrolyzed under these conditions, 0.244 pound of acetylene, 0.342 pound of ethylene and 0.031 pound of propylene were produced. In this example the combustion gases employed in the reaction were at about in the range of 1970 to 2080 C.

Example 9 In an apparatus of the type shown in Fig. 1 propane was pyrolyzed by means of hot combustion gases produced by burning 2.2 cubic feet per minute of methane with 2.77 cubic feet per minute of oxygen in the presence of 2.3 cubic feet per minute of steam. The propane was introduced to the reaction chamber at the rate of 2.09 cubic feet per minute along with 3.4 cubic feet per minute of dilution steam. The cracking stock stream was preheated to 390 C. while the gas streams to the furnace were not preheated. The efliuent gas from the reaction chamber analyzed 6.4 percent acetylene, 9.4 percent ethylene, 2.0 percent propylene, 9.0 percent ethane, 9.8 percent methane, 34.9 percent hydrogen, 9.3 percent carbon dioxide, 17.8 percent carbon monoxide, 0.4 percent oxygen and 1.0 percent nitrogen. For each pound pyrolyzed, 0.146 pound of acetylene, 0.231 pound of ethylene and 0.074 pound of propylene were produced. In this example, the combustion gases employed in the reaction were above 2000 C.

14 Example 10 In an apparatus arrangement of the dimensions and design used in Example 4, hot combustion gases were produced using 0.52 cubic feet per minute of propane and 11.0 cubic feet per minute of air in the absence of any added diluent. The air and fuel were preheated to 502 C. prior to combustion. The cracking stock fed to the reaction chamber was natural gasoline of and of average formula Carl-111.4, fed at the rate 81 cubic centimeters per minute (room temperature) and preheated to 350 C. before introduction. Steam diluent was added along with natural gasoline at the rate of 3 cubic feet per minute. The hot effluent gases from the reaction chamber were cooled with water. This gas stream was produced at the rate of 13.4 cubic feet per minute and had the following analysis: 4.0 percent acetylene, 2.5 percent ethylene, 0.2 percent propylene, 11.7 percent hydrogen, 4.2 percent methane, 64 percent nitrogen, and remainder were combustion products. This analysis con responded to conversions of the natural gasoline of 37.9 percent to acetylene and 23.7 percent to ethylene. The conversion to carbon was 10.9 percent. In this example the combustion gases employed in the reaction were in the range of about 2050 to 2150 C.

Example 11 Using the same fuel and cracking stock in the same apparatus as in Example 10, but altering conditions of temperature and feed rates a higher yield of ethylene and a lower yield of acetylene was produced. The combustion gas was produced from 0.462 cubic feet per minute of propane burned with 11.0 cubic feet per minute of air. The preheat temperature of these streams was 475 C. The natural gasoline was introduced to the reaction chamber at the rate of cubic centimeters per minute (room temperature) in the presence of 3.0 cubic centimeters per minute of steam. These streams were preheated to 320 C. The reaction products were produced at the rate of 13.8 cubic feet per minute and were cooled with water. These analyzed 4.0 percent acetylene, 6.9 percent ethylene, 9.9 percent hydrogen, 5.8 percent methane, 0.2 percent propylene, 60.8 percent nitrogen and remainder combustion products. The conversion of the natural gasoline amounted to 22.7 percent to acetylene and 39.1 percent to ethylene. The conversion to carbon was 14.5 percent. The combustion gases employed in the reaction in this example Were in the range of about 2100 C. to 2200 C.

Example 12 In equipment of the type shown in Fig. 1, natural gasoline as used in Example 10 was pyrolyzed to give good yields of acetylene, ethylene, and propylene. The combustion gases were produced by oxidizing 0.905 cubic feet per minute of propane with 3.87 cubic feet per minute of oxygen in the presence of 4 cubic feet per minute of steam. The natural gasoline was introduced at the rate of 335 cubic centimeters per minute and preheated to 600 C. in the presence of 5.45 cubic feet per minute of steam. The oxygen introduced to the furnace was preheated to 570 C. while the fuel fed to the furnace was preheated to 545 C. Water was used as a quenching agent. The effiuent gas analyzed 9.6 percent acetylene, 12.0 percent ethylene, 0.8 percent propylene, 14.2 percent methane, 33.7 percent hydrogen, 0.2 percent oxygen, 1.5 percent nitrogen, 10.2 percent carbon dioxide and 17.8 percent carbon monoxide. The pounds of unsaturated hydrocarbons produced per pound of natural gasoline cracked were as follows: 0.23 pound of acetylene, 0.31 pound of ethylene, and 0.031 pound of propylene. In this example, the combustion gases employed in the reaction Were in the range of about 2480 C. to 2580 C.

2,79o,sss

15 Example 13 White gasoline of d, =0.7203 and of average formula CmsHw was pyrolyzed in equipment similar to that described in Example 2. The hot combustion products were made by burning 0.60 cubic feet per minute of propane with 2.95 cubic feet per minute of oxygen in the presence of 3.6 cubic feet per minute of steam. The gasoline was introduced to the reactor at the rate of 164 cubic centimeters per minute along with 5.5 cubic feet per minute of dilution steam. These were preheated to a temperature of 430 C. The effluents from the reaction chamber were produced at the rate of 7.54 cubic feet per minute and were quenched with water upon leaving the reaction chamber. Analyses indicated that the products were as follows: 9.7 percent acetylene, 7.1 percent ethylene, 1 percent propylene, 32.6 percent hydrogen, 12.8 percent methane, 14.6 percent carbon dioxide, 22 percent carbon monoxide and 0.2 percent oxygen. The conversion of the white gasoline was 22.4 percent to acetylene, 16.4 percent to ethylene and 3.5 percent to propylene. In this example, the combustion gases employed in the reaction were about in the range of 2300 C. to 2425 C.

Example 14 In an apparatus of similar design and dimensions as that described in Example 3, isobutane was pyrolyzed with hot combustion gases produced by burning propane at the rate of 0.71 cubic feet per minute by oxygen at the rate of 3.47 cubic feet per minute in the presence of steam at 1.65 cubic feet per minute. The isobutane was introduced to the reaction chamber at the rate of 1.56 cubic feet per minute in the presence of steam at 6.3 cubic feet per minute. This reactant gas steam was preheated to 575 C. When these conditions were used the temperature at the downstream side of the venturi was found to be 1100 C. The gaseous products leaving the reaction chamber were immediately cooled to 635 C. with steam. Analyses of the products indicated the following composition: 8.0 percent acetylene, 3.2 percent ethylene, 0.4 percent benzene, 0.5 pcrcent ethane, 13.3 percent methane, 37.7 percent hydrogen, 24.7 percent carbon monoxide, 11.2 percent carbon dioxide, 0.8 percent nitrogen and 0.2 percent oxygen. The calculated conversion of isobutane to acetylene was 37 percent. In this example the combustion products were at a temperature range of about 2400 C. to 2550 C.

Example 15 Propylene Was pyrolyzed with combustion gases pro duced by burning 0.42 cubic feet per minute of propane with 1.45 cubic feet per minute of oxygen in the presence of no furnace diluent. Propylene in the absence of any diluent was introduced to the reaction chamber at the rate of 5.0 cubic feet per minute. The propylene was preheated to 480 C. Under these conditions the temperature of the reacting gas mixture at the downstream side of the venturi was found to be 865 C. The eifiuent gases from the reaction chamber were not cooled and were at a temperature of 480 C. The eflluent products analyzed 2.3 percent acetylene, 20.3 percent ethylene, 1.8 percent propylene, 0.8 percent benzene, 1.7 percent ethane, 33.8 percent methane, 22.0 percent hydrogen, 11.7 percent carbon monoxide, 0.3 percent oxygen and 5.3 percent carbon dioxide. In this example the combustion products were in a temperature range of about 2200 C. to 2500 C.

Example 16 In a manner similar to Example 9 propane was pyrolyzed with a combustion gas produced by burning methane with oxygen in the absence of diluent. The propane feed stock was not preheated and was added to the reaction chamber in the absence of any diluent. The products from the reaction chamber analyzed 5.6 percent acetylene, 11.2 percent ethylene, 2.4 percent propylene, 22.2 percent ethane. 2.5 percent propane, 27.3 percent hydrogen, 10.2

Example 17 Using equipment similar to that described in Example 3, propane was pyrolyzed with a combustion gas produced by burning 3.77 cubic feet per minute of recovered byproducts with 2.02 cubic feet per minute of oxygen in the presence of 3.75 cubic feet per minute of steam. The byproducts were recovered from the effluents of the pyrolysis process after separating the desired components. The fuel so recovered consisted of 23.7 percent carbon monoxide, 13.0 percent carbon dioxide, 47.3 percent hydrogen and 16.0 percent methane. The propane was fed into the reaction chamber at the rate of 1.46 cubic feet per minute in the presence of 4.15 cubic feet per minute of dilution steam. No preheating of fuel or reactant propane was carried out. The effluents from the reaction chamber were cooled with steam to 585 C. The analysis of the products was 7.4 percent acetylene, 8.4 percent ethylene, 0.2 percent propylene, 10.7 percent methane, 30.4 percent hydrogen and 1.3 percent nitrogen with the remainder products of combustion. Conversions to unsaturated hydrocarbons amounted to 27.3 percent to acetylene, 30.8 percent to ethylene, and 1.0 percent to propylene. Conversion of propane to carbon amounted to 7.3 percent. In this above example the combustion gases employed in the reaction were above 1900 C.

Example 18 In an apparatus of the general arrangement shown in Fig. 4 with a combustion furnace 8 inches in length and 2 inches in internal diameter fabricated of stabilized zirconia with a V2 inch efiluent orifice and with a reaction chamber 20 inches in length and 4 inches in diameter equipped with a venturi constriction of zirconia 6 inches in length and with a throat inches, 248 cubic centimeters of natural gasoline per minute and 3.0 cubic feet per minute of steam were reacted with a combustion gas produced by burning 0.90 cubic feet per minute of propane with 2.27 cubic feet per minute of oxygen. The natural gasoline and steam were preheated to 470 C. in a heat exchanger with the heat supplied by the effluents of the reaction chamber. The temperature measured at the downstream side of the venturi was 810 C. Gaseous products issued from the reaction chamber at the rate of 9.54 cubic feet per minute. These products analyzed 15.7 percent ethylene, 5.8 percent propylene, 0.2 percent butyl ene, 28.0 percent hydrogen, 24 percent carbon monoxide, 7.6 percent methane, 10.6 percent ethane, 0.5 percent nitrogen, 0.3 percent oxygen, 1.2 percent acetylene, 3.9 percent carbon dioxide and 2.2 percent products condensable at -40 C. (benzene and the like). The percent gasification in this .examplewas 96.5. The natural gasoline employed was of d, =0.635 and average formula C4.ssH11.as. In this example the combustion products were at a temperature above 1900 C.

Example 19 Natural gasoline as used in Example 18 was pyrolyzed continuously in an apparatus, generally similar to that shown in Fig. 1, of the following dimensions: the stabilized zirconia furnace was 2 inches in internal diameter, 7 inches long with a /2 inch diameter outlet orifice; the reaction chamber was 5 inches in internal diameter, 8 /2 inches in length, equipped with a venturi 6 inches in length with a 1 inch throat. The natural gasoline was admitted to the reaction chamber at the rate of 400 cubic centimeters per minute in the presence of 3.1 cubic feet per minute of steam and 0.66 cubic feet per minute of carbon dioxide. These materials were preheated to 480 C. The combustion gas wa produced by burning 1.47 cubic feet per minute of propane with 2.94 cubic feet per minute of oxygen. With these conditions the temperature at the exit end of the venturi was found to be 810 C. The gaseous products issuing from the reaction chamber at 12.7 cubic feet per minute were not cooled and were'at a temperature of 700 C. These products analyzed 17.3 percent ethylene, 5.6 percent propylene, 24.4 percent hydrogen, 22.1 percent carbon monoxide, 7.4 percent methane, 12.6 percent ethane, 0.5 percent nitrogen, 0.4 percent oxygen, 7.7 percent carbon dioxide, and 2.0 percent acetylene. In this example the combustion products were at a temperature above 1900 C.

Example 20 Natural gasoline as used in Example 18 was pyrolyzed in an apparatus generally similar to that shown in Fig. 1 of the following dimensions: the zirconia furnace was 8 inches in length and 2 inches in internal diameter with a /2 inch effluent orifice, the reaction chamber was 5 inches in internal diameter equipped with a venturi 6 inches in length with a /4 throat. Natural gasoline Was introduced to the reaction chamber at the rate of 245 cubic centimeters per minute in the presence of 7.15 cubic feet of steam. These were preheated to 245 C. The combustion gases were produced by burning 2.0 cubic feet per minute of propane with 3.70 cubic feet per minute of oxygen. With these conditions the temperature at the downstream side of the venturi was found to be 845 C. Gaseous effluents from the reaction chamber were not cooled but issued at a temperature of 785 C. The product analyzed 13.3 percent ethylene, 3.2 percent propylene, 32.5 percent hydrogen, 28.8 percent carbon monoxide, 9.9 percent methane, 5.2 percent ethane, 0.7 percent nitrogen, 0.4 percent oxygen, 1.6 percent acetylene, 3.8 percent carbon dioxide, and 0.6 percent materials condensable at -40 C. In this example the combustion products were at a temperature above 1900 C.

Example 21 In an apparatus similar in design and dimensions to that given in Example 19, natural gasoline as used in Example 18 was pyrolyzed by a combustion gas produced by burning 1.14 cubic feet per minute of propane with 3.12 cubic feet per minute of oxygen.- The natural gasoline was introduced to the reaction chamber at the rate of 362 cubic centimeters per minute in the presence of 2.65 cubic feet per minute or steam and 0.30 cubic feet per minute of carbon dioxide. These were preheated to 525 C. With these conditions the temperature downstream from the venturi was recorded as 873 C. The efiluent gases from the reaction chamber were not cooled but issued at a temperature of 765 C. These gases analyzed 21.0 percent ethylene, 3.6 percent propylene, 23.0 percent hydrogen, 18.5 percent carbonv monoxide, 18.2 percent methane, 3.8 percent ethane, 0.9 percent nitrogen, 0.2 percent oxygen, 6.6 percent carbon dioxide, 2.8 percent acetylene, and 1.4 percent condensable productsat ..40 C. In this example the combustion products were at a temperature above 1900 C.

Example 22 In an apparatus of. the design and dimensions given in Example 19, ethane was pyrolyzed by a combustion gas produced by burning 0.55 cubic feet per minute of propane with 2.02 cubic feet per minute of oxygen in the presence of 1.25 cubic feet per minute of steam. The

18 was 6.0 percent to acetylene, 44.5 percent to ethylene, and 17.1 percent to methane. In this example the combustion products were in a temperature range of about 2375 to 2525C.

Example 23 In an apparatus arrangement of the type given in Fig. 5, propane was pyrolyzed to give a product containing ethylene, propylene, carbon monoxide and hydrogen. The combustion furnace fabricated of stabilized zirconia was 18 inches in length and 6 inches in internal diameter while the reaction chamber was 18 inches in length containing a venturi 3% inches long with a 2% inch throat. The reactant hydrocarbon stream consisting of 16 cubic feet per minute of propane and 30.0 cubic feet per minute of dilution steam, was preheated to 600 C. Combustion products were produced by burning 6.0 cubic feet per minute of propane with 23.2 cubic feet of oxygen, in the presence of 86 cubic feet per minute of steam. All streams entering the combustion furnace were preheated to 600 C. The off-gas which was quenched with water, analyzed 13.7 ethylene, 0.8 percent propylene, 39.2 hydrogen, 11.4 carbon monoxide, 15.7 percent methane, 0.7 percent nitrogen, 5.6 percent acetylene and 12.9 percent carbon dioxide. For each pound of propane pyrolyzed 0.45 pound of ethylene, 0.039 pound of propylene, and 0.17 pound of acetylene were produced. In this example, the combustion gases employed in the reaction were of a range of about 1800 to 1950 C.

Example 24 In an apparatus arrangement as used in Example 20, methane was burned with oxygen in the absence of any diluent. Propane was fed into the reaction chamber to give gaseous products containing 11.2 percent ethylene, 2.4 percent propylene, 12.4 percent carbon monoxide, 27.3 percent hydrogen, 5.7 percent nitrogen, 0.5 percent oxygen, 22.2 percent ethane, 0.5 percent propane, 10.2 percent carbon dioxide and 5.6 acetylene.

Example 25 In an apparatus of the general appearance of that shown in Fig. 5, with a combustion furnace 18 inches in length, and 6 inches in internal diameter fabricated of stabilized zirconia, and .with a reaction chamber 18 inches in length with a venturi type constriction 3% inches in length with .a'2 /2 inch throat, propane was pyrolyzed to give high yields of acetylene and ethylene. The hot combustion gases were produced by burning 7.3 cubic feet per minute ofpropane with 31.0 cubic feet per minute of oxygen in the presence of 59.0 cubic feet per minute of steam. The propane to be cracked was introduced into the reaction chamber before the throat of the venturi at the rate of 29.5 cubic feet per minute. All streams entering the furnace were preheated to 600 C. and the reactant gas stream entering the reaction chamber was preheated to 600 C. The products issuing from the reaction chamber were immediately cooled with water. The effiuent stream analyzed 8.7 percent acetylene, 10.9 percent ethylene, 0.8 percentpropylene, 15.0 percent methane, 38.6 percent hydrogen. The remainder was essentially products of combustion. For each pound of propane pyrolyzed the following weights of unsaturated materials were produced: acetylene 0.218 pound, ethylene 0.293 pound, and propylene 0.0325 pound. The actual construction of the apparatus used is given in Fig. 12.

Example 26 arouses preheated to 600 C. The products issuing from the reaction chamber analyzed 7.5 percent acetylene, 15.2 percent ethylene, 1.2 percent propylene, 16.6 percent methane, and 36.1 percent hydrogen. The remainder was essentially products of combustion. For each pound of propane pyrolyzed under these conditions, 0.177 pound of acetylene, 0.386 pound of ethylene and 0.045 pound of propylene were produced. The construction of the apparatus used is given in Fig. 12.

Example 27 Using the same fuel and cracking stock in the same apparatus as in Example 25, but altering conditions of temperature and feed rates a very high yield of acetylene and ethylene was produced. The combustion gas was produced from 4.69 cubic feet per minute of propane burned with 100.5 cubic feet per minute of air. The preheat temperature of these streams was 600 C. The propane cracking stock, also preheated to 600 C., was introduced to the reaction chamber at the rate of 18.7 cubic feet per minute. The reaction products were produced at the rate of 150.1 cubic feet per minute and were cooled with water. They analyzed 5.0 percent acetylene, 6.2 percent ethylene, 0.4 percent propylene, 16.1 percent hydrogen, 7.3 percent methane, 0.1 percent ethane, 53.6 percent nitrogen, and remainder combustion products. The conversion of the propane cracking stock was 23.7 percent to acetylene, and 31.7 percent to ethylene. The conversion to carbon was 12 percent.

I claim:

1. A single-pass cracking method for the production of mixtures of acetylene and ethylene comprising the steps of 1) forming a feed stock stream comprising principally at least one lower paraflinic hydrocarbon higher than methane, (2) introducing into a combustion zone components comprising a fuel and a combustion supporting gas, the components including at least one preheated gaseous stream and the components containing not substantially more than a stoichiometric amount of oxygen based on the fuel content, (3) forming a gaseous hot combustion products mixture in the combustion zone out of contact with the feed stock stream by combustion of the fuel in the presence of all other of the components, (4) discharging the hot combustion products mixture in the form of a stream of gases issuing from the combustion zone at a velocity of an order less than the speed of sound and in the range from about 200 feet per minute to the speed of sound into a mixing zone at a temperature which is substantially the initial combustion products mixture formation temperature and which is at least as high as about 1800 C., (5) forming a mixture of feed stock and combustion products mixture by introducing said feed stock stream, at a temperature at least about 1100 C. lower than the temperature of the combustion products mixture stream entering the mixing zone, into the mixing zone in direct contact with the combustion products mixture stream, (6) effecting substantially complete conversion of the feed stock into cracked gases comprising only minor quantities of multi-earbon hydrocarbons other than acetylene and ethylene by immediately discharging'the mixture of feed stock and combustion products mixture from the mixing zone into a reaction completion zone while maintaining the temperature of the mixture in the reaction completion zone within a range of about 800 C. to about 1500 C. by controlling the temperatures and volumes of the streams of combustion products and feed stock, (7) maintaining the mixing zone and the reaction completion zone substantially free of free oxygen other than oxygen originating from the dissociation of carbon oxides in the combustion products mixture, (8) quenching the cracked gases by chilling within less than one second after mixture of the combustion products with the feed stock, and (9) recovering at least acetylene from the thus cracked and quenched gases.

2. A method as defined in claim 1 wherein the feed stock stream is a substantially unprecracked stream substantially free of acetylene and ethylene.

3. A method as defined in claim 1 wherein the lower paraflinic hydrocarbon is propane, the temperature of the gaseous hot combustion products mixture stream discharged into the mixing zone is about 2100" C., and the temperature of the feed stock stream, the volume of the stream of combustion products mixture and the volume of the stream of feed stock are controlled to give cracked gases containing at least by weight of acetylene and ethylene.

4. A method as defined in claim 1 wherein the components contain a less than theoretically equivalent amount of oxygen, the feed stock stream is preheated to not more than about 700 C., is substantially free of acetylene and ethylene, and is introduced substantially perpendicularly into the combustion products mixture stream in the mixing zone, and the combustion products mixture stream is directed axially from the combustion zone, directly through the mixing zone and axially into the mouth of u constriction in a discharge passage from the mixing zone.

5. In a single pass cracking process for the production of mixtures of acetylene and ethylene an improved method comprising the combination of the steps of (l) introducing into an elongated refractory combustion chamber adjacent one end thereof heating mixture makeup components comprising at least one preheated gas, said components including a fuel and a combustion supporting gas and said components containing a total of not substantially more than a stoichiometric amount of oxygen based on the fuel content, (2) burning the fuel within the combustion chamber in the presence of all other of said components and forming thereby a hot gaseous heating mixture free of any substantial amount of oxygen other than that resulting from high temperature dissociation of carbon oxides, (3) forming the hot gaseous heating mixture into a high velocity stream of gases issuing from the combustion chamber at a velocity of an order less than the speed of sound and in the range from about 200 feet per minute to the speed of sound by discharging the mixture from the combustion chamber through a restricted orifice in an end opposite the components intro duction end, (4) forming a feed stock stream comprising principally at least one lower parafiinic hydrocarbon higher than methane, (5) directing the high velocity heating mixture stream from the restricted orifice immediately and directly into an adjacent mixing zone at a temperature which is substantially the initial formation temperature of the gaseous heating mixture and which it at least as high as about 1800" C., (6) exposing the feed stock for the first time to direct contact with the heating mixture stream and forming a reaction mixture of feed stock and heating mixture by introducing said feed stock stream at a temperature at least about 1100 C. lower than the temperature of the hot gaseous heating mixture stream into the mixing zone in direct contact with the heating mixture stream, (7 effecting substantially complete conversion of the feed stock into cracked gases comprising only minor quantities of multi-carbon hydrocarbons other than acetylene and ethylene by immediately discharging the reaction mixture of feed stock and heating mixture from the mixing zone into a reaction completion zone while maintaining the temperature of the reaction mixture in the reaction completion zone within a range of about 800 C., to about 1500 C. by controlling the temperatures and volumes of the streams of heating gases and feed stocks, and while maintaining the reaction completion zone substantially free from oxygen other than that introduced in the heating mixture, (8) quenching the reaction mixture by chilling within less than one second after mixture of the heating mixture with the feed stock, and (9) recovering at least acetylene from the thus quenched reaction mixture.

6. A method as defined in claim 5 wherein the feed 21 stock stream is a substantially unprecracked stream substantially free of acetylene and ethylene.

7. A method as defined in claim 5 wherein the lower paraflinc hydrocarbon is propane, the temperature of the gaseous hot combustion products mixture stream discharged into the mixing zone is about 2100 C. and the temperature of the feed stock stream, the volume of the stream of combustion products mixture and the volume of the stream of feed stock are controlled to give cracked gases containing at least 50% by weight of acetylene and ethylene.

8. A method as defined in claim 5 wherein the components contain a less than theoretically equivalent amount of oxygen, the feed stock stream is preheated to not more than about 700 C., is substantially free of acetylene and 15 ethylene, and is introduced substantially perpendicularly into the combustion products mixture stream in the mix ing zone and the combustion products mixture stream is 'directed axially from the combustion zone, directly through the mixing zone and axially into the mouth of a constriction in a discharge passage from the mixing zone.

References Cited in the file of this patent UNITED STATES PATENTS Hincke Mar. 14, 1944 2,377,847 Allen et al. June 12, 1945 2,394,849 Doumani et a1. Feb 12, 1946 2,520,149 Keeling Aug. 29, 1950 2,572,664 Robinson Oct. 23, 1951

Claims (1)

1. AN SINGLE-PASS CRACKING METHOD FOR THE PRODUCTION OF MIXTURES OF ACETYLENE AND ETHYLENE COMPRISING THE STEPS OF (1) FORMING A FEED STOCK STREAM COMPRISING PRINCIPALLY AT LEAST ONE LOWER PARAFFINIC HYDROCARBON HIGHER THAN METHANE, (2) INTRODUCING INTO A COMBUSTION ZONE COMPONENTS COMPRISING A FUEL AND A COMBUSTION SUPPORTING GAS, THE COMPONENTS INCLUDING AT LEAST ONE PREHEATED GASEOUS STREAM AND THE COMPONENTS CONTAINING NOT SUBSTANTIALLY MORE THAN A STOICHIOMETRIC AMOUNT OF OXYGEN BASED ON THE FUEL CONTENT, (3) FORMING A GASEOUS HOT COMBUSTION PRODUCTS MIXTURE IN THE COMBUSTION ZONE OUT OF CONTACT WITH THE FEED STOCK STREAM BY COMBUSTION OF THE FUEL IN THE PRESENCE OF ALL OTHER OF THE COMPONENTS, (4) DISCHARGING THE HOT COMBUSTION PRODUCTS MIXTURE IN THE FORM OF A STREAM OF GASES ISSUING FROM THE COMBUSTION ZONE AT A VELOCITY OF AN ORDER LESS THAN THE SPEED OF SOUND AND IN THE RANGE FROM ABOUT 200 FEET PER MINUTE TO THE SPEED OF SOUND ONTO A MIXING ZONE AT A TEMPERATURE WHICH IS SUBSTANTIALLY THE INITIAL COMBUSTION PRODUCTS MIXTURE FORMATION TEMPERATURE AND WHICH IS AT LEAST AS HIGH AS ABOUT 1800*C., (5) FORMING A MIXTURE OF FEED STOCK AND COMBUSTION PRODUCTS MIXTURE BY INTRODUCING SAID FEED STOCK STREAM, AT A TEMPERATURE AT LEAST ABOUT 1100*C. LOWER THAN THE TEMPERATURE OF THE COMBUSTION PRODUCTS MIXTURE STREAM ENTERING THE MIXING ZONE, INTO THE MIXING ZONE IN DIRECT CONTACT WITH THE COM BUSTION PRODUCTS MIXTURE STREAM, (6) EFFECTING SUBSTANTIALLY COMPLETE CONVERSION OF THE FEED STOCK INTO CRACKED GASES COMPRISING ONLY MINOE QUANTITIES OF MULTI-CARBON HYDROCARBONS OTHER THAN ACETYLENE AND ETHYLENE BY IMMEDIATELY DISCHARGING THE MIXTURE OF FEED STOCK AND COMBUSTION PRODUCTS MIXTURE FROM THE MIXING ZONE INTO A REACTION COMPLETION ZONE WHILE MAINTAINING THE TEMPERATURE OF THE MIXITURE IN THE REACTION COMPLETION ZONE WITHIN A RANGE OF ABOUT 800*C. TO ABOUT 1500*C. BY CONTROLLING THE TEMPERATURES AND VOLUMES OF THE STREAMS OF COMBUSTION PRODUCTS AND FEED STOCK, (7) MAINTAINING THE MIXING ZONE AND THE REACTION COMPLETION ZONE SUBSTANTIALLY FREE OF FREE OXYGEN OTHER THAN OXYGEN ORIGINATING FROM THE DISSOCIATION OF CARBON OXIDES IN THE COMBUSTION PRODUCTS MIXTURE, (8) QUENCHING THE CRACKED GASES BY CHILLING WITHIN LESS FROM ONE SECOND AFTER MIXTURE OF THE COMBUSTION PRODUCTS WITH THE FEED STOCK, AND (9) RECOVERING AT LEAST ACETYLENE FROM THE THUS CRACKED AND QUENCHED GASES.

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