US2349160A - Process for converting hydrocarbons - Google Patents

Description

May 16, 1944. F. E. FREY Erm. 2,349,160

PROCESS FOR CONVERTING HYDROCRBONS Filed April 29, 1940 ML /wmvA/bm ROBERT DA SNOW Patented May I6, i944 UNITED STATES PATENT l OFFICE raocsss Foa comme maocAaBoNs Frederick E. Frey, and Robert D. Snow, Bartlesville,` Okla., and Walter F. Huppke, Lomida, Calif., assignors to Phillips Petroleum Company, a corporation of Delaware Apputmon Apru 29, 1940, semina. 332,392

' 9 claims. A(ol. 19o-49) This invention -relates tothe conversion of simple aliphatic hydrocarbons into volatile, nor- These processes are readily. adaptable to the production of motor fuel. from naturally occurring maily liquid hydrocarbons. 'More specifically it relates to the conversion of parains and/or oletlns 'into hydrocarbons boiling-in the motor fuel boiling range by a catalytic treatment, and

preferably by two or moreA catalytic' treatments.4

This application` is u. continuation-impart of ourcopending application' Serial No. 745,348,

'iiled September 24, 1934, now U. S. Patent 2,227,-

639,l granted Jan. '1, 1941.

Man-y `processes/have been proposed in the past for increasingthe yield of hydrocarbons in the' motor fuel boiling range from hydrocarbon fractions or mixtures which-'occur naturally, such as natural gas and crude oil, as well as from similar mixtures which are produced artiflcally, such as by the destructive hydrogenation of heavy tars, lignites, coals, etc., or by l the reaction of .carbon oxides and hydrogen. While hydrocarbon materials from vsuch sources generally comprise or contain substantial quantities of hydrocarbons in the motor fuel range, the greater proportion' of the hydrocarbons in such mixtures are often not in this desirable lus For quite a number of yearsk there have been I increasing demands notv only for larger quantities of 'motor fuel but also for motor fuels with improved antidetonation properties, or fuels with higher octane numbers, as this feature is more During the greater part of often referred to.` this period the demands for more motor fuel were met by fcracking hydrocarbons which boiled above the motor fuel range. Such cracking processes are -conducted by heating 'heavier hydrocarbons to temperatures between about 850 and 1400 Runder low or high superatmospheric pressures. Although these cracking processes permit a considerable increase in the amount of motor fuel which can be obtained from a given amount of crude oil or petroleum, `they also result in a production of considerable quantities of light gaseous material and of heavy tars and coke. Both these types of by-produ'cts represent valuable carbonaceous material present in the original charge to the cracking process which ,is not recovered as motor fuel-the desired prod-y uct.

More recently,V the production of motor fuel has been augmented to a small, although appreciable extent by the development of various gas conversion processes, which convert certain light or normally gaseous hydrocarbons to hydrocarbons having higher Vmolecular weights.

vlight or gaseous hydrocarbons, or from similar hydrocarbonsproduced as by-products in-the aforementioned cracking processes. Although,- comparatively speaking.' these gas conversion, vor

polymerization, processes do not at present produce a large proportion of the total motor fuel produced from all sources, nevertheless the motor fuels producedv by such processes generally have premium qualities, and nearly all the so-called "high octanefuels of the` present time are produced by such polymerization processes. We have found that the process which forms the principal subject rmatter of our hereinbefore mentioned application Serial No. 745,348 is one) proportions of the gases produced by ordinary cracking processes are not readily converted to motor fuel range hydrocarbons, such as ethanel and more especially methane, large amounts of valuable carbonaceous materials being lost every vday in the forml of methane.

As has just been mentioned, there is an increasing demand not only for more motor fuel,

but also for motor fuels with improved antidetonation properties. Many hydrocarbons or hydrocarbon fractions in the motor fuel range recovered from natural sources, or `recovered from asynthetic hydrogenation process, do not have'desirable antidetonating qualities. It has therefore been found necessary in many cases t0 subject suchhydrocarbon fractions to some sort of reforming operation, whereby a fraction in the motor fuel range is recovered with better. antidetonating qualities. Most such reforming operations are similar to the aforementioned cracking processes and are accompanied by the production of\appreciable amounts of tar and light gases, ywhich represent lost carbonaceous material.

In our hereinbefore mentioned copending ap' 'produced by such treatment.

ing oleilns are polymerized to produce hydrocarbons in the motorfuel boiling range, -heavier hydrocarbons are, at times, also produced, and we have also disclosed that such heavier hydrocarbons can be depolymerize'd in the presence of a depolymerization catalyst to form lighter olens. The lighter'oleins so formed may be in the motor fuel boiling range and suitable for inclusion in motor fuels as they are, or after nondestructive lrvdrogenation, or they may be somewhat lower boiling than the-motor fuel range but suitable for subsequent poly-- merization to form hydrocarbons in the motor fuel range. We have also disclosed that .cer-

K tain solid depolymerization catalysts are especially suitable for use in such depolymerization operations, namely, hydrous aluminum silicates,

mixed alumina and silica gels, such as disclosedV in McKinney 2,142,324 and 2,147,985 and in the copending application of Frey Serial No. 329,195,

` led April 11. 1940, fullers earth, especially when activated by treatment with a halogen acid, and the like catalysts. We have found that these s ame catalysts are good catalysts for the polymerization of olens to form motor fuel range Y hydrocarbons, and vthey are often referred to as polymerization catalysts. However, modiiications best adapted for depolymerization may not best adapted for polymerization, as may be determined bytrial for any particular case.

We have found that-not only may heavier polymeric olen hydrocarbons be treated in the presence of depolymerization catalysts to'produce lighter oleflns, but also that other heavier unsaturated hydrocarbons which have not been Y produced through a polymerization step can be' l ltreated, or cracked, in the presence of a'depolymerization catalyst and will produce lighter olefin hydrocarbons. ,We have-also found that very little material lower boiling than propene is Thus we have found thatolen hydrocarbonsboiling above, or in the upper part of the motor fuel boiling range and produced by either thermal orcatalytic dehydrogenation, may be cracked in the presence of a depolymerization catalyst to produce lighter olens which are predominantly eitherin the motor fuel range or which may be readily catalytically polymerized .to form hydrocarbons in the motor fuel range. We have further invented a process whereby heavier hydrocarbons can be converted to lighter hydrocarbons in the motor' fuel range with very little, if any, loss of carbonaceous material comprising iirst catalytically dehydrogenating such heavier hydrocarbons and subsequently cracking the unsaturated hydrocarbons so produced in the presence of a depoly merization catalyst.

It is an lobject of our invention to produce lighter hydrocarbons from heavier hydrocarbons with a minimum loss'of carbonaceous material.

A further object of our invention is to produce practically a quantitative yield of hydrocarbons by a process which involves a catalytic cracldng step.

It is another objectof our invention to submit heavier olefin hydrocarbons from any source to catalytic'cracking in the presence of a depolymerization catalyst to produce lighter hydrocarbons which do Vnot comprise substantial amounts ofjmethane or ethane.

Another object of our invention is to obtain motor fuel range hydrocarbons from heavier paraffin hydrocarbons by a process comprising thecombination of dehydrgenation of the-heavier parafiins to form olens and a catalytic cracking of the olefins so produced-in the presence of a solid depolymerization catalyst. 'A

. Still a further 'object' of our invention isto dehydrogenize catalytically paraillns heavier f than motor fuel to form heavy oletlns and free' hydrogen, to crack catalytically heavier `oleflns so producedto form hydrocarbons in the motor fuel range, and to hydrogenate atleast a part ofthe 'hydrocarbons so produced inthe presence of hydrogen produced by said dehydrogenation.

Further objects and advantages of our invention will be found from the accompanying dis- .A

carbon bonds, forming at least two smaller hy-l l drocarbon molecules or radicals. Depolymeriz" tion is a specific form of cracking, wherein hydrocarbons formed by polymerization are converted to hydrocarbons of lower molecular weights, generally the original monomeric hydrocarbons. Reference is made to cracking in the presence of a depolymerization catalyst, and we have found that, for the purpose of our disclosure`a catalyst may beJ defined as a vdepolylmerization catalyst when it will promote the Vformation of isobutylene from diisobutylene.

For instance, welhave depolymerized diisobutylene by passing the vapors overa granular silicaalumina catalyst at 'a temperature of. 392 F. at an absolute pressure of 0.58 pound per square inch and a ow rate of 1.27 volumes of liquid per volume of catalyst granules per hour, with a* depolymerization of 58 per cent of the diisobutylene per pass into isobutylene with a formation of heavy polymer of less than one per cent. Whilewe have not found any exceptions to the rule that sucha depolymerization catalyst be effective in our process, we have found that certaindepolymerization catalysts are especially efllcient in our process. These catalysts are hydrous aluminum silicates,silicaalumina catalysts. such as mixed alumina and silica gels and more especially those silica-alumina catalysts disclosed in McKinney 2,142,324 and 2,147,985, and in the copending application of Frey Serial No. 329,195, filed April l1, i940, fullers earth, especially fullers earth, activated with a halogen acid, and the like. In the silica-alumina catalysts as mentioned above there will be a major proportion of silica and a minor proportion of alumina; generally not more than 5 per cent by weight and more often between about 0.5 and 2 per cent. I

We have found that not only .olefin polymers, but also nonpolymeric oleflns can be cracked in the presence of these'catalysts. We have further found that olens having at least six carbon atoms per molecule are most efficiently treated, and will produce very little material lighter than propene when the cracking conditions are properly controlled. We have found that, in general, the temperature should be between about 300 and 1100 F., and preferably between about 550 and 1050 F. The operating pressure for the hydrocarbons inthe cracking' ide catalyst, especially the chromium oxide gel phase, and subatmospheric pressures maybe employed at times although this is generally not feasible on a commercial scale. Inert gases may be included 'to facilitate operation in the vapor phase, if it should appear feasible in any particular instance. In many instances the'olefins will be accompanied by saturated hydrocarbons, which will be substantially inert under the conditions of cracking. The flow rate should be between 0.25 and 10. liquid volumes of hydrocarbon per volume of catalyst per hour, with the best operation being between l and 4 liquid volumes of charge. It is desirable in this operation to avoid excessive deposition of carbonaceous materiai on the catalyst, and the rate of formation of such material will be a factor to be considered in establishing reaction conditions. For any particular catalyst and/or charge stock, opy timum conditions' of temperature.' pressure, and now rate can be readily determined by trial by l one skilled in the art.

' range from less desirable hydrocarbons in the motor fuel range, in which case hydrocarbons of six to eight or nine carbon atoms will be charged, y and treated in the cracking step to produce hydrocarbons of similar molecular weight, or molecg u lar weight range, but more desirable molecular structure the most usual operation will be in connection with the production of hydrocarbons in the motor fuel range from hydrocarbons of 10 or more carbon atoms per molecule,l generally of 14 to 20 or 22 or more carbon atoms per molecule. Hydrocarbons of 10 to about 14 carbon atoms per molecule are in the motor fuel range, but are den'- nitely in the upper part of it as dened at present and such hydrocarbons will be more often treated 4 than lighter normally liquid hydrocarbons. When heavier hydrocarbons are treated in our process, a substantial proportion of the products of the catalytic cracking step will be in the motor fuel range, while when lighter hydrocarbons are treated. substantial proportions of very light or normally gaseous hydrocarbons are produced which can be readily polymerized to form motor fuel range hydrocarbons, as will be mole fully. described. i

When our complete process includes a dehydrogenation step, we prefer that this should be operiated as a catalytic step also. lIn this way, full advantage ls taken of our catalytic cracking step, sincecatalytic dehydrogenation can be operated to produce olens with little loss of carbonaceous material, and catalytic dehydrogenation thus combines with catalytic cracking of oleiins to produce a lighter hydrocarbon product with little disclosed in Huppke and Frey 1,905,383, Frey and Huppke, 2,098,959 (Re. 21,911), and other forms of black, unglowed chromium oxide such as disclosed in the copending applications of Morey Serial No. 113,091, now Patent 2,288,320, issued June 30, 1942, and Serial No. 359,295, filed `October 1, 1940, of Matuszak and Morey Serial No. 173,708, now Patent 2,294,414, issued September 1,1942, of Morey and Frey Serial No. 173,709, now Patent 2,312,572, issued March 2, 1943, and Serial No.v 359,296, filed October 1, 1940, andSchulze Serial No. 10,697, now Patent 2,183,591, issued December 19, 1939. However, we do not necessarily wish to restrict ourselves to such catalysts, and other catal'ysts which will promote a clean cut dehydrogenation of lparaffin hydrocarbons to form free hydrogen and olefins of the same number of car-v bon atoms per molecule, with a minimum of concomitant cracking reactions, may beused. In many instances the hydrocarbon fractions to be treated will contain organicsulfur compounds, such as mercaptans, suldes', disulfldes, thi'o- 'phenea thiophanes andthe like. These -compounds will be more or less completely decomposed along with or prior to thedehydrogenation, and in such instances the dehydrogenation catalysts used should be such as willl not be .poisoned by sulfur compounds, an advantage of the chromium oxide -catalysts mentioned. In such cases, the delsulfurizatiori and dehydrog ation may be carried out in two or more steps, sim ar to those disclosed in Schulze 2,151,721. However, this part of our process is primarily a dehydrogenation step rather than one of desulfurization alone. The temperature of the dehydrogenation will generally be between about 750 and 1200fa F., and we prefer to use low pressures, not in excess of about 250 pounds -per square inch andf preferably less than 100 pounds per square inch. The reaction times should be such that. the eiliuent will contain between 10 and 40 percent by volume of oleiins, preferably 15 to 25 per cent, but not long enough to induce appreciable cracking reactions. Actual temperatures, pressures, and reaction times will vary between'individual cases since these factors are also dependent upon catalyst activity and characteristics of the charge stock, and optimum conditions for each application of the process may be readily determined by trial by one ski1led in the art.

Our process may also include a polymerization step and/or a hydrogenation step. iAs mentioned,

in one specific modification our catalytic cracking catalyst such as a silica-alumina catalyst, and the overall loss of carbonaceous material. Further-` alyst we prefer to use some form of chromium ox- 'In like, or solid phosphoric acids, or liquid catalysts such as sulfuric and sulfonic acids, or phosphoric acids, or a vaporous catalyst such as boron trifiuoride. We nd that these .polymerization cata-y lysts are not the full equivalents of-each other, and most desirable results are obtained with a silica-alumina catalyst, such as disclosed in McKinney, 2,142,324 and 2,147,985, which are most eiiiciently' used under liquid phase conditions as .disclosed in the copending application of Frey,

April 30, 1940.- When the process is primarily one involving the catalytic cracking of oleilns from a nonpolymeric sourceI a polymerization step may be included to react lighter oleiins formed by the catalytic'cracking. Again, any such polymerization step may be employed, and in this latter case it may be a specic modiiication which involves alkylation, either with paraiilns, aromatica, or the like. With-such modication, a catalyst such as sodium chloroaluminate, or concentrated sulfuric acid usedin conjunction with vigorous agitation and isoparaillns, or concentrated hydrofluoric acids maybe used.

Any process for essentially nondestructive hydrogenation may be included, and may be operated 'with hydrogen produced in this process asV being'at least a part of the hydrogen used. If only a part of the total product is hydrogenated, such hydrogen may be suiilcient in quantity, but if it is desired to eilect a complete conversion of heavier parafllnic hydrocarbons into lighter parwhich 1s mtrodueed through pipe lo wm comprise ailinic hydrocarbons, additional hydrogen will, o1

course, have to be used. Simple hydrogenation in the presence of a nickel-containing catalyst is to be preferred.

A modication of our invention will now be discussed in connection with the accompanying drawing which forms Va part of thisdisclosure and vwhich shows diagrammatically and in partial elevation one arrangement of apparatus adapted to the practice of our invention.

A parafilnicl hydrocarbon material, such as a petroleum traction in the upper part of the gasoline boiling range, or in the kerosene or gas oil range, is introduced to 'the process through pipe IB, and is introduced. into an apparatus Il forV dehydrogenation and/or desulfurization. lThe dehydrogenation and/or desulfurization step which is carried out in apparatus H is preferably a catalytic operation, and as will be readily appreciated by those skilled in the art the apparatus l l .will comprise a heating unit or furnace, one or more catalyst chambers, with various pumps, valves, temperature indicating and controlling devices, and the like, which are common and usual in such installations. When the reaction is one of dehydrogenation. we prefer to use some form of chromium oxide catalyst, as previously discussed. Ordinary hard bauxite and other mineralores may also be used, but we prefer. to use these for simple desulfurization steps. The chromium oxide catalysts may also' be used for desuliuriza- A"boiling range, and when the initial treatment in primarily normally gaseous hydrocarbons, such as propane and/or butane. t

The material which has been treated in apparatus l I is passed through pipe I 2 and valve Il to the fractionating and separating equipment Il. In actual practice the stream which enters the equipment Il may be at a higher pressure than existed during the previous dehydrogenation step, or other treatment, and will also be at an appreciably lower temperature. Adequate cooling and compressing equipment, and the like, can, of course, be included to accomplish the indicated result.v 'Ihe fractionating and separating equipe ment Il will include various fractionating co1- umns, separators, heaters and coolers, and pumps, and the like, necessary to the separation o! the ellluent from the dehydrogenation step into iractions suitable for treatment in the subsequent steps, as will be more fully discussed.

When the charge stock, which is passed through pipe Il to the dehydrogenation step, is a petroleum fraction heavier than an ordinary gasoline fractiomand the principal object o! the process is to produce valuable hydrocarbons in the gasoline apparatus I I is primarily one of dehydrogenation accompanied by cracking reactions to only a small or negligible extent, the eflluent is easily separated into a light gas fraction "predominating in free hydrogen which is removed through pipe I5 and valve I6, andan unsaturated hydrocarbon fraction which is removed through pipe I1 and is eventually passed tothe catalytic cracking apparatus ZlLas through valve i8. Heavierhydrocarbons and tar may be removed from the system through pipe 2| and valve 22. If polymerizable olens are formed, and it is desired to polymerize them to form gasoline range, or heavier, hydrocarbons, they may be removed through pipe V2l apparatus 63. It these polymerizable oleilns are present in only minor amounts, and it is not detion, either alone or where such a reaction takes place along with dehydrogenation, but such a catalyst is generally more expensive than the mineral ore catalysts which are quite suitable for desuliurization. In any event the reaction pressure should not exceed about 250 pounds per square inch, and is preferably below 100 pounds per square inch. For dehydrogenation the temperature is preferably between about 750 and 1200 F. Desuli'urization without extensive dehydrogenation can be eected at temperatures besired to submit them to polymerization, they may,

be removed from the system, as by including them with lighter material passingv through pipe Ii.

As previously discussed, the catalytic cracking operation which is conducted in apparatus 2l takes place at a temperature between about 300 and- 1000'F., and at a'relatively. low pressure. generally not in excess of about 250 pounds per square inch. The most desirable operation is `obtained with the reactant present in the vapor phase. The reaction is quitel endothermic, and for this reason it may be desirable to conduct the operation with the catalyst mass in a heat-exchange relationship with a heat-'supplying medium. However, we have found that the process tween about 500 and,800" F., and again specific f temperatures and contact times .will be dependent on catalyst activity and on charge stock. Contact times for desuliurization will be Shorter than contact times for dehydrogenation, evenv with the lower temperatures, and in any event optimum speciilc values for any speciilc casel can be readily determined by trial by one skilled in the art. When the entire process is primarily one oi' dehydrogenation-polymerization-hydrogenation, as claimed in our copending application of which this is a continuation-impart, the charge stock' is successfully operated with a large body o! catalyst, the heat being supplied solely by the heat content of the charge stock.

In the event that the unsaturate content of the hydrocarbon stream passing through pipe l1 from the fractionating equipment Il is initially not sui'ilciently great to give a desirable operation in the catalytic cracking equipment, a portion of the l stream may be diverted from pipe l1 through pipe zu and passed through valve nto pipe lo where it is reintroduced to the dehydrogenation step; In this manner. theunsaturate content of the`4 material leaving the tractionating, equipment vIl through pipe l1 is raised, and will remain at a substantially steady state after the starting-up period is passed and an equilibrium within the plant has been reached. It such a modiilcation of operation does not give a desired result, a part or all of the stream passing through pipe I1 may beremoved through pipe 21 and valve 28, and the unsaturated hydrocarbon material separated in a more concentrated form, in apparatus not shown, and this more concentrated fraction can be introduced to the catalytic cracking step through pipe 30 and valve'3I, which leads into pipe I1 on the far side of valve I8. In this ease, the unreacted saturated hydrocarbon material which remains may be reintroducedto the process through pipe III, as may be desired. In the event that a suitable unsaturated hydrocarbon material is available as such from an outside source, it may be introduced directly to the process through pipe 30. Such an unsaturated hydrocarbon material may be a fraction from a thermal cracking operation, or a fraction of polymers produced by the well known clay treating and stabilization of cracked gasoline, and the like. Alternatively, if the catalytic cracking step carried out in the apparatus 2i) is so adapted as to operate satisfactorily on a saturated charge stock, such a saturated stock may be introduced directly to the catalytic cracking step through pipe 30.

The eiliuent from the catalytic cracking step passes through pipe 33 'and valve 34 to fractionating and separating equipment 35. This equipment comprises various conventional units, as has been discussed in connection with the fractionating equipment I4. A hydrocarbon stream comprising hydrocarbons boiling in the motorfuel range produced by the catalytic cracking is passed from the -fractionating equipment 35 through pipe 36 and valve 31, and may be recovered from the process as such through pipe 40 and valve 4I. Inasmuchas this fraction will have a high content of unsaturated hydrocarbons, and since it may be desirable in many instances to secure a more or less saturated product, this stream, or at least a part of it, is conveniently hydrogenated. 'I'his is accomplished by passing the material to be hydrogenated through valve 38 inpipe 36 to the hydrogenation apparatus 42` where it it treated with free hydrogen in the presence of a suitable hydrogenation catalyst. Appreciable quantities of hydrogen are produced inthe dehydrogenation Astep in apparatus I I, and this hydrogen can be used directly by passing the stream from pipe I5 through pipe 43 and valve 44 to the latter part of pipe 36, where it is into the process through' pipe 45 and valve 46,

leading into pipes 43 and 36. The hydrogenation effluent passes through pipe 41- and valve 48 to separating means 50, and a hydrogenated hydrocarbon fraction is recovered through pipe 5| and valve 52, while other products such as light gases may be recovered through pipe 53 and valve 54. 'lfhese light gases may have a high content of free hydrogen, and may be recycled to the hydrogenation step, at least in part, by being introduced through pipe `45. `It will, of course, be appreciated that various processes may be practiced in the apparatus 4/2, although we have found that the simple illustration diagrammatically illus- Hydrocarbons 'which are higher boiling than the gasoline range can be removed from the catalytically cracked eiliuent and from fractionating means through pipe 12 .and may be discharged from the process through valve 13. The hydrocarbons in this stream may be predominantly unreacted hydrocarbons, in which case they can be recycled to the dehydrogenation step, and are passed from pipe 12 through pipe IIU and valve III to pipes 25 and I0. When the process is so operated that these hydrocarbons are adapted for direct treatment in the catalytic cracking apparatus 20, they can be passed from pipe 12 through pipe IIII and then through pipe H2 and valve II3 to pipe 86 and pipe I1. Hydrocarbon material which is too refractory and high boiling for retreatment in the process is removed through pipe 14 and valve 15, while light material. such as gas containing ethane, methane, and/or lhydrogen is removed through pipe 16 and valve 11. When it is not desired to treat lighter oleflns which may be produced by the catalytic cracking,

these may be discharged from the process, as

through pipe 1li.

I'In the polymerization apparatus 63 polymerizable oleiins charged through pipe 23 are polymerized to higherl molecular weight hydrocarbons, preferably with hydrocarbons in the gasoline boiling range asthe predominant product. While the polymerization may be carried out in the absence of a catalyst, preferably in such a case at a temperature between about 750 and 1000" F. and an elevated pressure above about 500 pounds per square inch, preferably r150 to 5000 pounds per square inch or more, we prefer to make this step a catalytic one, as previously discussed. v'Not only can the operation be carried out under' milder conditions of temperature and pressure when a catalyst is used, but also we are generally able to get a higher yield of product and also a product of somewhat diierent and often more desirable characteristics. The various units included in the polymerization apparatus 63 will vary with each particular mode of application, but will include heaters, coolers. pumps, reaction coils and/or reaction chambers, and the like common to the art, which may be readily adapted by one skilled therein. The olens charged may be those produced in the catalytic cracking operation, olefins produced directlyl by dehydrogenation in the apparatus II, or in some instances may `be introduced from an outside source; as through pipe 64 and, valve 65.. Whenthe principal source of polymerizable oleflns is from the catalytic cracking-step, these maybe in a more highly concentrated form then is feasibly charged to a polymerization unit. Such a charge may be suitably diluted with inert material, preferably polymerization apparatus 63 through pipe 66 and valves 61 and 60 tothe fractionating orseparating means 10, or it' may be passedirom pipe B6 through pipe 1| and valve 12 to pipe 30 and frac- 'tionating equipment in admixture with the. l eiliuent of the catalytic cracking step. When the polymerization -eilluent is passed to 'fractionatorj 10', a hydrocarbon fraction containing polymers Y in the motor fuel range is removed through pipe and valve 0|. It 'it is desired to submit this fraction to 'hydrogenatiom it may be passed, entirely or in part, from pipe 80 through pipe 82 and valve 03 to pipe 30 and hydrogenation appa- Vratus 42. Havier polymers, boiling below the tar range, can be separated'from the polymerization eiiluent and passed from fractionating means through pipe 84- and may be discharged through valve 05 or may be passed, entirely or A in part, through pipe 00 and valve 81 to pipe I1 and the catalytic cracking step, wherein these heavy polymers are depolymerized or cracked.

' Heavy material such as tar can be separated from the polymerization ei'lluent through pipe 00 and valve 0|, and light low boiling material can be separated and removed through pipe 92 and valve 03. When this stream has an appreciable content of unreacted polymerizable olens, at least a portion of the stream'mayr be passed to the l y polymerization step from pipe 02 through pipe and valve 95 to pipe 00. When this stream con- 1 tains paramns which can be dehydrogenated to' produce polymerizable oleilns, the material discharged through valve may be dehydrogenated in apparatus not shown, and the oleilns so produced-may be passed tolthe polymerization step 63 by being introduced through pipe 64. When the paraillns charged tothe dehydrogenation apparatus through pipe Il are lighter than'the ilnal gasoline range products and similar in molecular weight range to paramns passing through lpipe 92, thesenunreacted paramns may be passed to the dehydrogenation apparatus from pipe 02 through pipe 0l and valve 91 to pipe |0, andin this manner can be dehydrogenated within the apparatus shown.

When the composition of the polymerization Veliiuent is such that it can conveniently be sent catalytic dehydrogenation in.

premium motor fuel hydrocarbons from less desirable hydrocarbons inthe motor fuel range.

atively low octane number, such as a natural gasoline fraction comprising substantial amounts of normal hexane, heptane and/or octane, can be charged through pipe l0 and subjectedr to 'Ihe corresponding normal olens so produced are cracked in the presence of a depolymerization catalyst in 20, the oleiln products so produced being, in generallower boiling than is a desired motor fuel product and predominantly normally gaseous.I

In such a case, the eiiluent can'be passed .from 20 through pipe 33, pipe |05 and valve |00 to pipe 23 and the polymerization step 63 directly.

In 63 the lghtfolens are polymer'ized to hydrocarbons in the motor fuel range. The eflluent will comprise both unreacted parailins and olefin polymers and may be recovered as such through pipe 40 or through pipe 00. Since olei'lns have higher blending octane numbers than straight octane numbers, this eilluent which comprises a blend of oleilns in parailins can be used directly. -As the polymers are more highly branched than the oleiins initially formed by the dehydrogenation, this motor vfuelifraction has a higher octane rating than the'hydrocabon efiluent from dehydrogenation unit I! desired, the light oleflns may' be separated from the heavier paraftlns in 3i before the. polymerization operation, as has1-been"discussed.fand' other rdmodincations may-be made, vas .will be obvious. `IfJit is desired to hydrogenate adaptions a olens produced by any modication of our process, and produce a saturated product free of any unreacted parafiins 0'! similar boiling range, a

directly to the hydrogenation step, theV stream may be passed from pipe 00 through pipe 90 and 'valve 00 directly to pipe 30 and the hydrogenation apparatus 42. While we prefer to separate hydrogen and any heavy tar-like materials from the dehydrogenation el'liuent before catalytically cracking the oleilns contained therein, it is possible at time to operate the dehydrogenation process with practicallyv no production of tar or the like, and when using a depolymerization catalyst which will operate satisfactorily inthe presence of free hydrogen, the entire dehydrogenation eiiiuent may be passed directly to the catalytic cracking step. through pipes I2, |03, |01 and valve |08 to pipes 00 and I1, with-valves I3 andv |04 being closed. As discussed in our herelnbefore mentioned copending application, a motor fuel may be produced directly from propane and/or vbutane' by a straight-through process, which can be carried out bydehydrogenating in apparatus Il, passing theeiiiuent through pipes l2 and |03 and valve IN to Dives 00 and 2l', polymerizing in apparatus 63, passing the -eflluent through pipes 00, 08, and' 30, hydrogenating in apparatus 42, and recovering saturated motor fuel so produced from pipe 0|. with no interveningseparatlng steps.

,Our process also may be operated to produce vstream may be withdrawnfrom pipe l0 or pipe 00, oleiins may -be separated from paraillns as by selective solvent extraction or the like, known to the art and concentrated oleiins may be hydrogenated bybeing introduced through pipe 45.

In any modiiication or adaptation, when low boiling oleilns are separated in a relatively concentrated fraction from the emuent of the catalytic cracking step, they may-be converted to motor i'uel by a modiilcation of catalytic Polymerization which involves catalytic reaction with some other type of hydrocarbon to produce a premium motor fuel range product, as by an alkylation reaction with isoparailins in the presence of concentrated sulfuric acid, o'r other alkylation catalyst, as previously discussed.

Example I The following is cited as an example of the operation of our process as adapted to .crack heavy polymers produced during the polymerization of normally gaseous oleiins to form motor.

y fuel range hydrocarbons.

A :normally gaseous hydrocarbon mixture of the following composition was charged to a catalytic polymerization step.

This material was polymerized undera 'pxessure of about 1500 pounds'per square inch in the presence of a silica-alumina catalyst prepared by treating a partially dried hydrous silicagel with a tive per cent aluminum sulfate solution at a temperature near the boiling point of the treating solution, washing the treated gel withy water, and subsequently drying it. The polymery 1 The composite polymer produced after 2.89

hours of operation had the following composition:

l Percent by weight C5 8.9

B. P. `sos-40o" F as B. P., 400 F.. 11.7

C: and lighter A portion of thomatonn boiling above 365 F. was catalytically cracked by being passed over a silica-alumina depolymerization catalyst at a temperature of '710 F. and approximately atmospheric pressure at a rate of 1.63 volumes of liquid per volume of catalyst per hour. Another portion of the' same material'was subjected to noncatalytic cracking at approximately atmospheric pressure, a temperature of 1022" F. and a contact time of 4.6 seconds in the cracking chamber. The results of these twoA cracking runs were as follows:

Yields (per cent by weight) Thermal Catalytic Composition of gas (per cent by volume) Thermal Catalytic The fact that much 'morev gaseous material was produced by the catalytic cracking, at an appreciably lower temperature, and that this gaseous material contains very little material lighter than propene and very little saturated material is f quite striking, and brings out a distinct advantage of our invention.

Example II Thefollowingis cited as an example of the operation of our process as adapted to crack nonpolymeric oleilns. Normal heptene such as is oba silica-alumina catalyst/ maintained at a temperature just under 400 F. The ilow ratev was 0.72 volume of liquid normal heptene per volume of catalyst per hour, and the absolute pressure was about atmospheric. The ei'iiuent had the following composition.

Mol per cent 0 0 c, 111s C4 1.2 'Cs 1.2 Co (Predominantly C'zH'n) 85.8

Over 98 per cent'of the Cs fraction/was propylene, and over 30 per cent of the'C4 fraction was butylenes.' These light gasesvare readily catalytically polymerized to produce a Imotor fuel superior as to antiknock characteristics as compared with the normal heptane corresponding to the original normal heptene.

Example m A parafilnic-base crude oil had the following analysis, derived from a simple distillation test.

The straight run gasoline fraction had an octane number of 45.6, a gravity of 57.5 A. P. I., and a Reid vapor pressure 014.15 pounds. The kerosene fraction may be dehydrogenated by being passed at a temperature between 950 and 1000 F. over a granular catalyst comprising unglowed chromium oxide at a pressure of about 25 r pounds per square inch gauge and at a flow-rate of about two liquid volumes per volume of granular catalyst per hour. The light gases contain only about 10 per cent methane and other light hydrocarbons,v being predominantly free hydrogen. The liquid hydrocarbons have substantially the same'boiling range as the initial charge stock and contain about 16 per cent oleilns. This oleiln-containing material is passed over fullers earth, which has been activated by treatment with hydrogen chloride, at a temperatureV of about 775 F. and a pressure oi' about 20 pounds per square inch and a flow rate of 1.3 liquid volumes per volume of catalyst per hour. The emuent is fractionated into a gaseous fraction comprising propylene and butylene, a fraction comprising normally liquid hydrocarbons boiling be' l straight run gasoline and 20 per cent of the gasoline produced by the catalytic cracking has an `octane number of 58. The vgaseous fraction is `polymerized in the presence of a silica-alumina catalyst to produce a motor fuel which, after hydrogenation, has an octane number of 88, and

has an octane number of 100 by the Army meth- ,iod upon the addition oi 1.3 cc. of tetraethyl lead uid.

Manymodifications and variations of this invention may obviously be used, and can be adapted byone skilled in the art without departing -ticular'case by anyone skilled in the art. ever, the essential equipment and conditions have used in Fthe examples, and in connection with the drawing, need not necessarily be used as limits for any particular operation or set of conditions, as they are presented primarily as illustrative examples. While it Will generally be desirable to practice our invention as a continuous process, it may be practiced in an interrupted manner, or

otherwise, as conditions or circumstances may,

warrant or indicate. It will be understood that the iiow diagram presented and described as a part of the disclosure is schematic only, and that many additional conventional pieces of equipment, such as pressure gauges, valves, pumps,

heat exchangersreiiux lines and accumulators, Y heaters and coolers, and the like, will be necessary for .any particularinstallation, and can be supplied to meet the requirements for any par- Howbeen described and the modiiications discussed in suillcient detail to serve as efllcient guides;

We claim':

1,'A process for converting paraiilnic hydrocarbons boiling above the lower part of the gasoline boiling range into ,hydrocarbons of a smaller y 2,849,160 Y from the spirit ofthe disclosure. The restrictions quate to produce lower boiling olens therefrom and at a ilow ratebetween 0.25- and 10 liquid volumes of Ysaid hydrocarbon per volume of catalyst per hour and such that corresponding saturated hydrocarbons are substantially inert atsaid pressure and temperature.

4. In a process for producing lower molecular weight hydrocarbons from hydrocarbons of.

higher molecular weight', the step which comprises contacting a normally liquid, nonpoly-l meric normal oleiin hydrocarbon with a solid silict-alumina depolymerization catalyst at a pressure lessl than 100 pounds per square inch and a temperature between 400 and 1050 F. and adequate to produce lower boiling oleilns therefrom and at a ow rate between 0.25 and l0 liquid volumes of said hydrocarbon per volume of catalyst per hour and such that corresponding saturated hydrocarbons are suUstantially inert at said pressure and temperature.

5. A process for' converting paramnic hydrocarbons boiling above the lower part of the gasonumber of carbon atoms per molecule and in the gasoline boiling range, which comprises subjecting such a paraiiinic hydrocarbon material to dehydrogenation in the presence of a solid dehydrogenation catalyst to produce oleilns and free hydrogen without substantial' cracking, subjecting a fraction comprising oleflns so produced in the presence of. a solid depolymerization catalyst toconditions of time, temperature and pressure adapted to crack said olefins to produce a substantial portion of hydrocarbons of a smaller number of carbon atoms per molecule and in the gasoline boiling range along with lighter oleiins having at least three carbon atoms per molecule,

passing the eiiluent to a separating zone, removing from said separating zone a fraction comprising said lighter oleflns having at least three carbon atoms per molecule, subjecting said lighter olens to catalytic polymerization to form hydrocarbons in the gasoline lboiling range and passing the eiiiuent to said separatingzone, and removing from said separating zone a hydrocarbon fraction comprising hydrocarbons in the gasoline boiling range produced byl said cracking and by said polymerization.

2. A process for producing lower boiling hydrocarbons boiling in the motor f uel range from higher boiling nonpolymeric oleiin hydrocarbons, which comprises subjecting a hydrocarbon material comprising a. substantial proportion of heavy nonpolymeric olefin hydrocarbons to the action of a granular silica-alumina catalyst, prepared by activating a hydrous silica gel with an aluminum salt solution, at a temperature be- 'tween 400 and 750'? F. under a pressure not inV excess of about 100 pounds per square inch and per hour, and subsequently separating a hydrocarbon fraction containing lower boiling hydrocarbons in the motor i'uel range so produced.

3.' In a process for producinglower molecular weight hydrocarbons from hydrocarbons oi higher` molecular weight, the stt; which comprises contacting a normally liquid, -nonpoly meric oleiln hydrocarbon with a solid silica- -at a now rate between 0.25 and 4 liquid volumes l of hydrocarbon material per volume of catalyst alumina depolymerization catalyst at a pressure less than 1001pounds per square inch and a temperature between 400 and 1050 F. and adeline-boiling range into hydrocarbons of a smaller number of carbon atoms per molecule and in the gasoline boiling range, which comprises subjecting such a paraillnichydrocarbon material to dehydrogenation in the presence of a solid dehydrogenation catalyst to produce oleilns and free hydrogen without substantial cracking.

subjecting a fraction comprising olens so produced in the presence of a soliddepolymerization catalyst to conditions .of time, temperature and pressure adapted to crack said oleiins to produce`a substantial portion of hydrocarbons of a smaller number of carbon'atoms per molecule andv in the gasoline boiling range along lwith lighter oleiins havingat least three carbon atoms per molecule, passing the eiliuent to a separating zone, removing from said separating zone a fraction comprising saidlighter olefins having at least three carbon atoms per molecule, subjecting said lighter olerlns to catalytic polymerization to form hydrocarbons in the gasoline boiling range and above the gasoline boiling range, passing eiliuents of said polymerization to said separating zone, removing from said separating zone an olefinic fraction above the gasoline boiling range comprising oletln polymers produced in said polymerization and subjecting said fraction to said depolymerization catalyst in ad- -mixture together with said olen fraction resulting from dehydrogenation, and removing also from said separating zone an oleiinlc hydrocar- .bon fraction comprising hydrocarbons in the polymerization` catalyst to conditions of time,

temperature and pressure adapted to crack said oleiins to produce a substantial .portion of hydrocarbons of a smaller number ol' carbon atoms per moleculeand in the gasoline boiling range along with lighter oleiins having at least three carbon' atoms per molecule, passing the eiiiuent alsfiaieo boiling range, passing eilluents of said polymeri zation 4to said separating zone, removing from said separating zone an oleiinic fraction above the gasoline boiling range comprising oleiin4 polymers produced in .said polymerization and subjecting said fraction to said depolymerization catalyst in admixture together with said olefin flraction resulting from dehydrogenation, removing also from said separating zone an oleflnic hydrocarbon fraction comprising hydrocarbons in the gasoline boiling range resulting from said cracking of oletlns and from said polymerization, and hydrogenating the last said oleiinic fraction with hydrogen produced by said dehydrogenation to saturate olenic hydrocarbons contained therein.

7. The'process of claim 3 in whichI said solid silica-alumina depolymerization catalyst has been preparedl by treating a hydrous silica gel with an aluminum salt solution and subsequently washing and drying the resultant material, and contains not more than .above ve per cent alumina.

8. A process for the production of hydrocarbons predominantly in the boiling range of vgaso weight, which comprises subjecting said oleiin hydrocarbons to catalytic polymerization separating from the eiliuent of the polymeigzation step polymers boiling i n the gasoline range and polymers boiling above the gasoline range. passing at least a portion ot the polymers -Loiling above the gasoline range in contact with a solid depolymerization catalyst comprising mixed y aluminaand silica gels under such conditions of time, temperature and pressure that the depoiy- 'meriz'at'ion reaction produces a substantial pmportion of gasoline boiling range hydrocarbons and olefinic gases, and recycling the oleflnic gases to the-polymerization step.

9. A process for the production of hydrocar-4 bons predominantly in the boiling range of gasoline from olefin hydrocarbons of lower molecular weight, which comprises subjecting said olen hydrocarbons to catalytic polymerization, separating from the effluent of the polymerization step polymers boiling inthe gasoline range andpolymers boiling above the gasoline range, passing at least a portion of the polymers boiling above the gasoline range in contact with mixed alumina and silica gels under such conditions of 5 time, temperature'and pressure that a -depolyline from oleiln hydrocarbons of lower molecular l m'erization reaction produces a substantial proportion of gasoline boiling range hydrocarbons and oleiinic gases, and recycling the olenic gases to the polymerization step.

FREDERICK E. FREY. ROBERT D. sNow. WALTER E. HUPPKE.

. CERTLFICATE o F coRREc'I'AIoN.I Patent No'. 2,5L|.9,16o. may 15, 19141 FREDERICK E'. FREY, ET '.AL.

It is hereby certified that error appeers 1n the print-ed specification of the above numbered Vpatent: lrequiring correction as follows: Page 2, flrst column, line 50, before the word "best" insert be; and second `column, 1 1ne 6, for "dehydrogenize" reed -dehydrogenate; page 5, second column, line-15, for "No, 10,697 read --NQ.-1o6,6'97;and that the" 1d Letters Patent should be rend with this correction therein that the seme may con-- fom to the record of the -case in .the Patent Office. v

Y Signed and sealed this v 12th day. of ,Septiembem A. D. 191411,."

Leslie Frazer (Seal) I Acting Commissioner of Paten-ts.

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