US2436257A - Conversion of hydrocarbons - Google Patents

Description

Patented Feb. 17, 1948 CONVERSION OF HYDBOCARBONS Rowland 0. Hansford and Alexander N. Sachanen, Woodbury,-N. J., assignors to Socony- Vacuum Oil Company, Incorporated, a corporation of New York No Drawing. Application August 9, 1944, Serial No. 548,786

This invention relates generally to cracking of petroleum stocks, and is more particularly concerned with a method of catalytic cracking of petroleum stocks, whereby the yields of hydrocarbons boiling within the gasoline boiling range, are substantially increased.

Cracking is a well known chemical process and generally connotes operations for converting heavy hydrocarbon molecules into light hydrocarbon molecules. The decomposition or the breakdown of the heavy hydrocarbon molecules into lighter ones, is accompanied by the concurrent formation of even heavier hydrocarbon molecules and by the production of solid material referred to as coke. Cracking was originally carried out non-catalytically, at temperatures of the order of 7501l00 F. with the charge stocks mostly in the liquid phase. However, due to the demand for anti-knock gasoline, and since the motor fuels produced by catalytic cracking operations, possess anti-knock properties superior to those of motor fuels produced by non-catalytic or thermal cracking, catalytic cracking soon came into prominence. The development of aviation soon created a demand for motor fuels having not only anti-knock characteristics superior to those of motor fuels produced by thermal cracking, but possessing also morev desirable overall properties and, particularly, a greater stability with reference to gum formation during use and storage.

It is well known to those familiar with the art, that catalytic cracking of petroleum stocks has been carried out mostly in the vapor phase and 3 Claims. (Cl. 196-52) having desired boiling ranges. As a consequence, the supplyof available catalytic cracking stocks is restricted.

As is well known in the art, even recycle stocks obtained from the catalytic cracking of non-refractory petroleum cracking stocks, are not suited to recycling to the catalytic cracking zone to be subjected to the catalyic cracking operation per se or in conjunction with the charge stocks, due to their somewhat refractory nature. Accordingly, these recycle stocks frequency have been processed separately, in thermal cracking operations, as distinguished from cracking operations wherein cracking catalysts are employed. As noted hereinbefore, gasoline produced by catalyticcracking operations is somewhat superior to gasoline produced by thermal cracking operations. Hence, and in view of the foregoing, only a moderate portion of the total yield of hydrocarbons boiling'within the gasoline boiling range, may be ob- The present invention is to be distinguished from those processes for the production of arcmatic hydrocarbons from the cracking of petroleum oils, wherein in order to minimize the production of benzene in preference to alkyl aromatic hydrocarbons, the concentration of henzene is increased above that produced by the normal formation of benzene in the cracking zone. The present invention is not directed to a process for the production of aromatic hydrocarbons or of cyclic hydrocarbons, but rather, it is directed to an improved catalytic cracking operation for the production of high yields of hydrocarbons boiling within the gasoline boiling range. It must be noted that the gasoline produced in accordance with the present invention, is the somewhat superiorproduct or that resulting from catalytic cracking operations.

Accordingly, it is an object of the present invention to provide a method for converting heavy liquid hydrocarbons into light, normally liquid hydrocarbons. Another object is to provide an improved method of catalytic cracking. A further object is to afiord an eflicient method for efiecting the catalytic cracking of petroleum stocks of a refractory nature. A very important object is to provide a method of catalyticcracking, where.- .7

object is to provide a method of catalytic cracking capable of carrying out the foregoing objects by subjecting petroleum cracking stocks'to cat-' alytic cracking in the presence ,ofthermally-stable aromatic hydrocarbons. Othenobjects and advantages of the present invention will become ap-' liquid hydrocarbons -.under cracking conditions,

with'acracking catalyst, inthepresence of an added aromatic hydrocarbon .that is thermally stable under said cracking. conditions.

According to ourinventiomany aromatic hydrocarbon which is 'stableat the temperatures mdinarily used in thermal and catalytic cracking operations, is suitable for our purpose. Benzene, meihylbenzene,naphthalene, and diphenyl may be mentioned byway of non-limiting'examplesol the aromatic hydrocarbons employed.

In the preferred embodiment of our invention, we use'benzene as the-thermally stablearomatic hydrocarbon. Accordingly, benzene may be charged together with the petroleum cracking stock, intothe cracking-zone. I In the cracking zone, thestock is subjected to-the cracking conditions and converted in the desired manner. The benzene vapors emerge from the cracking zone unchanged alongwiththe: products of the cracking operation, and together, they are sent through a fractional condensation system to condense the desired fractions of lower-boilinghydrocarbons thatihave been-produced, an'd also, a benzene fraction. .The benzene'fraction ordinarilyconstitutes a substantially complete recovery of benzene, and'thisfraction may be conveniently recycled to the cracking zonewith freshpetroleum cracking stock.

Generally speaking, the-conversion of heavy, normally liquid hydrocarbons into light, normally liquid hydrocarbons by pyrolysis, with or Without the use of cracking catalysts, at temperatures of the order of about 800 F. to aboutl100 F., and

at pressures determined by the phase of operadue'to the fact that the rate of cracking of these -latter stocks is rmuch higher than that of the 4 with the method of our invention, are any of the well known petroleum cracking stocks for thermal cracking or catalytic cracking operations, although the advantages of the method of the present invention, are more predominant when the heavier and more refractory petroleum cracking stocks are employed. For instance, benzene can be used to advantage in the cracking of heavy residua for the sole purpose of gasoline production. For example, the cracking of heavy petroleum residua, of the order of A. P, I. gravity 10 and lower, is performed with considerable difficulty because of excessive coke formation. The use of fractions from these heavy residua as the recycling stock for such cracking operations, does not .give .satisfactory results,.-since these fractions f,thems'elves;'have undesirable coke-forming properties. On the other hand, the use of other rrecycle stocks having higher A. P. I. gravity, for

such ,crackingoperations, is practically impossible '-'.,heavy-residua. Benzene, however, is highly re- :fractory and accordingly. does not form coke under-thecracking-conditions; as a matter of fact, benzene, actuallytends to diminish coke forma- .f-tion. .As stated hereinbefore, benzene can be recovered and recycled and, particularly because of its tendency to reduce coke formation, it constitutes an attractive additive in catalytic cracking processes wherepthec amount of coke deposit regulates the. requirements for catalyst regeneration.

.A feature .of themethodof the present invention, is that ,the yields: per pass :of hydrocarbons boiling within the gasoline-boiling range, other variables-such as temperature, contact time of the petroleum stock; inzthe catalyst bed, etc., remaining constant; are unusuallyhigh. Theprior art did notrsuccessiully crack heavy stocks under the temperature conditions of the present invention. Suchhigh:temperaturetconditions in the absence of. added-benzeneleadito very excessive coke and gas formation .with lresultant low yields of gasoi line.

Accordingly,=i=another feature of our method, is that severexcraeking. conditions may be employed. It is well known thatithe'octane number of motor fuels increases rapidly with increasing severity of-cracking. Howeven severe cracking conditions are normally avoided in conventional commercial operations due to practical considerations arising from excessive 'cokean'd gas formation. The use 0fi'bEI1Zne, aS -S8t forth hereinbefore, minimizes coke and gas formation; hence, our invention the present invention,it is our belief that benzene enters into the cracking reaction during the early stages ofthe operation, by functioning as a hydrogen and: alkyLradical 'facceptor," and is subsequently regenerated by dehydrogenation I and dea'lkylation.

A most important feature of this invention, is total chargeibenzene-l-stock) or or 0.167 based that b our method, catalytic cracking of refracon the cracking stock. Under similar conditions, tory stocks is rendered commercially feasible. but In the absence f n such a crackin Even extremely efr ctor stocks of the type stock would be so severely cracked that the yield duced in thermal cracking and reforming opera- 5 3g 5 3, 3; 33:32 gfii gz gggfifgig' tions gwes qiute satlsfactqy i of 9 I very high. The use of very severe conditions of as compared to those obtainable in processes of catalytic cracking suchv as F. and a space the prmr velocity of 0.167, in the presence of benzene, is To illustrate the methodof our invention and to 1 an advantage'ofthe method of our invention.

. Table II Stock: Recycle stock from runs 1 through? Catalyst: Activated clay I Iiecycle I volume Tem- Rate Gas Coke Gasoline Stock 210 Residuum Run 0 H pcra- L [L Wt. Wt. to 200 c. 300 0. 300 0. Sw N o. a ture, g Per cent Per cent Vol. Per Fraction I Vol. Per 6 H I F. Stock Stock c'ent Stock V01. Per cent Stock P 19 3 0? 1 .f

1 Benzene was carefully fractionated out of gasoline cut in range 70-95 0. and analyzed for purity. Impurities are included in gasoline yield and amount to about 10% of total gasoline cut. v

point out the advantages thereof, we set forth in These data illustrate the efiect of. benzene on Table I, II, III, IV and V, data obtained in carthe cracking of refractory stocks, n: this inrying out our method of catalytic cracking. stance, the recycle stock-from the-cracking of a Table I Stock: Naphthenic distillate for cracking" from Coastal crude A. P. I.=3u.2 I I 8p. gr. (so/00 F.=0.875 v r 1 I A. S. '1. M. distillation: f I I I. B. P.==440 F. 1 r Y l0%=468 F 50%=504 F 90%=555 F E. P.=584 F. Catalyst: Activated clay Recycle v I 'lcm- Rat Gas Coke Gasoline Stock 200- Residuum Run 3 Derajfi' Wt. Wt. to 200 0. 300 0. 000 0. f No. 2 ture, I Per cent Percent Vol. Per Fraction VoL'Per 6 3 L F. Stock Stock cent Stock Vol. Per cent Stock cent Stock m Brge $411 925 10/20 15. 0 4. 3- 51. 1 35.4 3. 9 '91. 5' 34:1 025 v/20 1.0 2. 0 Y 48.8 40.9 2.0 90.1 1:1 950 I 20/20 11. 6 2. 6 49. 6 42. 7 3. 4 96. 6 1:1 925 10/20 12.6 6.0 52.8 34.4 2.5 95.8 1:1 900 10/20 12. 0 5. S 54. 2 36. 7 2. 9 90. 2 2:1 Q 10/20 11. 4 5. 1 58. 7 30. 1 5. 2 95. 5 2:1 925 20/20 8.4 2.4 53.6 50.3 6.0 93.8

1 Benzene was carefully fractionated out of gasoline cut in range C. and analyzed for purity. Impurities are included in gasoline yield and amountto about 10%0i' total gasoline cut. I I II I The data in Table I- show that the yieldsiof typical cracking stock. The. yield per'pass of gasoline per pass, considering the temperatures .gasoline from this recyclestock is 88.2% as and contact times of the petroleum stock-inthe against 52.8% obtained ith thevirginstbck.

. I I Table In Stock: Dewaxed distillate I: I

A. P. I.=27.7

Sp. gr. (SO/60 F'.==0.889 I Oatalyst: Activated clay I Recycle I I Tem- I Gas Coke Gasoline Stock 200- Residuum ;?259' Run 0 H pera- .Wt. Wt. to 200 0. -300O. 300C. P i N c. 2 ture, i Per cent Per cent Vol. Per Fraction Vol. Per C F. I Stock Stock cent Stock Vol. Per cent Stock in gcent Stock i Benzene Was careinllyfractlonated out of gasoline cut in range 7095 C.and analyzed for purity. Impurities are included in gasol ne yield and amount to about 10% of total gasoline cut. I I v 1 catalystbed, are abnormally high; For example, These data show that the yields of gasoline iii- F run NO. '7 shows a gasoline yield-0f,58.7% per pass crease with. decreasing'severity. of cracking cone at 925 F. and-a space velocity;nice-based on 'Tdltluns, such'asshorter contact titties."

""S." U." V. at 210 Ed 53.1 eatalystz nctivatedclay 5 f- Recycle H Re. volume {Pai 1B8. I Gas poke gasoline Stocked) fnesidunm a Run C'Ho -pera-- LJL Wt Wt to-200 G. 300 C. 300 Per cent :No.; ture'g. Percent ..Per,'ecent "VoLEPer Fraction VoLPer PFQ, fg k. .Stock centStock; v neer .centstock gflgfi f cent Stock 11 1:1 92 12/20 17. 6 ll-I6 52. 8 l4. 4 l3. 6 99. 2 l2 1:1 950 20/20 16.6 10.2 46.4 15.6 20.4 p 97.6 13.0 2:1 925 20/20 10.0 8.0 58;!- 7 1652 21. 4 "97.8

I Benzene was carelully'irectionated out oi? gasoline cut in range 704)? C. and analyzed for purity. Impurities areincluded gwoline yield and-amount to about of total gasoline cut.

These data show :that the'yiel'ds of gasoline attic-hammer coonditions of catalytic cracking inincrease with decreasing severity of cracking cluding .a temperature varying between about conditions, in instance, lower temperatures. 800 F. and about 1100 F., with a catalyst pro- Table V emerg e1 gstgbkfrom D'e'Flore'z vapor pbaso cracking of'Miran'do crude.

A. S. T. M. distillation: 1. B 0 F.

Recycle C H Ref volume Tem- Rate Gas Coke Gasoline Stook:20u-= LResrduum Run Cm p ra- LIL we. Wt. to 200 0. 300" 0. 300 0. No. stock ture, Oat/hr. Per cent Per cent Vol. Per Fraction Vol. Per

F Stock Stock cent Stock Vol. Per cent Stock cent Stock in Charge l Benzene was carefully fractionated out of gasoline cut in range 7095 C. and analyzed for purity. Impurities are included in gasoline yield and amount to 'about l0% of total gasoline cut.

These data illustrate one cot-the most striking motingcrackingundersaid conditions of catafeatures of the method of our-invention, namely "lytic cracking.

that even extremely refractcrycharge.stocksgive 2. .A method .forcobtaining high yields-of hysatisfactory yields of gasoline. 7 45 drocarbons boiling within theug'asoline boiling The figures given on the recovery of pure *range from a recycle .petroleum' crackingstock benzene can be considered to be {quite reliable j=having an A. P. I. gravity of less than about 15, if the basic assumption that benzene doesnot which'comprises 'contacting amixtureconsisting contribute to gas and coke formation, is correct. essentially of said recycle petroleum cracking This assumption was verified by runs with benstock and added benzene, inamountsofat least zene alone and is valid at temperatures below abouteohe-half volume of addedtbenzene :to one about 950 F. and in the range of space rates volume of'--said"recyclepetroleum cracking'stock" indicated, under conditions .of catalytic icra'ckingjncluding This application is .a continuationsin-pa'rt of atemperature varying between about 800.F.andour copending .ap'p'licationi'Serial .Number 366,806, 5 about 51100. E, with acatalyst promotingcracke filedNovember23;'I940, now abandoned. ingunder said conditions of catalytic cracking.

Although the present invention has been 'de- 3. A method for obtaining high yields of hydroscribed in conjunction with preferred eiiibodicarbons boiling within the gasoline boiling range ments, it is to be understood that modifications from a recycleipetroleumcracking stock having and variations may be resorted to without de- 6 an A. P. -I.; .gravity oflless than about 15, which parting from the spirit and scope of the invencomprises"contacting -amixture consisting essention asthose-skilledintheart'willreadiiy under- 'tially"ofsaidrecycle petroleum cracking stock stand. t Such variations and modifications are and an added aromatic hydrocarbon selected consideredtoibe withinthe purview-andv scope of from thegroup consisting of benzene, alkyl benthe. appended claims. zenepnaphthalene, and 'diphenyl, in amounts of We claim: at least about one-half volume of added aro- .1...A.method.for.obtaining highyields of hydro- A matichydrocarbon to-cne-volume of said recycle carbons boiling within-the gasoline boiling range petroleum cracking stock, under conditions of from a recycle petroleum cracking stock having catalyticcracking including a temperature varyan A. -P.-I.gravity-of less-than about 15", which ing between about 800 F. and about 1100 F.,

comprises contactingamixtureconsisting essenwith :a, .catalyst promoting cracking under said tially of said recycle petroleum cracking stock conditions of catalytic cracking.

and added :benzene iin :amounts varying between RGWLAND C. *I-IANSFORD. about /2 atosabout 2'-.volumes% ofradded benzene to I ll. SACHANEN.

one volume 1.0! .wsaidirecycle.petroleum rcracking :75 :ms gu foubwin pagg) REFERENCES CITED Number The following references are of record in the file of this patent:

UNITED STATES PATENTS 6 Number Number Name Date 795,125

2.245.157 Pier et al. I June 10. 1941 Name Date Pier et a]. II Aug. 1'7, 1943 Marschner 1 Nov. 30, 1943 FGREIGN PATENTS Country Date France Mar. 4, 1936