US2428715A - Catalytic cracking of hydrocarbons - Google Patents

Description

Oct. 7, 1947. M. M. MARlslc QATALYTIC CRACKING OF HYDOCARBONS Filed Sept. 8. 1944 :C 2o@ Shun@ .u FWGEU T nma I# N/ Ndonm Qwvhow I' m SQ a.. m M m S mu n *n eowwlv# I' n wh 0 o. nu *u u umQNW |IFII||- W ./.ns N ERS @25 1 un I1 awmwN T n h N W -ir n Q mm, Y n* @n u S52,

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Patented Oct. 7, 1947 UNITED STATESl PATENT-OFFICE CATALYTIC CRACKIN G F HYDROCARBONS Milton M. Marisic, Northfield, Ill., assigner to The` Pure Oil Company, Chicago, Ill., a corporation of Ohio Application September 8, 1944, Serial No. 553,148

(Cl. ISG-49) 3 Claims.

alyst, resulting in rapid degradation of the catalyst and necessitating long regeneration periods and peak reactivating temperatures which reduce and sometimes completely destroy the activity of a catalyst. The practice of subjecting the recycle stock from catalytic cracking operations to purely thermal cracking is not entirely satisfactory for the reason that purely thermal cracking of such stock results in large yields of light hydrocarbon gases and production of motor fuel having a lower octane rating than motor fuel produced in the catalytic cracking operation.

I have discovered that the insuiiiqiently cracked oil or recycle stock from any known type of catalytic cracking operation utilizing either a natural or synthetic siliceous catalyst, such as activated clay or co-precipitated silica-alumina, can be satisfactorily cracked by contacting it at cracking temperature with activated carbon. By cracking conventional catalytic recycle stocks in the presence of activated carbon, the resulting motor fuel has an octane number substantially equal to that obtained on conventional catalytic cracking processes and the catalyst can be repeatedly regenerated without effecting its activity. In addition, coke is formed which may be used for heating purposes in the process or for extraneous use.

An object of the invention is to provide a method for cracking recycle stock or insufficiently cracked oil from conventional catalytic cracking processes using siliceous type catalyst.

Another object of the invention is to provide a method for simultaneously producing coke and manifest from the following description and the accompanying drawing of which the single figure is a diagrammatic, elevational viewof apparatus suitable for carrying out my invention.

Referring to the drawing, insufficiently cracked hydrocarbons or recycle stock from a converttional catalytic conversion step such as a fixed' bed, moving bed or a fluid catalyst operation utilizing a natural or syntheticsiliceous catalyst is charged through line I by means of pump 2 into line 3 which leads to furnace 4 wherein the charge is vaporized and superheated. The superheated vapors from furnace 4 pass into line 5 and commingle with the i'lnely divided activated carbon catalyst admitted through line 6. The resultant suspension of catalyst in oil vapors enters reactor 1 which may be maintained at a temperature of 800 to 1000 F. and at a pressure ranging from a few pounds'above atmospheric to several hundred pounds per square inch'.- Catalytic conversion of the charged hydrocarbons is effected on passage through the said reactor. The conversion products and the spent carbon catalyst, containing on its surfaces a catalytically inactive hydrocarbonaceous deposit, pass out of reactor 1 through line 8 into separator 9 which may be of the cyclone type and serves to separate coarse particles of spent catalyst from the hydrocarbon vapors and the finely divided spent catalyst. The latter mixture leaves separator 9 through line III and is conducted into a second separator Il. The coarse particles of spent catalyst in separator 9 pass through line I2 and valve I3 into catalyst hopper I4 wherein the spent catalyst is purged free of volatile hydrocarbons with superheated steam, at approximately cracking temperature, which enters vessel I4 through line I5 and valve I6. Hydrocarbon vapors, superheated steam and a small amount of catalyst powder pass out of I4 through valve I'I and line I8 and through line 8 into separator 9, while the coarse catalyst freed of adsorbed volatile hydrocarbons is removed through valve I9 and line 20.

The hydrocarbons separated from the nely divided spent catalyst in separator II are conducted through line 2| to fractionating column *.22 Where gasoline and lower boiling hydrocarhigh octane motor fuel from catalytic cracking recycle stocks.

Still another object of the invention is to condition recycle stocks from conventional catalytic4 cracking operations so that the stock may be recycled to the catalytic operation for conversion into motor fuel.

Other objects of the invention will become bons are segregated from the recycle stock. The recycle stockA is removed from column 22 by valve 23 and line 24 and line 21 and thus is recycledthrough the conversion system to extinction; or the recycle stock may be withdrawn through line 25-a and valve 25-b and utilized as a cracking stockin the, same catalytic cracking operation from which fresh charging stock' is derived for charging to line I. The hydrocarbons having the greatest tendency to yform coke are removed during the catalytic cracking with activated carbon and therefore can be satisfactorily cracked in the presence of a siliceous cracking catalyst. If desired, a portion of the recycle stock removed from column 22 may be recycled and a portion charged to a conventional catalytic cracking process or withdrawn for other disposal.

Gasoline and lighter hydrocarbons leaving column 22 pass through line 28 into stabilizer 28 from which gasoline of the desired vapor pressure is removed through valve 38. This gasoline is characterized by its high anti-knock properties which are substantially superior in value to those possessed by `motor fuels produced by thermal cracking at similar operating `conditions in the absence of a cracking catalyst. The fraction lighter than gasoline is withdrawn through lme 3 I, condenser 32 and line 33 and gas separator 34. Uncondensed material (boiling below propane) is removed through line v35, while the -condensate composed chiefly of C3 and C4 hydrocarbons are withdrawn through valve 36, line 31 and valve- 38. A portion of 'the liqueed hydrocarbons may be returned as reflux to column 28 through valve 38, pump 40 and line 4I. Separator 34 is placed above stabilizer 29in the drawing merely for convenience. VActually these vessels would be on approximately the same level.

The spent catalyst from separator II passes through valve 42 to catalyst hopper 43 where volatile hydrocarbons adsorbed on the catalyst are removed by purging with super-heated steam, heated to approximately SOO- 1000 F., which enters hopper 43 through valve 44. From hopper 43'the volatile hydrocarbons and steam are conducted through valve 45 and line 46 to separator I I. `A portion of the adsorbed hydrocarbons will be removed from catalyst in separators 8 and Il, by the superheated steam charged thereto from catalyst hoppers I4 and 43. The purged catalyst from 43 is introduced through valve 41 into heat treater 48, which is maintained at a temperature of about 1000 to l200 F. Heating may be effected by external or internal heating means or may be eected in whole or in part by passing heated air or oxygen-containing gas in contact with the spent catalyst in amount sumcient to generate the required amount of heat.

The purpose of treater 48 is to effect desorption and/or decomposition of heavy hydrocarbons present in the hydrocarbonaceous deposit formed on the catalyst during the cracking reaction and thereby either remove these hydrocarbons or decompose vthem to carbon. Such hydrocarbons are not` removed y during steam purging. This heat treatment is essential in order to obtain most eiiicient and complete reactivation of the catalyst with steam or the like in the subsequent revivication step. Omission of the heat treating step, not only unduly prolongs the regeneration with steam, but results in a poor cracking catalyst.

During the heat treatment of the catalyst in 48, gases are evolved which carryvwith them some of'the nely divided catalyst.` These gases are conducted through line 48 to separator 50. Hydrocarbon gases are'removed therefrom by line 5IWhile the catalyst is returned to treater 48 through valve 52 and line 53. The heat treated catalyst leaving 48 through valve 54 and line 55 is picked up in line 5G by superheated steam or other reactivating gas and thereby the catalyst ator 51.

The coarse catalyst from hopper I4 may be pulver-ized and utilized as fuel to furnish heat for treater 48, Aor when the formation of coarse particles in the operation is excessive so that the supply of powdered catalyst in the system is depleted, all or a portion of the pulveri'zed catalyst may be returned to the process after reactivation in 48 and 51.

In starting the initial operation of the process of this invention, activated carbon lfroniany source-may be utilized. The activated rcarbon may be a readily available commercial product or may be prepared Yspecially vby carbonization rof waste-pulp liquors lignite, wood, saw-dust, coal,

petroleum oils, `e c. After lcarbonization, the Y product is further treated at 1000 to 12,00,F`

with air, oxides of carbon, chlorinasuperheated steam, or mixtures of steam and air to formche activated carbon catalyst. Ifl desired, the carbonizedV material may be impregnated with acids such as hydrouoric, hydrochloric. sulfuricfphosphoric and/or s alts like sodium carbonate,- calcium chloride, magnesium chloride, vinorderto facilitate the steam activationlstep.and/orto yield a more active carbon catalyst. Furthermore, the activated carbon lcatalyst may be impregnated with inorganic cracking Acatalysts which are soluble in water or dilute acids sothat a cracking catalyst is formed whose activity is due tothe combined activities of the activated carbon and the inorganic compound. For. example, inorganic compounds suitable as cracking catalysts are zirconium sulfate, sodium tungstate, sodium pyrophosphate, and aluminumsulfate. The compound may be recovered from the spent catalyst by solution in water followed by crystallization from the aqueous solution.

In the reactivation of the spent catalyst, temperatures of reactivation should be as high as possible without resulting in permanent destruction ofthe catalyst. Suitable temperatures are between 1000 and 1200 F. Care should be exercised not to permit the temperature to get `so high as to convert the carbon to the graphitic form since in this form carbon is inactive cata.- lytically and it is impossible to convert this form of carbon to the active state.

the carbon should be carried tosuch an extent that Vwhen an East Texas oil having an A. P. I. gravity of 37 and a boiling range of approximately 430 to 700 F. is cracked in the presence of the catalyst at a weight ratio of one pound ofoil to .575 pound of catalyst over a thirty minute period and at a temperature of 850 F., at least ten percent of the gas oil will be converted to gasolineboiling hydrocarbons. In general, reactivation should be conducted so that the catalyst is capable of converting over twenty percent of the gas oil to gasoline-boiling hydrocarbons under the conditions above specied `and if regeneration is properly conducted, the catalyst will be capable of converting thirty percent or ,more of the gas oil to gasoline-boiling hydrocarbons. Under similar conditions in the absence of a Reactivation oi! 5 catalyst, the amount of gas oil converted to gasoline is less than ten percent.

After the initial charge of activated carbon is made to the operation, it is unnecessary to add additional catalyst since the depositions of coke on the catalyst during the cracking operation is activated during the regeneration cycle and increases the total amount of catalyst in the system thereby necessitating withdrawal of a portion thereof through line 20.

It will be seen, therefore, that I have succeeded in providing a method for cracking recycle stocks from conventional catalytic cracking operations in a manner such as to obtain additional yields of gasoline of substantially the same octane number as gasoline prepared by conventional cracking processes without permanent injury to the cracking catalyst.

I have also succeeded in providing a method for producing coke which may be used for heating in the process or for other purposes and I have succeeded in producing a residual oil product which is suitable for charging to conventional cracking processes yor which can be continuously recycled until it'is completely converted into high octane motor fuel, coke and gaseous products which contain components suitable .for conversion by alkylation and/or polymerization into gasoline.

It is claimed:

1. A process for converting insuiilciently cracked liquid hydrocarbons from a cracking operation in which siliceous catalyst is used to crack fresh charging stock, to gasoline-boiling hydrocarbons of high anti-knock properties comprising vaporizing said hydrocarbons, suspending comminuted activated carbon in said vapors, said activated carbon' being capable of cracking at least ten percent of East Texas gas oil having an A. P. I.` gravity of 37 and a boiling range of approximately 430-700" F. to gasoline at 850 1". when said oil is cracked in the presence of the activated carbon in a weight ratio of one pound of oil to 0.575 pound of catalyst over a thirty minute period, subjecting a mixture of only saidvapors and the hereinafter mentioned liquid product boiling above the gasoline boiling range and suspended activated carbon to temperatures of approximately 800-1000 F.. until a substantial portion of said hydrocarbons are converted to gasoline-boiling hydrocarbons, separating coarse carbon particles from the remaining products oi reaction and eliminating them from the sys tem, separating fine carbon particles from hydro'- carbon reaction products, regenerating the separated fin'e carbon particles by contact with superheated steam at temperatures of approximately 1000 to 1200 F., recycling the regenerated insufficiently cracked hydrocarbons first men' tioned above and recycling liquid product boiling step.

2. A process for converting mineral oil into high octane gasoline comprising charging freshoil only to a siliceous catalyst cracking step, subjecting said oil in said step to conditions of time, temperature and pressure to crack a substantial portion thereof to gasoline, separating the cracked material into gasoline and insufilciently cracked stock, contacting said insuillciently cracked stock in a cracking zonel with activated carbon under suitable time, temperature and pressure cracking conditions, said activated carbon being capable of cracking at least ten percent of East Texas gas oil having an A. P. I. gravity of 37 and a boiling range of approximately 430-700 F. to gasoline at 850 F. when said oil is cracked in the presence of the activatedycarbon in a weight ratio of one pound of oil to 0.575 pound of catalyst over a thirty minute period, 4:separating spent carbon from the efliuent from -said cracking zone, separating reaction products from said cracking zone into high octane gasoline and insufficiently cracked heavier hydrocarbons, regenerating at least a part of the spent carbon catalyst and recycling it to said cracking zone, said insufficiently cracked stock from said siliceous cracking step and said insuiilciently cracked heavier hydrocarbons from the activated carbon cracking zone being recycled only to said cracking zone. i

' 3. Process in accordance with claim 2 in which the spent carbon catalyst is regenerated with steam at approximately 10001200 F.

MILTON M. MARISIC.

REFERENCES CITED The following references are of `file of this patent:

UNITED s'rA'rEs PATENTS France Nov. 9, 1928 above the gasoline boiling range to the conversion record in 'the

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