US2526068A - Catalytic cracking of hydrocarbons - Google Patents

Description

Oct. 17, 1950 J. DELATTRE-SEGUY CATALYTIC cRAcxING oF HYDRocARBoNs Filed June 3, 1947 A 10mm/,1.9015

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cAiALif'TIo citAcKINo oF'HYDRoCARBoNs Jean Delaftre-Segy, Washington, D. YC.,"e`l,ssg`nor to Universal Oil ProductsY Company, Ill., a corporation of. Delaware Chicago,

Appiicstinn .uneaieia serial'No. "152,247

This invention relatste the eataiytlceracnng '5 Claims.- (ol. ieee-52) of hydrocarbons. It is' more particularly Vcilnerned with the Conversion of high boiling hydocarbons such as topped or reduced crudes'to high octane number gasolines by a two step process employing fluidized catalyst y In order te obtain a greater amount crgeseune r from a given amount 'of crude oil, it is necessary to crack the heavier or residual portions of the crude. To utilize these high boiling fractions as lcharging stocks for catalytic cracking processes', itV has been necessary in the pasty to remove the coke-forming constituents, such as asphaltenes and the like, by relatively expensive methods such as propane deasphalting, vacuum distillation, and steam distillation. Even then the resultant material often was found to be an undesirable charge stock, particularly in fluid catalyst systems, because it was difficult to vaporize and process, and because. it cracked` to excessive amounts of low grade products such as coke or gas when contacted with active, freshly regenerated catalyst. Y

I have invented an improvedeconomical process for cracking residual oils to good yields of gasoline without excessive production-of gas or coke, and with our prior treatment or removal of asphaltenes andthe like, from the oil.

1n one embodiment myinventie'nrelates te a process for the conversion of hydrocarbons which comprises separating a hydrocarbon oil containi- A ing intermediate and residual fractions of petroleum into la gas oil fraction and fa residual fraction, subjecting the gas oil fraction tothe action of hot, freshly regenerated cracking catallyst at cracking conditions in a flrst cracking step,

separating the catalyst Afrom the hydrocarbons in said step, passing thefcatalystso separated to a ents from Vsaid cracking steps, fractionating the In amore vspecific embodiment my invention relates to a process such as Vvthatdescfribed above further characterized in tnatrelatively severe crackingconditions are maintainedin the first cracking step and less severe cracking conditions are maintained in the second cracking step.

`Brieny'stetec, my invention, es' applied te e,

cracking'zprocessemploying fluid catalyst, com.

rprises distilling a hydrocarbon oil such'a-s' topped crude to separate a gas -oil and aliquid residue. y

The gas oil, being a rather refractory stockyis'y y used* to transfer hot, freshly regenerated crack-` fractory stream of heavy reflux condensate, produced as hereinafter described, after whichv the catalystin admixture with the more refractory oil is contacted with the liquid residue in a second cracking zone, at cracking conditions less severe than those maintained in the rst cracking zone. The temperature in this second crackingstep usually Will lie within the range of from. about 850 to aboutV 940 F. The catalyst fromthis 'zone is separated from the hydrocarbons, is passed to a regenerator wherein the carbonaceous deposits are burned therefrom, and the regenerated catalyst is returned to the first cracking zone. The hydrocarbon effluents from the cracking zones are combined, are fractionatedtoobtain a light V anda heavy reflux condensate boiling above the gasoline range, and at least a portion of the heavy reflux condensate is recycled to the second cracking step.

One of the advantages -of this process is the separation of a hydrocarbon oil containing .inter-` mediate and residual fractions lof petroleum intor a gas oil fraction and a residual fraction and the conversion vof these fractions into motor fuel cracking step, combining the hydrocarbon 'eillue same to obtain a light and a heavy reflux condensate boiling above the gasolinerange, and-re"- 'cycling at least a portion of the heavy reflux constituents by processing each fractionunder conditions of, temperature rand catalyst activity most favorable for that particular stock.v Since the virgin gas oil fractionis relatively refractory, it should be cracked at more severe conditions,

i. e., at a. fairly high temperature and Tin the ying zone I I.

residue is converted chiefly into gas and coke. Howevenat temperatures within theV range of from about 850 to 940 F. and in the presence of a partially carbonized catalyst and a somewhat lighter oil, the residue can be more selectively converted into motor fuel constituents. Contacting the hot, freshly regenerated catalyst from the first regeneration zone with heavy reflux condensate serves to lower the temperature of the catalyst and to deposit some carbonaceous material thereon, thereby lowering its activity and preparing it for subsequent contact with the liquid residue. The initial activity of the catalyst is not dissipated by this method of operation because said activity is utilized in cracking a portion of theheavy reiiux condensate.

Because the liquid residue has greater-cokeforming tendencies than the virgin gas oil, the catalyst passing from the second cracking zone to the second regeneration zone usually contains a greater amount of carbonaceous deposit than the catalyst passing fromthe rst cracking zone to thenfirst regeneration zone. As a consequence, the temperature in the second regeneration zone is higher than that in vthe first. This isadvantageous because the hotter catalyst from the second regeneration zone is used in the high Vtemperature cracking step and the cooler catalyst from the first regeneration zone is used in the lower temperature cracking step. This is one of the chief reasons for using two regeneration zones instead of a single, common regenerator.

Further advantages of my process will be apparent from the following description of the accompanying drawing which illustrates in conventional side elevation one form of apparatus in which the present invention may be accomplished. For purposes of simplification, certain auxiliary equipment such as condensers, reflux accumulators, and the like have been omitted .from the drawing, but it is to be understood that such equipment is to be used wherever engineer ing -skill dictates.

Referring now to the drawing, substantially gasoline-free crude 'oilis passed through line I containing valve 2V into fractionator 3 wherein ,the .vaporous gas oil fraction is removed overhead through line 4 `containing valves 5 and i9 and a liquidresidue removed asa .bottoms` product through line I5 containing valve l.

Hot regenerated catalyst in a fiuidized form `such as a powder or microspheres, present in regenerator 8, is passed through line 9 containing valve I0 into line 4 wherein it is picked up by the vaporous gas oil fraction from fractionator 3, and the resultant mixture is passed into crack- The temperature within this zone is maintained at from about 940 F. to about 1100o F. and the reaction time is regulated to give substantial conversion, i.e., from about 40 to about `85% conversion based on the gas oil charged thereto. In this zone some carbonaceous material is deposited on the catalyst thereby lowering its activity.

Any suitable metal' oxide cracking catalyst lsuch as silica-alumina, silica-zirconia,v silicaalumina-zirconia,v silica-magnesia, silica-alumina-rnagnesia, alumina-boria, and the like, may

may vbe employed. Y

A dense phase bed ofA solid catalyst particles is maintained in reactor II and is kept in a uidlike state of relatively high density by the hydrocarbons passingupwardly through the bed at a velocity which partially counteracts the force of gravity on the solid particles and brings about their hindered settling-within. the Adense phase fbed. Above thedensphaseibed inthe upper portion of theV reaction chamber a relatively light phase region having a reduced catalyst density is maintained, wherein the catalyst is substantially separated from the hydrocarbons by means of aseparator, such as a cyclone separator, not. shown on the drawing. The cracked products are discharged from the upper end oi reactor II through line I2 containing valve I3 and are directedthrough line I4 into fractionator The carbonized catalyst from reactor II is ,withdrawnfthrough line I6 containing valve I'I and flows downwardly and tcountercurrently to an upwardly flowing stream of stripping medium, such `as'steam, which'enters line yIt through line I8 containing valve L9. The stripped catalyst is passed into regenerating zone 20 wherein car- `bonaceous depositson-the catalyst are removed by oxidation. This is accomplished by passing an oxidizing gas, such as air, through line 2| containing`valve22 into the bottom of regenerator 20. 'he'airpasscfzs upwardly through the catalyst and leaves the regenerator via line 23 containingvalve A'243. Entrained catalyst particles are removed from the .air stream by means of a cyclone separator or the like, and are returned to the dense phase maintained in regenerator 20.

Hot regenerated catalyst from regenerator 20 is passed through line 25 containing valve 26 and is passed into line 2l wherein it is commingled with a recyclestream of heavy reflux condensate. The mixture of catalyst and condensate passes through; line21 into the'bottorn` of reactor 28 wherein is maintained a light and a'dense phase of solid catalyst particles ina manner similar to that describedin connection with reactor Ii. Liquid residue flowing through line 0 is injected intoY the lower.;,IJor-tionY of the densev phase in reactor 28. :,The temperature maintained in this reactor usually -lies within the range of from about 850 F. tol about 940 F. The conversion products, from' which Aentrained catalyst has been separated, are discharged from reactor 28 through line I4 and are directed into vfractionator I5. i v

The catalyst in reaction zone 28 is withdrawn through line 29 containing valvel 30 and is directed downwardlyv andcountercurrently to the upwardly flowing stripping medium `which enters line 29 through. line 3I containing valve 32. The catalyst ilowingthroug'h line 29 passes into re- -generator 8. The oxidizing gas employed for burning theV vcombustibles'onthe contaminated catalyst is supplied toregenerator through line 33 containingfvalve 313..' The flue gases are discharged from theupper end of the regeneratcr by means of-line 35 vcontaining valve 36 after being passed through suitable catalyst separation means. 1

In iractionator i5 the hydrocarbon effluents from the reactorsare'separated into several fractions. Gasoline and gaseous hydrocarbons are removed overhead from the fractionator through linev 31 containing :valve 38. JSA light reflux condensate is removed as aside cut through line 39 containing valve 40.. Ilfhis light reflux condensate is rather` refractoryand-,1vv hence, itusually not recycled to the cracking step. Because of its relatively high aromatic content, it is useful as a solvent, in the production of naphthalene, and the like. Heavy reflux condensate is Withdrawn from the bottom of fractionator I5 through line 21, pump 4|, and valve 42. A portion of this stream may be withdrawn to storage or other conversion processes through line 43 containing valve 44. In order to balance out the process, it may be desirable to pass a portion of the heavy reflux condensate to reactor Il or a, portion of the virgin gas oil to reactor 28. This may be done by utilizing line 45 containing valve 46 or line 41 containing valve 48, respectively.

In general, the pressures maintained on the reactors and regenerators will lie below 100 p. s. i.

and preferably below 50 p. s, i.

Although my process has been described in connection with a fluidized catalyst system, it is to be understood that it is also applicable to systems in which the'catalyst is transported as a compact moving bed.k

I claim as my invention:

1. A process for the conversion of hydrocarbons which comprises separating a hydrocarbon oil containing intermediate and residual fractions of'petroleum into a gas oil fraction and a residual fraction, subjecting the gas oil fraction to the action of hot, freshly regenerated cracking cata- Y lyst at cracking conditions in a first cracking zone, separating the catalyst from the hydrocarbons, passing separated catalyst from said cracking Zone to a rst regeneration Zone and therein burning the major portion, at least, of the carbonaceous matter therefrom, withdrawing regenerated catalyst from said first regeneration Zone and contacting the same with said residual fraction in a second cracking zone under conditions to convert a substantial portion of said residual fraction into gasoline, removing contaminated catalyst from said second cracking zone and introducing the same to a second regeneration zone,

separately removing the cracked vapors from said second cracking zone and supplying the same directly and without prior passage through said first cracking zone to a fractionating Zone, separating said gasoline from the cracked vapors in the fractionating Zone, regenerating said contaminated catalyst in the second regeneration Zone at higher temperature `than the catalyst in said rst regeneration zone, and supplying hot regenerated catalyst from said second regeneration zone to said first cracking zone.

2. The process of claim 1 further characterized in that said first cracking zone is maintained at a temperature of from about 940 F. to about 1100c F. and the second cracking zone at a temperature of from about 850 F. to about 940 F.

3. A process for the conversion of hydrocarbons which comprises separating a hydrocarbon oil containing intermediate and residual fractions of petroleum into a gas oil fraction and a residual fraction, subjecting the gas oil fraction to the action of hot, freshly regenerated cracking catalyst at cracking conditions in a rst cracking zone, separating the catalyst from the hydrocarbons, passing separated catalyst from said cracking zone to a rst regeneration zone and therein burning the major portion, at least, of the carbonaceous matter therefrom, transferring hot regenerated catalyst from said first regeneration zone to a second cracking zone, commingling reflux condensate, formed as hereinafter set forth, With the regenerated catalyst in transit from the regeneration zone to the second cracking Zone to reduce the temperature and activity of the regenerated catalyst, introducing said residual fraction to the second cracking zone and therein contacting the same with the regenerated catalyst of reduced temperature and activity under conditionsto convert a substantial portion of said residual fraction into gasoline, removing contaminated catalyst from said second cracking Zone and discharging the same into a second regeneration zone, separately removing the cracked vapors from said second cracking Zone and supplying the same directly and without prior passage through said rst cracking zone to a fractionating zone, separating said gasoline from the cracked vapors in the fractionating zone, regenerating said contarninated catalyst in the second regeneration zone at higher temperature than the catalyst in said first regeneration zone, supplying hot regenerated catalyst from said second regeneration zone to said first cracking zone, supplying the vapors from said first cracking Zone to said fractionating zone land withdrawing from the lastnamed zone a reflux condensate boiling above the gasoline range, and commingling at least a portion of said reux ,condensate with the hot regenerated catalyst in transit from said rst regeneration zone to said second crackingA zone as aforesaid.

4. The process of claim 3 further characterized in that said rst cracking zone is maintained at a temperature of from about 940 F. to about 1100 F. and the second cracking zone at a ternperature of from about 850 F. to about 940 F.

5. The process of claim 3 further characterized in thatthe vapors from said cracking zones are fractionated in said Vfractionating Zoneto separate light and heavy reux condensates therefrom and Aat least a portion of the heavy reflux condensate commingled with the hot regenerated catalyst in transit. from said first regeneration zone to said second cracking zone.

JEAN DELATI'RE-SEGUY.

REFERENCES I CITED The following references are of record in the le of this patent:

UNITED S'IA'I'ES PATENTS

Claims (1)

1. A PROCESS FOR THE CONVERSION OF HYDROCARBONS WHICH COMPRISES SEPARATING A HYDROCARBON OIL CONTAINING INTERMEDIATE AND RESIDUAL FRACTIONS OF PETROLEUM INTO A GAS OIL FRACTION AND A RESIDUAL FRACTION, SUBJECTING THE GAS OIL FRACTION TO THE ACTION OF HOT, FRESHLY REGENERATED CRACKING CATALYST AT CRACKING CONDITIONS IN A FIRST CRACKING ZONE, SEPARATING THE CATALYST FROM THE HYDROCARBONS, PASSING SEPARATED CATALYST FROM SAID CRACKING ZONE TO A FIRST REGENERATION ZONE AND THEREIN BURNING THE MAJOR PORTION, AT LEAST, OF THE CARBONACEOUS MATTER THEREFROM, WITHDRAWING REGENERATED CATALYST FROM SAID FIRST REGENERATION ZONE AND CONTACTING THE SAME WITH SAID RESIDUAL FRACTION IN A SECOND CRACKING ZONE UNDER CONDITIONS TO CONVERT A SUBSTANTIAL PORTION OF SAID RESIDUAL FRACTION INTO GASOLINE, REMOVING CONTAMINATED CATALYST FROM SAID SECOND CRACKING ZONE AND INTRODUCING THE SAME TO A SECOND REGENERATION ZONE, SEPARATELY REMOVING THE CRACKED VAPORS FROM SAID SECOND CRACKING ZONE AND SUPPLYING THE SAME DIRECTLY AND WITHOUT PRIOR PASSAGE THROUGH SAID FIRST CRACKING ZONE TO A FRACTIONATING ZONE, SEPARATING SAID GASOLINE FROM THE CRACKED VAPORS IN THE FRACTIONATING ZONE, REGENERATING SAID CONTAMINATED CATALYST IN THE SECOND REGENERATION ZONE AT HIGHER TEMPERATURE THAN THE CATALYST IN SAID FIRST REGENERATION ZONE, AND SUPPLYING HOT REGENERATED CATALYST FROM SAID SECOND REGENERATION ZONE TO SAID FIRST CRACKING ZONE.

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