US2436922A - Catalytic conversion process - Google Patents

Description

H. w. GROTE CATALYTIC CONVERSION PROCESS Filed June 28 March 2, 1948.

W ww Patented Mar. 2, 1948' 7 2,436,922 7 I CATALYTIC couvmsiosraocs ss iijniry'w. Grate; Downers Grove',-*II1;-,; assisnoito Universal on Products com any; Chicago; 111;," a-corporation 'of Delaware Application June 28', 1946, SerialNo it"lilQillll This invention relates "to th'e conversion of hydrocarbons. It is' -parti'cularly concerned with the preparationof suitable cracking charging stock from residual hydrocarbons by a novel method ofoperation which utilizes the regeneration gases from a catalytic cracking process. In recent: years many catalytic processes have been developed for the conversion of hydrocar- 5 Claims. (01. mt -52) bons utilizing solid-catalysts whichflgradually become contaminated or deactivated by: the deposition of high boiling hydrocarbons and carbonaceous deposits upon the catalyst surfaces. It is the usual procedure to regenerate or reactivate these catalysts by contacting them with okygen- 4 containing gases'at elevated temperatures, thereby burning off the hydrocarbon and carbonaceous deposits. The large quantity of heat liberated in the regeneration step is largely removed as sensible heat in the combustion gases. Heretofore, this heat has'seldom been recovered aled by passing the combustion gases through a steam generator. 7

One object of this invention is to prepare a de sired boiling range charge for a' conversion operation, particularly a catalytic cracking operation, from a high boiling hydrocarbon material such as a topped crude petroleum oil. Another object of the invention is to utilize the heat contained in thereg'eneration gases from a catalytic cracking process in the preparation of the desired catalyticcracking charge stock. A further object is to efiect the. heatingoi the starting material or charge in a manner that avoids the production of large amounts of deposits such as coke. A 'still furtherobject is to efiect the heating of the hydrocarbons to be separated in-such a, manner as to avoid thermal conversion of the high boiling' hydrocarbons to undesirable products.

In one embodiment my invention'relates to an improvement in the conversion of hydrocarbons in the presence of a' 'solid catalyst which becomes contaminated with high boiling hydrocarbons and solid carbonaceous deposits during the conversion operation and which is regenerated by contact with an o'xygen containing gas at com bustion temperatures; said improvement comprisifig commirighngthe hot combustion gases With 'alligh boilingpetroleum oil. subjecting theresulta-nt' mixture to flash vaporization, recovering a higher boiling hydrocarbon residue as a bottoms product" from nsemination step and a lowerboiling hydrocarb'cn" fractionia'san over- "20 through occasionally partial recovery was effect- 2 last named'fr'a'ctiori to the hydrocarbon conver= sion zone.

Briefly stated; my invention as applied to the catalytic cracking of hydrocarbons involves the use of at least a portion of the hot combustion gases produced in the regeneration of the contaminated catalyst to supply at least a portion oi the heat necessary to vaporize a suitable boiling range catalytic cracking charge stock from a topped or'reduced' crude. Specifically, the hot gases and the crude aremixed and led to a suitable separation zone maintained at a low but superatmospheric pressure. The presence of the flue gas lowers" the effective partial pressureof the oil vapors and hence favors flash vaporization of the hydrocarbons in a manner to give yields at supera'tmosphericpressure that are normally attainable only under high vacuum or by steam distillation. Thevapors are led from the separation zone and either charged directly to the cracking zone, or the hydrocarbons are condensed and separated from the residual combustion gases and the separated hydrocarbons charged to the cracking zone.

By the proposed process the overall recovery of heat from the combustion of catalyst deposit in the regeneration step is improved and the expensive step of flashing at high vacuum is replaced by a simple superatmospheric flashing operation. The heat recovery realized when my invention is applied to the fluid catalytic cracking of hydrocarbons is so great that a suitablecatalytic cracking charge stock can be obtained from a'topped or reduced crude by flash vaporization without the use of extraneous heat. An additional benefit is obtained through the use of my invention when the catalyst regeneration step is carried out in countercurrent fashion, i. e., when downwardly flowing contaminatedcatalyst is re-'- generated by contact with an upwardly flowing oxygen-containing. regeneration medium, In this type of operation the oxygen is substantially consumed by the time the regeneration medium reaches the top of the catalyst bed and oil vapors are "then stripped from the catalyst in the top 'sectionof the bed and pass out of the regenerator whereas coke formation is a major problem when heavy crudes are heated by conventional methods. More than this, my" process avoids thermal conversionin the heating and flashing zones and thus valuable "charge "stdck l is not consumed in producing unwanted gases and low octane number gasoline which would contaminate the catalytic gasoline.

The features of the present invention will be apparent in the following description of the attached diagrammatic drawing which illustrates in conventional side elevation one type of apparatus in which the objects of the present invention may be accomplished. For simplification, the description of the drawing is limited to a fluid Catalyst contaminated with high boiling hydrocarbon and carbonaceous deposits flows from recatalytic cracking process although it should be clearly understood that the invention is equally applicable to fixed bed and moving bed type processes. The drawing and description are not intended to place any undue limitation on the generally broad scope of the invention.

Referring to the drawing, the raw oil, which i may comprise a high boiling hydrocarbon material such as a topped or reduced crude oil, heavy shale oil, and the like, is charged through line I containing valves 2 and 3 and through exchanger 4 wherein it undergoes heat exchange with the hydrocarbon residue from the flash vaporization zone, If desired, the raw oil may .be.jby-pass"ed around this exchanger through line 5 containing valve 6. In the preferred method of operation, the raw oil is next passed through line 1 containing valve 8 and through exchanger 9 where it undergoes heat exchange with the vaporization zone overhead, which comprises vaporous hydrocarbons and combustion gases. A portion or all of the raw oil may be by-passed around condenser 9 through line l containing valve l I when the heat balance of the unit so dictates.

The preheated raw oil is then passed through line I2 and into line l3 containing valve 44 wherein it is commingled with the combustion gases from the regenerator. The resultant mixture is led into flash vaporizer I4 wherein a portion of the oil expands into vapor which has a lower average boiling point than that of the raw oil and passes overhead together with the combustion gases through line l5 containing valve I6 and thence through condenser 9. It the desired degree of condensation and cooling has been'attained in condenser 9, the mixture of hydrocarbons and combustion gases are led through line I! containing valve I8 and into disengaging drum I9. However, if further condensation or cooling is desired, the hydrocarbons and gases are passed through water condenser and thence into the disengaging drum.

The combustion gases separate from theliquid hydrocarbons in the disengaging drum and are passed through line 2! containingvalvein and vented to the atmosphere. Occasionally a water layer is formed in drum [9 from the condensation of the water vapor contained in the combustion gases. This water layer may be withdrawn through line 23 containing valve 24.

The hydrocarbons in disengaging drum l9 are passed through line 25 containing valve 26 and pump 21 and charged to reactor 28. 7 If necessary this hydrocarbon stream may be heated by any convenient method although a heating step is not shown on the drawing. Regenerated catalyst flows from regenerator 29 through line containing valve 3| and into line 25 wherein it is picked up by the oil and carried into the reactor. The hydrocarbon conversion products from reactor 28 are passed through line 29 containing valve 30 and sent to suitable recovery means such as fractionators, absorbers, and the like- Regenerating air is charged through line 33 containing valve 34. and into regenerator 123.

actor 28 through line 35 containing valve 36 and into line 33 through which it is transported by the regenerating air into the regenerator. The deposits are burned from the catalyst in regenerator 29 and the hot, substantially oxygen-free combustion gases are removed from the regenerator through line 13 containing valve 31 and passed into the flash vaporizer. Excess combustion gases may be vented to the atmosphere through line 38 containing valve 39. Similarly excess catalytic cracking charging stock may be withdrawn from disengaging drum l9 through line 40 containing valve 4|.

An alternative method of operation is to pass the uncooled, "unseparated overhead mixture of combustion gases and vaporous hydrocarbons from vaporizer l4 through line 15 and thence through line 42 containing valve 43 and into line 25 ,to reactor 28, This type of operation is preferred when the reaction taking place in reactor 23 is highly endothermic and it is desired to carry in'a substantial quantity of heat into the reactor.

The high boiling hydrocarbon residue from vaporizer I 4 is withdrawn through line 44 con- I taining valve 45.

The following example is given to illustrate my invention but it is not introduced with the in tention of unduly limiting the broad scope of said invention.

Example In a fluid catalytic cracking unit of the type shown in the drawing and described in the specification, 1000 B. P. D. of liquid, 25 A. P. I. gas oil derived in a manner hereinafter described is continuously charged to a reactor containing a synthetic silica-alumina cracking catalyst. The temperature in the reaction zone, which averages 950 F., is maintained by the continuous addition to the reactor of hot (1100 F.) regenerated catalyst from the regenerator. Seventy per cent of the gas oil undergoes conversion to gas, gasoline, and catalyst coke. The contaminated catalyst is continuously withdrawn. from the reactor and passed to the regenerator where the high boiling hydrocarbon and carbonaceous deposit, which amounts to 7 weight per cent of the gas oil charge, is burned from the catalyst. To burn this deposit and thereby regenerate the catalyst, 140,000 on. ftJhour of air is supplied to the regenerator. ,The combustion gases are led from the regenerator at a temperature of 1100 F. and commingled with preheated 22 A. P. I. reduced crude supplied at the rate of 1,250 B. P. D. The mixture of combustion gases and reduced crude is passed into a flash vaporizer in which the temperature is 850 F. and the pressure is one atmosphere. Two-hundred fifty B. P. D. of 10 A. P. I. residue are removed from the bottom of the vaporizer. The vaporizer overhead consisting of combustion gases and 1000 B. P. D. of 25 A. P. I. gas oil is heat exchangedw-ith cold reduced crude thereby condensing thegas oil and then passed to a disengaging drum. The combustion gases are vented to the atmosphere from this drum and the gas oil is charged to the reactor.

Thus it can be seen that a suitable charging stock for a catalytic'cracking unit can be prepared from a reduced crude by flash vaporization with hot combustion gases from the cracking process as the only source of heat.

I claim as my invention:

1...In a hydrocarbonconversion process where- '5 in a hydrocarbon charge is contacted at conversion conditions with a solid conversion catalyst in a hydrocarbon conversion step thereby depositing carbonaceous contaminants on said catalyst and said contaminants are subsequently removed by combustion thereof with an oxygen-containing regenerating gas in a regenerating step, the

improved method of preparing a suitable hydrocarbon charge for said hydrocarbon conversion step without the use of external heat which comprises subjecting a heavy hydrocarbon oil to indirect heat exchange with vaporization products obtained as hereinafter described, commingling the thus heated heavy oil with hot substantially oxygen-free effluent combustion gases from said regeneration step, flash vaporizing the resultant mixture to separate vaporization products comprising combustion gases and lower boiling hydro carbon vapors from a higher boiling hydrocarbon residue, cooling said vaporization products by indirect heat exchange with said heavy hydrocarbon oil to condense said lower boilin hydrocarbon vapors, said heat exchange step and said hot combustion gases being substantially the sole sources of heat supplied to said heavy hydrocarbon oil, and supplying the resultant lower boiling hydrocarbon condensate to said conversion step as charge thereto.

2. In a catalytic cracking process wherein a relatively low boiling hydrocarbon fraction is separated from a heavy hydrocarbon oil, said fraction is cracked in acracking step in the presence of a solid cracking catalyst, and carbonaceous contaminants are subsequently removed from said catalyst by combustion in the presence of an oxygen-containing regenerating gas in a regenerating step, the improved method of separating said relatively low boiling hydrocarbon fraction which comprises subjecting at least a portion of said heavy hydrocarbon oil to indirect heat exchange with hot vaporization products obtained as hereinafter described, commingling 6 the thus heated heavy oil with hot efliuent combustion gases from said regeneration step, flash vaporizing the resultant mixture to separate vaporization products comprising combustion gases and said relatively low boiling hydrocarbon fraction from a higher boiling hydrocarbon residue, subjecting said vaporization products to indirect heat exchange with said heavy hydrocarbon oil to efiect condensation of at least part of said relatively low boiling fraction, said heat exchange step and said hot combustion gases being substantially the sole sources of heat supplied to said heavy hydrocarbon oil, introducing the mixture of condensate and gas from said heat exchange step to a separating zone, withdrawing combustion gases, and removing the condensed relatively low boiling hydrocarbon fraction as charge for use in said cracking step.

3. The process of claim 2 further characterized in that said vaporization products are subjected to an additional cooling step after said indirect heat exchange step.

4. The process of claim 2' further characterized in that said heavy hydrocarbon oil comprises a, reduced crude.

5. The process of claim 2 further characterized in that said heavy hydrcoarbon oil comprises a topped crude.

HENRY W. GROTE.

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

UNITED STATES PATENTS Number Name Date 1,506,444 Pyzel Aug. 26, 1924 1,996,243 Heid Apr, 2, 1935 2,143,949 Keith, Jr Jan. 17, 1939 2,311,978 Conn Feb. 23, 1943 2,398,489 ,Arveson Apr. 16, 1946

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