US2470263A - Hydrocarbon conversion process - Google Patents

Description

May 17, 1949. N. E. PEERY HYDROCARBON CONVERSION PROCESS Filed July 2'7, 1946 Scrubber leqenerafl'or Gasoline,

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Furnace Heafer lnvenTrZ Norman E. Peer-L Patented May 17, 1949 HYDROCARBON CONVERSION PROCESS Norman Peery, San Francisco, Calif., assignor to S hell Development Company, San Francisco, Calif., a corporation of Delaware Application July 27, 1946, Serial No. 686,639

4 Claims.

The present invention relates to a process for the conversion of hydrocarbon oils primarily into gasoline and normally gaseous products through cracking.

An object of the invention is to provide a simple process whereby gasoline of good quality may be obtained in better yields without resort to elaborate and costly equipment. Another object is to provide an improved process wherein existing equipment may be advantageously employed. A further object is to provide a method whereby substantially the entire cracking stock may be converted into quality gasoline and a gaseous fraction rich in desirable olefins.

In catalytic cracking of hydrocarbon oils boiling above the gasoline boiling range, only about half of the hydrocarbon oil is converted into cracked products. The remainder consists of a heavy car-.-

bonaceous material and unconverted and pan tial-ly converted products. The main portion of the remainder known as catalytic gas oil is sub.- stantially depleted of more readily crackable ma.- terials and is consequently relatively refractory. It has heretofore been proposed to recycle some of this material to the catalytic cracking step. However, due to the refractory nature of the material, it contributes little to the gasoline yield and this operation is economical only in special cases such as when there is a shortage of virgin feed stock.

It has been proposed to subject the catalytic gas oil to a drastic thermal treatment .such as coking. This is generally considered as economical operation and is sometimes practiced. However, the yields of gasoline are not as good as desired and the gasoline is generally unsuited for use without further treatment.

In the catalytic cracking of virgin stocks, the character of the catalytic cracking reaction is fat vorably influenced 'by the simultaneous crack-ing of minor amounts of thermal gas .oils. This is entirely unexpected since thermal .gaS oil is a much poorer feed for catalytic cracking than virgin gas oil and its inclusion would be expected to give poorer rather than improved results. Catalytic gas oil can :be cracked under mild thermal cracking conditions, rather than under drastic thermal conditions, to give a small yield .of gasoline and a gas oil partaking of the qualities of thermal gas oil. The process of the presen in-. vention is designed to take advantage .of the improvements possible through the utilization of these facts. In general outline the process is carried out as follows:

The hydrocarbon oil to be cracked, for example virgin gas oil, is first used to quench the product of what is herein designated as a thermal-catalytic cracking treatment. The mixture is then cracked with a large excess of solid cracking catalyst to produce substantial yields of quality gasoline. The product is separated into a normally gaseous fraction rich in valuable olefins, a quality gasoline and a catalytic gas oil fraction containing minor amounts of partially spent catalyst in suspension. This suspension is then subjected to the thermalecatalytic cracking treatment. Due to the refractory nature of the stock, the small amount of catalyst present and the partially exhausted condition of the catalyst, the cracking in the thermal-catalytic cracking treatment is partly thermal and partly catalytic. The gasoline produced in this step is not of particularly good quality and is not separated. Also the gas produced is not of particularly good quality and it also is not separated. After quenching the product of the thermalcatalytic cracking treatment with the virgin feed, it is subjected to catalytic cracking with a large amount of catalyst as described above.

In specific embodiments of the process, the catalytic gas oil is also used to scrub minor amounts of entrained catalyst from gases in the system. This material is particularly suited for this use. Also, the minor amount of catalyst picked up in this manner is usefully employed in the thermal-catalytic cracking step. In an-. other specific embodiment of the process, a portion of the virgin feed is commingled with the product of the catalytic cracking step to serve as a heat regulator and also to alter the proper ties of the product of the thermal-catalytic cracking treatment. The improved results obtained are due to the observed beneficial effect .on the cracking of the virgin gas oil .of minor amounts of unsaturated products produced in the thermal-catalytic treatment. These products appear to improve the cracking of the virgin gas oil through the provision of easily crackable hydrogen acceptors. It is to be understood, however, that the invention is not dependent upon the correctness of these explanations of the catalytic phenomenon.

The process of the invention will be described i more detail in onnect-ion with the ri tion of a typical operation. To aid in this description, reference is had to the attached drawing wherein a plant adapted for the operation is illustrated semi diagrammatically by means of conventional figures not drawn to scale. Referring to the drawing, the reed which may be any hydro a on oil boiling above the gasoline boiling range, but is preferably a virgin gas oil from a naphthenic petroleum, is introduced by pump I via line 2. This feed or a portion thereof passes via line 3 to line 4, wherein it commingles with the product of the thermal-catalytic cracking treatment hereinafter described and serves as a quench oil. It then passes via lines 4 and 5 to cracking reactor 6. The mixture in line 4 contains the virgin gas oil feed commingled with thermal and catalytic gas oil as well as thermal and catalytic gasoline and gas. The mixture also contains a small amount of spent catalyst in suspension. This mixture in passing to line 5 picks up a quantity of hot regenerated powdered cracking catalyst from standpipe I of the regenerator 8. The amount of catalyst picked up by the oil stream is large with respect to the oil, usually being in the order of 5 to 30 parts by weight per part of oil. The contact of the hot catalyst (which may be at a temperature in the order of 1200 F.) with the hot oil causes substantially complete vaporization of the latter. The oil vapors carrying the fresh catalyst in suspension pass up through the cracking reactor 6. Reactor 6 is a conventional bottom-drawoff fluidized catalyst reactor. The conditions in the cracking reactor are adjusted to afford substantial cracking, for example a depth of cracking between 40 and 65%. The temperature is preferably in the range of 850-1100 F. The liquid hourly space velocity is generally between about 0.2 and 3 (Liquid hourly space velocity is defined as the volumes of hydrocarbon feed, measured as a liquid, passed in contact with a unit volume of the catalyst in one hour). Any pressure may be used. However, pressures in the order of 1 to 10 atmospheres absolute are quite suitable.

Spent catalyst is continuously withdrawn from the reactor 6 via line 9 and is conveyed by a stream of air via line 10 to the regenerator 8 wherein it is regenerated in the conventional manner.

The hydrocarbon vapors leaving reactor comprise normally gaseous products,.cracked gasoline, catalytic gas oil and also a small amount of partially spent catalyst in suspension. This product is passed via line H to fractionator it. The gasoline and normally gaseous products are removed from fractionator l2 via line 53 and after cooling to condense the gasoline constituents it is passed to separator l4. Normally gaseous products rich in valuable olefins are removed via line I and gasoline is removed via line it. The normally gaseous products may be further worked up to convert them into gasoline or other valuable products by known methods. Also the asoline may be stabilized or further handled by conventional methods. The catalytic gas oil containing a small amount of partially spent catalyst is removed from fractionator l2 via line H. Part of this oil may be removed from the system if desired through valved line 18. The remainder is passed by pump l9 via line 20 to a scrubber 2|. In the scrubber the oil scrubs small amounts of entrained catalyst from the exit flue gas. In order to reduce the temperature of the oil in the scrubber and consequently to decrease losses by volatilization, a part of the cold virgin oil feed may be advantageously commingled with the catalytic gas oil stream in line 20. valved line 22 is provided for this purpose. The catalytic gas oil coming from the scrubber and carrying a small amount of catalyst in suspension is passed by pump 20 via line 24 to the coil 25 of furnace heater 26. The conditions in coil 25 are adjusted to afford a minor amount of thermal cracking and a minor amount of catalytic cracking. Thus, the conversion to gasoline is usually between about 5% and about 35% of the charge, and preferably between about 10% and 25%. The temperature is usually in the range of 950 F. to 1350 F. The pressure may range widely, but is preferably in the range of from 150 to 1000 p. s. i. The contact time will depend upon the conditions and upon the particular gas oil used. It may be adjusted in the known manner to ive, for example, 15% conversion to cracked products boiling below 400 F. Upon issuing from the cracking coil 25, the product is quenched with the virgin gas oil and passed to the catalytic cracking reactor as described.

It is to be noted that whereas the amount of catalyst in reactor 6 is at least parts by weight per part of oil, the amount of catalyst in the cracking coil -25 is only in the order of 0.5 to 10 pounds per barrel of oil; the catalyst in coil 25 is furthermore substantially spent catalyst. If the amount or activity of the catalyst in the oil in coil 25 were allowed to increase much beyond the limits indicated, the cracking would be substantially all catalytic cracking and a very refractory catalytic gas oil would build up in the plant. It is also to be noted that in the described process the virgin feed is not subjected to cracking in coil 25. The catalytic cracking of the material in coil 25 would increase the depth cracking in this step and decrease the efficiency of the second catalytic step in reactor 6.

Recommended catalysts for the described operation are the synthetic silica-alumina complex cracking catalysts used commercially at present, the commercial catalyst sold under the trade name Filtrol, synthetic silica-magnesia complex crackin catalyst, and adsorptive alumina supporting about 10-20% by weight of boric oxide. The second of the mentioned catalysts is an activated montmorillonite type clay. All of these catalysts are well known in the art and are described in numerous patents and periodicals. While the above catalysts are recommended, the process is in no way limited to the use of these catalysts. There are numerous solid cracking catalysts of this general type known, and although they are not now commercially used, their use is not precluded.

The invention claimed is:

1. Process for the production of gasoline from higher boiling hydrocarbon oils through catalytic cracking which comprises passing recycled oil containing between 0.5 and 10 pounds per barrel of a suspended finely divided solid cracking catalyst through a cracking coil under conditions to produce a minor amount of thermal and catalytic cracking, quenching the product by the addition of virgin gas oil, subjecting the mixture to catalytic cracking in the vapor phase in the presence of at least 100 parts by weight of said cracking catalyst per part of oil, fractionating the product to separate gasoline and a recycle oil, and subjecting the recycled oil to the above specified treatment.

2. Process for the production of gasoline from virgin gas oil with a finely divided solid cracking catalyst which comprises subjecting recycled gas oil obtained as hereinafter specified in the presence of 0.5 and 10 pounds per barrel of suspended catalyst to mild thermal-cracking at a temperature between about 950 F. and 1350 F., quenching the product by the addition of virgin gas oil,

subjecting the mixture to vapor phase catalytic crackin at a temperature between about 850 F. and 1100 F. in the presence of at least 100 parts by Weight of said cracking catalyst per part of oil, separating gasoline and heavy catalyst-containing recycle gas oil from the product and subjecting' the said heavy recycled gas oil to thermal cracking as above specified.

3. The process according to claim 2 in which the cracking of the recycled gas oil is carried out under conditions to convert between about 5% and 35% of the charge to gasoline.

4. Process according to claim 2 in which the virgin gas oil is from a naphthenic petroleum.

NORMAN E. PEERY.

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

UNITED STATES PATENTS Number Name Date 2,332,562 Eglofi Oct. 26, 1943 10 2,387,309 Sweeney Oct. 23, 1945 OTHER REFERENCES Eaton et a1., Ind. & Eng. Chem, vol. 24, N0. 7,

pages 819-822 (1932).

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