US2257723A - Production of motor fuel - Google Patents

Description

Oct. 7, 1941. M. H. ARvl-:soN-

PRODUCTION OF MOTOR FUEL Patented Oct. 7, 1941 UNITED STATES PATENT OFFICE raonUcTroN or M o'ron FUEL Maurice H. Arveson, Flossmoor, Ill., assignor to Standard Oil Company, Chicago, Ill., a corporation of Indiana Application 'January 26, 1938, Serial No. 187,100

6 Claims. (Cl. 196-9) This invention relates to the production of motor fuel from petroleum oil, and it pertains. more particularly to processes for converting a wide variety of petroleum fractions into high octane number gasoline. The invention is .applicable to the production of gasoline fromcrude oil, but while this is a preferred embodiment, it should be understood that the invention is equally applicable to the wide variety of petroleum fractions from various refining processes.

The object of my invention is to increase the yield and quality of gasoline obtainable from crude oil. A further` object is to increase the yield and quality of gasoline obtainable from` various oils and gases' resulting from petroleum refinery operations.

A rfurther object of my invention is to provide an integrated system of thermal ,and catalytic processeswherein each specific process is correlated with the other processes so that maximum thermal and operating efliciency is secured throughout' the whole system, and wherein the products from one process may be most eectively utilized in each of the correlated processes.

A further object is to provide an improved combination of conversion processes operating with different feed stocks andv under the same or diflferent conditions of temperature and pressure,

either with or without the presence of specific catalysts,`so that optimum conditions are obtained in each conversion process, optimum process, and optimum .rening methods are provided for the products of each process.

A further object is to simplify the apparatus and operation of a system for'converting crude oil to high quality motor fuel, to decrease the cost and increase the eiciency of such systems. Other objects will be apparent as the detailed description of my invention proceeds.

of which will be hereinafter set forth in morel detail. A common stabilizer is used for the three conversion processes. Hot products from one process are introduced directly into the hot feed stocks entering another process so that maximum thermal eiiiciency is obtained. By the particular combination of processes hereinabove described I can not only markedly increase the yield of gasoline obtainable from any givencrude, but

. I can obtain a higher quality motor fuel, one

which is particularly characterized by a very highV knock rating.

. The invention will be more clearly understood from the following detailed description. and from the accompanying drawing which forms a part charging stocks are available for each conversion My process comprises three major conversion Y steps:

y (1) Catalytic conversion of gas oil, either with or without heavy naphtha to produce highanti-knock motor fuel, a certain quantity of hydrocarbon gases and first cycle gas oil:v (2) Catalytic conversion of this ilrst cycle gas oil fraction, with or without the heavy naphtha, along with propane-butane fractions to produce high anti-knock motor fuel, a certain` l quantity ofgases and a second cycle gas-oil; (3) 'I'he catalytic conversion of the second cycle gas oil along with light hydrocarbon gases and hydrogen to produce high anti-knock motor fuel, a certain quantity of gases and a third Y cycle stock, the third cycle stock being recycled with the secondcycle stock in this step.

Other steps in the process include thel dehyof this specification and which diagrammatically represents the arrangement of a preferred embodiment of my apparatus or system'.

Crude oil is heated in conventional exchangers and coils and is introduced at a temperature of about 500 F. to 800 F. through line I0 into crude o il fractionating tower I I. wherein it may be separated into as many fractions as desired. Preferably, the vapors from the top of the tower pass through vline I2 and cooler' I3 to separator Il, a, light naphtha being withdrawn from the bottom oi the separator through line I5, and uncondensed gases being transferred through line I6 to compressors Il.

- Heavy naphtha is taken off as a side stream through line I8 and it may optionally be passed through line I9 to be processed with first recycle gas oil, or through line 20 to beprocessed with gas oil. The gas oil is withdrawn as a side stream through line 2l and reduced crude is withdrawn from the bottom of the tower through line 22.

The iight naphtha may se suitabie'for blending ,.described. If the naphtha is dehydrogenated it will be by-passed through line 23 through dehydrogenation system represented by the rectangle 24, the hydrogen being passed through line 25 to v treatment of gas oil.

gas une ls, and the dehydrogenated iight naphtpa 4being returned through line 26 to line l5 and thence to the stabilizer, as willbe hereinafter described.

The heavy naphtha may be 1processed in one of the ways hereinafter described or it may be treated catalytically, passed through line 21 to a catalytic conversion system represented by rectangle 28 for increasing its octane number, the treated heavy naphtha being introduced ythrough line 29 to the stabilizer, and any gases produced in the catalytic treatment being passed through line 30 to the gas line I6. If conversion system 28 is employed it is preferably carried out at :a temperature of about '100 to 850 F. in the presence of activated clay of the same general type which is hereinafter described with regard to the Gas oil from line 2|, which may contain-heavy naphtha from line 20, is forced by pump 3| t ough pipe still 32 and lines 33 to one or more o a battery of catalyst chambers 34. The particular temperature and pressure will depend somewhat upon the nature of the crude oil and the boiling rangeof the gas oil, but preferred temperatures are of the order of '150 to 1000 F.. preferably 850 to 925 F.' The pressure in the catalyst zone is preferably low, i. e.. atmospheric: or below fifty pounds per square inch.

I mayl use any one of a variety of catalysts known to be effective for the -conversion of gas oils and naphthas to low boiling hydrocarbons of high anti-knock rating. Such catalysts include activated hydrosilicates of alumina, -both natural and synthetic, particularly such compositions wherein the mol percentof alumina is of the order of 10% to 40%. The acid ,treated natural clays such as Attapulgus or Death Valley clay may be used. The catalysts also include boron silicate, alumina mounted on silica, and other mixed catalysts involving one element from the third group and one element from the fourth group in the periodic system. Nickel borite has been aas'mas y bers 34 are passed through line 35, through line 36 to the low pressure evaporator ltower 31.

Reduced crude from line 22 is introduced into this low pressure evaporator 31 above trap-out pan 38, where it picks up heat and where the light Vends are stripped therefrom. The hot stock from the trap-out pan is charged through line 39 to viscosity breaker furnace 40, wherein it is heated to a temperature of about 850 to 950 F., at about the same pressure asv the catalytic cracking system hereinabove described. The hot products from pipe still 40 mixed with catalytic cracking products from line are introduced through line 35 underneath trapfout pan 38. Tar is withdrawn from the base of the evaporator through line 4 I and vapor, comprising the rst recycle oil, gasoline fractions, and gases are taken overhead through line 42 to the rst bubble tower 43. The heavier gas oil fractions are condensed with the reduced crude in the evaporator tower and continuously recycled to the vis breaker pipe still until converted into lighter products and tar, respectively.

. In bubble tower 43 the gasoline and gases are separated from the first cycle gas oil, the former being .withdrawn from the top of the tower found to be an excellent catalyst, either alone orfV admixed with some other material to decrease its lcarbon-forming tendencies, i. e.. with cobalt.

borite, clay, bauxite, etc. Any and all of the above catalysts may be impregnated with other metallic oxides, including nickel, copper, cadmium, cobalt; thoria, manganese and the like. Ifdesired, vcertain promoters may be introduced along with the hydrocarbon stream entering the reaction zone, such promoters including the hydrogen halides, organic halides and easily decomposable oxides. When using oxideV promoters, some improvement is eifected in the cracking reaction itself, but what is more important, the life of the catalyst is extended by virtue of the consumption of carbonaceous matter on the catalyst while the process is in operation. These oxides include the organic peroxides and the oxides of or regeneratedy by oxygen-containing gases,` while other catalyst chambers are on stream. Such regeneration is-well-known in the art and needs no further description.

The reaction products leaving catalyst chamthrough line 44 to cooler 45, separator 46 and stabilizer A 41. Suitable reiiux means will,4 of course, be supplied in the top of the bubble tower, and a reboiler or heating means may be supplied at the bottom thereof.

The iirst cycle gas Oil from the base of bubble tower 43 is withdrawn through line 48 and 'forced by pump 49 through pipe still 50, thence through line 5I to one or more of a battery of catalyst chambers 52. As above stated, heavy naphtha from line I9 may be admixed with this first cycle gas oil in line 48, and a C3C4 gas fraction from line 53 may be introduced into the line between pump 49 and the pipe still. The Cs-Cl'fraction is obtained, as hereinafter described, and consists chiefly of propane, propylene, -normal and isobutanes, vnormal butenes and iso-butylene, a1- though small amounts oi!Y other hydrocarbons may be used. `If the Ca-Ci fraction is catalytically dehydrogenated, as hereinafter described, it

same as those employed in zone A, namely, from 800'to 1000 F., and preferably from 850 to 925 F. The pressures in this zone may also be similar to those used in zone A, but they are preferably higher, and may be up to 200 or 300 pounds per square inch or even higher. The catalysts in zone B may be the same as those used .in zone A, but they may in addition be impregnated with, or physically admixed with, one of the knowndehydrogenation catalysts. For example, pellets or particles of chrome oxide gel or metallic chromites, such as magnesium chromite, may be admixed with the extruded sticks or hollow cylinders of clay material used in zone A. It is particularly desirable to employ such dehydrogenation cata- -lysts invzone B if the gases charged thereto have not been previously dehydrogated. By carrying out the process of zone B in theV presence of normally liquid and normally gaseous hydrocarbons, it is found that while the yield is approximately the same as that which would be obtained by ,processing the two stocks separately, the octane number obtained is considerably higher.

Reaction products from zone B are introduced through line 55 to bubble tower 56. The gasoline and gases are withdrawn overhead through a suitablereducing valve to line 51, to line 44, cooler 45, gas separator 46 and stabilizer 41.

The second lcycle gas oil is withdrawn from the base of bubble tower 56 through line 56, and is forced by pump 58 through the coils of pipe still 60, thence through line6l to the catalyst chambers 61 of zone C. This second cycle gas oil is admixed with lhydrogen, methane, ethane, ethylene, etc., from line 63, which may be introduced in line 58 ahead of the pump or compressor 59. or which may be parately coinpressed and introduced into the line between pump 59 and the coils of the pipe still 60. The temperatures in catalyst chambers 62 of zone C are somewhat higher than those used in zone B-and may range from 900 to 1050 F. Pressures in zone C are preferably considerably higher than those used in zone B, and mayl range from 200 to 2000 pounds per square inch.- The catalysts in z one C are preferably those commonly described as sulfur containing hydrogenation catalysts of which molybdenum suide is an example. The purpose of zone C is to obtain an effective reaction between gases rich in hydrogen and a cycle stock of lw hydrogen content, so that a maximum yield of gasoline of comparatively high. octane number can be produced with a minimum amount of coke formation, and preferably without the formation of tar.

The products from zone C are introduced through-line '63a to bubble tower 64, the gasoline and gases being withdrawn from the top of this tower through line 66 containing a suitable pressure reduction valve to line 61, and the heavier products being withdrawn from the base of this bubble tower through line 66 and recycled along with second cycle stock from line 58 through the coils of pipe still 60 and through the zone C catalyst chambers.

The gasoline and gases from all of the bubble towers is cooled in condenser 45 and introduced into separator 46. the condensate being introduced into stabilizer 41, as hereinabove described. This stabilizer is preferably operated at a pressure of about 10D-300 pounds per square inch, and it may therefore be desirable to provide separate separators for the gasoline from low pressure and high pressure bubble towers. Finished gasoline is withdrawn from the base of the stabilizer tower through line 61. The overhead from the stabilizer is withdrawn through line 66 to cooler or condenser 69 and thence to separator 10. Liquid from this separator may be used as reflux in the stabilizer or passed by line 1|,to line 12.

Uncondensed gases from separator 46 are introduced through line 13 to line I6, and uncondensed vapors from separator 10 are introduced through line 14 to line I6. Line I6 will thus conduct all of the hydrogen, methane, ethane, ethylene Vand perhaps some propane, propylene, butanes and butylenes to compressor l1 which will boost the' pressure of these gases to about 300 pounds per square inch, or higher. The compressed gases are partially condensed in cooler 15 and introduced into separator 16. A fraction containing predominately hydrogen, C1 and Cz fractions is Withdrawn through line 63 for introduction into feed stock going to zone C, as hereinabove described. The condensate from separator 16, which contains chiefly C: and C4 fractions, is withdrawn through line 16a to line 12, from which it may be passed through line 53 to the feed stock entering zone B; A pressure absorber and stripper may be substituted for separator 16 with certain resultant economies in which case line 14 may lead directly to the ab-V sorber. Y

These fractions from line 12 may alternatively be passed through line 11, pipe still coils 16 and line 16 to dehydrogenation catalyst chambers 60 of zone D. The temperature of this zone is of the same order as that used in zone B, namely,

about 800 to 1000 F., and the pressures may likewise be aboutthe same as used in zone B. The catalyst used in the dehydrogenation of zone D is preferably a chrome oxide gel or a magnesium chromite, although it should be undehydrogenated Cs-C4 fractions may be eil'ected either catalytically or thermally. The catalytic reaction conditions will be approximately the same as those hereinabove described in connection with zone B. If a thermal process is used, temperatures of the order of 1050 to 1100 F. are preferred, with pressures upwards ,of 500 pounds per square inch.

While `I have described. a common stabilizer tower for light riaphtha, converted heavy naphtha, and gasoline from bubble towers 43, 56, and

64 it should be understood that each or any of these gasoline fractions may be separately stabilized if desired, without departing-from the spirit of my invention. .'I'he nnishedgasoline is preferably a blend of the products produced in each of the above-enumerated steps,- but it should be understood that particular products may be segregated for specialuse.

It will be noted that all of the gases from all of the zones of my system are fractionated in a common separator, segregated and utilized in those processes for whichthey are most suitable. Reaction in zone B, for instance, effects a certain amount of reaction of gaseous olens with normally liquid parafllns .or gaseous paraffins with normally liquid olens. 'Ihese reactions produce highly branched paraffin and'oleiin hydrocarbons of high knock rating. Similarly, in zone C there will bea certain amount of polymerization, hydrogenation, alkylation and gas reversion, so that the resulting motor fuel will consist of branched chain hydrocarbons which are richer in hydrogen than the second cycle gas oil `charging stock, and which are characterized by light gas component from the system through line 82 to the burner gas lines.

While I have described in detail a 'preferred l embodiment of my invention, it should b stood that I do not limit myself to an; lxfdile details hereinabove described, and it should also be understood that the above description has been simplied by purposely omitting details of heat exchange expedients, and of a large numberV of 'steam lines, water lines, pumps, compressors, valves, etc., which will be necessary for operation, but which are not shown for reasons of clarity. Regeneration equipment and catalyst chamber construction has not been described in detail for the same reason. Such details of construction and operation are well-known to those skilled vin the art, and their inclusion in this description would tend to confuse rather than to K 'clarify the description of the invention.

y gas oil, separating hydrogen and methane from said gases to obtain a (fa-C4 hydrocarbon fraction admlxing said 'C3-C4 fraction with said first recycle Agas oil, and catalytically converting said I mixturev to form a second cycle gas oil, and a high' antikncck gasoline characterized 4by branched chain'structure.

2. 'The` process of claim 1 which includes the further step of admixing a gas rich in hydrogen with lthe second cycle gas oil, and catalytically converting said mixture into high) antiknock gasoline under' a pressure of about 200 to 2000 pounds per square inch in the presence of a hydrogenation catalyst.

3. 'I'he method of converting crude petroleum oil into high quality motor fuel, which comprises fractionatingsaid oil into naphtha, gas oil and reduced crude, -catalytically converting said naphtha to form high antiknock motor fuel and gasescatalytically cracking said gas oil to form amrag'msA converting said reduced crude, together with said heavy products from the catalytic cracking step to form tar, flrst cycle gasoil, gasoline and gases, separating the gasoline and gases produced in the catalytic cracking and thermal conversion steps from the combined gas oils produced therein, catalytically converting said-combined gas oil, together with Aan admixed Cs-C4 fraction to producehigh quality gasoline, gas, and a second cycle oil, separating said second cycle oil from said gasoline and gas, catalytically converting' returning said fraction rich in hydrogen for conversion with said second cycle gas oil.

4. In the process of claim 3, wherein the Cs-C4 fraction is dehydrogenated before it is returned for admixture with said first cycle gas'oil.

5. The method of claim 3 wherein the catalytic cracking is effected at -a pressure .of about atmospheric to 50 pounds per square inch and a temperature of about 800 to 1000 F., wherein the conversion of the first cycle stock with the Ca-C4 fraction is effected at a temperature of about 800 to 1000 F. and at a pressure of about atmospheric to 200 pounds per square inch, and where-'- in the catalyticl conversion of .the second cycle stock with the fraction rich Ain hydrogen is effected at a temperature of about 900 to 1050 F. under a pressure of about 200 to 2000 pounds per square inch.

6. The process of claim 3 wherein the catalyst employed in the conversion of the rst cycle gas oil with the Cs-C4 fraction is a mixture of a `dehydrogenation catalyst with a crackingcatalyst.

MAURICE H. ARVESON.

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