US2436618A - Conversion of hydrocarbon oils - Google Patents

Description

w. J. swEENEY 2,436,618

CONVERSION OF HYDROCARBON OILS Filed nec. 27, 1944 2 sneetsfsheet 1 Feb. 24, 1948.

Patented Feb. 24, 1948 Ztittid 2,436,618 lCONVERSION F `HYDROCARBON OILS WilliamJ. Sweeney, Summit, N. J., assignor to Standard Oil Development Company, a corporation of Delaware Application December 27, 1944, Serial No. 569,996

1 Claim. (Cl. 196-52) This invention relates to the conversion of hydrocarbon oils and pertains more particularly to the conversion of high-boiling hydrocarbons into high-quality aviation gasoline.

One of the objects of the present invention is 5 small amount of non-aromatic constituents, to provide an improved method of producing ranging from to 35%,which adversely aect aviation gasoline of superior quality. the quality of the aviation fuel.

Another object of the invention is to produce In accordance with the present invention, the an aviation gasoline which will have exceptional heavier fraction is subjected to catalytic retreatrich-mixture performance. 10 ment under relatively higher temperatures than Another object of the invention is to provide are maintained during the cracking of the lower a process for converting high-boiling hydrocarboiling fraction. This retreating temperature bons into aviation gasoline and low-boiling olemay, for example, be of the order of from 850 F. nic hydrocarbons which may be utilized for the to 1000 F. Under these conditions, the nonproduction of synthetic rubber or other valuable aromatic constituents present in the heavier products. fraction are selectively cracked into lower boiling It has heretofore been proposed to crack hyhydrocarbons without substantially affecting theA drocarbon oils in the presence of finely-divided aromatic constituents contained therein. These catalysts under conditions controlled to produce lower boiling hydrocarbons may then be sepaa relatively high yield of butenes which may be 2o rated from the aromatic constituents by simple further processed to produce butadiene for the fractionation, and the relatively pure aromatic production of synthetic rubber. Under condiso obtained may then bevblended with the retions amenable to the production of high yields treated light naphtha to form a balanced aviation of butenes and other low-boiling olens, the gasfuel. oline produced is not suitable for direct use for It has been found that the removal of the nonaviation fuel due to the presence of the relatively aromatic impurities from heavy naphtha matehigh percentage of olenic material in the lower rially improves the rich-mixture performance of boiling fraction of the aviation gasoline. the aviation fuel.

It has been proposed to produce aviation gaso- Having set forth the general nature and ololine by rst cracking a eas oil or higher boiling jects, the invention win be best understood from fraction at high temperatures in the presence of the more detailed description hereinafter in a catalyst to form oleiinic gasoline and thereafter which reference will be made to the accompany-I subject the olenic gasoline to further treatment ing drawing wherein Fig. 1 is a diagrammatic in the presence of catalytic agents. I have now illustration of equipment suitable for carrying;v found that the quality of aviation fuel may be the invention into eiiect and Fig. 2 is a flow plan further improved by rst separating the gasoline illustrating a different embodiment of the invenobtained from the initial catalytic cracking treattion. ment of the higher boiling hydrocarbons into a Referring to the drawing, the reference charlight naphtha fraction having an endpoint beacter lo designates a charge line through which' tween about 160 F. and 250 F., for eXamiole, 40 the oil to be processed is introduced into the and a higher boiling naphtha fraction. equipment, This oil may be a total crude, re-

The lower boiling fraction is then subjected to duced crude, or a clean condensate stock, such catalytic retreatment at relatively mild temperaas gas oil. In addition, the oil, instead of being tures, such as a temperature ofthe order of from derived from crude petroleum, may be obtained 500 F. to 850 F., preferably in the presence of 45 by synthetic processes such as by hydrogenation added hydrogen or hydrogen donors, such as or by synthesis of carbon monoxide and hydrohigher boiling naphthenic oils. The retreatment gen. The oil introduced through line l0 may be of the lower boiling fraction under relatively mild preheated to any desired temperature. The oil conditions materially reduces the amount of olepassing into the equipment through line I0 is iins contained in this fraction and thereby conintermixed with iinely-divided cracking catalyst verts said fraction into constituents suitable for use in aviation and motor fuel.

The heavier naphtha fraction which is separated from the initial catalytic cracking treatment is predominantly aromatic and contains 2 relatively little olenic material. However, in addition to the aromatic constituents contained in the heavier fraction, which may amount to from to 85% or 90%,'there is a relatively discharging into line l0 from standpipe Il hav-k ing a feed valve i2 for regulating the amount of catalytic material so introduced. The catalyst introduced into the oil stream may be any desired 56 active cracking catalyst, such as naturally active or activated clays, synthetic compounds of silica-alumina, silica-zirconia, boric oxide-alumina, and the like. Best results have been obtained by utilizing synthetic silica-alumina catalysts formed by impregnating a purified silica hydrogel with an aluminum salt solution and thereafter decomposing the salt into alumina by ammonia. The catalyst introduced into the oil stream through standpipe II is preferably at a temperature of from 1000" F. to 1200 F. which is attained during the regeneration of the catalytic material, as later described.

The amount of catalyst introduced may be controlled to supply the bulk of the heat necessary forV carrying out the cracking operation. In this case, the charging oil may be introduced through line I at substantially room temperature or at a mild preheat temperature- In general, the amount of catalyst admixed with the oil is between about i and parts of catalyst per part of oil by weight. l

In cases where it is desired to supply the bulk of the heat required for the cracking operation by hot catalyst introduced into the oil stream, the active catalytic material may be intermixed with a relatively inert diluent which may serve as a heat carrier. The mixture of catalyst and oil formed by the intr-oduction of the catalyst into the oil stream is transferred through line I3 into a distributing cone' Id located in catalytic reactor I5. The distributing cone i4 is preferably provided with a perforated grid IS positioned in the top thereof through which the suspension passes into the main body ofthe reactor. The' distributing cone I4 is preferably of somewhat smaller diameter than the outer shell of the catalytic reactor I5 to form an annular space between the shell and the cone through which catalyst is removed from the reactor, as later described.

The velocity of the oil vapors passing upwardly through the reaction chamber is preferably controlled to permit the catalytic material contained therein to settle into a relatively dense mass which is maintained in a turbulent condition by the upward passage of the oil vapors therethrough. To this end. the velocity of the oil vapors passing upwardly through the reactor I5 may be of the order of from 0.5 to 5 feet per second. Under well regulated conditions, a relatively dense layer of finely-divided catalytic material is formed within the reactor I5 superimposed by a dilute phase containing a relatively small amount of entrained solids.

The oil vapors passing through the reactor I5 are cracked under conditions controlled to produce a relatively. high conversion, such as of the order of from 60% to 90%, as measured by the amount of feed disappearing during the cracking operation. Under high conversion conditions a substantial per cent of the oil is converted into butane-butene constituents. The amount of butane-butene constituents may, for example, range from 10% to 25% or more of the fresh feed, depending upon the conditions of operation. The temperature within the` reaction chamber may be between 850 F. and 1050J F., and preferably between 900 F. and 1000 F. The time of passage of the oil vapors through the mass of finely-divided catalytic material through the reactor may range from 5 to 50 seconds and the weight of oil treated per hour per weight of catalyst within the reactor at a given instant may be of the order of from 0.5 to 10.

The oil vapors after passing through the bed of catalytic material within the reactor I5 are conducted to a cyclone separator I1 which may be positioned in the top of the reactor. Entrained catalytic material separated from the cracked vapors in the cyclone separator Il may discharge through conduit I8 into the dense, turbulent mass of catalytic material therein. The cracked vapor products after passing through the cyclone separator I'I are removed overhead through line I9 to a fractionating tower 2I in which the products are subjected to initial fractionation to condense insufficiently cracked constituents. The initial condensate formed may contain a small amount of entrained catalytic material which is not removed by the cyclone separator I1.

During the course of the cracking operation, the catalytic material becomes contaminated with carbonaceous deposits which impair its activity. In order to maintain the desired activity, a portion of the catalytic material in the reactor I5 continuously discharges through the annular space formed between the distributing cone I4 and the outer shell into the bottom section of the reaction chamber. A stripping gas, such as steam, spent combustion gases or the like, may be introduced at one or more spaced points in the bottom section of the reaction chamber to remove gaseous reaction products from the catalyst. Following the stripping operation, the catalyst discharges from the bottom of the reaction chamber I5 into a standpipe 22 having a control valve 23 which feeds the catalytic material at a controled rate into a stream of air passing through line 24. The stream of air carries the catalyst through lines 24, 25 and 26 into the bottom section of a regenerating chamber 2l below a perforated grid plate 28 located in the bottom portion thereof. A portion of the chamber below the grid plate 2li is preferably of reduced diameter to form a distributing zone for dispersing the catalyst into the regeneration zone. The velocity of the air stream passing through the regeneration zone is preferably controlled to permit the catalyst contained therein to settle into a relatively dense, luidized mass of catalytic material which is maintained in a turbulent state by the upward passage of the regeneration gas therethrough. The density of the catalytic material in this dense layer within the regenerator'may be of the order of from 10 to 25 pounds per cubic foot.

Within the regeneration chamber 21 the catalyst is subjected to oxidizing conditions to burn off carbonaceous deposits contained thereon, as previously described. During the burning operation, considerable heat is. liberated and the catalyst temperature is raised. During regeneration it is desirable to control the temperature tov avoid permanently impairing the activity of the material. AThe spent combustion gases after passing through the mass of catalytic material in the regenerator 21 are passed to a cyclone separator 2B located in the upper portion of tbe regenerator 21. Entrained -catalytic material separated from the regeneration gases in the cyclone separator 29 may be returned to the main body of the catalytic material therein through line 3l.

The spent regeneration gases after passing through the cyclone separator 29 are removed through line 32 and may, if desired, be passed to further purifying devices, such as Cottrell precipitators, scrubbing chambers, lter bags, and the like. for further removal of entrained catalytic material therefrom.

'I'he spent combustion gases may also be passed to a suitable heat absorber such as a waste heat boiler for recovery of heat therefrom prior to being vented to the atmosphere For the purpose of simplicity, these purifiers and heat exchangers have not been illustrated in the drawing.

The catalytic material after being subjected to the desired amount of regeneration within the regeneration chamber 2l is continuously withdrawn therefrom through standpipe il which has an internal extension 33 terminating within the dense layer of catalytic material at a point somewhat above the perforated grid 28. A portion of the regenerated catalytic material withdrawn from the regenerator through standpipe il is dis charged into the oil stream, as previously described.

Returning again to the fractionating tower 2 i, the oil vapors introduced therein are subjected to fractionation to condense the insufficiently cracked constituents as reflux condensate. This fractionatingtower may be provided with suitable trap-out trays for segregating the condensate into separate fractions of different boiling range. For example, the initial condensate formed in the bottom section of the tower and containing ent-rained catalytic material carried overhead from the rem actor I5 may be withdrawn from the bottom of the fractionator through line 34. An intermediate condensate may be collected in trap-out tray 35 located at an intermediate point of the tower. This product may be withdrawn from the system and utilized as a diesel fuel, kerosene, heating oil or the like, or it may be returned to the reactor for further conversion by recycle line (not shown). The top of the fractionating tower 2| may also be provided with a trap-out tray 36 in which a heavy naphtha fraction may be collected, if so desired. This heavy naphtha may have an initial boiling point between 160-250 F. and a nal boiling point between 30W-450 F,

Vapors remaining uncondensed in the primary fractionating tower 2| are removed overhead through line 31 and may be passed to a secondary fractionating tower 38 in which further fractionation is carried out to segregate a heavy naphtha fraction, of the above-specified boiling range. and a lighter naphtha fraction. The heavy naphtha fraction formed as condensate in the fractionating tower 38 is removed therefrom through line 39 and is charged by means of pump ill to a heavy naphtha retreating reactor 42. As illustrated, a portion of the regenerated catalyst from regenerator 2'! may be introduced into the heavy naphtha. stream through conduit 43 having a control valve 44.

The heavy naphtha retreating chamber 42 may be of the same general construction as the catalytic cracking reactor l5, except that the capacity may be substantially smaller since it is designed to process only the heavy naphtha fraction. The heavy naphtha vapors passing upwardly through the retreating chamber 52 are controlled to maintain a dense, turbulent mass of catalytic material therein. The products within the reaction chamber 42 are preferably main tained at a temperature of from 850 F. to 1050 and preferably between 900 F'. and 1000 F. This temperature may be maintained by controlling the proportion of hot, regenerated catalyst introduced into the heavy naphtha stream through line 43. or the heavy naphtha may be subjected to preheating to any desired temperature prior to the admission of the catalyst thereto. The conditions within the retreating chamber 42 are controlled to preferentially crack the non-aromatic impurities contained in the heavy naphtha derived from the catalytic cracking process previously described. The amount of catalyst introduced into the heavy naphtha stream may, for example, range between 0.5 and 10 parts of catalyst per part of naphtha by weight. The time of residence of the heavy naphtha vapors within the reactor may range from 5 to 50 seconds. The heavy naphtha vapors after undergoing retreating in the reaction chamber t2 are passed to a cyclone separator 45 positioned in the top of the chamber for removal of entrained catalyst particles from the gases. The catalyst particles removed from the gases in the cyclone separator 45 are returned to the main boiling polymers formed during the operation, is-

.removed from the bottom of the iractonating tower t3 through line i9. This polymer fraction may contain some entrained catalyst. The condensate fraction withdrawn through line 49 may, if desired, be recycled to the catalytic cracking Unit i5 by suitable recycle line (not shown).

Vapors remaining uncondensed in fractonating tower it are removed overheadv through l'ne 5l 'to a condenser 55% in which the normally liquid constituents are condensed. Products from the condenser 52 then pass to a product receiver 5S in which the liquid separates from normally gaseous products formed during the retreatingr operation. Liquid distillate collected in prod'ct receiver 5s is removed therefrom through line 5c. It desired, a portion of this distillate may be returned to the top of the tower i8 through line 55 ard pump 5t to serve as a reflux medium therefor. Gases separated from the liquid distillate in product receiver 53 may be removed overhead through line 5l and may be subjected to further treatment for remo-val of the higher boiling hydroarbon constituents, such as butanes, butenes, propylene and the like.

Returning again to the fractionating tower 3S, the light naphtha vapors together with normally gaseous products formed during the catalytic cracking operation are removed overhead from the tractionating tower 38 through line 5S to condenser 5i in which the light naphtha constituents are condensed. Products from the condenser @l are collected in product receiver 62 in which the light naphtha is segregated from normally geseous products formed during the catalytic cracking operation. Uncondensed gases and vapors are removed from the product receiver 62 through line The gaseous products may include all of the butane-butene fractions as well as the lower boiling hydrocarbons, or, if desired, the temperature within the condenser may be controlled so as to retain the bull; of the butane--butene constituents in the light naphtha fraction. According to the preferred mode of operatiomhowever, the butenes formed during the cracking operation are Segregat-ed from the cracked products and utilized as a source of raw material for the production of synthetic rubber,

The light naphtha fraction is removed from the product receiver E2 through line If des'red, a portion of the light naphtha removed from the product receiver 62 may be returned to the top of the secondary fractionating tower 38 through line 65 and pump 66 as a reflux medium therefor. 'Ihe light naphtha fraction removed from the receiver 62 is subjected to further retreating under temperature conditions substantially lower than those maintained during the retreating of the heavy naphtha fraction. To this end, the light naphtha from line 64 passes through pump 66 and line 61 to a light naphtha retreating chamber 68 which may be of the same construction as the heavy naphtha retreater 42. Finely-divided, hot, regenerated catalytic material from the standpipe I I is discharged into the stream of light naphtha passing through line 61 through conduit 69 having a control Valve 'il for regulating the quantity of catalytic material so introduced. The resulting suspension discharges into the light naphtha retreating chamber 68 and is subjected to treatment similar to that described with reference to the heavy naphtha, except that the temperature within the retreating zone may be of the order of from 509 F. to 850 F. The temperature within the retreating chamber may be controlled by regulating the proportion of the regenerated catalytic material introduced into the naphtha stream through line 69. In some cases, it may be desirable to cool the hot, regenerated catalytic material partially prior to introducing the same into the light naphtha stream.

It is also desirable to introduce into the naphtha stream undergoing treatment a naphthenic oil having a boiling range above the boiling range of the light naphtha. This naphthenic oil may serve to supply hydrogen for saturating the olefinic constituents contained in the light naphtha. The naphthenic oil may be obtained from an eX- traneous source or it may be produced by nondestructive hydrogenation of heavy aromatic naphtha produced in the process as hereinafter described. If desired, a naphthenic oil may be intermixed with the charging oil to the cracking reactor i to promote transfer' of hydrogen during the main cracking step. The naphthenic oil may be introduced into the light naphtha Stream through line 12. In place of naphthenie oils, hydrogen or other hydrogen donors may be interinixed with the light naphtha. The light naphtha. vapors are retained within the retreating chamber 68 for a period suiiicient to remove the olefin concentration therein to the desired minimum. Following this, the light naphtha vapors are passed through cyclone separator I3 positioned at the top of the retreating chamber 68. The catalyst separated from the light naphtha in the cyclone separator 'i3 may be returned to the main body of the reactor through line 14.

The light naphtha vapors after passing through the cyclone separator 'I3 are conducted through line l5 to a fractionating tower 'i6 in which constituents boiling above the end point of the desired light naphtha fraction are condensed. The condensate formed in the tower 'IS is removed therefrom through line ll. The light naphtha which remains uncondensed in the fractionating tower 7S is removed overhead through line l-B to a condenser T9 in which the light naphtha fraction is condensed.

The products from the condenser then pass to a. product receiver 8l in which the light naphtha distillate separates from normally gaseous constituents formed during the retreating operation. Normally gaseous constituents are removed from the product receiver through line 82. The light naphtha distillate is removed from the receiver 8l through line 83 and may be passed through line 84 to line 54 and blended with the heavy naphtha. from product receiver 53 to form a balanced fuel.

The catalytic material is continuously withdrawn from the heavy naphtha. retreater 42 through a standpipe 85 and discharged into a stream of air passing through line 25 which transports the catalyst to the regenerating chamber 21 for regenerative treatment. Likewise, catalytic material in the light naphtha retreater 68 is continuously withdrawn through a standpipe 86 and discharged into an air stream passing through line 26 which transports the material to the regenerator 2l.

In order to eiect circulation of the finely-divided material as previously described, it is necessary to build up or restore pressure on the cata# lytic material during circulation. As illustrated, this is accomplished by means of standpipes Il, 22, 85 and 86. In order to utilize the standpipes for developing pressure on the catalytic material undergoing circulation, it is essential to main-v tain the catalytic material in a fluidized, freely flowing state throughout its circulating path. To this end, a small amount of a fiuidizing gas may be introduced at one or more spaced points along the Various standpipes as indicated in order to maintain the catalytic material in the standpipes in a luidized condition, The amount of aerating or fluidizing gas admitted into the standpipes is relatively small and is preferably only sufficient to effect the desired uidity.

For simplicity, however, I have shown a single regenerator which is utilized for regenerating the catalytic material from both the catalytic cracking operation and the retreating operations. In some cases, it may be desirable to utilize separate regenerators for each of the treating operations and for the catalytic cracking operation. This is particularly suitable when diierent types of catalysts are employed for the three operations.

Fig. 2 is a ow plan illustrating a modication wherein the heavy naphtha resulting from the initial catalytic cracking operation is subjected to hydrogenation to convert the aromatic constituents thereof into naphthenes. The resulting naphthenes are then combined with the light naphtha passing to the treating zone.

Referring specically to Fig, 2, the fresh feed is introduced through line 9G and is passed to conventional type of catalytic cracking apparatus 9i, such as that illustrated in Fig. 1. The cracked products are then fractionated in a fractionating zone 92 wherein the cracked vapors are fractionated to segregate a light naphtha of the type previously described and a heavy naphtha. The heavy naphtha is passed through line 93 to a hydrogenating zone 94 wherein the products are hydrogenated under non-destructive conditions to saturate the aromatics and form naphthenes or hydroaromatics. The resulting naphthenes are then passed from the hydrogenating zone 95 through line 95 and combined with the light naphtha withdrawn from the fractionating zone 92 through line 96. The resulting mixture is then passed to a retreating zone 97v in which the light naphtha is subjected to retreating under conditions described with reference to Fig. 1. The products from the retreating zone 91 are subsequently fractionated to segregate the desired aviation gasoline therefrom.

What is desired to be protected by Letters Patent is:

A process for the conversion of higher boiling hydrocarbons into lower boiling hydrocarbons cracking temperature between 850 F. and 1000 F., contacting said hydrocarbons within said cracking zone with an active cracking catalyst, maintaining said oil within said cracking zone for a period su'icient to convert a major portion of said hydrocarbons into constituents outside the boiling range of said rst-named hydrocarbons, fractionating the cracked products to segregate a light naphtha fraction containing a relatively high proportion of oleinic constituents and a heavy naphtha fraction containing a major portion of aromatic constituents, hydrogenating said heavy naphtha fraction under non-destructive conditions to convert at least a portion of said aromatic constituents into naphthenes, combining the hydrogenated heavy naphtha so formed with said light naphtha fraction, subjecting the combined mixture to further treatment with an active cracking catalyst at a temperature between about 500 F. and 850 F. to reduce the oleiin content thereof, and fractionating the resultingy treated product to segregate a motor fuel fraction therefrom.

WILLIAM J. SWEENEY.

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

UNITED STATES PATENTS

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