US2596145A - Method of catalytically reforming hydrocarbons - Google Patents

Description

May 13, 1952 H. w. GROTE 2,596,145

` METHOD OF CATALYTICALLY REFORMING HYDROCARBONS Filed Dec. 21, 1948 @auf Patented May 13, 1952 METHOD OF CATALYTICALLY REFORMING HYDROCARBONS Henry W. Grote, Downers Grove, Ill., assignor to Universal Oil Products Company, Chicago, Ill., a corporation of Delaware Application December 21, 1948, Serial No. 66,527 4 claims. (c1. 19e-50) This invention relates to the conversion of hydrocarbons. It is more specifically concerned with a particular method of simultaneously reforming hydrocarbon reactants of high f and low naphthene contents in the platinum-containing catalysts.

Hydrocarbon stocks of low octane number that boil approximately within the gasoline' range and that contain naphthenes and parafiins may be upgraded by dehydrogenating the naphthenes to aromatics and hydrocracking `the parailins to lower boiling paraiiins. The aromatics possess considerably higher antiknock ratings thanV the corresponding naphthenes; the same is true of the lower boiling paraflins relative to thehigher boiling paraffins. l'

The yield-octane increase relationship resulting from aromatization is approximately linear over a wide range of octane increases. Thisis due to the loss of a portion of the charge stock to hydrogen, Vand in part to ay density increase inherent in changing naphthenes to aromatics. Hydrocracking, on -the other hand, involves a combination of cracking and hydrogenation of the fragments thereby produced. AIn the initial stages, this results' in the formation of lower molecular weight gasoline hydrocarbons which are of lower density than the charge. Thus the initial octane increases dueto hydrocracking often are obtained at a volumetric recovery or yield greater than 100%. As `the reaction proceeds, however, there is an increase in the tendency to produce gaseous hydrocarbons, which results in a loss of yield without any appreciable increase in octane number. Hydrocracking, therefore, is an efficient reforming process when not carried to extremesi In general, to obtain the optimum yield at a A'given` product octane number with a stock containing both naphthenesand paraiiins, it is necessary.

to'control the balance between the hydrocracking and aromatization reactions to limit the hydrocracking to the degree at which it is eillcient andto obtain the remainder of the octane number increase by aromatization.

Since the same types of hydrocarbonsV that are susceptible 4to aromatization are also susceptible to hydrocracking. it is important that the aromatization reaction be carried out iirst, since if it is not, some of these particular hydrocarbons will be hydrocracked in the early stages, and it is impossible to obtain a maximum amount of aromatization or maximum yield for a given octane number. Therefore, with hydrocarbon reformer charging stocks that contain presence of both naphthenes and paraiiins, I rst subject the stock to dehydrogenation and thereafter to hydrocracking. l

There are, however, some low octane number hydrocarbon stocks that boil within the gasoline range that are so low in naphthenes that itis not practicable to subject them to naphthene dehydrogenaton. In accordance with my invention, I mix such a stock with the hydrogen rich eiiiuent from the dehydrogenation zone and subject the resultant mixture to hydrocracking, i. e., I subjectv a stock containing naphthenes and paraflins to dehydrogenation and then commingle this stock with a low naphthene material and hydrocrack the resulting mixture. A combination process of this type oiers a number of advantages. The dehydrogenation produces, for example, three molecules of hydrogen for each six membered ring naphthene. Inasmuch as only one molecule of hydrogen is required when one molecule of a paran is hydrocracked into two lower boiling paraflin molecules, it can be seen that the dehydrogenation of one molecule of naphthene produces sufficient hydrogen for the hydrocracking of three molecules of paraiiin. Therefore, I am able to hydrocrack not only the parail'ins in the 'eilluent from the dehydrogenation zone but also the paralns in the low naphthene hydrocarbon stock without resorting to the use of `external hydrogen. I usually prefer to operate mycombination process in such a. manner that there is substantially no net consumption of hydrogen. This can be done by correlating the relative proportions of the two types of stocks fed to my process with the degree of dehydrogenation and hydrocracking obtained. Another advantage of adding a stock predominating in paraffins to the dehydrogenation zone effluent before it is subjected to hydrocracking, lies in thel fact that the concentration of aromatics in the material passing through the hydrocracking zone is materially reduced. The

- presence of aromatics inthe feed to the hydrocracker tends to cause carbon formation and the aromatics themselves tend to undergo certain reactions whereby a portion thereof is consumed without any benefit from an octane number standpoint. lThese tendencies are considerably reduced when the 4aromatic content is lowered to values below about 25% as they usually are in my process.

In one embodiment my invention relates to a hydrocarbon conversion process which comprises subjecting a naphthene-containing sub- 3 stantially olen-free hydrocarbon reactant boiling below about 425 F. to the action of a dehydrogenation catalyst under dehydrogenation conditions, commingling the resultant product with a naphthene-lean, substantially olefin-free 5 hydrocarbon reactant boiling below about 425 F., and subjecting the resulting mixture to the action of a -hydrocracking catalystmaintained under hydrocracking conditions. f g

In a more specic embodiment my invention relates to a process which comprises contacting at aromatizationlconditions in a iirst4 reactionv zone, a substantially olen-iree hydrocarbonre-f, actant containing a substantial proportion of naphthenes and boiling approximately 'within 15 the gasoline range with a cata-lyst'predominatingin aromatizing activity and comprising platinum and alumina, commingling the eiiluent.vfronisiid` rst reaction zone with a hydrocarbon reactant of low naphthene content that predominates in I parains, and contacting 2the resultant mixture at hydrocracking conditions :with a catalyst.1305:,H sessing. substantial hydrocracking activity; and comprising platinum, alumina, and halogen.

Therhydrocarbon-stocks that may .beaconllerted inA accordance.,with .the present .processk by, ,den hydrogenation I followed by v hydrocracking :com: prise 1 .nonolenic ,hydrocarbons.that@ contain naphthenes. Bya the. term..nonolenic I- .mean.. t substantially olen-frea'. i.; e., a-.fewdper cent ..0f;, 430 oleinsican be presentin the charge in sometypes ofoperation. VSuitable stocks include:-narr0 w: boiling` fractions V4rich, in. n aphthenes as welltas substantially` pure materials such..V as cyclohexw anefand methylcyclohexane. `YPlrererredastocks .35 are Vthose consisting; Vessentially of naphthenes';` andparains, although ,relatively minori amounts. of aromatics also may be present. J1-his pre1 i ferredclass ,includes primarily-straight-runv gasolines,'. such aslthose from Trinidadand the, Gulli` 40 Coast area. The gasoline mayibeiaiull boilingzf range gasoliney lhaving anv initialVboiling fp oint.l within` the range. of', from about,.,50 f;lto. about;I 100i F. 'and amend` boilingrpointjwithin -theA range lof from .aboutit-2,5? tdabout. 425,?;, E. or-p it may be a. selected `fractionf-.thereo :which: i usually. will` be a...higher boilingfractiong com- 1 monlyureferred to as,v naphthm. andN ,fgenerally having an Hinitial boiling point ,1 .of `4f1tomabout,v

125toY about250'- F. and an..end. boiling-point- (,0- r Within the range of Vabout()o Fatoabout 4:251-11. i,

The `expression ffstraight-run gasoline` fraction l as usedhereinis intended toinclude bothi-naphffA thas andifullvboiling gasolines.:- i ,l 1 m The flow naphthene content hydrocarbon stocksthat are.. included only, inm the charge-td. the hydrocracking ,step .should predominate,V in l -V paraffins` and will have. aboutgthe samev boiling rangesfas .thenaphthenefcontaining;stocks. Cerak tain v`straighterun gasolines ,fal1 finto, this classi-60 ficationlas Well as some-natural .gasolines,y recycle ,condensatea ,and the fparaiinicly gasolines produced, ,bythe Y Synthine process, i.; e., vby zone. f or more oftthe modified, forms ofthe Fischer, TIGDYSCI.DIOGEBSS` Y ufff i., l \.;;l .1 .6

Any.. suitablev naphthene dehydrogenation catalyst may be, used .in `.therst step-of my process. Suitablelcatalytic compositesinclude a compoundiof the lmetalszof -theleft handl 'columno Groups V and..V I of the periodic -table and, in-partic'ular, 70 the oxides ofchromium;molybdenum, tungsten, and vanadium, either alone or inadmixture with one another, and a suitable refractorysupporting'- material such asalumina, magnesia,` silica; or mixtures rthereof..` The-particular process conv ,v silica-alumina,

and-thelike.. Zp'lvhecpreferred type of catalyst for both the 4 ditions of time, temperature, pressure and the likeV employed in any specific operation will, of course, Vary somewhat depending upon the catalyst used in the operation.

Suitable hydrocracking catalysts that may be used in the second step of my process include composites comprising Y a cracking component plus ajhydrogenating component; y Examples of suchcornposites -are nickel, chromium, and molybdenum, deposited on or incorporated in silica-zirconia, silica-magnesia,

dehydrogenation and the hydrocracking steps is one ycomprising `platinum and alumina. These 1 catalysts may` contain substantial amounts of M platinum, but, for economic as Well as for product yield and quality reasons, the platinum ccntent usually will be Within the range of from about V0.05% to about 5.01%. A particularly effective catalyst of this type contains relatively minonamounts, usually lessthan aboutz-,3%izon a ldryr aluminal basis, .of. a .halogenespecially chlorine or 1 uorine.. One method-,4 of preparing l thegcatalyStv comprises adding-,a suitableal'kaline reagent; @Such as ammonium hydroxide; on; carbonate to a. salt of aluminum, such as; aluminum l Chloride. Y. .aluminum -.:su1fate, raluminum.; nitrate, and thelike; in an amountsuicent to. .form alu-1 minum hydroxides ,'vvhich'upon drying,v can; be

added 'to` vthe resultant slurryiin :the formaof ani.

acid such ashydrogen' fluoride or hydrogen-chloe;v

ride,; or'. as `a yolatile c salt; such; as ammonium. fluoride-,orammonium chloride-` yThe amountrof combined; halogenuin i the,y Vfinished:catalyst. ide-L 'termines the hydrocracking activity.; flatinumffr alumina catalysts :that ,arez substantially; devoid of halognsfpredominate in Adehydrogenation;or:` aromatization; aptivity; whereas :platinum-ame;

l l,minaf catalysts containingA greater .I than about Y Of vhalogen inthercatalyst 3-5%:, l

.in-a lower-1;concentrationioria given degre'eiof;V hydlocracking;activityx ;^,Ordinarily the l amount ,i

will :not exceed .about A-satisfactryhietnod of adding platinum teA the aluminafhalogen .composite-.zcompri-ses pre paring. a ;colloidal:.. suspensionof fplatin'ic'f sulfide by .introducing hydrogen fsulde: i'nto an` aqueousl solution; of.ch1oroplatinic f acid'until said solution -f reaches-'a constant-color, which usually dark ",brown. t The resul-tant colloidal= Esuspens-ionVv of"ly platinic sulfide is commingled'wi-th the aluminum l hydroxideslurry at room --temperature followedby Astir-ring Vvto :obtain intimatemixing.-' 'There- '5 sulting :material .is then -d'riedatz a temperature of fromfaboutZOO? to about 400-=Ff1for aperiod of from about 4to about 24 hours-*br ymore to form a cake;.= *The*A resulting Amaterialmay then lue-conf prior to use: .Itis-to be understood thatthe fore-'f going method of preparing satisfactory 'vplati numfalumina'vicatalysts -is-merely-illustrative andL U ,is notto-rbeftaken-in alimitative senseinasmuch fas 'variousffothrz methods ina-ybelemployed toV` producel satisfactorycatalysts oi this type:-vv The use of the eterm catalystcomprisingplatil num' 'and aluminahin the-specification; and '-'a'p pended claims isV :intended tdirzcludeplatimimV-L alumina composites of the type described above including those containing minor amounts of a halogen. The exact manner in which the halogen or` halide ion is present in the catalyst is not known, although it is believed to be present in the form of a chemical combination or loose complex with the alumina and/or platinum components. Because the exact chemical constitution of such halogen-containing catalysts is not known, I sometimes refer to them as catalysts comprising platinum, alumina, and a halogen. It is known, however, that the presence of a small amount of a halogen in the catalyst enhances the hydrocracking activity thereof; for platinumalumina composites that are substantially halogen-free possess very little ability to provide hy'- drocracking.

Other platinum-containing catalysts that may be used in my process, although not necessarily with equivalent results, include platinum on charcoal, platinum on silica, platinum on asbestos, and platinum on bases or carriers that possess cracking activity such as silica-alumina composites. The corresponding palladium catalysts occasionally may be used with advantage in my process. i

Additional features and advantages of my invention will be apparent from the following description of the attached drawing which illustrates a particular method for conducting a hydrocarbon reforming operation in accordance with the present invention.v

Referring to Figure l, a full boiling range straight-run gasoline which contains paraiiins and a substantial amount of naphthenes is charged through line I and is picked up by pump 2, passed through line 3 containing valve 4, and is joined by a stream of recycle hydrogen flowing through line 5 and produced as hereinafter described. The combined stream of straight-run gasoline and hydrogen is passed through heater 6 wherein it is heated to a temperature of about 900 F. The eiiluent from the heater is Withdrawn through line 1 and is changed to header 8 of reactor 9.

Reactor 9 comprises a furnace of the downdraft type and is provided with a burner at the top thereof. Vertically disposed tubes are arranged adjacent the wall of the furnace so as to be heated predominantly by radiant heat. A suitable gaseous or liquid fuel is charged to reactor 9 through line I0 containing valve II and the products of combustion are removed via line I2. The tubes are filled with 1/8" x 1/8" pellets of platinum-alumina catalyst containing less than about about 0.1% fluorine or chlorine. The tubes are disposed on an annular circle, the center of which substantially corresponds to the center of the combustion chamber. The name and the products of combustion now in a central longitudinal unobstructed path through the chamber substantially out of direct contact with said tubes. Because of the high heat input rates to the catalyst that can be obtained, a reactor of the type just described is particularly suitable for the highly endothermic naphthene dehydrogenation reaction. The amount of heat supplied to the catalyst and the reactants iiowing therethrough ordinarily is approximately equal to the endothermic heat of reaction.

The eiiiuent from the tubes in reactor 9 is passed through header I3 and into line I4 containing valve I 5. The concentration of hydrogen in the eiuent is considerably higher than the concentration of hydrogen in the charge to the reactor because three molecules of hydrogen were liberated for each molecule of napthene that was dehydrogenated. The hydrogen-rich material owing through line I4 is commingled with a` heated stream of naphthene-lean gasoline which ows through line I6 and is picked up by pump I 1 and passed through line I 8 containing valve I9. A stream of recycle hydrogen iiowing through line 20 is commingled with the two streams and the resulting mixture is passed into reactor 2I. The reactor is packed with a platinum-alumina catalyst containing 0.5% fiuorine and is maintained at a temperature of about 880 F. The predominant reaction that takes place in reactor 2| is hydrocracking of higher boiling parains to lower boiling paraffins. However. the catalyst possesses dehydrogenation activity. and the small amount of naphthenes that may be present in the euent from reactor 9 or in the gasoline iiowing through line I6 will be converted to aromatics in this zone. Consequently, the overall reaction that takes place in reactor 2l is substantially thermally neutral. a However, it may be somewhat exothermic or even somewhat endothermic depending upon the relative amounts of hydrocracking and dehydrogenation that are effected. a

The eilluent from reactor 2| passes through line 22 containing valve 23 and into receiver 24 wherein a separation is effected between hydrogen and low molecular gaseous hydrocarbons on the one hand and higher molecular Weight liquid hydrocarbons on the other;` The hydrogen-rich gas is withdrawn from receiver 24 through line 25. It is picked up by compressor 26 and a portion is passed through line 5 containing valve 21 and the remainder is passed through line 20 containing valve 28. Make-up hydrogen may be added to or excess hydrogen may be withdrawn from the system through line 29 containing valve 30. The liquid hydrocarbon layer in receiver 24 is Withdrawn through line 3| containing valve 32 and is sent to suitable fractionation and storage equipment.

It is to be understood that the process that has just been described is to be taken in an illustrative and not in a limitative sense for the reason that a number of variations may be'made in the process without departing from the spirit of the invention. For example, in some types of operation it may be desirable to effect the dehydrogenation in reactor 9 in the absence of recycle hydrogen. Again, it may be desirable to combine the dehydrogenation zone and the hydrocracking zone into a single vessel as shown in Figure 2. The naphthene-rich reactant would then be passed through line 33 and into reactor 34 wherein it first contacts a bed 35 of dehydrogenation catalyst. The effluent from this bed is joined by a stream of naphthene-lean hydrocarbons passing through line 36 and the combined stream passes through bed 31 of hydrocarbon catalyst. The eiiluent from reactor 34 is withdrawn through line 38.

Hydrocarbon reforming operations carried out in accordance with my process in the presence of catalyst comprising platinum and alumina ordinarily will be conducted at temperatures of from about 750 F. to about 1000" F. The dehydrogenation reaction usually will be conducted at a temperature near the upper end of the range and the hydrocracking reaction will be conducted at a somewhat lower temperature within the range of from r" F. to about 950 F. The pressure at which my process will be conducted 'heriemploying.. platinumfaliirnriai caielyst Vfor..

1; Af process;forj1',hejf simultaneous reforming` of "gasoline Stoqks; 01E.' relatively high and, 101W,"

naphtyhene cgnient; whichjcomprises; subjecting which, is. deneiqas, i the' w'elg" n of hydrocarbon chafgedtperhoof rjweighgbri frwifmv Containing flambe-nes.. and; Damme-Site;

REFERENCES .011.13119 Catalytic Reforminep. ,Stfaghirun ,G aSQHQfL (pagesl

Claims (1)

1. A PROCESS FOR THE SIMULTANEOUS REFORMING OF GASOLINE STOCKS OF RELATIVELY HIGH AND LOW NAPHTHENE CONTENT, WHICH COMPRISES SUBJECTING A SUBSTANTIALLY OLEFIN-FREE STRAIGHT-RUN GASOLINE FRACTION CONTAINING NAPHTHENES AND PARAFFINS TO CATALYTIC DEHYDROGENATION TO CONVERT NAPHTHENES TO AROMATICS AND FORM HYDROGEN, COMMINGLING WITH THE RESULTANT HYDROGEN-CONTAINING PRODUCT A SUBSTANTIALLY OLEFIN-FREE, PREDOMINANTLY PARAFFINIC, NAPHTHENE-LEAN GASOLINE FRACTION IN AN AMOUNT SUFFICIENT TO LOWER THE AROMATIC CONTENT OF THE MIXTURE TO BELOW ABOUT 25%, AND THEN SUBJECTING THE MIXTURE TO THE ACTION OF A HYDROCRACKING CATALYST COMPRISING PLATINUM, ALUMINA AND HALOGEN MAINTAINED UNDER HYDROCRACKING CONDITIONS TO CONVERT HIGHER BOILING PARAFFINS INTO LOWER BOILING PARAFFINS.

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