US2440751A - Conversion of hydrocarbons - Google Patents

Description

May 4, 1948. H. R. LEGATSKI CONVERSION OF HYDROCARBONS Filed Nov. 5, 1945l ATTORNEYS Patented May 4, 1948 CNYESlQN 0F HYDEQQARBQNS, l Harold It., Legatskil. Bartlesyilles. Q k a., assignor "le Phillips-Petras@ Gsell?,

morele@ n @umanamente 5, 194s sexisme-sasso:

and saturated 1nono-o3rolopar:V

isomerizauon of normal hexane anni meihylcyclonentane. In anotherfaspect this inyentionjrelates to the preparation of a feed 'composition for an isomerizationplocess.

Natural and straight gaSQlllES.` are. usuglli separated into their:variousfV mpnemsby nag; Si

tionai @15u11ation,andthe` comnonenisftnus sep- @rated areutilizedlin variduswants. Generally, natural and straight run easulines alie separated into about seven fractions. The lightest fraction comprises propane and lighterlhydrocarhonsj.

This fraction is further separated into propane which is marketed commer ly as liqueefdf'netroleuin gas. The lighter Ydizocarloons `from this fraction ,may be 'used in; the" production' Qf v carbon black. The second fraction visfa, butarie f fraction icemprislns isobllleue and normal ,buleue- The tufo ,butenes' are separated and the islebutaee is usually alkyluted with butyleue t0 ferm Otanesx The normal "butahe is marketedas s lieueued petroleum eee. or may @emprise a leed fel' the manufacture@ butadiene 0r leerte@ used as a gasoline blending agent.- n paritarie fraction is also separatedfrom' the naturalgasoline containing isopentane and normal pantano.

T heisopentane isa blending ingredient for-loth aviation and high octane niotorf uels. Nornial pentes@ .is es e sulventeusl as blending. @sulla forfrnotor fuels.' A fourth fraction comprising (c1. couette) duction of a high quality he 'lhe h xane fraction separated from the natur W u gasolnesisofnal? interest sii1e"the isonexanesyhave been afa valuable blending ingredient 'in y t'o isomerizelioth the normal hexane aule o t n tnfiioniiarhesf ne" and' methyloyelopentane w"The Vobject 4ofA this" invention is to isomerize saturatednormal Qarafns and saturated "rjnn'o "-Itffis an object of this' invention tof provide a isoheg'iane and normal hexanefis separated Yand v the isrohexane fraction `is` 11S ej;l in both'ajliati'on and :noto-r fuels for increasing the, octane quality of; the product. The normal hexane fraction, which usually contains a large proportioniof methylcclopentane, is used in rnotor fuels and as a solvent. An isoheptane'fration separated from the natural orstraight rungasolin'is used as a component of 100 octane Agas 'olifriel VStillanother fraction separated from thenatural'and straight run gasoline is'fomp'osed of normal heptane and risooctane This Afrati'on'is further's'earated into its components. The normal heptane has various uses, such as av solvent and as 'a feed forthe manufacture of toluene. Isoocta'xe is Q flins" and Saturated l'noijio-` omerized in a manner heireprudueel an 'exceptionally c" products" which may be g n agent ier' meh o Q y eneratine theafuref hun frautionflfutu anormal parailu araillueouueutltateyafid the respective Geneseuis. ef `Whiellare reeelnlined, her duality ,fraction can' be." Qbtalnedthau Quuftheelll nel used as aviation fuel hase stock and inhigh ootanemotor fuel. Usua11y-the1astfractionnog the separati@ ,ef ille naturel ,eed Straight 'ruil gasoline comprises norrnal octane and heavier hydrecarbeuswhich. are use@` es .a refqimles. es?.

pnyicycipenijane tossina-t0 @man d. of both c yclohexane andi islohexans "nhasheenjused'das a single blending agent. By separate isomi erization of the normal heptane concentrate and the methylcyclohexane concentrate ultimately a higher quality blending agent can be obtained by combining the products of. the separate isomerization reactions than could be obtained by a single isomerization of the original mixture.

The isomerization of the hexanes is carried out under appropriate conditions of temperature,

pressure and residence time known in the art.

Apreferred catalyst comprises a Friedel-Crafts metal halide in the form of a hydrocarbon comweight per cent normal hexane and between about 35 and about 20 weight pery cent methylcyclopentane. The normal hexane fraction is separated into a normal hexane concentrate and a cycloparaiin concentrate by conventional fractional distillation. Preferably, the normal hexane concentrate contains at least about 85 weight per cent and up to about 93 weight per cent normal hexane and the cycloparan concentrate contains at least about 40 weight per cent methylcyclopentane. Each concentrate or fraction is then isomerized under appropriate conditions to obtain the desired isomeric product. In the case of the normal hexane concentrate, the isomerization product is isohexane; in the case of the methylcyclopentane concentrate, the isomerization product is cyclohexane. In isomerizing the normal hexane concentrate it has been found that at least 7 to about 12 weight per cent or more methylcyclopentane is desirable to inhibit side reactions, such as disproportionation, dealkylation and cracking. By separately isomerizing a concentrated normal hexane fraction and a concentrated methylcyclopentane fraction the yield of. isohexane and cyclohexane is greatly increased.

The normal hexane isomerization eiiiuent generally contains more than about 55 weight per cent isohexanes and less than about 10 weight per cent cycloparafns. 'Ihe methylcyclopentane isomerization ei'liuent generally contains more than about 25 weight per cent cyclohexane.

Isohexane is recovered from the normal hexane isomerization effluent as a product of the process and cyclohexane is recovered from the methylcyclopentane isomerization efliuent also as a product of the process. If desired these components, isohexane and cyclohexane, or the entire effluents from the respective isomerizations, may be combined to form a motor fuel blending agent. Unconverted methylcyclopentane and normal hexane from the isomerization eiiiuents may be recycled as a portion of the feed to the respectivelsomerization processes. A portion of the unconverted methylcyclopentane may be added to the feed to the normal hexane isomerization in order to maintain the naphthenic content of the feed within the desired limits.

This invention is equally applicable to the isomerization of other mixtures of saturated normal paramns and saturated mono-cyclohydrocarbons as herein described. For example, a normal heptane fraction containing an appreciable amount ofmethylcyclohexane is fractionated to form a normal heptane concentrate and a methylcyclohexane concentrate. The normal 'heptane concentrate is isomerized under optimumreaction conditions to produce isoheptanes, and the methylcyclohexane is isomerized under optimum reaction conditions to produce dimethylcyclopentane. Both products of the separate isomerization reactions are excellent blending Vagents for motor fuels, thus the products arecombined plexor supported on suitable inorganic material.

Theisomerizationofeither the normal hexane concentrate org the methylcyclopentane concentrate may be carried out in either the liquid or vapor phase without departing from the scope of this j invention. Liquid phase isomerization is preferred.

Amongthe solid inorganic catalyst supports suitable in vapor phase isomerization are the mineral or mineral-like compounds, preferably nearly completely dehydrated, such as the kaolinites, Terrana, Floridin,` pyrophyllite, apophyllite, meerschaum, serpentine, keserite, bentonite, talc, bauxite, the permutites, the zeolites and the like, as 'well as the prepared hydrated materials such as the prepared permutites and zeolites, aluminum oxides, magnesium oxides, silica, and similar compounds prepared by partial dehydration of the hydroxides and the like. Y The above materialsV are employed in admixture or in combination with an active metal halide isomerization catalyst of the Friedel- Crafts or aluminum halide type. Preferred catalysts are those comprising aluminum chloride and aluminum bromide.

The catalytic material in any suitable solid form as powder, pillules, pellets, or granules`of the desired size is employed in manners customary in the execution of catalytic processes of this type. The desired quantity of the-granular catalyst material may be `packed or otherwise contained ina reaction tube, chamber or tower and maintained at the desired temperature by suitable heating and/or cooling means while the material to be treated is passed into contact with it under the appropriate pressure for the required periodl of time. Y 'Vapor phase isomerization, generally, is executed'at a temperature not greater than about 450 F. and preferably at temperatures below 325 F. At temperatures above 450 F. losses of material due toundesirable cracking reactions are prohibitive. T he lower limit of temperature range is set by that temperature at which the desired isomerization will take place at a/practical rate. Temperatures as low as about 200 F. may be used inl some cases where pressure is low enough to assure vapor phase operation. A preferred practical loperating range is from about 200 to about 325 F. A

Unless fairly high pressures are used, the catalyst may suffer loss of activity because of the sublimation of the metal halide therefrom. Thus, it is preferred to `use pressures from about to about 400 pounds per squareinch gage. In practice theV temperature and pressure are adjusted so that the isomerization reaction is carrietil out in the vapor phase. If the reaction is effected under moderately superatmospheric pressures offrom about 25 to about 350 pounds per square .inch gage, practicable conversion of the hexanes to the desired isomeric products can be effected at relatively lower temperatures than 52,4405?? oli com-pse `under -reaction'condit'ions to `yield the hydrogen halide, may be added -to the system. The amount of hydrogen halide within the -reaction zone `at-any time should hot `be/more than -lO` I'nol per cent for best I-I'esults The most suitable `contant time -will depend Aupo'rithe particular catalyst, upon the reaction conditions, and upon the -ieed 'usdj The "con-tact `time `is chosen'so that alpracticable conversion is obtained with the minimum Side lreactions. nIn

'isomerization of hexanesinthe `Vapor phase 'at 'temperatures between -200` and I325" F., contact timesf-rom about l to about `22o-minutes are used.

AThe rcatalyst-in vapor 'phase fisomerization,

'after it has 'suffered substantial deactivation 'be- -cause of use in the process, Acan be restored to 'its initial-activityby Iadditionof an aluminum halide. `The reactivation-caribe:effected Without removing the lcatalyst Afrom the. reaction chamerably `afterthe catalyst Ehas "temporarily been *taken lout of use.

The i catalyst `A'employed-"in Sliquidfphase' isomerization i comprises essentially Afa VFriedel#Crafts 'met-al halide 'which `-W`ill 1form fa esludge complex with an oleflnic polymer, Ikerosene, or an--alkyl ate. This hydrocarbonemetal Ahalidefcon'lplex having some free metalhalid'e therein is v"a very active catalyst. The spentsludge may be LWithdrawn Vfrom -the reaction chamber-"and disposed A*oil-since itisTelati'vely cheap,` or liti may be regenerated for reuse.

LvThe'presence -in `ti-ie reaction 'system Vduring lid-uid'phase -isomerization of la hydrogen halide appears to have a beneficial effect upon the A".l-ife and-activity of the catalyst. -It inthe-rotore, 'beneci'al to the reaction -to havelrelativelyfsmall 4amounts "of `hydrogen 'chloride 'added to Atherea'etaits and presn-tduring the reaction.

1I-he pressure ofthe "reaction chamber in? liquid phase isomer-ization is f maintained so -as to :keep the heXanesthe liquidfpha'se in the chamber at fthe 'iisomeiiization temperatures. vPreferred pressures are about 200 to about 450 pounds pensquarel'inch 'gage. The reaction temperatures-for lliquid phase isomerizationfares'ome- Whatlowerithan those temperatures used in vapor` Aphase Yi`somerizatioi'i. The reaction -temperatures Jinay i range 'from about' 100- t'o `about 375`TF.,' and 'preferably from? about 11150 tof about 275 l `The v'Contact time of the ffeedi'with the -c'atalyst 'lfor lliquid phase lisomri-'Zation "imay `vary Within a relatively large rangeV without :affecting the conversion process. Contact ti-'mes from about-2 to 'about`30 minutesa're mostdesirable.

The `reaction chamber Fifor -f liquid phase isomerization may befpacked "Wi-thi'a ysolid. catalyst supporting material or carrierA agent, As'uch 1was carbon fRaschig ringsgfof such la nature ras-"to have a high wettability `by the catalyst sludge. The high wettabilityof the supporting material `assures a large hold-up of the catalyst sludge. This packing material is ordinarily relatively inert with respect to reactants and catalyst. Examples are Raschig rings, Berl saddles, etc., m-ade from carbon, glazed or unglazed porcelain or other ceramic Wear. Other types of packing which may be used include bauxite, activated alumina, fullers earth, silica gel which may have adsorptive properties enhancing the activity of the sludge catalyst. The reaction for liquid isomerization may contain no supporting material at all, but instead intimate contact between re- `actants and catalyst is -eiected by means of stirrers within the reaction chamber itself.

Various other isomerization catalysts may be --used which are suitable for isomerization of hexanes, such as hydrogenfluoride, boron trifluoride', mixtures of hydrogenlluorde and boron trifluoride, and sulfuric acid. Reaction conditions of isomerization yand the catalyst used for the Various isomerization` steps may be altered and various modifications Will become4 apparent to those skilled in the `art Withoutdeparting from the scope of this invention.

` Preferably, the normal hexanepconcentrate is isomerized at` a temperaturebetween ,about 210 and about 375 F. and under sufficient pressure to maintain the reactionmixture in theliq-uid phase. An aluminum chloride-hydrocarbon complex containing between about 50 and about weight per cent aluminum chloride is preferred as the catalyst. The methylcyclopentane 'concentrate is isomerized at a Atemperature between about and 200 F. `under :suicient EXAMPLE i I A normal hexane Vfraction was isomerized without preliminary .fractionation The following is the approximate :feed and eluent compo,- sitions.

Per ent Pentanes and lighter 4. 8 Isoliexaues 5 52. 9 Methylcyclopentane.. 2l 9. 8 Cyclohexane 4 1 7. 2 Normal Hexane v '.70 19. 2 Heavier hydrocarbons 6. 1

Normal: hexane conversion =.72 .4% `lsohexane yield -p er normal hexanereacted 94 .1% -Methylcyclope11tane"reacted 53.8% 1 =Cyclohexane yield, penmetliylcyclopentane .reacted29.8%

. EXAMPLE 1I A normalfhexane concentrate'was prepared by preliminary fractionation according to this invention and isomerized under optimum reaction conditions for the formation of isohexanes. The following is 4the approximate feed and eiuent compositions.

Eluent Feed Composition, Weight Per Cent Corgsgtmn Per Cent Pentanes and lighter 3. 8 Isohexanes 55. 1 Normal hexane 87. 9 26. 3 Methylcyclopentane 12. 1 2. 2 Cyclohexane 3. Heavier hydrocarbons 9. 6

n 100. o 10o. o

Normal hexane reacted= 70.1%

Isohexane yield per normal hexane reacted=89.5% Methylcyclopentane reacted=81.9%

Cyclohexane per methylcyclopentane reacted=31% EXAMPLE III A methylcyclopentane concentrate was prepared by preliminary fractionation according to this invention and isomerized under optimum reaction conditions for the formation of cyclo- Normal hexane reacted=l1.9%

Isohexane yield per normal hexane reacted=95% Methylcyclopentane reacted=51.l

Cyelohexane yield per methyleyclopentane reacted=85.4%

The 85 per cent yield of cyclohexane in Example III as compared to a 29 per cent and 31 per cent yield in Examples and II, respectively, indicates the desirability of concentrating methylcyclopentane in a hydrocarbon fraction to at least about 40 per cent of the fraction.

EXAMPLE IV Normal hexane substantially free from other hydrocarbons was isomerized under ,optimum reaction conditions, and the following composition of the eiiiuent was obtained.

Composition of eluent weight per cent Isobutane a 15.3 Isopentane 14.9 Normal pentane 1.7 Neohexane 4.1 Other isohexanes 13.1 Normal hexane 37.3 Heptanes and heavier 13.6

Conversion normal hexane=62.7%

Isohexane yield per normal hexane reacted=27.4%

Since the highest yield of isohexanes was obtained when methylcyclopentane was present in substantial amount in the reaction mixture, it is evident that a methylcyclopentane content of the isomerization feed above about 12 weight per cent is highly desirable to obtain a good yield of isohexanes Example IV adequate illustrates the degree of disproportionation resulting when relatively pure normal hexane is isomer-ized without the presence of a disproportlonation inhibitor, such as methylcyclopentane or other naphthene.

I claim: Y 1.` A processk for isomerizing a hexane fraction comprising between about 65 and about 80 weight per cent normal hexane and between about 20 and about 35 weight per cent methylcyclopentane which comprises fractionally distilling said hexane fraction to form a normal hexane concentrate comprising between about and about 93 weight per cent normal hexane and a methylcyclopentane concentrate containing at least about 40 weight per cent methylcyclopentane, isomerizing said normal hexane concentrate at a temperature between about 210 and about 375 F. under sufcient pressure to maintain the reaction mixture in the liquid phase and in the presence of an aluminum chloride-hydrocarbon complex containing between about 50 and about 80 weight per cent aluminum chloride, fractionally distilling aneffluent from said normal hexane isomerization to separate isohexane and normal hexane, recycling said normal hexane to the aforesaid isomerization, simultaneously isomerizing said methylcyclopentane concentrate at a temperature between about and about 200 F. under suilicient pressure to maintain the reaction mixture in the liquid phase and inthe presence of an aluminum chloride-hydrocarbon complex containing between about 10 and about 45 weight per cent aluminum chloride, fractionally distillng an eiiuent from said methylcyclopentane isomeriaztion to separate cyclohexane and methylcyclopentane, recycling a portion of said methylcyclopentane to said methylcyclopentane isomerization, introducing another portion of said methylcyclopentane into said normal hexane concentrate in an amount sufficient to maintain a naphthenic content therein or at least 7 weight per cent, and combining said isohexane and said cyclohexane as a motor fuel blending agent. Y

2. A process for isomerizing a hexane fraction comprising between about 65 and about 80 weight per cent normal hexane and between about 20 and about 35 weight per cent methylcyclopentane which comprises fractionally distilling said hexane fraction to form a normal hexane concentrate comprising between about 85 and about 93 weight per cent normal hexane and a methylcyclopentane concentrate containing at least about 40 weight per cent methylcyclopentane, isomerizing said normal hexane concentrate at a temperature between about 210 and about 375 F. under suflicient pressure to maintain the reaction mixture in the liquid phase, and in the presence of an aluminum chloride-hydrocarbon complex containing between about 50 and about 80 weight per cent aluminum chloride, simultaneously isomerizing said methylcyclopentane concentrate at a temperature between about 100 and about 200 F. under suilcient pressure to maintain the reaction mixture in the liquid phase and in the presence of an aluminum chloridehydrocarbon complex containing between about 10 and about 45 weight lper cent aluminumchloride, and combining effluents from said respective isomerizations. Y 3. A ,process for isomerizing a hexane fraction comprising between about 65 and about 80 weight per cent normal hexane and between about 20 and about 35 weight per cent methyleyclopentane whichv `comprises fractionally dis-- tilling said hexane fraction to form a normal hexane concentrate comprising between about 85 and about 93 weight per cent normal hexane and a methylcyclopentane concentrate comprising at least about 40 weight per cent methylcyclopentane, isomerizing said normal hexane concentrate at a temperature between about 210 and about 375 F. under sufficient pressure to maintain the reaction mixture in the liquid phase, and in the presence of an aluminum 'chloride-hydrocarbon complex containing between about 50 and about 80 weight per cent aluminum chloride, fractionally .distilling an effluent from said normal hexane isomerization to separate isohexane and normal hexane, recycling said normal hexane to the aforesaid isomerization, simultaneously isomerizing said methylcy-clopentane concentrate at a temperature between about 100 and about 200 F. under sufficient pressure to maintain the reaction mixture in the liquid phase and in the presence of an aluminum chloride-hydrocarbon complex containing between about 10 and about 45 weight per cent aluminum chloride, fractionally distilling an eluent from said methylcyclopentane isomerization to separate cyclohexane REFERENCES CITED The following references are of record in the tile of this patent:

UNITED STATES PATENTS Number Name Date 2,379,749 Ross et al., I July 3, 1945 2,382,446 Ross et al., II Aug. 14, 1945 2,394,797 McAllister et al. Feb. 12, 1946 OTHER REFERENCES Journal Amer. Chem. Soc., vol. 61, July 1939, pages 1717-1720 (article by Glasebrook and Lovell).

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