US2394906A - Production of motor fuel - Google Patents

Description

F. E. FREY Feb.`l2, 1946. i

PRODUCTIN oF MOTOR 'FUEL Filed. Feb. 27, 1942 INVENTOR FREDERICK E. FREY MMMQW I ATTORNEY HOLVNOILQVHd .M mZEml-O,

Paiement. 'laz 1946 l l escasos PRODUCTION or Moron FUEL I vFrisdrank E. Frey, Baruesviue, okia., assigner to f Phillips Petroleum Company, a corporation of Delaware ,Application February 27, 1942, sei-iai No. 432,679v

(ci. 19e-1o) This invention relates to the conversion of hy.- drocarbohs. More particularly, it relates to the production of motor fuel from realtively lowboiling hydrocarbons by a process in which hydrouoric acid is used as a catalyst. This application is a continuation in part of my copending as distillation, to recover the free hydrogen iluoride, and/or thermal decomposition and distillation, to recover the organically combined fluorine as hydrogen fluoride. v

I h'ave now found that spentor partly deactivated hydrofluoric acid from the alkylating step application, Serial No.7 315,063, flled January 22,

1940` (Patent No. 2,322,300?, and Serial No. 426,- 627, led January 13, 1942. x

An object of this invention is to convert relatively low-boiling normal paraffinv hydrocarbons,

suchas normal butane and normal pentane, to higher-boilingsaturated hydrocarbons.

A specic obj'ect of this invention is to produce j a motor fuel stock from relatively low-boiling paraiiins by a process in which used hydrouoric aoidcatalyst from an alkylation step is used as a catalyst for isomerizingv normal parailin's to the isoparatlins required for the alkylation step.

Other objects and advantages of this invention will be apparent from the accompanying description and discussion.

In the prior art of hydrocarbon conversion, it has been shown that isoparamnsof relatively low molecular weight, such as isobutaneand/or isopentane4 can. be reacted in the presence ofl concentrated hydrofiuoric acid at a lcomparatively low temperature, for example, in the range of Y Ofto 200 F., with alkylating reactants, such as olefins having 3 to 5 carbon atoms per molecule and corresponding alkyl compounds such as alkyl' halides, alcohols, esters, ethers, and the like, preferably those of ,secondary or tertiary structure. to produce motor-fuel hydrocarbons thatjhave high antiknock values and that are suitable for 'use in aviation gasoline. Normal paramns, such as normal butane .and/or normal pentane, can also be alkylated, but only under considerably more drastic conditions, so that the product Iobtained by alkylating normal paramns is of lower quality in respect to octane number, and is produced in lower yield than that obtained by allavlating the corresponding isqparailins.

In such' alkylation processes. the hydrouoric acid'eventually becomes so spent or deactivated by acid-soluble organic and nuoro-organic material that it is 'unsuitedfor continued use: the

1 Spending or deactivation is especially rapid at elevated temperatureafsuch as those'required for the alkylatlon ofnormal' paramns. Disposal of the spent. acid is a considerable problem, because can -be advantageously used as an isomerizing catalyst to convert relatively low-boiling normal parains, such as normal butane and/or normal pentane, into isoparamns, such as isobutane and/ orisopentane. I have also found that the emuent from such a conversion can be used as feed to han alkylation step, wherein theisoparafllns are converted to higher-boiling motor-fuel hydrocarbons. Furthermore, I have found that the acid from the isomerizing conversion can .be puried in a relatively simple manner so that it can be re-used in the alkylation step.

An understanding of' some aspects of my in- Yvention may be aided by the accompanying drawing, which is a schematic flow-diagram. of one arrangement of equipment for practicing theinvention.

In the alkylating step of this invention, alsuitable hydrocarbon material, for example` a mixture of normal butane and isobutane, isadmittedto alkylator Il, as through inlet II, valve I2, and pump I 3 and/or through conduit 'I0 and pump 20. In alkylator Il, it is mixed under alkylating conditions with an alkylating reactant, which 'may be admitted throughinlet I5, valve I6, and

pump I1, and with concentrated hydrofiuoric acid, preferably anhydrous, which may be admitted through inlet Il, valve I9, and pump 20 and/or through conduit 10 and pump 20.

In the feeds to this alkylating step the weight ratio of isoparamns to olefins, or other alkylating reactant, preferably is in the range of 2:1 to 20:1

i troduced into the reaction mixture under condi- I tions of high turbulence and/or in multipointwise v 'fashion, so that it is rapidly mixedwith the isoo1' the corrosive nature of the acid; lfurth'rmore,

heretofore no use for thejs'pent acid has been g known. Therefore, in commercial alkylation, it

. is necessary to provide acidfrecovery steps, such or more,` and the weight ratio of hydroiiuoric acid to total hydrocarbons preferably is in the range 0.2:1 to 4:1, Th'e olefin preferably is inparamn reactant. This procedfure is advantaseous inorder to favor lthe desired olefin-isoparamn ljunctures, or alkylation reactions. and to hinder undesirable olefin-olefin junctures, or D013?- f merization' reactions. Suitable operating'conditions'l in alkylator Il are a ,tenrrperaturev in the v range -of 30 to 150". F., apressure sufncient to .maintain'all components in the liquid phase, and

. a time of about Ito 30 or more minutes.

` .'I'n'e resulting mixture passes through conduit 2i A"and vvalve llltoseparator 2l, wherein it is '38 for use as catalyst in an isomerization-step to be described.

The lighter or hydrocarbon phase from separator 23 is passed through valve 24 and conduit 25 to fractionating means 26, in which it is separated into the following six fractions: (1) a relatively minor fraction of relatively inert and difflcultly condensable gases, which is removed through outlet 21 having valve 28; (2) a fraction comprising propane and hydrogen iiuoride, which is passed through conduit 29 and valve 30 to separator 3l; (3) one or more fractions comprising isoparafins, such as isobutane and/or isopentane, and at times also some hydrouoric acid,

which are recycled to pump I3, as through valve 32 and conduit 33; (4) 'one or more fractions comprising normal pa'raiiins,y such as normal butane and/or normal pentane, which are passed to pump 36, as through valve 34 and conduit 35; (5) a fraction of highly branched parafnic reaction products boiling within the motor-fuel range, which is withdrawn through outlet 431 having valve 38, and (6) a relatively high-boiling hydrocarbon residue, which is withdrawn through outlet 39 having valve 40. Fractionating means comprises whatever distilling columns and auxiliary equipment are necessary or convenient for effecting the separations indicated, as will be readily appreciated by those skilled in the art.

In separator 3l the fraction comprising propane and hydrouoric acid is separated into two phases as by cooling and gravitational or centrifugal means. The lighter or propane phase may be withdrawn through outlet 44 having valve d5; the heavier or hydrouoric acid phase is passed through valve 46 and conduit 35 to pump 30. If desired, separator 3| may be by-passed, the hydrogen uoride and the propane then passing 'glrough valve 4l and conduit 35 directly to pump In the isomerizing step of this invention, the materials from the alkylating step that come to pump 36 through conduit 35, that is, a mixture of normal paraflins, such as propane, butane, and

. normal pentane, with used or spent hydrofiuoric acid, is forced by pump 36 through heating coil 48, valve 49, and conduit 50 to reactor 5 l.

In the feed to reactor 5i, the ratio of hydrouorio acid to hydrocarbon is preferably in the range from about 0.2:1 to 4:1 or more by weight; usually, operating with an acid-to-hydrocarbon ratio within this range will effect the maximum conversion of normal paraffins to isoparamns.-

These proportions are obtained by controlling the relative proportions of spent acid from separator 23 which pass through valves 4 I and 43, respectively. Also, if desired, additional normal 'paraffl'n and/or hydrotluoric acid may be admitted to the system, as through inlets 52 and/or 53 and valves 54 and/or B5, respectively.

The reaction temperature in reactor 5I may be within the range of about 250 to l000 I". A

ment and operating costs, to use a pressure` in the range of 250 to 1000 pounds per square inch. The reactiontime may be within the range of from about 1 to about 300 minutes, depending the temperature, since the time re- Y chieiiy upon Y quired decreases with increase in temperature. If the reaction time is very short, such as 1 `to 5 minutes the reaction can be completed in coil 48 4or an extension thereof; whereupon reactor 5I may -be icy-'passed or removed fromv the system.

Preferably, the reaction zone is packed with a y contact mass, such as steel turnings,. alumina,

or other material resistant to corrosion by hydroiiuoric acid and suitable for aiding the reaction' and heat transfer.

The resultant mixture from reactor 5I may be passed through valve 56 and conduit 5l to partial condenser 58, wherein, by a suitable cooling means, relatively high-boiling material, such as hydrocarbons boiling above about the pentane range, water, acid-soluble material, and the like, are liquened. Suitable conditions in the partial condenser are a temperature in the range of 125 to 400 F. and a corresponding pressure in the range of 15 to 400 pounds per square inch. The optimum conditions for any particular case are readily determinable by trial and/or from wellknown vapor-pressure relationships of the various constituents. Conditions outside the ranges given above may 'be used, if desired or necessary.

The resulting mixed-phase mixture from partial oondenser `5l; is passed through conduit 59 and valve t0 to separator 6i, wherein it is septemperature within the range 400 to 800 F. is

usually preferred; at low temperatures the rate of reaction is low, and at high temperatures some cracking and carbon formation occurs. The pressure may be within the range of atmospheric to 5000 pounds per square inch or more; usually, it is preferred, for reasons of economy in equiparated into a gas phase and a liquid phase, as by gravitational or centrifugal means. The temperature and pressure conditions should be, as nearly as possible, the same as in partial condenser 58. The liquid phase, kwhich comprises mainly hydrocarbons andacid-soluble substances boiling approximately in the hexane range and above, is withdrawn through outlet 62 havingV valve 03. k The gas phase is passed through valve @d and conduit 65 to condenser and separator 66.

in condenser and separator 00, the gas phase from separator 5| is cooled and liquefied. The resulting mixture of acid and hydrocarbon phases, which comprises the isoparaiiins produced in reactor i, is passed through valve 69 and conduit ill to pump 20 for use as feed in the alkylation vheavy impurities areremoved from the catalyst and from the system. The material passed through valve 69 and conduit l0 to the alkylation step therefore contains lsoparafins and also concentrated hydroiuoric acid in a purified state suitable for catalyzing` the subsequent'alkylation reaction. In some instances it may be possible to pass a portion, or all, of the isomerization ellluent directly to the alkylation step, as through conduit l and valve, 14, with valve 56 partially or completely closed. Such a procedure may be followed when the impurities in the elliuent from the isomerization are small, or negligible, in amount. At other times it may be desirable to subject the isomerization eilluent to more complete separay tion, obtaining thereby in various separate frac- Y step is passed equipment, not shown, as will-be appreciated by v those skilled in the art. Any fraction-so recovered may be used in other steps of the process, and may be introduced thereto through one or more appropriate conduits.

It is contemplated that the hydrofluoric acid can be, and in many instances will be, the isomerization catalyst, and I have obtained satisfactory isomerization and disproportionation of aliphatic hydrocarbons using `hydroiluoric acid as the sole catalyticy material. However, in the broadest concept of the present invention, it is to be understood that the isomerization may be carried out in the presence of other material in addition to hydrofluoric acid. Such other materials may serve to enhance the catalytic activity of hydrofiuoric acid; such as material which provide large surfaces, to promote the ractivity of hydrofluoric l acid, or to cooperate with the hydroiiuoric acid,

members of thislatter group having, themselves,

independent isomerization catalyzing activity.

Included among these groups. for use together with hydrofluoric acid', are the oxides and halides of beryllium, sulfur, tungsten, magnesium, alumi num, zinc, titanium, thorium, iron, copper, tin,

' vanadium, antimony, arsenic, chromium, molybdenum, manganese, nickel and cobalt, their salts c of difiicultly volatilizable acids, either synthetic or natural. Of the naturally occurring materials, I prefer those of large surface such as various clays, bauxite, brucite, etc. Sometimes activatedcharcoal ,may also be used to advantage. These various materials, or various ones oi' the materials mentioned may be used in granular form, as a powder, or may be pelleted, as may be found found most eiective or desirable in any particular instance.

A few o'i the many aspects vc: my invention are illustrated by the following example, which is illustrative but not necessarily limitative of the invention.

In an arrangement similar to that illustrated in theA accompanying drawing, normal butane' is prises relatively large proportions of normal parafhns and only small proportions of isoparainns, it is preferably introduced to fractionating means 28, as through inlet 'ii having valve 12, instead of directly to alkylator il; whereupon the isoparanins are separated out and passed to alkylator i4, and the normal paraiiins are passed to the isomerization step. In another modification, the parafiinic feed material, instead of being ad- 'mitted directly to alkylator i4, or to fractionating means. 28, is admitted through inlet 52, valve M, and pump 38 to the isomerization step; this modification is particularly advantageous when the feed material has mostly low-boiling normal parailins but practically no loW-boiling isoparail'ins. Additional pumps, valves, conduits, coolers, fractionators, and other equipment, such as are well-known in the art qi hydrocarbon conversion, may be used wherever theyare necessary or convenient. 'I'he scope oi' my invention should 'not be unduly limited by the numerical values discussed herein.

I claim:

l. Inaprocess for alkylating an isoparamn in the presence of hydroiluoric acid, the improvement which comprises mixing a normal paraiiin with usedv hydroiluoric acid from an alkylating step, subjecting the resulting mixture to isomer-V izing conditions in an isomerizingstep, and using atleast part of. the eiiiuent from the isomerizing charged to -the isomerization stage, as through inlet 52; normal butylenes and concentrated lilydrofiuoric acid are separately charged to the alkylation stage, as through inlets I5 and il, re-

spectively. All of the acid used in the alkylation step.

The alkylating conditions are approximately las follows: temperature, 102 F.; pressure, 150

pounds per square inch; time, 5 minutes; isobutane-to olefin molal 'ratio (in the incoming ma terlals to the alkylation reactor), 11.5; hydrocarbon-to-acid weight ratio, 1.0; and rapid mix- 11,18 to maintain intimate contact between the acid A and hydrocarbon phases.

'I'he isomerizing conditions are approximately' as follows: temperature, 850 F.; pressure, 2,000 pounds per square inch; time,'10 to 80 minutes. From this process, there is produced in a yield of aboutv 160 per cent, based on the weight of olefins charged, an aviation motor fuel which has a clear octane number of about 90.

In this process, the acid eiliuent from the alkyl ation step is used as catalyst in the isomerization step; it is then purified by partial condensation,

as in condenser 68, and is returned to the alkylation step.

My invention provides a process for utilizing normal parafllns, particularly low-boiling paramns such as normal butane and/or normal pentane, to produce relatively high-boiling saturated as catalyst to the isomerization step as ieed material in the alkylating step.

2. In the process of claim 1, cooling the eiiiuent from the isomerizing step to remove by partial condensation material which boils above about the pentane range prior to using said efiiuent as feed material in the alkylating step.

3. A process for producing motor fuel, which comprises: alkylating a low-boiling isoparaiiin of four to five carbon atoms per molecule with an olefin of three to 'five carbon atoms per molecule in the presence of concentrated hydrouoric acid in an alwlation step; separating the effluent from -said alkylation step into a hydrofluoric acid iraction, at least one low-boiling isoparaiiin fraction, at least one low-boiling normal paraiiin fraction, a motor-fuel fraction, and a heavier-than-motorfuel fraction; removing from the process said motor-fuel and heavier-thansmotor-:fuel fractions; recycling said low-boiling isoparamn 'fraction to the alkylation step; Passing said hydroiluoric acid and low-boiling normal paraffin fractions to an isomerization step in which such conditions are maintained that normal paraflins are' isomerized to a substantial extent by hydro fluoric acid into isoparaiiinm'freeing the resulting effluent-from the isomerization step from materialfboiling above about the pentane range by partial condensation; and passing the thus freed eiiluent to said alkylation step.

4. A process for producing normally liquid iso- I paramnic hydrocarbons from lower boiling norhydrocarbons of high antiknock value that are mal paradin hydrocarbons etat least i'ourv carbon ralkylatirig reactant in vin the presence of concentrated hydrouoric acid to produce a low-boiling isoparailn hydrocarbon, reacting said isoparaffin so produced with an the presence of concentrated hydrouoric acid as the alkylation catalyst to produce normally liquid isoparafns ofliigher molecular weight, separating from effluents of said alkylation a hydrocarbon traction containing liquidv isoparafns so produced as a product of the process, separating also from eiiluents of said alkylation a hydrofluoric acid fraction, Yand passing said fraction to said isomerization.

5. A process for producing normally liquid isoparafiinic hydrocarbons from lower boiling normal parafiln hydrocarbons of at least four carbon atoms per molecule, which comprises subjecting such a normal paraflin to catalytic isomerization in the presence of concentrated hydrofluoric acid as the isomerization catalyst to produce a lowboiling isoparain hydrocarbon, reacting said iso-l paraiiin so produced with an alkylating reactant in the presence of concentrated hydrofluoric acid as the alkylation/ catalyst to produce normally liquid isoparains of' higher molecular weight, separating from efuents of said alkylation a hydrocarbon fraction containing liquid isoparafns so produced as a product of the process, separating also from effluents of said alkylation a hydrofiuoric acid fraction, and passing said fraction to said isomerization as the isomerization catalyst.

6. A process for producing normally liquid isoparalnic hydrocarbons from a mixture of low- .boiling isoparaflins and normal parains of at least four carbon atoms per molecule, which comprises separating an isoparailln fraction and 'a normal paraiiln fraction from said mixture, re acting said iso parafiln fraction in an alkylation step with an alkylating reactant in the presence of concentrated hydrouoric acid as the -alkyla= tion catalyst to produce higher-boiling isoparaf- `iins, separating from eiiluents of said alkylation higher-boiling isoparafns vso produced as products of the process, separating also from effluents of said alkylation an impure liquid hydroluoric acid, passingA said liquid hydroluoric acid together with the aforesaid nonmal paraflln fraction to an lisomerization step to isomerize said normal paraiins,

parailins and form low-boiling isoparafns, and

recovering low-boiling isoparafilns so formed andv paraiilnic hydrocarbons from lower boiling paraf- 1in hydrocarbons, which comprises subjecting aV low-boiling normal paraiiln hydrocarbon of at least four carbon atoms per molecule to isomerization in the presence' of hydrofiuoric acid as the isomerization catalyst at a temperature within the range of 250 to 1000" F. and a superatinospheri'c pressure to produce low-boiling isosubjecting the effluent of said isomerization to cooling and partial condensation to condense material .boiling above pentanes and removing material so condensed from the system, subjecting uncondensed material/to further cooling and condensation to condense hydrofluoric acid and low-boiling isoparaflins, separating rnaterial so condensed from uncondensed gases, passing. the last said condensed material to an alkylation zone and reacting isoparafilns contained therein with an added alkylating reactant .in the presence of said hydrofluoric acid and as the allrylation catalyst to produce normally liquid isoparains, separating from the effluent of said alkylation a liquid hydrofluoric acid phase, and passing said hydrofluoric acid phase-to said isomerization. Y

8. In a process for producing parafn hydrocarbons boiling in the motor fuel range from lower-boiling parafn hydrocarbons, the improvem ment which comprises subjecting a normal paraf lin an alkylation step with an fin of four to ve carbon atoms per molecule in an isomerization step to catalytic isomerization in the presence of used hydrofluoric acid obtained from a subsequent alkylation step, separating from efiluents of said isomerization a low-boiling isoparafiln' so produced, reacting said isoparaiiin alkylation reactant in the presenceof concentrated hydrouoric acid as the alkylation batalyst to produce parafflns boiling in the motor fuel range, passing eiiluents of said alkylation to a separator and effecting a separation between a hydrocarbon phase and a hydroiiuoric acid phase, and passing at least a portion of said hydrofluoric acid phase to said isomerization step.

FREDERICK E. FREY.

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