US2371402A - Hydrocarbon synthesis - Google Patents

Description

Match 13, 1945. G. l. MA''EER ETAL HYDROCARBON SYNTHESIS patented Mer. 13, 1945 George 1. Mateer, mountainside. and Avery n.

George, Cranford, N. J., assignors to Standard Oil Development Company, a corporation of Delaware Application peeemher 11, 1942, serial No. 468,658

(o1. 26o-sass.)

6 Claims.

The present invention relates to the production of hydrocarbons fby catalytic means, said hydrocarbons being highly useful in the supply- Y ing of motor fuels or in the production of motor fuels made by alkylation processes. A more particular aspect of the present invention resides in a combination process in which feed stocks containing isoparafns, normal paramns and olens, both lstraight and branched chain, are subjected to catalytic alkylation reactions to produce alkylate boiling within the motor fuel range in which the relatively inert normal'parailns are higher aviation fuels is a welcome improvement Y in the art.

In describing the process, reference will be made chiefly to a cracked renery C4 cut and one or more of its components, 'butr it is distinctly to be understood that the presenty invention is not restricted to such a feed stock, it being entirely vpossible to use field butanes which have been separated from the reaction mixture, subjectedA action and the remainder going to a catalytic.

dehydrogenation reaction.

In .the petroleum industry it has often been diillcult to adequately balanced feed stocks suitable for alkylation so as to produce from given,

quantities of recycle gases available the highest yields of aviation gasoline or high octane number motor fuels by the alkylation method. Paraugmented With oleilns from extraneous sources, to use combined Ce-Cs refinery fractions from cracking operations, or to use Cs fractions alone which contain isopentane, normal pentane, and the straight and branched chain oleilns.

The 'operation of the combined isomerizationallo/lation process is such that the two processes function substantially as a single unit although the reaction conditions in each of the two processes are independent of one another. after thefeed stock containing iso and normal paralns and olens is subiectedv to alkylation the reacted mixture is fractionally distilled to remove a fraction rich in isoparaln reactant, a fraction rich in unreacted normal parafln, and an alkylate. The operation of the fractional distillation may be so controlled as to vary the compositionof die normal parailin fraction, leaving in it moreor less of the isoparailln which is orditicularly in small renery operations there may be an apparent scarcity of some particular component required in the alkylation reaction.

Thus, for example, isoparafns or the olefin, or both, may be relatively scarce although large `quantities of basic 'materials from which these the refinery gases availableand to Woduce from vthese renery gases the highly desired alkylate.

above described. The present process Ais designed which utilizes to a vmost economical advantage to fully utilize existing refinery gases and to.

accomplish this utilization ina most economical and advantageous manner.

present invention, considerable flexibility in the operation of these units is possible. without de- As will be seen .from a fuller understanding of the process of the parting from the general principles of the invention as herein more fully outlined. The prob'- lem has always been to improve overall yieldsl of desired products while utilizing existing4 materials from refining operations. Therefore, any practical method for the manufacture on a commercial scale of high octane blending agents for s use in the preparationof octane ,number and narilyreturned or recycled to the 'alkylation unit. This is carried out for the reason that when this normal parafdn fraction is conducted to the isomerization unit, control of the degree or amount o! isomerization in the present invention is carried out in a novel manner, as follows:

The normal parafiln feed stock-,is heated to a substantially constant predetermined temperacoming feed stock to that unitand its vapor pressure is likewise determined. A device is employed which is actuated by the difference in the vapor pressure oi' the incoming feed and the outgoing reacted mixture, and depending upon the increase `in the percentage of isobutane contained in the reacted mixture, the valve through which the feed stock is introduced into the isomerization unit is 'either opened or closed-by means of .the pressure dierential actuating means in lorder to control they extent of Vconversion ofnormal to iso butane, so that a substantially constant amount of isoparaiiln is introduced back into the alkylation unit so as to maintain a substantially constant source of supply to that unit of isoparailin reacted with olefins to form allwlate. This replacement of reacted isoparaflins is therefore dependent upon the composition of the incoming feed stock because the rate of introduction of that feed stock is controlled by the vapor pressure differential means heretofore described. It is therefore readily understood that one method of controlling that means, or, in other words, of increasing or decreasing the differential in vapor,pressure, is 'by permitting small or large aliquot portions of isoparaln to be admixed with the normal paraffin going to the isomerization unit, and this is accomplished by a variation in the fractional distillation conditions maintained in the isoparaffln-normal-parafiin fraction distillation tower. As will be more fully described hereinafter, the

effluent from the isomerization unit goes directly to the alkylation unit or may be returned to and admixed with the alkylated mixture going to the fractional ldistillation tower for effecting the separation of isoparan from normal paraiiins and from alkylate.

Although the invention is not restricted to any particular method of accomplishing the alkylation reaction, the isomerization reaction and/or the dehydrogenation reaction, for purposes of illustration it may be stated that the alkylation can be carried out-in the presence of sulfuric acid of from 90 to 100% concentration. at a temperature between about and about 75 F., under sufficient superatmospheric pressure to maintain liquid phase operation; that the isoparaifin should be present in substantial molar excess over the olefins being reacted, and that the mix ture should be vigorously agitated to maintain a thorough contacting for a sufficient period of time to bring the reaction to substantial equilibrium. In the case of the isomerization reaction, a suitable methodiof carrying it out is to employ aluminum chloride, and in the case of normal butaneisomerization to use temperatures of between about 200 and about 400 F. Likewise, a halogen-containing promoter is desirable and this may be selected from any one of a number of suitable substances, hydrogen chloride being the preferred one. Liquid or vapor phase reaction may be employed and the aluminum chloride maybe deposited on a suitable carrier such as Porocel or other highly porous substance for greater contacting with the feed stock. In the case of the dehydrogenation unit, the operation may be carried out using a catalyst of chromial and alumina gels at atmospheric pressure and under a temperature range of from 1000 to 1400* F., at a throughput of from 100 to 1200 volumes of feed stock per volume of catalyst per hour. Each of these types of reactions are well known and the speciiic details, specific catalysts and reaction conditions form no part of the present invention other than in the combination as shown. As will be more fully explained, the invention lies in the subsequent isolation and treatment of the ei'iluent from the alkylation unit to condition the inerts and unreacted portions of the feed thereto for further use in alkylation.

Referring'to the accompanying drawing, which is a more or less diagrammatic representation in sectional elevation of a plant designed for carrying out the process of the present invention, the

feed stock employed will be, for illustrative purposes only, described as a cracked refinery C4 A cut containing isobutane, normal butane, normal butylenes and isobutylene.

Such a feed stock is introduced into line 2 by means of open valve 3 and pumps not shown into alkyla'tion unit 4 where it is contacted with suifuric acid or other suitable alkylation catahrsts. The reacted etlluent, substantially free of acid, emerging therefrom through line 5 is fed through open valve 6 into fractionating tower 'I operating under such conditions of temperature and pressure wherein a substantially pure fraction of isobutane and any lighter boiling hydrocarbons present is passed overhead through line 8, controlled by valve 9, and recycled back to the feed line 2 for further use in the alkylation unit. It may be necessary at times to purge part of the stream in line 8 in order to prevent appreciable build-up of Ca and lighter components in the reactor by means not shown. A bottoms from this tower I which consists of normal butane and alkylate, together with small amounts of isobutane, is then passed by means of line I0, controlled by valve Il, into line i2 and then into fractionating column I5 which is operated under conditions effecting a separation of main quantities of normal butane from the alkylate, it being understood of course that any quantities of isobutane not; taken overhead from fractionating column 'I are removed with the normal butane overhead from fractionating column I5. The normal butane is then, by means of line I5 and open valve Il, conducted to either line 4I controlled by valve 42 or line BI controlled by valve 82, or both, depending upon the openings set in valves 42 and 82.

The alkylate, together with any small amounts of normal butane which have not been taken overhead to line I6, is withdrawn through line I8 controlled by valve I9 and conducted into the final fractionating tower 34 for the removal of light alkylate throughline 35 controlled by valve 38, medium cut alkylate through line 31 controlled by valve 38, and the heavy bottoms through line 89 controlled by valve 40.

' In operating the alkylation unit, a single stage circulating stream emulsion type of reactor or a two-stage operation in which the olens are first absorbed in sulfuric acid and the isoparafn then contacted with the olefin extract under alkylation conditions may be employed, 'I'his latter type is advantageous particularly in cases wherein the feed stock does not contain only a single olefinic hydrocarbon but may contain Cz, C3, C4

and C5 olens and the like, in which case it may be desirable to selectively extract only the C4 olen or only the Ca olen, as the case may be, or both, leaving unabsorbed the undesired olen. As stated, two-stage alkylation is preferable in such an instance.

The normal butane, unless removed from the alkylation system to compensate for the introduction of fresh quantities of normal butane,

builds up indefinitely since it is inert in the alkylation unit, hence at least suflicient normal butane should be removed through line I8 for further processing so as to maintain the normal butane level at least constant in the alkylation unit and to compensate for the introduction of further quantities of normal butane in the feed stock in line 2. This normal butane, which may contain small or large amounts of isobutane, depending upon the fractionation conditions in fractionating columns I and I5, is conducted through line 4I controlled by valve 42 into a vapor pressure recording unit 43 having a constant temperature jacket I4. The vapor pressure is measured for the purpose of the present invention, in the case of normal butane, at about 100 F. In other words, jacket 44 would be maintained about at 100 F. The eliiuent from the heater and constant temperature zone 43 passing through valve 45 and line 45 goes to' absorber 41 and passes'downwardly therethrough while simultaneously therewith there is passing upwardly by means ofy line 50 controlled by valves il and 5S, hydrogen chloride which is introduced into this same absorber by means ofv recycle line 58, and any unabsorbed hydrogen chloride is released from the system through line 48 controlled by valve 49. The temperature and throughput maintained in the absorber are such as to give a hydrogen chloride concentration roughly of from 3 to 20% hydrogen chloride. This fat lid-i 'uor, that is normal butane containing hydrogen chloride, is passed by means of line 52 through control valve 58 into the isomerization unit 54. The reacted mixture from isomerization unit 5d passes through line 55 through open valve 5B into the stripping tower 51 where, the hydrogen chloride and any lighter degradation products which may have formed, such as ethane, methane, propane, are removed overhead and recycled to the absorber 41. The degradation products, together with any uinabsorbedv hydrogen chloride, are removed from the system through line 48 controlled by valve 49 as heretofore specified. The bottoms from the stripping operation and which consist primarily of normal and isobutane are passed through lines 50, 53 and open valve BQ into a temperature controlled vapor pressure recorder 55 similar to that of temperature controlled vapor pressure Yrecorder 43 wherein the vapor pressure again at 100 F. is measured, the 100 F. temperature being` insured by heating or cooling liquids in jacket 55. Vaper pressure recorders 4S and 35 .are conventional pressure recorder mechanisms with a pneumatic device added which operates to produce an air pressure output of each recorder having a predetermined relation to the respective actual vapor pressures.

4Recorders 43 and S5 may be devices such as those kpage 13,` Figure 22, and Brown Instrument Company Catalogue #8902, page 20. 'I'he output of controller 14 'is connected by means of air line 1I to-a conventional control-valve 53 such as, for l example, the pneumatic diaphragm control valve f type 57T as disclosed in Fischer Governor Com- '.pany Catalogue #35, page F.24. A portion of the reacted emuent free of promoter may'be withdrawn, if desired, through line 6l, controlled by valve 52, This is usually done, however, only inl cases where an excess of isoparaiin for the alkylation unitis produced in the isomerization unit. The reacted mixture is passed through line l1 by means of open valve 58 and may either be directly introduced with the reacted alkylate emuent, which. is substantiallyv acid-free, into iractionating tower 1 for separation of lisobutane 'fromthe normal butane and alkylate by means of line 89, open valve 10, lin'e S--and openvalve 6, valve 12 being closed, or valve 10 may be closed and the mixture-of iso and normal butanes may be passed by means of line 1I and open valve 12 into the feed line 2 and the emuent from the isomerizationunit 54 s thereby fed directly into the alkylation unit 4. Although no provision is made for the'same in the drawing, nevertheless caustic treaters, driers, pumps, reboilers, and the like are employed as required. Usually a caustic treat of normal butane-isobutane eiiiu'ent from the stripping column 51 is employed in order to neutralize any entrained aluminum chloride or hydrogen chloride contained therein. Any Cs paramns which have formed duringthe isomerization are removed from the system with the light alkylate as overhead from tower 04, without the necessity f including another fractionating tower in the isomerization section of the system.

That portion of the norlrial butane in line i8 which goes to the dehydrogenation unit is passed through line 8| by means of open valve 82 into the dehydrogenation unit 83 and the resulting mixture of olens and paramn content may be either selectively or non-selectively absorbed in sulfuric `acid ofv alkylating strength at 2.0-50" F. and at the proper acid to olefin ratio in absorber 89 by passing the effluent from line 8d into the absorber 89 by means of line 85 controlled by valve 86, or the absorber may be by-passed and the reacted eiiluen-t fed direct to an alkylation valve S9 fed into the alkylation unit so that inv effect a two-stage alkylation is carried out thereby. The normal butane-isobutane or unabsorbed portion of the eiiluent from the dehydrogenation unit 83 is passed by means of line Se controlled by valve 95 tothe isomerization unit 5t by means of line 4i,-etc., as previously described. Further quantities of normal butane may be added tothe eiiluent from the absorber 89 by-means of line 92vl controlled by valve 93, or if desired some or all of the unabsorbed eiiiuent from absorber 89' tion as hereinbefore set forth which may be made without departing from the spirit and scope o! the present invention, and the appended claims indicate-*only such limitations as should bel im- Whereesiredlto besecured by Letters Patent 'lo is:

- 1. A process for the production of high boiling normally liquid isoparamns which comprises alkylating a hydrocarbonmixture containing low boiling isoparailin, low boiling normal param-n,

15 low boiling monoolen, under alkylation reacand deviations, variations and the like, of the invener (to adequately define the invention.v

tion conditions in the presence of an alkylation catalyst to produce normally liquid isoparafllns. separating the unreacted normal parafn trom the alkylate produced, isomerizing sufdcient of said low boiling normal parafn to isoparain and returning the same to the alkylation unit so as to compensate for and replace the lsoparafn reacted in the alkylation reaction by subjecting the said normal paramn to isomerization in the presence ot an aluminum halide and a, halogencontaining promoter, the rate of throughput of the normal paraffin being correlated with the amount of isoparaflin required -for the alkylation reaction by measuring the vapor pressure of said low boiling normal paraffin at a `predetermined temperature, measuring the vapor pressure of the isomerized mixture substantially tree of catalyst and promoter at substantially the same predetermined temperature and directly controlling the throughput of the feed stock through the isomer-ization reaction zone by means of the vapor pressure differential between the two vapor pressure measurements and conducting the resulting isomerized mixture to the alkylation system.

2. A-process for the production of high boiling normally liquid isoparafns which comprises alkylating a hydrocarbon mixture containing low boiling isoparaflin, low boiling normal parailln, low boiling monooleiln, under alkylation reaction conditions in the presence of an alkylation catalyst to produce normally liquid isoparaiiins, separating the unreacted normal parafn from the alkylate produced, isomerizing sumcient of said low boiling normal paraln to isoparaflin and returning the same to the alkylation unit so as to compensate for and replace the isoparailin reacted in the alkylation reaction by subjecting the said normal parailin to isomerization in the presence of an aluminum halide and a halogen-containing promoter, the rate of throughput of the normal paraffin being correlated with the amount of isoparaflin required for the alkylation reaction by measuring the vapor pressure 'of said low boiling normal parain at a predetermined temperature, measuring the vapor pressure of the isomerized mixture substantially free of catalyst and Apromoter at substantially the same predetermined temperature and directly controlling the throughput of the feed stock through the isomerization reaction zone by means of the vapor pressure diierential between the two vapor pressure measurements, conducting the resultant mixture to the alkylation system, and wherein at least la portion of the normal paraiiln from the alkylation product is further diverted to a catalytic dehydrogenation unit operated under dehydrogenation conditions and in the presence of a dehydrogenation catalyst to obtain a product predominating in monoolefln and normal paraffin, introducing said product into the alkylation reaction zone at least in sufficient quantity to compensate for and balance the loss of oleiin therefrom because of condensation with isoparafiln. n

3. 'A process for the production of high boiling normally liquid isoparatllns which comprises alkylating a hydrocarbon mixture containing low boiling isoparamn, low boiling normal paraiiin, low boiling monoolefln, under alkylation reaction conditions inthe presence of an alkylation catalyst to produce normally liquid isoparaflins, separating the unreacted normal parainn from the alkylate produced, isomerizing suillcient of said low boilingnormal parafdn to isoparailln and re.

turning the same to the alkylation unit so as to compensate for and replace the isoparaiiln reacted in the alkylation reaction by. subjecting the said normal paraiiin to isomerization in the presence of an aluminum halide and a halogen-containing promoter, the rate of throughput of the normal parain being correlated with the amount of isoparaflin required for the alkylation reaction by measuring the vapor pressure of said low boiling normal paramn at a predetermined temperature. measuring the vapor pressure oflthe isomerized mixture substantially free of catalyst and promoter at substantiallythe same predetermined temperature and directly controlling the throughput of the feed stock through the isomerization reaction zone by means of the vapor pressure differential between the two vapor pressure` measurements, conducting the resultant mixture to the alkylation system, and wherein a portion of the normal paraflin from the alkylation product is so diverted'to a catalytic dehydrogenation unit operated under dehydrogenation conditions and in the presence of a dehydrogenation catalyst to give a product containing monoolen and isoparaiiin, absorbing the olefin content of the reacted effluent in sulfuric acid of alkylating strength and alkylating the resultant extract with isoparain, subjecting the unabsorbed portion of the reacted effluent from the dehydrogenation unit to a catalytic isomerization under isomerization reaction conditions and conducting' the resultant isomerized mixture substantially free of halogen-containing promoter and catalyst to the alkylation reaction.

4. In a process of isomerizing normal paraiiins of at least four carbon atoms per molecule under isomerization reaction conditions in the presence of an aluminum halide and halogen-containing promoter, the improvements comprising measuring the vapor pressure of the feed stock at a predetermined temperature, measuring the' vapor pressure of the isomerized mixture substantially free of aluminum halide and halogen-containing promoter at substantially the same predetermined temperature, directly controlling the throughput of the feed stoel; through the isomerization reaction zone by means of the vapor pressure diierential between the two vapor pressure measurements so as to regulate the amount of normal parain passing through the isomerization reaction zone and the amount of isoparailin produced therein.

5. In a combination alkylation-isomerization process involving the alkylation of a cracked reflnery C4 cut containing butenes and butanes, the amount of isobutane present being adjusted so that it is in molar excess of the butenes, and

wherein normalbutane is separated from the isobutane by distillation from the alkylated reaction mixture, isomerized to isobutane and reintro duced into the alkylation reaction zone, the improvements comprising regulating the amount and rate of normal butane isomerization to isobutane by measuring the vapor pressure of the feed stock to the isomerization unit at a predetermined temperature, measuring the vapor pressure-of the isomerized mixture substantially free of catalyst and promoter at substantially the same predetermined temperature, regulating the throughput of the feed stock through the isomerization reaction zone directly by means of. the vaporpressure differential .between the two vapor-pressure measurements and introducing.

the resultant mixture of isobutane and normal butane into the alkylation system.

6. lIn a process of normal parailln isomerization wherein the normal parailin contains at least four crbon atoms per molecule to produce isoparalns under isomerization reaction conditions in the presence of a Friedel-Crafts type catalyst and a halogen-containing promoter, the

-' improvement comprising regulating the rate andv amount of normal parailln fed through the isomerization unit and isomerized therein by measuring the vapor pressure of the feed stock at a predetermined temperature, measuring the vapor pressure oi' the isomerised substantially free of Friedel-Crafts type catalyst and halogencontaining promoter at substantially the same predetermined temperature and directly control-

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