US2439021A - Preparation of saturated hydrocarbons - Google Patents

Description

April 6, 1948. H. T. QUIGG 2,439,021

PREPARATION 0F SATURATED HYDROCARBONS Filed July 24, 1945 ATTORNEYS Patented Apr. 6, 1948 PREPARATION F SATURATED HYDROCARBONS Harold T. Quiza', Bartlesville, 0kla.-, assignor to Phillips Petroleum Company, a corporation oi' Delaware Application July 24, 1945, serial No. soases This invention relates to the preparation of l paralns or saturated hydrocarbons from lowboiling normally gaseous oleiins, and especially from ethylene or ethylene and propylene, contained in normally gaseous streams such asthe eiluent from an ethane and/or propane cracking unit or the cracked gas formed as a by-product in cracking operations. Y More particularly it relates to the conversion of such low-boiling aliphatic olen's into higher-boiling parafiins in the motor and/or aviation fuel range of boiling point and molecular weight. Still more particularly, it relates to a process wherein the ethylene contained in cracked gas strea/ms is converted to valuable paraflinic hydrocarbons, especially branched chain octanes, suitable for use as a high knock rating blending component in the preparation of aviation and motor fuels.

The 'art of converting butylenes. by alkylation of isoparafiins especially isobutane, to high octane hydrocarbons is well known. It is also well known that the conventional alkylation catalysts such as hydrofluoric acid and sulfuric acid will not effect alkylation with ethylene. Special catalysts such as aluminum chloride are required to bring about alkylation of isoparaillns with ethylene. 'I'he alkylation of isobutane with ethylene by means of aluminum chloride-containing catalysts produces Cs hydrocarbons, especially diisopropyl. However, no economically feasible process is available whereby aliphatic oleiins boil- 11 claims. (el. zooi-683.4)

ing below butylenes, such` as propylene and more especially ethylene, can be reacted with isoparailins to give parains heavier than C1, such as the branched chain octanes, nonanes and higher parafflns. .Since tremendous quantities of ethylene and propylene are cheaply and readily available in dilute form in cracked gas streams, such a process is highly desirable.

The principal object of my invention is to make available to the art a process whereby low-boiling oleiins, especially propylene and more particularly ethylene, can be converted to heavier saturated hydrocarbons of motor and aviation fuel and heavier boiling range, predominantly Ca and heavier, in a simple and economical manner. Another object is toprovide a process of the -foregoing type which involves a minimum number of steps and gives a high yield of valuable products with a minimum of loss by undesirable side reactlons and the like. Another object is to provide an improved method of converting olefins contained in waste refinery gas streams into valuable products. Another object is to provide a process of the foregoing type which gives a high yield of high octane number Cs and heavier hydrocarbons from an oleiin-containing stream whichcontains relatively small amounts of propylene. process las in the foregoing objects which does not require an expensive preliminary concentration of ethylene or ethylene and propylene contained in the cracked gas stream used as starting material. Another object is to provide a process of the foregoing type which gives a more desirable product than is obtained from other processes using light olens, such as ethylene, as the raw material. Numerous other obiects will appear more fullyhereinafter.

The accompanying drawing portrays diagrammatically one arrangement of equipment which has been found suitable for carrying out the process of the present invention.

General In accordance with my invention, normally gaseous olefins contained in a normally gaseous mixture containing other normally gaseous components, especially hydrogen 'and parafiins including methane, are converted into heavier hydrocarbons in the motor and aviation fuel range of molecular weight and boiling point by three sequential steps which are integrated into a unitary process. The oleiins are iirst removed from the normally gaseous feed mixture by absorption in liquid isoparaihn as an absorption liquid. This dissolves the olefins while allowing the light nonolenic components, principally hydrogen and methane, to pass through undissolved. The liquid isoparailln rich is oleiin is withdrawn from the absorber and is passed to a catalytic polymerization zone wherein the olenn content is `polymerized catalytically with the isoparailin as a diluent. The ethylene is thereby converted to butylene and if any propylene is present, as is usually the case, ethylene and propylene are inter-polymerzed ur co-polymerized to give amylenes or pentenes. Ordinarily. the ethylene is present in such excess that the propylene is entirely consumed in this manner,` substantially no simple polymerization of propylene to hexylenes taking place. The isoparafnn and the polymer contained in the catalytic polymerization effluent are now fed to an alkylation zone where the lsoparaflin is alkylated with the DOlymers or higher-boiling oleflns formed in the polymerization step to give heavier saturated hydrocarbons having a highly branched structure and being in the motor and aviation fuel range of molecular Weight and boiling point. Generally, the al- Another obiect is to provide a kylate produced is mainly composed of C parafsired, is suitable as feed stock for the present tins and heavier. 'I'he alkylate formed can be invention.

readily separated intoa relatively light fraction, A typical gas obtained by cracking a 25% suitable for use as a high knock rating blending ethane-75% propane mixture at 6-8 p. s. i. g. and component of motor and aviation fuels, and a s at 1400' F. followed by extraction of C4 and any relatively heavy fraction known in the art as heavier hydrocarbons 'had the following analyheavy alkylate which is very suitable for use sis:

as a safety fuel, as solvent in paints, varnishes, v M01 per cent lacquers and other plastic and coating composi- Hydrogen 18 tions, in dry-cleaning, or in insecticides such as lo Met-haue Y 38 fly sprays, etc. mme v n Thusit will be seen that the isoparailin serves Ethylene 29 iirst as an absorption liquid to remove the ole- Propane 5 fins from the lighter iixed gases. hydrogen and Propylene 3 5 methane, then as a diluent in the polymerization step whereby undesirable side reactions are pre- Such a. stream is an excellent feed for the process vented in the polymerization zone, and then as of the present invention.

one of the reactants, namely, the hydrocarbon The other feed to the process of the present which is alkylated in the alkylation step. No invention is an isoparaiiln feed. Usually this'is a separation of olefins from the rich absorption go stream of isobutane since isobutane upon alkylmedium leaving the absorber is required before ation with the lowest polymer of ethylene, namely the polymerization step and the eiliuent from the butylene, or with the inter-polymer of ethylene polymerization step is a suitable feed to the alwland 'propylene, the polymers formed from the\ ation step requiring only the removal of unreoleiins contained in the preferred olefin stream, acted light gas. g3 gives isooctane and other highly branched oc- Feed stocks tanes, nonanes, etc., which are valuable motor and aviation fuel blending components and for As the olefin-containing gas stream fed to my other vpurposes wherever heavy alkylate" is deprocoss, I prefer to use any stream rich in ethylsired. However, the feed may comprise isopenene. The feed may or may not contain propylene. so tane or even isohexane. It may be a mixture of The gas may be from any source, for instance the isobutane and lsopentane. Use of such higher waste gas formed in the cracking of heavier norisoparafiins gives a greater yield of "heavy alkylmally liquid material such as gasoline, naphtha. ate. Normal paraiilns corresponding to the isokerosene, gas oil, fuel oil, crude oil, or the like. paramns may be present in the isoparamn feed. The cracking gas obtained from vapor phase a5 For example, the presence of substantial quancracking processes is especially rich in oleilns' tities of normal butane in the isobutane feed which often range up to 60 per cent. of the total stream is unobjectionable since such normal bugas and of which ethylene is predominant. The tane functions as an absorbing liquid in the first methane and hydrogen content may range from or absorption step and as an inert diluent reto 50 per cent of the cracking gas. The com- "40 ducing side reactions in the polymerization step position of cracking gases is discussed on pages and in the alkylation step. The pressure of ex- 114-116 of vol. 1 and pages 139-140 of vol. 2 of cessive amounts of normal paraiiin in the iso- Ellis, The VChemistry of Petroleum Derivatives." paraidnV feed maysbe undesirable because it is Ordinarily, such cracking gas is subjected in not feasible to eliminate the normal paramn known treatment for the removal of the valuable prior to the alkylation step and the presence of C4 and heavier components and frequently. evenl a large amount of normal paraffin may undethe C; components prior in its use as feed t sirably repress the desired alkylation reaction. the process ofthe present invention. Thefeedto Both feed stocks should be free of contamithe present invention may be derived from the nants orimpurities which would interfere with cracking of ethane or propane or mixtures of the polymerization or alkylation reactions or ethane and propane which, as is now well-known, which would be objectionable in the finished prod^ yields an ethylene-rich gaseous eiiluent which uct. In general, the feeds are essentially .free usually contains a substantial amount of propylfrom sulfur, nitrogen and'. oxygen compounds. ene as well as of material heavier than C: hydro- For example, the feed stocks should be free from carbons. such an emuent is commonly -treated u sulfur or sulfur compounds such ,as hydrogen to remove the C4 and heavier material and if sulilde, mercaptans, alkyl suliides, etc.sincethese desired the C; content thereof, although I often impurities are objectionable both in the catalytic prefer to use a feed from which the propylene conversions and in the product.

has not been removed.

Atypieeieraekmggasstreamobtamecmme. Mmmm am of gas on fono'm ms: t1 In the process of my inven- V l hmm on. the o con ed in the feed, which ole- Hydrogen Y e w iins usually consist oi' ethylene or of a mixtm'e Methane Y 33 7 of ethylene and propylene with the ethylene often Eme 333 in excess of the propylene, are absorbed in liq- Ethylene 3 0 uidisoparaflin,generallyisobutane,whilethexed me 175 gases, which usually consist of hydrogen and Propylene 5 7 methane pass through imdissolved. v Since the Bum Y 9 9 absorption is not selective for` olens as against 'Bum 3 7 n paraiiins, but is based merely on relative volamm Y v 9 3 tility of the several hydrocarbons present, ethane Y Y v and @ny propane presentv in the feed are dissolved such a stream after extraction of the C4 and along with yethylene and any propylene.v Howheavier components, which extraction may ever. the presence of these paraiiins. in later poralso remove a part or all of the C: componente if de-"I tions ofthe process is not objectionable; on the contrary. they serve as desirable inert diluent in addition to the isoparaiiln in the subsequent polymerization step. Generally, they are removed with other C: and lighter components between the polymerization step and the alkylation step.

The absorption step may be a, simple gas scrubbing operation conducted in the usual vertical column packed or provided with other means for effecting the desired intimacy of contact such as theusual bubble trays. the cold liquid isoparafdn such as isobutane being injected continuously at a point near the top of the tower and descending downwardly therein in countercurrent to the gaseous olefin-containing feed introduced adjacent the bottom, the undissolved hydrogen and methane continuously passing out overhead and the rich absorbing liquid being continuously withdrawn from the bottom of the column. With such an arrangement the absorber pressure and the temperature and rate of introduction of isoparafnn are so adjusted as to eil'ect solution of substantially all the oleflns with minimum loss of valuable hydrocarbons (Cz and heavier including isoparaln absorbent) in the overhead 0r residue gas. Where isobutane is used as the isoparailln, the pressure in the absorption zone may range from 700 to 800 pounds per square inch gauge, the overhead temperature may be below 40 F., for example, 30 F. or therebelow, and the rate of introduction of liquid isobutane into the top of the absorber may be such as to give a mole ratio of isobutane fed in to olefin in the feed ranging from 2:1 upwardly say to 50:1, a range of from 2:1 to 10:1 being preferred.

I prefer to provide means for at least partially condensing the overhead from the absorber and returning liquid condensate to the top of the co1- umn as liquid reux therefor in addition to the reflux effect provided by the fresh isoparailin injected thereinto. By condensation of overhead vapors the loss of isoparailln in the outgoing residue gas is cut to a minimum. The condensation should be sulcient tok liquefy substantially all vaporized isoparafiln; for example, where the isoparailln is isobutane the condensation is so carried out as to liquefy substantially all the isobutane from the overhead gases. If it is found suitable or deisrable, the condensation may extend down to the C3 hydrocarbons and in extreme cases even down to the Cz hydrocarbons but the expense of refrigeration requirements to condense the Czs is prohibitive at the present time and the condensation of the Cas is often not commercially feasible under present-day conditions. The condensation ofl the condensible hydrocarbons from the overhead gases may be carried out in any suitable way as by providing indirect cooling coils in the top of the absorber, or by cooling the overhead in a separate cooler, passing to a condensate or reflux accumulator from which the uncondensed gases are vented in the usual way, and withdrawing the liquid condensate and injecting it into the top of the absorber.

In many cases I Prefer to operate the absorber as an extractive distillation column. i. e., to combine rectification and absorption by providing means for rebolling the kettle product prior to its withdrawal and means for partially condensing the absorber overhead as just described. The principles underlying extractive distillation are now well understood by those skilled in the art and need not be detailed herein. When extractive distillation is employed for separating the oleflns from the methane and hydrogen in practicing my invention, the olefin-containing feed is inpolymer produced is in the Ce-Cs range.

example, where the olefin consists substantially of ethylene, it is preferred that the polymerizal 6 troduced into the middle ofthe absorber column rather than into Aits bottom as in the case where simple gas scrubbing is practiced. In extractive distillation the bottom temperature wil1 be the boiling point of the kettle product at the column operating pressure.

Polymerization step The isoparamn containing dissolved olefin withdrawn from the absorber as bottom or kettle product is next passed to a unit wherein the olens -are polymerized to higher-boiling olens. 'I'he isoparaiiln functions as anv inert diluent and to repress undesired side reactions during the polymerization, and also to enable liquid phase conditions to be maintained therein without excessive pressures and even though the polymerization temperature be above the critical temperature of the ethylene or-of the ethylene and propylene.

It is preferred to conduct the polymerization under such conditions that substantially the sole reaction is one of simple polymerization of the olefin. It is also preferred that conditions be so adjusted that a major portion of the olefin For tion convert it principally to butylene and where the olefin consists essentially of ethylene and propylene that principally butylene and amylene be formed. Since the propylene is usually present in minor amount, conversion thereof to amylene by co-polymerization, mixed polymerization or inter-polymerization with the ethylene which is present in excess, is relatively easily accomplished. Where propylene is in excess of ethylene the excess may be converted to the dimer.

Polymerization primarily to olefin in the Ci-Cs range is preferred in order that upon alkylation of the isoparaflin with the polymer the'alkylate will not be unduly heavy but instead will be primarily in the gasoline range. To this end, polymerizationconditionsV are so adjusted as to effect principally dimerization and simple co-condensation of ethylene with propylene. If production of heavy alkylate as the principal or sole product is desired, thenl polymerization of the olefin to higher olens than Cs may be effected. However, ordinarily the extreme upper limit of polymer range will be decylene since alkylation of the usual isoparaflin with olefin polymer above decylene gives aikylate having more than 14 carbon atoms per molecule for which there is little demand.

The polymerization is conducted catalytically. The selection of suitable catalysts and suitable reaction conditions such as pressure, temperature, contact time, ratio of hydrocarbon to catalyst. and other factors will be obviousto those skilled in the art in the light of this disclosure. In general, the polymerization of ethylene requires somewhat more .active catalyst or more drastic reaction `conditions than the polymerization of its homologs. I prefer to effect polymerization of the ethylene by means of a more active catalyst which effects the desired conversion under conditions such that, with the isoparailin present in amount required to effect the absorption, a minimum of side reactions takes place in the polymerization zone. A catalyst which I have found to be exceptional is that of activated nickel oxide supported on a suitable carrier as disclosed more fully in the copendingV applications of G. C. Bailey et al., Ser. No. 435,888,

assenti.

filed March 23, 1942 (now U. S.Patent 2,381,198

granted Alllllt 7, 1945), and Sel'. No. 599,536,

filed June 15. 1945. I'he patent applications men- 1 thereof are hereby incorporated by reference. A

preferred lcarrier is that disclosed in the secondmentioned application, namely. silica gel either by itself or preferably promoted with a small amount of alumina as by impregnating the still wetI or only partially dried freshly precipitated silica gel with an aqueous solution of a suitable aluminum salt' such as aluminum sulfate or nitrate. Use of supported nickel oxide catalysts of the types disclosed in the above mentioned applications is especially advantageous in the practice of -this step of my invention because such catalysts smoothly effect simple polymerization of ethylene which very frequently is the sole or the principal olefin present in the feed. v

The polymerization temperature may vary within a rather wide range but will generally not be much lower than about C. nor substantially above about 225 C. It is preferred to polymerize with the range of about 50 to 150 C. Atmospheric temperature, about 24 C., is often used. Temperatures of at least about 100 C. ranging up to 200 C. may be superior since at such levels polymerization is accelerated without undue side reactions. Above a polymerization temperature of about 200 C. hydrocarbons other than oleiln polymers begin to be formed. The polymerization is ordinarily conducted at temperatures not over 150 C. It is carried out in the absence of hydrogen or other reducing agent.

High pressures favor the polymerization reaction, but under suitable conditions the reaction may be carried out under a very wide range of pressures, from as low as atmospheric or below to as high as 2000 p. s. i. or above. Although high pressures increase the'rate of polymerization they also increase the average molecular weight of the polymer formed. Accordingly, it is ordinarily preferred to conduct the polymerization at temperatures of not over 200 p. s. i.

The polymerization may be carried out in either liquid or gas phase. Ordinarily liquid phase operation is preferred. Accordingly, the presence of the isoparaflln in the feed to the polymerization step is additionally advantageous since it enables liquid phase conditions to be maintained much more readily and at desirably moderate pressures. Pressures such as to insure substantial or complete liquid phase operation are preferred. Liquid phase operation facilitates control of reaction temperature and contributes to catalyst life by diminishing the deposition of high molecular weight, or other non-volatile or insoluble, materials on the. catalyst surface. When polymerizing at temperatures above the critical temperature of the olefin, the presence of the inert isoparaiiln, which was used as an absorbing liquid and is subsequently used as the alkyiated hydrocarbon, facilitates the maintenance of liquid phase conditions. When polymerizing at temperatures below the critical of the olefin, the isoparailln performs its functions of minimizing side reactions and serving as an inert diluent.

In the relatively rare situation where poly- 'merization is vcarried out with the hydrocarbons in the gas phase, conditions should be such that the exothermic heat of reaction does not cause ve local overheating of the catalyst or a general rise in temperature above the desired op- 8 erating range. This can be .accomplished by suitable design -of a catalyst chamber to allow good heat transfer, and by controlling the rate of introduction of charge stock.

The contact time in the polymerization zone may vary over a wide range. A time as low as 30 seconds at atmospheric pressure and in the preferred temperature range is sufcient to polymerize the olens appreciably. However, higher extents of conversion are possible when a longer contact time and/or higher pressure are utilized. Contact times of 3 and even 12 hours may be employed but are ordinarily too long to be commercially feasible. Contact times suillcient to polymerize at least 75% of the olefin are preferred in order to minimize recycle or auxiliary polymerization.

Since the preferred nickel oxide catalysts are readily deactivated or poisoned by 'various materials such as sulfur compounds, carbon monoxide. some halogen compounds, organic oxygencontaining compounds, and the like, it is desirable, in order to secure satisfactory catalyst life,

vto exclude such materials from the polymerization system. This is preferably done by excluding them from the feeds to the absorbing step. Any suitable means for removing such materials from the feed may be employed.

Where the polymerization catalyst is a solid material it may be arranged in the form of a bed through which the polymerization feed is passed, usually downwardly. Alternatively, the catalyst maybe suspended in the hydrocarbon liquid or vapors in the manner in which so-called fluid catalytic conversions are effected. Known means for regenerating the catalyst is provided regardless of. the form which the catalyst takes.

Instead of a nickel oxide catalyst, I may use any other catalyst which is capable of effecting the polymerization of ethylene. Such other catalysts may be either known now or discovered in the future. The reaction conditions discussed in detail above apply particularly to the preferred activated nickel oxide catalyst. With other catalysts different polymerization conditions may be desirable. As an example of another type of catalyst, I may use boron fluoride and a nickel promoter as disclosed in VOtto et al. 1,989,425. Another catalyst is aluminum chloride.

The eilluent from the polymerization step may be subjected to fractionation or other means of separation to remove all material lighter than C4 leaving a fraction containing C4 and heavier including isoparailln and butylene and all other polymeric material formed in the polymerization step. If desired it may be further fractionated to separate material heavier than a predetermined level of molecular weightv or boiling point. For example, if the polymerization produces a small amount of heavy oily or waxy polymers it is often desirable to remove these and thereby prevent them from entering the alkylation step where they would give undestrably heavy alkylate. The unpolymerized olefin separated from the polymerization eluent may be passed to an auxiliary polymerization unit and there polymerized catalytically, the resulting polymer being merged with the polymer from'the main polymerization unit for passage to the alkylation step. If desired. isoparailln may be admixed with the olefin feed to the auxiliary polymerization unit whereby the above-detailed advantages of its presence in the main polymerization unit are attained. If desired the olefin-containing stream separated from the main polymerization eluent aesaosi may be recycled to the absorption step or directly to the main polymerization step.

l Aller/lation step line boiling range up through heavy alkylate" ordinarily having not more than fourteen carbon 4atoms per molecule.-

The alkylation step is conducted in a manner known per se. It is almost invariably carried out.

catalytically. It is ordinarily preferable to employ an inorganic acid such as substantially anhydrous hydrouoric acid. or concentrated sulfuric acid as the alkylation catalyst although any other suitable alkylation catalyst known now or discovered in the future may be employed, since the alkylation step does not per se constitute my invention. Many other alkylation catalysts are known such as aluminum chloride, aluminum chloride complexes, boron fluoride, etc.

The alkylation step is conducted in a manner well within the present skill o! the art and conditions for this step need not be described in detail. Sumce it to say that the alkylation ls conducted in such a way, that the oleilns alkylate the isoparaflln to give the desired product.

The alkylation enluent is treated in known manner as by fractionation, etc. to recover recyclev and product streams. Usually a phase of catalyst is recovered for recycle to the alkylation unit, a portion being passed to a regeneration or re-run unit. Likewise a phase oi.' unreacted isobutane is recovered i'or recycle to the absorption unit.

Many advantages are attained by the present invention. The principal advantage is that cheap olefins especially ethylene in readily available cracked gas streams are converted to very valuable alkylate in a simple and economical manner. Other advantages are that a single material, namely, the isoparafiln, performs a number ot valuable functions in a simple and peculiarly advantageous manner, namely, as liquid absorbent in the iirst step, as diluent and liquetying medium in the polymeri ation step and as major reactant in the alkylatio stage. Another advantage is that a large excess of isoparaiiin to olen 'is maintainedin the absorption step and is therefore maintained in the polymerization and alkylation steps whereby very undesirable side reactions are prevented. This large excess of isoparamn is particularly advantageous in the alkylation step since it prevents oleiln polymerization and improves the alkylate quality. Many other advantages of my invention will be apparent to those skilled ln the art.

Referring now to the accompanying drawing,

L the olefin-containing gas stream is charged to an absorber 2 through line I. 'I'he absorber is operated under such conditions (for instance, F. overhead and '760 p. s. i.) that most of the C2 and heavier hydrocarbons are absorbed in the liquid isobutane supplied at the top of the absorber 2, while lighter hydrocarbons such as hydrogen and methane are removed as gases. Isobutane which will be used in the reaction later is used as the absorption medium and as the reilux for the absorber 2 being added through line l in' a mole ratio 012:1 to 50:1 of olefin with a ratio ci 2:1 to 10:1 preferred. Abmrber 2 may 10 be provided with a reboiler 2A as shown to effect fractionation, thus serving to enect extractive distillation. It desired, the overhead may be cooled or dephlegmated to condenseCz and heavier, or C: and heavier, or Ci and heavier which is ted to the top of absorber 2 as reilux. Usually it will be desirable to condense and return only the Ci (and any heavier) contained in the absorber overhead, to avoid excessive refrigeration requirements. The provision for reuxing the tower is indicated diagrammatically on the drawing by the showing of an indirect reflux cooler 2B, although it will be obvious that any other suitable means for eil'ecting the desired result may be employed. The fixed gases such asl hydrogen and methane are removed at I and disposed of in any desired manner. '-I'he isobutane and absorbed gases are removed through line l and charged to polymerization reactor or reactors i. I'he reactors 6 may be operated in any desired sequence; two or three reactors 8 may be operated in parallel or series while the other one or 'two chambers are being regenerated with an oxygen-bearing gas. Ethylene can be converted t0 predominantly butylenes, and if propylene is present copolymerization to amylenes may also be eiiected by the use ot any suitable catalyst. A preferred catalyst is one of activated nickel oxide on a suitable carrier such as is described in the above-mentioned copending applications of G. C. Bailey et. al., Ser. No. 435,888, filed-March 2 3, 1942 (now Pat. No. 2.381.198), and Ser. No. 599,536, nled June 15, 1945.

'Ihe emuent from the polymerization reactor is withdrawn through line 'I and charged to a sep arator l' which conveniently takes the form of a 'conventional fractional distillation column and which is operated under such conditions that C: and lighterhydrocarbons are removed through line I. The disposal of this material will be gov-- erned by the amount of olefin present and the value or the olefin. 4If the olefin content of the gas is low it may be removed through line 25 and disposed of in any manner. It the oleiln content of the gas is high a portion of the gas may be returned to the feed to the absorber 2 through line 2l and the remainder vented through line 25 or all of thev gas may be charged to an auxiliary polymerization unit 21 similar to 0 but adjusted as to size. The eilluent from the polymerization unit 21 is withdrawn through line 28 and charged to a separator or fractionation column 29 from which polymer is removed through line 3l and mixed with the eiiiuent from the separator 8 in line II. Residue gas from separator 29 is removed through line 20. The isobutane and oleilns are withdrawn through line II and charged to an alkylation unit I3. Any type alkylation unit may be used such as an HF or sulfuric acid unit operated underconditions known to the art. The eiiluent. from the alkylation unit I2 is charged to a separation unit I5 through line I4. Separation unit II may comprise a series of iractlonal distillation columns to effect the indicated separations. Catalyst carried out with the hydrocarbon may be reclaimed and returned to the reactor I3 through line I6. Excess isobutane is removed through line I1 and may be combined with fresh isobutane through line 22 and returned to the absorber 2, the separator 8 or the alkylation reactor I3. Any n-butane present may be removed through line I2 and disposed of through line II or charged to an isomerization system through line 22 to be added to the recycle isobutane from line l1. Light hydrocarbons in the motor fuel and/or aviation fuel boiling range are withdrawn from the separation unit I through line 21 and heavy hydrocarbons boiling above the motor fuel boiling range are withdrawn through line 2l.

Example A hydrocarbon stream containing mostly ethylene and methane together with smaller amounts of hydrogen, ethane, propylene. and propane, is counter-currently contacted at 30 F. and 'Z50 p. s. i. with isobutane in an absorption tower. A gaseous mixture containing mainly hydrogen and methane is withdrawn at the top of the tower. and a liquid mixture of isobutane and ethylene containing minor proportions of ethane, propylene and propane is withdrawn from the bottom. The mol ratio of isobutane to ethylene in the latter mixture is approximately 8: l.

The isobutane-ethylene mixture is then passed through a catalyst chamber lled with a polymerization catalyst having the composition 1.5 per cent nickel oxide, 90 per cent silica gel, and 8.5 per cent alumina. Conditions for this treatment are; temperature, 120 F.; pressure, suiiicient to maintain liquid phase; space velocity, 2 liquid volumes per volume of catalyst per hour. Approximately '10 per cent of the ethylene is polymerized, and of this amount approximately 80 per cent is converted'to butylenes. The polymerization eiiluent is passed to a fractionation column from which ethane, unconverted ethylene, propylene, and propane are removed as an overhead fraction and recycled to the absorption tower.

The kettle product from the fractionator is passed to an alkylation reactor provided with a motor-driven stirrer and is intimately contacted with an equal volume of anhydrous hydrofiuoric acid. The alkylation conditions are: temperature, 100 F.; pressure, sumcient to maintain the reactants in the liquid phase; contact time, 10 min.; mol ratio of isobutane to olefin, at least 16:1: acidity of the acid phase, 90 per cent. The eflluent from the alkylation reactor is passed to a settler in which it separates into an acid phase, which is recycled to the alkyiation reactor, and a hydrocarbon phase. Dissolved hydrofluoric acid is removed, as a minimum-boiling azeotropic mixture with isobutane. from the latter phase by distillation. Organically combined iluorine is removed by contacting the acid-free hydrocarbon phase with calcined bauxite at about 180 F. The substantially iluorine-free hydrocarbon phase is then passed through a series of fractionators from which the following fractions are obtained: a

fraction, comprising chiefly isobutane, which is recycled to the absorption tower; a fraction, ccmprising hydrocarbons in the motor fuel boiling range, chiey octanes. which is withdrawn as the main product of the process; and a fraction, comprising hydrocarbons that boil above the motor fuel range, which is withdrawn from the system.

I claim:

l. A process of converting normally gaseous olefin comprising mainly ethylene contained in a gaseous mixture containing other normally gaseous components into heavier hydrocarbons having molecular weight and boiling point in the motor and aviation fuel range which comprises absorbing said olefin comprising mainly ethylene from said normally gaseous mixture in liquid isoparaitln in an absorption zone while allowing other tion zone, said isoparafiin serving as a diluent and enabling maintenance of liquid phase in said polymerization step, withdrawing the resulting mixture oi said isoparai'lin and said higher-boiling olefin and feeding it to an alkylation zone. and there alkylating said isoparailln with said higherboiling olefin to give heavier hydrocarbons having molecular weight and boiling point in the motor and aviation fuel range.

2. The process of claim 1 wherein the polymerization eiiluent is withdrawn from the polymerization zone and is subjected to separation into a C3 and lighter fraction and a fraction of said isoparamn and higher-boiling olefin which is employed as the' feed to said alkylation step.

3. The process of claim 1 wherein said liquid isoparailin is supplied to the top of said absorption zone in an amount such as to give a mole ratio to oleiin in the gaseous mixture fed to said absorption zone of at least 2:1.

4. The process of claim 1 wherein the bottom of said absorption zone is reboiled, the feed thereto is supplied at an intermediate point therein, said liquid isoparamn is supplied to the top thereof in an amount such as to give a mole ratio to olefin in the feed of at least 2:1, the overhead gases are cooled to effect condensation ofl at least the major portion of the C4 content thereof and the resulting condensate is fed to the top of the absorption zone as redux therefor.

5. The process of claim l wherein said polymerlzation is eiected with a solid catalyst comprising nickel oxide supported on a carrier and activated by heating in an oxygen-containing atmosphere at a temperature of between 400 and '100 C.

6. The process of claim l wherein said olefin consists essentially of a major proportion of ethylene and a minor proportion of propylene and is converted substantially to butylene and amylene in said polymerization step.

7. A process of converting ethylene contained in a normally gaseous mixture containing other normally gaseous components into branched chain octane which comprises absorbing said ethylene from said normally gaseous mixture in liquid isobutane in an absorption zone while allowing other normally gaseous components to pass through undissolved, withdrawing the resulting solution of ethylene in liquid isobutane from the absorption zone and feeding it directly to a polymerization zone, effecting catalytic liquid phase polymerization of said ethylene to butylene as the principal reaction in said polymerization zone, said isobutane serving as a diluent and enabling maintenance of liquid phase in said polymerization step, withdrawing the re.

sulting mixture of said isobutane and polymer including butylene from said polymerization zone and feeding it to an alkylation zone, and there alkylating said isobutane with said butylene with an inorganic acid catalyst selected from the group consisting of substantially anhydrous hydrofiuoric acid and concentrated sulfuric acid to give branched chain octanes.

8. A process of converting ethylene contained in a normally gaseous mixture containing methane and hydrogen into branched chain octanes which comprises absorbing said ethylene from said normally gaseous mixture in liquid isobutane in an absorptionzone while allowing other normally gaseous components including the methane and hydrogen to pass through undissolved, withdrawing the resulting solution of ethylene in liquid isobutane from the absorption zone and feeding it directly to a polymerization zone, effecting catalytic liquid phase polymerization of said ethylene to butylene as the principal reaction in said polymerization zone, said isobutane serving as a diluent and enabling maintenance of liquid phase in said polymerization step. withdrawing the resulting4 mixture of isobutane and butylene from said polymerization zone and feeding it to an alkylation zone, and there alkylating said isobutane with said butylene with an inorganic acid catalyst selected from the group consisting of substantially anhydrous hydroiluoric acid and concentrated sulfuric acid to give branched chain octanes.

9. The process of claim 8 wherein said polymerization is eiected with a solid catalyst comprising nickel oxide supported on a carrier and activated by heating in an oxygen-containing atmosphere at a temperature of between 400 and '700 C.

10. A process of converting ethylene and propylene contained lin a normally gaseous mixture containing methane and hydrogen into alkylate in the motor and aviation fuel range of molecular weight and boiling point which comprises absorbing said ethylene and propyleneA from said normally gaseous mixture in liquid isobutane' in an absorption zone while allowing other normally gaseous components including the methane and hydrogen' to pass through undissolved, withdrawing the resulting solution of ethylene and propylene in liquid isobutane from the absorption zone and feeding it directly to a polymerization zone, effecting catalytic liquid' phase polymerization of ethylene and propylene predominantly to butylene and amylene -by simple and inter-polymerization as the principal reaction in said polymerization zone, said isobutane' serving as a diluent and enabling maintenance of liquid phase in said polymerization step, withdrawing the resulting polymerization eiiluent. separating Cs and lighter components from a mixtureof isobutane and the polymer formed in said polymerization step and feeding said mixture oi' isobutane and polymer to an alkylation zone, and there alkylating said isobutane with said polymer with an inorganic acid catalyst selected from the group consisting of substantially anhydrous hydroiiuoric acid and vconcentrated sulfuric acid to give heavier hydrocarbon in themtor and aviation fuel range of molecular weight and boiling point.

11. The process for the preparation of an `alkylate comprising principally branched chain oc- 14 tanes from ethylene. contained in cracked gas containing same in dilute form in admixture with hydrogen and methane together also with some ethane and a small amount of propylene relative to the ethylene. said gas being free from C4 and heavier components, which comprises absorbing the ethylene and propylene from said gas by intimately countercurrently contacting said gas in a vertical scrubbing zone with liquid isobutane in an amount such as to give a mol ratio of lsobutane to ethylene plus propylene in said gas of from 2:1 to 10:1 at a top temperature below 40 F. and a pressure of from 100 to 800 pounds per square inch gauge and thereby effecting solution oi' substantially all of said ethylene and propylene in said gas in said isobutane while causing the hydrogen and4 methane to pass through undissolved, passing the resulting liquid isobutane containing dissolved ethylene and proof propylene with ethylene to amylene as the; 3

principal reactions, eifecting said polymerization at a temperature of from 24 to 150 C. with a solid catalyst consisting of nickel oxide supported on a carrier and activated by heating in an oxygen-containing atmosphere at a temperature of from 400 to 700 C., the isobutane serving as a diluent and enabling the maintenance oi' liquid phase in the polymerization step, fractionally distilling the polymerization effluent -to separate same into a fraction oi.' the material lighter than Cr hydrocarbons and a fraction containing the isobutane and the butylene and the small amount of amylene formed in said polymerization step, passing said last-named fraction to an alkylation step and there alkylating said isobutane with said butylene and amylene with an alkylation catalyst composed oi' an inorganic acid which is incapable oi' effecting .alkylation of isobutane with ethylene, thereby forming alkylate compris ing principally branched chain octanes, and recovering said alkylate comprising branched chain octanes from the alkyiation eiiiuent as the product of the process.

HAROLD T. QUIGG.

REFERENCES CITED The following references are of record in the ille oi' this patent:

UNITED STATES PATENTS

Images