US2460303A - Gasoline manufacture - Google Patents

Description

Patented Feb. I, 1949 GASOLINE MANUFACTURE Sumner H. MoAllister, Lafayette, and John Anderson and Walter H. Peterson,

Development Company, San

assignors to Shell Berkeley, Calif.,

Francisco, Calii'., a corporation of Delaware Application January 29, 1942, Serial No. 428,656 18 Claims. (Cl. 260-683.4)

This invention relates to the production'of motor fuel and deals particularly with anew and more eflicient method of increasing the yield of high anti-knock value hydrocarbons obtainable from petroleum products and the like.

Great advances have been made in the production of high octane gasoline within recent years, but large amounts of available hydrocarbons, particularly, gaseous hydrocarbons such as ethane, ethylene and propane, are still unused because no satisfactory method for eillciently converting them to saturated liquid hydrocarbonshas been available. It is an important object of the present invention to overcome this disadvantage of prior methods of gasoline manufacture. More particularly, it is an object of the invention to provide a method whereby hydrocarbons are treated in a series of cooperating steps to produce higher yields of isoparaflins boiling in the gasoline range than have been obtainable heretofore from the same starting materials. A-speciflc object is to provide an improved, continuous and cyclic process of polymerization and alkylation of high efficiency. Another special object is to make propane and ethylene available as starting materials for the production of branched chain octanes. Still other objects and advantages of the process of the invention will be apparent from the following description. v

Various proposals have been made for producing gasoline by procedures involving polymerization of oleflnes and alkylation of isoparafiins, but none of these methods have proved to be satisfactory because of the diiliculties of correlating the polymerization with the requirements of the alkylationstep. This is accomplished by the process of the present invention by the use of special polymerization conditions which insure high yields of high octane gasoline and long catalyst life in the alkylation step. The new process has the additional advantage that it makes more effective use of ethylene and propane than has heretofore been possible.

For the purpose of making the invention more clear, it will be described with particular reference to its application to the improvement of the commercially established method of alkylating isobutane with butylene's in the presence of concentrated sulfuric acid as the catalyst, in which propane is a component of the starting material. The accompanying drawing illustrates diagrammatically .an assemblage of apparatus particularly adapted to this application of the process. It will be understood, however, that the invention is not limited to this application and that not methods be employed, but also that the other" arrangements of apparatus and other operating at a plurality of points,

shown, if streams of different composition are only may other-feed stocks and other alkylating procedures may be used.

Referring to the drawing, a charge of isobutaneand propane-containing hydrocarbon from any suitable source, for example,'from the fractionation of natural gas or straight run'gasoline.

or residual paraflins from olefinic conversion processes, and hydrocarbons from the alkylation step of the invention, to be more fully described hereinafter, introduced via line 22, are fed, as by line i, to a depropanizer column 2. The hydrocarbon feed to this column may be introduced instead of the'single line being employed. In column 2 all hydrocarbons of less than four carbon atoms, usually mainly I and condenser 9, and by line H, to the alkylation system, represented propane, are taken off overhead via line 3 to condenser 4, preferably provided with anoutlet 4a through which lower boiling components such as ethane may be removed, and accumulator I, the higher boiling components are removed as bottom product by line isobutanizer column 8. In column 6 a separation of isobutane from normal butane is made, the latter being removed as bottoms via line I, for use in adjusting the and dehydrogenation step or for other purposes. Isobutane of high purity is taken oil via line I is fed from accumulator IO,

by l2.. In the alkylation step, preferably carried out by the method disclosed and claimed in U. S.

Patent 2,232,674, the isobutane is reacted'with olefines to form branched chain hydrocarbons of high anti-knock value, boiling in the gasoline range. Olefines from a suitable maybe supplied by line i3.v Such olefines may, for example, be a butane-butylene fraction of gases obtained in the stabilization 01 a cracked naphtha or the like and in such case will usually contain a small amount of propane." To the olefine or oleflnes admitted by line l3 are added comprising ex'cess isobutane, diluents introducedwith the olefine, including propane and normal to and conducted to devapor pressure of gasoline to butylenes which may be butane for example,

from any extraneous source 3 and alkylation products, are withdrawn by line ll to a de-butanlzer column ll. From column ll alkylation products are withdrawn by line II for further fractionation, if desired, into cuts having boiling ranges appropriate for the particular use to which the products are to be applied. The separated lower boiling components are removed by line II to condenser fl and accumulator 2i, whence they are conducted by line 22 to column 2, in which the propane content is removed as previously described.

The separated prop lator I is fed by lin e collected in accumuif desired introduced by line 24, to cracking unit II in which it is the object to produce as high conversions to unsaturates as possible. This may be advantageously achieved by non-catalytic cracking at atmospheric pressure and about 1200 Etc 14:00 F.,using a residence time of. about 1 to 2 seconds. Under these preferred conditions, ethylene and propylene are the main reaction products and the formation of parafllns, such as ethane, is minimized. Other conversion methods, either catalytic or non-catalytic, may, however, be employed. Thus, for example. methods such as are described in U. 8. Patents 2,168,840 and 2,217,865 may be used. As a rule, conditions of operation at which substantial amounts of ethylene are formed are preferred since highest conversions to unsaturates can be most economically obtained in this way. The conversion products, after suitable cooling or other desired treatment, not shown,are conducted by line 26 to separating unit 21, in which the components lower boiling than ethylene, mainly hydrogen and methane, are removed for use in supplying heat for the process or for other purposes. This separation may be eifected by fractionation or by absorption of the higher boiling components in a suitable liquid such, for example, as pentane, followed by stripping of the absorptionproduct. The remaining hydrocarbons, principally unreacted propane, ethylene and propylene, together with a small amount of higher hydrocarbons, mainly butylenes, are fed by line 20 to a fractionating column 20 in which the ethylene is removed as overhead byline 30 and fed to polymerization unit ll. Additional ethylene from any suitable source may be used in the polymerization, such ethylene being introduced by line It, if sufilciently free from undesirable lower or higher boiling components, or by lines 88 or 34 if removal of such components is considered advisable.

The object of the polymerization step of the process is to produce, in high yield, olefines which are-especially suitable for use in the alkylation step of the process, for exaple to convert ethylene as eompletely as possible to butylene. It is desirable to carry out the polymerization, whatever the olefine or olefines used as feed, so as to produce substantial amounts of normal olefines instead of branched chain polymers, since the former give improved results in the alkylation of isoparafiins. These objectives may be most ad- I, together with propane vantageously achieved by effecting the polymerication in the presence of catalysts consisting of the metals of the 8th group of the periodic table.

,Of particular use for this polymerization are cobalt and nickel, cobalt being the preferred catalyst. The metals employed as the polymerization-promoting catalysts are used in a reduced state and are preferably employed in the form of finely divided particles disposed on suitable cars',seo,sos

riers. The use of activated carbon as the carrier for the reduced metal, for example reduced cobalt, has been found to be of particular benefit for the conversion of ethylene to produce polymers containing high percentages of the desired butylenes, but other supports may be used. The use of the carriers for the'active catalyst metals is advantageous since it permits an accurate control of'the oleiines to be polymerized and the metal catalyst in the reaction zone, while maintaining other operating conditions, such as the reaction temperature, pressure, space velocity, contact time, etc., constant. The metal catalyst, e. g. reduced cobalt, whether employed alone or in the preferred form of a finely divided metal deposited on activated carbon, or the like, may be prepared and employed in a variety of ways. For example, it may be used in the form of compact masses, granules, chips, powder, etc. One method of preparing the catalyst for the polymerization according to the present invention includes the steps of absorbing aqueous cobaltous nitrate on activated carbon or the like, decomposing the nitrate to the corresponding oxide by a prolonged heating at'an elevated temperature, and finally reducing the oxide by heating, preferably while passing an inert or a reducing gas, for example hydrogen, through the catalyst mass. Other methods of preparing the reduced catalyst metal, as well as the incorporation thereof onto porous carriers, may be employed. The concentration of the active reduced metal catalyst may vary within relatively wide limits, depending on the specific metal employed, the desired contact time, and the like. When ethylene is polymerized according to the present invention and this primary material is conveyed through the reaction zone at the rate of about 250 grams per hour per liter of catalyst space, good conversions have been obtained when the cobalt-to-carbon ratio is in the neighborhood of 14:86. However, much higher or lower concentrations of the catalyst may also be used.

Instead of using a solid catalyst bed through which the reactants are conveyed, it is also possible to effect the polymerization according to the present invention by maintaining the catalyst, e. g. reduced cobalt, whether used alone or on a carrier, in suspension in the reaction zone. This may be effected, for instance. by suspending the catalyst in the liquid polymer and by conveying the olefine to be polymerized therethrough.

The catalyst employed for the polymerization of the unsaturated hydrocarbons may also contain various promoters which when used alone will not catalyze the reaction. As such, reference may be made to the oxides and/ or salts of lithium, thorium, copper, silver, zinc, and the like, as well as some of these metals per se, for example small amounts of silver or reduced copper with finely divided cobalt or the like.

Instead of polymerizing individual olefines separately, mixtures of olefines may be treated. Thus, for example, column 29 may be by-passed and the ethyleneand propylene-containing mixture conducted by line 35 to polymerizer ii, in which these oleflnes may be co-polymerized. It has been found that there are critical ranges of temperature and pressure which should be maintained in order to insure highest yields of products most desirable for use in alkylation. Thus, the polymerization of ethylene in the presence of reduced cobalt deposited on activated carbon is preferably carried out at temperatures of about 35 C. to 150 C., most preferably between C. and 0.. using pressures above about 300 lbs.

per sq. in., most preferably between 600 and 900 lbs. per sq. in. The same range of temperatures ried out the reaction products may be conducted by lines 86 and 31 to line H connecting with the alkylation unit. tageous, however, to use .higher throughput rates, for example about 200 to 500 grams of ethylene per liter of catalyst per hour, in polymerizer 3| as under such conditions not only may higher production rates 'be achieved but also products of better quality for alkylation may be obtained, particularly through a reduction in the amount of higher boiling products formed. Under such conditions it is preferred to return the polymerization products by lines 38 and 33 to column 29. The polymers will then appear in the bottoms removed by line 39 along with the unreacted propane. This mixture is fed by line 40 to fractionation column 4|, in which the propane is taken off overhead by line 42, and the polymers, mainly normal butylenes if ethylene has been polymerized alone or a mixture of mainly normal butylenes and amylenes if the ethylene has been co-polymerized with the propylene, are removed by line 43 and fed to the alkylation unit by line l4, or, particularly where the residence time in polymerizer 3| is insuflicient to eifect the desired degree of isomerization of the polymers formed, the olefine or olefines may be conducted by line 44 to an isomerization unit in which substantial conversion of the oleflnes to beta-olefines is effected before using them in the alkylation step. For this isomerization catalysts of the same type as used in the polymerization stepare particularly suitable. With these catalysts the isomerization is advantageously effected at about 60 C. to 120 C., and

production of higher boiling compounds is preferably avoided. Where the polymers are not deethanized they may be fed to the isomerization It is frequently more advan-' or the propylene recovered therefrom. fed'to the alkylation unit by line ii, or withdrawn byline 52 for isopropyl alcohol production or other use.

Particularly when feeding a sulfuric acid solu tion of propylene by line II to the alkylation unit, a part or all of the acid normally admitted by line Iia may be omitted. In certain cases the separation of propylene from the propane may be advantageously effected by an alkylation treatment using isobutane, for example, supplied through line 54. 'In this case the hydrocarbon products are conducted by lines II and II to line It, and the alkylate recovered with the products of alkylation from unit It. It may even be feasible to carry out the alkylation with the propylene in unit i2, where the amount of propane present is such that it does not too unit by lines 31 and 46. In either'case, products consisting substantially of oleflnes having the double bond between carbon atoms removed from the end of the chain are conducted by lines 41 and I4 to the alkylation unit ii, in which they give higher yields of high quality products and a materially longer catalyst life than when the previously employed olefine mixtures are used.

The propane-propylene mixture removed by line 42 or the similar mixture supplied by lines 39 and 48, when de-ethanization of the polymerization products is not essential, is conducted to a propylene separating unit 49. This separation may be carried out in a number of difierent ways. It may consist of an eflicient fractionation, after which propane is returned by lines and 23 to cracking unit 25, and propylene is conducted by line 5| to the alkylation unit, or by lines 5| and 52 to some other use. An extraction treatment, for example with sulfuric acid, may be used to efiect the separation, the solvent being admitted by line 53 and the extract itself,

greatly reduce the isoparaflln concentration in the reaction, and line 56 is provided for use in such operations.

It will be apparent from this description of the invention that ,itofiers many advantages over prior methods' of operation. Not only does it make it possible to eflicientiy utilize propane and ethylene in the process, but also it gives improved results in the allwlation as a consequence of the fact that normal olefines are used therein in place of branched chain products or polymerization. As. a result of isomerization of the olefines in unit 45, or, where long contact times are used in polymerization, in unit 3|, the process gives more uniform results because the oleflnes are more uniform and longer catalyst life in alkylation because the isomerized oleilnes are predominantly beta-oleflnes. These latter advantages may be extended by using in the process only isomerized olefines conveniently obtained, for example by supplying the olefines, preferably normal olefines, to the process by line 51 instead of line It.

Many variations may be made in the process, the various steps of which may be carried out batch-wise or intermittently instead of continuously. The process is not limited to alkylation with sulfuric acid as described as a preferred since corresponding hydrocarbons from other sources may be used instead. In fact, it maybe advantageous in some cases to use other hydrocarbons than those described in the illustrative example in the various steps of the process. Thus, isopentane may be alkylated instead oi. isobutane, and normal butane, for example, supplied to line 23 by lines 58 and 50 may be cracked instead of, as well as in addition to, the propane. Alternatively, the normal butane mayjbe catalytically dehydroganated in unit 25 instead of cracked and line Gil may be used to conduct-the resulting butylenes to the isomerization. "I'he alkylation with the products of polymerizer 3| and/or isomerizqr 45 may be carried out separately from the alkylation. with oleilnes from other sources. Column 29 may be operated so as to separate propylene along with the ethylene, higher boiling products being removed as bottoms and either withdrawn from the system by line 6| or treated along with, or similarly to, the hydrocarbons in line 39, as previously described.

preferably deethylenized in a separate column, not shown, the bottom product of which is fed to line 39. Propylene or other oleflne separated in unit 49 may be fed to polymerizer 3| by connecting lines 32 and 52, it being generally desirable when such oleflne is to be intcrpolymerized with ethylene to maintain an excess of the less reactive higher olefine, preferably 2 to mole of higher oleiine (such as propylene) per mol of ethylene during the polymerization. Still other variations may be made not only in the The polymerization products in this case are materials treated, but also in the details of opsuiting normal alpha olefines of four,-and five car- I bon atoms per molecule to the corresponding beta olefins and reacting the isomerized, olefins with an isoparaflln under alkylating conditions, and recovering high anti-knock value saturated liquid hydrocarbon reaction products.

2. A process of producing motor fuel components from normally gaseous hydrocarbons which comprises cracking propane to produce a mixture of ethylene, propylene and unreacted propane, separating the ethylene from the propylene and propane, converting the separated ethylene substantially to .a mixture of alpha and beta butylenes by contact with a metal of the eighth group of the periodic table at between C. and 150 C. substantially isomerizing the alpha butylene content of said mixture to beta butylene, and alkylating an isoparafiin with the resulting beta butylene.

3. A process of producing motor fuel components from normally gaseous hydrocarbons which comprises contacting ethylene with reduced 00- balt deposited on activated carbon at a temperature between 30 C. and-150 C. and, under a pressure above about 300 pounds per square inch. separating unreacted ethylene from the resulting butylene, contacting the latter with reduced cobait deposited on activated carbon at a temperature between C. and 120 C. to substantially convert the butylene to beta butylene, and alkylating isobutane with said beta butylene to produce high anti-knock value gasoline components.

4. A process of producing motor fuel components from normally gaseous hydrocarbons which comprises subjecting propane to treatment at an elevated temperature at which substantial conversion to ethylene takes place, separating the ethylene produced from components of the reaction mixture having less and more than two carbon atoms per molecule, contacting the separated ethylene with a polymerization catalyst to produce an alpha butylene-containing product, contacting said alpha butylene with reduced cobalt deposited on activated carbon at a temperature between 60 C. and 120 C. to substantially convert the alpha butylene to beta butylene, and

alkylating isobutane with said beta butylene to.

content of said mixture to beta butylene, alkylat-' ing. said separated isobutane with the resulting beta butylene in the presence of sulfuric acid of about to concentration, and recovering high anti-knock value gasoline components from the reaction products.

6. A process of producing motor fuel components from normally gaseous hydrocarbons which comprises reacting a butyleneand propane-containing hydrocarbon mixture with isobutane in the presence of an alkylation catalyst under conditi'ons at which alkylation of the isobutane takes place, fractionating the reaction products to separate normally gaseous hydrocarbons from the alkylation products, separating propane from said normally gaseous hydrocarbons, cracking said propane to produce a substantial yield of ethylene, polymerizing said ethylene by contact with reduced cobalt at a temperature between 30 C. and C. and under a pressure above about 300 pounds per square inch to produce an alpha butylene-containing product, isomerizing said alpha butylene to beta butylene, and feeding the resulting beta butylene to said alkylation reaction to produce saturated high anti-knock value gasoline components therefrom.

'7. In a process of producing motor fuel components by alkylating isobutane with butylene, the improvement which comprises fractionating a hydrocarbon mixture to separately remove therefromisobutane, normal butane and propane, reacting the separated isobutane with butylenecontaining hydrocarbon under alkylating conditions, separating aikylation products from normally gaseous components of the reacted hydrocarbons, returning the normally gaseous components to the flrstisaid fractionation, cracking propane separated from the isobutane therein, removing hydrocarbons having less than two,carbon atoms per molecule from the cracking products, separating ethylene produced in said cracking from unreacted propane present therewith, polymerizing the separated ethylene by contact with a metal of the group consisting of cobalt and nickel at between 30 C. and 150 C., returning the alpha butylene-containing polymerization products to said ethylene separation, fractionating the higher boiling products from the latter to separate unreacted propane from said alpha butylene, contactingthe alpha butylene with reduced cobalt on activated carbon under conditions at which beta butylene is produced therefrom, andfeedlng said beta butylene to said isobutane alkylation.

'8. A process for producing high octane number gasoline which comprises polymerizing an olefin having at least 3 carbon atoms per molecule, subjecting at least a part of the resulting polymers to catalytic isomerization, and alkylating isobutane by reaction with said isomerized polymer,

mer by reaction in the presence of sulfuric acid. SUMNER H, McALLISTER.

10. The process which comprises polymerizing JOHN ANDERSON. propylene, subjecting at least a portion of the WALTER H. PETERSON. resultant polymers to the action 01' an olefin isomerizing catalyst at isomerizing conditions, and 10 REFERENCES CITED alkylatins an alkylatable hydrocarbon with at The following references are of record in the least a portion of said isomerized propylene polyme f this patent: mer.

11. A process for producing branched chain UNITED STATES PA'I'ENTS hydrocarbons which comprises polymerizing pro- Number Name Date pylene, subjecting at least a portion of the re- 1,914, 74 Runge June 20, 1933 sultant polymers to the action of an olefin isomer- ,939,425 tt t 1 Jan 9, 3

' izing catalyst atisomerizing conditions, and al 3,130,37 st h t a1 21, 9 9 l ng n alkylatable r r on with at 2,227,559 Stevens et al. Jan. 7. 1941 least a portion of sa d some ized propylene poly- 20 2,268,557 Allender Jan. c, 1942 2,330,206 Dryer et a]. Sept. 28, 1943 12. The process which comprises polymerizing 2,375,687 Peterson a1 May 8, 1945 a normally gaseous olefin, subjecting at least a 3,333 942 Zimmerman 3 1945 portion of the resultant polymers to the action 3,404,340 Zimmerman July 16, 1946 0 an olefin isomerizing catalyst at isomerizing 25 conditions. and alkylating an alkylatable hydro- FOREIGN PA'IENTS carbon with at least a portion of said isomerized Number Country Date polymer.

9. A process for producing higher boiling a normally gaseous olefin, subjectingv at least a branched chain parafllns which comprises polyportion of the resultant polymers to the action merizing propylene, subjecting at least a part of 01' an olefin isomerizing catalyst at isomerizing the resulting polymers to catalytic isomerization, conditions, and alkylatlng a isoparaflln with at and alkylating isobutane with the isomerized poly- 5 least a portion of said isomerized polymer.

559,735 Germany Sept. 23, 1932 13. The processwhich comprises polymerizing g

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