US2418899A - Process for the synthesis of hydrocarbons - Google Patents

Description

E. F. PEVERE ET A, '2,418,899 PROCESS FOR THE SYNTHESIS OF HYD ROCARBONS Filed 0G12. 24,' 1945 pril l5, '1947.

Patented Apr. 15, 1947 POCESS FOB THE SYNTHESIS'OF HYDRCAI'LBONS` pany, New York, NY

..` a corporation of Delasppueauoocmser 24, 1945, serial No. 624,292

1 Our invention relates to the synthesis'of hydrocarbone, and especially to an improved'process for synthesizing hydrocarbons ofmotor fuel range by the hydrogenation of carbon oxides.

The present application isa continuation-inpart of our co-pending application, S. N. 461,852, led October 13, 1942, for Process for the synthesis of hydrocarbons.

The synthesis of hydrocarbons by the hydrogenation of carbon monoxide has been operated lar theory by which it may operate.

on a-commercial scale for a number of years, but

this process has had certain disadvantages, particularly in thev character of the hydrocarbons produced. The motor fuels obtained by this process have not been comparable in anti-knock properties to motor fuels obtainable from petroleum fractions, and have generally had octane numbers considerably vbelow straight run and thermally cracked gasolines. i

An object of the present invention is to provide a process for the hydrogenation of carbon oxides to produce motor fuel hydrocarbons of improved anti-knock characteristics.

Another object oi' our invention is to provide an improved reaction mixture for the vapor phase catalytic hydrogenation of carbon oxides to produce increased yields of hydrocarbons.

A further object of our invention is to provide a suitable continuous .cyclic process for eiecting our improved hydrogenation reaction.

Other objects and advantages of our invention will be apparent from the following description.

In accordance with the present invention, the reactant mixture for the hydrogenation contains, in addition to hydrogen and a carbon oxide, a substantial proportion of a hydrocarbon component comprising essentially branched chain hydrocarbons. The provision of a branched chain hydrocarbon in the reaction mixture-increases the yield of hydrocarbons of motor fuel range and above, and thus effects a marked improvement in the volumetric eiliciency of the catalytic unit. The use of a branched chain hydrocarbon in the reaction mixture also modies the characteristics of the reaction products, and effects a marked improvement in the anti-knock characteristics of the motor fuel range hydrocarbons. It is believed that the branched chain hydrocarbon reacts with methylene radicals at the catalyst surface to produce branched chain hydrocarbons of higher molecular weight, rather than essentially straight chain hydrocarbons, such as are produced from carbon monoxide and hydrogen alone. However, it is to be understood 9 claims. (c1. 26o-449.6)

that our invention is not limited to any Any branched chain hydrocarbon of lower molecular weight than the desired reaction product may be employed in our process, but we prefer to -use .a branched chain hydrocarbon which is in the vapor state under the hydrogenation conditions employed. Isobutane, isobutylene, isopentane. the methylbutenes andmethyipentenes, 2,2-dimethylbutane, and 2,3-dimethylbutane are examples of ,hydrocarbons of the preferred volatility range.

When effecting the reaction with a liquid phase in contact with the catalyst, higher boiling branched chain hydrocarbons auch as diisobutylene, tri-isobutylene, andthe corresponding par- 'aillns may be employed A mixture of such hydrocarbons inay be employed if desired, but the recycling of unreacted branched chain hydrocarbon'in thesubstantial absence of straight chain motor fuelf range.

hydrocarbons willbe simplifiedI if only a single branched chain hydrocarbon is 'used for this purpose. Although any branched chain hydrocarbon will, be ,operative in our process we prefer to use isoparafnns of 4 to 6 carbon atoms, and our invention will be. speciilcally illustrated with respect to the use of ,isobutana The amount of hydrocarbon to be incorporated in the reaction mixture may be varied over relatively wide limits, depending on the particular hydrocarbon employed, and the nature of the synthetic hydrocarbons to be produced. Alarser amount of hydrocarbons may be employed when the catalyst and reaction conditions are chosen for the production of a widel range product, including high molecular weight constituents, than is desirable when the synthesis conditions are designed to produce primarily light hydrocarbons of It is desirable to employ at least 5 mol per cent of isobutane, based on the carbon -oxide in the reaction mixture, -and correspondingamounts of other branched chain hydrocarbons. Amounts of 5 to 15 mol per cent are suitable for obtaining a substantially modified reaction product. However, a large excess of the branched chain hydrocarbon, e. g., -1000 mol per cent, may be employed to minimize the formation of the usual carbon oxide hydrogenatlon products.

carbon in the reaction mixture, the hydrogenation reaction may be eilected in accordance with prior practices in the art. Either carbon monoxide or carbon dioxide may be employed, using thev known ratios of hydrogen to carbon oxide in each case. However, carbon monoxide is usually to be a temperature lof 1200-1500# F. carbon monoxide-hydrogen preferred. and further discussion herein will refer speciilcally to carbon monoxide.

The usual catalysts. comprising metals of the eighth group of the periodic system, together with activating constituents, such as aluminum, magnesium, thorium, their oxides, and the like may be employed in our process. Any catalyst which is effective for the reaction and hydrogen alone. will be found to be operative 'with the reaction mixtures of the present invention.4 Such catalysts may beprepared, reduced, and conditioned in the usual manner, and may be used in the dry state for a fully vapor phase process. or may be used in the form of a slurry in a v'high boiling hydrocarbon or other liquid carrier.

The temperature and pressure conditions for the reaction may be the same as those employed with the particular catalyst for the reaction of carbon monoxide and hydrogen alone. Temperature of 325 to 550 F., and Apreferably 390 to 450 F., or in the range about 325 to 100 F., and pressures up-to 100 atmospheres but preferably from atmospheric to iifteen atmospheres. constitute -suitable conditions with most catalysts.

The contact time need not .be modied when incorporating a branched chain hydrocarbon in the reaction mixture, although improved yields of light motor fuel fractions maybe obtained in some cases by utilizing a somewhatshorter contact time than would be employed in-the absenceV of a hydrocarbon reactant. i

In order to operate the hydrogenation processes economically, it is desirablel to recycle the. un-

reacted carbon monoxide and hydrogen, and to utilize vthe methane .and other low molecular weight hydrocarbons which process. The fixed gases, condensable hydrocarbons.. 'may be separated usually preferable to. oxidize the hydrocarbon component to carbon monoxide prior to recycling.

For this purpose, the fixed gases-may be mixed withsteam or other onzen-containing gas, and passed over a suitable catalyst, such as nickel, at The resulting mixture. after cooling by suitable heat exchange, may then be recycled to the hydrogenation reaction, preferably' of carbon monoxide including the noli--4 4 f tion may be subjected to polymerization. alkylation, or other conventional reactions for the production of the higher boiling hydrocarbons. The. alkylation reaction isparticularly advantageous,

however. sincethe separated narrow boiling fraction contains both the isoparafiin and-the oleilns required for the alkylation reaction.

The use of isobutane as the branched chain hydrocarbon in the reaction mixture, and the.

*tionA of xed gases, oxidation of the hydrocarbon content of the xed gases by catalytic reaction with steam at high temperature, and recycle of are produced in the the resulting carbon monoxide-hydrogen mixture, are efected in accordance with conventional procedures. This representation, however, isonly diagrammatic, and additional expedientel lwhich are commonly employed, such as the use of f activated charcoal adsorbers to effect-,complete recoveryof products from the gas mixture, may alsobe used. In this phase of the process, the

only distinction of'our procedure overprior prac-, tices is the incorporation of 'isobutane in the reaction mixture. A

In order to recover isob,vv taie f romthe reaction product for recycle, the primaryjractionator is operated toseparate propane and propylene 'as overhead, and toob'tainas a side-outa light liquid hydrocarbon fraction containing the butanes and butylene's. The latter fraction is 'then'deI s' butanized, andlthe debutanizer overhead is iractionated tobbtain an isobutane-butene distilfrom-the reaction product and recycled, but it'is being mixed with the fresh make-up reactants prior to entering the reaction vessel. This pro-v4 cedure, and other -known expedients for cyclic operation of the hydrogenation process'. may be used in conjunction with our present improvements; and our invention is not limited to the use of any particular procedures or reactin conditions for effecting recycle of carbon monoxide. and hydrogen.

In order to utilize a branched chain hydrocarbon in the reaction most economically, it is also desirable .that the unreacted hydrocarbon be recycled in the process. For this purpose, the particular hydrocarbon employed may be separated from the light liquidhydrocarbon reaction product by conventional methods, such as multiple stage fractionation, azeotropic distillation, and' the like.

One advantageous method of separating an unreacted isoparain comprises the recovery -of a fraction containing only the isoparafn and the oleiins of substantially the same-boiling point, reacting the olen contentA of this fraction to produce. higher boiling hydrocarbons, separating the latter, and hydrogeriation reaction. In this type of operation, the olen content of the narrow boiling iraclate, which is employed in the alkylation step -of theprocess.

' The alkylation may be effected in accordance' with any of the usualmethods, utilizing catalystssuch as sulphuric acid, hydrouoric acid,

aluminum chloride, and the like. In the modi` cation illustrated, sulfuric acid is used as the catalyst, and the' reaction and separation of the reaction product are effected in the conventional, manner. The alkylate' debutanizer overhead supplies recycle.. isobutane for either the alkylation reaction,'the hydrogenationreaction, or both, as j may be desired. .The make-up isobutane for the process Amay likewise be supplied only to the 't alkylation step, or to .the hydrogenation step, or to both, as desired. Generally, we prefer to supply the .make-up isobutane to the hydrgenation step and utilize most or all 'of the recycle isobutane to supply the large excess desired in the alkylation reaction. The particular distribution of the makeup and recycle isobutane, however, will be determined in-any case by the relative amounts of .reactants'em'ployed in the hydrogenation and alkylation reactions-' It may be seen that the procedure described aboye has the advantage of improving the yield andquality of the motor fuel hydrocarbonsprduced in the hydrogenation reaction, and also yielding additional motor fuel hydrocarbons of high 'quality f romthegaseous olefins produced in the hydrogenation.

recycling the isoparailin to the The following specic example lillustrates the vuse of theprocedure described above:

aiample A hydrogenation catalyst comprising cobalt 011s" oxide with minor amounts of manganese, thorium, and magnesium oxides, supported on kieselguhr, and reduced with hydrogen at an increasing temperature from 650 to '770 F., is employed for the hydrogenation of carbon monoxide, with and without isobutane in the reaction mixture. The charge rates, essential reaction conditions, and the hydrocarbon yields which are obtained under these conditionsare shown in the table 2. The method according to claim 1 in which the isoparamn is isobutane.

3. The method according to claim 1 in which the isoparaiiin is isopentane.

4. In a catalytic process for synthesizing hydrocarbons by the hydrogenation of a carbon oxide, the method'which comprises continuously passing to a reaction zone a reactant feed combelow: prising carbon monoxide, hydrogen and iso- Char cu. ftJhr. per cu. it. Hydrocarbon ge of catalyst Tem- .Space vel yield lha/1,000 era. Pres ity cu. ft. of cu n of charge Iure sure' charge/hr' recoverable by Carbon Hydro- Isobuatm per etui of condensation and Monoxide gen tane ca a ys adsorption The C. F. R. M. octane number of the motor fuel fraction in the rst case above is only about 45, whereas the octane number of the motor fuel fraction in the second case may be as high as 65, or even higher. If the sulfuric acid alkylate from the isobutane-butene fraction of the hydrogenation product is blended with the motor fuel fraction, the octane number of the overall-motor fuel produced may be increased to 68, or higher.

It is to be understood, of course, that the above example is merely illustrative and does not limit the scope of our invention. Other branched chain hydrocarbons may be used in the reaction mixture, in place of isobutane, and the reaction conditions may be modified in various respects, as pointed out in the preceding discussion. Similarly, other equivalent procedures may be employed for recovering unreacted branched chain hydrocarbon for recycling to the hydrogenation reaction. In general, it may be said that the use of any equivalents or modifications of procedure which would naturally occur to those skilled in the art, is included in the scope of our invention. Only such limitations should be imposed on the scope of our invention as are indicated in the appended claims.

We claim:

1. In a catalytic process for synthesizing hydrocarbons by the hydrogenation of a carbon oxide, the method which comprises continuously passing to a reaction zone a reactant feed comprising carbon monoxide, hydrogen` and isoparafn hydrocarbon having from 4 to 6 carbon atoms per molecule, subjecting the reactant feed in the gas phase to contact with a hydrogenation catalyst comprising a metal of the eighth group of the periodic system, and a minor amount of a metal oxide having the essential promoting action of thorium and magnesium oxides, effecting contact between the reactants and the catalyst at a temperature in the range 325 to 550'F. and under a pressure ranging from atmospheric to about 15 atmospheres, continuously removing from the reaction zone 'a stream of reaction products comprising unreacted isoparaffin and synthesized hydrocarbons. separating unreacted isoparafiin from the reaction products, and recycling said separated isoparaiiin to the reaction zone, the amount of isoparain entering the reaction zone being at least 5 mol per cent based on the carbon oxide in the reaction mixture.

ing contact between the reactant and the catalyst at a temperature in the range 350 to 450 F. and under substantially atmospheric pressure, continuously removing from the reaction zone a stream of reaction products comprising unreacted isoparain and synthesized hydrocarbons,

separating unreacted isoparaiin from the reaction products, and recycling said separated isoparaiiin to the reaction zone, the amount of isoparafiin entering the reaction zone being about 5 t0 15 mol per cent based on the carbon oxide in the reaction mixture.

5. The method according to claim 4 in which the isoparafn is isobutane.

6. The method according to claim 4 in which the isoparailin is isopentane.

7. In a catalytic process for synthesizing hydrocarbons by the hydrogenation of a carbon oxide, the method which comprises continuously passing to a reaction zone a reactant feed comprising carbon monoxide, hydrogen and isoparaiiin hydrocarbon having from 4 to 6 carbon atoms per molecule, subjecting the reactant feed in the gas phase to contact with an active synthesis catalyst comprising a metal of the eighth group of the periodic system, effecting contact between the reactants and the catalyst at a temperature in the range about 325 to 700 F. and under a pressure ranging from atmospheric to about atmospheres, continuously removing from the reaction zone a stream of reaction products comprising unreacted isoparaifin and synthesized hydrocarbons, separating unreacted isoparaiiin from the reaction products. and recycling said separated isoparaihn to the reaction zone, the amount of isoparaflin entering the reaction zone being at least 5 mol per cent based on the carbon oxide in the reaction mixture.

8. The method according to claim 7 in which the isoparaiiin is isobutane.

9. The method according to claim '7 in which the isoparaln is isopentane.

ERNEST FRANK PEVERE. GEORGE BATES HATCH. EUGENE EDWARD SENSEL.

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