CA1289126C - Cobalt catalysts for conversion of methanol or synthesis gas - Google Patents

Abstract

ABSTRACT OF THE DISCLOSURE

IMPROVED COBALT CATALYSTS, AND USE THEREOF
FOR THE CONVERSION OF METHANOL TO HYDROCARBONS, AND FOR THE FISCHER-TROPSCH SYNTHESIS

A zirconium, hafnium, cerium or uranium promoted cobalt catalyst and process for the conversion of methanol or synthesis gas to hydrocarbons. Methanol is contacted, preferably with added hydrogen, over said catalyst, or synthesis gas is contacted over said catalyst to proudce, at reaction conditions, an admixture of C10+ linear paraffins and olefins. These hydrocarbons can be further refined to high quality middle distillate fuels, and other valuable products such as mogas, diesel fuel, and jet fuel, particu-larly premium middle distillate fuels of carbon number ranging to about C20.

Description

2~ 6 RACKGROUND OF THE INVENTION
. ~
I. Field of the Invention This lnventlon relates to lmprovementa in a pro-cess for the converslon o~ methanol to hydrocarbons, to improvements ln a Flacher-Tropsc~l process for the production of hydrocarbon~, and to improvements made ln catalysts employed to conduct such processe~s. In partLcular, it relates to improved cobalt catalysts, and proCess for uslng such catalyats in the converslon of methanol, and Fiacher-Tropsch synthesis to produce hydrocarbons, eapsclally C
diatillate ruela, and other valuable produots.
II. Back~round A need exlsts for the creation, development, and improvement of catalysts and processes, uqe~ul ror the con-version of methanol and synthesis gaaes to hydrocarbona, eapeclally high quality tranqportatlon fuels. Methane is avallable in large quantlties, either as an undesirable by-product or off-gas from process units, or from oll and gas field~. The exi tence of large methane, natural gas reserves coupled with the need to produce premiu~ grade transportation Yuela, particularly middle distillate fuels, thus poses a ~ajor incentive for the eevelopment of new gas-to-liquids procesae3. However, whereas technology i9 avail-able for the conversion of nat~ral gaa to methanol, in order to utlllze this technology there is a need for new or improvcd catalysts, and processes suitable for the conver-sion of methanol to high quality transportation fuel~, particularly middle distillate fuela.
The technology needed to convert natural g~s, or methane, to synthesis 8as is also well e~tat~li3hed. It ls also known that synthesis gas can be converted to hydro-carbona via Fischer-Tropsch synthesi~, though new or improved catalysta, and processes for carrylng out Fischer-Tropsch reactions are much needed. Fischer-Tropsch ". , synthesls ~or the production Or hydrocarbon~ rrom carbon monoxlde and hydrogen l~ weil known in the technical and patent llterature. Commercial units have also bee~
operated, or are belng operated in ~ome parts Or the world. The rirst commercial Fi3cher-Tropsch operation utlllzed a cobalt catalyst, thou~h later more actlve iron catalysts were also commercialized. An l~portant advance ln Flscher-Tropsch catalysta occurred with the use of nic~el-thoria on Kieselguhr in the early thirties. Thl9 catalyst was followed within a year by the! correspondin6 cobalt catalyst, 100 Co:18 ThO2:lO0 Kle~elguhr, parts by weight, and over the next few year~ by catalysts constltuted to lO0 cO la ThO2:200 ~leselguhr and 100 Co:5 ~hO2:8 M80:200 Kie~elguhr, respectively. The ~roup VIII non-noble metals, i.e., lron, cobalt, and nlckel, have been-wldely used ln Fischer-Tropsch reactions, and these metalR have been pro-moted with various other metals, and supported in various ways on various substrate~. Most commercial experLence has been based on cobalt and lron cataly3ts. The cobalt cata-ly9t9, howe~er, are Or generally low activlty necessitating a muItiple 3taged proces3, as well as low ynthesls gas throughput. The lron catalysts, on the other hand, are not really suitable for natural gas conversion due to the high degree o~ water gas shift activity possessed by iron cata-lyst3. Thus, more of the synthesis sas is converted to carbon dioxide in accordance with the equation: H2 + 2C0 (CH2)X + C02; with too iittle Or the synthesis ~as being converted to hydrocarbons and water a~ in the more desiraole reaction, represented by the equation: 2H2 ~ C0 ~ (CH2)x ~2 The need for a catalyst compositlon, and process useful ~or the converslon Or methanol or synthesi~ 3as at high conversion levels, and at high yields to premium grade transportation fuels, particularly without the production of excessive amounts of ca-bon dioxide, were met in large part by the novel cataly3t composltion~, and proce~se3 described in U.S. Patent Nos. 4,542,122; 4,595,703; and 4,556,752. The 1;~ 1 39~26 -prererred catalysts therein descrlbed are characterized as particulate catalyst composltions con3tituted Or a titania or titania-conealning support, preferably a tltania support having a rutlle:anata3e content of at least about 2:3, upon which there 19 dispersed a catalytically active amount of cobalt, or cobalt and thoria. These cataly3t compo~itions po~se~s good activity and stabilLty and can be employed over long periods to produce hydrocarbons from methanol, or to syntheslze hydrocarbon~ from carbon monoxide and hydrogen.
These cobalt-titanla catalysts lt was found, like most hydrocarbon synthesLq catalysts, became coated during an "on-oil" run with a carbonaceous residue, l.e., coke, formed either during extended periods Or operation or durlng feed or temperature up~ets. The initially high activity of che cataly3ts declines during the operatLon due to the coke deposits thereon, and the operating temperature must be increased to maintain an acceptable level Or conversion.
Eventually the catalysts become deactivated to a point where the temperature required to maintain an acceptable conver-lon level causes excessive formation of methane and other light hydrocarbon ga3es at the e~pense Or the desired C10 hydrocarbons, at which point it ~ecomes neces~ary to regenerate, and reactivate the catalyst. Unli~e many other catalysts commonly used by the re~ining industry however, when the coke deposits were t~urned from tne cobalt-titania catalysts at oxidizing conditions by contact with air (or oxygen) at elevated tempe aturet, and tne catalysts there-a~ter trea~ed with hydrogen to reduce the cobalt metal component, the initially high activity of the cobalt-t.tania cataly~ts did not return to that of a rresh catalyst.
Rather, thelr activity wa3 considerably les~ than that of fresh cobalt-titania catalysts. Moreover, after the regeneration, and reactivation of the catalyst~, there was no improvement in the rate Or deactivation and the deactiva-tlon proceeded rrom a lower initial activity. This loss in ~2~39126 the overall activity brought about by burnlng the coke from these catalysts at elevated temperatures in the presence of air (oxygen) is not only detrimental per se, but severely restricts the overall life of the catalyst, and threatens their full utilization in commercial operations.
III. Objects It is, accordingly, a primary objective of the present invention to obviate this problem.
In particular, it is an object to provide novel and improved cobalt-titania catalysts, and processes utilizing such catalysts, for the conversion of methanol or synthesis gas to high quality transportation fuels, especially distillate fuels characterized generally as admixtures of C10+ linear paraffins and olefins.
A more specific object is ~o provide new and im-proved supported cobalt-titania catalysts, which in methanol conversion and Fischer-Tropsch synthesis reactions are not only highly active and stable prior to regeneration, and reactivation, but capable after regeneration, and reactiva-tion, of recovering their initial high activity, while main-taining their stability.
A further object is to provide a process which utilizes such catalysts for the preparation of hydrocarbons, notably high quality middle distillate fuels characterized generally as admixtures of linear paraffi.ns and olefins, from methanol, or from a feed mixture of carbon monoxide and hydrogen via the use of which catalysts.
IV. The Invention These objects and others are achieved in accor-dance with the present invention which, in general, embodies:
(A) A particulate catalyst composition consti-tuted of titania, or a titania-containing support, on which there is dispersed a catalytically active amount of cobalt sufficient to provide good activity and stability in the production of hydrocarbons from methanol, or in the produc-tion of hydrocarbons via carbon monoxide-hydrogen synthesis L2~i reactlons, and sufficient of a metal promoter selected from the group consisting of zirconium, hafnium Li.e., Group VIs metals of the Periodic Table of the Elements (E. H. Sargent & Co., Copyright 1962, Dyna-Slide Co.) having an atomic weight greater -than 90] cerium (a lanthanium series metal), and uranium (an actinium series metal), or admixture of these metals with each other or with other metals, such that after oxidizing the cobalt at elevated temperature, as occurs after the deposition of coke thereon during an operating run, the catalyst can be regenerated by burning the coke therefrom by contact at elevated temperature with oxygen or an oxygen-containing gas (e.g., air), and then reactivated by contact of the catalyst with a reducing gas, particularly hydrogen, to reduce the cobalt metal component such that the activity and stability of the catalyst is thereby restored. Suitably, in terms of absolute concentra-tions the cobalt is present in amounts ranging from about 2 percent to about 25 percent, preferably from about 5 percent to about 15 percent, calculated as metallic metal based on the total weight of the catalyst composition (dry basis).
The zirconium, hafnium, cerium, or uranium in the form of a salt or compound of said promoter metal, is added to the cobalt-titania ca-talyst, in amount sufficient to form a catalyst composite the activity and stabllity of which after regeneration, and reactivation, approximates that of a fresh cobalt-titania catalyst, i.e., a catalyst, cobalt-titania catalyst which has never been regenerated. The promoter metal is quite effective in low concentrations, concentra-tions greater than that required to provide the desired regenerability generally offering little, or no further benefit. The efficiency of the promoter metals is believed generally related to their highly dispersed physical state over the surface of the titania support. Suitably, a cobalt-titania catalyst can be made regenerable by composit-ing therewith a zirconium, hafnium, cerium, or uranium metal in weight ratio of metal:cobalt greater than about 0.010:1, preferably from about 0.025:1 to about 0.10:1. One of more ~g~6 Or aald promoter metala--vlz.. zirconium, hafnium, cerium, or uranium--ls dlspersed with the catalytlcally actlve amount Or cob~lt upon a titania support, partlcularly a titania support wherein the rutile:anataqe wel~ht ratio is at least about 2:3. The rutile:anataae ratlo is determined in accordance with ASTM D 3720-78: Standard Teat Method for Ratio Or Anataae to Rutile in Titanlum Dioxide Pi~menta 3y Use Or X-Ray Dirrraction. The absolute concentratlon of the cobalt and promoter metal is preaelected to provide the desired ratio of the zirconium, hafnium, cerium, or uranium metal:cobalt. Zirconium i~ a prererred Group IVB metal in term~ of ita cost-efrectivene~s, and a cobalt-titania catalyst to which zirconium i9 added in wei~ht ratio of zirconla:cobalt greater than 0.010:1, prererably ~rom about 0.04:1 to about 0.25:1 has been found to form a catalyst which is highly regeneration atable. This catalyst haa been found capable of continued sequences of regeneratlon with esaentially complete recovery Or its lnitial activity when the catalyst is returned to an on-oil operation, and there ia no loas in ~tability in elther methanol conversion or hydrocarbon syntheais reactions. ~he cobalt-titanla cata-lyst compositions when stabilized with any one, or admixture of zirconlum, hafnium, cerium, or uranium, it has been found, prcduce a product which is predorninately C10~ linea-paraffins and olerins, with very l~ttle oxygenates. These promoted catalyst species provide essentially the same hign selectivity, high activlty, ar.d high activity maintenance arter regeneration in methano1 conversion, or in the conver-aion o~ the carbon monoxide and hydrogen to distillate fuels, as ~reshly prepared unpromoted cobalt-titania cata-lyata (i.e., catalysta otherw.~e similar except that no zirconium, hafnium, cerium or uranium have been compoaited therewith) which have never ~een regenerated, or subjected to regeneration conditions. The promoted cobalt-titania catalysta are thus highly regeneration ~table, the activity and stability of the promoted catalyst being reatored a~ter regeneration to t~at of an unpromoted cobalt-titania ~2~ 6 catalyst which has never been regenerated by burning off the coke at hi8h temperature in air under oxidizing condLt1Ons.
(B) A process wherein the partlculate zirconium, harnium, cerium, or uranium promoted cobalt-tltanla catalyst compo~ition of (A), supra, ls formed lnto a bed, and the bed Or catalyst contacted at reaction condltionq wlth a methanol feed, or feed comprlsed of an ad~ixture Or carbon monoxide and hydrogen, or compound decompo~able ln situ within the bed to generate carbon monoxide and hydrogen, to produce a middle distillate fuel product constituted predominately of linear pararfins and olefins, particul~rly Cl0+ linear parafrins and olefins.
(i) In conducting the methanol reactlon the partial pre~sure Or methanol within the reaction mixture i~ generally malntained above about 100 pounds per square lnch at~olute (psia), and pref-erably above about 200 psia. It is often prefer-able to add hydrogen with the methanol. Suitably, methanol and hydrogen are employed in molar ratio Or CH3OH:H2 a~ove about 4:1, and preferably a~ove 8:1, to increase the concentration of Cl01 hydro-carbons in the product. Suitably, the CH30~:H2 molar ratio, where hydrogen is employed, ranges from at~out 4:1 to a~out 60:1, and prefera~l~ t~e methanol and hydrogen are employed in molar ratLo ranging from about 9:1 to a~out 30:l. Inlet h~drogen partial pressures prefera~ly range oelow about 80 p31a, and more preferably below about 40 ps a; inlet hydrogen partial pressures preferabiy ranging from about 5 psia to about 80 psia, and more prererably from about l0 psia to about 40 psla. In general, the reaction Ls carrled out at llquid hourly ~pace velocities ranging from about 0.l hr l to about l0 hr 1, preferat~ly from about 0.2 hr l to about 2 hr l, and a~ temperatures ranging from about 150C to about 350C, prefera-bly from about 180C to about 250C. Methanol ~2~126 ..

partial pressures preferably ran~e from about 100 psla to about 1000 psia, more preferably from about 200 psia to about`700 pRia.
(li) The synthe~i~ reaction Ls generally carried out at an H2:C0 mole ratio of greater than about 0.5, and preferably the H2:C0 mole ratlo ranses ~rom about 0.1 to about 10, more preferably from about 0.5 to about 4, at gas hourly ~pace veloci-ties rangin8 from about 100 ~/Hr/V to about 5000 V/Hr/V, preferat~ly from about 300 V/Hr/~ to about 1500 V/Hr/V, at temperatureg ranging from about 160C to about 290C, preferably from about 190C
to about 260C, and pressures above about 80 p9ig, prefera~ly ranging from about 80 pslg to about 600 psLg, more preferably from about 140 p~ig to about 400 p9ig.
~he product of either the methanol conversion reactlon, or synthesis reaction generally and preferably contaln3 45 per-cent or greater, more preferably 60 percent or greater, C10+
llquld hydrocarbons which boll above 160C (320F).
In forming the catalyst, titania is used as a support, or in combinatlon with other materlals for form~n~
a support. The titania used for the support in eitner meehanol or syn~as conversions, however, is prefera~ly one where the rutile:anatase ratio is at laast abGut 2:3 as determined by x-ray diffraction ~AaT.~ D 3720-7~). ?refer-ably, the tltania used for the catalyst support of catalysts usad ln ~yngas conversion is one wherein the rutile:anata~e ratio i9 at least about 3:2. Sui~ably the titania used for ~yngas conversions is one containin~ a rutile:anatase ratio of form about 3:2 to about 100:1, or higher, preferably from about 4:1 to about 100:1, or higher. A preferred, and more selectlve catalyst for use in methanol conversion reactions is one containing titania wherein the rutile:anatase ranges from about 2:3 to about 3:2. The surface area of such forms of titanla are less than about 50 m2/g. This weight of rutile provldes generally optimum act.vity, and C10 hydro-carbon selectivity without signlrlcant gas and C02 make.

31%6 The zirconium, hafnium, cerium, or uranium promoted cobalt-titania catalyst prior to regeneration, it was found, will have essentially the same high activity as the corresponding unpromoted cobalt-titania catalyst. Thus, during an initial, on-oil operating run, or run wherein hydrocarbons are being produced over the fresh catalyst by methanol conversion or hydrocarbon synthesis from carbon monoxide and hydrogen the activity of the two different catalysts is not essentially different. Unlike an unpro-moted cobalt-titania catalyst, or catalyst otherwise similar except that it does not contain zirconium, hafnium, cerium, or uranium, however, the initial high activity of the pro-moted cobalt-titania catalyst will be maintained even after regeneration of the coked catalyst which is accomplished by burning off the coke deposits at elevated temperature in an oxygen-containing gas (e.g., air), and the catalyst then reduced, as by contact of the catalyst with hydrogen, or a hydrogen-containing gas. Moreover, the stability of the promoted cobalt-catalyst will be maintained, this catalyst deactivating in an on-oil run at corresponding conditions at no greater rate than that of any unpromoted cobalt-titania catalyst, or catalyst otherwise similar except that it does not contain zirconium, hafnium, cerium, or uranium, which has never been regenerated. Whereas the unpromoted, fresh cobalt-titania catalyst was thus found to possess an initial high activity in an on-oil operation, it was subsequently found that the activity of this catalyst was not completely restored after regeneration, the catalyst recovering only about 50 percent of the activity formerly possessed by the fresh catalyst. Moreover, after initiation of an on-oil operation, the activity of the regenerated zirconium, hafnium, cerium, or uranium promoted cobalt-titania will decline at about the same rate as that of the fresh unpro-moted cobalt-titania catalyst. Retention of this activity and stability by the promoted cobalt-titania catalysts thus effectively ellminates the disadvantages formerly associated with unpromoted cobalt-titania catalysts, and makes possible . ~ .

121~91~6 full utilization of cobalt~titania catalysts in commercial operations.
Cobalt-titania catalysts, like most hydrocarbon synthesis catalysts are primarily deactivated during on-oil operation by the deposition thereon of a carbonaceous residue, i.e., coke, formed either during extended periods of operation or during feed or temperature upsets. It was thought that the coked catalyst could be regenerated and its initial activity restored by burning the coke from the cata-lyst. Air burns at, e.g., 400-500C, are thus normally effec-tive in removing essentially all of the carbon from a catalyst, this offering a relatively simple, commercially feasible technique for regenera-ting deactivated cobalt-titania catalysts. However, in order for air regeneration to restore activity, the catalytic cobalt metal must be maintained in dispersed state at both on-oil and regenera-tion conditions. Albeit the unpromoted cobalt catalyst upon which the cobalt was well dispersed was found to be stable during an on-oil operation, the cobalt agglomerated during high temperature air treatment. It is found however, that even in low concentration, zirconium, hafnium, cerium, or uranium, or admixture thereof, could be used as an additive to stabilize the cobalt-titania catalyst not only by main-taining the cobalt in a dispersed state upon the titania during on-oil operations, but also during air burns, thus providing a readily regenerable catalyst.
Whereas Applicants do not wish to be bound by any specific mechanistic theory, it is believed that the action of the zirconium, hafnium, cerium, or uranium metals in promoting the regenerability of a cobalt-titania catalyst during an air burn can be explained, at least in part.
Thus, during an air burn the crystallites of metallic cobalt of a cobalt-titania catalyst are oxidized to form Co3O4 which agglomerates at temperatures above about 350C. After reactivation of the catalyst by contact with hydrogen cobalt metal agglomerates are formed which are of larger crystal-lite size than the original metallic crystallites of cobalt , .
.

~.2~
metal. Large a$glomerates of cobalt form cataly3ts which are la~s actlve than catalyst3 formed with more flnely di3-persed cobalt. The zlrconium, hafnium, cerlum, or uranium promoter metals of the promoted cobalt-titanla catalyst are present a3 highly di3per~ed oxides over the TiO2 support surface, and all are Or a cublc crystal 3tructure (except for Ce which can exist either a3 cut~ic CeO2, or hexagonal Ce203). These oxldes ars believed to form a 3trong 3urface interaction wlth Co304 which i9 also of cubic crystal structure. The cubic oxide promoters are thus belleved to form a matrix, or act as a "glue" between the Co304 and TiO2, and maintain the cobalt in finely dlaper3ed form upon the support ~urface.
The cataly3ts Or thl3 invention may be prepared t~y techniques known in the art for the preparation of other catalysts. The catalyst can, e.g., be prepared by ~ella-tion, or co3ellation techniques. Sultably, however, the cobalt, zirconium, hafnium, cerium, or uranium metal3, or admlxtures of the3e metals with each other, or with other metals, can be deposited on a previously pilled, pelleted, beaded, extruded, or sieved ~upport materlal by the impreg-nation method. In preparing cataly~t~, the metal3 are deposited from solution on the support in preselected amount3 ~o provide the desired absolute amounts, and wei~ht ratio of the respective metal3, e.g., cobalt and zirconium or hafnium, or cobalt and an admi~ture of zirconiu~ and hafnlum. Suitably, the cobalt ana zirconium, hafnium, cerium, or uranium metals are composited with the support ~y contacting the 3upport with a solutlon Or a cobalt-contain-ing compcund, or salt, e.g., cobalt nitrate, acetate, acetylacetonate, napthenate, carbonyl, or the li~e, and a promoter metal-containing compound, or salt. One metal can be compoaited with the support, and then the other. For example, the promoter matal can first be impregnated upon the support, foliowed by impre nacion of the cobalt, or vice versa. Optionally, the promoter metal and cobalt can be colmpregnated upon the 3upport. The cobalt and promoter 9~26 metal compounds used in the impregnatlon can be any organo-metalllc or inorganic compounds which wlLl decompose to give cobalt, and zLrconlum, ha~nlum, cerium, or uranium oxides upon calcination, e.g., a cobalt, zirconium, or hafnium nitrate, acetate, acetylacetonate, naphthenate. carbonyl, or the like. The amount of lmpregnation solution used should be su~iclent to completely immerae the carri~r, usually within the range rrom about 1 to 20 times Or the carrier ~y volume, depending on the metal, or metals, concentration in the impregnation solution. The impregnation treatment can be carried out under a wide range o~ conditlons including ambient or ele~ated temperatures. Metal components other than cobalt and a promoter metal, or metal~" can al~o be added. The introduction Or an additional metal, or metal~, into the catalyst can ~e carried out by any method and at any time of the catalyst preparation, for example, prior to, rollowing, or simultaneously with the impregnation of the support with the cobalt and zirconium, haflium, cerium, or uranium metal components. In the usual operation, the addltional component is introduced simu1taneously with the incorporation o~ the cobalt and the zirconlum, and hafnium, cerium, or uranium components.
It is preferred to first impregnate the zirconium, hafnium, cerium, or uranium metal, or metals onto the support, or ~o coimpregnate the zirconium, hafnium, cerium, or uranium metal, or metal with the cobalt into the titania support, and then to dry and c~lcine the catalyst. Thus, in one technique for preparing a catalyst a titania, or tltania-containing support, is first impregnated with the zirconium, hafnium, cerium, or uranium metal salt, or com-pound, and then dried~or calcined at conYentional condi-tion~. Cobalt is then dispersed on the precalcined support on which the zirconium~ hafnium, cerium, or uranium metal, or meta10" has been di~per~,ed and the catalyo,t asain dried, and calcined. Or, the zirconium, hafnium, cerium, or uranium metal, or metals, may be coLmpregnated onto the ~upport, and the catalyst then dried, and calcined. The l26 zlrconium, harnium, cerlum and uranlum metals are believed to exlqt ln the rlnished freshly calclned catalyst as an oxlde, ~he metal oxLde~ being more closely assoclated with the tltania ~upport than wlth the cobalt.
The promoted cobalt-tltanla cataly~t, after lmpregnation of the support, i9 drLed by heatlng at a temperature above about 30C, prererably between 30C and 125C, in the presence of n1trogen or oxygen, or both, or alr, in a ga3 stream or under vacuum. It i9 neceasary to activate the finished catalyst prlor to uqe. Preferably, ths catalyst ls contacted in a firat step wlth oxygen, air, or other oxygen-containing 8as a~; temperature surricient to oxldlze the cobalt, and convert the cobalt to Co304.
Temperatures ranging above about l50C, and preferably above about 200C, are satisfactory to convert the cobalt to the oxide, but temperatures up to about 500C, such a~ might be used in the regeneratlon Or a severely deactivated catalyst, can be tolerated. Suitably, the oxidatlon Or the cobalt is achleved at temperatures ranging from about 150C to about 300C. The cobalt oxLde contained on the catalyst i~ then reduced to cobalt metal to actiYate the catalyst. Reductlon iq performed by contact Or the catalyst, whether or not prevlou ly oxldized, with a reducing gas, suitably with hydrogen or a hydrogen-containing ga~ strsam at temperatur=3 above about 250C; preferably above about 30GC. Suitably, the catalyst i3 reduced at temperatures ranging from about 250C to a~out 500C, and preferably from about 300C to about 450C, ~or periods rangin; from about 0.5 to about 24 hours at pressures ranging from ambient to about 40 atmo-~phere~. Hydrogen, or a gas containing hydrogen and inert components in admixture i~ sa~isfactory for use in carryin~
out the reduction.
In tre regeneration ~tep, the coke is burned from the cataly~t. The catalyst can be contacted w1th a dilute oxygen-containing gas and the coke burned from the catalyst at controlled temperature below the sintering temperature of the catalyst. The temperature of the burn i~ maintained at ~2~ 6 the de.~lred level by controlllng the oxy~en concentratlon and Inlet Bas temperature, thl~ ta~lng lnto conslderation the amount of eoke to be removed and the time de3ired to complete the burn. Generally, the eataly~t is treated with a ga~ havlng an oxygen partlal pressure above about O.l pound~ per ~quare ineh (psl), and preferably ln the range of from about 0.3 p91 to about 2.0 psl, to prov$de a tempera-ture ranglng from about 300C to about 550C, at statle or dynamle eondltion~, preferably the latter, for a time su~rleient to remove the coke deposits. Coke burn-ofr can be aeeomplished by rir~t lntrodueing only enough oxygen to Inltlate the burn whlle malntalnlng a temperature on the low slde Or thls range, and gradually lnereaslng the temperature as the flame front i9 advanced by addltlonal oxygen inJee-tlon untll the temperature has reaehed optimum. Most Or the eo~e ean generally be removed in this ~ay. The eatalyst is then reaetivated by treatment wlth hydrogen or hydrogen-con-tainlng gas as with a rresh catalyst.
The invention will be more fully understood by reference to the accompanying drawings and to the following demonstratio~s and examples which present comparative data illustrating its more salient features. AlI parts are given in te~ms of weight except as otherwise specified. Feed compositions are expressed as molar ratios of the compoments.
In the accompanying drawings, Figures 1 and 2 are graphical depictions of test results upon various catalysts according to the invention.
The addition of a small amount of hafnium, zireonium, eerium, or uranium, respec~.veIy, to a Co-TiO2 eataly~t maintains the eobalt in a high state of dispersien and stabillzes the catalyst during nigh temperature air treatments. The added zireonium, hafnium, eerium, or uranlum metal thus maintains during and after regeneratior.
the ~ery high intrinsle activitY of the eataly t which .s eharaeterlstie of a fresh eatalyst having well-dispersed eobalt on the TiO~. The high intrinsic activity of c..e promoted Co-riO2 permits, after regener~tlon, the same ~ h converslon cperations at iow tem?er~ture, where exeellent seleetivity ls obtained in the conversion of methanol o^
syngas to ClO~ hydrocarbons as with a fresh catalyst.

- l4 -~2~

In the rollowlng example, the result~ Or a series or runs are gl~en whereln various metals, lncluslve or zlrconlum, hafnium, cerlum, and uranlum, re3pectlvely, were added to portlons Or a rreshly prepared Co-T102 catalyst, these speclmens of catalyst being compared with a portion Or the Co-T102 catalyst to whlch no promoter metal was added.
These catalysts ~ere calclned by contact wlth alr at elevated temperature in a slmulated coke burn, actlYated by contact wlth hydrogen, and then employed ln a Fl~cher-Tropsch reaction. The metal lmpregnated catalyst~ are compared wlth the control, or portion Or the Co-TiO2 catalyat slmllarly treated except that no promoter metal was added thereto. The ef~ectiYeness of the metal added to the Co-T102 catalyst, or metal promoter, i9 demonstrated by the amount Or C0 conversion obtalned wlth each of the catalyst~
arter the simulated regeneratlon.

Tltania (Degussa P-25 TiO2) was used as the sup-port ror preparatlon of several catalysts. The Degus~a P-25 T102 was admlxed wlth Sterotex~(a vegetable 3tearlne used as a lubrlcant; a product of Capital Clty Products Co.) and, arter pllllng, grindin6, screenlng to 80-150 me~h (Tyler), was calcined in aLr at 6500C for 16 hours to glve rlo2 supports w1th the following properties:

Rutlle:Anata,se Surrace Area Pore Volume Welght Ratio`1) m2/g _ ml/~
97:3 14 0.16 (1) ASTM D 3720-78.

A ~eries Or promoted 11S Co-TiO2 catalyst3 was prepared by impreznation of the TiO2 support using a rotary e~aporator as described below, and the~e compared wlth an unpromoted 11 S Co-TiO2 catalyst in conducting a hydrocarbo~.
synthesis operation.
* Trade Mark .

3L,'~9~.26 -The promoter metal9 were applled to the rio2 9Up-port simultaneously wlth the cobalt, the lmpregnatlng ~olvent u~ed being acetone, ace~one/15-20~ H20, or water (Preparatlon A, ~, or C), or by sequentlal impregnatlon rrom solutlon Or a promoter metal, with lntermedlate aLr treat-ment at temperatures ranging rrom 140C to 500C, wlth a rinal lmpregnatlon of the drled promoter-containing TiO2 composlte wlth a solution o~ cobaltous nltrate (Preparatlons D, E, F, G, and H). These catalyst preparatlon procedures are described below in Table I.
Table I
Catalyst Preparat~on Procedures .
Slmultaneous Impregnatlons _Solvent_ _ _ A Acetone a Acetone/15-20% H20 Solvent Intermedlate ror 2nd Solvent for l~t Air Treat Impregnation Sequentlal Impregnatlon Temperature (Cobalt (-Promoter) C Nitrate) D Isopropanol140 Acstone E Acetone/15S H20 140 Acetone Acetone/15~ H20 500 Acetone G H20 140 Acetone Cataly~ts lmpregnated in thls manner were dried in a vacuum oven at 140C ror about 20 hours. Air treatments were made in rorced-air ovens at varlous temperatures for 3 hours. The catalysts were d-luted 1:1 by volume with 80-150 me h T102 (to minimize temperature gradient~), charged to a 1/4 inch ID reactor tube, reduced in H2 at 450C, 5000 V/Hr/V catalyst for one hour, and then reac~ed with syn~as 3t 200C, 280 psig, CHSV~1500 (on cataly~t), and H2/C0~2 f~r at least 16 hour~. The performance Or each catalyst was ., '~'.

~2~ 26 monltored by conventional GC analysls uslng neon as an lnternal standard (4~ in the ~eed). Activity results are tabulated ln Table II and shown in graphical form in Figures 1 and 2. Hlgh sslectlvity to heavy parafrlnlc hydrocarbons was ob~alned over all Or these Co-TlO2 catalysts independent Or the promoters present. Thus, methane selectlvlty was about 3-5 ~ol. % and C02 selectlrity waa le~s than about 0.2 mol. % ln all runs. The balance Or ehe product was C
hydrocarbona.

~8~6 ,...
Table II
Results of Catalyst Tests Air Treat _ Prep. Temp. % C0 Element ~ e~ Wt.S Procedure C-3 Hr. Conversion None - - A -- 78 n 250 73 n 400 63 " 550 32 ~ 600 28 Hf HfO(N03)2 0.06 A 500 48 0 . 31 n 400 78 " 0.31 " 500 73 " 0.50 " 500 70 n 0.50 1~ 600 58 " 0.63 " 500 71 1.89 1~ 500 78 " 3.0 . " 500 81 Ce (NH4)2Ce(NO3)6 o 55 B 500 79 n 0. 5 E 500 78 " 0.5 F 500 76 ' 0.5 B 600 63 2. 0 E~ 500 64 ~ 2.0 H 500 i~1 7r Zr~0C3H7)4 0.5 D __ 85 " 0.5 D 500 31 zro(02CCH3)2 0.3 C -- 75 n 0. 3 C -- 75 0 . 3 C 500 03 " ~. 6 C 500 68 0. 9 C ~~ 80 0.9 C 500 70 " 1.1 C 500 74 U U02(N03)2 1.0 A 500 79 . .

It i9 clear from these re3ults, a3 deplcte~ by reference to Figure 1, that the zirconium, hafnium, cerium, or uranlum promote, and maintaln the actlvlty of the lls Co-TlO2 catalyst after calcinatlon. The actlvity of promoted 11S Co-TiO2 thus remalns high and virtually constant after ...

~2~9~21~

calcinatlon as high aa 500C whereas, in contra~t, the actlYlty o~ the unpromoted 11% Co-TiO2 catalyAt declines rapldly, and sharply; the rate of actlvlty decreacing dependent upon the temperature o~ calalnatlon.
The data depicted in Figure 2 clearly show the efrectlYeness Or small amounts Or ~irconium, ha~nium, cerium, and uranlum to enhance the re~enerabllity of a 11 Co-TlO2 cataly~t, promotera in concentratlon of about 0.5 wt. percent being adequate for n~ear-maxlmum stabillzation.
Promoters ln greater concentration do not appear to produce any signlflcant additlonal benefit, lf an~.
The hydrocarbon product dlstributlon was further defined ln a run of an 11.2S Co-0.5S Hf-TlO2 catalyat. The catalyst (150 cc) was dlluted with 110 cc TlO2, char~ed to a 1/2 lnch ID reactor, reduced with H2 at 450C ~or 4 hours, and then used for the converslon of syn~as to hydro-carbona. Operating condltlons and product distrlbution data are shown ln Table III. The results conrirm the formatlon o~ very heavy hydrocarbons over Co-Hf-TiO2 catalyst.
Table III
Hydrocarbon Product Dlstrlbution From Co-Hr-TiO2 Temperature, C
Sandbath 20~
Reactor Average 206 Cas Houriy Space Velocity on c~taiyst 10CO
Pre~3ure, p~lg 280 H2/CO Inlet Ratio 2.09 S CO Con~er~ion g9 Hydrocarbon Product Distribution, '~t. S
C1 5.6 C2-C4 3,4 C~-550F 15.1 5~0-700F 10.0 700-1050F 29.2 ,050~ 36.7 .. . . .

9~2~

The followlng example lllustrate~ tha catalysts of thia lnventlon used for the conversion of methanol to hydro-carbon3.

Sitanla ln the form of spherlcal beadq was elupplied by a catalyst manu~acturer and employed to make ca~alysts. The titanLa was of 14-20 me~h e~lze (Tyler), and characterlzed as havln~ a rutile:anatase ratlo of 86:14, a e~urface area of 17 m2/g, and pora volume of 0.11 ml/~m.
Cataly~ts were prepared from por~;ions of the tltania by aimultaneoua lmpregnation with aqueous solution~ containing cobalt nltrate and a salt of ZrO(02CCH3)2, HfO(N03)2, ~NH4)2Ce(N03)6 and U02(N03)2, ree~pectively. Each catalyst, after impregnation, was dried and alr treated at 500C for three hours. The composltion of each of these catalysts in terms of wel3ht percent cobalt and weight percent concentra-tion Or the promoter (1 wt. S) is given in Table IV.
In separa~e runs, each of the promoted Co-TiO2 cataly~lt~ were charKed to a 3/8 inch ID reactor tube, reduced ln hydrogen at 450C, 1000 GHSV, and 0 psig for one hour. A feed admixture of hydrogen, argon, and methanol in molar ratio of 20 CH30H:1H2:4Ar at CH30H LHSV - 0.67, 230C
and 400 psi~ was then passed over each of the catalysts.
The performance of each c~talyst was monitored by conventional CC analy~i~ of the product with the resul~s given in Sable IV.

8~

Table IV
CONVERSION OF METHANOL TO HYOROCAR~ONS
(230~C~ 400 PSIG, LHSV ~ 0.67, 20 CH30H:lH2:4 Ar) Catalyst Compos1tion on TlO2 ~t. ~ Co 5~0 4~344~654~55 4~73 Promoter (1 Wt. %) None Zr Hr Ce U
S CH30H Converglon 31 37 34 49 46 Rate, g CH30H Converted/1.6 2. 3 1 ~ 92.8 2.6 hr./g Co Carbon Product Dlstributlon, Wt. %

c2~ 68 70 69 74 69 ~ .

The results show that the promoted catalysts are more active than unpromoted Co-TiO2 catalyst~, calclned at 500C; whlch 19 best shown by the methanol converslon rate. Cerlum, as wlll be observed, i9 an eapecially good promoter rOr methanol conversion, the cerlum promoted Co-T102 catalyst giving the highest activity and best selec- -tlvity to C2~ hydrocarbons. The ~electivity of the Co-Ti~2 catalyst generally by ad~ition thereto of the respective promoter remains high, and to some extent improved by the pre~ence Or the promoter.
It is apparent that various modificatLons and change~ can be made without departing the spirit and scope of the present invention.
What is claimed i3:

Claims (10)

1. A regeneration stable catalyst for the con-version at reaction conditions of methanol or synthesis gas to hydrocarbons which comprises from about 2 percent to about 25 percent cobalt, based on the weight of the catalyst composition, composited with titania, or a titania-containing support, to which is added a zirconium, hafnium, cerium, or uranium promoter, the weight ratio of the zir-conium, hafnium, cerium, or uranium metal:cobalt being greater than about 0.010:1.

2. The composition of Claim 1 wherein the weight ratio of the zirconium, hafnium, cerium, or uranium metal:cobalt ranges from about 0.04:1 to about 0.25:1.

3. The composition of Claim 1 wherein the catalyst contains from about 5 to about 15 percent cobalt, based on the weight of the catalyst composition.

4. The composition of Claim 1 wherein said titania has a mixture of rutile and anatase crystalline forms with the rutile:anatase ratio content of the titania being at least about 3:2.

5. A regeneration stable catalyst for the con-version at reaction conditions of methanol or synthesis gas to hydrocarbons which comprises cobalt in catalytically active amount composited with titania, or a titania-containing support, to which is added sufficient of a zir-conium, hafnium, cerium, or uranium promoter to obtain, on conversion of methanol or synthesis gas to hydrocarbons with deposition of coke on the catalyst, and the catalyst is regenerated by burning coke therefrom and then reactivated by contact with a reducing gas to reduce the cobalt, an activity, and activity maintenance at corresponding reaction conditions approximating that of a catalyst otherwise similar except that the cobalt-titania catalyst does not contain the added promoter, and has not been regenerated.

6. A process useful for the conversion of methanol or synthesis gas feed to hydrocarbons which com-prises contacting said feed at reaction conditions with a catalyst which comprises from about 2 percent to about 25 percent cobalt, based on the weight of the catalyst com-position, composited with titania, or a titania-containing support, to which is added a zirconium, hafnium, cerium, or uranium promoter, the weight ratio of the zirconium, hafnium, cerium, or uranium metal:cobalt being greater than about 0.010:1.

7. The process of Claim 6 wherein the weight ratio of the zirconium, hafnium, cerium, or uranium metal:cobalt ranges from about 0.04:1 to about 0.25:1.

8. The process of Claim 6 wherein the catalyst contains from about 5 to about 15 percent cobalt, based on the weight of the catalyst composition.

9. The process of Claim 6 wherein the feed con-tacted with the catalyst is an admixture of carbon monoxide and hydrogen, and the reaction conditions are defined within ranges as follows:

H2:CO mole ratio about 0.5:1 to 4:1 Gas Hourly Space Velocities, V/Hr/V about 100 to 5000 Temperature, °C about 160 to 290 Total Pressure, psig about 80 to 600

10. The process of Claim 6 wherein the feed con-tacted with the catalyst is comprised of an admixture of methanol and hydrogen, and the reaction conditions are defined within ranges as follows:

Methanol:H2 ratio greater than about 4:1 Space Velocities, hr-1 about 0.1 to 10 Temperatures, °C about 150 to 350 Methanol Partial Pressure, psia about 100 to 1000