Fischer-Tropsch hydrocarbon synthesis with copper promoted iron/cobalt spinel catalyst

Page 1 — bibliographic record

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or suggest their applicability in conducting or carrying

F SCHERTROPSCH HYDROCARBON out slurry-type Fischer-Tropsch processes.

SYNTHESIS WITH COPPER PROMOTED

RON/COBALT SPINEL CATALYST SUMMARY OF THE INVENTION

CROSS REFERENCE TO RELATED

The present invention relates to unsupported, copper

APPLICATIONS

promoted, high surface area, iron-cobalt spinels, their preparation and use as catalysts in Fischer-Tropsch

This application is a continuation-in-part application hydrocarbon synthesis for selectively producing high of co-pending U.S. Ser. No. 561,192 filed on Dec. 14, 10 amounts of C2 to C20 alpha-olefin hydrocarbons. Thus, 1983 now U.S. Pat. No. 4,544,671. in one embodiment of this invention, the catalysts of this BACKGROUND OF THE INVENTION invention will be used to synthesize hydrocarbons, in cluding C2 to C20 alpha-olefin hydrocarbons, by con 1. Field of the Invention tacting said catalyst, at elevated temperature, with a This invention relates to high surface area, copper 15 gaseous feed mixture of H2 and CO for a time sufficient promoted iron-cobalt spinel Fischer-Tropsch catalysts, to convert at least a portion of said feed to said hydro their preparation and use in Fischer-Tropsch slurry carbons. This reaction is preferably conducted in a processes for selectively producing high amounts of C2 slurry reactor. In a preferred embodiment, the catalyst to C20 alpha-olefin materials. will be further promoted with one or more alkali or 2. Brief Description of the Prior Art alkaline metals of Group IA and IIA. It is particularly Methods for preparing low molecular weight olefins 20 by Fischer-Tropsch processes using coprecipitated preferred Group IA that the additional promoter metal comprise a alkali metal, such as potassium.

iron-based catalysts including cobalt as cocatalyst, are The high surface area iron-cobalt spinels can be pre well-known in the art, as described, for example, in U.S. pared by a process of adding an alpha-hydroxy aliphatic Pats. Nos. 2,850,515; 2,686, 195; 2,662,090; and carboxylic acid, e.g., glycolic acid, to an aqueous solu 2,735,862; Aiche 1981 Summer Natl Meeting Preprint 25

No. 408, "The Synthesis of Light Hydrocarbons from tion containing dissolved iron and cobalt salts and sub sequently evaporating the solution to dryness to yield

CO and H2 Mixtures over Selected Metal Catalysts' an amorphous

ACS 173rd Symposium, Fuel Division, New Orleans, formed precursormixed metal precursor salt. The so salt will then be calcined at elevated

March 1977; J. Catalysis 1981, No. 72(1), pp. 37-50; temperatures

Adv. Chem. Sem. 1981, 194, 573-88; Physics Reports 30 correspondingsufficient high to decompose the salt to the surface area spinel. The unsup

(Section C of Physics Letters) 12 No. 5 (1974) pp. ported, high surface area Fe-Co spinels prepared in this 335-374; UK Patent Application No. 2050859A; J. Ca manner, possess surface areas (BET) in the range of talysis 72, 95-110 (1981); Gmelins Handbuch der Anor ganische Chemie 8, Auflage (1959), pp 88-96; and about 100-200 m2/g (square meters per gram), which Chem. Ing. Tech. 49 (1977) No. 6, pp. 463-468. 35 are significantly higher than corresponding Fe-Co spi It is further known that high levels of cobalt in copre m/g.nels prepared by conventional processes, e.g., 0.2-1.0 cipitated iron-cobalt alloy catalysts produce enhanced selectivity to olefinic products under certain process The copper and, if desired, additional promoter metal conditions, as described in Stud, Surf Catal. 7, Pt/A, pp. or metals will then be added to the so-formed Fe-Co spinel by any means known to those skilled in the are

Although the above-described prior art describes such as incipient wetness impregnation or multiple im catalysts and processes displaying good fixed bed olefin pregnation with one or more promoter metal salt solu synthesis activity, what is particularly desired are slurry tions, etc. The choice being left to the conveniece of the catalysts which can preferably be completely pretreated practitioner. After the promoter metal or metals have in situ in the slurry liquid to yield the reduced, carbided 45 been added to the Fe-Co spinel by surface deposition or active catalysts in the process displaying the combina impregnation, the catalyst compositions of this inven tion of good C2-C20 olefin synthesis activity, low selec tion may be formed by either of the two methods. In tivity to methane, coupled with long-term activity one method, the Fe-Co spinel containing copper and, if maintenace which is essential for a successful commer desired, additional promoter metal, will be charged to cial process. Particularly desired is where the catalyst 50 the reactor where the catalyst composition will be precursor is the metal oxide spinel of the final catalyst formed in-situ by contacting with a mixture of H2 and composition. CO at a temperature sufficient to obtain a fully reduced It has been found that low surface area ironcobalt and carbided or carburized composition which is the spinels having BET surface areas below 5 m2/g are not catalyst of this invention. This may be accomplished readily pretreated in situ in a Fischer-Tropsch slurry 55 under Fischer-Tropsch reaction conditions. liquid under mild conditions to readily yield active In another, alternative method, the Fe-Co spinel con catalysts for producing C2-C20 olefins. taining copper and, if desired, additional promoter The preparation of high surface metal oxides is de metal will be subjected to high temperature, e.g., scribed in the French article, "C. R. Acad. Sc. Paris', 300-400 C., H2 reduction to obtain a fully reduced p268 (May 28, 1969) by P. Courte and B. Delmon. The alloy, followed by treatment with H2/CO at elevated article describes a process for producing high surface temperature (i.e., 300-400 C.) to convert the alloy to a area metal oxides by evaporating to dryness aqueous fully carburized state.

solutions of the corresponding glycolic acid, lactic acid, The resulting copper promoted, high surface area malic or tartaric acid metal salts. One oxide that was reduced and carburized or carbided catalysts provide prepared by their described method was CoFe2O4. 65 unusually high activity, selectivity and activity mainte However, the above references do not describe or nance in the direct conversion of CO/H2 to alpha-ole suggest the use of copper promoted single phase Fe:Co fins under slurry reactor conditions. These catalysts spinels having iron-cobalt atomic ratios of 4:1 or above have higher CO conversion activity and greater selec

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tivity to alpha-olefins than similar compositions which There is further provided a process for synthesizing a are not promoted with copper disclosed in copending hydrocarbon mixture containing C2-C20 olefins com Ser. Nos. 561,190 and 561,192 filed on Dec. 14, 1983. prising the step of contacting a catalyst composition, These catalysts are especially useful in low pressure comprised of an unsupported, copper promoted, iron slurry reactor systems where alpha-olefin residence cobalt spinel, or mixture of said spinels which initially times in the reaction zone can be minimized, and the exhibit a single spinel phase being isostructural with physical properties of the catalyst bed are conducive to Fe3O4, as determined by X-ray diffractometry, and use of finely divided powdered catalysts. possessing an initial BET surface area greater than 5 In accordance with this invention, there is provided a m2/g and an Fe:Coatomic ratio of 4:1 or above, said composition of matter comprising an unsupported, iron 10 contacting conducted with a mixture of CO and hydro cobalt spinel promoted with copper and, if desired, one gen under conditions of pressure, space velocity and or more promoter metals of Group IA and IIA, said elevated temperature for a time sufficient to produce spinel exhibiting a single phase powder X-ray diffraction said C2-C20 olefins.

pattern substantially isostructural with Fe3O4, and pos 15 DESCRIPTION OF THE INVENTION AND sessing a BET surface area greater than 5 m2/g and an PREFERRED EMBODIMENTS iron-cobalt atomic ratio of about 4 to 1 or above. As a practical matter, in most cases the surface area will be at The high surface area iron-cobalt spinels are isostruc least about 50 m2/g. tural with Fe3O4, as determined by X-ray diffractome Further provided is a composition of matter compris try using copper Kalpha radiation and exhibit a single spinel phase. By the term "spinel' is meant a crystal ing a copper promoted iron-cobalt metallic alloy, being 20 structure isostructural with metallic alpha-iron, as determined by whose general stoichiometry corresponds to X-ray diffractometry, and possessing a BET surface AB2O4, where A and B can be the same or different area greater than 5 m2/g, said alloy being produced by cations. Included within this definition is the commonly contacting the above, described Fe:Co spinel with a 25 ing found spinel, MgAl2O4. A and B can have the follow reducing atmosphere. cationic charge combinations: A = --2, B= --3, Also provided is a composition of matter comprising A= +4, B= --2, or A= --6, B= + 1. Spinels contain an a copper promoted, reduced and carbided iron-cobalt approximately cubic close-packed arrangement of oxy gen atoms with of the available tetrahedra. interstices alloy, said composition being substantially isostructural and of the octahedral interstices filled, and can exhibit with Chi-FesC2 (Hagg carbide), as determined by 30 hundreds of different phases. Further description of the X-ray diffractometry, and possessing a BET surface spinel structure can be found in "Structural Inorganic area of greater than 5 m2/g, said composition produced by contacting the above-described iron-cobalt alloy Chemistry' by A. F. Wells, Third Edition, Oxford Press, and the Article "Crystal Chemistry and Some with a carbiding atmosphere. A related composition is Magnetic Properties of Mixed Metal Oxides with the also provided being isostructural with Fe3C (cementite) 35 Spinel Structure' by G. Blasse, Phillips Research Re and having a BET surface greater than 5 m2/g. view Supplement, Volume 3, pp 1-30, (1964). By the Furthermore, there is provided a process for produc term "isostructural' is meant crystallizing in the same ing the copper-promoted, iron-cobalt spinel composi general structure type in that the arrangement of the tion described above comprising the steps of: (a) evapo atoms remains very similar with only minor changes in rating a liquid solution comprising a mixture of iron and 40 unit cell constants, bond energies, and angles. By the cobalt salts of at least one alpha-hydroxy aliphatic car term "single spinel phase' is meant one structural and boxylic acid, wherein the molar ratio of total moles of compositional formula, corresponding to a single spinel said acid to total moles of said iron and cobalt, taken as material into which all of the metal components are the free metals, is about 1:1 or above, and wherein the incorporated, and exhibiting one characteristic X-ray atomic ratio of iron:cobalt, taken as the free metals in 45 diffraction pattern.

said mixture is greater than 2 to 1; yielding an amor These spinels possess a BET surface area greater than phous residue; and (b) calcining said residue at elevated 5 m2/g as determined by the well-known BET surface temperature for a time sufficient to yield an iron-cobalt area measurement technique as described in reference spinel, exhibiting a single phase spinel, isostructural JACS Vol. 60, p. 309 (1928) by S. Brunauer, P. H. Em with Fe3O4, as determined by powder X-ray diffrac 50 mett, G. Teller, and preferably the spinel has a surface tometry followed by promotiring said so-formed single area greater than 50 m2/g and particularly preferred of phase spinel with copper and, if desired, additional about 100 to 300 m2/g. This obtained surface area is in promoter metal of Group IA or IIA or mixture thereof. contrast to conventional methods of spinel formation, It addition, there is provided a process for preparing e.g., high temperature sintering of component oxides in the above-described, copper promoted, iron-cobalt 55 an oxygen-free atmosphere which results in surface alloy composition of matter comprising contacting the areas generally in the range of about 0.1 to 1 m2/g. The above-described copper promoted, iron-cobalt spinel high surface area obtained in the present process corre with a reducing atmosphere under conditions of ele sponds to about 0.01 to 0.002 microns in particle size. vated temperature, pressure and space velocity for a The iron to cobalt atomic ratio of the metals in the time sufficient to substantially reduce the metal oxides 60 spinel is 4:1 or above and is preferably in the range of of the spinel. 7:1 to 35:1, and particularly preferred in the range of There is also provided a process for preparing the 19:1 to 20:1. The amount of copper promoter employed above-described copper promoted reduced and carb will range from about 0.1 to 5 gram atom percent based ided spinel comprising the step of contacting the above on the combined iron and cobalt content of the spinel described copper promoted iron-cobalt metal alloy, 65 preferably the amount of copper promoter will range with a carbiding atmosphere under conditions of ele from about 0.5 to 2 gram atom 9%. As set forth above, vated temperature, pressure and space velocity for a the copper may be deposited on or added to the spinel time sufficient to substantially carbide said alloy. by impregnating the spinel with a solution of a suitable

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copper salt such as copper nitrate, sulfate, halide, ace ducted such that no significant loss in surface area of the tate, etc. final spinel is incurred.

The spinel can be represented by the formula: Fe The key to the synthesis of these spinels is in the use CoO4, wherein x and y are decimal or integer values of an organic, saturated, aliphatic, alpha-hydroxy car other than zero, and wherein the sum of x plusy is 3 and boxylic acid to form a complex salt, which is soluble in the ratio of x toy is 4:1 and preferably being about 7 to the aforementioned aqueous medium, at a pH on the 1 to 35 to 1. Particularly preferred is where the iron to acidic side, i.e., pH of 5-7. The solubility of the iron and cobalt atomic ratio is about 19 to 20 to 1. Illustrative, cobalt organic salts of the alpha-hydroxy carboxylic but non-limiting examples of spinels corresponding to acid prevent crystallization from occurring, resulting in the formula include Fe2.85 Coo.15O4, Fe2.625Co0.375O4, 10 a crystalline product being obtained from the solution, Fe2.97 Co003O4, and Fe2.25Co0.75O4. The composition which would possess a relatively low surface area. utilized may comprise a mixture of spinels in which at This method of preparation utilizes an alphs-hydroxy least two iron-cobalt spinels are present, being isostruc aliphatic carboxylic acid which acts as a solubilizing tural with Fe3O4, having BET surface areas greater agent for the iron and cobalt salts in the aqueous solu than 5 m2/g, wherein said spinels individually possess 15 tion. Any saturated aliphatic alpha-hydroxy carboxylic different iron-cobalt atomic ratios, being 4:1 or above. acid, containing at least one alpha-hydroxy grouping, Physical properties, in general, of these spinels are can be used to form the soluble iron and cobalt salts in similar to those of magnetite, Fe3O4, and include: melt the subject invention process in aqueous solution, is ing point above 1400' and brown to black in color. 20 deemed to be included within the scope of this inven Additional promoter metal selected from the group tion. Representative examples of such acids which can consisting essentially of one or more metals of Group be mono-hydroxy or di-hydroxy or mono-carboxylic or IA and IIA can also be used in the catalyst composition di-carboxylic are glycolic, malic, glyceric, mandelic, to promote olefin formation in a Fischer-Tropsch pro tartaric, lactic acids and mixtures thereof. A preferred cess. General classes of suitable promoter agents in 25 carboxylic acid used in the process is glycolic acid. clude carbonates, bicarbonates, organic acid salts, e.g. The amount of acid used is at least the stoichiometric acetates, inorganic acid salts such as nitrates, halides, amount, i.e., 1 to 1 molar ratio for each metal present sulfates and hydroxides of the Group IA and IIA metals and preferably in about a 5-10% molar excess of the including lithium, sodium, potassium, rubidium, cesium, stoichiometric amount. Higher ratios can be used, if it is barium, calcium, strontium, magnesium, and the like, 30 economical to do so. Lower amounts can also be used Illustrative, but non-limiting examples of specific pro but would result in incomplete iron and cobalt acid salt moter agents include potassium carbonate, potassium formation.

sulfate, potassium bicarbonate, cesium chloride, rubid The first step in the process comprises forming an ium nitrate, lithium acetate, potassium hydroxide, and aqueous solution by dissolving iron salts and cobalt the like. Preferred are the Group IA compounds potas 35 salts, in a water-soluble salt form such as their nitrates, sium carbonate being particularly preferred. These pro sulfates, chlorides, acetates, and the like, in water. moters can be added to the iron-cobalt spinel, if desired, The concentration of the salts in the aqueous liquid is simply by impregnating the iron-cobalt spinel composi not critical to the extent that the salts are present in less tion with an aqueous solution of one or more of said than a saturated solution to avoid precipitation. For promoter agents and drying the resulting impregnate. 40 example, an 80-90% saturated solution, of combined The additional promoter, if used, will generally be dissolved metal molarities for avoiding precipitation in ; : present in about a 0.1 to 10 gram-atom 9% of metal ion the process, can be effectively used. based on the total, combined Fe-Co metals gram-atoms. The temperature of the aqueous solution is not criti A preferred level of promoter agent is in the range of 1 cal and may be above room temperature to aid in the to 2 gram-atom %. A particularly preferred spinel com 45 solubilizing process. However, room temperature is position of the subject invention is Fe2.85Co0.15O4/1% adequate and is the temperature generally used in the Cu, 2% K. process. The pressure also is not critical in the process In the empirical formulas used herein, the amount of and atmospheric pressure is generally used. the promoter agent, e.g., potassium, is expressed in The aqueous solution can also contain a small amount terms of gram atom percent based on the total gram 50 of organic solvent such as ethanol, acetone, and the like atoms of metals used. Thus, "1 gram-atom percent of for aiding in the solubilizing of the iron and cobalt salts potassium' signifies the presence of 1 gram-atom of of the alpha-hydroxy carboxylic acid. potassium per 100 total gram atoms of combined gram Following the dissolving of the iron and cobalt salts, atoms of Fe and Co. the alpha-hydroxy carboxylic acid is added, together The copper-promoted spinels undergo unexpectedly 55 with a sufficient quantity of base, usually being ammo facile in-situ reduction in a slurry liquid and pretreat nium hydroxide, sodium hydroxide, potassium hydrox ment to form copper-promoted iron-cobalt alloys, ide, and the like, preferably ammonium hydroxide, to which are further in situ carbided to form active slurry solubilize the resulting acid salts. The amount of base catalysts in a Fischer-Tropsch slurry process for mak added is sufficient to keep the pH in the range of about ing C2-C20 olefins from CO/hydrogen. 5 to 7.0.

The spinels can be made by a process in which an It should be noted that the exact sequence of steps aqueous solution of cobalt and iron salts of an alpha need not be adhered to as described above, with the hydroxy aliphatic carboxylic acid, is evaporated to proviso that the resulting aqueous solution contain dis dryness, leaving an amorphous residue, which is then solved iron and cobalt salts in stoichiometric amounts as heated at elevated temperature to substantially form the 65 iron and cobalt salts of alpha-hydroxy carboxylic acid spinel, as a single spinel phase, being isostructural with in solution. If there are any insoluble materials present Fe3O4 and possessing a surface area greater than 5 after addition of the base and organic acid, they should m2/g, preferably above 50 m2/g. The heating is con be filtered prior to the evaporation step.

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At this point, the resulting solution is evaporated, as Preferred is where the surface area of either material for example, by air drying, or under reduced pressure, is about 25-200 m2/g and particularly being preferred at elevated temperature, as practiced in a rotary evapo of about 60-150 m2/g, including both the formed Fe-Co rator, or in a vacuum drying oven. carbide and surface carbon formed during the carbiding The resulting material from the evaporation step is an step.

amorphous residue, generally being a powder. This The atomic ratio of the iron:cobalt is not restricted residue is heated at elevated temperature at 100 to 600 for either composition but generally for use in the sub C. for about 1 to 24 hours in generally air to result in a ject process for producing C2-C20 olefins is 4:1 or above substantially single spinel phase which is isostructural and preferably 7:1 to 35:1 and particularly preferred in with Fe3O4, as determined by X-ray diffractometry, as 10 the range of about 19-20:1.

previously described herein. Preferred temperature The copper promoted, carbided iron-cobalt alloy, range is 100-400 C., and particularly preferred is having an X-ray diffraction pattern isostructural with about 350° C. for single phase spinel formation. FesC2, can be produced by carbiding the copper pro A further subject of the instant invention is a compo 15 moted iron-cobalt alloy, described hereinabove, in a sition of matter comprising a copper promoted, re suitable carbiding atmosphere at elevated temperature duced, iron-cobalt metallic alloy formed from the cop of up to about 400° C. Temperatures above 500' lead to per-promoted spinel described above, said alloy being formation of Fe-Co carbides which are isostructural isostructural with alpha-iron, as determined by X-ray with Fe3C, cementite.

diffractometry, and preferably possessing a BET sur 20 Carbiding atmospheres which can be used to produce face area of at least about 5 m/g or higher. the subject reduced, carbided, catalyst include CO, Generally preferred is where the surface area is about CO/hydrogen, aliphatic hydrocarbons, aromatic hy 5-10 m2/g and particularly preferred being 6-8 m2/g. drocarbons, and the like. A preferred carbiding atmo The atomic ratio of iron to cobalt is not restricted and sphere is CO/hydrogen. When using CO/hydrogen can be 4:1 and above. Generally, however, for C2-C20 25 carbiding atmosphere, mixtures of CO/hydrogen can be olefin synthesis in the subject process described herein, used inused a 1:10 to 10:1 molar volume ratio. A preferred the iron-cobalt atomic ratio is preferably about 4 to 1 ratio for carbiding purposes is a 1:1 molar ratio. and above and more preferably being about 7 to 1 to 35 perature of aboutstep

The carbiding is generally conducted at a tem to 1 and a particularly preferred range is of about 19:1 to 300 to 400° C. A250 C., or above and preferably at preferred method of carbiding the

The copper-promoted iron-cobalt alloy can be pro 30 alloy is in situ in the slurry liquid to be used in the Fisch er-Tropsch process. A particularly preferred method is duced by reducing the above-described copper pro where the spinel moted iron-cobalt spinel in a reducing atmosphere at gen and reduced isandtreated with a mixture of CO/hydro carbided in situ in one step prior to elevated temperature generally of about 240° C. and above and preferably 300' to 400° C. The reduction can 35 hydrocarbon synthesis. The pressure is generally about 1 atmosphere, and a space velocity of about 20-20,000 be carried out with various reducing gases including v/v/hr hydrogen, H2/CO, and the like, and mixtures thereof. starting isiron-cobalt chosen in order to completely carbide the

Preferably hydrogen gas alone is generally used in an X-ray diffractometryoxide when which can be determined by the material becomes isos inert carrier medium such as helium, neon, argon, or tructural with Haag carbide, nitrogen, in the absence of CO when substantially pure, Fe-Co carbides produced in thisFesC2. The Haag-type process are of the gen " non-carbided alloy is desired.

The alloy can be prepared ex situ in a tube reactor or eral formula: Fes-(5/3)Co(5/3)C2, and also include surface carbon produced during the carbiding process.

in situ in a Fischer-Tropsch slurry process. The in situ Carbiding temperatures above 500' C. and preferably preparation is conducted in the slurry apparatus when 500-700' C., lead to formation of a mixed Fe-Co car the above described copper-promoted spinel is reduced 45 bide of the general while suspended in the slurry liquid, in a reducing atmo ally formed under formula ex situ

Fe3-yCoC, which is gener procedures which allow the sphere being preferably a hydrogen atmosphere at ele use of higher temperatures than possible in the in situ vated temperature being about 240 C., or above, pref slurry process.

erably at 240-300 C., at a space velocity, pressure, and The resulting carbide is an active slurry catalyst for hydrogen concentration sufficient to cause substantial 50 producing C-C20 olefins in the described Fischer reduction of the spinel to the alloy. Substantial reduc Tropsch slurry process.

tion is complete when the X-ray diffraction pattern If the above-described alloy and carbide, are pre shows a pattern substantially isostructural with alpha pared ex-situ or independently of the slurry apparatus,

they may be pyrophoric and inconvenient to handle. In

The above-described alloy is useful informing a carb 55 that case, the material may be passivated by contact ided, copper-promoted iron-cobalt catalyst useful in the with oxygen for a sufficient time to reduce or eliminate subject Fischer-Tropsch slurry process for making th pyrophoric tendency. Generally, the oxygen used in C2-C20 olefins, as described herein. the passivating process is used in an inert gas stream Also, subject of the instant invention are composi carrier such as helium for a sufficient time to cause tions of matter being copper promoted, reduced and 60 passivation. Generally, this is conducted preferably at carbided iron-cobalt alloys, one being isostructural with room temperature, at a pressure and space velocity FesC2, "Hagg carbide” as described in Trans, of the Iron which are convenient and easy to control and to maxi & Steel Inst, of Japan, Vol. 8, p. 265 (1968) by Nagakura mize the efficiency of the process needed for complete et al., as determined by X-ray diffractometry and pos passivation.

sessing a BET surface area of greater than 5 m2/g; and 65 Also, a subject of the instant invention is a Fischer two, being isostructural with Fe3C "cementite', as de Tropsch process for producing C2-C20 olefins by utiliz termined by X-ray diffractometry, and possessing a ing the copper promoted iron-cobalt spinel, copper BET surface area of greater than 5 m2/g. promoted iron-cobalt alloy and the reduced, carbided,

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copper promoted iron-cobalt spinel catalyst described lene, C1-C12 mono- and multi-alkyl substituted ben hereinabove, zenes, dodecylbenzene, naphthalene, anthracene, biphe Although a fixed bed process can be used, a preferred nyl, diphenylether, dodecylamine, dinonylamine, trioc process mode for operating the Fischer-Tropsch pro tylamine, and the like. Preferred liquid hydrocarbon cess utilizing the catalysts described herein is a slurry slurry solvent is octacosane or hexadecane. type process wherein the catalyst in fine particle size and high surface area being above 5 m2/g is suspended bonThe amount of catalyst used in the liquid hydrocar in a liquid hydrocarbon and the CO/hydrogen mixture catalyst persolvent slurry

is generally about 10 to 60 g of dry slurry liquid. Preferably about 30 to forced through the catalyst slurry allowing good 50 g. dry catalyst per contact between the CO/hydrogen and the catalyst to 10 lized, being in about a500respective g. slurry liquid slurry is uti

initiate and maintain the hydrocarbon synthesis process. ratio.

Advantages of a slurry process over that of a fixed The slurry system, comprised of the slurry liquid and bed process are that there is better control of the exo finally divided catalyst, is generally stirred to promote thermic heat produced in the Fischer-Tropsch process good dispersion during the reaction and that better control over catalyst 15 to avoid catalyst during settling the pretreatment in the process and to eliminate mass transport activity maintainance by allowing continuous recycle, limitations between the gas and liquid phases. In a typi recovery, and rejuvenation procedures to be imple mented. The slurry process can be operated in a batch cal laboratory unit the rate of stirring is generally car ried out in the range of about 600 to 1,200 rpm and or in a continuous cycle, and in the continuous cycle, preferably the entire slurry can be circulated in the system allow 20 Prior to 1,000 to 1,200 rpm. the CO/hydrogen hydrocarbon synthesis ing for better control of the primary products residence time in the reaction zone. run, the reduced and carbided, copper promoted iron The subject process can use any of the above de cobalt catalyst is generally conditioned in the apparatus scribed materials, as catalyst or catalyst precursors; the by purging with nitrogen to remove reactive oxygen copper promoted iron-cobalt spinel isostructural with 25 containing gases and then the temperature is increased Fe3O4; the copper promoted iron-cobalt alloy isostruc while stirring to the reaction temperature range. Then tural with alpha-iron; or, the reduced, carbided, copper the system is generally subjected to a hydrogen treat . . promoted iron-cobalt alloy which is isostructural with ment for a sufficient time to insure complete removal of FesC2, or Fe3C. All the materials must have a BET any surface metal oxide present which would interfere surface area of greater than 5 m2/g, to be applicable in 30 in hydrocarbon synthesis.

the efficient claimed slurry process described herein. Optionally, and preferably if the catalyst is prepared These materials can also be made independently of the in situ, then the hydrogen treatment is generally not apparatus prior to use or can be made in situ in the required or is only practiced for a short period of time, apparatus during the carrying out of the process. A The pressure and space velocity during the inert gas preferred procedure is where the copper promoted 35 hydrogen conditioning step are not critical and can be spinel, in high surface area form is pretreated in situ in utilized in the range which is actually used during actual the slurry liquid, in either distinct reduction-carbiding hydrocarbon synthesis.

steps or in one reduction-carbiding step as with CO/hy Following the conditioning step, the CO/hydrogen . . drogen at elevated temperature. A full discussion of feedstream is introduced into the slurry catalyst cham each of the materials, their properties and their prepara 40 ber and the pressure, space velocity, temperature, and tion are given hereinabove and need not be reiterated. hydrogen/CO molar ratio is then adjusted, as desired, The slurry liquid used in the process is a liquid at the for hydrocarbon synthesis conditions. reaction temperature, must be chemically inert under In the process, the hydrogen and CO are used in a the reaction conditions and must be relatively good molar ratio in the gaseous feedstream in about a 10:1 to solvent for CO/hydrogen and possess good slurrying 45 1:10 molar ratio, preferably 3:1 to 0.5:1, and particularly and dispersing properties for the finely divided catalyst. preferred 1:1 to 2:1 molar ratio. Representative classes of organic liquids which can be utilized are high boiling paraffins, aromatic hydrocar range of about 200 toin 300

The temperature the process is generally in the

C., preferably being 230 to bons, ethers, amines, or mixtures thereof. The high 270° C., and particularly preferred of about 240-260 boiling paraffins include Clo-C50 linear or branched 50 parafinnic hydrocarbons; the aromatic hydrocarbons C. Higher temperature ranges can also be used but tend include C2-C20 single ring and multi- and fused ring to lead to lighter products and more methane, lower aromatic hydrocarbons; the ethers include aromatic temperature ranges can also be used but tend to lead to ethers and substituted aromatic ethers where the ether lower activity and wax formation. oxygen is sterically hindered from being hydrogenated; 55 The pressure useful in the process is generally con the amines include long chain amines which can be ducted in the range of about 50 to 400 psig and prefera primary, secondary, and tertiary amines, wherein pri bly about 70 to 225 psig. Higher pressures can also be mary amines preferably contain at least a C12 alkyl used but tend to lead to waxy materials particularly in group in length, secondary amines preferably contain at combination with lower temperature. least two alkyl groups being C7or greater in length, and The space velocity used in the process is generally tertiary amines preferably contain at least three alkyl about 100 to 4,000 volumes of gaseous feedstream/per groups being C6 or higher in length. The slurry liquid volume of dry catalyst in the slurry/per hour and is can contain N and O in the molecular structure but not preferably in the range of about 400 to 1,200 v/v/hr, S, P, As or Sb, since these are poisons in the slurry and particularly preferred of 800-1,200 v/v/hr. Higher process. Representative examples of specific liquid 65 space velocities can also be used but tend to lead to slurry solvents useful are dodecane, tetradecane, hexa lower % CO conversion, and lower space velocities can decane, octadecane, cosane, tetracosane, Octacosane, also be used but tend to lead to more paraffinic prod tetratetracontane, toluene, o-, m-, and p-xylene, mesity ucts.

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Generally, after the pretreatment, the CO/hydrogen feedstream is introduced to initiate and maintain hydro EXAMPLE 1 carbon synthesis. Preparation of Fe2.85Co0.1504 Spinel The percent CO conversion obtainable in the subject process, while providing substantial quantities of 5 7.5198.04 grams grams of ferric nitrate in 144 cc of water and of cobalt nitrate in 8 cc of water were mixed

C2-C20 olefins, will generally range from about 30 to 80 together. To percent and usually from about 50 to 60 percent for grams of 85%this solution was added a solution of 41.6 glycolic acid containing 45 cc of ammo sufficient C2-C20 olefin production. nium hydroxide such that the resulting pH of the ammo "Total hydrocarbons' produced in the process is nium glycolate solution was about 6.5. The ammonium related to the selectivity of percent CO conversion to 10 glycolate hydrocarbons being those hydrocarbons from C1 to solution constituted 0.51 moles of glycolic about C40 inclusive. Total hydrocarbon selectivity is acid such that about a one to one molar ratio of total generally 0 to 50 percent and higher, of the total CO metals including iron and cobalt to glycolic acid re converted, and the remainder converted to CO2. sulted. The ammonium glycolate solution was added to The percent C2-C20 hydrocarbons of the total hydro 15 the aqueous solution containing iron and cobalt salts carbons produced including methane and above is about and the contents stirred. The resulting solution was 60 to 90 wt.%. The percent of C2-C20 olefins produced, allowed to evaporate by air drying. Upon drying at of the C2-C20 total hydrocarbons produced is about 60 room temperature the resulting solid was shown by to 70 wt.%. The olefins produced in the process are X-ray diffraction to be an amorphous material because substantially alpha olefins. 20 of lack of sharp discrete reflections. The solid was The selectivity to methane based on the amount of heated in air at 350° C. for 2 hours. An X-ray diffraction CO conversion is about 1 to 10 weight percent of total pattern of the resulting material showed it to be a single hydrocarbons, produced. Preferably about 5 percent, phase cobalt-iron spinel isomorphous with Fe3O4. The and lower, methane is produced in the process. X-ray diffraction peaks were broadened relative to a As discussed above, the percent selectivity to CO2 25 compositionally equivalent material obtained by a high formation in the process is about 10 to 50 percent of CO temperature procedure. This indicated that the resulting converted. obtained material was of very small particle size. Preferably, the reaction process variables are ad A number of different batches of this spinel were justed to minimize CO2 production, minimize methane prepared using the procedure set forth above. In all production, maximize percent CO conversion, and max 30 cases, the surface area of the resulting material ranged imize percent C2-C20 olefin selectivity, while achieving from about 80 to 200 square meters per gram. activity maintenance in the catalyst system. Preparation of Fe3O4. Generally, this format can be derived in a preferred mode of operating the process where the slurry liquid For comparative purposes, Fe3O4 was prepared from used is hexadecane, the catalyst used is Fe2.85Co0 35 ferric nitrate, glycolic acid and ammonium hydroxide 15O4/1%Cu, 2% K, the catalyst/liqud weight ratio is using the procedure set forth above for the Fe2.85Co0 40/500, the system is stirred at 1,200 rpm, and pretreat 15O4 spinel, except that no cobalt salt was employed. ment procedure is conducted in situ in a one step proce Impregnation With Promoter dure using 9:1H2/N2 at 220 C., atmospheric pressure, 1200 v/v/hr. space velocity, for a period of 5 hrs., and Samples of the spinel and Fe3O4 prepared as set forth the process conducted at the hydrogen:CO molar ratio above were impregnated with either potassium or a is 1:1, the temperature is conducted at about 245 C., at mixture of potassium and copper. For the copper im a pressure of 7-150 psig, and space velocity 1,000-1200 pregnation, an aqueous solution of cupric nitrate hexa v/v/hr. By carrying out the above process in the stated hydrate was used in an amount sufficient to deposit one variable ranges efficient activity maintenance and pro 45 gram atom 9% of Cu on the spinel, based on the com duction of C2-C20 olefins can be achieved. bined Fe and Co content. The resulting copper impreg The effluent gases in the process exiting from the nate was then dried in air for about two hours at 125 C. reactor may be recycled if desired to the reactor for Following the Cu impregnation, samples of the dried further CO hydrocarbon synthesis. impregnate were further impregnated with one gram Methods for collecting the products in the process 50 atomic percent of potassium using an aqueous solution are known in the art and include fractional distillation, of potassium carbonate followed by drying of the result and the like. Methods for analyzing the product liquid ing impregnated sample at 125 C. Some samples were hydrocarbons and gaseous streams are also known in impregnated only with K. Resulting solid had an empir the art and generally include gas chromatography and ical formula of Fe2.85Co0.15O4/1% K.

the like. 55

Apparatus useful in the preferred process is any con Preparation of Carbide Ex-Situ ventional slurry-type reactor, being horizontal or verti In those cases where the catalyst was prepared ex cal, being stationary or cyclical, in catalyst slurry. situ, the promoted iron or iron-cobalt spinel was treated Other apparatus not specifically described herein will at 400° C. in a stream of 40 volume percent hy be obvious to one skilled in the art from a reading of this 60 drogen/40% helium/20% CO at 200 V/V/hr. for disclosure. twentyfour hours. Following this, the sample was The invention will be more readily understood by cooled to room temperature and 1.0% oxygen in helium reference to the examples below. was introduced for one hour to passivate the material. EXAMPLES The X-ray diffraction pattern of the resulting material 65 was isostructural with FesC2. The BET nitrogen sur

Unless otherwise indicated, the selectivity weight face area of the material was at least about 150 m2/g. percentages of product hydrocarbons is given on a Analysis showed that about 40-50 weight percent of the CO2-free basis. material was carbon and thus the material was a com

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posite of Fes-Cox C2/2 gram-atom 9% K, and, in some TABLE 2-continued cases, 1% Cu. and surface carbon. In this case x=0 or 0.25. Catalysts Prepared In-Situ and Ex-Situ

Catalyst Runs 2% K 1% CU, 2% K 1% Cu, 2% K

Into a slurry reactor, being a 300 cc Parr CSTR (con produced in tinuous stirred tank reactor) was charged: 50 g of octa C2-C4 hydro cosane and 8.0 of either the ex-situ carbided catalyst or carbon fraction the Cu and/or K promoted Fe or Fe-Co spinel prepared Cio distribution as set forth above. In those cases where the reactor was 10 or - olefins 50 46 59 charged with a promoted spinel that had not been carb (3m -- alcohols

ided ex-situ, the catalyst was formed in-situ in the reac n - paraffins 17 18 15 tor. Ali Else 23 29 21 After a sample of catalyst or promoted spinel catalyst precursor was loaded into the reactor, the system was 15 What is claimed is:

purged with nitrogen and then placed under CO hydro 1. A process for synthesizing a hydrocarbon mixture genation reaction conditions by adjusting the reaction containing C2-C20 olefins comprising contacting a cata temperature to 270° C., the H2/CO volume ratio to 2/1, lyst composition, comprising an unsupported, copper the space velocity to 2,000 V gaseous feedstream/V dry promoted iron-cobalt spinel, said spinel exhibiting a catalyst/hr, the pressure to 75 psig, and the slurry stir single phase being isostructural

with Fe3O4 as deter rer speed to 600 rpm in the octacosane solvent.

The actual gas flow rate through the reactor was an initial BET surface area greater than and mined by powder X-ray diffractometry,

possessing m2/g and an 120/60/20 cc per min. of H2/CO/N2. The effluent gas Fe:Coatomic ratio of 4:1 and above, with a mixture of from the reactor was monitored by an HP-5840A Refin 25 CO and hydrogen in a slurry liquid under conditions of ery Gas analyzer to determine percent CO conversion pressure, space velocity, and elevated temperature, for and the nature of the hydrocarbon products.

The results are set forth in Tables 1 and 2 below. In a time sufficient to produce said C2-C20 olefins. all cases, the values reported were determined after the selected 2. The process of claim 1 wherein said slurry liquid is catalyst had been on-stream in the reactor for a period 30 hydrocarbons, from high boiling liquid paraffins, aromatic of at least 16 hours. ethers, amines, or mixtures thereof Referring to the Tables, Table 1 sets forth the results liquid paraffins areofC12-C60 3. The process claim 2 wherein said high boiling of three different catalysts formed in-situ in the reactor aliphatic hydrocarbons. linear or branched saturated from the promoted Fe or Fe/Co spinel. The results 4. The process of claim 3 wherein said hydrocarbon show the high selectivity of a-olefin production 35 slurry liquid is selected from octacosane, hexadecane, achieved by the copper promoted catalyst of this inven tion compared to a similar catalyst which was not pro or5.mixtures The thereof.

process of claim 1 wherein said hydrogen and moted with copper. The data for the Fe spinel merely serves as a comparison for conventional iron catalysts. CO are present in a hydrogen/CO molar ratio of 1:10 to Table 2 compares the result obtained using a catalyst of 10:1.

this invention prepared both in-situ and ex-situ. These in 6.theThe process of claim 1 wherein said temperature is

: data illustrate that the catalysts of this invention are preferably prepared in-situ for greatest alpha olefin the7.range The process of claim 1 wherein said pressure is in of about 50 to 250 psig.

selectivity.

8. The process of claim 1 wherein said space velocity

TABLE I 45 is in the range of about 100 to 4000 v/v/hr.

Catalysts Prepared In-Situ in The Reactor 9. The process of claim 1 wherein the weight ratio of Fe3O4/ Fe2.85Col5O4/ Fe2.85Co.1504/ slurry liquid to dry catalyst is in the range of about 10:1

% CO conversion % CH4 make

10. The process of claim 1 wherein said copper pro 50 moted spinel is reduced and carbided in situ in the pro % olefins in C2-C4 47.5 91 87 cess in the slurry liquid.

hydrocarbon fraction 11. The process of claim 1 wherein the catalyst is C10 distribution reduced and carbided ex situ. a - olefins n - paraffins

12. The process of claim 1 wherein said carbided, 55 reduced, copper promoted spinel is isostructural with m - alcohols 10 3

R - olefins 4.1 2 FesC2, or Fe3C, as determined by powder X-ray dif. All Else 31 21 fractometry.

Note 13. The process of claim 1 wherein said iron and No measurable amount of Clo's produced with this catalyst. cobalt are present in an iron-cobalt atomic ratio of 4:1 or above and wherein said copper is present in an amount

TABLE 2 of from about 0.1 to 5 gram atom 9% of the iron and cobalt.

Catalysts Prepared In-Situ and Ex-Situ 14. The process of claim 13 wherein said atomic iron Fe3O4/s. Fe2.85Co.5O4/ Fe2.85CO.15O4/ cobalt ratio is 7:1 to 35:1.

ex-situ ex-situ in-situ 65 15. The process of claim 14 wherein said iron-cobalt % CO conversion 49 54 86 atomic ratio is 19-20:1. % CH4 make 3.8 4.5 4.2 16. The process of claim 1 wherein said spinel has an % olefins 77 85 87 initial BET surface area of at least about 50 m2/g.

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17. The process of claim 16 wherein said spinel has a 20. The process of claim 19 wherein additional said BET surface area of from about 70 to 220 m2/g. promoter agent is potassium carbonate. 18. The process of claim 1 wherein said catalyst com 21. The process of claim 1 wherein said spinel catalyst position further comprises a Group A and IIA pro composition is Fe2.85Co0.15 O4 with 2 gram-atom 26 K moter agent present in about 0.1 to 10 gram-atom per 5 and 1 gram atom % Cu.

cent of said total gram-atoms of metals content. 22. The process of claim 1 wherein said product hy 19. The process of claim 18 wherein said promoter drocarbon mixture contains 60 wt.% C2-C20 olefins. agent is selected from the group of carbonate, bicarbon 23. The process of claim 1 wherein said hydrocarbon ate, organic acid salts, inorganic acid salts, nitrate, hal mixture contains a C2/C20 paraffins and olefins in an ide, sulfate, and hydroxides of Group IA and IIA met 10 olefins/paraffins weight ratio of 3:1. als. a a sk