Process for preparing high surface area iron/cobalt Fischer-Tropsch slurry catalysts

Page 1 — bibliographic record

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the process of adding an alpha-hydroxy aliphatic car

PROCESS FOR PREPARING HIGH SURFACE boxylic acid, e.g., glycolic acid, to a solution containing AREA IRON/COBALT FISCHER-TROPSCH dissolved and cobalt salts and subsequently evaporating SLURRY CATALYSTS s the solution to dryness to yield an amorphous mixed metal oxide, which on calcining at elevated tempera

BACKGROUND OF THE INVENTION ture, exhibits a spinel crystal structure and possesses a 1. Field of the Invention high surface area. W This invention relates to high surface area iron-cobalt The unsupported high surface area Fe-Co spinels Fischer-Tropsch slurry catalysts, their preparation and 10 prepared in this manner, possess surface areas (BET) in use in Fischer-Tropsch slurry processes for selectively the range of about 100-200 m2/g (square meters per producing high amounts of C2 to C20 alpha-olefin mate gram), which are significantly higher than correspond rials. ing Fe-Co spinels prepared by a conventional process, 2. Brief Description of the Prior Art e.g., 0.2-1.0 m2/g.

Methods for preparing low molecular weight olefins After the addition of promoter agents, by surface by Fischer-Tropsch processes using coprecipitated 5 deposition or impregnation, Such as alkali carbonate, iron-based catalysts including cobalt as cocatalyst, are the high surface area spinels are then subjected to high well-known in the art, as described, for example, in U.S. temperature, e.g., 300-400 C., H2 reduction to obtain Pat. Nos. 2,850,515; 2,686, 195; 2,662,090; and 2,735,862; a fully reduced alloy, followed by treatment with AICHE 1981 Summer Natl Meeting Preprint No. 408, H2/CO at 300-400° C. to convert the alloy to a fully “The Synthesis of Light Hydrocarbons from CO and 20 carburized state.

H2 Mixtures over Selected Metal Catalysts' ACS 173rd The resulting high surface area reduced and carbu Symposium, Fuel Division, New Orleans, March 1977; rized

J. Catalysis 1981, No. 72(1), pp. 37-50; Ady. Chem. Sem. tivity catalysts, and provide unusually high activity, selec activity maintenance in the direct conversion 1981, 194, 573-88; Physics Reports (Section C of Physics 25 of CO/H2 to alpha-olefins under slurry reactor condi

cation No. 2050859A; J. Catalysis 72, 95-110 (1981); tions. These catalysts are especially useful in low pres sure slurry reactor systems where alpha-olefin residence

Gmelins Handbuch der Anorganische Chennie 8, Auflage times in the reaction zone can be minimized, and the (1959), pp 88-96; and Chem. Ing. Tech. 49 (1977) No. 6, physical properties of the catalyst bed are conducive to pp. 463-468. use of finely divided powdered catalysts. It is further known that high levels of cobalt in copre 30 cipitated iron-cobalt alloy catalysts produce enhanced In accordance with this invention, there is provided a selectivity to olefinic products under certain process composition of matter comprising an unsupported, conditions, as described in Stud, Surf Catal. 7, Pt/A, Group IA or IIA metal salt promoted iron-cobalt spinel pp. 432 (1981). or mixture thereof, said spinel exhibiting a single phase Although the above-described prior art describes 35 powder X-ray diffraction pattern substantially isostruc catalysts and processes displaying good fixed bed olefin tural with Fe3O4, and possessing a BET surface area synthesis activity, what is particularly desired are slurry greater than 5 m2/g and an iron-cobalt atomic ratio of catalysts which can preferably be completely pretreated about 4 to 1 or above.

in situ in the slurry liquid to yield the reduced, carbided Further provided is a composition of matter compris active catalysts in the process displaying the combina 40 ing an iron-cobalt metallic alloy, being isostructural tion of good C2-C20 olefin synthesis activity, low selec with metallic alpha-iron, as determined by X-ray dif tivity to methane, coupled with long-term activity fractometry, and possessing a BET surface area greater maintenance which is essential for a successful commer than 5 m2/g, said alloy being produced by contacting cial process. Particularly desired is where the catalyst the above, described Fe:Co spinel with a reducing at precursor is the metal oxide spinel of the final catalyst 45 mosphere.

composition. Also provided is a composition of matter comprising It has been found that low surface area iron-cobalt a reduced and carbided iron-cobalt alloy, said composi spinels having BET surface areas below 5 m2/g are not readily pretreated in situ in a Fischer-Tropsch slurry tion (Hagg being substantially isostructural with Chi-Fesc2 carbide), as determined by X-ray diffractometry, liquid under mild conditions to readily yield active and possessing

a BET surface area of greater than 5 catalysts for producing C2-C20 olefins. m2/g, said composition produced by contacting the The preparation of high surface metal oxides is de above-described iron-cobalt alloy with a carbiding at scribed in the French article, "C. R. Acad. Sc. Paris', mosphere. A related composition is also provided being p268 (May 28, 1969) by P. Courte and B. Delmon. The isostructural with Fe3C (cementite) and having a BET article describes a process for producing high surface 55 area metal oxides by evaporating to dryness aqueous surface greater than 5 m2/g. solutions of the corresponding glycolic acid, lactic acid, ingFurthermore, there is provided a process for produc the iron-cobalt spinel composition described above malic or tartaric acid metal salts. One oxide that was prepared by their described method was CoFe2O4. comprising the steps of: (a) evaporating a liquid solution However, the above references do not describe or 60 comprising a mixture of iron and cobalt salts of at least suggest the use of single phase Fe:Co spinels having one alpha-hydroxy aliphatic carboxylic acid, wherein iron-cobalt atomic ratios of 4:1 or above or suggest their the molar ratio of total moles of said acid to total moles applicability in conducting or carrying out slurry-type of said iron and cobalt, taken as the free metals, is about Fischer-Tropsch processes. 1:1 or above, and wherein the atomic ratio of iron:- 65 cobalt, taken as the free metals in said mixture is greater

SUMMARY OF THE INVENTION than 2 to l; yielding an amorphous residue; and (b) It has been found that high surface area, in situ, pre calcining said residue at elevated temperature for a time treatable iron-cobalt slurry catalysts can be prepared by sufficient to yield an iron-cobalt spinel, exhibiting a

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single spinel phase, isostructural with Fe3O4, as deter area is in contrast to conventional methods of spinel mined by powder X-ray diffractometry. formation, e.g., high temperature sintering of compo In addition, there is provided a process for preparing nent oxides in an oxygen-free atmosphere. The surface the above-described iron-cobalt alloy composition of area is generally in the range of about 0.1 to 1 m2/g. The matter comprising contacting the above-described iron 5 high surface area obtained in the present process corre cobalt spinel, with a reducing atmosphere under condi sponds to about 0.01 to 0.002 microns in particle size. tions of elevated temperature, pressure, space Velocity The iron to cobalt atomic ratio of the metals in the for a time sufficient to substantially reduce the metal spinel is 4:1 or above and is preferably in the range of oxides of the spinel. 7:1 to 35:1, and particularly preferred in the range of There is also provided a process for preparing the 10 19:20-1.

above-described reduced and carbided spinel compris The spinel can be represented by the formula: Fe ing the step of contacting the above-described iron CoyO4, wherein x and y are decimal or integer values cobalt metal alloy, with a carbiding atmosphere under other than zero, and wherein the sum of x plus y is 3 and conditions of elevated temperature, pressure, space the ratio of x to y is 4:1 and preferably being about 7 to velocity, for a time sufficient to substantially carbide 15 to 35 to 1. Particularly preferred is where the iron to said alloy. cobalt atonic ratio is about 19 to 20 to 1. There is further provided a process for synthesizing a Representative examples of the various spinels corre hydrocarbon mixture containing C2-C20 olefins com sponding to the formula are Fe2.85Co0.15O4, Fe2.62. prising the step of contacting a catalyst composition, 5Co0.375O4, Fe2.97Co0.03O4, and Fe2.25Co0.75O4. comprised of an unsupported iron cobalt spinel, or mix Physical properties, in general, of these subject spi ture thereof, said spinel initially exhibiting a single spi nels are similar to those of magnetite, Fe3O4, and in nel phase being isostructural with Fe3O4, as determined clude: melting point above 1400 and brown to black in by X-ray diffractometry, and possessing an initial BET color.

surface area greater than 5 n2/g and an Fe:Coatomic The iron-cobalt spinels are generally used in unsup ratio of 4:1 or above, said contacting conducted with a ported form in the slurry process. mixture of CO and hydrogen under conditions of pres A promoter agent can also be used in the composition sure, space velocity and elevated temperature for a time and can be used to particularly promote olefin forma sufficient to produce said C2-C20 olefins. tion, for example, in the process. General classes of

DESCRIPTION OF THE INVENTION AND

suitable promoter agents include carbonates, bicarbon 30 ates, organic acid salts, e.g. acetates, nitrates, halides,

PREFERRED EMBODIMENTS sulfates, hydroxides of Group IA and IIA metals includ The subject high surface area iron-cobalt spinels are ing lithium, sodium, potassium, rubidium, cesium, bar new compositions of matter which are isostructural ium, calcium, strontium, magnesium, and the like. with Fe3O4, as determined by X-ray diffractometry Representative examples of specific promoter agents using copper K alpha radiation and exhibit a single 35 are potassium carbonate, potassium sulfate, potassium spinel phase. By the term "spinel' is meant a crystal bicarbonate, cesium chloride, rubidium nitrate, lithium structure whose general stoichiometry corresponds to acetate, potassium hydroxide, and the like. Preferred AB2O4, where A and B can be the same or different are the Group A compounds and a particularly pre cations. Included within this definition is the commonly ferred promoter agent is potassium carbonate. found spinel, MgAl2O4. A and B can have the following The promoter, if used, is generally present in about a cationic charge combinations: A = --2, B = +3, 0.1 to 1 gram-atom 7% of metal ion based on the total A = +4, B= --2, or A = + 6, B= -- 1. Spinels contain an combined metals gram-atoms. A preferred level of pro approximately cubic close-packed arrangement of oxy moter agent is in the range of 1 to 2 gram-atom 9%. A gen atoms with th of the available tetrahedral inter particularly preferred spinel composition of the subject stices and of the octahedral interstices filled, and can 45 invention is Fe2.85Co0.15O4/1% K as potassium carbon exhibit hundreds of different phases. Further descrip ate. In the empirial formulas used herein, the amount of tion of the spinel structure can be found in "Structural the promoter agent, e.g., potassium, is expressed in Inorganic Chemistry' by A. F. Wells, Third Edition, terms of gram atom percent based on the total gram Oxford Press, and the Article “Crystal Chemistry and atoms of metals used. Thus, 'l gram-atom percent of Some Magnetic Properties of Mixed Metal Oxides with potassium' signifies the presence of 1 gram-atom of the Spinel Structure' by G. Blasse, Phillips Research potassium per 100 total gram atoms of combined gram Review Supplement, Volume 3, pp. 1-30, (1964). By the atoms of Fe and Co.

term "isostructural' is meant crystallizing in the same The utility of the subject spinels is their ability, to general structure type in that the arrangement of the undergo unexpectedly facile in situ reduction in the atoms remains very similar with only minor changes in 55 slurry liquid and pretreatment to form iron-cobalt al unit cell constants, bond energies, and angles. By the loys, which are further in situ carbided to form active term "single spinel phase' is meant one structural and slurry catalysts in a Fischer-Tropsch slurry process for compositional formula, corresponding to a single spinel making C2-C20 olefins from CO/hydrogen. material into which all of the metal components are The subject spinel composition can be made by a incorporated, and exhibiting one characteristic X-ray 60 process in which a solution of and iron salts of an alpha diffraction pattern. hydroxy aliphatic carboxylic acid, is evaporated to The spinel possesses a BET surface area greater than dryness, leaving an amorphous residue, which is then 5 m2/g as determined by the well-known BET surface heated at elevated temperature to substantially form the area measurement technique as described in reference spinel, in a single spinel phase, being isostructural with JACS Vol. 60, p. 309 (1928) by S. Brunauer, P. H. Em 65 Fe3O4 and possessing a surface area greater than 5 mett, and G. Teller, and preferably the spinel has a m2/g, preferably above 50 m2/g. The heating is con surface area greater than 50 m2/g and particularly pre ducted such that no significant loss in surface area of the ferred of about 100 to 300 m2/g. This obtained surface final spinel is incurred.

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The key to the synthesis of the subject spinels is in the at elevated temperature, as practiced in a rotary evapo use of an organic, saturated, aliphatic, alpha-hydroxy rator, or in a vacuum drying oven.

carboxylic acid to form a complex salt, which is soluble The resulting material from the evaporation step is an in the aforementioned aqueous medium, at a pH on the amorphous residue, generally being a powder. This acidic side, i.e., pH of 5-7. The solubility of the iron and residue is heated at elevated temperature at 100 to 600 cobalt organic salts of the alpha-hydroxy carboxylic C. for about 1 to 24 hours in generally air to result in a acid prevent crystallization from occurring, resulting in substantially single spinel phase which is isostructural a crystalline product being obtained from the solution, with Fe3O4, as determined by X-ray diffractometry, as which would possess a relatively low surface area. previously described herein. Preferred temperature The subject method utilizes an alpha-hydroxy ali O range is 100-400° C., and particularly preferred is phatic carboxylic acid which acts as a solubilizing agent about 350° C. for single phase spinel formation. for the iron and cobalt salts in the aqueous solution. Any A further subject of the instant invention is a compo Saturated aliphatic alpha-hydroxy carboxylic acid, con sition of matter being a reduced iron-cobalt metallic taining at least one alpha-hydroxy grouping, can be alloy formed form the spinel described above, said alloy used to form the soluble iron and cobalt salts in the 15 being isostructural with alpha-iron, as determined by subject invention process in mildly basic aqueous solu X-ray diffractometry, and preferably possessing a BET tion, is deemed to be included within the scope of this invention. Representative examples of such acids which surface area of about 5 m2/g or higher. Generally preferred is where the surface area is about can be mono-hydroxy or di-hydroxy or mono-carboxy 5-10 m2/g and lic or di-carboxylic are glycolic, malic, glyceric, man The atomic ratioparticularly

preferred being 6-8 m2/g.

of iron to cobalt is not restricted and delic, tartaric, lactic acids and mixtures thereof. A pre can be 4:1 and above. Generally, however, for C2-C20 ferred carboxylic acid used in the process is glycolic olefin synthesis in the subject process described herein, acid. the iron-cobalt atomic ratio is preferably about 4 to 1 The amount of acid used is at least the stoichiometric amount, i.e., 1 to 1 molar ratio for each metal present to 25 and above and more preferably being about 7 to 1 to 35 and preferably in about a 5-10% molar excess of the to 11.and a particularly preferred range is of about 19:20 Stoichiometric amount. Higher ratios can be used, if it is The iron-cobalt alloy can be produced by reducing economical to do so. Lower amounts can also be used the but would result in incomplete iron and cobalt acid salt atmosphere above-described iron-cobalt spinel in a reducing formation. 30 at elevated temperature generally of about The first step in the process comprises forming an 240° C. and above and preferably 300 to 400° C. The aqueous solution by dissolving iron salts and cobalt gases reduction can be carried out with various reducing salts, in a water-soluble salt form such as their nitrates, including hydrogen, H2/CO, and the like, and sulfates, chlorides, acetates, and the like, in water. mixtures thereof. Preferably hydrogen gas alone is gen erally used in an inert carrier medium such as helium,

The concentration of the salts in the aqueous liquid is 35 neon, argon, or nitrogen, in the absence of CO when not critical to the extent that the salts are present in less substantially than a saturated solution to avoid precipitation. For pure, non-carbided alloy is desired. example, an 80-90% saturated solution, of combined in The alloy can be prepared ex situ in a tube reactor or situ in the Fischer-Tropsch slurry process. The in situ dissolved metal molarities for avoiding precipitation in preparation is conducted in the slurry apparatus when the process, can be effectively used. 40

The temperature of the aqueous solution is not criti in the above described spinel is reduced while suspended cal and may be above room temperature to aid in the the slurry liquid, in a reducing atmosphere being Solubilizing process. However, room temperature is preferably a hydrogen atmosphere at elevated tempera adequate and is the temperature generally used in the ture being about 240° C., or above, preferably at process. The pressure also is not critical in the process 45 240-300 C., at a space velocity, pressure, and hydro and atmospheric pressure is generally used. gen concentration sufficient to cause substantial reduc The aqueous solution can also contain a small amount tion of the spinel to the alloy. Substantial reduction is of organic solvent such as ethanol, acetone, and the like complete when the X-ray diffraction pattern shows a for aiding in the solubilizing of the iron and cobalt salts pattern substantially isostructural with alpha-iron. of the alpha-hydroxy carboxylic acid. 50 The above-described alloy is useful in forming a carb Following the dissolving of the iron and cobalt salts, ided iron-cobalt catalyst useful in the subject Fischer the alpha-hydroxy carboxylic acid is added, together Tropsch slurry process for making C2-C20 olefins, as with a sufficient quantity of base, usually being ammo described herein, nium hydroxide, sodium hydroxide, potassium hydrox Also, subjects of the instant invention are composi ide, and the like, preferably ammonium hydroxide, to 55 tions of matter being reduced and carbided iron-cobalt solubilizing the resulting acid salts. The amount of base alloys, one being isostructural with FesC2, "Hagg car added is sufficient to keep the pH in the range of about bide” as described in Trans, of the Iron & Steel Inst. of 5 to 7.0. Japan, Vol. 8, p. 265 (1968) by Nagakura et al., as deter It should be noted that the exact sequence of steps mined by X-ray diffractometry and possessing a BET need not be adhered to as described above, with the 60 surface area of greater than 5 m2/g; and two, being proviso that the resulting aqueous solution contain dis isostructural with Fe3C "cementite", as determined by solved iron and cobalt salts in stoichiometric amounts as X-ray diffractometry, and possessing a BET surface iron and cobalt salts of alpha-hydroxy carboxylic acid area of greater than 5 m2/g.

in solution. If there are any insoluble materials present Preferred is where the surface area of either material after addition of the base and organic acid, they should 65 is about 25-200 m2/g and particularly being preferred be filtered prior to the evaporation step. of about 60-150 m2/g, including both the formed Fe-Co At this point, the resulting solution is evaporated, as carbide and surface carbon formed during the carbiding for example, by air drying, or under reduced pressure, step.

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The atomic ratio of the iron:cobalt is not restricted forced through the catalyst slurry allowing good for either composition but generally for use in the sub contact between the CO/hydrogen and the catalyst to ject process for producing C2-C20 olefins is 4:1 or above initiate and maintain the hydrocarbon synthesis process. and preferably 7:1 to 35:1 and particularly preferred in Advantages of a slurry process over that of a fixed the range of about 19-20:1. bed process are that there is better control of the exo The carbided iron-cobalt alloy, having an X-ray dif thermic heat produced in the Fischer-Tropsch process fraction pattern isostructural with FesC2, can be pro during the reaction and that better control over catalyst duced by carbiding the iron-cobalt alloy, described activity maintainance by allowing continuous recycle, hereinabove, in a suitable carbiding atmosphere at ele recovery, and rejuvenation procedures to be imple vated temperature of up to about 400 C. Temperatures 10 mented. The slurry process can be operated in a batch above 500' lead to formation of Fe-Co carbides which or in a continuous cycle, and in the continuous cycle, are isostructural with Fe3C, cementite. the entire slurry can be circulated in the system allow Carbiding atmospheres which can be used to produce ing for better control of the primary products residence the subject reduced, carbided, catalyst include CO, time in the reaction zone. CO/hydrogen, aliphatic hydrocarbons, aromatic hy 15 The subject process can use any of the above drocarbons, and the like. A preferred carbiding atmo described materials, as catalyst or catalyst precursors: sphere is CO/hydrogen. When using CO/hydrogen the iron-cobalt spinel isostructural with Fe3O4; the iron carbiding atmosphere, mixtures of CO/hydrogen can be cobalt alloy isostructural with alpha-iron; or, the re used in a 1:10 to 10:1 molar volume ratio. A preferred duced, carbided, iron-cobalt alloy which is isostructural ratio used for carbiding purposes is a 1:1 molar ratio. 20 with FesC2, or Fe3C. All the materials must have a The carbiding step is generally conducted at a tem BET surface area of greater than 5 m2/g, to be applica perature of about 250 C., or above and preferably at ble in the efficient claimed slurry process described 300 to 400° C. A preferred method of carbiding the herein. These materials can also be made independently alloy is in situ in the slurry liquid to be used in the Fisch of the apparatus prior to use or can be made in situ in the er-Tropsch process. A particularly preferred method is 25 apparatus during the carrying out of the process. A where the spinel is treated with a mixture of CO/hydro preferred procedure is where the spinel, in high surface gen and reduced and carbided in situ in one step prior to area form is pretreated in situ in the slurry liquid, in hydrocarbon synthesis. The pressure is generally about either distinct reduction-carbiding steps or in one re 1 atmosphere, and a space velocity of about 20-20,000 duction-carbiding step as with CO/hydrogen at ele v/v/hr is chosen in order to completely carbide the 30 wated temperature. A full discussion of each of the ma starting iron-cobalt oxide which can be determined by terials, their properties and their preparation are given X-ray diffractometry when the material becomes isos hereinabove and need not be reiterated. tructural with Haag carbide, FesC2. The Haag-type The slurry liquid used in the process is a liquid at the Fe-Co carbides produced in this process are of the gen reaction temperature, must be chemically inert under eral formula: Fes-(5/3),CO(5/3),C2, and also include sur 35 the reaction conditions and must be a relatively good face carbon produced during the carbiding process. solvent for CO/hydrogen and possess good slurrying Carbiding temperatures above 500° C. and preferably and dispersing properties for the finely divided catalyst. 500-700 C., lead to formation of a mixed Fe-Co car Representative classes of organic liquids which can be bide of the general formula Fe3-yCoC, which is gener utilized are high boiling paraffins, aromatic hydrocar ally formed under ex situ procedures which allow the 40 bons, ethers, amines, or mixtures thereof. The high use of higher temperatures than possible in the in situ boiling paraffins include Co-C50 linear or branched slurry process. paraffinic hydrocarbons; the aromatic hydrocarbons The resulting carbide is an active slurry catalyst for include C2-C20 single ring and multi- and fused ring producing C2-C20 olefins in the described Fischer aromatic hydrocarbons; the ethers include aromatic Tropsch slurry process. 45 ethers and substituted aromatic ethers where the ether Also, the above-described alloy and carbide, can be oxygen is sterically hindered from being hydrogenated; prepared independently of the slurry apparatus and may the amines include long chain amines which can be be pyrophoric and inconvenient to handle. In that case, primary, secondary, and tertiary amines, wherein pri the material may be passivated by contact with oxygen mary amines preferably contain at least a C12 alkyl for a sufficient time to reduce or eliminate the pyro group in length, secondary amines preferably contain at phoric tendency. Generally, the oxygen used in the least two alkyl groups being C7 or greater in length, and passivating process is used in an inert gas stream carrier tertiary amines preferably contain at least three alkyl such as helium for a sufficient time to cause passivation. groups being C6 or higher in length. The slurry liquid Generally, this is conducted preferably at room temper can contain N and O in the molecular structure but not ature, at a pressure and space velocity which are conve 55 S, P, As or Sb, since these are poisons in the slurry nient and easy to control and to maximize the efficiency process. Representative examples of specific liquid of the process needed for complete passivation. slurry solvents useful are dodecane, tetradecane, hexa Also, a subject of the instant invention is a Fischer decane, octadecane, cosane, tetracosane, octacosane, Tropsch process for producing C2-C20 olefins by utiliz dotriacontane, hexatriacontane, tetracontane, tetratet ing the iron-cobalt spinel, iron-cobalt alloy and the 60 racontane, toluene, o-, m-, and p-xylene, mesitylene, reduced, carbided, iron-cobalt spinel catalyst described C1-C12 mono- and multi-alkyl substituted benzenes, hereinabove. dodecylbenzene, naphthalene, anthracene, biphenyl, Although a fixed bed process can be used, a preferred diphenylether, dodecylamine, dinonylamine, trioctyla process mode for operating the Fischer-Tropsch pro mine, and the like. Preferred liquid hydrocarbon slurry cess utilizing the catalysts described herein is a slurry 65 solvent is octacosane or hexadecane. type process wherein the catalyst in fine particle size The amount of catalyst used in the liquid hydrocar and high surface area being above 5 m2/g is suspended bon slurry solvent is generally about 10 to 60 g. of dry in a liquid hydrocarbon and the CO/hydrogen mixture catalyst per 500 g. slurry liquid. Preferably about 30 to

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50 g. dry catalyst per 500 g. slurry liquid slurry is uti The percent CO conversion obtainable in the subject lized, being in about a respective 5:1 to 10:1 weight process, while providing substantial quantities of ratio. C2-C20 olefins, ranges from about 30 to 80 percent and The slurry system, comprised of the slurry liquid and usually about 50 to 60 percent for sufficient C2-C20 finally divided catalyst, is generally stirred to promote 5 olefin production.

good dispersion during the pretreatment in the process “Total hydrocarbons' produced in the process is to avoid catalyst settling and to eliminate mass transport related to the selectivity of percent CO conversion to limitations between the gas and liquid phases. In a typi hydrocarbons being those hydrocarbons from C1 to cal laboratory unit the rate of stirring is generally car about C40 inclusive. Total hydrocarbon selectivity is ried out in the range of about 600 to 1,200 rpm and 10 generally 0 to 50 percent and higher, of the total CO preferably 1,000 to 1,200 rpm. converted, and the remainder converted to CO2. Prior to the CO/hydrogen hydrocarbon synthesis The percent C2-C20 hydrocarbons of the total hydro run, the reduced and carbided iron-cobalt catalyst is carbons produced including methane and above is about generally conditioned in the apparatus by purging with 15 60 to 90 wt.%. The percent of C2-C20 olefins produced, nitrogen to remove reactive oxygen-containing gases of the C2-C20 total hydrocarbons produced is about 60 and then the temperature is increased while stirring to to 70 wt.%. The olefins produced in the process are the reaction temperature range. Then the System is substantially alpha olefins.

generally subjected to a hydrogen treatment for a suffi The selectivity to methane based on the amount of cient time to insure complete removal of any surface 20 CO conversion is about 1 to 10 weight percent of total metal oxide present which would interfere in hydrocar hydrocarbons, produced. Preferably about 5 percent, bon synthesis. and lower, methane is produced in the process. Optionally, and preferably if the catalyst is prepared As discussed above, the percent selectivity to CO2 in situ, then the hydrogen, treatment is generally not formation in the process is about 10 to 50 percent of CO required or is only practiced for a short period of time. converted.

The pressure and space velocity during the inert gas 25 Preferably, the reaction process variables are ad hydrogen conditioning step are not critical and can be justed to minimize CO2 production, minimize methane utilized in the range which is actually used during actual production, maximize percent CO conversion, and max hydrocarbon synthesis. imize percent C2-C20 olefin selectivity, while achieving Following the conditioning step, the CO/hydrogen 30 activity maintenance in the catalyst system. feedstream is introduced into the slurry catalyst cham Generally, this format can be derived in a preferred ber and the pressure, space velocity, temperature, and mode of operating the process where the slurry liquid hydrogen/CO molar ratio is then adjusted, as desired, used is hexadecane, the catalyst used is Fe2.85Co0 for hydrocarbon synthesis conditions. 15O4/1% K as K2CO3, the catalyst/liquid weight ratio In the process, the hydrogen and CO are used in a 35 is 40/500, the system is stirred at 1,200 rpm, and pre molar ratio in the gaseous feedstream in about a 10:1 to treatment procedure is conducted in situ in a one step 1:10 molar ratio, preferably 3:1 to 0.5:1, and particularly procedure using 9:1 H2/N2 at 220° C., atmospheric preferred 1:1 to 2:1 molar ratio.

The temperature in the process is generally in the pressure, 1200 v/v/hr. space velocity, for a period of 5 range of about 200 to 300° C., preferably being 230 to 40 molar ratiotheis 1:1, hrs., and process conducted at the hydrogen:CO the temperature is conducted at about 270° C., and particularly preferred of about 240-260

C. Higher temperature ranges can also be used but tend 245 C., at a pressure of 7-150 psig, and space velocity to lead to lighter products and more methane, lower 1,000-1200 v/v/hr. By carrying out the above process temperature ranges can also be used but tend to lead to innance the stated variable ranges efficient activity mainte and production of C2-C20 olefins can be lower activity and wax formation. 45

The pressure useful in the process is generally con achieved. The effluent gases in the process exiting from the ducted in the range of about 50 to 400 psig and prefera bly about 70 to 225 psig. Higher pressures can also be reactor may be recycled if desired to the reactor for used but tend to lead to waxy materials particularly in further CO hydrocarbon synthesis. Methods for collecting the products in the process combination with lower temperature. 50

The space velocity used in the process is generally are known in the art and include fractional distillation, about 100 to 4,000 volumes of gaseous feedstream/per and the like. Methods for analyzing the product liquid volume of dry catalyst in the slurry/per hour and is the hydrocarbons and gaseous streams are also known in art and generally include gas chromatography, liq preferably in the range of about 400 to 1,200 V/v/hr, uid chromatography, and particularly preferred of 800-1,200 v/v/hr. Higher 55 high pressure liquid chromatogra space velocities can also be used but tend to lead to phy and the like.

lower % CO conversion, and lower space velocities can Apparatus useful in the preferred process is any con also be used but tend to lead to more paraffinic prod ventional slurry-type reactor, being horizontal or verti CS. cal, being statitionary or cyclical, in catalyst slurry. Generally, after the pretreatment, the CO/hydrogen 60 Other apparatus not specifically described herein will feedstream is introduced to initiate and maintain hydro be obvious to one skilled in the art from a reading of this carbon synthesis. By the use of the above-described disclosure.

catalysts in the system, the activity mainenance is very EXAMPLES good and on a laboratory scale, e.g., 500 cc of slurry containing 50 g of catalyst described herein, 30 days of 65 The following Examples are illustrative of the best continuous run have been observed without significant mode of carrying out the invention as contemplated by decline in percent CO conversion activity while main us and should not be construed as being limitations on taining good C2-C20 olefin synthesis activity. the scope and spirit of the instant invention.

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Unless otherwise indicated, the selectivity weight EXAMPLE 2 percentages of product hydrocarbons is given on a

CO2-free basis. Into a slurry reactor, being a 300 cc Parr CSTR (con It should be further noted that the data in Example 8 tinuous stirred tank reactor) was charged: 50 g of octa was obtained utilizing a large scale slurry apparatus and cosane and 5.0 of the high surface area spinel, described the data was analyzed for alcohols content as reported. above in Example 1. The system was purged with nitro The previous examples did not analyze for or report an gen and then H2 while the temperature was increased alcohols content and it is reasonably believed to be from room temperature to 220 C., where the system below 15% of total products in the small scale appara was maintained under these conditions in a hydrogen tuS. O atmosphere with stirring for a one-hr period at 600 rpm.

EXAMPLE 1. The system was then placed under CO hydrogenation reaction conditions by adjusting the reaction tempera

Preparation of Fe2.85Co0.15O4 Spinel ture to 270° C., the H2/CO volume ratio to 1:1, the 198.04 grams of ferric nitrate in 144 cc of water and 15 space velocity to 1200 V gaseous feedstream/V dry 7.5 grams of cobalt nitrate in 8 cc of water were mixed catalyst/hr, the pressure to 70 psig, and the slurry stir together. To this solution was added a solution of 41.6 rer speed to 600 rpm in the octacosane solvent. The grams of 85% glycolic acid containing 45 cc of ammo effluent gas from the reactor was monitored by an HP nium hydroxide such that the resulting pH of the ammo 5840A Refinery Gas Analyzer to determine percent CO nium glycolate solution was about 6.5. The ammonium conversion and the nature of the hydrocarbon products. glycolate solution constituted 0.51 moles of glycolic The results are listed below in Table I under the high acid such that about a one to one molar ratio of total surface area spinels as "oxide'. metals including iron and cobalt to glycolic acid re Further runs were made based on the spinel which sulted. The ammonium glycolate solution was added to was (1) reduced ex situ, and (2) reduced/carbided ex the aqueous solution containing iron and cobalt salts 25 situ, prior to being charged into the slurry liquid. The and the contents stirred. The resulting solution was results are listed below in the Table as "reduced' and allowed to evaporate by air drying. Upon drying at "reduced/carburized', respectively, together with the room temperature the resulting solid was shown by specific pretreatment condititons. The control, and the X-ray diffraction to be an amorphous material because low surface area spinel also run under substantially the of lack of sharp discrete reflections. The solid was same conditions, are listed below.

heated in air at 350° C. for 2 hours. An X-ray diffraction The listed comparative sample, Fe2O3, was obtained pattern of the resulting material showed it to be a single from Alpha Chemicals and had a BET surface area of phase cobalt-iron spinel isomorphous with Fe3O4. The less than 10 m2/g.

X-ray diffraction peaks were broadened relative to a The listed comparative sample Fe2.85Co0.15O4/1% K compositionally equivalent material obtained by a high 35 was made by sintering an intimate mixture of Fe2O3, Fe temperature procedure. This indicated that the resulting metal and Co3O4, in the appropriate molar ratio, at obtained material was of very small particle size. The 800-1,000 C. for 24 hours in an evacuated sealed tube. surface area of the resulting material was about 200 The solid was collected, crushed, pelletized and then square meters per gram. Carbon analysis of the material the sintering procedure repeated. The obtained solid indicated approximately 0.15% carbon percent. The 40 was crushed and then impregnated with aqueous potas resulting material was impregnated with one gram sium carbonate and then dried at 125 C. for several atomic percent of potassium using an aqueous solution hours in a drying oven. The surface area of the obtained of potassium carbonate and drying of the resulting im solid was about 0.3 m2/g.

pregnated sample at 125 C. The resulting solid had an TABLE I empirical formula of Fe2.85Co0.15O4/1% K. 45

Slurried F-T Catalysts with 1:1 H2:CO

Preparation of Alloy % The above obtained oxide was reduced at 400 C. in % CO % Olefin a stream of 15 volume percent hydrogen/85% helium at Catalysts Conv. 2 CO2 % CH4 C2-C3 C2-C4 200 v/v/hr (SHSV) for 4 hours. One percent of oxygen 50 Fe2O3 <4.0 - --- - --

in helium was introduced at room temperature for one Fe2.85

hour to passivate the material. The X-ray of the result Spinels (100 + m/g) ing material was isostructural with alpha iron. The re Fe2.85 Co0.15O4 sulting BET nitrogen surface area was 8 m2/g. Oxide 78 48 3.1 7.3 92 55 Reduced 55 62 2.2 10.9 88

Preparation of Carbide Reduced/Carburized' 79 48 4.5 6.0 92 The above reduced material was treated at 400° C. in Conditions:

a stream of 15 volume percent hydrogen/80% heli 270° C., l: H:CO. 1200 v?v/cat/hr. 70 psig, 600 rpm, octacosane solvent.

um/5% CO at 200 v/v/hr. for four hours. Following H/CO at 350° C. for 12 hours and 400° C. for 24 hours. this the sample was cooled to room temperature and 60 10% oxygen in helium was introduced for one hour to As is seen in this example, catalysts prepared from the passivate the material. The X-ray diffraction pattern of high surface area spinel gave higher activity and C2-C4 the resulting material was isostructural with FesC2. The olefin selectivity than conventional iron oxide catalysts. BET nitrogen surface area of the material was about EXAMPLE 3 118 m2/g. Analysis showed that about 60-70 weight 65 percent of the material was carbon and thus the material The catalysts, apparatus, catalyst pretreatment and was a composite of Fe4.75Co0.25C2/1 gram-atom 7% K general CO hydrogenation procedures of Example 2 and surface carbon. were used and repeated except that modified CO hydro

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genations conditions were used at 250 C. and 2:1 TABLE IV-continued H2:CO as listed in Table II. Comparative Study of Carburized TABLE II Catalysts from High Surface Area

Slurried F-T Catalysts with 2:1 H2CO - Spinel Precursors -

% CO % Olefin Precursor A(a) B(b) Fe3O4/1% K(c) Catalysts Conv. 2% CO2 % CH4 C2-C4 C2-C4 % CO to HC 28 18 26 Fe2O3 <5.0 20-- 15.-- 14.0 60.0 Wt. % Selectivity *Fe2.85Co. 5O4/ (4.0° NA NA NA NA CH4 3.6 4.1 5.1 1%. K. O CT 4.2 2.8 2.6 Spinels (100 + m2/g) C2' 0.6 1. 1.6 Fe2.85 Co0.15O4 C= 5. 6.0 6.7 Oxide 31 62 4. 18.2 90 Cs" 0.6 0.7 0.8 Reduced 54 63 2.4 11. 89 C4 2.7 3. 3.6 Reduced/Carburized 64 50 3.6 14.0 83 C4" 0.4 0.6 0.8 15 Cs+ 26.6 25.6 18.8

Conditions: CO2 56 56 60 250 C. 2:1 H:CO, 1200 v/v/cat/hr. 70 psig, 600 rpm, octacosane solvent. %. Olefin in 88 83 80

less than 5% conversion observed even at 270' C. C2-C4

'H/co at 350 C. for 12 hours and 400 C. for 24 hours. 'same as A but less than 1 m/g.

Conditions:

EXAMPLE 4 250 C. 1200 V/G CAT/hr, 2: H2:CO, 70 psig, 600 RPM, octacosane, ex situ

Utilizing the catalysts, apparatus, catalyst pretreat ment and general CO/hydrogenation procedures de As seen, catalysts generated from Fe-Co and Fespi scribed in Example 2, the following runs were made 25 nel precursors which are fully reduced and carbided ex utilizing the specific process conditions listed in Table situ, exhibited comparable activity under CO hydroge

III below: nation conditions. However, the Fe-Co based system

TABLE III generated less unwanted CH4 and CO2 and a C2-C4

Comparative Study of fraction which is richer in alpha-olefins when compared 30 to the Fe only analog.

Fe-Co Catalysts from High and Low Surface Spinel Precursors Comparison of Fe-Co catalysts from high and low

Spinel Initial Fe2.85Co. isO4/1% K surface area spinel precursors, Runs A and B, indicates Surface Area 100+ m2/g < 10 m/g that the high surface precursor generated higher yields % CO Conversion 45 44 of alpha-olefins and lower methane than the low surface 35 area precursor when both catalysts are prereduced/- % CO to CO2 - -

Wt % Selectivity

carbided ex situ. Similar results were noted in previous

CH4 1.9 2.0

Example 4.

C2-C4 8.3 8.4 EXAMPLE 6 C5-- 32.3 23.6

CO2 57.0 66.0 Utilizing the spinel catalysts, apparatus, and general % Olefin in C-C4 90 90 CO hydrogenation conditions described in Example 2, Conditions:

250 C., 1200 vag CAT/hr, 1: H:CO. 70 psig, 600 RPM, octacosane solvent.

the following runs were carried out utilizing the specific

Catalysts subjected to ex situ H2 treatment at 300-- C. followed by ex situ H2/CO in situ pretreatment and hydrocarbon synthesis process treatment 360-- C. to affect complete reduction-carburization followed by oxygen conditions listed below in Table V: passivation.

TABLE V

The results in Table III indicate that catalysts pre Comparative Study of High Surface pared from low and high surface area Fe-Co spinels Area Oxide Catalysts provide comparable performance when they are both Catalyst Fe2.85Co.15O4/1% K Fe3O4/1% K fully prereduced and carburized ex situ. The catalyst 50 Surface Area 100- m/g 00-- m/g derived from the low surface area precursor generated % CO Conversion 60 8 more CO2 and less C5 -- hydrocarbon than the catalyst %% CO to CO2

generated from the high surface area precursor, under Wt % Selectivity the stated reaction conditions. CH4 1.8 4.0 55 C2-C4 8.0 5

EXAMPLE 5 Cs-- 30.2

Utilizing the catalysts, apparatus, pretreatment and CO2 60,0 65 general CO hydrogenation procedures described in % Olefin in C2-C4 88 80 Example 2, the following runs were made under the Conditions:

250 C. 1200 V/G CAT/hr, 2:1 H:CO, 70 psig, 600 RPM octacosane. Catalyst specific process conditions listed below in Table IV: 60 charged to reactor as oxide, treated in situ with H2 at 100 psig at 200 C. for 1 hr before use.

TABLE IV

Comparative Study of Carburized As is seen, catalysts derived from high surface area Catalysts from High Surface Area

Spine Precursors spinels, with and without added cobalt, exhibited sub

Catalyst 65 stantially different activities when employed and pre Precursor A(a) B(b) Fe3O4/1% K(c) treated in situ directly under slurry reactor conditions. % CO Conversion 64 42 65 The Fe-Co catalyst is ca. 5-fold more active than the Fe % CO to CO2 36 24 39 only catalyst. The Fe-Co catalyst also generated less

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CH4 and CO2 than the Fe only catalyst and generates a of contacting a catalyst composition, comprised of an C2-C4 fraction which is richer in alpha-olefins. unsupported iron-cobalt spinel, said spinel exhibiting a EXAMPLE 7 single phase being isostructural with Fe3O4 as deter mined by powder X-ray diffractometry, and possessing

Utilizing the catalysts, apparatus, pretreatment and 5 an initial BET surface area greater than 5 m2/g and an general CO hydrogenation procedures, described in Fe:Coatomic ratio of 7:1 and above, with a mixture of

Example 2, the following runs were made using the CO and hydrogen under conditions of pressure, space specific conditions listed below in Table VI including velocity, and elevated temperature, for a time sufficient comparative runs made at H2/CO ratios of 1.0 and 2.0. to produce said C2-C20 olefins.

2. The process of claim 1 wherein said slurry liquid is

TABLE VI selected from high boiling liquid paraffins, aromatic

Performance of Fe and Fe-Co hydrocarbons, ethers, amines, or mixtures thereof.

Alloy Catalysts 3. The process of claim 2 wherein said high boiling

Precursor Fe3O4/1% KC) Fe2.85Co.s04/1% K() liquid paraffins are C12-C60 linear or branched saturated 15 aliphatic hydrocarbons.

H2/CO 1.0 2.0 O 2.0 4. The process of claim 3 wherein said hydrocarbon % CO to CO2 26 5 34 34 slurry liquid is selected from Octacosane, hexadecane, % CO to HC 18 3 21 20

or mixtures thereof.

CH4 18 1.0 2.2 2.4 5. The process of claim 1 wherein said hydrogen and 20 CO are present in a hydrogen/CO molar ratio of 1:10 to

C2-C4 11.1 5.0 10.9 11.

Cs+ 28. 41.0 24.8 23.5 10:1.

CO2 59 53 62 63 % Olefinin 93 94 88 9. 6. The process of claim 1 wherein said temperature is C2-C4 in the range of about 200 to 300° C. Conditions: 7. The process of claim 1 wherein said pressure is in 270° C., 1:1 H:CO, 1200 wav Catahr., 70 psig, 600 rpm. Catalyst prereduced ex situ 25 the range of about 50 to 250 psig. in H2 at 350° C. for 12 hours and 400 C. for 24 hours. 8. The process of claim 2 wherein said space velocity Initial spinel surface area - about 100 m/g.

Initial spinel surface area - about 100 m/g. is in the range of about 100 to 4000 v/v/hr. 9. The process of claim 1 wherein the weight ratio of

EXAMPLE 8 30 slurry liquid: dry catalyst is in the range of about 10:1 to

Utilizing the pretreatment and general CO hydroge 10. The process of claim 1 wherein said spinel is re nation procedures described in Example 2, the follow duced and carbided in situ in the process in the slurry ing runs were made utilizing the specific catalyst and liquid.

CO hydrogenation conditions described below. 11. The process of claim 1 wherein the catalyst is The spinel described in Example 2, Fe2.85Co0 35 reduced and carbided ex situ.

15O4/1% K, was reduced and carbided ex situ similar to 12. The process of claim 1 wherein said carbided the procedure described in Example 2. A hydrogen/- reduced spinel is isostructural with FesC2, or Fe3C, as CO/helium feedstrean in 1:1:7 molar ratio at 350 C. determined by powder X-ray diffractometry. and about 300 v/v/hr. for 24 hours was used. Powder x-ray diffraction analysis revealed the resulting material cobalt ratio is 7:1 toof35:1. 13. The process claim 1 wherein said atomic iron was isostructural with Hagg Carbide, FesC2. The ele 14. The process of claim 13 wherein said iron-cobalt mental analysis of the material showed it to contain: Fe atomic ratio is 19-20:l. and Co in about a 19:1 atomic ratio and about 60-70 weight percent carbon. The surface area of the material 45 initial 15. The process of claim 1 wherein said spinel has an was determined to be about 180-200 m2/g. BET surface area of about 50 m2/g or above. The catalyst (40 cc. catalyst volume) was run under 16. The process of claim 15 wherein said spinel has a two different pressures in CO hydrogenation under the BET surface area of about 70 to 220 m2/g. 17. The process of claim 1 wherein said catalyst com conditions listed below in Table VII.

The apparatus used was a 1 liter stirred tank reactor 50 about position further comprises a promoter agent present in (316 S.S.) equipped with a Magnedrive TM head and an atoms 0.1 to 10 gram-atom percent of said total gram of metals content.

internal gas recycle. 18. The process of claim 17 wherein said promoter TABLE VII agent is selected from the group of carbonate, bicarbon

Fe.75CO25C2/1% K ate, organic acid saits, inorganic acid salts, nitrate, hal % CO Conversion 24 53 55 ide, sulfate, and hydroxide salts of Group IA and IIA % CO to CO2 1 23 metals.

% CO to HC 13 30 19. The process of claim 18 wherein said promoter

Wt. % Selectivity agent is potassium carbonate.

CH4 4.9 4.7 20. The process of claim 1 wherein said spinel catalyst C2m-C20- 59.3 53.2 60 composition is Fe2.85Co0.15O4 with 1 gram-atom 2% Kas C-Clo Alcohols

potassium carbonate.

C2- trace 10.6 21. The process of claim 1 wherein said product hy Conditions: drocarbon mixture contains 60 wt % C2-C20 olefins. 240 C., i:1 H2/CO, 1,000 vavahr. 1.200 RPM, 100-150 hr. on stream. 22. The process of claim 1 wherein said hydrocarbon 65 mixture contains C2/C20 paraffins and olefins in an ole

What is claimed is: fins/paraffins weight ratio of 3:1. 1. A slurry process for synthesizing a hydrocarbon 23. A slurry process for synthesizing a hydrocarbon mixture containing C2-C20 olefins comprising the step mixture containing C2-C20 olefins comprising the step

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of contacting a slurry comprising an unsupported iron- greater than 5 m2/g, said spinel being reduced and carb cobalt spinel composition of the formula: Fe2.85Co0- ided ex situ, with a 1:1 H2/CO mixture at 75-150 psig, 15O4/1% K, exhibiting a single phase being isostruc- 1000 SHSV and 240° C., for a time sufficient to product tural with Fe3O4 as determined by powder X-ray dif- said olefins.

fractometry and possessing an initial BET surface area 5 ck : 3 x 3.