Cobalt metal foam catalyst, method of making same, thermal-medium-circulating heat-exchange reactor using same, and method of producing a liquid fuel by means of a Fischer-Tropsch synthesis reaction using thermal-medium-circulating heat-exchange reactor

Abstract

A method of producing liquid fuel by a Fischer-Tropsch synthesis reaction using a thermal medium-circulated heat exchanger type reactor is provided. The thermal medium-circulated heat exchanger type reactor uses the cobalt metal foam catalyst including a metal foam coated with cobalt catalyst powder is used. Exothermic reaction heat generated by the Fischer-Tropsch synthesis reaction occurring in the cobalt metal foam catalyst layer of the tube unit is controlled by thermal medium oil circulating in the shell unit at a reaction temperature of 190250 C. and a reaction pressure of 2025 atm, and simultaneously the reaction is conducted, thus producing liquid fuel.

Claims

1. A method of producing liquid fuel by a Fischer-Tropsch synthesis reaction using a thermal medium-circulated heat exchanger type reactor, comprising: preparing a tube unit comprising an outer heat exchange surface having a circumference and a shell unit that fully surrounds the circumference of the outer heat exchange surface of the tube unit to form a space between the tube unit and the shell unit; disposing a cobalt metal-foam catalyst layer inside the tube unit; supplying a synthesis gas into an upper portion of the tube unit through a synthesis gas supply line; heating the cobalt metal-foam catalyst layer to bring about a Fischer-Tropsch synthesis reaction inside the tube unit, using an electric heater provided at the circumference of the shell unit, to thereby produce a liquid fuel product from the synthesis gas; supplying a thermal medium oil having a predetermined temperature into a lower portion of the space through a thermal medium oil supply line; recovering the thermal medium oil from an upper portion of the space through a thermal medium oil recovery line; heat-exchanging between the tube unit and the thermal medium oil using a heat exchange pin protruding from an outer surface of the tube unit, thereby controlling heat generated by the Fischer-Tropsch synthesis reaction; recovering the liquid fuel product through a lower portion of the tube unit, wherein the metal-foam of the cobalt metal-foam catalyst layer comprises any one of iron-chromium-aluminum alloy, nickel-chromium alloy, copper-nickel alloy, aluminum-copper alloy, zinc-copper alloy, or silver-copper alloy, and the metal-foam was pre-treated by atomic layer deposition to form an Al.sub.2O.sub.3 thin film on the surface of the metal-foam.

2. The method of producing liquid fuel according to claim 1, further comprising: controlling the predetermined temperature using a heat exchanger provided on the thermal medium oil supply line.

3. The method of producing liquid fuel according to claim 2, wherein the predetermined temperature is adjusted to 190250 C.

4. The method of producing liquid fuel according to claim 1, wherein the cobalt metal-foam catalyst layer is heated to 300500 C.

5. A method of producing liquid fuel by a Fischer-Tropsch synthesis reaction using a thermal medium-circulated heat exchanger type reactor, comprising: preparing a tube unit comprising an outer heat exchange surface having a circumference and a shell unit that fully surrounds the circumference of the outer heat exchange surface of the tube unit to form a space between the tube unit and the shell unit; disposing a cobalt metal-foam catalyst layer inside the tube unit, wherein the cobalt metal-foam catalyst layer is heated to 300500 C.; supplying a synthesis gas into an upper portion of the tube unit through a synthesis gas supply line; heating the cobalt metal-foam catalyst layer to bring about a Fischer-Tropsch synthesis reaction inside the tube unit, using an electric heater provided at the circumference of the shell unit, to thereby produce a liquid fuel product from the synthesis gas; supplying a thermal medium oil having a predetermined temperature into a lower portion of the space through a thermal medium oil supply line; controlling the predetermined temperature using a heat exchanger provided on the thermal medium oil supply line, wherein the predetermined temperature is adjusted to 190250 C.; recovering the thermal medium oil from an upper portion of the space through a thermal medium oil recovery line; heat-exchanging between the tube unit and the thermal medium oil using a heat exchange pin protruding from an outer surface of the tube unit, thereby controlling heat generated by the Fischer-Tropsch synthesis reaction; recovering the liquid fuel product through a lower portion of the tube unit, and wherein the metal-foam comprises a copper-nickel alloy that was pre-treated by atomic layer deposition to form and Al.sub.2O.sub.3 thin film on the surface of the metal-foam.

6. The method of producing liquid fuel according to claim 1, wherein the metal-foam of the cobalt metal-foam catalyst layer comprises aluminum, iron, iron-chromium-aluminum alloy, nickel-chromium alloy, copper-nickel alloy, aluminum-copper alloy, zinc-copper alloy, or silver-copper alloy.

7. The method of producing liquid fuel according to claim 6, wherein the metal-foam comprises a copper-nickel alloy that was pre-treated by atomic layer deposition to form an Al.sub.2O.sub.3 thin film on the surface of the metal-foam.

Description

DESCRIPTION OF DRAWINGS

(1) FIG. 1 is a photograph showing a cobalt metal foam catalyst in which a metal foam surface-pretreated by ALD is coated with cobalt catalyst powder according to the present invention;

(2) FIG. 2 is a flowchart showing a method of manufacturing the cobalt metal foam catalyst according to the present invention;

(3) FIG. 3 is a schematic view showing a thermal medium-circulated heat exchanger type reactor according to the present invention; and

(4) FIG. 4 is a graph comparing the results of reaction temperatures obtained from the Fischer-Tropsch synthesis reaction using the thermal medium-circulated heat exchanger type reactor filled with the cobalt metal foam catalyst with those obtained from the Fischer-Tropsch synthesis reaction using the conventional fixed-bed reactor filled with a spherical cobalt catalyst.

DESCRIPTION OF THE REFERENCE NUMERALS IN THE DRAWINGS

(5) 1: metal foam 2: cobalt catalyst powder 3: cobalt metal foam catalyst 201: tube unit 202: shell unit 203: electric heater 204: cobalt metal foam catalyst 205: heat exchange pin 206: thermal medium oil storage tank 207: thermal medium oil storage tank heater 208: thermal medium oil circulation pump 209: heat exchanger 210: switching valve 211: hydrogen mass flow controller (MFC) 212: carbon monoxide mass flow controller 213: nitrogen mass flow controller 221: synthesis gas supply line 222: nitrogen supply line 223: air injection unit 224: thermal medium oil recovery unit 231: thermal medium oil 232: thermal medium oil supply line 233: thermal medium oil recovery line 241: cooling water line 251: liquid fuel product recovery unit

DETAILED DESCRIPTION OF THE INVENTION

(6) Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. Further, in the description of the present invention, when it is determined that the detailed description of the related art would obscure the gist of the present invention, the description thereof will be omitted.

(7) FIG. 1 is a photograph showing a cobalt metal foam catalyst 3 in which a metal foam 1 surface-pretreated by ALD is coated with cobalt catalyst powder 2 according to the present invention, and FIG. 2 is a flowchart showing a method of manufacturing the cobalt metal foam catalyst 3 according to the present invention.

(8) As shown in FIGS. 1 and 2, the cobalt metal foam catalyst in which the metal foam surface-pretreated by ALD is coated with the cobalt catalyst powder is manufactured by coating the surface of the metal foam with a slurry composed of a mixture of alumina sol, cobalt catalyst powder and isopropyl alcohol.

(9) Conventionally, a fixed-bed reactor or a slurry reactor using a powdered catalyst or a spherical or pelleted particulate catalyst has been used as a reactor for carrying out a Fischer-Tropsch synthesis reaction. In contrast, when the cobalt metal foam catalyst manufactured by the method of the present invention is used, the reaction heat generated during the Fischer-Tropsch synthesis reaction can be efficiently removed to control the reaction temperature stable because of the metal properties of the metal foam, and liquid fuel, which is a reaction product, is efficiently transferred to the outside of a catalyst layer by the improved mass transfer characteristics because the metal foam is coated with cobalt catalyst powder and so forms a thin film, thereby achieving high liquid fuel productivity even at a low CO conversion ratio.

(10) The method of manufacturing the cobalt metal foam catalyst according to the present invention includes the steps of: surface-pretreating a metal foam by atomic layer deposition (ALD) using trimethylaluminum ((CH.sub.3).sub.3Al) and water to form an Al.sub.2O.sub.3 thin film; preparing a cobalt catalyst slurry composed of a mixture of alumina sol, a cobalt catalyst and isopropyl alcohol; surface-coating the surface-pretreated metal foam with the cobalt catalyst slurry by dip coating; and drying and calcinating the surface-pretreated metal foam coated with the cobalt catalyst slurry.

(11) As the cobalt catalyst, any catalyst may be used as long as it is generally used in Fischer-Tropsch synthesis. Preferably, the cobalt catalyst may be a catalyst prepared by impregnating a support, such as alumina (Al.sub.2O.sub.3), silica (SiO.sub.2), titania (TiO.sub.2) or the like, with a cobalt precursor, such as cobalt nitrate (Co(NO.sub.3).sub.26H.sub.2O), cobalt acetate ((CH.sub.3CO.sub.2).sub.2Co4H.sub.2O) or the like.

(12) The metal foam is made of aluminum, iron, stainless steel, iron-chromium-aluminum alloy (FeCrAl alloy), nickel-chromium alloy, copper-nickel alloy, aluminum-copper alloy, zinc-copper alloy or silver-copper alloy. The metal foam is used to form a stable Al.sub.2O.sub.3 thin film and coat cobalt catalyst powder because it has heat transfer properties and high adhesivity to the surface of the metal foam. Preferably, the metal foam may be made of any one of iron-chromium-aluminum alloy (FeCrAl alloy), nickel-chromium alloy, copper-nickel alloy, aluminum-copper alloy, zinc-copper alloy and silver-copper alloy. Particularly, copper-nickel alloy is most effective at forming the stable initial interlayer that is necessary to form an Al.sub.2O.sub.3 thin film on the surface of the metal foam in the process of surface-pretreating the metal foam.

(13) Atomic layer deposition (ALD) is a process of surface-treating a metal foam to evenly coat the surface of the metal foam with a cobalt catalyst. ALD is a process of forming a compact Al.sub.2O.sub.3 thin film on the surface of the metal foam using trimethylaluminum and water.

(14) The reason for this is that it is difficult to form a stable interface on the surface of the metal foam because the properties of the metal foam are different from those of the catalyst which includes inorganic matter as a main component. Therefore, in order to solve this problem, an interlayer having properties similar to those of a catalyst including inorganic matter as a main component is formed on the surface of the metal foam.

(15) Since the surface of the metal foam is completely covered with an Al.sub.2O.sub.3 thin film by ALD, the surface property of the metal foam is changed to that of Al.sub.2O.sub.3, which is inorganic matter.

(16) That is, the uniform Al.sub.2O.sub.3 thin film that completely covers the surface of the metal foam is not formed by a general coating method, and can be formed only by the ALD of the present invention.

(17) In the present invention, the cobalt catalyst slurry applied onto the surface of the metal foam pretreated by ALD is prepared by mixing alumina sol, cobalt catalyst powder and isopropyl alcohol.

(18) In the composition of the cobalt catalyst slurry, the mixing ratio of a mixed solution of alumina sol and isopropyl alcohol to cobalt catalyst powder may be 10:11:5.

(19) Here, when the mixing ratio of the mixed solution of alumina sol and isopropyl alcohol to cobalt catalyst powder is more than the upper limit, the concentration of the cobalt catalyst slurry is excessively low, so that the adhesivity of the cobalt catalyst slurry is very low, with the result that it is difficult to form a catalyst coating layer on the surface of the metal foam. Further, when the mixing ratio thereof is less than the lower limit, the concentration of the cobalt catalyst slurry is excessively high, so that the thickness of the catalyst coating layer formed on the surface of the metal foam increases, with the result that the amount of catalyst particles which fail to be exposed to the surface of the coating layer increases, thereby increasing the loss of catalyst particles which are active in the Fischer-Tropsch synthesis.

(20) Further, the mixed solution including alumina sol and isopropyl alcohol is prepared by mixing alumina sol including alumina and water with isopropyl alcohol. The mixed solution is configured such that its viscosity is 150 cP. The reason for limiting the numerical value of the viscosity is because it is difficult to suitably apply the cobalt catalyst slurry onto the surface of the metal foam when the viscosity thereof is less than the lower limit or more than the upper limit.

(21) FIG. 3 is a schematic view showing a thermal medium-circulated heat exchanger type reactor according to the present invention.

(22) As shown in FIG. 3, the thermal medium-circulated heat exchanger type reactor according to the present invention is configured such that the problem of pressure drop which occurs during a Fischer-Tropsch synthesis reaction is effectively solved and such that the reaction heat in the Fischer-Tropsch synthesis reaction, which is a strong exothermic reaction, can be efficiently controlled, so that the reaction temperature can be controlled and kept stable and the mass transfer characteristics of a catalyst layer can be improved, thereby producing liquid fuel in a high yield even when the CO conversion ratio is low. Without providing this thermal medium-circulated heat exchanger type reactor, when the Fischer-Tropsch synthesis reaction is carried out, the loss of active catalyst particles charged in a reactor is large, which is inefficient, and the reaction temperature is not easily controlled.

(23) In order to solve such a problem, the thermal medium-circulated heat exchanger type reactor according to the present invention includes: a tube unit 201 configured such that synthesis gas is supplied to a cobalt catalyst layer 204 filled with a plurality of cobalt metal foam catalysts each including a metal foam coated with cobalt catalyst powder to carry out a reaction; a shell unit 202 configured to cover the tube unit 201 such that thermal medium oil having a predetermined temperature is circulated to control the reaction heat generated from the Fischer-Tropsch synthesis reaction; a heat exchange pin 205 protruding from the outer surface of the tube unit 201 to accelerate the heat exchange between the tube unit 201 and the thermal medium oil; an electric heater 203 provided at the circumference of the shell unit 202 to heat a cobalt catalyst layer to reduce and pretreat the cobalt catalyst layer; a thermal medium oil storage tank 206 supplying the thermal medium oil 231 to the lower portion of the shell unit 202 through a thermal medium oil supply line 232 and recovering high-temperature thermal medium oil discharged from the upper portion of the shell unit 201 through a thermal medium oil recovery line 233 and then storing the high-temperature thermal medium oil; a thermal medium oil circulation pump 208 provided along the thermal medium oil supply line 232 to supply the thermal medium oil stored in the thermal medium oil storage tank 206; and a heat exchanger 209 provided along the thermal medium oil supply line 232 located behind the thermal medium oil circulation pump 208 to perform heat exchange between cooling water and thermal medium oil to control reaction temperature.

(24) The thermal medium storage tank 206 is provided at the circumference thereof with a heater 207 to control the temperature of the stored thermal medium oil.

(25) Further, the thermal medium oil supply line 232 is provided with a thermal medium oil recovery unit 224 to control the amount of the thermal medium oil discharged from the thermal medium storage tank 206.

(26) Further, the thermal medium oil recovery line 233 is provided with an air injection unit 223 for injecting air when the circulated thermal medium oil is recovered by the thermal medium oil recovery unit 224 provided in the thermal medium oil supply line 232 and provided with a switching valve 210 that controls the injection of air.

(27) The top of the tube unit 201 is connected to a mixed gas supply line 221 for supplying a mixed gas of hydrogen passing through a hydrogen mass flow controller 211 and carbon monoxide passing through a carbon monoxide mass flow controller 212. Also, the mixed gas supply line 221 is connected to a nitrogen supply line 222 for supplying nitrogen passing through a nitrogen mass flow controller 213. Further, the bottom of the tube unit 201 is connected to a liquid fuel product recovery unit 251 for recovering liquid fuel produced while passing through the cobalt catalyst layer 204 provided in the tube unit 201.

(28) The electric heater 203 for heating the cobalt catalyst layer to reduce and pretreat the cobalt catalyst layer 204 is configured such that the cobalt catalyst layer 204 is heated to 300500 C. When the cobalt catalyst layer is heated to below the lower limit, it is difficult to activate a cobalt catalyst, although the activation of the cobalt catalyst is necessary for carrying out the Fischer-Tropsch synthesis reaction for producing liquid fuel. Further, when the cobalt catalyst layer is heated to above the upper limit, it is difficult to maintain the stability of the cobalt catalyst at high temperature.

(29) The temperature of the thermal medium oil is maintained at 190250 C. When the temperature thereof is below the lower limit, it is difficult to run the Fischer-Tropsch synthesis reaction. Further, when the temperature thereof is above the upper limit, during the Fischer-Tropsch synthesis reaction, undesirable side reactions, such as the formation of an excess amount of gaseous products (CH.sub.4, CO.sub.2, etc.), catalyst coking ascribed to carbon deposition causing catalytic deactivation and the like, frequently occur, compared to the production of liquid fuel.

(30) The above-configured thermal medium-circulated heat exchanger type reactor using the cobalt metal foam catalyst including a metal foam coated with cobalt catalyst powder according to the present invention can effectively and rapidly control the exothermic reaction heat that is generated by the Fischer-Tropsch synthesis reaction occurring in the cobalt metal foam catalyst layer of the tube unit by using the thermal medium oil circulating in the shell unit at a predetermined temperature. Further, the heat exchange pin provided on the outer surface of the tube unit can increase the heat exchange efficiency. Also, the exothermic reaction heat that is recovered by the thermal medium oil of the shell unit is removed by the exchanger controlling the temperature using external cooling water, so that the temperature of the thermal medium oil of the shell unit is maintained constant.

(31) As the result of performing the Fischer-Tropsch synthesis reaction using the cobalt metal foam catalyst of the present invention and the thermal medium-circulated heat exchanger type reactor of the present invention under the conditions of a reaction temperature of 190250 C. and a reaction pressure of 2025 atm, first, the problem of pressure drop in the reaction operation was effectively solved. Further, the reaction heat generated by the Fischer-Tropsch synthesis reaction, which is an extremely exothermic reaction, was efficiently controlled, so that the reaction temperature was kept stable and the mass transfer characteristics in the catalyst layer was improved, thereby obtaining high liquid fuel productivity even at a low CO conversion ratio.

(32) The reason for limiting the numerical value ranges of the reaction temperature and reaction pressure is because the highest production yield was obtained in these numerical value ranges.

(33) FIG. 4 is a graph comparing the results of reaction temperatures obtained from the Fischer-Tropsch synthesis reaction using the thermal medium-circulated heat exchanger type reactor filled with the cobalt metal foam catalyst with those obtained from the Fischer-Tropsch synthesis reaction using the conventional fixed-bed reactor filled with a spherical cobalt catalyst.

(34) As shown in FIG. 4, when the Fischer-Tropsch synthesis reaction was performed using the thermal medium-circulated heat exchanger type reactor filled with the cobalt metal foam catalyst, very stable reaction temperature control results (results according to Example 5) were obtained. In contrast, when the Fischer-Tropsch synthesis reaction was performed using the conventional fixed-bed reactor filled with a spherical cobalt catalyst, irregular reaction temperature control results (results according to Comparative Example 1) were obtained.

(35) As shown in FIG. 4, when the initial reaction temperature of the Fischer-Tropsch synthesis reaction using the thermal medium-circulated heat exchanger type reactor filled with the cobalt metal foam catalyst was set 190250 C., the reaction temperature was maintained constant at the initial reaction temperature even when the Fischer-Tropsch synthesis reaction, which is an extremely exothermic reaction, was ran for a long period of time because the reaction temperature was controlled stable by controlling the reaction heat with high efficiency. Further, in this case, the mass transfer characteristics of the cobalt metal foam catalyst were improved, so that high liquid fuel productivity was obtained even at a low CO conversion ratio (results according to Example 5)

(36) As described above, from the Fischer-Tropsch synthesis reaction using the thermal medium-circulated heat exchanger type reactor filled with the cobalt metal foam catalyst according to the present invention, it can be ascertained that the reaction temperature can be controlled stable by controlling the reaction heat with high efficiency, and the mass transfer characteristics of the cobalt metal foam catalyst can be improved, so that high liquid fuel productivity can be obtained even at a low CO conversion ratio.

(37) Hereinafter, the present invention will be described in more detail with reference to the following Examples and Comparative Example. However, the scope of the present invention is not limited to these Examples.

(38) The CO conversion ratio, liquid fuel yield, liquid fuel productivity and hydrocarbon yield in Example 5 and Comparative Example 1 are defined as follows.
CO conversion=reacted CO moles/supplied CO moles*100=(supplied CO molesunreacted CO moles)/supplied CO moles*100
Liquid fuel yield=produced liquid fuel (gasoline, diesel, wax) moles/supplied CO moles*100
Liquid fuel productivity=liquid fuel produced per hour(gasoline, diesel, wax)/used catalyst
Hydrocarbon yield=produced hydrocarbon (ethane, propane, butane, gasoline, diesel, wax) moles/supplied CO moles*100

Example 1

(39) To pretreat metal foam to be used in catalyst surface coating, in order to form an Al.sub.2O.sub.3 thin film, a metal foam (diameter: 22 mm, thickness: 4 mm) made of an copper-nickel alloy was surface-treated by atomic layer deposition (ALD) using trimethylaluminum (CH.sub.3).sub.3Al) and water. In the first step, trimethylaluminum (TMA) was supplied. The supplied TMA reacts with a hydroxyl group (OH) present on the surface of the metal to form a metal-OAl bond. In the second step, residual TMA and CH.sub.4 (reaction side products) are washed with an inert gas such as nitrogen, argon or the like. In the third step, water is supplied. The unreacted methyl group present on the surface of the metal reacts with the supplied water to form an AlOH bond. In the fourth step, water (unreacted reactant) and CH.sub.4 are removed using inert gas in the same manner as in the second step. While carrying out these four steps, a monolayer film is formed, and this is defined as one cycle. In the following step, the supplied TMA reacts with AlOH to form an AlOAl bond. Therefore, the surface of the metal is chemically bonded, not physically adhered to, with an Al.sub.2O.sub.3 thin film to form a surface thin film, and the thickness of the surface thin film can be adjusted in a range of 1100 nm by adjusting the number of cycles in the ALD process.

Example 2

(40) In order to prepare a catalyst slurry to be applied onto the surface-treated metal foam, 50 g of alumina sol, 15 g of cobalt catalyst powder and 20 mL of isopropyl alcohol were mixed to prepare a cobalt catalyst slurry.

Example 3

(41) The surface-treated metal foam was coated with the prepared cobalt catalyst slurry by dip coating, dried at 120 C., and then calcinated at 400 C. to manufacture a cobalt metal foam catalyst.

Example 4

(42) A thermal medium-circulated heat exchanger type reactor including a tube unit filled with a cobalt metal foam catalyst and a shell unit in which a thermal medium circulates was made of a double tube including an inner tube having a diameter of 1 inch and an outer tube having a diameter of 2 inches. The length of the reactor was 430 mm. The inner tube of the tube unit having a diameter of 1 inch was filled with eighty cobalt metal foam catalysts, and the outer surface of the tube unit was provided with a heat exchange pin for the purpose of efficient heat exchange. In the outer tube having a diameter of 2 inches of the shell unit, thermal medium oil, the temperature of which is controlled constant at 222 C. by an additional exchanger using external cooling water, was circulated by an oil pump, and the thermal medium oil having passed through the shell unit of the heat exchanger type reactor was recovered into a thermal medium oil storage tank and then recirculated by the oil pump. Three thermocouples was provided in the center of the tube unit filled with cobalt metal foam catalysts at 200 mm intervals depending on the height of a cobalt metal foam catalyst layer to measure the reaction temperature. In order to reduce and pre-treat the cobalt metal foam catalyst layer, the heat exchanger type reactor was heated to 300 C. using an electric heater provided on the outer circumference of the shell unit.

Example 5

(43) The Fischer-Tropsch synthesis reaction was ran by supplying H.sub.2 at a flow rate of 200 mL/min and CO at a flow rate of 100 mL/min as reactants using the eighty cobalt metal foam catalysts and the thermal medium-circulated heat exchanger type reactor under the conditions of a reaction temperature of 222 C. and a reaction pressure of 20 atm. In the Fischer-Tropsch synthesis reaction using the cobalt metal foam catalysts and the thermal medium-circulated heat exchanger type reactor, during the reaction, the reaction temperature was maintained constant at the initial reaction temperature regardless of the high exothermic reaction heat. As a result, the CO conversion was 46.8%, liquid fuel yield was 31.4%, liquid fuel productivity was 98.2 mL.sub.liquid fuel/(kg.sub.catalyst*hr), and hydrocarbon yield was 37.5%.

Comparative Example 1

(44) In order to compare the reaction activity obtained from the Fischer-Tropsch synthesis reaction using the cobalt metal foam catalyst of Example 5 and the thermal medium-circulated heat exchanger type reactor with that obtained from running a Fischer-Tropsch synthesis reaction using a general spherical cobalt catalyst and a general fixed-bed reactor, the Fischer-Tropsch synthesis reaction was performed by filling the fixed-bed reactor with 4.5 g of the spherical cobalt catalyst and supplying H.sub.2 at a flow rate of 67 mL/min and CO at a flow rate of 33 mL/min as reactants under the conditions of a reaction temperature of 220 C. and a reaction pressure of 20 atm.

(45) Immediately after initiation of the reaction, there was a sudden rise in the reaction temperature, which increased to 280 C. in 40 minutes, so that the catalyst was deactivated by the precipitation of carbon, with the result that the Fischer-Tropsch synthesis reaction did not proceed, and thus liquid fuel was not produced.

(46) Although the preferred embodiments of the present invention have been disclosed for illustrative purposes, those skilled in the art will appreciate that various modifications, additions and substitutions are possible, without departing from the scope and spirit of the invention as disclosed in the accompanying claims.