Method for making a cobalt metal foam catalyst in which a cobalt catalyst powder is coated onto the surface of a metal foam, the cobalt metal foam catalyst, a thermal-medium- circulating heat-exchange reactor using the cobalt metal foam catalyst, and a method for producing a liquid fuel by means of a fischer-tropsch synthesis reaction using the thermal-medium-circulating heat-exchange reactor

Abstract

The present invention relates to a method of manufacturing a cobalt metal foam catalyst including a metal foam coated with cobalt catalyst powder, a cobalt metal foam catalyst manufactured by the method, a thermal medium-circulated heat exchanger type reactor using the cobalt metal foam catalyst, and a method of producing liquid fuel by Fischer-Tropsch synthesis using the reactor. An object of the present invention is to provide a catalyst, which is used to obtain high liquid fuel productivity even at a low CO conversion ratio because the reaction temperature can be kept stable by controlling reaction heat with high efficiency in Fischer-Tropsch synthesis so that the mass transfer characteristics of a catalyst layer can be improved, and a method of manufacturing the catalyst, a reactor filled with the catalyst, and a method of producing liquid fuel using the reactor. The method of manufacturing a cobalt metal foam catalyst includes the steps of: surface-pretreating a metal foam by atomic layer deposition (ALD) using trimethylaluminum ((CH 3 ) 3 Al) and water to form an Al 2 O 3 thin film; preparing a cobalt catalyst slurry composed of a mixture of alumina sol, cobalt catalyst powder 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.

1 . A method of manufacturing a cobalt metal foam catalyst including a metal foam coated with cobalt catalyst powder, comprising the steps of:
 surface-pretreating a metal foam by atomic layer deposition (ALD) using trimethylaluminum ((CH 3 ) 3 Al) and water to form an Al 2 O 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.   
     
     
         2 . The method of manufacturing a cobalt metal foam catalyst according to  claim 1 , wherein the metal foam is made of any one selected from the group consisting of aluminum, iron, stainless steel, iron-chromium-aluminum alloy (Fe—Cr—Al alloy), nickel-chromium alloy, copper-nickel alloy, aluminum-copper alloy, zinc-copper alloy and silver-copper alloy. 
     
     
         3 . The method of manufacturing a cobalt metal foam catalyst according to  claim 1 , wherein the cobalt catalyst slurry is prepared by mixing a mixed solution including alumina sol and isopropyl alcohol with cobalt catalyst powder such that a mixing ratio of the mixed solution to the cobalt catalyst powder is 10:1˜1:5. 
     
     
         4 . The method of manufacturing a cobalt metal foam catalyst according to  claim 3 , wherein the mixed solution including alumina sol and isopropyl alcohol is prepared by mixing alumina sol including alumina and water with isopropyl alcohol, and the mixed solution has a viscosity of 1˜50 cP. 
     
     
         5 . The method of manufacturing a cobalt metal foam catalyst according to  claim 1 , wherein the cobalt catalyst is prepared by impregnating a support selected from the group consisting of alumina (Al 2 O 3 ), silica (SiO 2 ) and titania (TiO 2 ) with a cobalt precursor selected from the group consisting of cobalt nitrate (Co(NO 3 ) 2 6H 2 O) and cobalt acetate ((CH 3 CO 2 ) 2 Co4H 2 O). 
     
     
         6 . The method of manufacturing a cobalt metal foam catalyst according to  claim 1 , wherein the dip coating and drying are repetitively performed several times such that the surface of the metal foam is coated with the cobalt catalyst to form a thin film which has strong adhesivity to the surface of the metal foam. 
     
     
         7 . A cobalt metal foam catalyst including a metal foam coated with cobalt catalyst powder, manufactured by the method of  claim 1 , wherein, when a Fischer-Tropsch synthesis reaction is performed using the metal foam catalyst, a reaction temperature is maintained constant at an initial reaction temperature of 190˜250° C. in spite of high exothermic reaction heat, and a high liquid fuel productivity of 98.2 mL liquid fuel /(kg catalyst *hr) is obtained even at a low CO conversion ratio of 46.8%. 
     
     
         8 . A thermal medium-circulated heat exchanger type reactor, comprising:
 a tube unit configured such that synthesis gas is supplied to a cobalt catalyst layer filled with the cobalt metal foam catalysts each including a metal foam coated with cobalt catalyst powder, each of the metal foam and the cobalt catalyst powder having been manufactured by the method of  claim 1 , to conduct a reaction;   a shell unit configured to cover the tube unit such that thermal medium oil having a predetermined temperature is circulated to control reaction heat generated from a Fischer-Tropsch synthesis reaction; and   an electric heater provided at the circumference of the shell unit to heat a cobalt catalyst layer to reduce and pretreat the cobalt catalyst layer.   
     
     
         9 . The thermal medium-circulated heat exchanger type reactor according to  claim 8 , further comprising: a heat exchange pin protruding from an outer surface of the tube unit to accelerate heat exchange between the tube unit and the thermal medium oil. 
     
     
         10 . The thermal medium-circulated heat exchanger type reactor according to  claim 8 , wherein the thermal medium oil is supplied by a thermal medium oil storage tank supplying thermal medium oil to a lower portion of the shell unit through a thermal medium oil supply line and recovering high-temperature thermal medium oil discharged from an upper portion of the shell unit through a thermal medium oil recovery line and then storing the high-temperature thermal medium oil; a thermal medium oil circulation pump provided along the thermal medium oil supply line to supply the thermal medium oil stored in the thermal medium oil storage tank; and a heat exchanger provided along the thermal medium oil supply line located behind the thermal medium oil circulation pump to perform heat exchange between cooling water and thermal medium oil to control reaction temperature. 
     
     
         11 . The thermal medium-circulated heat exchanger type reactor according to  claim 8 , wherein the electric heater for heating the cobalt catalyst layer to reduce and pretreat the cobalt catalyst layer is configured such that the cobalt catalyst layer is heated to 300˜500° C. 
     
     
         12 . The thermal medium-circulated heat exchanger type reactor according to  claim 10 , wherein the circumference of the thermal medium storage tank is with a heater to control the temperature of the stored thermal medium oil. 
     
     
         13 . A method of producing liquid fuel by a Fischer-Tropsch synthesis reaction using a thermal medium-circulated heat exchanger type reactor, wherein the thermal medium-circulated heat exchanger type reactor of  claim 10  using the cobalt metal foam catalyst including a metal foam coated with cobalt catalyst powder is used, and 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 190˜250° C. and a reaction pressure of 20˜25 atm, and simultaneously the reaction is conducted, thus producing liquid fuel. 
     
     
         14 . The method of producing liquid fuel according to  claim 13 , wherein the reaction is performed while increasing a heat exchange efficiency using a heat exchange pin provided on an outer surface of the tube unit during the Fischer-Tropsch synthesis reaction. 
     
     
         15 . The method of producing liquid fuel according to  claim 13 , wherein the exothermic reaction heat recovered by thermal medium oil of the shell unit is removed by a heat exchanger that controls the temperature of the thermal medium oil using external cooling water to maintain the temperature of the thermal medium oil constant. 
     
     
         16 . The method of producing liquid fuel according to  claim 15 , wherein the temperature of the thermal medium oil is adjusted to 190˜250° C. 
     
     
         17 . The method of producing liquid fuel according to  claim 13 , wherein the cobalt catalyst layer is reduced and pretreated by heating it to 300˜500° C.