Catalyst for producing hydrogen and method for producing hydrogen

Abstract

A metal-supporting catalyst for decomposing ammonia into hydrogen and nitrogen. The catalyst shows a high performance with a low cost and being advantageous from the viewpoint of resources, and an efficient method for producing hydrogen using the catalyst. The catalyst catalytically decomposes ammonia gas to generate hydrogen. The hydrogen generation catalyst includes, as a support, a mayenite type compound having oxygen ions enclosed therein or a mayenite type compound having 10 15 cm −3 or more of conduction electrons or hydrogen anions enclosed therein, and metal grains for decomposing ammonia are supported on the surface of the support. Hydrogen is produced by continuously supplying 0.1-100 vol % of ammonia gas to a catalyst layer that comprises the aforesaid catalyst, and reacting the same at a reaction pressure of 0.01-1.0 MPa, at a reaction temperature of 300-800° C. and at a weight hourly space velocity (WHSV) of 500/mlg −1 h −1 or higher.

1 . A catalyst for producing hydrogen comprising a mayenite-type compound as a support which includes 10 15  cm −3  or more of conduction electrons or hydrogen anions, and metal particles for ammonia decomposition which are supported on a surface of the support. 
     
     
         2 . A catalyst for producing hydrogen comprising a mayenite-type compound as a support which includes oxygen ions which has not been made to include 10 15  cm −3  or more of conduction electrons or hydrogen anions, and metal particles for ammonia decomposition which are supported on a surface of the support. 
     
     
         3 . The catalyst for producing hydrogen according to  claim 1 , wherein the catalytically active metal is at least one selected from the metal elements of Groups VIII, IX, and X. 
     
     
         4 . The catalyst for producing hydrogen according to  claim 1 ,
 wherein the support includes a mayenite-type compound powder or compact and has an amount of the catalytically active metal particles of 0.01 wt % to 30 wt % and a BET specific surface area of 1 to 100 m 2 g −1 .   
     
     
         5 . A method for producing the catalyst for producing hydrogen according to  claim 1 , the method comprising a step of supporting a compound of the active metal on the support by an impregnation method, a physical mixing method, a thermal decomposition method, a liquid phase method, or a vapor deposition method and then reducing the compound of the catalytically active metal by heating in a reducing atmosphere to adhere metal particles to a surface of the support, or a step of directly supporting the metal particles by sputtering. 
     
     
         6 . The method for producing the catalyst for producing hydrogen according to  claim 5 , wherein the impregnation method includes a step of dispersing a powder or compact in a solvent solution of the compound of the catalytically active metal, a step of evaporating a solvent of the solvent solution to dry the compound of the catalytically active metal and form a catalyst precursor composed of the compound of the catalytically active metal, and a step of reducing the compound of the catalytically active metal by heating in a reducing atmosphere to support the particles of the catalytically active metal on the surface of the powder or compact. 
     
     
         7 . The method for producing the catalyst for producing hydrogen according to  claim 6 , wherein the mayenite-type compound powder is synthesized by a hydrothermal method. 
     
     
         8 . A method for producing hydrogen comprising continuously supplying an ammonia gas with a volume fraction of 0.1 to 100% to a catalyst layer including the catalyst according to  claim 1 , and then performing contact decomposition reaction at a reaction pressure of 0.01 MPa to 1.0 MPa, a reaction temperature of 300° C. to 800° C., and a weight hourly space velocity (WHSV) of 500/mlg −1 h −1  or more. 
     
     
         9 . The catalyst for producing hydrogen according to  claim 2 , wherein the catalytically active metal is at least one selected from the metal elements of Groups VIII, IX, and X. 
     
     
         10 . The catalyst for producing hydrogen according to  claim 2 , wherein the support includes a mayenite-type compound powder or compact and has an amount of the catalytically active metal particles of 0.01 wt % to 30 wt % and a BET specific surface area of 1 to 100 m 2 g −1 . 
     
     
         11 . A method for producing the catalyst for producing hydrogen according to  claim 2 , the method comprising a step of supporting a compound of the active metal on the support by an impregnation method, a physical mixing method, a thermal decomposition method, a liquid phase method, or a vapor deposition method and then reducing the compound of the catalytically active metal by heating in a reducing atmosphere to adhere metal particles to a surface of the support, or a step of directly supporting the metal particles by sputtering. 
     
     
         12 . The method for producing the catalyst for producing hydrogen according to  claim 11 , wherein the impregnation method includes a step of dispersing a powder or compact in a solvent solution of the compound of the catalytically active metal, a step of evaporating a solvent of the solvent solution to dry the compound of the catalytically active metal and form a catalyst precursor composed of the compound of the catalytically active metal, and a step of reducing the compound of the catalytically active metal by heating in a reducing atmosphere to support the particles of the catalytically active metal on the surface of the powder or compact. 
     
     
         13 . The method for producing the catalyst for producing hydrogen according to  claim 12 , wherein the mayenite-type compound powder is synthesized by a hydrothermal method. 
     
     
         14 . A method for producing hydrogen comprising continuously supplying an ammonia gas with a volume fraction of 0.1 to 100% to a catalyst layer including the catalyst according to  claim 2 , and then performing contact decomposition reaction at a reaction pressure of 0.01 MPa to 1.0 MPa, a reaction temperature of 300° C. to 800° C., and a weight hourly space velocity (WHSV) of 500/mlg −1 h −1  or more.