Exhaust gas purifying method for fuel cell vehicle and exhaust gas purifying system for fuel cell vehicle

Abstract

An exhaust gas purifying method for a fuel cell vehicle comprises preparing an exhaust gas purifying system for the fuel cell vehicle, the exhaust gas purifying system including a methane removal catalyst for accelerating the conversion of methane into hydrogen and carbon monoxide. The methane removal catalyst comprises a catalytic ingredient including at least one of rhodium, platinum and palladium.

1 - 15 . (canceled)  
   
   
       16 . An exhaust gas purifying system, comprising: 
 a methane removal catalyst comprising a first catalytic ingredient including at least one of rhodium, platinum and palladium, the methane removal catalyst accelerating oxidation of methane into hydrogen and carbon monoxide by an oxidizing agent comprising oxygen,    wherein an oxygen excessive rate ζ of exhaust gas introduced to a region where the methane removal catalyst is disposed is set in a range from 50% to 98%, the oxygen excessive rate ζ being defined by a following formula (1):                  ζ   =         C     O   ⁢           ⁢   2             C     CH   ⁢           ⁢   4       ×   2     +       C     H   ⁢           ⁢   2       ×   0.5         ×   100             (   1   )                 where C O2  is a concentration of oxygen, C CH4  is a concentration of methane, and C H2  is a concentration of hydrogen and    wherein a temperature of the exhaust gas introduced to the methane removal catalyst is controlled in a range from 200° C. to 600° C.    
   
   
       17 . The exhaust gas purifying system of  claim 16 , 
 wherein the methane removal catalyst contains palladium as the first catalytic ingredient.    
   
   
       18 . The exhaust gas purifying system of  claim 16 , 
 wherein the methane removal catalyst contains at least one selected from the group consisting of alumina, silica, magnesia, zirconia, titania, and ceria as a porous carrier.    
   
   
       19 . The exhaust gas purifying system of  claim 18 , 
 wherein a concentration of the first catalytic ingredient is in a range from 1 wt % to 10 wt % with respect to a mass of the porous carrier in a state where adsorbed water is removed therefrom.    
   
   
       20 . The exhaust gas purifying system of  claim 16 , 
 wherein the methane removal catalyst contains zeolite.    
   
   
       21 . The exhaust gas purifying system of  claim 16 , 
 wherein a sum of contents of alkaline metal and alkaline earth metal in the methane removal catalyst is 3 wt % or below with respect to a mass of the methane removal catalyst.    
   
   
       22 . The exhaust gas purifying system of  claim 16 , further comprising: 
 a hydrogen and carbon monoxide removal catalyst accelerating conversion of hydrogen and carbon monoxide into water and carbon dioxide, the hydrogen and carbon monoxide removal catalyst being disposed downstream of the methane removal catalyst with regard to flow of the exhaust gas,    the hydrogen and carbon monoxide removal catalyst, comprising:    a second catalytic ingredient including at least one of rhodium, platinum and palladium.    
   
   
       23 . The exhaust gas purifying system of  claim 22 , wherein the hydrogen and carbon monoxide removal catalyst contains platinum as the second catalytic ingredient.  
   
   
       24 . The exhaust gas purifying system of  claim 22 , 
 wherein the second catalytic ingredient is formed by being loaded on a porous carrier, and a concentration of the second catalytic ingredient is in a range from 0.1 wt % to 3 wt % with respect to a mass of the porous carrier in a state where adsorbed water is removed therefrom.    
   
   
       25 . The exhaust gas purifying system of  claim 22 , 
 wherein the methane removal catalyst and the hydrogen and carbon monoxide removal catalyst are monolithic honeycomb catalysts.    
   
   
       26 . The exhaust gas purifying system of  claim 25 , 
 wherein a shape of openings of the monolithic honeycomb catalyst is formed to be circular or elliptical by a refractory inorganic compound, and    the first catalytic ingredient and the second catalytic ingredient are supported on surfaces of the openings formed to be circular or elliptical.    
   
   
       27 . The exhaust gas purifying system of  claim 26 , 
 wherein the refractory inorganic compound is contained in a range from 50 g/L to 100 g/L with respect to the monolithic honeycomb catalyst.    
   
   
       28 . The exhaust gas purifying system of  claim 16 , 
 wherein the exhaust gas comprises methane, hydrogen and oxygen.    
   
   
       29 . The exhaust gas purifying system of  claim 16 , 
 wherein the exhaust gas purifying system oxidizes methane in an exhaust gas of a vehicle.    
   
   
       30 . The exhaust gas purifying system of  claim 29 , 
 wherein the vehicle is a compressed natural gas vehicle, a fuel cell vehicle, or a hybrid vehicle.    
   
   
       31 . The exhaust gas purifying system of  claim 22 , 
 wherein an oxygen excessive rate of exhaust gas introduced to a region where the hydrogen and carbon monoxide removal catalyst is disposed is 100% or more, the oxygen excessive rate being represented by the formula (1).