Research on exhaust emission control characteristics of a natural gas vehicle - Characteristics of methane oxidation reaction of three-way catalysts

Abstract Model gas reaction experiments were conducted to analyze the factors causing the conversion rate of hydrocarbons (consisting mainly of CH 4 ) to decline in the lean-mixture region, using a natural gas engine fitted with a three-way catalyst. The results showed that there was no decline in the conversion rate of methane in CH 4 -O 2 reactions in the lean-mixture region. However, it was observed that oxidation of CH 4 was suppressed when either H 2 O or NO was also present. It is thought that prior adsorption of H 2 O and NO inhibits adsorption of CH 4 at active sites, resulting in a lower conversion rate.