Low-Temperature Methane Combustion Using Ozone over Coβ Catalyst
Shunsaku Yasumura, Ken Nagai, Shinta Miyazaki, Yucheng Qian, Duotian Chen, Takashi Toyao, Yuichi Κamiya, Ken‐ichi Shimizu
Abstract
Catalytic methane (CH 4 ) combustion is a promising approach to reducing the release of unburned methane in exhaust gas. Here, we report Co-exchanged β zeolite (Coβ) as an efficient catalyst for CH 4 combustion using O 3 . A series of ion-exchanged β zeolites (Co, Ni, Mn, Fe, and Pd) are subjected to the catalytic test, and Coβ exhibits a superior performance in a low-temperature region (<100 °C). The results of X-ray absorption spectroscopy (XAS) and catalytic tests for Coβ with different Co loadings indicate the isolated Co species is the plausible active site. The reaction mechanism of CH 4 combustion over the isolated Co 2+ cation is theoretically investigated by the single-component artificial force-induced reaction (SC-AFIR) method to thoroughly search for possible reaction routes. The resulting path toward CO 2 formation shows an activation energy of 73 kJ/mol for the rate-determining step and an exothermicity of 1025 kJ/mol, which supports the experimental results. During a long-term catalytic test for 160 h without external heating, the CH 4 conversion gradually decreases from 80 to 40%, but the conversion fully recovers after dehydration at 500 °C (0.5 h). The copresence of H 2 O and CO exhibits a negative impact on the catalytic activity, while NO and SO 2 do not markedly change the catalytic activity.