Designing a Ce/In-CHA OXZEO catalyst for high-efficient selective catalytic reduction of nitrogen oxide with methane

Abstract

Selective catalytic reduction of nitrogen oxides with methane (CH4-SCR) has emerged as a promising technology for mitigating exhaust emissions from natural gas vehicles, while its insufficient catalytic activity and durability are key barriers to application. In this study, novel Ce/In-CHA OXZEO catalysts were prepared, demonstrating exceptional catalytic performance and stability in the CH4-SCR reaction. Over these OXZEO catalysts, indium species predominantly existed in the form of InO+ and InxOy within the CHA zeolite framework, while CeO2 nanoparticles primarily resided as an external layer. During the CH4-SCR reaction, NO oxidation to form NO2 and nitrate species was triggered by CeO2, which further enhanced the activation of CH4 on InO+ sites, thus boosting the low-temperature CH4-SCR process by facilitating the formation of the key intermediate CH3NO2. The synergy between InO+ and CeO2 underscores the exceptional performance and stability of the Ce/In-CHA with a low SiO2/Al2O3 ratio in reducing NOx and CH4 emissions.