A highly active and stable palladium zeolite catalyst for wet methane combustion

Natural gas engines are the most viable alternative to diesel and gasoline ones. However, the current state-of-art catalyst, palladium (Pd) on alumina, for eliminating unburnt methane from engine exhaust suffers from high light-off temperature (> 400 °C) and poor water tolerance. Here we systematically investigated the effects of zeolite structure and Si/Al ratio, catalyst calcination temperature and extra-framework cation type on catalytic performance of zeolite-supported Pd catalysts for wet methane combustion to overcome these limitations. We found that a 3.0 wt% Pd catalyst supported on Na-post-exchanged 500 °C-calcined IWV zeolite with a Si/Al ratio of 45 has a light-off temperature as low as 290 °C for methane combustion in the presence of 10 % water vapor while maintaining ca. 85 % methane conversion at 330 °C for 100 h. This study provides a new direction for bringing supported Pd catalysts close to real-world applications.