Effect of highly active oxygen on methane catalytic removal at low temperatures using a core–shell structural catalyst

Abstract

The removal of alkanes and alkanols at low temperatures is useful in chemical industry. This study focused on methane catalytic removal at low temperatures and developed a novel core–shell structural Pt–Pd catalyst to catalyze methane to <10–4 kPa (in Air) at approximately 200 °C. Surface oxygen and vacancies play important roles in the performance of catalysts. This was determined by reaction kinetics, HRTEM-EDS, isotopic exchange, DFT calculation, and several in situ techniques, such as XAS, FT-IR, and XPS, which were employed to characterize the reaction intermediates, active sites, coordination numbers, and d-band centers. For the Pt–core@Pd–shell catalyst, exposed Pd active sites are supported by the Pt species, and electron transfer occurs between these two metal species. This transfer lowers the coordination of surface Pd sites and electron density, making the surface oxygen species more active in the C–H bond activation. In addition, exposed Pd species are largely reduced during catalytic reactions, leaving a significant number of vacancies. These vacancies also assist during C–H bond activation in alkanes and alkanols. Core shell structure provides new direction for the design of high-performance catalysts.