Facile Strategy to Extend Stability of Simple Component-Alumina-Supported Palladium Catalysts for Efficient Methane Combustion.

Abstract

It is of practical importance to develop a stable and accessible methane combustion catalyst which could retain an excellent activity under drastic conditions. Herein, we introduce a facile approach to extend the stability of conventional Pd/Al2O3 catalysts through tailoring the pore size of mesoporous aluminas (MAs) and the interaction between Pd and Al. By modulating the addition of templates (deoxycholic acid and polyvinylpyrrolidone), a series of MAs with tunable and uniform pore size were obtained through a designed sol-gel method. Unexpectedly, Pd/MA-800-5 catalyst prepared with relatively large pore size (ca. 12 nm) MAs exhibited an efficient and sustained performance under a variety of operating conditions, while those prepared with small pore size (ca. 5-7 nm) MAs suffered from a significant loss of activity during high temperature cyclic reactions (280-850 °C) due to the decomposition of confined PdO. The enhancement could be attributed to the suitable particle size, higher crystallinity, generated active sites, improved reducibility, and thermal stability of PdO species. Moreover, the variation of pore size also resulted in a different reaction mechanism. Such a pore size promotion strategy effectively invoked a superior catalytic performance while keeping the catalyst components simple, which can be extended to prepare other high-performance metal oxide-supported catalysts for catalytic applications.