Constructing Azro3 (A=CA, Sr, Ba) Perovskite and Ln2zr2o7 (Ln=La, Pr, Nd) Pyrochlore Composite Oxides for Oxidative Coupling of Methane

Abstract

Herein, AZrO3 (A=Ca, Sr, Ba) perovskites and Ln2Zr2O7 (Ln=La, Pr, Nd) pyrochlores have been successfully synthesized using a simple solid-state method for catalyzing oxidative coupling of methane (OCM). The catalytic performance of perovskite exceeds that of pyrochlore because the A-site oxides of perovskites are more basic than those of pyrochlores. Furthermore, the A-site oxide surface has abundant moderate and strong basic sites as well as chemisorbed oxygen species including O2- and O22-, which are beneficial to the selectivity and yield of C2. Moreover, the Zr-O bond strength affects the C2 selectivity of both perovskites and pyrochlores. The Zr-O bond strength of pyrochlores is weak. Thus, this bond breaks easily during OCM, which in turn activates its lattice oxygen species, increases COx production (a deep oxidation product), and reduces C2 selectivity.

Keywords: Oxidative coupling of methane, perovskite, pyrochlore, basic sites, Zr-O bond strength