Three-dimensionally ordered macroporous LaMnAl11O19-supported Pd nanocatalysts highly active for methane combustion

Abstract

Three-dimensionally ordered macroporous (3DOM) LaMnAl11O19 and 0.97wt% Pd/3DOM LaMnAl11O19 samples with a good-quality 3DOM structure have been prepared using the poly(methyl methacrylate) (PMMA)-templating and polyvinyl alcohol (PVA)-protected reduction methods, respectively. The Pd nanoparticles (NPs) with a size of 2–5nm were uniformly dispersed on the macropore wall surface of 3DOM LaMnAl11O19. Due to the highest adsorbed oxygen species concentration and the best low-temperature reducibility, the 0.97wt% Pd/3DOM LaMnAl11O19 sample showed the best catalytic activity for methane combustion, with the reaction temperatures (T10%, T50%, and T90%) required for achieving methane conversions of 10, 50, and 90% being 259, 308, and 343°C at SV=20,000mL/(gh), respectively. The 0.97wt% Pd/3DOM LaMnAl11O19 catalyst was catalytically stable, whereas the 0.98wt% Pd/3DOM Mn2O3 sample was partially deactivated after 50h of methane oxidation. The introduction of 3.0vol% H2O or 2.0 vol% CO2 to the reaction system resulted in the reversible deactivation of 0.97wt% Pd/3DOM LaMnAl11O19, but the addition of 100ppm SO2 led to the irreversible deactivation of the catalyst. It is concluded that the good-quality 3DOM structure, uniformly dispersed Pd NPs, high adsorbed oxygen species concentration, good low-temperature reducibility, and strong interaction between Pd NPs and 3DOM LaMnAl11O19 were accountable for the good catalytic performance of 0.97wt% Pd/3DOM LaMnAl11O19.