3DOM LaMnAl11O19-supported AuPd alloy nanoparticles: Highly active catalysts for methane combustion in a continuous-flow microreactor

Three-dimensionally ordered macroporous (3DOM) LaMnAl11O19 and xAuPd(y)/3DOM LaMnAl11O19 (x = 0.44 - 1.91 wt%; y = 1.80 - 1.86) were prepared via the polymethyl methacrylate (PMMA)-templating and gas bubble-assisted polyvinyl alcohol (PVA)-protected reduction routes, respectively. Physicochemical properties of the samples were characterized by a number of analytical techniques. Catalytic activities of the samples were measured for methane combustion in a continuous-flow microreactor. It is shown that the LaMnAl11O19 in each of the samples was hexagonal in crystal structure, and all of the samples possessed a good-quality 3DOM architecture with a surface area of 24.4 - 28.2 m(2)/g. The Au-Pd nanoparticles (NPs) with an average size of 2.8 nm were uniformly dispersed on the macropore walls of 3DOM LaMnAl11O19. The 1.91AuPd(1.80)/3DOM LaMnAl11O19 sample performed the best for methane combustion (T-50% = 342 degrees C and T-90% = 402 degrees C at a space velocity of 20,000 mL/(g h)). The deactivation of the 1.91AuPd(1.80)/3DOM LaMnAl11O19 catalyst induced by water vapor introduction was reversible, whereas that induced by SO2 addition was irreversible. It is concluded that the good catalytic activity of 1.91AuPd(1.80)/3DOM LaMnAl11O19 was related to its good-quality 3DOM structure, highly dispersed Au-Pd NPs, high adsorbed oxygen species concentration, good low-temperature reducibility, and strong interaction between Au-Pd alloy NPs and 3DOM LaMnAl11O19.