Mesoporous Cr 2 O 3 -supported Au–Pd nanoparticles: High-performance catalysts for the oxidation of toluene

Three-dimensionally ordered mesoporous Cr 2 O 3 ( meso -Cr 2 O 3 ) and its supported Au, Pd, and Au–Pd (0.90 wt% Au/ meso -Cr 2 O 3, 1.00 wt% Pd/ meso -Cr 2 O 3, and x Au 1 Pd 2 / meso -Cr 2 O 3 ( x  = 0.50–1.95 wt%) catalysts were prepared using the KIT-6-templating and polyvinyl alcohol-protected reduction methods, respectively. Physicochemical properties of the samples were characterized by means of numerous techniques, and their catalytic activities were evaluated for the oxidation of toluene. It is found that the meso -Cr 2 O 3 with a high surface area of 74 m 2 /g was rhombohedral in crystal structure and the noble metal nanoparticles (NPs) with a size of 2.9–3.7 nm were uniformly dispersed on the surface of meso -Cr 2 O 3. The 1.95Au 1 Pd 2 / meso -Cr 2 O 3 sample performed the best: the T 10%, T 50%, and T 90% (temperatures required for achieving toluene conversions of 10, 50, and 90%) were 87, 145, and 165 °C at a space velocity of 20,000 mL/(g h), respectively, and the apparent activation energy was the lowest (31 kJ/mol) among all of the samples. The effect of moisture on the catalytic activity of the 1.95Au 1 Pd 2 / meso -Cr 2 O 3 sample was also examined. It is concluded that the excellent catalytic performance of 1.95Au 1 Pd 2 / meso -Cr 2 O 3 was associated with its small Au–Pd particle size, high adsorbed oxygen species concentration, good low-temperature reducibility, and strong interaction between Au–Pd NPs and meso -Cr 2 O 3.