Abstract
Three-dimensionally ordered macro-/mesoporous 26.9wt% CeO2–Al2O3 (denoted as 3DOM 26.9CeO2–Al2O3)-supported noble metal nanocatalysts (xM/3DOM 26.9CeO2–Al2O3, x=0.27–0.81wt%; M=Au, Ag, Pd, and Pt) were prepared using the polymethyl methacrylate-templating and polyvinyl pyrrolidone- or polyvinyl alcohol-protected reduction methods, respectively. It is shown that the xM/3DOM 26.9CeO2–Al2O3 samples displayed a high-quality 3DOM architecture with a bimodal pore (macropore size=180–200nm and mesopore size=4–6nm) structure and a surface area of 102–108m2/g, with the noble metal nanoparticles (3–4nm in size) being highly dispersed on the 3DOM 26.9CeO2–Al2O3 surface. The 0.27Pt/3DOM 26.9CeO2–Al2O3 sample performed the best (T90%=198°C at space velocity=20,000mL/(gh)) for toluene oxidation. The addition of moisture to the feedstock induced a positive effect on catalytic activity. The apparent activation energies obtained over the xM/3DOM 26.9CeO2–Al2O3 samples were in the range of 46–100kJ/mol, with the 0.27Pt/3DOM 26.9CeO2–Al2O3 sample possessing the lowest apparent activation energy. It is concluded that the good catalytic performance of 0.27Pt/3DOM 26.9CeO2–Al2O3 was associated with its higher adsorbed oxygen species concentration, better low-temperature reducibility, and stronger interaction between Pt and 3DOM 26.9CeO2–Al2O3 as well as the unique bimodal porous structure.
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