3DOM CeO2-supported RuyM (M = Au, Pd, Pt) alloy nanoparticles with improved catalytic activity and chlorine-tolerance in trichloroethylene oxidation

摘要

Ruthenium-based materials are promising catalysts for the removal of chlorine-containing volatile organic compounds (CVOCs) due to their good ability in cleaving the C-Cl bonds and decreasing the Cl deposition. However, the roles of noble bimetals alloyed with Ru have not been clarified clearly. In this work, the bimetallic RuyM (M = Au, Pd or Pt) alloys supported on three-dimensionally ordered macroporous (3DOM) CeO2 (xRu(y)M/3DOM CeO2; RuyM loading (x) = 0.90-0.93 wt%, and Ru/M molar ratio (y) = 2.77-2.87) were fabricated by the polymer microbead-templating and polyvinyl alcohol-protected reduction methods, and their physicochemical properties were well measured using a number of techniques. Oxidation of trichloroethylene (TCE) was used to evaluate catalytic performance of the as-obtained samples with a good-quality 3DOM structure and a surface area of 39-44 m(2) g(-1). The Ru, Pd, and RuyM nanoparticles (NPs) with an average size of 2.9-3.5 nm were uniformly dispersed on the skeleton surface of 3DOM CeO2. The 0.93Ru(2.87)Pd/3DOM CeO2 sample showed the highest catalytic activity and the lowest apparent activation energy (34 kJ mol(-1)), with the temperatures (T-50% and T-90%) at TCE conversions of 50 and 90% being 237 and 298 degrees C at a space velocity of 20 000 mL g(-1) h(-1), respectively. Simultaneously, 0.93Ru(2.87)Pd/3DOM CeO2 exhibited the highest TCE oxidation rate (30.3 mu mol g(Noblemetal)(-1) s(-1)) and the highest TOFNoblemetal (3.1 x 10(-3) s(-1)) at 250 degrees C. The 0.93Ru(2.87)Pd/3DOM CeO2 sample also possessed a better hydrothermal stability than the 0.85Ru/3DOM CeO2 sample after hydrothermal ageing treatment at 750 degrees C. Effects of H2O, CO2, and HCl on catalytic activity of 0.93Ru(2.87)Pd/3DOM CeO2 were also examined. The presence of Ru in the samples was favorable for generation of HCl and Cl-2 and reduction of the by-products in TCE oxidation, and tetrachloroethylene was the main by-product. The possible catalytic mechanism over 0.93Ru(2.87)Pd/3DOM CeO2 was also proposed. The outstanding catalytic efficiency of 0.93Ru(2.87)Pd/3DOM CeO2 could be assigned to the high adsorbed oxygen species, good low-temperature reducibility, strong TCE adsorption and activation ability, and formation of the intimate nanointerface between RuPd NPs and 3DOM CeO2. This work provides a practical guideline for rationally designing the efficient bimetallic catalysts for CVOCs removal under the industrial conditions.