Oxidation of Trace Ethylene at 0 °C over Platinum Nanoparticles Supported on Silica

Oxidation of trace ethylene (50 ppm) at 0 °C was systematically studied using Pt nanoparticles supported on mesoporous silica (SBA-15) in a fixed-bed flow reactor. The SBA-15 supported Pt catalyst (1.8 wt % Pt loading) exhibited an ethylene conversion higher than 99% at the initial stage, which gradually began to decrease at 90 min and reached 33% within 240 min. The CO2 yield was lower than the corresponding ethylene conversion before the steady state was reached. This was due to the formation of intermediates that were stabilized on the catalyst surface. These intermediates could be recovered in the form of CO2 by heating the spent catalyst in a mixed N2 and He (1:19, v/v) flow at 150 °C. The addition of water vapor to the catalyst bed decreased the original activity drastically because physically adsorbed water molecules partly blocked the active Pt sites. Control experiments using nonordered silica supports (Aerosil 380 and 200) showed similar catalytic behavior as that observed with SBA-15. The formation of highly dispersed Pt nanoparticles on the silica surfaces is thus the key to the development of effective Pt catalysts for low-temperature oxidation of ethylene.