NO_x Reduction Over MSU Molecular Sieve Catalysts Obtained by Direct Incorporation of Platinum and 12-Tungstophosphoric Acid H3PW_(12)O_(40): deNO_x Catalysis

摘要

The catalytic activity of silica-based mesoporous molecular sieves containing tungstophosphoric acid (HPW), platinum (Pt) and Pt/HPW, which were directly incorporated during the synthesis of MSU-type materials, was investigated in the NO_x reduction with propene in the presence of O2. The NO_x reduction reaction over these catalysts was studied for various Pt and HPW loadings, and oxygen concentrations (0-10 vol.%), and at different temperatures (170-350°C). The reduction of NO_x was found to occur for various amounts of O2 in given temperature domains. In the presence of HPW alone, the NO_x conversion levels remain low (20%); in contrast, over the Pt-containing catalysts, the NO_x conversion is high (around 90%), but it is limited to a narrow O2-poor domain (0.5-1 vol.%). Samples which contain small amounts of Pt and moderate loadings of HPW are the most active (up to 97% at 250°C and for 1 vol.% O2). However, whatever the O2 concentration, when the HPW loading increases, the NO_x conversion decreases.