NOx Reduction Over MSU Molecular Sieve Catalysts Obtained by Direct Incorporation of Platinum and 12-Tungstophosphoric Acid H3PW12O40: deNOx Catalysis

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 NOx reduction with propene in the presence of O2. The NOx 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 NOx was found to occur for various amounts of O2 in given temperature domains. In the presence of HPW alone, the NOx conversion levels remain low (20%); in contrast, over the Pt-containing catalysts, the NOx 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° and for 1 vol.% O2). However, whatever the O2 concentration, when the HPW loading increases, the NOx conversion decreases.