Effect of parameters on NO reduction by methane in presence of excess O 2 and functionalized AlMCM-41 as catalysts

Abstract

Abstract The selective catalytic reduction of NO with CH4 over functionalized AlMCM-41 has been studied. Factors such as platinum rate exchange (0.5–4.0 wt %), temperature (100–800 °C), GHSV (8000–16,000 h-1) and CH4/O2 ratio (0.25–2.0) have been investigated. The highest NO reduction rate was found at a stoichiometric ratio of CH4/NO ≅ 2, T≈350 °C, 2.5 wt% of platinum and a GHSV of 12,000 h-1. The rate of intermediate N2O reduction is minimal at high CH4 pressures. The reaction product suggests a short NO2 lifetime. The NO/NO2 oxidation/reduction cycle delays NO reduction to N2 until all O2 is consumed under helium flow. For Pt(X)-catalysts, the NO maximum conversion depends on the factors mentioned above and on aging steam. Then, for high oxygen concentrations (at 350 °C), catalyst Pt (2.5 wt%)-H-AlMCM-41 shows a good NO reduction. The presence of Pt ions, oxidation states and their uniform dispersion within the catalysts affect positively this reaction. It was observed that the specific catalytic behaviors of the prepared materials sharply decreased when O2 increased with a steam aging temperature ≥600 °C. Studied factors induced the formation of octahedral aluminum due to a dealumination phenomenon that leads to a structural collapse and a loss of activity.