N2O decomposition by mesoporous silica supported Rh catalysts

Abstract

Nitrous oxide (N2O), a greenhouse gas produced by nitric acid and adipic acid plants, damages the ozone layer and causes many environmental problems. The potential of MCM-41, SBA-15-Conventional (SBA-15-C), SBA-15-Spherical (SBA-15-S) and KIT-6 supported Rh catalysts has been explored at specific conditions for N2O decomposition in order to investigate the characteristics of new catalyst supports (SBA-15-S, KIT-6) for this application. A Rh metal loading of 1wt% was impregnated to synthesize mesoporous silica supported Rh catalysts. The catalysts were characterized by scanning electron microscope (SEM), energy dispersive X-ray spectroscopy (EDX), X-ray diffraction (XRD), N2 adsorption/desorption, X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM) and CO-chemisorption techniques. Of all the catalysts, Rh/SBA-15-S not only showed the highest activity, but also the best strength against ageing impact, O2 inhibiting effect and long-term stability. The higher metal dispersion due to the smaller Rh particle size and a greater formation of Rh+1 than Rh0 or Rh+3 on SBA-15-S compared to the other supports, favoured a higher N2O decomposition. The larger pore size of SBA-15-S in Rh/SBA-15-S might favour a better Rh access, diffusion and dispersion and lead to higher activity. The higher long-term stability of Rh/SBA-15-S, with preserved support characteristics, than the other supports indicates its significance.