Synthesis and characterisation of K-Ag/Al2O3 catalysts for CH4-SCR of NOx: effect of SO2

Abstract

This paper characterizes the integrated activity of fresh and used catalysts on the selective catalytic reduction of NOx using CH4. The synthesised K-Ag/Al2O3 catalysts exhibited a promotional effect on deNOx activity in the presence of SO2. In addition, 130 h of time-on-stream reactions demonstrated the thermal and mechanical stability of the synthesised materials. A TEM analysis and diffraction patterns demonstrated the sintering of finely dispersed particles to similar to 0.5 micron size clusters by sulphation. Furthermore, under reaction conditions, the de-sulphation initiated the re-dispersion of the Ag clusters to different sized particles. The TPD studied demonstrated the strong adsorption sites for methane and formation of R-SOx compounds. This surface modification in the SO2 feed stream is considered to be the reason for the promotional effect on the deNOx reaction.