Sulfur-Resistant NO Decomposition Catalysts Derived from Co−Ca/Ti−Al Hydrotalcite-like Compounds

Co 1.5 M 1.5 /Al 1− x Ti x hydrotalcite-like compounds (where M = Co, Ca and x = 0, 0.1) were synthesized by a constant-pH coprecipitation. The derived oxides from hydrotalcites upon calcination at 800 °C for 4 h were all of spinel phase without crystalline TiO 2 phase being detected. Substitution of partial Al for Ti significantly enhanced NO direct decomposition activity of these catalysts. In particular, catalyst Co 3.0 /Al 0.9 Ti 0.1 O (CATO) showed the highest NO direct decomposition percentage, up to 86% at 300 °C with GHSV of 30 000 h −1 (800 ppm of NO and 8% O 2 in N 2 stream). CATO also showed the highest resistance to SO 2 poisoning to NO direct decomposition, with the activity being only reduced by 16% in the presence of 64 ppm of SO 2 in the mixed gas stream at 300 °C. The in-situ FT-IR spectra indicate different adsorption species over the catalysts, revealing NO surface storage/decomposition involves different adsorption reactions that determine the NO decomposition activity and resistance to SO 2 poisoning.