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 degrees 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 degrees 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 degrees 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.