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

Abstract

Co1.5M1.5/Al1−xTix 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 TiO2 phase being detected. Substitution of partial Al for Ti significantly enhanced NO direct decomposition activity of these catalysts. In particular, catalyst Co3.0/Al0.9Ti0.1O (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% O2 in N2 stream). CATO also showed the highest resistance to SO2 poisoning to NO direct decomposition, with the activity being only reduced by 16% in the presence of 64 ppm of SO2 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 SO2 poisoning.