Catalytic decomposition of nitrous oxide over calcined cobalt aluminum hydrotalcites

Abstract

Catalytic decomposition of nitrous oxide has been carried out over calcined cobalt aluminum hydrotalcites of general formula [Co1−xAlx(OH)2[CO3]x/2 H2O where x = 0.25–0.33 at 50 Torr (1 Torr = 133 Pa) initial pressure of N2O in a static glass recirculatory reactor (130 cc) in the temperature range 150–280°C. All catalysts showed a first order dependence in N2O without significant oxygen inhibition. The activity increased with an increase in cobalt concentration present in the sample. The catalyst precursor synthesized under low supersaturation (LS) exhibited a higher activity than the precursor synthesized by sequential precipitation (SP) method. The observed trend in the activity is explained based on the surface concentration of cobalt, determined by XPS and matrix effects. Prior to catalytic studies, the fresh and calcined samples were characterized by various physicochemical techniques such as XRD, FT–IR, TG–DSC, TEM (with EDAX) and BET surface area measurements.