Keywords: nitrogen monoxide, selective reduction, propane, copper oxide, cerium oxide, alumina
Selective catalytic reduction of nitric oxide over copper oxide and cerium oxide catalysts
The selective catalytic reduction of nitric oxide with hydrocarbons in an oxygen-containing simulated flue gas has been investigated for a series of copper oxide and cerium oxide alumina supported catalysts at 600–775 K. The activity of these catalysts for the reduction of NO by methane or propane has been investigated in simulated flue gas. The effects of sulphates on the catalyst, and of water vapour and/or gaseous sulphur dioxide have been examined for both the SCR of NOx by propane and direct decomposition of NO. Both copper sulphate on alumina and cerium sulphate on alumina are substantially less active for propane SCR than the respective oxides. Both catalyst types are reversibly inhibited by the presence of water vapour. The effect of sulphur dioxide in the gas stream appears to be only mildly inhibiting, but since the optimum temperature range for propane reduction of NO is the same as the optimum temperature range for SO2 absorption, the CuO/Al2O3 sorbent/catalyst will quickly become sulphated, even at low flue gas SO2 concentrations. Methane was also examined as a reductant, and neither copper oxide/alumina nor cerium oxide/alumina is active for selective catalytic reduction of NOx with methane up to 775 K.