Catalytic combustion of toluene over mixed Cu-Mn oxides

摘要

The influence of the synthesis pH and of the Zn and/or Al additives on the Cu-Mn precursors,obtained by co-precipitation at a constant pH from aqueous solutions of appropriate nitrates at (Cu + Zn)/(Mn + Al)ratio equal 2,was investigated.The relative content of Mn increased with the pH of precipitation.Depending on the sample composition the identified crystalline phases included layered hydroxy double salt,hydrotalcite-like structure,CuO and ZnO.Some precursors had strongly amorphous character.Calcination of the precursors at 673 K resulted in mixed oxides,in which CuO of various degrees of crystallinity could be identified.The Mn-containing phases remained amorphous.All calcined materials proved extremely active in catalytic combustion of toluene.Some catalysts reached 100% conversion already at 4O_3 K.High conversions observed in the low temperature regime were partially due to the strong sorption of toluene.In the catalysts containing Al additive this effect was suppressed.