Cu-Mn Hydroxyapatite Materials for Toluene Total Oxidation

The oxidation of 800 ppmv toluene in air has been investigated over CuMnOx ((Cu+Mn) loading: 10 wt%) dispersed on hydroxyapatite (Hap: Ca-5(PO4)(3)(OH)) with different molar Cu/Mn compositions (2; 1; 0.5) to be compared with the corresponding supported single transition metal oxide catalysts. The solids have been prepared by wet aqueous co-impregnation method followed by a calcination at 400 degrees C for 4 h and physicochemically characterized by different techniques. The catalytic performances of the supported Cu-Mn oxide catalysts revealed the existence of a synergetic effect in terms of activity and selectivity towards CO2 through the formation of Cu-Mn mixed oxides. The strongest synergetic effect is observed for a Cu/Mn molar ratio of 2 as confirmed by the standardized conversion rate values determined at 190 degrees C (r(190)) which followed the decreasing sequence (/10(-2) h(-1)): Cu(2)MnHap (2.57)>CuMnHap (2.04)>CuMn(2)Hap (1.59)>MnHap (1.13)>CuHap (0.13). The highest activity of Cu(2)MnHap can be explained by a better reducibility of the active phase in line with a high density of Cu-O-Mn interactions at the outermost layers as shown by ToF-SIMS results.