Study of correlation between activity and structural properties of Cu-(Cr, Mn and Co)2 nano mixed oxides in VOC combustion

The correlation between structure and catalytic activities of Cu-(Cr, Mn and Co)2 mixed oxides synthesized by a sol–gel combustion method was investigated for the oxidation of 2-propanol. The catalysts were characterized by FTIR, XRD, XPS, TPR and UV–vis DRS. Although the same preparation conditions were used for all the systems, obtained samples presented different pureness degrees. The structural characterization by XRD revealed that copper-chromite was pure CuCr2O4, while copper-manganese and copper-cobalt mixed oxides resulted in a mixture of the spinel (CuMn2O4 and Cu0.15Co2.85O4, respectively) and copper oxide phases. UV–vis DRS results also indicated a larger presence of small crystallites of CuO in the copper-cobalt oxide. Copper-cobalt oxide exhibited the highest activity in 2-propanol combustion which is explained, as expected for a Mars van Krevelen mechanism, by its higher reducibility at the reaction conditions and by a possible synergistic effect between this mixed oxide and CuO particles.