Catalytic combustion of methane over mixed oxides derived from Co-Mg/Al ternary hydrotalcites

CoxMg3-x/Al composite oxides (xCoMAO-800) were prepared by calcination of CoxMg3-x/Al hydrotalcites (x = 0.0, 0.5,1.0,1.5,2.0,2.5,3.0, respectively) at 800 degrees C. The materials were characterized using XRD, TG-DSC, N-2 adsorption-desorption and TPR. The methane catalytic combustion over the xCoMAO-800 was assessed in a fixed bed micro-reactor. The results revealed that cobalt can be homogenously dispersed into the matrices of the hydrotalcites and determines the structure, specific surface areas and porosity of the derived xCoMAO-800 oxide catalysts. The thermal stability and homogeneity of the hydrotalcites markedly depends on the cobalt concentration in the hydrotalcites. The Co-based hydrotalcite-derived oxides exhibit good activity in the catalytic combustion of methane. The catalytic activity over the xCoMAO-800 oxides enhances with increasing x up to 1.5, but subsequently decreases dramatically as cobalt loadings are further increased. The 1.5CoMAO-800 catalyst shows the best methane combustion activity, igniting methane at 450 degrees C and completing methane combustion around 600 degrees C. The catalytic combustion activity over the xCoMAO-800 oxides are closely related to the strong Co-Mg/Al interaction within the mixed oxides according to the TG-DSC, TPR and activity characteristics. (C) 2009 Elsevier B.V. All rights reserved.