Cu-Mn and Co-Mn catalysts synthesized from hydrotalcites and their use in the oxidation of VOCs

Mixed oxides of the Cu/Mn/Mg/Al and Co/Mn/Mg/Al type were obtained by means of the thermal decomposition of hydrotalcites, with manganese as the main active phase and with variations in their content by means of the addition of Cu or Co (molar ratio Cu/Mn or Co/Mn between 0.05 and 0.5). The effect of a second active phase on the material was evaluated in the total oxidation of three volatile organic compounds, VOCs (toluene, ethanol and butanol). The catalysts were characterized by means of X-ray fluorescence (XRF), X-ray diffraction (XRD), temperature-programmed reduction with hydrogen (TPR-H-2) and physisorption of nitrogen at 77 K. All the solids were active in the oxidation reaction of the VOCs, where the scale of difficulty to oxidize the different organic compounds evaluated was: butanol < ethanol < toluene. The use of mixed active phases optimized the physicochemical and catalytic properties compared with the system derived exclusively from manganese. The Co-Mn catalysts being the most active: this behavior is associated to the generation of amorphous phases and redox cycles as a consequence of the cooperative effect among the metals. (C) 2011 Elsevier B.V. All rights reserved.