Copper and manganese modified SBA-15 mesoporous Silica as catalysts for environmental protection

Full text: Transition metals have been recently considered as a good candidate for the preparation of low cost, environmentally friendly, highly active and with greater resistance to deactivation by poisoning catalysts, although some disadvantages, mainly related to their reducibility and dispersion, diminish the potential of their application. Generally, these disadvantages could be overcome significantly by promoting with a second metal, so that a cooperative effect between different metal species could enhance the oxygen mobility, the stabilization of more active species or to favor the redox cycles, which improve the catalytic behavior. The aim of current paper is to study the formation of active sites in bi-component copper and manganese materials with different phase composition, using SBA-15 mesoporous silica as a support. The samples were characterized by XRD, UV-Vis, FTIR, temperature programmed reduction (TPR) in hydrogen. Their catalytic properties were studied in methanol decomposition and total oxidation of ethyl acetate as representative catalytic tests, supplying reduction and oxidation reaction atmosphere, respectively. Both reactions have also essential impact, solving problems related to environment protection, supplying hydrogen as alternative fuel and VOCs elimination, respectively. The ordered porous structure of the SBA-15 mesoporous support facilitates the interaction between different metal oxide nanoparticles and increases their dispersion, due to the formation of a mixed oxide phase. The reductive reaction medium, formed during the methanol decomposition, leads to reduction/decomposition transformations with the mixed oxide phase, so the catalytic activity is higher for SBA-15 modifications. On the contrary, the ethyl acetate oxidation on SBA-15 binary materials is suppressed, due to the lower accessibility of metal oxide particles, located deeply into the micro-meso pores of the support. key words: transition metals, SBA-15 mesoporous silica, micro-mesopores