Total oxidation of VOCs on Au nanoparticles anchored on Co doped mesoporous UVM-7 silica

Abstract

Gold deposited on a cobalt containing siliceous mesoporous structure, UVM-7, presents a good catalytic performance in the total oxidation of propane and toluene. The presence of both gold and cobalt is necessary as bimetallic Au/Co-UVM-7 catalysts are remarkably more active than monometallic Au/UVM-7 or Co-UVM-7 catalysts. The improved activity of the bimetallic AuCo-samples if compared to gold free cobalt catalysts can be explained on the basis of the enhanced reducibility of some cobalt species in the presence of gold, which facilitates the redox cycle. This high reducibility of cobalt species in the bimetallic samples is probably due to the formation of Co3O4 domains at the gold–CoO interface perimeter, which are absent in the gold free cobalt containing UVM-7 catalysts. More interestingly, these catalysts have shown a high stability during the oxidation of propane and toluene, showing stable activity for at least 50h and 3 catalytic cycles. In fact, these catalysts have hardly modified their physicochemical properties after the catalytic runs. This stability has been explained on the basis of the architecture of the siliceous UVM-7 support. A deep characterization of all samples was carried out, before and after reaction, by means of N2 adsorption, Transmission Electron Microscopy, chemical analyses, X-ray diffraction, temperature programmed reduction and X-ray photoelectron spectroscopy, what allowed us to explain the observed stability.