Copper‐Based Catalysts Supported on Highly Porous Silica for the Water Gas Shift Reaction

Cu-based nanoparticles, supported on either a silica aerogel or cubic mesostructured silicas obtained using two different synthetic protocols, were used as catalysts for the Water Gas Shift reaction. The obtained nanocomposites were thoroughly characterized before and after catalysis using N2 adsorption-desorption measurements at -196 °C, transmission electron microscopy, wide-angle and low-angle X-ray diffraction. It was found that the samples before catalysis contain nanoparticles of copper oxides – either CuO or Cu2O – while the formation of metallic copper nanoparticles, constituting the active catalytic phase, is observed either using a pretreatment in reducing atmosphere or directly during the catalytic reaction due to the presence of CO. A key role in determining the catalytic performances of the samples is played by the ability of the different matrices in promoting a high dispersion of Cu metal nanoparticles. The best catalytic performances are obtained with the aerogel sample, which also exhibits constant CO conversion values at constant temperature and quite a reproducible behaviour after subsequent catalytic runs. On the other hand, in the catalysts based on cubic mesostructured silica the detrimental effects related to sintering of Cu nanoparticles are avoided only on the silica support which is able to produce a reasonable dispersion of the copper nanophase.