Key words: palladium, hexafluoroacetylacetonate, supercritical carbon dioxide, transition metals, catalysts, silica gel, acetylene, hydrogenation, selectivity
The kinetics of acetylene hydrogenation in the presence of supported catalysts containing transition metals (Fe, Co, Ni, Cu, Ag) and palladium was studied. The catalysts were prepared by deposition of palladium hexafluoroacetylacetonate from its solution in supercritical carbon dioxide onto a silica-based support, followed by heat treatment and reduction in a hydrogen flow at 500 °C. The support was pre-impregnated with solutions of transition metal nitrates. The catalytic properties of the bimetallic systems were compared with monometallic systems containing the same components. The mutual influence of palladium and the transition metal on their catalytic properties was demonstrated. A change in the kinetics of the formation of acetylene hydrogenation products (ethylene and methane) with increasing temperature was revealed, manifesting itself differently on bimetallic catalysts containing Cu and Ag and on Fe-, Co-, and Ni-containing catalysts. In the second case, a minimum acetylene conversion rate is observed at temperatures around 100 °C, while the selectivity for ethylene formation increases sharply at further temperature rise. The observed patterns are interpreted from the point of view of the existence on the surface of complex multicomponent catalytic systems of various forms of adsorption of reactants (hydrogen and unsaturated hydrocarbons), differing in adsorption strength and reactivity.
doi:10.34984/SCFTP.2025.20.4.004