Selective Hydrogenation of Acetylene on Pd Fiberglass Catalysts

Abstract

Key properties of silicate glasses are determined. These include the ability to stabilize the highly dispersed Pd nanoparticles in a bulk of fiberglass (FG), the high solubility of acetylene and hydrogen, and their increased mobility. Together, these ensure the high activity and selectivity of Pd/FG catalysts during the hydrogenation of acetylene in an excess of ethylene in a wide range of acetylene conversion up to its complete conversion. It is found that for a wide range of mono- and bimetallic systems, including catalysts with single palladium atoms, the TOF value depends weakly on the dispersion of the palladium and nature of the support, i.e., the reaction can be considered structure-insensitive. A tendency toward a lower frequency of turnover is nevertheless observed upon moving to single palladium atoms, due likely to the rate of hydrogen dissociation or its spillover slowing down. Based on kinetic isotope data, undesirable contributions to the selectivity of process resulting from the hydrogenation of acetylene and ethylene from the gas phase to ethane are determined quantitatively. The high selectivity of bimetallic alloyed systems with single palladium atoms is due to the low rate of hydrogenation of weakly absorbed ethylene to ethane, while that of Pd/FG catalysts results from the complete elimination of the hydrogenation of ethylene from the gas phase.