Effect of catalyst pre-reduction temperature on the reaction of 1,2-dichloroethane and H2 catalyzed by SiO2-supported PtCu bimetallics

A combination of reaction kinetics experiments, temperature-programmed investigations and FTIR CO adsorption studies were used to understand the effect of catalyst pretreatment on the reaction of 1,2-dichloroethane and H2 catalyzed by SiO2 supported PtCu bimetallics prepared from metal chloride precursors. Higher initial and steady-state selectivities towards ethylene were obtained for catalysts with a Cu to Pt atomic ratio of 1, 2, and 3 after pre-reduction at 220 °C than after pre-reduction at 500 °C. For catalysts with a Cu to Pt atomic ratio of 4 and 5, the initial ethylene selectivity was higher after the 220 °C pre-reduction, but the steady-state ethylene selectivities were essentially the same. Based on the catalyst characterization results, the low temperature pre-reduction yields supported particles with Pt-rich cores covered with Cu-rich layers that are still well-chlorinated, whereas the high temperature pre-reduction yields particles both more metallic and with surfaces richer in Pt. The factors governing the evolution of the catalysts during the two different pretreatments are discussed as well as the impact catalyst pretreatment has on the macroscopic performance behavior.

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► Pt and Cu chlorides impregnated on silica.
► Hydrogen treatment at low temperature yields PtCu particles with Cu-rich surfaces.
► High temperature treatment yields particles with higher surface concentrations of Pt.
► Cu-rich surfaces catalyze ethylene from 1,2-dichloroethane and hydrogen.
► Pt-rich surfaces catalyze ethane from 1,2-dichoroethane and hydrogen.