Selective hydrogenation of acetylene over Pd/In2O3@SiO2: The effect of the catalyst reduction temperature

Abstract

Tuning the hydrogenation activity of Pd is an effective method to achieve selective hydrogenation of acetylene. The previous study shows that Pd has a strong interaction with In2O3, causing a significant change in the electronic structure of the palladium catalyst. Herein, Pd/In2O3@SiO2 was prepared by a deposition-precipitation method for selective hydrogenation of acetylene. After the reduction by flowing hydrogen, Pd-In intermetallic compounds can be formed. The concentration of the formed intermetallic compounds is closely associated with the reduction temperature. The Pd-In intermetallic compounds suppress the hydrogen activation ability of Pd and significantly weaken the adsorption of ethylene. Especially, a weak adsorption of di-σ-bonded ethylene is observed, which facilitates the desorption of ethylene and promotes the ethylene selectivity in the semi-hydrogenation of acetylene. The experimental study confirms that there exists an optimum reduction temperature (250 °C) for the formation of the Pd-In intermetallic compounds, with which ∼ 80 % ethylene selectivity and 100 % acetylene conversion have been achieved at 140 °C.