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

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.