Effects of MgO doping in Pd/γ-Al2O3 catalysts forthe hydrogenation of perfluoro olefin

Abstract

Gamma alumina is widely utilized for preparing the supported noble metal catalysts for the hydrogenation reaction. It is an effective strategy to improve the catalytic performance of catalysts via modifying gamma alumina with alkaline earth metal to regulate its surface acidity and electronic properties. Herein, Pd catalysts supported by Al2O3 and Mg-modified Al2O3 are synthesized via the wet impregnation method, and the effects of MgO doping on the structure, composition, and surface acidity of Pd/γ-Al2O3 catalysts are investigated via X-ray diffraction patterns (XRD), Transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS) and Temperature programmed desorption (TPD). The results show that Pd/MgO-Al2O3–2 (γ-Al2O3 modified with 2 wt% Mg) has more metallic state palladium and weak acid sites and exhibits the best catalytic performance for the hydrogenation of perfluoro-4-methyl-2-pentene (D1). Density functional theory (DFT) calculations on Pd/Al2O3 and Pd/MgO-Al2O3–2 catalysts are also performed to further explore the mechanism of D1 hydrogenation. The studies for Gibbs free energy of the potential reaction steps and intermediates reveal a complex process to generate the target product C6F12H2, and the rate-determining-step is the addition of the first hydrogen on the second carbon of perfluoro-4-methyl-2-pentene molecule.