Preparation and Selective Acetylene Hydrogenation Catalytic Properties of Supported Pd Catalyst by the in Situ Precipitation-Reduction Method

Pd/MgAl-layered double hydroxide (LDH) was synthesized in situ on the surface of spherical Al2O3 to obtain a Pd/MgAl-LDH/Al2O3 catalyst, using hexamine as both a precipitant for LDH and a reductant for Pd2+. After calcination and reduction, another Pd/MgO-Al2O3 catalyst was obtained. As a comparison, the Pd/Al2O3 catalyst was prepared by the conventional impregnation method. Low-temperature N-2 adsorption-desorption, NH3 temperature-programmed desorption, and scanning electron microscopy results showed that Pd/MgAl-LDH/Al2O3 and Pd/MgO-Al2O3 catalysts possessed larger surface area, lower surface acidity, uniform Pd particle size, and specific Pd shape compared with the Pd/Al2O3 catalyst. The catalytic performances of the catalysts were then studied in the selective hydrogenation of acetylene. In comparison to Pd/Al2O3, Pd/MgAl-LDH-Al2O3 and Pd/MgO-Al2O3 catalysts exhibited not only higher activity due to the uniform size and specific shape of Pd particles which provided more catalytic active sites but also better selectivity because of the lower surface acidity and strong metal/support interaction.