Influence of Preparation Method on the Nanocrystalline Porosity of α-Al2O3 and the Catalytic Properties of Pd/α-Al2O3 in Selective Acetylene Hydrogenation

Nanocrystalline alpha-Al2O3 powder with average crystallite sizes of 34-68 not have been synthesized by three different methods, namely, solvothermal, sol-gel, and precipitation. Although the smallest crystallite, size of alpha-Al2O3 was obtained via the sol-gel synthesis, the alpha-Al2O3 sol-gel possessed the least amount of specific surface area and pore volume. A narrow pore size distribution with an average pore diameter of 15 not can be obtained via solvothermal method. whereas the precipitation method yielded alpha-Al2O3 with larger pore size and a wider pore size distribution. When used as a support for palladium catalysts, the alpha-Al2O3 solvothermal provided tire highest palladium dispersion and the best catalyst performance in selective hydrogenation of acetylene. The catalytic properties of Pd/alpha-Al2O3 solvothermal were improved, in terms of both acetylene conversion and ethylene selectivity. As shown by temperature program studies, the use of solvothermal-derived alpha-Al2O3 facilitated H-2 reduction at low temperature and the desorption of ethylene and CO.