Enhancement of Metal Dispersion and Selective Acetylene Hydrogenation Catalytic Properties of a Supported Pd Catalyst

Abstract

Pd(NH3)2Cl2/MgAl-CO32−-layered double hydroxide (LDH) precursor has been synthesized in situ on the surface of spherical Al2O3 using urea as a precipitant. Pd(NH3)2Cl2 particles were observed highly dispersed on the surface of MgAl-LDH/Al2O3 by Scanning electron microscopy. After calcinations, a PdO/MgO-Al2O3 catalyst precursor was obtained. In the process of calcination, the MgAl-LDH crystallites grown on the surface of Al2O3 prevented the migration and aggregation of Pd2+, therefore the PdO particles with uniform size still highly dispersed on the surface of MgO-Al2O3. As a comparison, a PdO/Al2O3 catalyst precursor was prepared by a conventional impregnation method. Low temperature N2 adsorption−desorption, temperature programmed desorption of hydrogen and ammonia showed that PdO/MgO-Al2O3 possessed larger surface area, higher metal dispersion, and lower surface acidity compared with PdO/Al2O3. After reduction, the selective hydrogenation of acetylene was studied over Pd/MgO-Al2O3 and Pd/Al2O3 catalysts. The Pd/MgO-Al2O3 exhibited higher activity, selectivity and better stability.