SELECTIVE HYDROGENATION OF ACETYLENE OVER TiO2 SUPPORTED Pd-Au AND Pd-Cu CATALYSTS PREPARED BY STRONG ELECTROSTATIC ADSORPTION AND ELECTROLESS DEPOSITION

Abstract

In the present work, the addition of Au or Cu on the performances of Pd/TiO2 was investigation in the selective hydrogenation of acetylene for improve performance of catalyst. Pd was deposited on the titania support by the strong electrostatic adsorption (SEA) method, which can attain high dispersion of Pd. The addition of a second metal on Pd/TiO2 was done by the electroless deposition (ED) method and compared with the incipient wetness impregnation (IM) method. The catalysts were characterized by hydrogen titration of oxygen-precovered on Pd, X-ray diffraction (XRD), Infrared spectroscopy of adsorbed CO (CO-IR), X-ray photoelectron spectroscopy (XPS), and transmission electron microscopy (TEM). The Pd/TiO2 catalyst prepared by SEA showed highly dispersion of Pd at 38% at 1.29 wt.% Pd. The preparation by ED method showed incremental coverage of the second metal on Pd, while IM method had accumulation of second metal onto both Pd and TiO2 support, the small ensembles of Pd sits found in ED samples promoted acetylene adsorption as π-bonded species that favored hydrogenation to ethylene. The Cu-Pd/TiO2 catalysts prepared by ED showed higher ethylene selectivity and hydrogenation activity than the Au-Pd/TiO2 catalysts. The results from CO-IR suggested that Cu selective deposited preferentially onto the low-coordination sites than Au which inhibited fully hydrogenation of ethylene to ethane.