Physicochemical Characterization and H2-TPD Study of Alumina Supported Ruthenium Catalysts

Abstract

A series of alumina supported ruthenium catalysts, which prepared by hydrogen treatment or hydrazine reduction, were characterized by N2 adsorption, X-ray diffraction (XRD), X-ray fluorescence (XRF), CO chemisorption, and Temperature-programmed desorption of hydrogen (H2-TPD). In contrast to the samples with conventional hydrogen reduction, there was almost no residual chlorine in the samples using RuCl3 as precursor with hydrazine treatment. Furthermore, the dissolved aluminum could be removed much more easily in basic solution, which led to the higher BET surface and pore volume of hydrazine-reduction catalysts. Therefore, the active phase (Ru metal) would not be contaminated. Three main peaks, which occurred at about 150, 375, and 650 °C, respectively, were observed in the H2-TPD profiles of Ru/Al2O3 catalysts with a high amount of residual chlorine. A new peak of desorption hydrogen centering at 240 °C, which was completely suppressed by the high amount of residual chlorine, might appear in the profiles of the samples with the washing procedure following hydrogen reduction or hydrazine treatment. The peaks with the desorption temperature lower than 500 °C were relative with dissociatively adsorbed hydrogen and spillover hydrogen simultaneity, and the peak at above 500 °C was caused by spillover hydrogen and would be stabilized by hydroxyl groups on alumina surface.