MODIFICATION OF RH/AL2O3 CATALYSTS BY COPPER DEPOSITION AND SULFUR ADSORPTION

Rh-Cu bimetallic catalysts were prepared by catalytic reduction under hydrogen of Cu2+ on Rh/Al2O3 parent catalysts, and were characterized using infrared spectroscopy of adsorbed carbon monoxide and hydrogenolysis of methylcyclopentane. Significant changes in the IR spectra as well as in the reactivity were observed upon addition of copper to Rh only if Rh/Al2O3 was well dispersed. This suggests that copper is selectively deposited on Rh surface atoms with a low coordination number. Comparison of methylcyclopentane conversion and IR spectral results for Rh-S and Rh-Cu showed that charge transfer could take place from Rh atoms at the phase boundary to sulfur and from copper to partially oxidized rhodium.