Supported bimetallic Rh ?Cu/Al2O3 catalysts of different copper fractions (Xcu = Ncu/(Ncu + NRh) atomic ratios) were prepared by impregnating a monometallic 3.8 wt.%Rh/Al2O3 catalyst with copper. Benzene hydrogenation over the prepared catalysts was studied with a fixed bed reactor using a 1x10 5 Pa gaseous stream of 10% benzene in hydrogen. In a reaction-temperature range between 373 and 423 K, the observed reaction order varied significantly with their alloy phase on the surface of dispersed metallic crystallites. A rhodium-rich phase dominated the surface of bimetallic catalysts at low Xcu (< 0.3) and exhibited a higher activity than the mono-metallic rhodium. On increasing the copper fraction of bimetallic catalysts to Xcu > 0.5, the activity decreased dramatically because the surface of dispersed bimetallic crystallites was covered by a copper-rich phase.
