Abstract: The bimetallic catalyst Ru-Pt/γ -Al₂O₃ was prepared by impregnating H₂PtCl₆ and RuCl₃ aqueous solution in the presence of PVP(40 000). Its catalytic performance in selective hydrogenation of p -chloronitrobenzene ( p -CNB) was studied. The results indicate that the activity of Ru-Pt/ γ -Al₂O₃[n(ruthenium):n(platinum)=4:1] is much higher than that of Ru/ γ -Al₂O₃,while the amount of dehalogenation product(aniline) and other by-products are much fewer than that by using Pt/ γ -Al₂O₃ as the catalyst. There is synergistic effect of ruthenium and platinum in bimetallic catalyst for selective hydrogenation of p -CNB. Under the reaction conditions t =50 ℃, p H₂ = 1.0 MPa, reaction time 60 min,n(substrate):n(total amount of metal content)=1000:1,the conversion of p -CNB and the selectivity to p -chloroaniline( p -CNA) by using Ru-Pt/γ -Al₂O₃ as the catalyst are 48.2% and 85.9%,respectively. The effect of other metal cations(introduced to the reaction system with the corresponding metal chloride solution) on the reaction was investigated. It was found that catalytic performance of Ru-Pt/ γ -Al₂O₃ could be greatly improved by modfication of some metal cations. When Co²⁺ and Ni²⁺ were used as modifiers for the catalyst Ru-Pt/ γ -Al₂O₃ under above mentioned reaction conditions,the conversions of p -CNB increase to 74.5% and 87.8%,as well as the selectivities of p -CAN increase to 98.9% and 99.4%,respectively. Fe³⁺ and Sn⁴⁺ were the best modifiers for Ru-Pt/ γ -Al₂O₃ under the same reaction conditions. The conversions of p -CNB and the selectivities of p -CAN can reach 100% and >99.0%,respectively. However,the catalysts can be poisoned by Zn²⁺ and Sn²⁺ .

Key words: Ru-Pt/γ-Al₂O₃ bimetallic catalyst, p -Chloronitrobenzene, Selective hydrogenation, Metal cations modifiers