聚合物稳定的Ru-Pt/γ-Al_2O_3双金属催化剂催化2,5-二氯硝基苯选择性加氢

Selective Hydrogenation of 2,5-Dichloronitrobenzene Catalyzed by Polymer-Stabilized Ru-Pt/γ-Al_2O_3 Bimetallic Catalyst

制备了以聚乙烯吡咯烷酮(PVP)稳定的Ru- Pt/γAl2O3负载型双金属催化剂,用于2,5-二氯硝基苯中的硝基选择性加氢.考察了催化剂还原方法,反应温度、压力、时间和添加金属离子对反应的影响.结果表明,用乙醇还原的Ru- Pt/γAl2O3催化剂性能明显好于用其它方法还原的催化剂,在50℃和氢气压力1.0MPa的条件下反应1h,转化率为41.4%,生成2,5-二氯苯胺的选择性为63.5%.如果在上述反应条件下向该催化体系中加入Sn4+离子,反应的活性和选择性则大幅度提高,转化率达100%,选择性为77.6%,延长反应时间至4h,选择性可达99.3%,并且没有脱氯产物的生成.

The Ru-Pt/γ-Al_2O_3 bimetallic catalyst was prepared by different methods and its catalytic performance for the selective hydrogenation of 2,5-dichloronitrobenzene was investigated. It was found that the PVP-stabilized Ru-Pt/γ-Al_2O_3 ( n(Ru)/ n(Pt)=4) bimetallic catalyst III exhibited the highest catalytic activity. There was a synergistic effect between Ru and Pt in the hydrogenation of 2,5-dichloronitrobenzene. The addition of Ru could not only improve the catalytic activity, but also inhibit the occurring of dechlorination. The addition of other metal cations in reaction solution had obvious influence on both the activity and selectivity of the catalyst. The best result was obtained when Sn 4+ was used as the modifier for Ru-Pt/γ-Al_2O_3 catalyst. The conversion of 2,5-dichloronitrobenzene and the selectivity for 2,5-dichloroaniline increased from 41.4% and 63.5% to 100% and 77.6%, respectively, when Sn 4+ was added in ratio of n(Sn 4+)/ n(Ru+Pt)=1 under the reaction conditions of 50 ℃, 1.0 MPa, 1 h and substrate/(Ru+Pt) molar ratio of 1?000. The conversion and selectivity could be up to 100% and 99.7%, respectively, by prolonging the reaction time to 4 h. No dechlorinated aromatic amines were determined during the reaction process.