A Highly Efficient and Selective Water-Soluble Bimetallic Catalyst for Hydrogenation of Chloronitrobenzene to Chloroaniline

Selective hydrogenation of chloronitrobenzene(CNB) to chloroaniline(CAN) catalyzed by water-soluble Ru/Pt bimetallic catalyst in an aqueous-organic biphasic system was studied. It was found that the catalytic activity increased obviously due to the addition of platinum. Ru/Pt bimetallic catalysts exhibited a strong synergistic effect when the molar ratio of Pt was in the range of 5%—80%. Under the mild conditions including a temperature of 25 ℃, a hydrogen pressure of 1.0 MPa and a Pt molar ratio of 20%, the conversion of p-chloronitrobenzene(p-CNB) reached 99.9%, with the selectivity to p-chloroaniline(p-CAN) equating to 99.4%. The Ru/Pt catalyst also showed high activity and selectivity for the hydrogenation of other chloro- and dichloro-nitrobenzenes with different substituted positions. In addition, the catalyst can be recycled five times without significant loss of activity.

Catalytic Hydrogenation of Aromatic Compounds in the Liquid Phase

Peculiarities of a liquid phase hydrogenation, namely lower diffusivity of components influencing the reaction rate and deactivation of catalysts by leaching, are discussed. A focus is on hydrogenation of aromatic compounds, whereas the following processes are evaluated： （l） partial hydrogenation of benzene to cyclohexene; （2） hydrogenation of aniline; （3） hydrogenation of diphenylamine; （4） preparation of aniline from nitrobenzene; （5） hydrogenation of chloronitrobenzenes; （6） hydrogenation of 4-nitrosodiphenylamine and 4-nitrodiphenylamine mixture. Processes （1） and （6） are typically carried out in the water-oil system. Generally, this type of system allows reaching a higher selectivity to desired products. In the case of hydrogenation of 4-nitrosodiphenylamine and 4-nitrodiphenylamine mixture, the water phase extracts a water soluble catalyst; which is recycled and used for condensation of aniline and nitrobenzene. Problems of reaction kinetics, as well as catalysts deactivation are here discussed.

均三甲苯胺合成工艺的改进

介绍了一种均三甲苯胺合成工艺的改进方法。以均三甲苯为原料,采用溶剂硝化反应制得硝基均三甲苯。研究了溶剂的选择与用量、反应温度、硝酸浓度等条件对硝化反应结果的影响。优化工艺条件为:乙酐为溶剂,乙酐用量微过量于理论值,硝化温度10~15℃,57%硝酸-乙酸溶液。此工艺条件下,硝化产物纯度达到98.5%以上,无二硝副产物生成,无废水产生。与传统混酸硝化法相比,本工艺具有环境友好、产品纯度高等优点。