水溶性钌络合物催化卤代芳香硝基化合物选择性加氢的研究

Selective Hydrogenation of Haloaromatic Nitro- Compounds Catalyzed by Water-Soluble Ru Catalyst AC-1

研究了水/有机两相催化体系中,水溶性钌络合物催化剂AC 1催化卤代芳香硝基化合物中硝基的选择性加氢反应.以对 氯硝基苯为底物,考察了表面活性剂种类及浓度、反应温度、氢压、催化剂浓度和反应时间等对反应转化率和选择性的影响.实验结果表明,阳离子表面活性剂对反应有明显的影响,其中以添加十六烷基三甲基溴化铵(CTAB)效果最好.当反应条件为90℃,氢压4.0MPa时,反应5h,对 氯硝基苯转化率可达100%,生成对 氯苯胺的选择性可达99.9%.该催化体系对其它卤代芳香硝基化合物的选择性加氢也具有很高的活性和选择性.

Aromatic haloamines are of great importance for the production of many fine chemicals,such as dyes,herbicides and pesticides. The preparation of them are either through the Bechamp's procedure or through selective hydrogenation over heterogeneous catalyst or homogeneous catalyst.In recent years,the use of watersoluble transition metal complexes in biphasic (aqueous/organic) catalysis has attracted much attention because this new approach has largely simplified the separation of catalysts from products.In research,selective hydrogenation of haloaromatic nitrocompounds catalyzed by watersoluble Ru catalyst AC1 in the biphasic catalytic system(aqueous/organic phase) has been studied. With pClC6H4NO2 as substrate,the influences of surfactant concentration,reaction temperature,H2 pressure,catalyst concentration and the reaction time on the activity and selectivity have been investigated. It has been found that the reaction rate is obviously promoted by the addition of cationic surfactants,among which cetyltrimethylammonium bromide (CTAB) performs the best. Under the conditions of 90℃,pH2=4.0MPa,reaction time 5h,the conversion of pClC6H4NO2 and the selectivity for pClC6H4NH2 are 100% and 99.9% respectively,and only a small amount of dehalogenation product (aniline) is formed. It has also been found that the Ru catalytic system exhibits high activity and selectivity for the hydrogenation of other haloaromatic nitrocompounds with different substituents and substituted positions.