Ni-B非晶态合金催化加氢制备氯代苯胺

Catalytic Hydrogenation of Chloronitrobenzene over Ni-B Amorphous Alloy Catalyst

采用水合肼和硼氢化钾为共还原剂,适当比例的甲醇、乙醇和水的混合物为溶剂,在333 K下制得负载催化剂P1。XRD、TEM、SAED测定结果表明,该催化剂是一种纳米级非晶态合金。将P1催化剂用于邻氯硝基苯加氢反应,在底物100%转化时,生成邻氯苯胺的选择性达到94.3%。对一系列氯代硝基芳烃化合物在P1催化剂上的催化加氢反应进行了考察,得出脱氯顺序依次为:2-氯-5-硝基甲苯>邻氯硝基苯>间氯硝基苯=对氯硝基苯>2,5-二氯硝基苯,分析了不同氯代硝基苯的结构与脱氯的关系,认为在该催化剂上脱氯的主要原因,是生成的氯代苯胺在催化剂表面的吸附。讨论了金属添加剂(Cr、Mn、Fe、Co、Cu、Mo、Zn、La)对P1催化剂催化加氢制备邻氯苯胺的影响,发现添加Cu、Fe能提高催化剂的选择性,在底物基本转化时,选择性由不加金属添加剂时的94.3%,分别提高到97.2%和97.6%。

The supported catalyst P1 was prepared using hydrazine hydrate and potassium borohydride as co-reducers in a mixed solvent consisting of methanol, ethanol and water in proper proportion. The catalyst is a kind of nanosized amorphous alloy as characterized by TEM, XRD and SAED. P1 catalyst in the hydrogenation of o-chloronitrobenzene showed 94.3% selectivity to o-chloroaniline when all the substrate was converted. Through the hydrogenation of a series of chloronitroarenes on P1, the dechlorination sequence 2-chloro-5-nitrotoluene〉o-chloronitrobenzene〉m-chloronitrobenzene = pchloronitrobenzene〉2,5-dichloronitrobenzene was observed. The relationship between the structure of different chloronitrobenzenes and the dechlorination was analyzed, and it is suggested that the dechlorination is mainly due to absorption of chloronitrobenzene substrate on the surface of the catalyst. The effect of different metal additives （ Cr, Mn, Fe, Co, Cu, Mo, Zn, La） on the catalytic properties was investigated. As can be seen from the results, the catalysts with Cu or Fe additive have higher selectivity （97.2% or 97.6% respectively at 100% conversion of the substrate than that without additive.