高分子微凝胶负载镍催化剂及催化还原芳硝基化合物

以高分子微凝胶为载体, 先通过浸渍法在载体上引入少许的镍金属种子, 再通过化学法镀镍, 在种子载体上镀上大量镍, 制备出微凝胶负载Ni催化剂。 以水合肼为氢给体, 使用此类催化剂催化还原芳香族硝基化合物呈现出较高的活性。 经动态光散射法检测, 这种微凝胶催化剂的流体力学直径为411.9 nm。 高分辨透射电子显微镜和X射线光电子能谱分析表明, 所制得的催化剂中Ni主要是以NiO的形式存在。 以硝基苯为原料考察了水合肼的用量对反应的影响, 结果表明, 底物与水合肼的摩尔比为1:15最佳。 在优化条件下, 硝基苯衍生物的还原均能得到高产率的芳香胺。 动力学研究结果表明, 硝基苯氢转移反应的活化能为133.7 kJ/mol, 焓变为130.9 kJ/mol, 熵变为102.8 J/(mol·K)。

Polymer Microgel-Supported Ni Catalysts and Their Catalytic Reduction of Aromatic Nitro Compounds

Polymer microgel-supported Ni particles were prepared by impregnation first with a small amount of Ni seeds on microgels, then by electroless nickel plating on the seeded microgels. The nickel particles exhibit good catalytic activity in hydrogen transfer reactions of aromatic nitro compounds with hydrazine hydrate as the hydrogen donor. Dynamic light scattering characterization shows that Ni embedded gel particles have hydrodynamic diameters of approximately 411.9 nm. Results from high resolution transmission electron microscopy and X-ray photoelectron spectroscopy demonstrate that Ni is mainly in the form of NiO. The effect of the hydrazine hydrate amount on the reaction was examined for the reduction of nitrobenzene. The result show that a molar ratio of 1:15 for the substrate to hydrazine hydrate is optimal for the reduction. The optimized conditions are used for reduction of a series of aromatic nitro compounds, giving rise to high yields of aromatic amines. Kinetic analysis shows that the Arrhenius activation energy is 133.7 kJ/mol, the enthalpy is 130.9 kJ/mol, and the entropy is 102.8 J/(mol·K).