Ag/MIL-101催化剂还原对硝基苯酚反应动力学

Kinetic analysis of catalytic reduction of 4-nitrophenol by Ag/MIL-101

采用双溶剂浸渍法制备得到了粒径为1.9nm±0.6nm高分散性的Ag/MIL-101催化剂。考察了该催化剂在过量NaBH4存在下,还原对硝基苯酚生成对氨基苯酚反应中的催化性能。本文通过研究催化剂浓度、底物浓度和温度对催化活性的影响,获得不同条件下的表观反应速率常数kapp,采用Langmuir-Hinshelwood吸附反应模型对所得动力学数据进行拟合,获得本征反应速率常数k,底物吸附常数K4-NP和KBH4,底物吸附焓、熵以及真实活化能EA,k等热力学参数。研究表明,诱导时间t0直接与该反应速率控制步骤的反应速率常数k有关。

Highly dispersed and ultrafine Ag/MIL-101 was prepared by double solvent method （DSM）. The size of the nanoparticles was about 1.9nm± 0.6nm and the total surface area of nanoparticles could be determined precisely. The catalytic activity was investigated by photometrically monitoring the reduction of 4-nitrophenol （4-NP） by an excess of NaBH4 in the presence of the nanoparticles. The kinetic data could be modelled to the Langmuir-Hinshelwood equation. The apparent reaction rate, k app was found to be related to the total surface of the nanoparticles, to the kinetic constant, k, related to the rate-determining step, and to the adsorption constants K4-NP and K BH4 for 4-NP and borohydride, respectively. The activation energy was obtained by fitting k app obtained at different temperatures. The study also showed that the induction time, to, is directly related to the reaction rate constant, k, of the controlling step.