羟基磷灰石负载钯催化剂用于H_2和O_2直接合成H_2O_2的动力学

Kinetics of synthesis of hydrogen peroxide directly from H_2 and O_2 over Pd/HAp catalyst

H2和O2直接合成H2O2过程绿色环保,反应具有原子经济性,是最有潜力的H2O2合成新方法之一。采用等量浸渍法,将Pd负载于羟基磷灰石(HAp)载体上,得到了高分散的Pd/HAp纳米催化剂,Pd平均粒径2.5 nm。运用幂指数模型,研究该催化剂在H2O2加氢及H2和O2直接合成反应中的动力学,计算得到H2O2加氢、H2O2和H2O的生成反应的表观活化能及O2、H2表观反应级数。结果表明低温及高O2分压有利于H2O2的生成,而高H2分压则有利于H2O的生成。

H2O2 synthesis directly from H2 and O2, as a ＂green process＂ and ＂atomic-economic reaction＂, is one of the most promising processes for replacing anthraquinone autoxidation process. In this paper, Pd/HAp （hydroxylapatite） catalyst was prepared by the conventional incipient-wetness impregnation method and highly dispersed Pd particles with an average size of 2.5 nm were obtained. Kinetic studies of H2O2 hydrogenation and direct synthesis of H202 were performed over a Pd/HAp catalyst and apparent activation energies and reaction orders with respect to H2 and O2 were calculated by power law functional models. Kinetic parameters indicated that the formation of H2O2 was favored at a lower reaction temperatures and higher O2 partial pressure, while higher H2 partial pressure would facilitate H2O formation.