以PdCl2为前驱体,采用浸渍法制备了Pd/C催化剂,并在发烟硫酸中考察了其催化甲烷选择氧化反应的性能,采用X射线粉末衍射、X射线光电子能谱、高分辨透射电镜和CO吸附等方法对催化剂进行了表征.甲烷选择氧化反应得到的主产物硫酸单甲酯经水解后得到甲醇,在5%Pd/C催化剂、Pd用量30μmol、反应温度180℃、反应压力4.0 MPa、反应时间4 h和发烟硫酸中SO3含量为50%的优化工艺条件下,甲烷转化率为23.6%,甲醇的选择性和收率分别为69.5%和16.4%,在一定程度上可实现催化剂的多次重复使用.Pd/C催化剂上的甲烷选择氧化反应可能遵循亲电取代机理,催化性能与Pd负载量、Pd粒子尺寸和分散度等有关.The selective oxidation of methane to methanol over Pd/C catalysts generated from a PdCl2 precursor was investigated in oleum.Characterization of the catalysts was performed by X-ray diffraction,X-ray photoelectron spectroscopy,high-resolution transmission electron microscopy,and CO adsorption.The major product in the oxidation reaction was methyl bisulfate,which was then hydrolyzed into methanol.Methane conversion of 23.6% with methanol selectivity of 69.5% and yield of 16.4% was achieved under the optimum conditions of 5%Pd/C,30 μmol Pd,reaction temperature 180 ℃,methane pressure 4.0 MPa,reaction time 4 h,and 50% sulfur trioxide concentration.After facile separation with the reactants and pretreatment,the catalyst could be reused several times with considerable stability.The selective oxidation of methane catalyzed by Pd/C catalysts in oleum possibly involved an electrophilic substitute mechanism.The catalytic performance was related to the Pd loading,dispersion,and particle size.国家自然科学基金(20473065);; 福建省科技重大专项(2005HZ01-3
