四氯化碳催化加氢脱氯反应研究

单金属Pt催化剂在四氯化碳催化加氢反应中,载体和还原温度对反应性能影响较大,Pt/Al2O3显示出很高的对四氯化碳的转化率和对氯仿的选择性,同时表现出较高稳定性。而Pt/(Al2O3-TiO2)在对四氯化碳的转化率上略低于Pt/Al2O3,但显示出对四氯乙烯较高的选择性和催化剂稳定性。还原温度也是影响Pt催化剂性能的一个重要因素,高温还原可有效增大金属催化剂的晶粒,而大的晶粒缺电子程度要小于小晶粒,与*CCl3形成的键较弱有利于生成氯仿。同样,高温还原大的晶粒与表面碳和氯形成的键也弱于小晶粒,有利于抑制催化剂表面积炭和氯中毒,提高催化剂的稳定性。而加入甲醇作为稀释剂时,改变了产物的分布,降低氯仿的选择性,提高四氯乙烯的选择性。

Study on Hydrodechlorination of Carbon Tetrachloride

The performance of platinum supported on various metal oxides catalysts reduced at different temperature for hydrodechlorination of CCl_4 was investigated. Pt/Al_2O_3 exhibited high activity,high stability and high selectivity to CHCl_3.Pt/(Al_2O_3-TiO_2)showed high selectivity to CCl_2CCl_2 and stability while its activity was relatively lower than that of Pt/Al_2O_3.The reduction temperature of Pt catalysts played an important role.The Pt catalyst reduced at high temperature favored chloroform formation,because high reduction temperature effectively increased the metallic crystal size.The largercrystals were less electron-deficient than the smaller metallic crystallites,thus adsorbed *CCl_3 weakly and favored desorption of chloroform.In addition,the stability of the catalyst was improved because the larger metal crystallites weakened adsorption of carbon and chloride species and decreased their deposition Furthermore,the selectivity towards CCl_2 CCl_2 was increased by using CH_3 OH as thinner.