Pd和甲醛对Ag/C催化四氯化碳原位液相加氢脱氯性能的影响

采用100mL反应釜,在N2存在条件下,研究了Ag/C催化剂催化CCl4液相原位加氢脱氯反应,考察了助催化剂Pd以及助剂甲醛溶液对CCl4原位催化转化反应转化率和产物选择性的影响,并结合XRD、XPS表征技术分析了甲醛自身分解反应。结果表明,助催化剂Pd可以提高Ag/C催化剂的活性,以n(Pd)/n(Ag)为0.03的Pd-Ag/C催化剂的活性最高;但对产物CH2Cl2和CHCl3的选择性没有影响,二者选择性之比仍维持在6/4。甲醛的加入明显提高Ag/C催化剂上CCl4的转化率,同时也改变了产物分布;反应4h,CCl4转化率和CH2Cl2选择性均达到90%。甲醛主要起促进Ag/C催化剂表面Ag-Cl物种还原为Ag的作用。

Effect of Pd and Formaldehyde on In-Situ Liquid Phase Catalytic Hydrodechlorination of CCl4 Over Ag/C Catalysts

In-situ liquid phase catalytic hydrodechlorination of CCl₄ over Ag/C catalysts was studied. The effects of Pd and formaldehyde on the catalytic performance were investigated in a 100 mL autoclave with the presence of N₂.The decomposition reaction of formaldehyde combined with the analysis of XRD and XPS was also carried out.The results showed that Pd promoted the activity of Ag/C. The Pd-Ag/C catalyst with Pd/Ag molar ratio of 0.03 exhibited high catalytic activity in the conversion reaction of CCl₄. Selectivity of CH₂Cl₂ and CHCl₃ was not influenced by the addition of Pd. Parallel reaction products CH₂Cl₂ and CHCl₃ with a molar ratio of 6/4 were obtained in the catalytic dechlorination of CCl₄ over Pd-Ag/C in methanol solution. The conversion of CCl₄ catalytic conversion reaction over Ag/C increased and the distribution of product was changed when formaldehyde was added into the reaction system as promoter. Both the conversion of CCl₄ and selectivity of CH₂Cl₂ were up to 90% after 4 h reaction. Formaldehyde played an important role in promoting the transformation of surface Ag-Cl species to active Ag.