铬离子催化铈离子氧化甲酸的双核配合物反应机理  

Dinuclear-complex Mechanism of Chromium(Ⅲ) Catalysed Oxidation of Formic Acid by Cerium(Ⅳ) in Aqueous Sulphuric Acid Medium

作　　者：刘红梅[1] 翟永清[1] 赵菁[2] 宋文玉[1] 杨国忠[1] 张楠[1] 

机构地区：[1]河北大学化学与环境科学学院,河北保定071002 [2]石家庄职业技术学院化工系,河北石家庄050081

出　　处：《河北大学学报（自然科学版）》2008年第1期57-62,73,共7页Journal of Hebei University(Natural Science Edition)

基　　金：河北大学自然科学基金资助项目(2003Z09)

摘　　要：在酸性介质中用氧化还原滴定法研究了铈（Ⅳ）离子在铬（Ⅲ）离子催化作用下，于30～45℃区间氧化甲酸的反应动力学．结果表明反应对铈（Ⅳ）和甲酸均为一级，准一级速率常数kobs随催化剂[Cr（Ⅲ）]增加而增大，亦随[H^＋]增加而增大，而随[HSO^-4]增加而减小．在氮气保护下，反应能引发丙烯腈聚合，说明在反应中有自由基产生．提出了催化剂、底物和氧化剂间生成双核配合物的反应机理．通过kobs与HSO4的依赖关系，并结合Ce（Ⅳ）在溶液中的平衡，认为本反应的动力学活性物种是Ce（SO4）2，还计算出一些速率常数及相应的活化参数．The kinetics of chromium（ Ⅲ） catalysed oxidation of formic acid by cerium（ Ⅳ ） in aqueous sulphuric acid medium was studied by titrimetric techniques of redox in the temperature range of 30- 45 ℃. The order is found to be unity with respect to both Ce（Ⅳ） and formic acid. It was found that the pseudo first order （[HCOOH]）〉〉[Ce（Ⅳ）]） rate constants kobs increases with the increase of [Cr（Ⅲ ） ] and [H^＋], but decreases with the increase of [ HSO4 ]. Under the protection of nitrogen the reaction system induces polymerzation of acrylonitrile indicating the generation of free radicals. Formation of a dinuclear complex involving the oxidant, catalyst and the substrate has been proposed in the reaction mechanism. From the relation between kobs and [HSO4 ], Ce（SO4）2 has been found as the kinetically active species. Some rate constants together with activation energy were evaluated.

关 键 词：铬(Ⅲ)离子 铈(Ⅳ)离子 甲酸 催化剂 

分 类 号：O611.3[理学—无机化学] O643[理学—化学]