铬(Ⅲ)离子催化铈(Ⅳ)离子氧化甲酸的反应动力学机理  

Kinetic and Mechanism of Chromium(Ⅲ) Catalysed Oxidation of Formic Acid by Cerium(Ⅳ)in Aqueous Sulphuric Acid Medium

作　　者：宋文玉[1] 降青梅[1] 

机构地区：[1]河北大学化学与环境科学学院,河北保定071002

出　　处：《山西大学学报（自然科学版）》2005年第1期52-55,共4页Journal of Shanxi University(Natural Science Edition)

摘　　要：在酸性介质中用氧化还原滴定法研究了铈( )离子在铬( )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( )和甲酸为一级,准一级速率常数kobs随催化剂[Cr( )]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,反应引发丙烯酰胺聚合,说明在反应中有自由基产生.提出了催化剂,底物和氧化剂间的反应机理,通过kobs与HSO-4的依赖关系,并结合Ce( )在溶液中的平衡,找到本反应体系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 aquesous sulphuric acid medium was studied by titrimetric techniques in the temperrature 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 k(obs) increases with the increase of [Cr(Ⅲ)]and [H\++],but decreases with the increase of [HSO_4\+-].Under the protection of nitrogen the reaction system induces polymerzation of acrylamide and it suggests the generation of free radicals.A mechanism involving a preequilibrium of an adduct formation among the substrate and catalyst was proposed.From the hydragensulphate dependence,Ce(SO_4)_2 has been found as the kinetically active species.Some rate constants together with the parameters were evaluated.

关 键 词：铬(Ⅲ)离子 铈(Ⅳ)离子 甲酸 催化剂 动力学机理 

分 类 号：O643[理学—物理化学]