铬(Ⅲ)离子催化铈(Ⅳ)离子氧化异丁醇的反应动力学及机理  

Kinetics and Mechanism of Chromium(Ⅲ) Catalysed Oxidation of Isobutyl Alcohol by Cerium(Ⅳ) in Aqueous Sulphuric Acid Medium

作　　者：宋文玉[1] 降青梅[1] 刘亚东[1] 刘红梅[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：《河北大学学报（自然科学版）》2004年第6期594-599,共6页Journal of Hebei University(Natural Science Edition)

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25～40℃区间氧化异丁醇的化学反应动力学.结果表明反应对铈(Ⅳ)离子为一级,对异丁醇的表观反应级数为正分数.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,但随[HSO4-]增加而减小.在氮气保护下,反应不能引发丙烯酰胺聚合,说明在反应中没有自由基产生.提出了催化剂、底物和氧化剂间生成双核加合物的反应机理,通过kobs与HSO4-的依赖关系,找到本反应体系的动力学活性物种是Ce(SO4)2+,并计算出平衡常数、速控步骤的速率常数及相应的活化参数.The kinetics of chromium(Ⅲ) catalysed oxidation of isobutyl alcohol by cerium(Ⅲ) in aqueous sulphuric acid medium was studied by titrimetric techniques in the temperature range of 25～40 ℃. The reaction rate showed first order dependence in oxidant, and positive fractional order dependence in isobutyl alcohol. It was found that the pseudo first order ([(CH_3)_2CHCH_2OH][Ce(Ⅳ)])rate constants k_(obs) increases with the increase of [Cr(Ⅲ)] and [H^+], but decreases with increase of [HSO_4^-]. Under the protection of nitrogen, the reaction system does not induce polymerization of acrylamide, indicating the generation of no free radicals. A mechanism involving a pre-equilibrium of an adduct formation among the oxidant, substrate and catalyst has been proposed. From the hydrogensulphate dependence,Ce(SO_4)^(2+) has been found as the kinetically active species. The pre-equilibrium constants, rate constants of the rate-determining step together with the parameters were evaluated.

关 键 词：铬(Ⅲ)离子 铈(Ⅳ)离子 异丁醇 催化剂 动力学及机理 

分 类 号：O611.3[理学—无机化学]