Pt催化N_2H_4还原U(Ⅵ)制备U(Ⅳ)过程中N_2H_4断键机制研究  

Study on Bond Breaking Mechanism for Process of U(Ⅳ)Produced by N_2H_4 Reducing U(Ⅵ)with Platinum as Catalyst

作　　者：张晓腾 李斌[2] 周贤明[2] 刘利生[2] 郝帅 蒋冬梅[3] 夏良树[1] 

机构地区：[1]南华大学核科学技术学院,湖南衡阳421001 [2]中国原子能科学研究院放射化学研究所,北京102413 [3]南华大学创新创业学院,湖南衡阳421001

出　　处：《原子能科学技术》2018年第2期240-246,共7页Atomic Energy Science and Technology

基　　金：国家自然科学基金资助项目(11575078)

摘　　要：为优化硝酸介质下Pt催化N_2H_4还原U(Ⅵ)制备U(Ⅳ)的工艺条件,确定此反应过程的控制步骤,有针对性地提高控制步骤的反应速率,以确定N_2H_4还原U(Ⅵ)制备U(Ⅳ)过程中的反应历程以及反应机理,通过实验研究确定了N_2H_4在Pt催化剂上的断键方式和分解机理。采用气相色谱法、分光光度法、滴定法及排水法对硝酸介质下Pt催化N_2H_4还原U(Ⅵ)制备U(Ⅳ)过程中的产物进行分析,确定反应过程中N_2H_4的断键机制。结果表明,硝酸介质下Pt催化N_2H_4还原U(Ⅵ)制备U(Ⅳ)反应过程中没有叠氮酸、氮氧化物及氢气生成,产物主要是N_2,生成的N_2的量与消耗的N_2H_4的量接近1∶1;当存在U(Ⅵ)时,生成的NH_4^+产量较低,当U(Ⅵ)反应完全后,NH_4^+的产生速率急剧增大;N_2H_4以N—N断键和N—H断键两种方式共存;反应温度升高有利于加快由U(Ⅵ)制备U(Ⅳ)还原反应的进行。In order to optimize the process conditions of U(Ⅳ)produced by N_2H_4 reducing U(Ⅵ)with platinum as catalyst in the nitric acid environment,determine the control steps of the reaction process,improve the rate of controlling step in the reaction,and determine the reaction path and reaction mechanism,it is necessary to confirm the manner of bond breaking and decomposition mechanism of the N_2H_4 with Pt as catalyst.In order to determine the bond breaking mechanism of N_2H_4 in this process,gas chromatography,spectrophotometry,titration and drainage method were used in this paper to analyze the product in the process of U(Ⅳ)produced by N_2H_4 reducing U(Ⅵ)with Pt as catalyst in the nitric acid environment.The results show that there is no hydrazoic acid,nitrogen oxides or hydrogen product in the process.The main product is N_2,and the consumption ratio of N_2 to N_2H_4 is close to 1∶1.When there is U(Ⅵ),the yield of NH_4^+ is low,and the production rate of NH_4^+ increases sharply when the U(Ⅵ)reaction is complete.N—N bond breaking and N—H bond breaking coexist.Increasing temperature is conducive to speed up the reduction reaction.

关 键 词：N2H4 铀 铂 催化 断键机制 

分 类 号：O614.62[理学—无机化学]