ESR法研究pH值对Pt催化N2H4断键的影响机制

为明确酸性条件下Pt催化N₂H₄还原U（Ⅵ）制备U（Ⅳ）的反应历程和反应机理，有针对性地提高其反应速率、优化工艺流程，本文采用电子自旋共振(ESR)法实验研究?NH2转化为?OH的机理及0.25 mol/L和0.5 mol/L N₂H₄浓度条件下不同酸度的高氯酸体系中Pt催化N₂H₄分解过程中产生的自由基，确定反应过程中pH值对N₂H₄断键的影响机制。结果表明，在高氯酸介质中，Pt催化N₂H₄分解反应体系中检测到的?OH是由N₂H₄分解产生的?NH₂转化而来；该反应体系中酸度会对N₂H₄分解产生影响，在酸度逐渐降低的过程中Pt催化N₂H₄分解的反应速率表现为先增大后减小的趋势，其中在pH=1～2之间时Pt催化N₂H₄分解反应最为迅速。

Study on Mechanism for pH Affecting Hydrazine Bond Breaking with Platinum as Catalyst by ESR Method

In order to determine the reaction process and reaction mechanism of U(Ⅳ) produced by hydrazine reducting U(Ⅵ) with platinum as catalyst in the nitric acid environment, improve the reaction rate, and optimize the process flow, the effect of pH value on hydrazine bond breaking with Pt as catalyst was studied. The electron-spin resonance (ESR) method was used to study the mechanism of conversion of?NH₂ to?OH, and analyze the free radicals generated during the decomposition of hydrazine catalyzed by Pt in perchloric acid systems with different acidity for 0.25 mol/L and 0.5 mol/L hydrazine solutions respectively to determine mechanism for pH affecting hydrazine bond breaking. The results show that in the perchloric acid environment, the?OH detected in the Pt-catalyzed hydrazine decomposition reaction system is converted from?NH₂ produced by the decomposition of hydrazine. The acidity of the reaction system will affect the decomposition of hydrazine. During the process of decreasing acidity, the reaction rate of Pt-catalyzed hydrazine decomposition reaction will increase first and then decrease, and the decomposition reaction is the fastest between pH=1-2.