Mn(Ⅱ)催化硝酸氧化草酸反应动力学及机理

doi:10.19894/j.issn.1000-0518.200320

摘要/Abstract

摘要： 为明确反应机理和反应历程,优化反应工艺条件,开展了在硝酸体系中以草酸为还原剂、Mn²⁺为催化剂催化硝酸氧化草酸的动力学研究。通过考察草酸浓度、硝酸浓度等反应条件对反应过程的影响,确定了该反应的初始动力学速率方程为:-dc(H₂C₂O₄)/dt=kc^0.7840(H₂C₂O₄)c^0.3192(HNO₃),在393 K时,反应速率常数k=3.0×10^-3 (mol/L)^-0.1032/min。研究了Mn²⁺和亚硝酸钠浓度对反应速率的影响,结果表明,Mn²⁺浓度在0.008~0.020 mol/L范围内,Mn²⁺的反应级数为0.6742,Mn²⁺和亚硝酸钠浓度的增加对初始草酸消耗速率有促进作用,并在此基础上推测了可能的反应机理,认为Mn²⁺促进了亚硝酸的生成,产物亚硝酸与草酸发生次级氧化还原反应从而促进了草酸的分解。

关键词: 草酸, 锰(Ⅱ), 硝酸, 催化氧化, 动力学

Abstract: A kinetic study on the oxidation of oxalic acid by nitric acid using Mn²⁺ as the catalyst was carried out to clarify the reaction mechanism and reaction process, and optimize the process conditions. By investigating the influence of concentrations of oxalic acid and nitric acid on the reaction process, the initial kinetic rate equation of the reaction is obtained: -dc(H₂C₂O₄)/dt=kc^0.7840(H₂C₂O₄)c^0.3192(HNO₃), and the reaction rate constant is k=3.0×10^-3 (mol/L)^-0.1032/min at 393 K. The results show that when the Mn²⁺ concentration is in the range of 0.008~0.020 mol/L, the reaction order of Mn²⁺ is 0.6742 and the increase of concentrations of Mn²⁺ and sodium nitrite promotes the initial consumption rate of oxalic acid. On this basis, the possible reaction mechanism is speculated, and it is believed that Mn²⁺ promotes the production of nitrous acid, and the secondary oxidation and reduction of nitrite and oxalic acid promote the decomposition of oxalic acid.

Key words: Oxalic acid, Manganese(Ⅱ), Nitric acid, Catalytic oxidation, Dynamics

中图分类号:

王玉婷, 张晓腾, 李先俊, 夏良树. Mn(Ⅱ)催化硝酸氧化草酸反应动力学及机理[J]. 应用化学, 2021, 38(6): 685-692.

WANG Yu-Ting, ZHANG Xiao-Teng, LI Xian-Jun, XIA Liang-Shu. Kinetics and Mechanism of Oxalic Acid Oxidation by Nitric Acid Catalyzed by Mn(Ⅱ)[J]. Chinese Journal of Applied Chemistry, 2021, 38(6): 685-692.

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