hybrid Quantum Chemical Studies for the Reaction Mechanism and the Control of Chemical Processes in the Supercritical Water

超临界水中反应机理和化学过程控制的混合量子化学研究

基本信息

批准号：
13450327
负责人：
NITTA Tomoshige
金额：
$ 8.51万
依托单位：
Osaka University
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (B)
财政年份：
2001
资助国家：
日本
起止时间：
2001 至 2002
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/en/grant/KAKENHI-PROJECT-13450327/
关键词：
Hybrid ab-initio Molecular Dynamics method Supercritical Water Reaction Mechanisms Solvent Effect Oxidation Ethanol Water Catalyst Proton Transfer ホルムアルデヒド

项目摘要

(1) Ab initio density functional theory calculations have been performed to investigate the catalytic role of water molecules in the oxidation reaction of ethanol : CH_3CH_2OH + nH_2O -> CH_3CHO + H_2 + nH_2O (n = 0, 1, 2 ). The results show that the potential energy barrier for the reaction is 88.0 kcal/mol in case of n =0, while it is reduced by 〜 34 kcal/mol when two water molecules are involved (n = 2 ) in the reaction. As a result, the rate constant increases to 3.31x10^<-4>s^<-1>, which shows a significant catalytic role of water molecules in the ethanol oxidation reactions.(2) A real-space-grid quantum mechanical / molecular mechanical (QM/MM) simulations have been carried out to investigate the role of the water solvent on the novel ethanol oxidation reaction catalyzed by two water molecules through proton transfer mechanism. We have considered two thermodynamical conditions of solutions for the calculations; ambient(AW) and supercritical water(SCW). The QM/MM simulations have revealed that the solvation energy for the transition state(TS) is larger than that of the reactant state in the SCW resulting in the reduction of the activation energy by 3.7 kcal/mol. While, in the AW, the energy barrier is raised by 7.2 kcal/mol. Radial distribution functions show that hydrogen bonding between the solvent and the water molecules that participate in the reaction seriously collapses when the complex is changed from the reactant to the TS in the AW, suggesting that the closely packed hydrogen bond network attached to the reactant disturbs the proton migration to take place. A reaction mechanism by stepwise proton translocations has also been examined and found to be minor as compared with the concerted one.

（1）已经进行了从头密度的功能理论计算，以研究水分子在乙醇的氧化反应中的催化作用：CH_3CH_2OH + NH_2O-> CH_3CHO + H_2 + H_2 + NH_2O（n = 0，1，2）。结果表明，在n = 0的情况下，反应的势能屏障为88.0 kcal/mol，而当反应中涉及两个水分子（n = 2）时，则将其减少〜34 kcal/mol。结果，速率常数增加到3.31x10^<-4> s^<-1>，该速率显示了水分子在乙醇氧化物反应中的显着催化作用。（2）通过在两次转移水解乙醇氧化物的作用中，实现了真实的空间量子机械 /分子机械 /分子机械（qm / mm）的真实空间量子机械 /分子机械（qm / mm），这两种作用是在乙醇中的作用。机制。我们考虑了两个用于计算的热力学条件。环境（AW）和超临界水（SCW）。 QM/MM模拟表明，过渡态（TS）的溶液能大于SCW中反应态的溶液能量，导致活化能减少3.7 kcal/mol。而在AW中，能量屏障则由7.2 kcal/mol提出。径向分布函数表明，当溶液与参与反应的水分子之间的氢键在AW中从反应物转换为TS时严重崩溃，这表明紧密堆积的氢键网络连接到反应物上，proton子迁移到了质子迁移。与协同的反应机制相比，还检查了逐步质子翻译的反应机制，并且发现较小。