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首页> 外文期刊>The journal of physical chemistry, A. Molecules, spectroscopy, kinetics, environment, & general theory >Quantum Chemical Study of CH3 + O-2 Combustion Reaction System: Catalytic Effects of Additional CO2 Molecule
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Quantum Chemical Study of CH3 + O-2 Combustion Reaction System: Catalytic Effects of Additional CO2 Molecule

机译：CH3 + O-2燃烧反应系统的量子化学研究：附加二氧化碳分子的催化作用

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摘要

The supercritical carbon dioxide diluent is used to control the temperature and to increase the efficiency in oxycombustion fossil fuel energy technology. It may affect the rates of combustion by altering mechanisms of chemical reactions, compared to the ones at low CO2 concentrations. Here, we investigate potential energy surfaces of the four elementary reactions in the CH3 + O-2 reactive system in the presence of one CO2 molecule. In the case of reaction CH3 + O-2 -> CH2O + OH (R1 channel), van der Waals (vdW) complex formation stabilizes the transition state and reduces the activation barrier by similar to 2.2 kcal/mol. Alternatively, covalently bonded CO2 may form a six-membered' ring transition state and teduce the activation barrier by similar to 0.6 kcal/mol. In case of reaction CH3 + O-2 -> CH3O + O (R2 channel), covalent participation of CO2 lowers the barrier for the rate limiting step by 3.9 kcal/mol. This is expected to accelerate the R2 "process, important for the branching step of the radical chain reaction mechanism. For the reaction CH3 + O-2 -> CHO + H2O (R3 channel) with covalent participation of CO2, the activation barrier is lowered by 0.5 kcal/mol. The reaction CH2O + OH -> CHO + H2O (R4 channel) involves hydrogen abstraction from formaldehyde by OH radical. Its barrier is reduced from 7.1 to 0.8 kcal/mol by formation of vdW complex with spectator CO2. These new findings are expected to improve the kinetic reaction mechanism describing combustion processes in supercritical CO2 medium.
机译：超临界二氧化碳稀释剂用于控制温度并提高oxycombustion化石燃料能源技术的效率。与低二氧化碳浓度的浓度相比，它可以通过改变化学反应机制来影响燃烧的速率。在此，我们在一个CO 2分子存在下研究CH3 + O-2反应性系统中的四个基本反应的潜在能量表面。在反应CH3 + O-2 - > CH 2 O + OH（R1通道）的情况下，范德华（VDW）复合物形成稳定过渡状态并通过类似于2.2kcal / mol减小活化屏障。或者，共价键合的CO 2可以形成六元环过渡状态，并通过类似于0.6kcal / mol而引发活化屏障。在反应CH3 + O-2 - > CH 3 O + O（R2通道）的情况下，CO2的共价参与将速率限制步骤的屏障降低了3.9kcal / mol。这预计将加速R2“过程，对于自由基链反应机理的分支步骤重要。对于CH3 + O-2 - > CHO + H 2 O（R3通道），具有共价参与CO2，可激活屏障降低0.5千卡/摩尔。反应CH 2 O + OH - > CHO + H 2 O（R4通道）涉及来自甲醛的氢摘除OH基团。通过与观众CO2的VDW复合物形成VDW复合物，其屏障从7.1至0.8kcal / mol降低。这些预计新发现将改善描述超临界CO2培养基中的燃烧过程的动力学反应机制。

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