CO2+MEA反应在CaCO3催化下Eley-Rideal模型及混合胺溶液体系协同效应的机理研究

研究混合胺溶液吸收二氧化碳(CO₂)的反应机理对低碳环保具有重要意义.本文以碳酸钙(CaCO₃)为催化剂,在Eley-Rideal模型下通过Gaussian09软件模拟计算乙醇胺(MEA)+CO₂反应机理,,同时计算混合胺溶液体系乙醇胺(MEA)+二乙醇胺(DEA)/2-氨基-2-甲基-1-丙醇(AMP)/N-甲基二乙醇胺(MDEA)吸收CO₂中经实验证明的协同效应.本文在CCSD(T)/6-311++G(d,p)水平上计算在两性离子机理下中间步骤的自由能和几何振动频率.模拟结果表明,在固体催化剂CaCO₃作用下,反应活化能降低了14.9%,但是自由能没有降低.混合胺盐能量(MEA-DEA-CO₂,MEA-AMP-CO₂)低于MEA-CO₂-MEA能量,差距分别为-18.25%和-14.5%,而MEA-MDEA-CO₂体系能量与单一溶液体系差距仅为-5.88%.这表明二级胺,空间位阻胺的协同效应大于三级胺.

Mechanism on Eley-Rideal model of CO2+MEA reaction under solid catalyst CaCO3 and coordination effect of mix amine solution system

Study of reaction mechanism of mixed amine solutions absorbing carbon dioxide(CO₂) have a great significance effect in area of environmental protection.Under the action of solid catalyst calcium carbonate,the reaction mechanism of heterogeneous catalytic ethanolamine(MEA) + CO₂ was simulated by Gaussian09 according to the Eley-Rideal model. In order to analyze the coordination effects of CO₂ absorption in a mixed amine solution which has been demonstrated by experiment repeatdely, we also calculate MEA with other amine: diethanolamine(DEA)/2-amino-2-methyl-1-propanol(AMP)/N-methyldiethanolamine(MDEA). The simulation results indicate that the activation energy of the reaction is reduced by 14.9% with aid of CaCO₃, but the free energy did not change. For coordination effect, the energy of the carbamate ammonium salt MEA-DEA-CO₂, MEA-AMP-CO₂] is lower than the energy of MEA-CO₂-MEA], and the difference was-18.25% and-14.5%. But the energy difference between the MEA-MDEA-CO₂ system and MEA-CO₂ is only-5.88%. This indicates that the coordination effect of secondary amine,sterically hindered amine is stronger than tertiary amine, with order of DEA>AMP>MDEA.