CO_(2)+MEA反应在CaCO_(3)催化下Eley-Rideal模型及混合胺溶液体系协同效应的机理研究

Mechanism on Eley-Rideal model of CO_(2)+MEA reaction under solid catalyst CaCO_(3) and coordination effect of mix amine solution system

研究混合胺溶液吸收二氧化碳(CO_(2))的反应机理对低碳环保具有重要意义.本文以碳酸钙(CaCO_(3))为催化剂,在Eley-Rideal模型下通过Gaussian09软件模拟计算乙醇胺(MEA)+CO_(2)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CO_(2)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CaCO_(3)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-CO_(2),MEA-AMP-CO_(2))低于MEA-CO_(2)-MEA能量,差距分别为-18.25%和-14.5%,而MEA-MDEA-CO_(2)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.

Study of reaction mechanism of mixed amine solutions absorbing carbon dioxide(CO_(2)) 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) + CO_(2) was simulated by Gaussian09 according to the Eley-Rideal model. In order to analyze the coordination effects of CO_(2) 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 CaCO_(3), but the free energy did not change. For coordination effect, the energy of the carbamate ammonium salt [MEA-DEA-CO_(2), MEA-AMP-CO_(2)] is lower than the energy of [MEA-CO_(2)-MEA], and the difference was-18.25% and-14.5%. But the energy difference between the MEA-MDEA-CO_(2) system and MEA-CO_(2) 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.