Monoethanolamine assisted CO2 hydrogenation to methanol – A computational study

Abstract

Carbon dioxide emission to the atmosphere has to be reduced which can be done by utilizing CO2 in the synthesis of added value products. At the same time this will lead to a process which can help to store renewable energy. The use of hydrogen produced from the electrolysis of water in carbon dioxide reduction to methanol could be an efficient way to store energy and to convert CO2 into an added value product. The synthesis of methanol from CO2 is usually performed catalytically in gas phase. Many scientists nowadays expressed interest in testing the feasibility of the reaction also in aqueous phase. In this direction, monoethanolamine (MEA) can be used as a solvent for capturing and trapping carbon dioxide in an aqueous phase. In this work, the hydrogenation of (2-hydroxyethyl) carbamic acid (HO-(CH2)2-NH-COOH) which is one of the produced species during the capture process has been investigated by using computational tools. The uncatalyzed and catalyzed-like hydrogenation mechanisms leading to methanol (and MEA+water) as a product has been studied by using high level ab initio calculations in aqueous phase. The mechanisms have been described at the molecular level to provide a deeper understanding of the processes. The calculations indicate that the highest barrier height in the catalyzed-like process is only 114.67 kJ/mol, which is 227.71 kJ/mol lower than the corresponding step in the uncatalyzed mechanism. Furthermore, the energy storage efficiency of the catalyzed-like process is 96.68%, which is 7.5 times more efficient than the uncatalyzed mechanism.