One-step synthesis of efficient manganese-based oxide catalyst for ultra-rapid CO2 absorption in MDEA solutions

Abstract

The objective of this study is to develop a promising and feasible technique to significantly increase in the CO2 absorption rate of tertiary amine solutions. Here, for the first time, a manganese-based oxide (MnOx) with four different oxides, including Mn3O4, Mn2O3, MnOOH, and MnO2, is prepared using a one-step synthesis approach, and utilized to catalytically accelerate CO2 absorption in a typical tertiary amine, MDEA solution. The results reveal that the MnOx catalyst improves the CO2 absorption rate and amount as high as 360% and 132%, respectively. The MnOx also outperforms various single manganese-based oxides and their physical mixture, as well as most of the reported catalysts in terms of catalytic enhancement of CO2 absorption in the MDEA solution. The FT-IR analysis is used to confirm the catalytic promotion effect of CO2 absorption, and a catalytic mechanism is proposed. The remarkable catalytic enhancement effect of MnOx might primarily result from both plentiful basic sites and unsaturated Mn sites as well as the synergistic interaction between various oxides. Furthermore, the MnOx also has a favorable effect on CO2 desorption and exhibits outstanding recyclability. This work not only demonstrates a workable strategy for improving the CO2 absorption rate by incorporating a low-cost and high-efficiency solid base catalyst into tertiary amine solutions but also provides guidance for developing more effective catalysts to promote CO2 absorption.