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 (MnO_x) 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 MnO_x catalyst improves the CO₂ absorption rate and amount as high as 360% and 132%, respectively. The MnO_x 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 MnO_x might primarily result from both plentiful basic sites and unsaturated Mn sites as well as the synergistic interaction between various oxides. Furthermore, the MnO_x 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.