Characteristics of CO2 fixation by chemical conversion to carbonate salts

Abstract

We propose a new method of CO2 removal by combining carbon dioxide capture and storage (CCS) and CO2 fixation processes. In this study, amine solutions were used to make carbonates and calcium ions were used for CO2 fixation. Primary (MEA), secondary (DEA), and tertiary (MDEA) amines were selected for use in a 10 or 30wt% amine solution with H2O and Ca2+ in a CO2 saturated solution. CO2 fixation was verified and the carbonate was formed under normal temperature and pressure conditions. As a result, most of the CO2 was converted to a precipitate (more than 84% by weight). The molar yield of MDEA was higher than that of the other amines (MEA and DEA). We believe that this is due to the fact that tertiary amines (MDEA) do not have H+ in their structure. Therefore, MDEA does not produce carbamate when CO2 is absorbed in solution. Further, we measured the residual CO2 in each solution through a desorption process. These results also demonstrate less residual CO2 in the MDEA than in the other amines. Product carbonates were analyzed by X-ray diffractometry (XRD) and were found to consist of calcite, aragonite, and vaterite with various compositions depending on the particular amine solution used for the CO2 conversion. Therefore, we conclude that CO2 fixation is possible using amine solutions and metal ions. We believe that this process can be applied to CO2 emission capture techniques where no external energy is required.