Year: 2025
Type: article
Abstract: High Resolution Image Download MS PowerPoint Slide Alkaline earth metal oxides are economically attractive, earth-abundant sorbents for CO 2 capture. In particular, MgO is a promising CO 2 sorbent for applications in the intermediate temperature range (200–400 °C). However, MgO requires the addition of promoters such as alkali metal nitrates or carbonates to overcome the slow kinetics of CO 2 sorption. It has been observed experimentally that the addition of K 2 CO 3 increases the CO 2 uptake of MgO, yet its role remains poorly understood; this is a critical knowledge gap for the design of more efficient sorbents. In this work, using a combination of in situ XRD and Raman spectroscopy, we gain insight into the CO 2 uptake mechanism of K 2 CO 3 -promoted MgO, which proceeds in two steps. An initial rapid CO 2 uptake (within 1 min) occurs via the formation of a potassium-rich amorphous carbonate phase (K 2 CO 3 ·xMgCO 3 ·yH 2 O). This is followed by a slower CO 2 capture step, in which the intermediate K-rich phase transforms into a magnesium-rich amorphous carbonate, along with the formation of small amounts of crystalline (hydrated and anhydrous) carbonates such as K 2 CO 3, baylissite (K 2 Mg(CO 3 ) 2 ·4H 2 O), and nesquehonite (MgCO 3 ·3H 2 O). In situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) analysis reveals that surface hydroxides, which remain on the MgO surface even after a thermal treatment at 720 °C in N 2, facilitate the formation of hydrated carbonates at 315 °C in dry CO 2 . However, the presence of steam during carbonation lowers the CO 2 uptake and inhibits the second CO 2 uptake step, most likely by stabilizing the K-rich amorphous intermediate. Cyclic CO 2 uptake and regeneration experiments reveal the crucial role of a high K 2 CO 3 dispersion within the sorbent for maintaining good cyclic stability.
Source: JACS Au
Institutions: ETH Zurich, UNSW Sydney, The University of Adelaide
Language: English
Subfield: Mechanical Engineering
Field: Engineering
Domain: Physical Sciences
SDG: Climate action
Open Access status: gold
Estimated APC paid: $3,500
OpenAlex ID: W4417138519