Effect of pH-controlled synthesis on the physical properties and intermediate-temperature CO2 sorption behaviors of K–Mg double salt-based sorbents

•K–Mg double salt-based sorbents were synthesized using a pH-controlled method.•The component fraction could be varied using different pH-controlling solutions.•The sorbent showed high CO2 sorption uptake with fast sorption kinetics.•The CO2 sorption mechanism of sorbent was studied from in situ XRD analysis.

High-temperature CO2 sorption has been investigated as a new CO2 capture technology, and the development of high-temperature CO2 sorbents is critically important for the realization of this technology. In this study, K–Mg double salt-based sorbents were synthesized using a new pH-controlled precipitation method and the prepared sorbents were tested for medium high (intermediate) temperature CO2 sorption. In the new method for the synthesis of K–Mg double salt-based sorbents, the pH of the reagent solution was controlled by adding K2CO3 and/or KOH, resulting in varied ratios of different components in the sorbent. The CO2 sorption ability was enhanced in K–Mg double salt-based sorbents synthesized using the new pH-controlled method compared to the samples synthesized by the conventional precipitation method. The newly prepared K–Mg double salt-based sorbents had a high CO2 sorption uptake of up to 2.09 mol kg−1 at 300 °C and 1 bar. In addition, they showed fast sorption kinetics and good cyclic stability during multiple sorption/desorption procedures.

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