Carbonation and Hydration Characteristics of Dry Potassium-Based Sorbents for CO2 Capture

Thermogravimetric apparatus (TGA) and X-ray diffraction (XRD) have been used to study the characteristics of potassium-based sorbents for CO 2 capture. The carbonation reactivity of K 2 CO 3 ·1.5H 2 O and K 2 CO 3 dehydrated from K 2 CO 3 ·1.5H 2 O was weak. However, K 2 CO 3 calcined from KHCO 3 showed excellent carbonation capacity and no deactivation of sorbents during multiple cycles. The XRD results showed that the sample dehydrated from K 2 CO 3 ·1.5H 2 O was K 2 CO 3 with structure of monoclinic crystal (PC#1). The carbonation products of PC#1 included K 2 CO 3 ·1.5H 2 O and KHCO 3, and K 2 CO 3 ·1.5H 2 O was the main product. Correspondingly, K 2 CO 3 with structure of hexagonal crystal (PC#2) was the product calcined from KHCO 3, and the main carbonation product of PC#2 was KHCO 3 . The byproduct of K 4 H 2 (CO 3 ) 3 ·1.5H 2 O for PC#2 would affect the carbonation processes. Hydration tests confirmed the two hypotheses: the hydration reaction will first occur for K 2 CO 3 with structure of monoclinic crystal, and the carbonation reaction will first occur for K 2 CO 3 with structure of hexagonal crystal. The reaction principles were analyzed by product and the relevant reactions. This investigation can be used as basic data for dry potassium-based sorbents capturing CO 2 from flue gas.