Influence of precursor of K2CO3 for CO2 capture

” monoclinic and hexagonal K2CO3 exhibit different microstructures. Zhao et al. compared the carbonation reactivity of K2CO3 calcined from different precursors such as analytical pure K2CO3, K2CO3•1.5H2O and KHCO3. Results indicated that K2CO3 calcined from KHCO3 showed high carbonation conversion and reaction rate, which was attributed to the better microstructure parameters (surface area and pore volume) and the important role of the K4H2(CO3)2•1.5H2O intermediate (Zhao et al., 2009c2012a). Zhao et al. further preloaded K2CO3, K2CO3•1.5H2O and KHCO3 on activated carbon (AC) and Al2O3 supports to clarify the interaction between the precursors and supports. The carbonation capacity was improved significantly for K2CO3 and K2CO3 dehydrated from K2CO3•1.5H2O after they were loaded on AC and Al2O3. Thus, incorporating the precursors into porous supports had diminished the precursor effects on the carbonation reactivity (Zhao et al., 2011). Mahinpey et al. compared the carbonation performance of the regenerated and prehydrated K2CO3 samples and similar results were observed, confirming that the KHCO3-derived adsorbent was highly active for carbonation (Gomez et al., 2016Jayakumar et al., 2016). Although different precursors have been investigated and the precursor effects have been correlated to carbonation reactivity, it remains unclear how the precursors endow the adsorbents with different active sites for carbonation. Besides, the K2CO3 crystals reported in literatures are all derived from inorganic precursors. It is not clear whether K2CO3 crystals and their carbonation reactivity would change if organometallic potassium precursors are employed. Theoretically, calcination of organometallic precursors with higher molecular weights will yield adsorbents with higher Brunauer-Emmett-Teller (BET) surface areas and greater pore volumes for enhanced carbonation performance, and this needs further experimental verifications. Therefore, more deep insights into the understanding of precursor effects are necessary.”

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