Hydrothermal preparation of calcium–aluminum carbonate sorbent for high-temperature CO2 capture in fixed-bed reactor

Calcium–aluminum carbonate (Ca–Al–CO3) sorbents for CO2 sorption were hydrothermally prepared and tested at 750 °C by thermal gravimetric (TG) analysis and fixed-bed reactor method. The Ca/Al molar ratios of the sorbents ranged from 1:1 to 30:1. As the Ca/Al molar ratio increased, the CO2 sorption mass increased from 13.4 to 74.2 wt%. The capturing stability remained stable at 99% in TG analyzer and 76% in the reactor (10 cycles at 750 °C). The kinetic parameter, estimated by the kinetic control model, indicated that the model was consistent with the carbonation reaction of Ca–Al–CO3 with CO2 in the kinetically controlled reaction regime. The estimated activation energy (Ea) of CO2 sorption was 53.6 kJ/mol, slightly less than the typical Ea of CaO carbonation reactions above 600 °C in fixed-bed reactors. This reduction may be partially attributed to the co-existence of Ca(OH)2 and CaO nanoparticles in the synthetic Ca–Al–CO3 sorbents.