Novel Regenerable Magnesium Hydroxide Sorbents for CO2 Capture at Warm Gas Temperatures

A novel sorbent consisting of Mg(OH) 2 was developed for carbon dioxide (CO 2 ) capture at 200−315 °C suitable for CO 2 capture applications such as coal gasification systems. Thermodynamic analysis conducted with the FactSage software package indicated that the Mg(OH) 2 sorbent system is highly favorable for CO 2 capture up to 400 °C at 30 atm. MgCO 3 formed during sorption decomposes to release CO 2 at temperatures as low as 375 °C up to 20 atm. MgO rehydroxylation to form Mg(OH) 2 is possible at temperatures up to 300 °C at 20 atm. The experimental data show that the sorbent is regenerable at 375 °C at high pressure and that steam does not affect the sorbent performance. A multicycle test conducted in a high-pressure fixed-bed flow reactor at 200 °C with 28% CO 2 showed stable reactivity during the cyclic tests. The capture capacity also increased with increasing pressure. The sorbent is unique because it exhibits a high CO 2 capture capacity of more than 3 mol/kg at 200 °C and also is regenerable at a low temperature of 375 °C and high pressure. High-pressure regeneration is advantageous because the CO 2 compression costs required for sequestration can be reduced.