Hydroxybenzoic acid derived porous carbons for low pressure CO2 capture

Abstract

There is an urgent need to mitigate CO2 emissions released into the atmosphere from coal-fired power plants. 4-Hydroxybenzoic acid (HBA) is a cost-effective small organic molecule (SOM) that has been used in this study as a molecular precursor for CO2-philic and affordable solid sorbent production. Many pore development strategies and comprehensive characterization techniques were employed. It is found that pyrolysis of HBA (H-800) without any additives allows reaching a capacity of 1.09 mmol g-1 at 0.15 bar, 298 K or 0.86 mmol g-1 at 0.15 bar, 313 K, which shows that simple carbonization of appropriate SOM may yield competitive results over well-known carbonization methods. Several carbonization techniques were employed on the SOM, including CO2, ZnCl2, KOH activations, or potassium salt thermolysis, and zinc salt thermolysis. Starting from zinc salt ends up with very low carbon yield (3 wt%) and high meso-macro pore volume, which is in the range of 2.78 cm3 g-1. KOH activation or potassium salt thermolysis results are comparable to the CO2 capture performance of H-800, though higher micropore volumes up to 0.55 cm3 g-1 were achieved. Additionally, CO2 activation resulted in similar CO2 capture capability and micropore volume as in the case of H-800. Finally, it was found that ultra-micropores are the effective pore range for low pressure CO2 adsorption (0.15 bar) at 298 K or 313 K.