Potassium Catalytic Effect on Gasification Reactions of Coal and Coal/Biomass Blends under Oxy-combustion Conditions. An Isotopic Study Using 13C18O2

In the present study, 20 wt % K2CO3 was added to coal and coal/biomass blends in a 20:80 wt % ratio and subsequently were heating-treated at 600 °C using CO2 or N2 atmospheres. The reactivity under oxy-combustion conditions (21% O2 + 79% CO2) was studied by thermogravimetry, and characterization of chars was carried out by N2 adsorption, scanning electron microscopy, and Raman and X-ray photoelectron spectroscopy. Higher activation energy for impregnated coal/biomass blends compared to impregnated coal was observed, likewise, for materials thermally treated with CO2. It is demonstrated that CO2 gasification takes place together with O2 combustion under oxy-combustion conditions. Isotopically labeled 13C18O2 was used to confirm the participation of CO2 gasification reactions at 450, 500, 550, and 600 °C in both catalyzed and uncatalyzed systems under O2 + CO2. The catalytic effect of potassium promotes CO2 gasification, and the highest CO (12C18O) desorption was obtained with impregnated samples. It is pos...