Study on desulfurization and catalytic mechanisms of iron oxides during supercritical water gasification for hydrogen production

Sulfur typically converts to H 2 S during the supercritical water gasification (SCWG) process, causing several serious problems. Iron oxides have the potential to achieve simultaneously catalysis and desulfurization, thereby optimizing the original process. Therefore, two types of iron oxides (Fe 2 O 3 , Fe 3 O 4 ) were selected to investigate the desulfurization performance and the effects on the gasification under different conditions. Due to differences in the reactivity of lattice oxygen, the desulfurization performance of Fe 3 O 4 was slightly inferior to that of Fe 2 O 3 . Iron oxides exhibit preferential adsorption and conversion of H 2 S over other gases. H 2 S was converted into solid sulfur like FeS/FeS 2 . Lattice oxygen oxidized part of H 2 S into inorganic ions such as SO 4 2− . Additionally, iron oxides catalyzed the SCWG process. Lattice oxygen also promoted the cleavage of C-C bonds, improving the gasification efficiency. Fe 2 O 3 further oxidized hydrocarbon gases, so it also consumed a small amount of H 2 . Fe 3 O 4 did not consume H 2 , facilitating the production of hydrogen-rich gases, particularly CH 4 .