Kinetic and mechanistic investigation of catalytic alkaline thermal treatment of xylan producing high purity H₂ with in-situ carbon capture

A novel biomass conversion pathway that integrates carbon capture and storage schemes has been investigated using hemicellulose as the biomass feedstock. The alkaline thermal treatment (ATT) produces high purity H₂ from biomass mixed with hydroxide and it can be considered as a bio-energy with carbon capture and storage (BECCS) technology, since the carbon in biomass becomes solid carbonates during the ATT reaction. In this study, in the presence of Ni catalyst, Group 1 and 2 hydroxides are employed to produce as high as 60 mmol H₂ (96.8% purity) from 1 gram of hemicellulose (xylan) feedstock with in-situ carbon capture at mild conditions (i.e., atmospheric pressure and relatively low temperatures ≤773 K). Reaction pathways of hydrogen production in the ATT of hemicellulose are proposed via the investigation of the roles of each hydroxide and catalyst in the H₂ formation from hemicellulose. Along with the previous studies on glucose and cellulose, this research lays a foundation for future development of H₂ production from real biomass with carbon-neutral or possibly negative potential.