LAUSR

Abstract Structural properties and functional groups variations of hydro-products from hydrothermal carbonization (HTC) of loblolly pine at 180, 200, 220, 240 and 260 °C were investigated in this paper. More than 50% fixed carbon content can be obtained in solid products, indicating HTC is a valued carbon sequestration method. The Higher Heating Value (HHV) of the solid residue from 260 °C reached 30.74 MJ/kg, nearly 1.53 times that of untreated pine. Higher temperature benefit for the generation of condensed aromatic structure especially at 240 °C, while 260 °C more conductive to etherification and aryl-condensation substitution reaction. Solid products from HTC were condensed carbon materials consist of lignin/pseudo-lignin and furfural structures with low carbonyl and carboxyl content, protonated carbon percentage in aromatic structure is higher than un-protonated carbon in aromatic structures, methoxy content reduced at higher temperature while aliphatic side-chains content increased; Liquid chemicals were water-soluble products consist of condensed polyaromatic structure with an elevated content of carbonyl and carboxyl groups, un-protonated carbon in aromatic structures show higher percentage, methoxy content increased at higher temperature while aliphatic side-chains content decreased, free phenol hydroxyl are richer than C 5 substituted condensed phenolic OH.