Hot-water pre-extraction from loblolly pine (Pinus taeda) in an integrated forest products biorefinery

Loblolly pine chips were treated with pressurized hot water at elevated temperatures of 160°, 170°, 180°, and 190°C for various times. Components of the resulting extracts were quantified using high-pressure anion exchange chromatography (HPAEC) and UV spectroscopy. The time-temperature effect on the extracted wood yields is described by the H-factor approach. A maximum of about 12% of the wood mass was extracted as sugars at an H-factor of about 1,500 hours. At an H-factor of about 500 hours, 8% of hemicelluloses were removed as polymeric sugars, with a minor removal of lignin (0.5% on ODW) and cellulose (0.3% on ODW). The sum of all monomeric and polymeric sugars reached a maximum of about 12% at an H-factor around 1,500 hours. The extraction yield was highly dependent on the residual pH of the extracts, which dropped rapidly from neutral to an acidic level of pH4 in the early stages of extraction, up to an H-factor of about 100 hours. The maximum yield was obtained at a pH of about 3.5, below which the extraction yield rapidly decreased.