Production of phenolic-rich slow pyrolysis liquid extracts by supercritical carbon dioxide fractionation

Abstract To produce biogenic phenolic-rich liquids, which could be of great interest to the adhesive, wood preservation and coating industry, beech wood slow pyrolysis liquid (SPL) was extracted with supercritical CO 2 (scCO 2 ). To this end, a scCO 2 extraction plant was extended with a separation unit with three separators. A stepwise depressurisation of the scCO 2 in the separators enabled various fractions of the extracted SPL, with differing compositions, to be collected. During depressurisation, the density of the scCO 2 (724 kg/m 3 –2 kg/m 3 ) and, thus, the solubilities of the extracted substances in scCO 2 were reduced in three separators. At a density of 261 kg/m 3 in the second separator, extracts with a content of up to 41.1 wt.% GC-detectable monomeric phenolic substances were produced. At lower scCO 2 densities in the subsequent separator, the proportion of better scCO 2 -soluble substances, such as acids, ketones and furans, increased in the extracts.