FRACTIONATION AND DEPOLYMERISATION OF LIGNOCELLULOSIC MATERIAL

Lignocellulose constitutes an alluring renewable feedstock for the production of bio-based chemicals. This contribution demonstrates for the first time a chemocatalytic biorefinery concept that produces three separate product fractions of valuable product families at high yield and purity from lignocellulosic biomass; the product families, merely comprising of stable products, are (i) a lignin oil enriched with high contents of lignin-derived (mono)phenolics, (ii) essentially humin (furanic oligomers)-free hemicellulose-derived polyols, and (iii) a cellulose pulp. This is achieved by processing biomass in a close to equivolumetric mixture of an alcohol (such as n-butanol) and water at elevated temperature, in the presence of a metal catalyst and hydrogen. During this one-pot fractionation process, the hot liquor disentangles the polymeric biomass and depolymerises lignin and hemicellulose, while the catalyst and reductive environment are essential to accumulate and target stable products at high yield (such as phenolics and polyols, respectively). The process is particularly industrially relevant because its overcomes difficult and complex separation protocols, at place in classic biorefinery technology; the process foresees simple product recuperation in one process step into the three fractions; the solid carbohydrate pulp (mainly cellulose) is retrieved upon filtration, while phase separation of n-butanol and water occurs below 125° C., offering a facile and effective strategy to isolate lignin-derived phenolics, present in the alcohol (such as n-butanol phase) from polyols, present in the aqueous phase at the same time. The three resulting product streams provide a versatile platform for down-stream conversion towards added-value bio-based chemicals.