Catalytic Valorisation of Hemicelluloses in Lignocellulosic Biomass to High-value Platform Chemicals: Reaction Networks, Catalyst Design and Process Integration

Abstract

Hemicelluloses are structurally heterogeneous C5- and C6-rich polysaccharides whose selective conversion can substantially improve carbon utilisation in lignocellulosic biorefineries. Their valorisation is nevertheless more difficult than the conversion of purified monosaccharides because hydrolysis, dehydration, hydrogenation, oxidation, ring rearrangement and condensation compete within reaction media that also contain lignin fragments, mineral ions, extractives and degradation products. This critical narrative review evaluates catalytic strategies that convert hemicellulose, xylan, xylose and hemicellulosic hydrolysates into high-value platform chemicals, with emphasis on furfural, xylitol, oxygenated C5 intermediates, furfuryl alcohol, methylfurans, cyclopentanone, pentanediols, furoic acid and related products. Literature was selected through live searches of accessible scholarly indexes and bibliographic registries, supported by citation chaining and verification of bibliographic identities and Digital Object Identifiers. The evidence indicates that furfural remains the most mature catalytic hub because acid-catalysed depolymerisation and dehydration can be coupled with in situ extraction, although apparent yield gains often depend on solvent-intensive biphasic systems and model substrates. Reductive routes to xylitol are chemically efficient, but catalyst poisoning, hydrolysate purification and hydrogen supply strongly influence practical performance. Furfural upgrading offers a broad product spectrum, yet selectivity is highly sensitive to metal identity, support acidity, hydrogen donor, solvent and water activity. Across pathways, the principal translational weakness is the limited comparability between catalyst studies and integrated biomass processes: many reports optimise reaction yield without fully quantifying catalyst lifetime, carbon balance, separation burden or solvent recovery. The strongest future strategy is therefore not a single superior catalyst, but coordinated feedstock fractionation, catalyst-function matching, impurity tolerance, continuous operation and process-level evaluation. Such integration is necessary for hemicellulose valorisation to progress from high laboratory selectivity to durable and economically credible biorefinery performance.