Diol Modification to Facilitate Full Biomass Utilization: From Mechanistic Studies to Process Development

Lignocellulosic biomass valorization presents a critical pathway toward sustainable chemical and material production. This dissertation explores the isolation and functionalization of both carbohydrates and lignin, with an emphasis on selective transformations targeting diol functionalities. The overarching objective is to develop a mechanistic understanding of diol acetalization in order to engineer high-efficiency synthesis routes for renewable solvents, surfactants, and polymer precursors. We expanded diol modification to esterification with boric acid and developed a pulping-compatible lignin-first biomass fractionation strategy. A major focus is the acetalization of D-xylose, a hemicellulose-derived sugar, with aldehydes. A generalized reaction network elucidates the pivotal roles of aldehyde electrophilicity, ring strain, and sugar tautomerism in governing product selectivity. Strongly electrophilic aldehydes produced both furanose- and pyranose-monoacetal, while weaker aldehydes only yield furanose acetals due to unfavourable ring strain in pyranose derivatives. Importantly, furanose diacetals consistently dominate the product distribution over time due to their thermodynamic stability. Building upon this, we modulated the mono-acetalized selectivity, which was often thermodynamically unfavoured, using zeolites as size-selective acetalization catalysts. Highly selective monoacetal formation was achieved in a single step across various sugars and polyols by matching substrate and product sizes with zeolite pore structures. As a result, the xylose-based amphiphiles were produced at high yields (70-95%). Working as bio-based surfactants, they exhibit competitive or superior surface activity and hard-water resistance compared to fossil-based analogues, with an environmentally benign end-of-life. To exploit the high thermodynamic stability of xylose diacetals, we developed four scalable routes to produce diformylxylose (DFX), a versatile solvent and platform chemical, using either pure xylose, raw corncobs, or industrial waste, at high yields. DFX subsequently underwent transacetalization reactions at >80% yield to form diglyoxylic acid xylose (DGAX), a terephthalic acid replacement in polymers production, further extending its utility as a chemical intermediate. These processes were scaled to kg levels and demonstrated good techno-economic and life-cycle competitiveness. To address the limitation of organic solvent use in current biomass valorization technologies, we developed a novel aqueous alkaline "lignin-first" fractionation strategy, compatible with industrial pulping. Using boric acid to stabilize beta-O-4 diol moieties, this method enables the co-extraction of high-quality lignin, papermaking-grade pulp, and xylan at high yields. Over 99.5% of the boric acid is recyclable, ensuring environmental and economic feasibility. This process aligns with existing pulping operations in terms of both process conditions and product specifications,