Biobased Resins Using Lignin and Glyoxal

Abstract

The utilization of lignin and glyoxal as potentially sustainable and less hazardous building blocks for phenolic resins is an emerging research field. Lignin thereby serves as a partial, macromolecular substitute for phenol, while glyoxal fulfills the role of an aldehyde cross-linker. In the first part of this perspective, the industrial context of lignin and glyoxal will be expounded with a focus on their origin and production processes. In the framework of phenolic resins, the use of lignin and glyoxal can be categorized into two research domains: (i) glyoxalation to improve the reactivity of lignin prior to resin synthesis and (ii) direct resin synthesis using lignin and glyoxal with glyoxal immediately serving as the cross-linker. This perspective provides a comprehensive overview of the progress made in both domains, pinpointing the opportunities, blind spots, and challenges that lay ahead.

Synthesis of Lignosulfonate-Based Dispersants for Application in Concrete Formulations

“…In another approach, the glyoxalation of LS in an alkaline medium was carried out [ 61 ], during which hydroxyl groups in ethylol moieties are expected to be introduced in the LS structure. In addition, the eventual depolymerization/repolymerization of lignin via crosslinking yielding adducts with increased M w was expected [ 61 , 62 , 63 ].…”

“…In another approach, the glyoxalation of LS in an alkaline medium was carried out [ 61 ], during which hydroxyl groups in ethylol moieties are expected to be introduced in the LS structure. In addition, the eventual depolymerization/repolymerization of lignin via crosslinking yielding adducts with increased M w was expected [ 61 , 62 , 63 ]. Unfortunately, the high pH (>12) necessary to carry out the glyoxalation reaction probably led to changes in the LS structure with the apparent loss of water solubility.…”

Fast screening of Depolymerized Lignin Samples Through 2D‐Liquid Chromatography Mapping

“…[ 7 , 10 , 11 ] As a result, lignin depolymerization into functionalized bio‐aromatics, i. e., monomers, dimers and oligomers, will become the main bio‐based route towards sustainable aromatic chemicals and building blocks for polymer synthesis or other high value applications. [ 5 , 11 , 12 , 13 , 14 , 15 , 16 , 17 , 18 ] Unfortunately, most polysaccharide focused industries discard lignin as a waste product. As a result, an estimated 100 million tonnes of lignin (technical lignins), mainly coming from the paper and pulping industry, is annually burned as low value fuel.…”

“…The latter consists of functionalized aromatic building blocks, which are linked through mostly ether (C−O) and, to a lesser extent, carbon‐carbon (C−C) bonds, making it the largest renewable source of aromatics [7,10,11] . As a result, lignin depolymerization into functionalized bio‐aromatics, i. e., monomers, dimers and oligomers, will become the main bio‐based route towards sustainable aromatic chemicals and building blocks for polymer synthesis or other high value applications [5,11–18] . Unfortunately, most polysaccharide focused industries discard lignin as a waste product.…”

Strategies for the Removal of Polysaccharides from Biorefinery Lignins: Process Optimization and Techno Economic Evaluation

“…Despite the challenges, which are (i) the structural complexity and heterogeneity of lignin, (ii) the variability of biomass sources and treatment processes, and (iii) the presence of impurities [11], the number of publications about lignin isolation, purification, fractionation, chemical modification, and potential applications has grown exponentially in the recent years [4,12,13]. These applications include binders [14], surfactants [15], dispersants for cement [16], carbon fibers [17,18], epoxy, polyurethane and phenol formaldehyde resins [19][20][21][22], thermoplastic elastomers [23], and fire retardants [13] among others. Given the applicability in diverse segments, lignin valorization could play an essential role in the bio-based economy and will contribute to the mitigation of climate change [24].…”