Lignin is the second most abundant natural polymer after cellulose, and although its recovery from biorefineries is increasing, current commercial extraction primarily is through Kraft pulping, from which only 2% of the separated lignin (~160 kt/y) is recovered. Many innovative products can be generated from diverse lignins, but hurdles for valorization include the structural heterogeneity, dark color, and unpleasant odor. These characteristics depend on biomass type, fractionation process, and recovery/purification method, and depolymerization to aromatic compounds is a promising strategy to address these challenges and generate valuable bioproducts. In this work, two reductive catalytic fractionation (RCF) processes were examined for the depolymerization of technical lignin samples from numerous sources (e.g., Kraft, soda, organosolv, and thermomechanical pulping). A conventional RCF process was used to develop a correlation between lignin thermal stability and phenolic product yield, resulting in a facile screening method for the ‘depolymerizability’ of technical lignins. Subsequently, a novel, intensified RCF process was developed to simultaneously depolymerize lignin to its constituent phenolic building blocks and purify those compounds. In addition to improved separations, the intensified process operates at much lower pressures than conventional RCF, resulting in safer and less costly operation. Finally, the phenolic products from the intensified RCF process were functionalized with acrylate groups and incorporated into stereolithography (SLA) 3D printing resins. The thermal properties (e.g., thermal stability and glass transition temperature) of the 3D printed materials were characterized by TGA and DSC, and their mechanical properties (e.g., modulus, tensile strength) were analyzed by dynamic mechanical analysis and tensile testing.

Intensified valorization of lignocellulosic biomass to biobased polymers

ACS Spring Meeting 2021

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