Abstract
BackgroundLignin is often overlooked in the valorization of lignocellulosic biomass, but lignin-based materials and chemicals represent potential value-added products for biorefineries that could significantly improve the economics of a biorefinery. Fluctuating crude oil prices and changing fuel specifications are some of the driving factors to develop new technologies that could be used to convert polymeric lignin into low molecular weight lignin and or monomeric aromatic feedstocks to assist in the displacement of the current products associated with the conversion of a whole barrel of oil. We present an approach to produce these chemicals based on the selective breakdown of lignin during ionic liquid pretreatment.ResultsThe lignin breakdown products generated are found to be dependent on the starting biomass, and significant levels were generated on dissolution at 160°C for 6 hrs. Guaiacol was produced on dissolution of biomass and technical lignins. Vanillin was produced on dissolution of kraft lignin and eucalytpus. Syringol and allyl guaiacol were the major products observed on dissolution of switchgrass and pine, respectively, whereas syringol and allyl syringol were obtained by dissolution of eucalyptus. Furthermore, it was observed that different lignin-derived products could be generated by tuning the process conditions.ConclusionsWe have developed an ionic liquid based process that depolymerizes lignin and converts the low molecular weight lignin fractions into a variety of renewable chemicals from biomass. The generated chemicals (phenols, guaiacols, syringols, eugenol, catechols), their oxidized products (vanillin, vanillic acid, syringaldehyde) and their easily derivatized hydrocarbons (benzene, toluene, xylene, styrene, biphenyls and cyclohexane) already have relatively high market value as commodity and specialty chemicals, green building materials, nylons, and resins.
Highlights
Lignin is often overlooked in the valorization of lignocellulosic biomass, but lignin-based materials and chemicals represent potential value-added products for biorefineries that could significantly improve the economics of a biorefinery
The high energy content of lignin, the presence of highly reactive groups, and the fact that it will be generated in large quantities as second generation biorefineries are deployed represents a significant opportunity for the production of a wide range of renewable chemicals and materials that can be sold as co-products (Figure 1)
Yields were not the same using different solvents, patterns of lignin degradation and recovery were similar for all the solvents tested
Summary
Lignin is often overlooked in the valorization of lignocellulosic biomass, but lignin-based materials and chemicals represent potential value-added products for biorefineries that could significantly improve the economics of a biorefinery. Lignocellulosic biomass is primarily composed of three biopolymers: cellulose, hemicelluloses and lignin [1]. Lignin constitutes roughly a third of the biomass and is typically burned to produce waste heat and/or electricity within paper mills and biorefineries [1,5]. The high energy content of lignin, the presence of highly reactive groups, and the fact that it will be generated in large quantities as second generation biorefineries are deployed represents a significant opportunity for the production of a wide range of renewable chemicals and materials that can be sold as co-products (Figure 1)
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