Thermochemical and catalytic conversion of lignin

Authors: Mullen, Charles

Submitted to: Book Chapter
Publication Type: Book / Chapter
Publication Acceptance Date: 5/13/2022
Publication Date: 8/21/2022
Citation: Mullen, C.A. 2022. Thermochemical and catalytic conversion of lignin. In: Nghiem, N.P., Kim, T.H., Yoo, C.G., editors. Biomass Utilization: Conversion Strategies. New York, NY: Springer. p. 133-200. https://doi.org/10.1007/978-3-031-05835-6_7.
DOI: https://doi.org/10.1007/978-3-031-05835-6_7

Interpretive Summary: Biorefineries convert biomass such as grass, wood, crop residues and wastes to fuels and chemicals. These renewable resources can be used to displace those produced from fossil sources. Biorefineries tend to be very good at converting some parts of biomass such as cellulose to products but struggle with generating valuable products from lignin, a part of the plant that gives it strength. Developing methods to convert lignin and therefore utilize more of the plant that is input into the biorefinery is key to their commercial viability. This chapter details progress on using heat and chemical catalysis to produce fuels and chemicals from lignin. The information contained in this chapter will be useful to those developing biorefinery processes.

Technical Abstract: Development of efficient processes for the production of high value chemicals from lignin remains one of the largest technical hurdles in the development of competitive, sustainable biorefineries. This chapter details progress in thermo-catalytic lignin conversion with a focus on processes that produce liquid products largely comprising high value aromatic monomers. The methods examined include both pyrolysis and solvent liquefaction. The pyrolysis section will cover both non-catalytic fast pyrolysis and catalytic pyrolysis, while the solvent phase section will cover the liquefaction process catalyzed by acids, bases, and active metals. Both reductive and oxidative processes will be covered. Also covered will be progress in the more recently developed lignin-first biorefinery concept, where in situ lignin depolymerization occurs concurrently with its fractionation from the biomass leaving a carbohydrate rich by-product. Finally, a summary of the remaining technical challenges in lignin depolymerization will be presented.