(400d) Depolymerization of Waste Lignin to Valuable Low Molecular Weight Aromatic Compounds Via a Continuous Electrochemical Reactor

Lignin, as the second most abundant biomass reserve in the world, has potential as an alternative to crude oil for production of industrial chemicals [1]. Annually 190 million tons of lignin are generated as a waste product in U.S. biorefineries and pulping mills, with the potential to increase to 1 billion tons by 2050 [2-3]. However, due to the lack of efficient and economical methods for breaking the complex lignin molecule, only 2% of this amount is converted into bioproducts, while the rest is burned as a low grade fuel [4]. Among different methods applied for lignin conversion, electrochemical depolymerization of lignin is promising. It has the privileges of low energy consumption, high yield and selectivity toward desirable products, high reaction rate, and elimination of the char production [5].

This presentation will focus on our efforts for designing a lab-scale continuous electrochemical reactor for lignin depolymerization over a high surface area Ni-Co/TiO₂ electro-catalyst. We will use various analysis techniques for characterization of lignin conversion products to confirm that the continuous process causes high yield and selectivity toward low molecular weight aromatic compounds.

References

[1] H. Lange, S. Decina, and C. Crestini, “Oxidative upgrade of lignin – Recent routes reviewed,” European Polymer Journal, vol. 49, no. 6, pp. 1151–1173, Jun. 2013.

[2] Z. Sun, B. Fridrich, A. de Santi, S. Elangovan, and K. Barta, “Bright Side of Lignin Depolymerization: Toward New Platform Chemicals,” Chem. Rev., vol. 118, no. 2, pp. 614–678, Jan. 2018.

[3] M. D. Kärkäs, B. S. Matsuura, T. M. Monos, G. Magallanes, and C. R. J. Stephenson, “Transition-metal catalyzed valorization of lignin: the key to a sustainable carbon-neutral future,” Org. Biomol. Chem., vol. 14, no. 6, pp. 1853–1914, Feb. 2016.

[4] R. Behling, S. Valange, and G. Chatel, “Heterogeneous catalytic oxidation for lignin valorization into valuable chemicals: what results? What limitations? What trends?,” Green Chem., vol. 18, no. 7, pp. 1839–1854, Mar. 2016.

[5] O. Movil-Cabrera, A. Rodriguez-Silva, C. Arroyo-Torres, and J. A. Staser, “Electrochemical conversion of lignin to useful chemicals,” Biomass and Bioenergy, vol. 88, pp. 89–96, May 2016.