Lignin valorization to chemicals and materials is recognized to be essential for the economic viability of future biorefineries. In this context, several promising catalytic approaches have been reported for lignin deconstruction to aromatic monomers and other low molecular weight compounds. However, major challenges remain such as the handling of solid lignin, limited knowledge on catalyst deactivation/stability, avoidance of stoichiometric reagents and the demonstration of continuous processing. This talk will present advances in addressing these challenges. Specifically, strategies to sequentially attack the C=C bonds (by ozonolysis) followed by C-O bonds (with solid Lewis acid catalysts) to isolate various value-added fractions in grass and woody lignins will be discussed. A simple spray reactor is used for the ozonolysis pretreatment to cleave C=C bonds in grass lignins to conveniently recover vanillin and p-hydroxybenzaldehyde, two of the most valuable monomers. Continuous depolymerization of the remaining lignin is achieved in a slurry reactor over a Lewis acidic catalyst (Zr-KIT-5) with stable activity and without the need for any reducing or oxidizing agents. The observed yield of aromatic monomers is greater than those recently reported using either reductive catalyst fractionation of lignin over Pd/C catalyst using hydrogen or oxidation/hydrolysis routes. The foregoing sequential valorization strategy accommodates a wide variety of lignins and raises the possibility of deploying modular concepts in distributed biorefineries.
Bala Subramaniam is the Dan F. Servey Distinguished Professor of Chemical Engineering at the University of Kansas (KU). Subramaniam earned a B.Tech. degree in Chemical Engineering from the University of Madras, India and his Ph. D. in Chemical Engineering from the University of Notre Dame. He has also held visiting professorships at the University of Nottingham, United Kingdom and the Institute of Process Engineering, ETH, Zürich, Switzerland. Subramaniam’s research interests are in catalysis, reaction engineering and crystallization. He has nearly 190+ journal publications, 30 issued patents and edited 2 books. Subramaniam is co-founder and founding Director of the Center for Environmentally Beneficial Catalysis (CEBC), a unique University/Industry consortium that is developing and providing licensing opportunities for novel resource-efficient technologies related to fuels and chemicals. He also co-founded CritiTech, a pharmaceutical company based in Lawrence, KS. Subramaniam is executive editor of ACS Sustainable Chemistry and Engineering journal and chaired the 2018 Gordon Research Conference on Green Chemistry. His honors include ASEE’s Dow Outstanding Young Faculty Award, Indian Institute of Chemical Engineers’ Chemcon Lectureship Award, and KU’s Higuchi Research Achievement Award. Subramaniam is a Fellow of the AIChE, the ACS Industrial & Engineering Chemistry Division, and the National Academy of Inventors.