Production of bio-phenols and bio-based phenolic resins from lignin and lignocellulosic biomass

Lignin is the second most abundant polymer in nature and a major by-product of the paper industry. Crude lignin is also generated as a waste stream in the organosolv deligninfication process and the steam explosion process for cellulosic ethanol production. There is an increasing interest in utilizing lignin as a potential raw material for the chemical industry in the past two decades, due to the its immense quantities produced annually and the depletion of fossil fuels as well as the environmental concerns associated with the use of fossil resources. Lignin is an amorphous macromolecule of three phenyl-propanols i.e., p-hydroxyl-phenyl propanol, guaiacyl-propanol and syringyl-propanol. These phenyl-propanols are linked mainly by condensed linkages (e.g., 5-5 and β-1 linkages), and more dominantly by ether linkages (e.g., β-O-4 and α-O-4) between the three main lignin building blocks. This macromolecule can decompose/degrade into oligomeric and monomeric phenolic compounds via thermochemical technologies (such as pyrolysis, hydrothermal liquefaction, and hydrolysis) and some biological processes. Lignin is thus attractive to many industries such as the manufacture of phenol-formaldehyde (PF) resins and adhesives, as the bio-phenols derived from lignin could potentially substitute for petroleum-based phenol in the resin synthesis. This chapter provides an overview of chemistry of PF resin synthesis, liquefaction of lignocellulosic materials and production of bio-oil-based PF resins, and the recent advances in lignin extraction, modification and de-polymerization.© 2012 Nova Science Publishers, Inc. All rights reserved.