Abstract

Lignin is primarily used to produce energy in the pulp and paper industry. However, given its phenolic structure and the presence of varied functional groups (phenolic hydroxyl, aliphatic hydroxyl, carboxyl, methoxyl and carbonyl), lignin could be a valuable raw material for the production of carbon fibers, active carbon, epoxy resins, phenolic adhesives, emulsifiers, and several other compounds. A novel, selective chemo-enzymatic process to generate epoxide structures was developed. A lipase (Candida antarctica lipase B, Novozyme 435 R (EC 3.1.1.3)) catalyzed the formation of peroxyacids from fatty acids in the presence of hydrogen peroxide. The peroxyacids were then reacted with unsaturated vegetable oils for the formation of oxirane rings through of the epoxidation of the C=C bond. Similar protocols were applied to a lignin degradation model compound (vanillic acid) and to processed lignin in order to generate epoxide structures. Lignin obtained from the Organosolv pretreatment of Eucalyptus globulus chips was fractionated following several treatments. The resulting lignins were characterized using gel permeation chromatography (GPC) to determine molecular weight and using 31-P nuclear magnetic resonance (NMR) to quantify the phenolic OH content. The lignin and a control (vanillic acid) are allylated, then exposed to the lipase, caprilic acid and hydrogen peroxide for chemo-enzymatic generation of oxirane rings, creating functional pre-polymers for the synthesis of epoxy adhesive resins.