• Ferdosian, Fatemeh
• Siddiqui, Homaira
• Li, Bing
• Schmidt, John
• Paleologou, Michael
• Mahmood, Nubla
• Yuan, Zhongshun
• Huang, Shanhua

Abstract

According to the International Lignin Institute, about 40-50 million tonnes of kraft lignin (KL) are generated worldwide each year in the form of “black liquor”. While combustion of black liquor to regenerate pulping chemicals and to produce steam and power is an integral part of the kraft process, a small portion of the lignin can be removed without compromising mill material and energy balances. This presents an opportunity for revenue diversification, if value-added applications for kraft lignin can be identified. The interest in kraft lignin has reached a critical juncture. A commercial-scale, 75 t/d, lignin plant has been in operation since 2013 at Domtar’s Plymouth, North Carolina mill, and projects with targeted capacities of 30 t/d and 142 t/d are under construction in Hinton, Canada and Sunila, Finland, respectively. The production of platform chemicals (e.g., lactic, succinic and other organic acids) from sugars is growing and the next generation of these technologies seek to use cellulose-derived sugar feedstocks. For this to be realized commercially, value-added applications are needed for the hydrolysis lignin (HL) by-products that are generated from cellulose hydrolysis. Value-added lignn by-products are also needed if the struggling cellulosic ethanol industry is ever to become commercially viable. Direct use of KL and HL in many biocomposite materials is difficult because the molecular weight is too high and because reactivity is reduced due to steric hindrance effects. Our approach to broaden the range of applications for both KL and HL has been to depolymerize the starting lignin to a mixture of monomers and oligomers. Compared with the original lignins, depolymerized lignins (DLs) are more chemically reactive as substitutes for petroleum-based chemicals (phenol, polyols and bisphenol-A) owing to their smaller molecular weights, reduced steric hindrance effects and more active functional groups. This paper presents some recent results achieved in the authors’ group on various technologies for lignin depolymerization, focusing on hydrolytic de-polymerization and reductive depolymerization, as well as production of bio-based phenolic resins, polyurethane foam and epoxy resins using the DLs, and their applications in wood adhesives and composites. © VTT 2015.

Topics

• impedance spectroscopy
• reactive
• composite
• combustion
• lignin
• wood
• molecular weight
• cellulose
• resin
• dynamic light scattering