(170a) Influence of Dilute Acid Pretreatment and Lignin Extraction Conditions on Lignin and Phenol Formaldehyde Resin Properties

The type of feedstock used, pretreatment employed, and method of lignin extraction/purification all influence the properties of lignins extracted from a biorefinery process. Structural and chemical properties of a specific lignin such as phenolic hydroxyl content and molecular weight affect the ability of a lignin to be incorporated into phenol formaldehyde (PF) resins for wood adhesives, and the subsequent material properties of the formulated adhesives. Our previous studies have shown that lignin generated from NaOH extraction of dilute acid pretreated corn stover can be used to formulate PF resins with 100% of phenol replaced which exhibit material properties that exceed industrial resin standards. We have previously hypothesized that the improved lignin incorporation in this study is largely due to high amounts of p-coumarate (pCA) present within grass lignins presenting additional phenolic hydroxyls for reaction with formaldehyde. In a previous study we have identified dilute acid pretreatment conditions that result in high hydrolysis yields while retaining high pCA levels within the biomass. In this study we expand on those finding by using corn stover to investigate a wide range of dilute acid pretreatment conditions, varying enzymatic hydrolysis conditions, and two different lignin extraction processes using sodium hydroxide and formic acid. These varied conditions were used to create a panel of lignins with varying properties which were completely characterized and the most promising lignins were chosen for scaled up production and PF resin adhesive formulation. Using optimized dilute acid pretreatment conditions and formic acid extraction we were able to formulate lignin-formaldehye resins which exceeded properties of previously formulated resins.