Effect of Dilute Acid Pretreatment and Lignin Extraction Conditions on Lignin Properties and Suitability as a Phenol Replacement in Phenol-Formaldehyde Wood Adhesives

Abstract

Corn stover was subjected to dilute sulfuric acid pretreatment to assess the impact of pretreatment conditions on lignin extractability, properties, and utility as a phenol replacement in wood phenol-formaldehyde (PF) adhesives. It was identified that both formic acid and NaOH could extract and recover 60−70% of the lignin remaining after pretreatment and enzymatic hydrolysis under the mildest pretreatment conditions while simultaneously achieving reasonable enzymatic hydrolysis yields (>60%). The availability of reaction sites for the incorporation of lignins into the PF polymer matrix (i.e., unsubstituted phenolic hydroxyl groups) was shown to be strongly impacted by the pretreatment time and the recovery. Finally, a lignin-based wood adhesive was formulated by replacing 100% of the phenol with formic-acid-extracted lignin, which exhibited a dry shear strength exceeding a conventional PF adhesive. These findings suggest that both pretreatment and lignin extraction conditions can be tailored to yield lignins with properties targeted for this co-product application.

Production of Hemicellulose Sugars Combined with the Alkaline Extraction Lignin Increased the Hydro-Depolymerization of Cellulose from Corn Cob

“…The results regarding reaction time are consistent with the results of 2% (w/v) NaOH treatment at 120 °C, removing 88.59% of CC lignin content [16]. Another study revealed 60~70% lignin recovery using formic acid-and NaOH-pretreated corn stover [39]. The longer the reaction time, the greater the yield of lignin extraction.…”

“…It is noteworthy that when extracting lignin from holocellulose (which includes cellulose and hemicellulose), the process may degrade hemicellulose and reduce yields of sugars in subsequent conversion. Thus, it is essential to depolymerize hemicellulose before optimizing the pretreatment process for lignin extraction in order to make the most use of the holocellulose and efficiently remove lignin [17,39]. Catalytic hydrogenation can also be employed to degrade hemicellulose into xylose and arabinose, which can then be further converted into alcohols and sugar alcohols, thereby maximizing the utilization of lignocellulose.…”

Recent progress of biomass in conventional wood adhesives: a review

“…Moreover, several researchers have explored the possibility in which lignin completely replaces the phenol needed in the production of PF resin adhesive. Saulnier et al 113 pretreated corn stover with dilute sulfuric acid, and evaluated the influence of pretreatment conditions on the extractability, characteristics and utility of lignin as a substitute for phenol in wood PF adhesive. Lignin-based wood adhesive was prepared by replacing 100% phenol with lignin extracted from formic acid.…”

Lignin Modification for Enhanced Performance of Polymer Composites

“…Acid–based catalysts such as HCl, H 2 SO 4 , HNO 3 , and CH 3 COOH are frequently used since they are inexpensive and may change the crystal structure of cellulose and degrade the hydrogen bonds among cellulose and units of glucose, producing lignocellulosic biomass less resistant. − In enzymatic saccharification, it has been shown that good sugar yields can be obtained with the use of acid pretreatment . The lignin and hemicellulose sections of the biomass are the only parts of the biomass that are selectively subjected to acid pretreatment.…”