Quenching of reactive intermediates during mechanochemical depolymerization of lignin

• Published in: Catalysis today 2018-03, Vol.302, p.180-189
• Main Authors: Brittain, Alex D., Chrisandina, Natasha J., Cooper, Rachel E., Buchanan, Michael, Cort, John R., Olarte, Mariefel V., Sievers, Carsten
• Format: Article
• Language: English
• Subjects: Ball mill; Biomass; Hydrolysis; Mechanocatalysis; Organosolv lignin; Scavenger
• ISSN: 0920-5861; 1873-4308
• DOI: 10.1016/j.cattod.2017.04.066

[Display omitted] •Mechanochemical depolymerization of lignin with sodium hydroxide is investigated.•The majority of depolymerization occurs within the first 10min of milling.•Addition of methanol as a scavenger decreases effects of condensation reactions.•Increasing moisture content will also result in more effective depolymerization.•Too much excess water leads to plasticization and ineffective milling. Mechanochemical reactions are performed to depolymerize organosolv lignin with sodium hydroxide in a mixer ball mill. GPC analysis reveals that rapid depolymerization into small oligomers occurs within minutes of milling time, followed by a slower reduction in average relative molecular mass over the next 8h of milling. Monomeric products are identified by GC–MS and quantified by GC-FID. The extent of depolymerization appears to be limited by repolymerization reactions that form bonds between products. Suppression of these repolymerization reactions can be achieved through the addition of methanol as a scavenger or adjustment of the moisture content of the feedstock. These modifications result in lower average relative molecular masses and higher yields of monomers. These results are an important step towards designing an efficient pathway for lignin valorization.