Thio-assisted reductive electrolytic cleavage of lignin β-O-4 models and authentic lignin. Issue 1 (21st December 2020)

• Record Type: Journal Article
• Authors: Fang, Zhen; Flynn, Michael G.; Jackson, James E.; Hegg, Eric L.
• Is Part Of: Green chemistry. Volume 23:Issue 1(2021)
• Page Start: 412
• Page End: 421
• Publication Date: 2020-12-21
• Subjects: Environmental chemistry -- Industrial applications -- Periodicals; Environmental management -- Periodicals; 660
• DOI: 10.1039/d0gc03597a
• Languages: English
• ISSNs: 1463-9262

Abstract

Abstract : Disulfide-enhanced electroreductive cleavage of oxidized lignin β-O-4 dimers. Abstract : Avoiding the use of expensive catalysts and harsh conditions such as elevated temperatures and high pressures is a critical goal in lignin depolymerization and valorization. In this study, we present a thio-assisted electrocatalytic reductive approach using inexpensive reticulated vitreous carbon (RVC) as the working cathode to cleave the β-O-4-type linkages in keto aryl ethers. In the presence of a pre-electrolyzed disulfide (2, 2′-dithiodiethanol) and a radical inhibitor (BHT) at room temperature at a current density of 2.5 mA cm −2, cathodic reduction of nonphenolic β-O-4 dimers afforded over 90% of the corresponding monomeric C–O cleavage products in only 1.5 h. Extended to DDQ-oxidized poplar lignin, this combination of electric current and disulfide, applied over 6 h, released 36 wt% of ethyl acetate soluble fragments and 26 wt% of aqueous soluble fragments, leaving only 38 wt% of insoluble residue. These findings represent a significant improvement over the current alone values (24 wt% ethyl acetate soluble; 22 wt% aqueous soluble; 54 wt% insoluble residue) and represent an important next step in our efforts to develop a mild electrochemical method for reductive lignin deconstruction.