Oxidative Depolymerization of Lignin Using a Novel Polyoxometalate-Protic Ionic Liquid System

Abstract

Oxidative depolymerization of lignin obtained from pine and willow can be achieved in a novel system encompassing the ionic liquid (IL) 1-butylimidazolium hydrogensulfate coupled with a vanadium based polyoxometalate (POM) under oxygen rich conditions. Along with an array of phenols and functionalized aromatics, vanillin and syringaldehyde were the main products extracted from the IL. The overall yield of aldehyde products were shown to be higher on lignin samples obtained with shorter pretreatment times, with vanillin being the exclusive aldehyde product obtained from pine. In the presence of molecular oxygen, the highest yield of aldehyde products was obtained when 5 wt % of the POM relative to the IL was employed and constituted the major product in the extracted oils. This system succeeds in exploiting the ability of ILs to depolymerize lignin and the remarkable properties of the POM to oxidize the lignin fragments into useful platform chemicals

Catalytic Oxidation and Depolymerization of Lignin in Aqueous Ionic Liquid

“…Yield (%) with respect to the loaded lignin ranged from 0.26 to 0.99 for Nb2O5 catalyst and from 0.41 to 0.90 for CoCl2 catalyst, respectively, under the tested conditions. The product yields obtained from this study were comparable with results from previous studies using vanadium-based POM in presence of IL 1-butylimidazolium hydrogen sulfate and H2O2 with a product (vanillin, syringaldehyde, and guaiacol) yield of 0.055% (De Gregorio et al, 2016;Prado et al, 2016a). Low product yield in this study may be due to repolymerization of depolymerized lignin and/or over-oxidization products to other intermediates which were not detected in the GC/MS.…”

Effect of Solvent, Role of Formic Acid and Rh/C Catalyst for the Efficient Liquefaction of Lignin

“…Recently ionic liquids (ILs) are extensively used for the conversion of cellulose, hemicellulose, and lignin into various value‐added chemicals . ILs have been employed as the solvent, additives, catalyst, etc.…”

Oxidative Depolymerization of Lignin Using Supported Niobium Catalysts

“…The yields obtained in our research were lower than those reported by other researchers. For example, De Gregorio et al [33] employed vanadium-based polyoxometalate as a catalyst in the presence of ionic liquid (IL) 1-butylimidazolium hydrogensulfate. The reported product yields for vanillin, syringaldehyde, and guaiacol were 0.055% with respect to lignin.…”