Lignin oxidation and depolymerisation in ionic liquids

Abstract

The depolymerisation of lignin directly in the black liquor was studied, comparing two ionic liquids as extracting solvents (butylimidazolium hydrogen sulphate and triethylammonium hydrogen sulphate), under oxidising conditions.

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.…”

“…1 Identification and quantification of the monomeric products from the depolymerization reaction were performed by Agilent 7890B GC coupled 5977B MS with an HP-5ms (60 m × 0.32 mm) capillary column. The temperature program started at 50°C and increased to 120°C at 10°C min −1 with a holding time of 5 min; then it was raised to 280°C at 10°C min −1 with a holding time of 8 min and to 300°C at 10°C min −1 with holding time of 2 min (Prado et al, 2016a). Helium was used as a carrier gas at a flow rate of 1.2 mL min −1…”

“…Catalyst and H2O2 were both loaded at 5 wt% loading (IL + lignin); the screening experiments were conducted at 120°C and a reaction time of 3 h (Prado et al, 2016a). Identification and determination of product formation and concentration were performed according to the batch experiments mentioned in the Section "Lignin Depolymerization, Extraction, and Analytical Method.…”

“…Lignin's full potential as a renewable source for aromatic compounds can be, in part, unlocked only if an efficient and economic method for lignin depolymerization and valorization is developed (Prado et al, 2016a). The heterogeneity of lignin (both in its varied bond chemistry and its variability between plants), however, is the major hurdle to its targeted upgrading and reuse as a feedstock for chemicals and advanced materials (Das et al, 2012).…”

“…It was suggested that the anion of IL is the dominating factor influencing lignin dissolution as compared with cation. The affinity in which anions intereacting with lignin is in the order of sulfate > lactate > acetate > chloride > phosphate (Prado et al, 2016a).…”