Reactive organosolv lignin extraction from wheat straw: Influence of Lewis acid catalysts on structural and chemical properties of lignins

• Published in: Industrial crops and products 2015-03, Vol.65, p.180-189
• Main Authors: Constant, Sandra, Basset, Charlie, Dumas, Claire, Di Renzo, Francesco, Robitzer, Mike, Barakat, Abdellatif, Quignard, Françoise
• Format: Article
• Language: English
• Subjects: Acid pulping; Agricultural sciences; Biomass pre-treatment; Catalysis; Characterization; Chemical Sciences; Lewis acids; Life Sciences; Lignocellulose; Material chemistry; Sciences and technics of agriculture; Silviculture, forestry
• ISSN: 0926-6690; 1872-633X
• DOI: 10.1016/j.indcrop.2014.12.009

[Display omitted] •Lewis acids were studied as catalysts in the organosolv treatment of wheat straw.•The harder Lewis acids allowed a greater degree of delignification.•Molecular masses of the lignins were in the range 3–8kg/mol.•Lignins present different structural and chemical properties. Lewis acids have been studied as catalysts in the organosolv treatment of wheat straw. Fractionation of the lignocellulosic biomass and fragmentation of lignin have been performed in aqueous ethanol in the presence of FeCl2, CuCl2, FeCl3, Ga(OTf)3, ZrOCl2 or Sc(OTf)3. The lignins were characterised in terms of molecular weight, βO4 linkage content and chemical functions through size exclusion chromatography; thioacidolysis; 31P and 13C NMR spectroscopies. The degree of delignification and the yield of Klason lignin increased with the hardness of the Lewis acid. About half of the delignification products were water-soluble monomers and oligomers. The nature of the Lewis acid influenced also the characteristics of the precipitated lignins. The molecular mass, the amount of OH groups and of aliphatic CO bonds decreased as cation hardness increased.