Formic acid assisted liquefaction of lignin in water and ethanol, investigated for a 0.025 and a 5 L batch reactor: Comparison of yields and compositions of the products. (May 2019)

• Record Type: Journal Article
• Authors: Ghoreishi, Solmaz; Barth, Tanja; Derribsa, Hailegebrel
• Is Part Of: Biomass and bioenergy. Volume 124(2019)
• Page Start: 1
• Page End: 12
• Publication Date: 2019-05
• Subjects: Lignin -- Formic acid assisted -- Lignin-to-Liquid -- Hydrodeoxygenated -- Reactor volume -- Phenols; Biomass energy -- Periodicals; Biomass -- Periodicals; Energy-Generating Resources -- Periodicals; Bioénergie -- Périodiques; 333.9539
• DOI: 10.1016/j.biombioe.2019.03.004
• Languages: English
• ISSNs: 0961-9534

Abstract

Abstract: Formic acid assisted conversion of lignin to liquids (LtL-process), where lignin is hydrodeoxygenated in a one-step conversion, produces bio-oils with a molecular weight range of 300–600 Da that comprise a complex mixture of monomeric phenols, e.g., phenol, cresol, guaiacol, catechol, etc., and more hydrogenated products. This paper addresses depolymerisation of lignin at small and large lab scales and includes characterisation of the products. Lignin conversion is performed using a 5 L stirred reactor and a 0.025 L unstirred reactor to evaluate the effect of increased volume and stirring on the oil yield and oil quality. The amount of oil yields is investigated for different types of lignin/lignin-rich residues, reaction temperatures (320–380 °C), reaction times (0.75–3 h) and reaction solvents (aqueous or ethanolic), and have been shown to be highest for the 0.025 L reactor. Furthermore, the relationship between the yields and reaction conditions are systematically explored using principal component analysis (PCA). For the Eucalyptus lignin-rich residue, ethanol tends to give higher oil yields (36–52 wt%) at most of the operating temperatures compared to water as reaction solvent (20–50 wt%). At both reaction scales and both solvent-systems, oil yields tends to decrease at reaction temperatures above 350 °C due to increased char formation. Reaction time does not seem to have any significant effect on oil yield at either scale. More than 40 wt% of the input lignin can be recovered as oil at 320 °C at both scales and solvent systems. Highlights: Oil yields decrease with increased reaction temperatures above 350 °C at both scales regardless of solvent type. In water system, reaction time has no significant effect on oil yield at either scale. In comparison with water system, ethanol system gives higher oil yields that are to some degree equivalent at both scales. The bio-oil composition produced at each scale is quite stable and independent of reaction conditions. For Eucalyptus lignin, bio-oils produced at 5 L scale seem to have lower O/C ratios regardless of solvent type.