期刊
ACS SUSTAINABLE CHEMISTRY & ENGINEERING
卷 6, 期 8, 页码 10408-10420出版社
AMER CHEMICAL SOC
DOI: 10.1021/acssuschemeng.8b01763
关键词
Deep eutectic solvents; Hydrogenolysis; Lignin; Catalysis; Sorghum
资金
- National Science Foundation [1355438, 1632854]
- Kentucky Agricultural Experiment Station [18-05-062]
- U.S. Department of Energy (DOE) [DE-AC05-00OR22725]
- BioEnergy Science Center (BESC)
- Center for Bioenergy Innovation (CBI)
- Office of Biological and Environmental Research in the DOE Office of Science
Deep eutectic solvent (DES) is intrinsically cheaper than many ionic liquids (ILs) due to low precursor cost, simple synthesis, and improved recyclability. Meanwhile, DES can be as effective as ILs toward dissolving lignin from plant materials. However, the lignin depolymerization mechanism in DES, the structural and chemical properties of DES-extracted lignin (DES-EL), and the possible valorization pathways of DES-EL toward value-added products were not well understood. This study aims to characterize the lignin streams from DES (1:2 choline chloride:lactic acid) treated sorghum and further upgrade the extracted lignin to phenolic compounds. As revealed by HSQC, C-13, and P-31 NMR analysis, DES cleaved nearly all ether linkages in native lignin, resulting in significant size reduction. We further catalytically upgraded DES-EL to phenolic compounds via catalytic transfer hydrogenolysis in the presence of isopropyl alcohol. Among the three tested catalysts (Ru/C, Pd/C, and Pt/C), Ru/C proved the most effective in deconstructing DES-EL, with oil, char, and gas yields of 36.3, 46.4, 17.3 wt %, respectively. Major lignin monomeric products in the oil were phenol, 4-ethylphenol, 4-ethyl-2-methoxyphenol, 2-methoxy4-propylphenol, and 4-hydroxy-benzenepropanoic acid. This study provides a mechanistic understanding of lignin depolymerization in DES and demonstrates a possible way to catalytic upgrading of DES-EL to low molecular weight phenolic compounds.
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