Oxidative conversion of lignin isolated from wheat straw into aromatic compound catalyzed by NaOH/NaAlO2

• Published in: Food science & nutrition Vol. 8; no. 7; pp. 3504 - 3514
• Main Authors: Luo, Ke‐Hui, Zhao, Si‐Jiu, Fan, Guo‐Zhi, Cheng, Qun‐Peng, Chai, Bo, Song, Guang‐Sen
• Format: Journal Article
• Language: English
• Published: Malden, Massachusetts John Wiley & Sons, Inc 01.07.2020; John Wiley and Sons Inc
• Subjects: Aldehydes; Aqueous solutions; aromatic compound; Aromatic compounds; Catalysts; Cellulose; Chemicals; Chromatography; composite catalyst; Conversion; Infrared spectrometers; Infrared spectroscopy; Lignin; Lignocellulose; Magnetic resonance spectroscopy; Mass spectrometry; Nitrobenzene; NMR; Nuclear magnetic resonance; Original Research; Oxidants; Oxidation; oxidative conversion; Oxidizing agents; Polymers; Scientific imaging; Sodium aluminate; Sodium hydroxide; Straw; Syringaldehyde; Vanillin; Wheat; Wheat straw; China
• ISSN: 2048-7177; 2048-7177
• DOI: 10.1002/fsn3.1633

Lignin was isolated from wheat straw via organosolv process and further transferred to monophenolic compounds via oxidative conversion. Wheat straw lignin (WSL) with purity at 91.4 wt% was acquired in the presence of heterogeneous and recyclable catalyst of Amberlyst‐45. WSL was characterized by infrared spectrometer (IR), nuclear magnetic resonance spectroscopy (NMR) including 1H NMR and 13C NMR spectra. The results showed that WSL possesses typical syringyl (S), guaiacyl (G), and p‐hydroxyphenyl (H) units, and it is mainly composed of S and G units. The product distribution was dependent on the composition of WSL. Derivatives from S and G units were found to be the main products. The oxidative conversion of WSL was performed by varying oxidant and catalyst. Both the formation of monophenolic compounds and aromatic aldehydes were enhanced by combining oxidants and catalysts. The composite catalyst composed of NaOH/NaAlO2 was effective for the oxidation of WSL in the presence of nitrobenzene and atmospheric pressure air. The total yield of monophenolic compounds reached up 18.1%, and yields at 6.3 and 5.7% for syringaldehyde and vanillin were achieved, respectively. The oxidative conversion of lignin isolated from wheat straw into aromatic compounds was investigated. Wheat straw lignin with high purity at 91.4 wt% was first isolated via organosolv process in the presence of green and recyclable catalyst of Amberlyst‐45. The oxidative conversion of lignin was then performed using NaOH/NaAlO2 as composite catalyst, and the total yield of monophenolic compounds reached 18.1%.