Preparation and characteristic analysis of rice husk high boiling solvent lignin

Abstract

Rice husk high boiling solvent lignin (RHL) was prepared by high boiling solvent method, and its characteristics was analyzed by using chemical composition analysis, infrared spectroscopy, and ¹H-NMR and ¹³C-NMR spectroscopy. The optimum prepared condition was that the rice husk with 70%–90% aqueous solution of 1, 4-butanediol was mixed with autoclave, under a certain weight ratio of solid raw material and solvent, heated to 200–220°C for 1.0–3.0 h, then water-insoluble RHL was separated from the liquor reaction mixture by water precipitation. Results suggested that the lower digestion temperature and concentration of 1,4-butanediol were both unfavorable for extracting lignin. Chemical weight-average molecular weight of RHL was 1939 g·mol⁻¹, and the residual polysaccharide content was 5.12%. The ¹H-NMR spectra of RHL showed the relative intensity ratio, aliphatic over aromatic methoxyl groups, situated at 3.5–3.8 and 3.8–4.0 ppm, respectively. The results from ¹³C-NMR spectra showed that β-O-4 bond and β-5 carbon-carbon linkage were the major linkages between RHL units. The C₉-formula of RHL was calculated by the experiment data.

Keywords

high boiling solvent method / rice husk lignin / C₉-formula

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