Characteristics of potassium hydroxide lignin from corn stalk and dhaincha

Abstract

Abstract Non-wood pulping faces environmental and processing problems due to lack of suitable technology. To overcome the challenges, potassium hydroxide pulping was suggested, which can also be integrated with biorefinery. To make a viable biorefinery, all dissolved components need to be utilized. Therefore, in this paper, the dissolved lignin from the potassium hydroxide pulping of corn stalks and dhaincha was isolated and characterized by UV, FTIR, 1H-NMR, 31P-NMR and 2D-NMR spectroscopy and molecular weight and compared with the corresponding dioxane lignins. 1H-NMR and 2D-NMR indicated that potassium hydroxide pulping cleaved β-O-4 aryl ether linkages, and consequently increased phenolic hydroxyl group and reduced molecular weight. It was found that phenolation is an effective method to improve the reactivity and reduce molecular weight, and thus the lignin from the potassium hydroxide liquor was further phenolated. The penolated lignin showed strong NIR bands at 5970 and 6896 cm−1 for aromatic C-H and phenolic O-H group.