Title
Molecular and spectroscopic characterization of technical lignin from Trema orientalis and Trewia nudiflora obtained from formic acid biorefinery
Authors
MD. NUR ALAM LIKHON, SHARMIN ISLAM, M. MOSTAFIZUR RAHMAN, BO JIANG, YANGCAN JIN and M. SARWAR JAHAN

Received January 30, 2025
Published Volume 59 Issue 5-6 May-June
Keywords hardwood, formic acid treatment, cellulose, resin, furfural

Abstract
Biorefinery has emerged as one of the most prominent topics in recent research, playing a crucial role in establishing a circular bioeconomy. Trema orientalis and Trewia nudiflora, which are experimentally planted in social forestry in Gazipur district of Bangladesh, are very similar both anatomically and chemically. These two species were fractionated by formic acid (FA) into pulp, hemicelluloses and lignin. In this investigation, the lignin from the FA spent liquor was characterized in terms of molecular weight, and by UV, FTIR, 2D-NMR, 31P NMR spectroscopy to better understand the lignin structure for its reactivity. The weight average molecular weights (Mw) were 10,826 and 8,784, while OCH3/C9 units were 1.3 and 1.0 for T. orientalis and T. nudiflora, respectively. The lignins had almost similar aliphatic OH (1.23 mmole/g vs 1.15 mmole/g) and phenolic OH (2.3 mmole/g and 2.26 mmole/g) contents. As observed from the 2D-NMR, the lignins were constituted of S units, followed by G units, and the S/G ratios were 1.56 and 1.15 for T. orientalis and T. nudiflora, respectively.