Valorization of Rice Straw via Hydrotropic Lignin Extraction and Its Characterization

Abstract

Rice straw hydrotropic lignin was extracted from p-Toluene sulfonic acid (p-TsOH) fractionation with a different combined delignification factor (CDF). Hydrotropic lignin characterization was systematically investigated, and alkaline lignin was also studied for the contrast. Results showed that the hydrotropic rice straw lignin particle was in nanometer scopes. Compared with alkaline lignin, the hydrotropic lignin had greater molecular weight. NMR analysis showed that β-aryl ether linkage was well preserved at low severities, and the unsaturation in the side chain of hydrotropic lignin was high. H units and G units were preferentially degraded and subsequently condensed at high severity. High severity also resulted in the cleavage of part β-aryl ether linkage. 31P-NMR showed the decrease in aliphatic hydroxyl groups and the increasing carboxyl group content at high severity. The maximum weight loss temperature of the hydrotropic lignin was in the range of 330–350 °C, higher than the alkaline lignin, and the glass conversion temperature (Tg) of the hydrotropic lignin was in the range of 107–125 °C, lower than that of the alkaline lignin. The hydrotropic lignin has high β-aryl ether linkage content, high activity, nanoscale particle size, and low Tg, which is beneficial for its further valorization.

Recent advances in hydrotropic solvent systems for lignocellulosic biomass utilization

“…9b). 122 The authors discussed the correlation between delignification reaction rate and CDF. The higher CDF signified the overall severity of the reaction, and the result showed that the lignin removal leveled at large CDF values.…”

“…128 The method showed high extraction efficiency (78%) and purity (78%) of the separated lignin. Freeze-thaw leads to effective lignin separation 122 while preventing oxidative degradation of lignin and hemicellulose dissolution. Consequently, the process yields highpurity lignin with elevated molecular weight.…”

“…9 Performance and application of fractionated components by p-TsOH. (a) ethanol production from poplar wood (Copyright 2013 Elsevier) 52 and (b) combined delignification factors (CDF) of straw hydrotropic lignin (Reproduced with permission from C. Yin et al, Molecules; published by MDPI, 2021) 122.…”

One-Step Precise Characterization of Drug Delivery Systems by PULCON Magnetic Resonance Spectroscopy

“…Although the PULCON method has demonstrated its advantages over other standard techniques in quantifying small molecules, 12,16 organometallic reagents, 17 and biological extract and metabolites, 11,14 its application to polymer quantification, except for occasional use in determining lignin concentration in foods, 18,19 in the context of drug delivery systems with the objective of establishing a straightforward and accurate protocol for physicochemical and pharmaceutical characterizations. Initially, the reliability and sensitivity of the PULCON protocol were assessed by examining samples with known concentrations of different polymers, either in combination or as single solutions.…”

“…Although the PULCON method has demonstrated its advantages over other standard techniques in quantifying small molecules, , organometallic reagents, and biological extract and metabolites, , its application to polymer quantification, except for occasional use in determining lignin concentration in foods, , remains largely unexplored. In this work, we investigate the applicability of the PULCON method in the context of drug delivery systems with the objective of establishing a straightforward and accurate protocol for physicochemical and pharmaceutical characterizations.…”