Chemical Modification of Softwood Kraft Lignin with Succinic Acid

This work explored the chemical modification of lignin with succinic acid for the first time. Temperature is crucial for the process, reducing reaction time and increasing conversion. In particular, at 160 °C for five h with 0.13 mol of imidazole and 0.35 mol of succinic acid, the reaction showed the most significant reduction in glass transition temperature (from 183.3 to 118.5 °C) and a decrease in the polydispersity index (from 11.31 to 8.96) and yielded 0.73 mmol g^-1 of new succinic acid groups. These results underscore the critical role of reaction conditions in modifying lignin properties, potentially expanding its application range and enhancing its value.