Esterification of levulinic acid into n-butyl levulinate catalyzed by sulfonic acid-functionalized lignin-montmorillonite complex
Wenguang Zhao, Hui Ding, Jie Zhu, Xianxiang Liu, Qiong Xu, Dulin Yin
Abstract
In this study, sulfonic acid-functionalized lignin-montmorillonite complex (LMT-SO3H) was prepared and employed as an efficient heterogeneous catalyst for the esterification of levulinic acid (LA) into n-butyl levulinate (BL). An intermediate pseudo-butyl levulinate (p-BL) was determined by distilled water treatment and nuclear magnetic resonance (NMR) analysis, and a possible mechanism for the esterification of LA is proposed. The effects of various process parameters were studied and the results showed that the LMT-SO3H catalyst had the excellent catalytic performance for esterification of the LA. Under optimum reaction conditions, the yield of BL was 99.3% and the conversion of LA was 99.8%. The LMT-SO3H catalyst exhibited strong acidic sites and high stability even after seven cycles of usage. Furthermore, esterification of the LA with various alcohols over the LMT-SO3H was further investigated