Modification of chitosan-coated magnetic material with glycidyltrimethylammonium chloride and its application as heterogeneous base catalyst for levulinic acid esterification

Abstract

To promote more widespread use of biodiesel, it is essential to add additives to improve its fuel properties, and one such additive is ethyl levulinate (EL). EL is often produced by acid-catalyzed esterification of levulinic acid (LA) with ethanol, but acid catalysis has a critical problem of low catalytic activity. This problem can be solved by using a base catalyst for this reaction. In the present study, we developed a novel composite material that was composed of natural magnetic material (MM), which was obtained from iron sand, with chitosan (Chi) and glycidyltrimethylammonium chloride (GTMAC), and applied it as a base catalyst for esterification of LA to EL. In the first step, the surface of MM was modified with chitosan in 1% acetic acid, and then it was further modified with GTMAC at room temperature. The obtained composite (MM/Chi/GTMAC) was comprehensively characterized by various physical and chemical methods to verify that it had a core (MM)–shell (Chi/GTMAC) structure as expected. In addition, TPD measurements demonstrated that MM/Chi/GTMAC had base sites owing to chloride ions in GTMAC. MM/Chi/GTMAC exhibited high catalytic performance for esterification of LA to EL and 77% of EL yield, and 89% of LA conversion were achieved at 80 °C for 6 h, while MM and MM/Chi showed only little catalytic activity for EL formation. Additionally, the catalyst was reusable, while the performance was gradually decreased with each repeated use for the reaction.