Acid catalysts based on simple modification of chitosan for the esterification of oleic acid

ABSTRACT Chitosan is a linear polymer with excellent physicochemical properties and has been widely used in a variety of applications, including as a catalyst in various types of reactions. In this work, chitosanbased solids were synthesized in order to obtain an active and stable material to be used as a catalyst in esterification reactions. To this end, the chitosan was modified in order to potentiate its Bronsted acidity by acid hydrolysis using HCl or H2SO4 solutions and subsequent drying in a vacuum line. The synthesized materials were characterized and evaluated in the esterification reaction of oleic acid with methanol. Although modification of chitosan with dilute solutions of inorganic acids is a simple method for the preparation of heterogeneous acid catalyst, there is evidence that the materials are not stable against the leaching of the active species into the reaction medium under the conditions evaluated.

摘要 壳聚糖（Chitosan）是一类具备优异理化性能的线性聚合物，已被广泛应用于诸多场景，其中包括作为各类反应的催化剂。本研究旨在制备活性与稳定性俱佳的催化材料，用于酯化反应，故合成了壳聚糖基固体材料。具体而言，通过采用氯化氢（HCl）或硫酸（H2SO4）溶液对壳聚糖进行酸水解改性，以增强其布朗斯特（Bronsted）酸度，随后在真空条件下完成干燥。对所合成的材料开展了理化表征，并在油酸与甲醇的酯化反应体系中评估其催化性能。尽管利用无机酸稀溶液改性壳聚糖是制备非均相酸催化剂的简便手段，但已有研究证据显示，在所评估的反应条件下，该类材料的活性组分易向反应介质中浸出，稳定性存在不足。