Heterogeneous catalysis on chitosan-based materials: a review

Chitosan is an optically active biopolymer that is characterized by a strong affinity for transition metals. The polymer can be used as a support for the preparation of heterogeneous catalysts in the form of colloids, flakes, gel beads, fibers (including hollow fibers), or immobilized on inorganic supports (alumina, silica, or other metal oxides). The conformation of the polymer (together with its flexibility) is an important advantage for this kind of application. The ease with which it can be modified physically and chemically opens up avenues for manufacturing a wide range of catalysts for applications in the fields of hydrogenation, oxidation, and fine chemical synthesis reactions. This review summarizes the main advances published over the last 15 years, outlining the procedures for preparing these materials, describing how they are tested in a series of reactions and discussing the main controlling parameters that should be taken into account in order to optimize their catalytic activity.