The chitosan was found to possess an excellent catalytic performance in n-butyraldehyde self-condensation to 2E2H. Under suitable conditions, the conversion of n-butyraldehyde, the yield and selectivity of 2E2H separately attained 96.0%, 86.0% and 89.6%. The chitosan catalyst could be recovered and used for 5 times without a significant deactivation after being treated with ammonium hydroxide. In order to elucidate the reaction mechanism, the adsorption and desorption of n-butyraldehyde on the surface of chitosan were studied using in situ FT-IR spectroscopy analysis. The result showed that n-butyraldehyde interacts with -NH2 group of chitosan to form an intermediate species with an enamine structure. Then the reaction process of n-butyraldehyde self-condensation was monitored by React-IR technique and it was found that n-butyraldehyde self-condensation to 2-ethyl-3-hydroxyhexanal followed by a dehydration reaction to 2-ethyl-2-hexenal. On this basis, chitosan-catalyzed n-butyraldehyde self-condensation reaction mechanism was speculated and its reaction kinetics was investigated. The self-condensation reaction follows auto-catalytic reaction characteristics and then the corresponding kinetic model was established. (C) 2019 The Chemical Industry and Engineering Society of China, and Chemical Industry Press Co., Ltd. M rights reserved.