Ionic Liquid Gels as Novel Catalysts in Application of Esterification for N-bornyl Acetate
LIU Huiru1, ZHANG Miaomiao2, XU Zhice2,*
1 School of Chemical and Engineering, Shijiazhuang University, Shijiazhuang 050035, China 2 School of Chemical and Pharmaceutical Engineering, Hebei University of Science and Technology, Shijiazhuang 050018, China
Abstract: N-bornyl acetate (BA) is widely applied as pharmaceutical intermediate. Inorganic acids are mostly used as catalysts for the synthesis of BA. However, these problems such as poor selectivity, difficult separation of product and catalyst, etc., limit their applications. Ionic liquid have received attention in catalytic esterification due to their advantages. However, the reusability of ionic liquids hinders the application in industry. Thermo-sensitive ionic liquid gels, as a new catalyst, can break through the technical bottleneck of industrialization. In this work, the novel ionic liquid gels were synthesized using poly (vinyl alcohol), tannic acid and acidic ionic liquids. The stability and structure of ionic liquid gels were characterized by Rh, TGA, FTIR,1H NMR, et al. The results showed that ionic liquid gel with high mechanical strength and toughness was a double-network polymer due to the carboxylic ester bond and π-π stacking interaction, which formed by hydrogen bond, imidazole and benzene ring. The synthesis of BA was chosen to evaluate the catalytic activity of ionic liquid gels. The reaction temperature and the reaction time was 90 ℃ and 6 h, respectively. The optimal molar ratio of α-pinene to acetic acid was 1∶1. The results showed that the gel catalysts had thermo-reversibility. At high temperature, the ionic liquid gels transformed to a sol, in which the catalytic reaction performed in a homogeneous sol state; when the temperature decreased, the catalyst became a gel, which endowed the efficient separation of catalyst and product. The catalytic activity of the ionic liquid gels was similar to the ionic liquid. At the optimized conditions, the ionic liquid gels catalyst could be reused for 5 times. The convertion rate of α-pinene remained 75% and selectivity of product was 8.5% above.
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2024, Vol. 38 
