Abstract
An efficient and green approach for the synthesis of cyclododecanone oxime (CDOX) via a zeolite-catalyzed indirect transoximation reaction has been developed in this work. The effects of topological structure, pore size, acidity of zeolites and solvent on the transoximation reaction were investigated. The results indicated that HBeta-21 zeolite promoted the cyclododecanone (CDON) conversion of 64.41% in ethanol-H2O, which was higher than that of 44.52% in ethanol. The pore size and the Brønsted acidic amounts of zeolites are important factors in ethanol, while the maximum conversions were obtained in ethanol-H2O despite the topological structure and SiO2/Al2O3 ratio of zeolites. The results of in-situ FT-IR, 2H MAS NMR, H218O and the hydrolytic behavior of cyclohexanone oxime (CHO) indicate that hydroxylammonium (NH3OH+) generated in-situ in ethanol-H2O system is the key active species for the better transoximation performance. It means that the transoximation reaction is carried with NH3OH+ as an intermediate, which is different from that in ethanol solvent. The reaction kinetics and the activation energy were determined in different solvents and the zeolite catalyst can be recovered and reused for more than 10 cycles in ethanol-H2O. The indirect transoximation reaction provides a new path for the utilization of CHO and the production of high value-added CDOX.