失活TS-1高效催化环己烯水合生成环己醇的研究

Cyclohexanol is an important chemical intermediate material. At present, ZSM-5 is mainly used as a catalyst in the industry to produce cyclohexanol by one-step hydration of cyclohexene. Its core is the development of high-performance catalysts. TS-1 is a high efficient catalyst for industrial liquid-phase ammoniation of cyclohexanone, which shows a typical Brønsted acidity after deactivation. Based on this, we applied the deactivated TS-1 as catalyst for cyclohexene hydration reaction, and investigated systematically the effects of reaction time, reaction temperature, catalyst dosage and mass ratio of water to oil on the hydration reaction of cyclohexene. The results showed that the deactivated TS-1 could offer a high catalytic performance with 11.0% yield and 99.8% selectivity towards cyclohexanol under the optimized reaction conditions, which indicated that the deactivated TS-1 is a high-performance catalyst and possesses the characteristics of high activity, high selectivity and high stability. Combined with nitric acid treating modification, potassium ion exchange experiment and the characterization techniques such as UV-Vis (UV-visible spectroscopy), FT-IR (Fourier transform infrared spectrometer), ²⁹Si MAS NMR (²⁹Si magic angle solid nuclear magnetic resonance), and NH₃-TPD (temperature-programmed desorption of ammonia), it was found that the deactivated TS-1 possesses two kinds of Brønsted acid sites, whereas its real active center for the hydration reaction of cyclohexene is silanol group adjacent to titanium hydroxyl group (Si-OH(Ti)). The structure of this Brønsted acid site is completely different from the skeleton bridge Brønsted acid site (Si-(OH)-Al) of ZSM-5 zeolite, meanwhile shows relatively weak acid strength. The unique acid property of Si-OH(Ti) could promote the main reaction path of cyclohexanol formation and inhibit the side reaction path of cyclohexene isomerization in cyclohexene hydration reaction, which determined its characteristic of high cyclohexanol selectivity. The discovery and application of the special Brønsted acid site of the deactivated TS-1 waste catalyst can provide a new idea for resource utilization of solid waste resources of spent catalyst.