A new method of the catalytic alcoholysis of Dioscorea zingiberensis C. H. Wright into diosgenin by magnetic solid acid in a Teflon-lined stainless-steel autoclave for the first time. The magnetic solid acid, Fe 3 O 4 @SiO 2 –SO 3 H, was prepared by the connecting the –SO 3 H groups on the surface of SiO 2 encapsulated Fe 3 O 4 microspheres . The synthesized catalysts were systematically analyzed by Fourier transform infrared (FT-IR) spectroscopy, thermogravimetric analyzer (TGA), X-ray diffraction (XRD), vibrating sample magnetometry (VSM), temperature programmed desorption of ammonia (NH 3 -TPD), scanning electron microscope (SEM), transmission electron microscope (TEM) and transmission electron microscope-mapping(TEM-mapping). To obtain the best conditions for the alcoholysis of Dioscorea zingiberensis C. H. Wright, single factor test was first utilized to determine the range of optimal conditions and optimized by response surface method . A three-level-three-factor Box-Behnken design was adopted to illustrate the effect of solid acid mass, solvent volume, reaction time and temperature on the yield of diosgenin. The optimum conditions obtained by response surface methodology were: 0.42 g Fe 3 O 4 @SiO 2 –SO 3 H, 4.38 mL solvent of ethanol, the reaction temperature at 100 °C and 6.09 h reaction time. At the optimal conditions, this method can reach the highest yield 2.64% from Dioscorea zingiberensis C. H. Wright. The yield of the new method was 21.66% higher than conventional sulfuric acid hydrolysis based on the analysis results of UV and HPLC. Importantly, the catalysts and solvents used in the alcoholysis process by the solid acid can be recovered, which is green and environmentally friendly, indicating that the catalytic alcoholysis with magnetic solid acid under hydrothermal conditions had a broad application prospect in diosgenin production.
In this work, a sulfonic acid-functionalized magnetic separable solid acid (Fe 3 O 4 @SiO 2 -SO 3 H) was synthesized, characterized, and tested for fructose conversion to 5-hydroxymethylfurfural (HMF). Results indicated that the prepared catalyst had a good efficacy for fructose dehydration to HMF due to its larger specific surface area, appropriate acid amount and homogeneous acid distribution. The maximum HMF yield of this work was 96.1 mol%. It was obtained at 120 °C for 1.5 h with 100 mol% fructose conversion. More importantly, the produced HMF could be further in-situ oxidized into 2,5-diformylfuran (DFF) after the replacing of the Fe 3 O 4 @SiO 2 -SO 3 H with a ZnFeRuO 4 catalyst, and the highest DFF yield of 90.2 mol% (based on initial fructose) was obtained after reaction another 8.5 h. The production of DFF from fructose through the above two consecutive steps avoids the intermediate HMF separation, which saves time and energy. In addition, both Fe 3 O 4 @SiO 2 -SO 3 H and ZnFeRuO 4 catalysts exhibited satisfied stability in the recycling experiments, which can be reused at least for five times with the HMF and DFF yield loss<5.3% and 3.3%, respectively. Finally, the plausible reaction mechanisms for fructose conversion to HMF or DFF over Fe 3 O 4 @SiO 2 -SO 3 H or/and ZnFeRuO 4 catalysts were also proposed in this work.
危险品化学品经营许可证（带存储）