The Research On Conversition Of Carbohydrates Into 5-Hydroxymethylfurfural Over Double Metal Chlorides And Solid Acid

Interest in utilizing biorenewable feedstocks to produce fuels and chemicals has risen greatly in the past decade due to the economic, political and environmental concerns associated with diminishing petroleum reserves. It is urgent to search for the other renewable energy to replace the fossil fuels. Carbohydrates make up the majority of biomass and 5-Hydroxymethylfurfural(HMF) has been known as a dehydration product. Moreover, HMF has a great potential to produce bulk chemicals and fuels. Therefore, the conversion of biomass-based carbohydrates into HMF has some theoretical significance and practical value. The contents and results of this research include the following several parts:(1) Direct conversion of galactose into 5- hydroxymethylfurfural(HMF) was carried out using a combination of metal chlorides in the [AMIM]Cl/DMF binary solvent media. From high throughput screening of various metal chlorides, a combination of Cr Cl3·6H2O and Mn Cl2 in 3 : 1 molar ratio was discovered as the most effective catalyst. The optimum reaction conditions of conversion of galactose into HMF were investigated. HMF was directly afforded from galactose in nearly 35% yield at 110 ℃ with 0.08 mmol catalyst for 4 h. Furthermore, the synergistic effect of Cr Cl3 and Mn Cl2 in isomerization of galactose into tagatose was proposed in our work. Both the challenged isomerization and inef?cient dehydration of tagatose into HMF could affect the HMF yields from galactose. This work systematically studies the transformation of galactose to HMF using a easy-to-handle catalyst.(2) We have presented a synthesis route for mesoscopically assembled zirconium nanostructures(MAZN) and mesoscopically assembled sulfated zirconia nanoparticles(MASZN) with an average diameter of ca. 5.0 nm and high crystalline pore walls of mesoscopic order through evaporation- induced self-assembly method using sodium dodecyl sulfate(SDS) as the template. The materials were characterized by X-ray diffraction(XRD), FT-IR spectroscopy, NH3 temperature-programmed desorption(NH3-TPD), pyridine FT-IR spectroscopy, field emission scanning electron microscopy(FE-SEM), transmission electron microscopy(TEM), N2 sorption and thermal gravity-differential thermal gravity analysis(TG). The TEM results revealed that the mesopores were created by the arrangement of premade Zr O2 nanoparticles with sizes of 7.0-8.0 nm, whereas N2 sorption analysis revealed higher BET surface area for the MAZN and MASZN. The heterogeneous catalysts MASZN with Lewis-Br?nsted acid sites has been confirmed by FTIR and pyridine-desorption FTIR spectroscopy. The total surface acid density of MASZN-3 was 0.165 mmol/g.(3) The catalytic dehydration of fructose to 5-hydroxymethylfurfural(HMF) in DMSO was performed over a sequence of MAZN and MASZN. The effects of catalyst type and amount, reaction temperature, reaction time and solvents in the reaction were studied. The results showed that under the optimized preparation and reaction conditions, a 91.9% HMF yield with a 98.5% fructose conversion was obtained at 110 ℃ for 120 min in DMSO with MASZN-3(10 mg) as catalyst. The catalyst MASZN-3 was recyled in four consecutive cycles with scarcely any loss of activity. Finally, kinetics studies reveal that the MASZN-3 promoted fructose-to-HMF transformation may follow pseudo- first-order kinetics with observed activation energy of 54.5 k J/mol under the investigated conditions. The excellent catalytic properties together with its easy synthesis, low cost, and nontoxic nature make this MASZN a promising catalyst for the development of new and efficient processes for biomass-based chemicals.(4) Investigating the catalytic activity of several MAZN and MASZN materials in the glucose degradation reaction. The effects of catalyst type, catalyst amount, reaction temperature and time on HMF yield were studied. The results showed that MASZN-3(20 mg) catalyst has been demonstrated to be the most active, exhibiting higher HMF yield(37.8 %) at 130 ℃ and after 4 h of reaction time in [AMIM]Cl. Otherwise, the material shows a good catalytic activity for the dehydration of biomass-derived surcose, lnulin and cellobiose to 5-hydroxymethylfurfural(HMF), which enables maximum yields of 43.7%, 54.8% and 25.7%, respectively, in [AMIM]Cl or [BMIM]Cl solvent system. At last, the degradation mechanism for glucose conversion to 5-HMF catalyzed by MASZN was proposed in the thesis, and MASZN expressed a more efficient catalytic activity in conversion of glucose into HMF. The research highlights a good prospect for catalytic application of MASZN solid acid catalysts for biomass carbohydrate degradation.