Solid Catalytic Hydrolysis Of Glucose To Produce5-hydroxymethylfurfural

As the global petroleum oil and natural gas supplies are gradually used up, the traditional chemical industry is facing serious challenge of sustainable development. Using renewable biomass resources as the organic chemical raw materials, researching green chemical technology, and preparing biomass-material based platform chemicals have become the important topics of the modern chemical industry.5-hydroxymethylfurfural (5-HMF) is a representative of biomass monomer. It contains active functional groups-aldehyde group and hydroxymethyl, which make it attractive to be used as an intermediate for many reactions, and as raw materials for synthesis of large ring compounds, or monomer for synthesis of polymer materials. Carbohydrates, especially the conversion of glucose to5-HMF have become a hot research topic. As the studies showed, the conversion of glucose to5-HMF process went through at least two steps:isomerization between glucose and fructose and dehydration of fructose. Solid catalyst has the advantage of not easily deactivated, high selectivity, and friendly to environment, so the application of solid catalyst in5-HMF preparasion is very promising. ZrO2not only can be used as a catalyst, but also as a catalyst carrier, therefore its application has attracted much attention. ZrO2has acidity, aklinity and oxidation-reduction property, therefore, ZrO2was selected as the base catalyst. SO42-/MxOy solid super acid catalyst has high activity, good thermal stability, excellent selectivity, and is simply and environmentally friendly in preparation. Therefore, SO42-/TiO2-SiO2was selected as the acid catalyst.5-HMF in aqueous phase is easily combined with water and reduces its yield. Therefore, DMSO was selected to adjust aqueous phase to both enhance the5-HMF yield and selectivity of this reaction, and shorten reaction time.This paper mainly studied the preparation of5-HMF from glucose by environmentally friendly solid catalyst in laboratory conditions, and successfully prepared two kinds of solid catalysts with different functions, and finally, the two kinds of solid catalysts were fixed into tubular reactor, the concentraton of the 5-HMF produced was analyzed by ultraviolet spectrophotometry. Below are the main results obtained:1. Using glucose as the substrate of the reaction, the effects of substrate concentration, volume ratio of water and organic phase, reaction temperature, reaction time on the5-HMF yield was investigated, and the optimal production conditions obtained were:substrate concentration of50%, volume ratio of water and organic phase of1:2, reaction temperature of140℃, and reaction time of12h, and under these conditions, the5-HMF yield reached the maximum of57.85%.2. The solid base ZrO2and solid acid SO42-/TiO2-SiO2catalysts were prepared and the best conditions were determined through the single factor experiments. The best calcination temperature for ZrO2was450℃, addition amount was20%when used ZrO2alone; and the best calcination temperature of SO42-/TiO2-SiO2was450℃, n(Ti):n(Si) was4:1, addition amount was20%when used SO42-/TiO2-SiO2alone.3. The effects of five single factors on the5-HMF yield were also investigated. When using solid acid and solid base together, results showed that:when m(Zr02):m(SO42-/TiO2-SiO2) was4:3, the total amount of solid acid and solid base added was20%, calcination temperature of ZrO2was450℃, calcination temperature of SO42-/TiO2-SiO2was450℃, n(Ti):n(Si) was4:1, the5-HMF yield reached the maximum of86.58%.4. With the Plackett-Burman (PB) experiment design using the JMP7.0software, the selected three significant factors among the9single factors affecting the5-HMF yield studied are:reaction temperature, calcination temperature of solid base, and calcination temperature of solid acid.5. The Design-Expert8.0software was used to develop the regression model for thesignificant factors affecting the5-HMF production and the regression equation obtained is shown below and with good fitting: Y=86.27+6.22*A-1.42*B+3.57*C-0.84*A*B+1.67*A*C-1.59*B*C-20.89*A2-7.98*B2-8.48*C2 This regression equation can be used in repalce of the actual experimental data analyze the experimental results.6. Based on the XRD analysis, CO2-TPD-MS analysis, and SEM figure of ZrO2, there were more monoclinic phase ZrO2with higher calcination temperature, ZrO2prepared under450℃had mild basicity, and higher calcination temperature caused catalyst binding to each other and affected its catalytic activity.7. Results of FT-IR analysis, Hammett indicator analysis, XRD analysis, TG-DTA analysis and SEM analysis of SO42-/TiO2-SiO2showed that:SO42-/TiO2-SiO2had super acidity after dipping in H2SO4, TiO2-SiO2had rough surface after dipping in H2SO4, and dipping in H2SO4also created many cavities and loosen its structure, therefore improved the specific surface area and catalytic activity. SO42-/TiO2-SiO2prepared under450℃had mild acidity which is more advantageous to the conversion of glucose to5-HMF.8. Researches on the reuse times of using both solid base and solid acid alone and together showed that the catalysts were deactivated after6times of use. The deactivation of the ZrO2was caused by coking of the surface, deactivation of SO42-/TiO2-SiO2was caused by losing SO42-and coking of the surface. Catalysts can be regenerated.9. Solid catalysts were also fixed into a continuous tubular reactor after granulation to study on the effects of reaction temperature, reaction pressure, type of the two kinds of catalysts used on the5-HMF yield. The optimized process conditions obtained throught the orthogonal experiment design were:reaction temperature of180℃, reaction pressure of6Mpa, and with the mixing type of catalyst used.In smmary, this paper successfully prepared the5-HMF in the laboratory condition using solid acid and solid base mixed catalysts. The5-HMF from starch hydrolysates was also prepared in a continuous tubular reactor. This paper provided new references for efficiently transforming biomass to platform chemicals.