Study On The Conversion Of Biomass Sugars Over WZr Solid Acid Catalysts

Cellulose is one of the most abundant biomass resources in nature and can convert to fuels and chemicals, which is of great importance for establishing the sustainable chemical proeesses. Solid superacids WO₃/ZrO₂ due to its excellent acid catalytic performance has been widely applied in a range of reaction. Based on the above background, this thesis focuses on the studies of cellulose model molecules cellobiose hydrolysis and cellulose hydrolysis-hydrogenolysis over modified WO₃/ZrO₂ catalyst.First, we conformed the hydrolysis active-sites of WO₃/ZrO₂ catalyst. A series of 0.1-WO₃-ZrO₂?T? catalysts with different calcination temperature were prepared by the coprecipitation method. Results show that under the same introduction amount of WO₃, catalyst performance is affected by the calcination temperature and get the best at 700⁸00?. At this point, surface tungsten density of the catalyst was at a “intermediate” level that maximize the population of amorphous surface polytungstate species. In order to improving the catalytic performance of WO₃/ZrO₂ solid acid, the supported 10%, 20%, 30% WO₃/Zr-SBA-15 solid acid catalyst with high specific surface area and uniform mesoporous were prepared by post-synthesized metnod. The catalyst performance maximized in medium load 20%. From the above, catalyst pore structure modification is of importance for the hydrolysis reaction, but surface state of W atoms are the decisive factors in catalytic properties.Compared with the traditional impregnation method, one-pot synthesis method can make the active component more dispersed. In the second part of this thesis, one-pot hydrothermal method was used to synthesize the W30Zry/SBA-15?y=0, 3, 5, 10, 15? catalysts, by adding Zr components, Which can control the surface state of W atoms While maintaining the material structures for the interaction between W and Zr. BET, small angle XRD, TEM results showed that the synthesized WZr/SBA-15 catalysts possess high specific surface area?> 400 m2/g? and regular pore structure? 7 nm?. In addition, the addition right amount of Zr can effectively improve the structure of the catalyst. XRD, UV-vis and Ranman results showed that Zr component can stabilize the amorphous WOx species and prevent the growth of WO₃ crystallites. Concerning the acid site nature, a progressive increase of the amount of Br?nsted sites with the polytungstate species was observed.Incorporation of small amounts of ZrO₂ into WZr/SBA-15 catalysts, can control the surface WOx species, improve acidity and structure of the catalysts, and significantly increased the cellobiose conversion. The hydrolysis activity achieved the highest value on W30Zr5/SBA-15 catalyst when the WO₃ concentration is 30 wt%, the Zr/W mole ratio is 0.3 0.6. When it undergos reaction at 160? for 90 min, the catalyst W30Zr5/SBA-15 exhibits high cellobiose conversion?75%? and sugars yield?53%?. Then WZr/SBA-15 solid acids were mixed with Ru/C catalysts for the hydrolysishydrogenolysis of cellulose. The results show that the solid acid has little effect on the cellulose conversion, but catalyze the cleavage of the C-C bonds to generate C2^C4 alcohols, the selectivity of ethylene glycol is 30% within at 205 ?, and a cellulose conversion of 100% and a ethylene glycol yield of 45.6% were obtained at 245 ?.