Preparation Of Platinum - Tungsten - Zirconium Multifunctional Catalyst And Study On Hydrogenolysis Of Glycerol

In recent years, the production of renewable chemicals has attracted much more attention, as a sustainable natural resources, biomass glycerol was the most simple polyols. Glycerol is a by-product of biodiesel production, and form the backbone of the triglycerides in the biomass, converting the excess glycerol into the highest value of 1,3-propanediol become a hot spot. In order to generate selectively to1,3-propanediol, adding a suitable catalyst is necessary. Due to the functional group of glycerin is hydroxyl, effectively potential catalyst must be strongly interact with hydroxyl. Metal oxide is one of the most effective catalytic material, especially tungsten trioxide. Most studies have shown that the combination of precious metals and tungsten trioxide can be selective conversion of glycerol to 1,3-propanediol. From the tungsten oxide based catalyst, the most widely known and application is WO₃/Zr O₂ solid acid catalysts. Consequently, precious metals and this kind of composite solid acid is a kind of ideal multifunctional catalyst.Pt/WO₃-Zr O₂ solid superacids multifunctional catalyst not only has more strength of acid than the average of solid acid catalyst, but also thanks to the synergy of metal and acid, hydrogenation activity is higher than common type load hydrogenation catalyst. On one hand, it makes up the defect of the acid strength aspect, which makes catalysis tend to be carried out under lower temperature.On the other hand, its advantages of recycle, non-corrosive to the reaction device and environment friendly advantages are widely used in isomerization, alkylation, acetoxylation, hydrogenation deoxidization reaction. Glycerin hydrogenolysis reaction was one of the special excellent performance compared with other catalysts combined metal and support as Pt/WO₃-Zr O₂.In order to study the platinum tungsten zirconium catalytic systems in the role of glycerol hydrogenolysis reaction, based on the different preparation methods of different types of platinum tungsten zirconium catalyst was prepared. In the third chapter of the thesis, three kinds of platinum tungsten zirconium catalysts prepared by three kinds of preparation methods and respectively the catalytic performance of hydrogenolysis of glycerol to 1,3-propanediol were tested through comparison and conditions optimization. Preparation of continuous impregnation method to Pt/WO₃-Zr O₂-C catalysts, precipitation and impregnation method to Pt/WO₃-Zr O₂ catalysts and coprecipitation preparation method to Pt/WZr Ox catalyst respectively.Pt/WZr Ox catalyst which prepared by coprecipitation method increased the formation of super acid active sites on W-O-Zr bonds, and Zr O₂ is stable in the WO₃-Zr O₂ solid acid which composite of more acidic content. Through XRD, NH3-TPD proved tetragonal phase Zr O₂ and strongly acidic catalyst, BET shows that this method is also beneficial to the catalyst, large specific surface and the multistage aperture were formed. TPR proved that the hydrogen on the surface of the overflow of catalytic hydrogenolysis of glycerol played a crucial role, and W-O-Zr activit sites makes the overflow with hydrogen to form H+, H- ion is the key to the activation of C-O bonds.Only by optimizing the space velocity, temperature conditions, the yield of1,3-propanediol could reach 35.1%. And the reaction mechanism was studied and discussed the different types of WO₃ hydrogen formation in the glycerol solution process.In the fourth chapter of this thesis, a kind of superfine nano zirconium dioxide as a carrier of high purity was used to prepare Pt/WO₃-50 nm Zr O₂ series catalysts by the simple method of continuous dipping. This series of catalysts can efficiently hydrogenolysis of glycerol selectively generation 1,3-propanediol, significantly curb the generation of the 1,2-propylene glycol. Through WO₃ load and metal Pt load modulation, determines the optimum catalyst group is 2.0Pt/0.40WO₃-50 nm Zr O₂. At high space velocity, low temperature 140 ℃, the continuous hydrogenolysis of glycerol to 1,3-propanediolcan reached more than 40% of the yield of1,3-propanediol. Catalyst life reached more than 80 h, the reason of catalyst deactivation due to Pt particles back into large up slightly and W5+ decreased in activity species of WO₃. Then also prepared the different types of platinum tungsten zirconium catalysts to study the difference of loading Pt for the first time on the WO₃ and loading on the 50 nm Zr O₂.Through the acknowledge of different effect to the reaction, the relationship between a further improved structure-activity relationship between catalysts and reactants was described.