Based On Phosphotungstic Acid Organic-inorganic Functional Material Preparation And Catalytic Carbohydrate Conversion Research

With the rapid development of the world economy,human demand for energy is increasing.The increase in fossil energy consumption and the decline in environmental quality have caused widespread concern.To this end,the search for renewable resources to replace fossil energy has become an important issue that needs to be solved urgently.Among renewable resources,biomass exhibits unique advantages that it is the only sustainable organic carbon resource with broad application prospects in the chemical and fuel industry.In this thesis,phosphotungstic acid was used as the basic raw material for the preparation of solid catalysts.A series of organo-inorganic functional materials of phosphotungstic acid were designed,prepared,and used to catalyze the production of alkyl levulinate from biomass derivatives and the carbon chain elongation reaction of biomass platform small molecules.The specific studies are listed as follows:1.The solid heteropoly acid catalyst 3-chloropyridine phosphotungstic acid?3-ClPYPW?was prepared by solvothermal method and characterized systematically.The catalyst was used to catalyze the dimerization of 5-methyl sterol?MFA?,and the reaction time,temperature,amount of catalyst,different solvents,catalyst reusability and kinetics were studied.The results showed that the conversion of MFA and the yield of the product were 69.1%and 51.6%,respectively,using 5mg catalyst and CH₂Cl₂ as solvent at 70°C for 11 h.Catalysts recyclability studies showed no significant loss of catalytic activity after recycles.Kinetic studies showed that the activation energy?Ea?for the reaction is 41.1 kJ/mol.2.3-BrPYPW catalyst was prepared by solvothermal method using phosphotungstic acid?HPW?and 3-bromopyridine?3-BrPY?as raw materials,and the catalyst was characterized.The3-BrPYPW catalyst was used for catalyzing the tetramerization of 5-hydroxymethylfurfural?HMF?and 2-methylfuran?2-MF?,and the reaction time,temperature,amount of catalyst,different solvents,catalyst reusability and reaction pathway were investigated.The 2-MF conversion and the yield of the target product were 78.0%and 37.1%,respectively,using 20 mg catalyst,CH₂Cl₂as solvent at 100°C for 8 h.In addition,based on the HMR analys is,the reaction pathway was proposed.3.A series of phenylpyridine phosphotungstic acid?x-PhPYPW,x=2,3,4?catalysts with different phenyl groups in different positions of pyridine were prepared.The structure and properties of the catalysts were analyzed by characterization techniques.The best catalyst,3-PhPYPW,was screened to catalyze the conversion of fructose to methyl levulinate?ML?.The fructose conversion and ML yield were 83.2%and 71.2%,respectively,under the reaction conditions of 140°C,8 h,90 mg catalyst,and the fructose concentration of 0.2 mol/L,and the catalyst had good reusability.In addition,the effects of different linear alcohols?methanol,ethanol,n-propanol and n-butanol?on the preparation of alkyl levulinate in fructose were investigated.4.A series of catalysts with different substituents of pyridylphosphonic acid?3-nPYPW,n=-OCH3,-COOCH3 and-F?were prepared and characterized systematically.The best catalyst3-FPYW was selected and used to catalyze the preparation of fructose into ML.Fructose conversion and ML yield were 97.8%and 82.5%,respectively,under 3-FPYPW?0.1 mmol H⁺?,fructose concentration?0.2 mol/L?at 120°C for 10 h.Catalyst reusability studies show that3-FPYW catalysts have good reusability.In addition,the possible reaction path was studied.5.A bifunctional heteropolyacid catalyst was prepared by impregnation method,and used to catalyze the preparation of ML from carbohydrates.Screening out the best catalyst 5.0%Sn/3-FPYH₂PW and the Sn load,catalyst amount,reaction time,temperature,and substrate were studied.The results showed that the yield of ML was 26.0%at a temperature of 160°C,10 h,Sn loading of 5.0 wt%,and 25 mg catalyst.At the same time,the reaction substrate has been expanded stdudy accordingly.