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Synthesis Of Cinnamate Catalyzed By Keggin-Phosphotungstic Acid Supported On Silica Gel

Posted on:2015-02-23Degree:MasterType:Thesis
Country:ChinaCandidate:L CuiFull Text:PDF
GTID:2251330428978044Subject:Chemical Engineering
Abstract/Summary:PDF Full Text Request
In this work, Keggin-phosphotungstic acid (short as12-HPW) supported on silica gel with diffierent load rate is efficiently prepared by the method of excessive solution impregnation, the catalysts are characterized by BET、XRD, TG-DSC, etc. It suggests that when12-HPW is carrired on silica gel, it will still keep Keggin structure, its specific surface area and thermal stability is largely improved with strong B acidity, it will not break down at350℃The isothermal and kinetics for the adsorption of12-HPW on silica gel are investigated. It shows that:Freundlich model is more suitable than Langmuir model; the mean feature concentrations are found out to distinguish chemisorption from physisorption; the whole adsorption is spontaneous, higher temperature contributes to chemisorption, while physisorption is more beneficial at lower temperature; the chemisorption of12-HPW on silica gel obeys quasi-second kinetic equation.Cinnamic acid and methanol are applied as the raw material to sythesis methly cinnamate catalyzed by12-HPW supported on silica gel. The result shows that: when cinnamic acid is0.1mol, ratio of methanol to acid is8:1, weight of catalyst is1.6g, load rate of12-HPW is36.90%, reaction temperature is342.15K, reaction time is2h, the yeild could be up to94.8%.The thermodynamic parameters and equilibrium constant of the synthesis for methly cinnamate catalyzed by12-HPW/silica gel is estimated by the method of Mavrovouniotis and Benson-Joback, the calculated result can well agree with the experimental data, it suggests that the esterification is spontaneous and endothermic.The mechanism and kinetic of the esterification is deeply explored as well. The result suggests that the esterification mechanism obeys simplified Langmuir-Hinshelwood model and its kinetics can fit the quasi-homogeneous double-molecule model very well, the kinetics equation is obtained: r=161.95e50.608/RT CA-3.7835e52.092/RT (3.09-CA)2...
Keywords/Search Tags:Keggin-phosphotungstic Acid/Silica Gel, Adsorption Thermodynamic, Esterification, Reaction Kinetics, Group Contribution Method
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