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Preparation And Performance Study Of Novel Supported Phosphotungstic Acid Catalyst For Alkenylation

Posted on:2018-03-05Degree:MasterType:Thesis
Country:ChinaCandidate:X H WangFull Text:PDF
GTID:2321330536461792Subject:Industrial Catalysis
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Alkenylaromatics are important organic intermediates.Direct alkenylation of aromatics and alkyes over novel metal catalysts and acid catalysts has attracted extensive attentions.However there are still some problems.Expensive ligand is needed to prepare novel metal catalyst and the catalyst is of low reaction efficiency and poor recyclability.On the other hand,although the liquid acids have been exploited in the alkenylaton,environment pollution,corrosion of equipments and complexity in the isolation of products are still bottle-neck problems for the application of liquid acid catalysts.So it is important to prepare novel solid acid catalysts.Phosphotungstic acid which is of the highest acidic strength and best thermal stability in all kinds of heteropoly acids has unique redox and acidic properties and has expressed outstanding catalytic performance in many kinds of organic reactions.The application of phosphotungstic acid is limited by low surface area and poor recyclability so the immigration of phosphotungstic acid on diverse careers can significantly improve surface area and catalytic performance and can also solve the recycling problem.In this paper,the supported phosphotungstic acid catalysts prepared by a facile wet impregnation method were employed for Friedel–Crafts alkenylation of p-xylene with phenylacetylene to synthesize their corresponding ?-arylstyrenes.Various characterization techniques such as N2 adsorption-desorption,X-ray diffraction(XRD),FT-IR,NH3 temperature-programmed desorption(NH3-TPD)were employed to reveal the relationship between catalyst nature and catalytic performance.The main conclusions are summaried as follows:1.The supported PTA catalysts on AC carrier with diverse PTA loadings have been prepared.The effect of phosphotungstic acid(PTA)loading and reaction parameters on the alkenylation is studied.The 30 wt.% PTA/AC sample can be chosen as a promising solid acid catalyst for Friedel–Crafts alkenylation.The desired product 1-phenyl-1-(p-xylyl)ethane is selectively(90% selectivity)obtained with an almost full conversion(99%)under the optimum reaction conditions,i.e.dosage of catalyst 3.33 wt.%,reaction temperature 150 oC,molar ration of p-xylene to phenylacetylene 12,reaction time 4 h.and the developed catalyst can be reused 4 times without visible loss in catalytic performance.2.The supported PTA catalysts with same PTA loadings on AC,CMK-3 and mesoporous carbon MC prepared by soft template method have been prepared.PTA/MC catalyst has the best catalytic performance under the same reaction condition.The effect of PTA loading of PTA/MC has also been studied.The 35 wt.% PTA/MC sample is the chosen one with best catalytic activities and excellent cyclic utilization.3.Mesoporous silica nanoparticles(MSNs)with sphere diameter less than 100 nm have been prepared employing low-cost and non-poison urea as the mineralizing agent.And the particle size and pore structure can be adjusted by changing the urea concentration.Compared with PTA/MCM-41,PTA/MSN prepared via a wet impregnation method assisted by vacuum with heating shows better catalytic activities and stability.
Keywords/Search Tags:alkenylation reaction, solid acid, phosphotungstic acid, carrier, structure-activity relationship
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