The Study Of VPO Catalysts In The Condensation Reaction Of Formaldehyde With Acetic Acid For Producing Acrylic Acid

Acrylic acid(AA)are important organic synthetic raw materials and resin monomer,which is often used to produce methyl acrylate,ethyl acrylate and so on.Acrylic acid and acrylate are widely used in synthetic resin,fiber,building materials and many other fields.The current main production methods of acrylic acid are acrylonitrile hydrolysis and propylene oxide.However,the two methods are faced with many problems respectively,such as the increasing cost of production,equipment corrosion and environmental impact.So a new production technology of acrylic acid is more improtant.Comparatively speaking,the process of aldol condensation reaction of acetic acid with formaldehyde for producing acrylic acid has the adwantages of rich and cheap raw materials,low environmental impact,thus it has obtained more and more concern.In general,aldol condensation reactions of acetic acid with formaldehyde can be catalyzed by many catalyst systems,such as composite metal oxide acid and/or base catalysts and so on.As the structure properties,the catalytic performance,catalysis mechanism of the catalysts and some other problems are still unknown,we need to study hard.In this work,we have synthesis of a series of VPO catalysts.We studied the preparation methods and evaluation conditions of the catalysts for the best property.We characterized the structure properties of the catalysts and invested the catalytic performance of the aldol condensation reaction of acetic acid with formaldehyde for producing acrylic acid on these catalysts.We also hope to establish the relationship between the structure properties and its catalytic activity of the catalyst.So we can provide experimental basis and theoretical foundation for the research of the catalyst in the aldol condensation reaction of acetic acid with formaldehyde.The details of this thesis are as follows:(1)We synthesized the VPO catalysts in the aqueous solution system or in the organic solvent system.We studied the calcination temperature,calcination atmosphere,and phosphorus vanadium molar ratio of the catalysts.Then the catalytic performances of the catalysts were investigated in the aldol condensation reaction of acetic acid with formaldehyde for producing acrylic acid.Meanwhile,we invested the oxygen flow of the evaluation system.Comparing with other catalysts,the catalysts prepared in the organic solvent system shows remarkably higher activity.It turns out that the most optimal catalyst and evaluation conditions are as follows:the phosphorus vanadium molar ratio of 1.5,the calcination temperature of 550?,the calcination atmosphere of muffle furnace,the oxygen flow of 3 mL/min,the reaction temperature of 350?.(2)We have synthesized of a series of MVPO catalysts(M = Li,Na,K,Rb,Cs,Mg,Ca)in the organic solvent system.The influence of different additives and the content of additives on the catalysts performance were investigated.And the life of the catalysts was researched.According to the experimental result,we could get the following conclusion:the catalyst of KVP02c-0.08 is the optimum one.The catalyst is still active 60 hours later.(3)We invested the structure and surface properties of the catalysts by XRD,IR,SEM,NH3-TPD,Py-IR and other characteristic techniques.We found that the active constituent of the catalyst are V5+/V4+ mixed crystal phase and V5+ crystal phase should be the main composition.The catalyst surface has weak acid center and mediate strong acid center.