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

Acrylic acid(AA)is a kind of an important raw material and polymer monomer,which is more often used to produce acrylic esters.Beyond that,Acrylic acid and acrylate are also used in a wide range of polymerization products,including construction,textile,packaging products,sanitary materials and other fields.It is mostly produced by the current production methods including acrylonitrile hydrolysis and propylene oxide.However,there are some troublesome problems in this production prosess,such as the increasing cost,corrosion resistant ability of the equipment and environment pollution.The aldol condensation reaction of acetic acid and formaldehyde to make acrylic acid is a potential route,which has raised scientists much concern because of the advantages of simple process,low cost raw material,fully utilize the resources,green environment and so on.VPO has been highly concerned as a heterogeneous catalyst,and widely used in the vapor phase condensation reaction of acetic acid and formaldehyde to produce acrylic acid.But at present,the research on the structural properties,reaction properties and reaction mechanism of VPO catalyst in the condensation reaction of acetic acid and formaldehyde is not deep enough,which remains to be furthered research.In this paper,in order to improve the selectivity of catalyst on the target product,we added the third component on the basis of VPO catalysts and produced system of MVPO catalysts.We selected the high selectivity of the catalyst and adjusted the preparation methods and evaluation conditions of the catalysts for the best property.Furthermore,we discussed the relation between the catalytic properties and the catalysts structure with the application of characterization methods.So we can provide useful information and theoretical basis for the research of the catalyst in the aldol condensation reaction of acetic acid with formaldehyde for acrylic acid.The details of this thesis are as follows:(1)We added the third component(Mo?W?Cr?La?Ce)on the basis of VPO catalysts.The influence of different additives and the content of additives on the catalyst performance were investigated.The catalyst of LaVPO is the optimum one.(2)We studied the influence of the raw material of catalysts,synthesis temperature,calcination temperature,calcination atmosphere and other conditions on the catalyst performance.It turns out that take the vanadium pentoxide as vanadium source,orthophosphoric acid as the phosphorus source,the synthesis temperature of 110? the calcination temperature of 550?,the calcination atmosphere of muffle furnace,the catalyst have the highest selectivity.(3)After confirming the LaVPO catalyst.We optimize the conditions:the reaction temperature,the oxygen flow,the nitrogen flow,the feedstock flow during the reaction.It turns out that the most optimal catalyst and evaluation conditions are as follows:the reaction temperature of 350?,the space velocity quality of 2400h-1,the oxygen flow of 3 ml/min,the nitrogen flow of 20 ml/min,the feedstock flow of 1 ml/h.(4)We investigated the structure and surface properties of the catalysts by XRD,IR,SEM,NH3-TPD,Py-IR,BET and other characteristic techniques.We found that the main active constituent of the catalyst is V5+ crystal phase with V4+ crystal phase doping.The catalyst surface has weak acid center,mediate strong acid center and strong acid center.We speculate that the dominant constituent is B acid during the catalytic reaction process.