A Study On Carbon Deposition Over Magnesia Supported Copper Salts Of Molybdovanadophosphoric Acid

In this paper, the advances of heteropoly compounds and their supportcatalysts are reviewed and the different supports are also introduced in detail.The factors affecting catalytic properties of supported heteropoly compoundsand the interactionAs the HPC catalysts are only stable at low temperature, it is consided tobe very important to study the technology that how to release the coke of thecatalysts at low temperature. The carbon deposition over magnesia-supportedheteropoly compound (HPC) Cu2PMo11VO40(CPMV) during the hexanoloxidation reaction has been studied. The coke predominantly deposited on thecatalyst surface in the form of CHx, and it has not been found to causedeactivation of the catalyst. The XRD, IR, XPS characterizations reveal thatthe Keggin structure of the CPMV was unaffected by carbon deposition. Wealso take the reaction over CPMV23.1/MgO at 280℃ for 50h. The catalyseability did not fall down, and the selectivity of the aldehyde keep over 96.0%.Moreover, it is shown that the supported CPMVs over the MgO surfacecan be beneficial to eliminate the coke. The temperature programmedoxidation (TPO) study showed that coke was formed over the catalyst on twodifferent sites. One type deposited on the CPMVs which can be burn off at lowtemperature, but the other type deposited on the MgO could only be removedat higher temperature. The coke content reached to constant with the reactiontime increasing.In the process of selective oxidized of alcohols, the aldehydes are alwayseasily further oxidized to acid. So it is our aim that how to get a quicker andmore selective way to complete this reaction. From 70th, heteropolycompounds (HPC) have been used in the industry product as a kind of newefficient catalysts. This type of catalysts shows high activity and selectivity forseveral reactions, and with low corrosion and low reaction conditions as well.Moreover, it is easy to change the HPC catalysts into the lacunary structurecatalysts. We can add the transitional metal atoms in the lacunary place. Thetransitional metal atoms connected the aniline with covalent bond. Then this type ofcatalysts can be modified with aniline, quinoline, Py and etc. This is a newtype of HPC catalysts, and they are suitable with the organic/aqueous biphasiccatalysis system.During the past twenty years, the oxidation of liquid alcohols intoaldehydes or ketones has been studied in homogeneous catalysis, liquid-solidheterogeneous catalysis and organic/aqueous biphasic catalysis. After thestudying of these different reactions, we come to the conclusion thatorganic-aqueous biphasic catalysis and multiphase reactions have a promisingprogress. Especially the reactions which operated under mild condition anduse O2 or air as oxidants and the catalysts can be recycled. It will be beneficialto the environment protection. Meanwhile, the process can also be applied tothe conversion of other alcohol-like chemicals. It has active meaning to solvethe pollution problems.It is reported here the synthesis of the HPC catalysts with lacunarystructures, and we added the transitional metal atoms in the lacunary place.Then we modified the catalysts with aniline. The oxidation of alcohols intoaldehydes was carried out over this type of HPC. The catalysts which before orafter the reactions were characterized by the means of IR, XRD, UV-VIS,DT-TGA etc. It is shown that the addition of aniline have not changed theKeggin structure. The transitional metal atoms connected the aniline withcovalent bond. The addition of aniline can efficiently rise the selectivity ofhexanal. After the reaction, the catalysts kept their Keggin structure and theycould be easily separated from the system only by the way of filtration.