A Research Into Catalysis Of Transition Metal Phosphotungstates For Alcohol Oxidations

Polyoxometallates have great utilities in catalysis because of their acidity and redoxidation quality. Compared with the traditional catalysts,they are characterized by internal strueture,a pseudo-liquid phase in solid state,and good solubility in polar solution and therefore found to be high catalytic activity and selectivity in the organic catalytic reaction。With low corrosiveness to equiments and mild recation condition,they have received the widespread attention in recent years。In this work, phosphotungstates of nickel,cobalt and zinc(noted NiPW,CoPW and ZnPW respectively) were prepared, structurally characterized by XRD, DTA-TG,UV and IR and used as catalysts for the selective oxidation of liquid BzOH into BzH with hydrogen peroxide as an oxidant under solvent-free condition and aminent pressure。Calcination temperature, the amount of catalyst, the amount of H₂O₂ ,reation temperature and reation time—five factors effective on catalystic activity were carefully investgated to obtain the optimum conditions before a research into reuses and catalysis of catalysts in oxidation of other alcohols。The results are as follows:The catalystic activity of NiPW reaches its maximum when 5ml BzOH was oxided by 10ml H₂O₂ at 90℃for 3.5h in the presense of 0.5g NiPW calcined at 300℃。Conversion of BzOH and yield of BzH are 90.9% and 79.4%,respectively. As to CoPW,its best result that the conversion of BzOH and the yield of BzH are 82.8% and 73.5%。respectively,was come to under the same condition as that of NiPW except the catalystic amount of 0.2g。However, ZnPW showed the top activity of catalysis in conditions of NiPW other than the catalystic amount of 0.4g and reaction time of 2.5h。Recycle of catalysts was accessible。In addition,it can be seen from oxidations of other alcohols that those with active groups were much more active than BzOH, but corresponding aldehydes were much less selective and that primary and secondary alcohols were amost inactive。Keggin structures of these catalysts were identified by XRD,higher thermal stability of by DTA-TG and complete Keggin structures having been reused for 4 times kept by IR and UV。The synsized catalysts were characterized by simple preparation , cheap availableness, high efficience and selecivity, being easily reused and friendly to environment,which is in response to green chemistry。Furthermore,reations were easily operated at short time with high yield,the fully used staring materials and without high pressure and any solvents, which were in agreement with atomic economy。Therefore,this work provides a efficient and practical way to prepare BzH,and broad prospects for industry application。...