Research On Synthesis Of Benzaldehyde By Dawson Type Heteropoly Compounds Liquid-phase Catalyzed Oxidation Of Toluene

Benzaldehyde is an important aromatic aldehyde in industry.Traditionally, benzaldehyde is produced by side-chain chlorination oftoluene, this process involving Cl2causes environmental pollutions andequipment corruptions. Along with the global attention to environmentprotection, HPC have been investigated extensively in catalytic field andmaterial chemistry because of its high catalytic activity, mild reactioncondition and anti-corrosion equipment as a green catalyst. Therefor, it hasimportant research and industrial significance to develop their appliedresearch in organic synthesis and catalytic field.This dissertation taking toluene as raw materials, research theDawson-type heteropoly acid neodymium salt catalytic oxidation of tolueneto benzaldehyde. Speculate the reaction mechanism. The main progress andresearch results have been obtained as follows:1, Catalytic oxidation of toluene to benzaldehyde over Dawson-typeheteropoly Acid neodymium saltUsing H2O2as oxidant and Dawson-type heteropoly acid neodymiumsalt as catalyst.The catalytic activity was determined by the oxidation oftoluene to benzaldehyde. The catalyst was characterized by infraredspectroscopy, X-ray diffraction. Catalyst exhibits high activity owing tostrong synergistic effect of Neodymium and vanadium. Experimental resultsshowed that with the acetonitrile (10mL) as solvent, the amount of tolueneis23.5mmol, the amount of catalyst is0.1mmol, the amount of H2O2(50%in volume) solution is0.4mol, reacting at90℃for7h. The conversion oftoluene and selectivity of benzaldehyde were up to90.1%,51.0%,respectively. The conversion of H2O2and effective utilization ratio of H2O2were89.0%and43.1%, respectively. A possible reaction mechanism isproposed.2, Oxidation of toluene to benzaldehyde with heteropoly acid neodymiumsalt immobilized on silylated palygorskiteThe surface of acid-activated palygorskite (Pa) was modified bygrafting3-aminopropyl-triethoxysilane (APTES)(the silylated Pa denoted PaA P T E S) for immobilization of Nd₃P₂Mo₁₅V₃O₆₂. The samples werecharacterized by Fourier transform infrared spectroscopy, X-ray diffraction,Brunauer–Emmett–Teller (BET) specific area measurement and thedesolvente rate of samples was determined by UV spectrophotometrymethod. The catalytic activity was determined by the oxidation of toluene tobenzaldehyde. The results show that with the acetonitrile (10mL) as solvent,the amount of toluene is25mmol, the amount of catalyst is0.4g, the amountof H2O2(50%in volume) solution is0.4mol, reacting at90℃for8h. Theconversion of toluene is23.4%and the selectivity of benzaldehyde is70.7%.The catalyst can be easily recycled from the reaction system and thecatalytic activity was not significantly reduced.3,Kinetics of the oxidation of toluene to benzaldehyde was researched overNd₃P₂Mo₁₅V₃O₆₂The effects of the amounts of toluene, Nd₃P₂Mo₁₅V₃O₆₂and hydrogenperoxide dosage carried out the reaction and reaction temperature wereinvestigated. Through data fitting of experiment, the apparent dynamicsequation was obtain in comparison to speculate reaction mechanism thattoluene was oxidized using the heteropoly acid salt complexes as catalyst tobenzaldehyde. The result showed: the reaction is apparent first order intoluene and hydrogen peroxide, respectively, and apparent second order inNd₃P₂Mo₁₅V₃O₆₂. The apparent activation energy of the reaction was17.358kJ mol^-1, the hypothesis would be consistent with the data of theexperiments.