Preparation Of Immobilized N,N-bidentate Schiff Base-type Oxovanadium(IV) Complex And Research On Its Catalytic Oxidation Performance

Immobilized oxovanadium（IV） complex catalyst exhibit excellent selectivity. Undermild conditions, it can efficiently catalyze the oxidation of many organic compounds,such as hydrocarbon into oxidation compounds and alcohols into aldehydes or ketone. Inthis paper, a new way of preparing Schiff base-type oxovanadium（IV） complex catalystwas designed. Firstly, N,N-bidentate schiff base ligands were prepared by using crosslinked polystyrene （CMCPS） microspheres as a carrier. After coordinating with oxygenand sulfuric acid vanadium （IV）, we obtained immobilized N,N-bidentate Schiff basetype oxygen vanadium （IV） complex and thoroughly investigate its catalytic activity onthe molecular oxygen oxidation catalyst ethylbenzene, benzyl alcohol and cyclohexanol.The results of this study have important scientific significance in the field of greencatalytic oxidation technology and organic synthesis.The nucleophilic substitution reaction between the chloromethyl groups of theswelled CMCPS microspheres and p-hydroxybenzaldehyde was first allowed to preparepolymer microspheres by bonding benzaldehyde （BA） BA-CPS. We also explored themost suitable modification conditions. And then the Schiff base reaction betweenBACPS microspheres and3–aminopyridine was conducted, resulting in BAAP-CPSmicrospheres. After coordinating with oxygen and sulfuric acid vanadium （IV）, weobtained oxovanadium（IV） complex heterogeneous catalysts bonding with N,N-bidentate Schiff base ligands CPS-[VO（BAAP）₂]. The chemical structure of themicrospheres CPS-[VO（BAAP）₂] were characterized by UV, FTIR and AAS. We foundthat CMCPS microspheres modification must be under the conditions of the constanttemperature of90℃, N2protection and acid binding agent of sodium carbonate, and the chloride methyl conversion rate of the chloride ball surface is80%.Then microspheres CPS-[VO（BAAP）₂] were used to catalyze the molecular oxygenoxidation process of ethyl benzene. And the effect of main factors on the catalyticoxidation was investigated and the mechanism of catalytic oxidation was explored. Wefound that it exhibited high catalytic activity and excellent selectivity. Under suitablereaction conditions （temperature110℃, the reaction of oxygen under atmosphericpressure through12h）, ethylbenzene can be efficiently （45%conversion） converted to asingle product acetophenone. The course of the reaction may follow radical oxidationreaction and the alkyl side ethylbenzene hydroperoxide can be crucial intermediate.Based on the preparation of microspheres CPS-[VO（BAAP）₂], the reaction betweenBA-CPS microspheres and glycine （GL） was conducted, resulting in N, O-bidentateSchiff base ligands microspheres BAGL-CPS. After coordinating with oxygen andsulfuric acid vanadium （IV）, we obtained oxovanadium（IV） complex heterogeneouscatalysts bonding with N,O-bidentate Schiff base ligands CPS-[VO（BAGL）₂]. Weinvestigated the catalytic activity of the two catalysts when they were used for theoxidation process of benzyl alcohol to benzaldehyde. In the reaction of the oxidation ofbenzyl alcohol to benzaldehyde, the results showed that the catalytic properties ofheterogeneous Schiff based on complexes of vanadium oxide was closely related to itschemical structure. The catalytic activity and stability of immobilized N, N-typecomplexes CPS-[VO（BAAP）₂] were significantly higher than N, O-type complexesCPS-[VO（BAGL）₂]. Under suitable reaction conditions, benzyl alcohol can beefficiently converted to a single product benzaldehyde with the conversion of85%byusing CPS-[VO（BAAP）₂] as catalyst.Finally, the coordination reaction between BAAP-CPS microspheres and cobaltions and molybdenum dioxide were conducted respectively, and two other bonded N,N-bidentate Schiff base metal complex catalyst microspheres CoBAAP-CPS andCPS-[MoO2（BAAP）₂] were prepared. We used the three kinds of N, N-type catalystmicrospheres CPS-[VO（BAAP）₂], microspheres CoBAAP-CPS and microspheresCPS-[MoO2（BAAP）₂] to catalyze the molecular oxygen oxidation process ofcyclohexanol to cyclohexanone, finding that the catalytic activity of CPS-[VO（BAAP）₂]was higher than the other two microspheres. The catalytic activity and mechanism of CPS-[VO（BAAP）₂] were investigated. Under mild conditions （oxygen under pressure,the temperature90℃）, the conversion of cyclohexanol to single product cyclohexanonecan be reached to90%. The polarity of the solvent had a very significant impact on theactivity of the catalyst. The weaker of the polarity of the solvent, the higher the activityof the catalys and the yield of cyclohexanone. Catalyst CPS-[VO（BAAP）₂] haveexcellent cycle performance.