Synthesis And Catalytic Performance Of Copper Complexes For Selective Oxidation Of Alkylaromatics And Alcohols

This dissertation has set the selective oxidation of alkylaromatics and alcohols as the object of study,focusing on the synthesis,characterization and catalytic performance of multinuclear copper complexes and organo-functionalized SBA-15 encapsulated copper complexes.The main achievements are summarized as followings.By modifying the synthetic methods in literature,four multinuclear copper complexes,that is,dinuclear[Cu₂(H₂tea)₂(C₆H₅COO)₂]·2H₂O(designated as Cul), trinuclear[Cu₃(H₂tea)₂(4-OC₆H₄COO)₂(H₂O)]·4H₂O(designated as Cu₂),tetranuclear [O(?)Cu₄(tea)₄(BOH)₄]·[BF₄]₂(designated as Cu3),polynuclear[Cu₂(H₂tea)₂ {μ-C₆H₄(COO)₂-1,4}]_n·2nH₂O(designated as Cu4),have been synthesized.Their structures have been confirmed by means of FT-IR spectroscopic studies and elemental analyses.These complexes have been employed as catalysts for the selective oxidation of ethylbenzene and other alkylaromatics using tert-BuOOH(TBHP).Several conclusions have been obtained:(â…°) The four complexes showed significant activity for the selective oxidation of alkylaromatics with alkyl substitute groups larger than C2 in the presence of TBHP under mild conditions,affording corresponding ketones as the major products.(â…±) The catalytic performances of the complexes are different from each other,due to the different coordinations and solubility.Among them,the acetophenone with a selectivity higher than 90%and a yield at about 60%can be achieved with Cu3 catalyst using TBHP.(â…²) The alkyl structures in alkylaromatics and the electron effect of their substitute groups were crucial for the catalytic results. Lower conversion was obtained when the alkylaromatics have electron withdrawing substitute groups.Moreover,the selective oxidation of primary and secondary alcohols to corresponding carbonyl compounds with the multinuclear copper complexes Cul-Cu4 as catalysts have been conducted using TBHP and O₂/TEMPO,respectively.Among them,the copper complex Cu3 showed the best performance.On the performances of the two classes of oxidants,benzylic and heterocyclic alcohols could be effectively oxidized to carbonyl compounds.Specifically,the secondary alcohols could be effectively oxidized to ketones with excellent selectivity up to 100%in the presence of TBHP and the allylic alcohols could be effectively oxidized to aldehydes in the presence of O₂/TEMPO system.Electronic and steric effects are different from each other on the two classes of oxidative systems due to different reaction mechanisms.Next,a new class of heterogenized Cu complexes catalysts were prepared by anchoring Cu(OAc)₂ into the mesoporous channels of the bipyridylamine-modified SAB-15 and applied to the selective oxidation of ethylbenzene.Evidences from the experiments revealed that the mesoporous silicas retained their skeletion and ordered mesoporous structures after the organo-functionalization and Cu encapsulation.The remained channels were enough for the diffusion and reaction of substrate.The catalysts exhibited high efficiency for the selective oxidation of ethylbenzene to acetophenone using TBHP under mild conditions.The results also showed that the bipyridylamine-Cu complex species formed at the support surfaces were structurally stable.The resulting catalyst could be reused several times with negligible losses in activity and selectivity.