| Selective oxidation of alcohols is a very important and most widely used reaction in organic synthesis.Schiff base complexes have been studied and applied in the selective oxidation of alcohols for their excellent catalytic performance.However,the homogeneous system of Schiff base complex suffer from the separation and reusability.Based on the structural characteristics and excellent physical and chemical properties of SBA-15,fixation of schiff base metal complex with excellent catalytic performance can not only exert its catalytic performance,but also realize the recycling of catalyst.Firstly,asymmetric Schiff base copper complex were supported on SBA-15 to form SBA-15-NH2-Cu L1 and SBA-15-NH2-Cu L2,and their related characterization and catalytic activity were tested.By exploring the reaction conditions such as solvent,oxidant,temperature,amount of catalyst and reaction time,the suitable conditions for catalytic oxidation of benzyl alcohol were obtained.The application conditions of catalyst SBA-15-NH2-Cu L1 were as follows,2 mmol benzyl alcohol,0.02 g catalyst,10 mmol 70%t-Bu OOH,1 m L[Bmim][BF4],5 mol%TEMPO,40℃,12 h.Under these conditions,the conversion rate of benzyl alcohol and the yield of benzaldehyde reached 81.83%and 80.57%.The application conditions of catalyst SBA-15-NH2-Cu L2 were as follows,2 mmol benzyl alcohol,0.02 g catalyst,10 mmol 70%t-Bu OOH,1 m L[Bmim][BF4],5 mol%TEMPO,40℃,12 h.Under these conditions,the conversion rate of benzyl alcohol and the yield of benzaldehyde reached 79.55%and 76.38%.The catalytic system has high reusability,and has good catalytic oxidation activity for most alcohols,which can be oxidized into corresponding aldehydes or ketones,it has universal applicability.Subsequently,the ethylene diamine asymmetric Schiff base copper complex catalysts SBA-15-NH2-Cu L3 and SBA-15-NH2-Cu L4 supported by SBA-15 were prepared experimentally.The application conditions of catalyst SBA-15-NH2-Cu L3were as follows,2 mmol benzyl alcohol,0.01 g catalyst,10 mmol 70%t-Bu OOH,1 m L[Bmim][BF4],5 mol%TEMPO,40℃,12 h.Under these conditions,the conversion rate of benzyl alcohol and the yield of benzaldehyde reached 90.37%and 80.29%.The application conditions of catalyst SBA-15-NH2-Cu L4 were as follows,2 mmol benzyl alcohol,0.10 g catalyst,10 mmol 70%t-Bu OOH,1 m L[Bmim][BF4],5 mol%TEMPO,40℃,12 h.Under these conditions,the conversion rate of benzyl alcohol and the yield of benzaldehyde reached 81.38%and 75.00%.The catalytic system has high reusability,and has good catalytic oxidation activity for most alcohols,which can be oxidized into corresponding aldehydes or ketones,it has universal applicability.Finally,the 3,4-Diaminotoluene asymmetric Schiff base copper complex catalysts SBA-15-NH2-Cu L5 and SBA-15-NH2-Cu L6 supported by SBA-15 were prepared experimentally.The application conditions of catalyst SBA-15-NH2-Cu L5were as follows,2 mmol benzyl alcohol,0.10 g catalyst,10 mmol 70%t-Bu OOH,1m L[Bmim][BF4],5 mol%TEMPO,50℃,5 h.Under these conditions,the conversion rate of benzyl alcohol and the yield of benzaldehyde reached 85.43%and 83.09%.The application conditions of catalyst SBA-15-NH2-Cu L6 were as follows,2 mmol benzyl alcohol,0.10 g catalyst,10 mmol 70%t-Bu OOH,1 m L[Bmim][BF4],5 mol%TEMPO,50℃,3 h.Under these conditions,the conversion rate of benzyl alcohol and the yield of benzaldehyde reached 81.79%and80.54%.The catalytic system has high reusability,and has good catalytic oxidation activity for most alcohols,which can be oxidized into corresponding aldehydes or ketones,it has universal applicability.The experimental results showed that when the asymmetric Schiff base of 3,4-Diaminotoluene was immobilized to SBA-15,the catalytic performance was the best and the reaction time is shorter.The complex immobilized on SBA-15 could effectively prevent the oxidation of the ligand or form oxo-and peroxo-bridged complexes in the oxidation process,thus improving the catalytic performance. |
