| Metal-organic skeleton material is a kind of metal ions or metal clusters and single or multi-toothed organic ligands containing O,N,S,P,etc.,through the way of coordination,self-assembly together to form a multidimensional mesh crystal structure.This kind of organometallic material has some characteristics,such as porosity,large surface area,unsaturated metal ligand and structural diversity.In recent years,the applications of porous MOFs materials in electrochemistry,catalytic chemistry,adsorption and biomedicine have been widely studied.In the process of air epoxidation of olefin,initiators such as CHP and TBHP are usually added in order to increase the efficiency of epoxidation reaction,which increases the complexity of the experimental process and also increases the separation cost of epoxy products.Therefore,in consideration of the shortcomings of previous research techniques,we made the following improvements to carry out environmentally friendly air epoxidation of diolefin and triolefin without the addition of initiators and reducing agents.The main research contents of this paper are as follows:1.ZnCo-MOFs bimetallic framework catalyst was prepared by mixed solvent-thermostatic method.The air epoxidation of ZnCo-Mo Fs was catalyzed by ordinary water bath without any reducing agent or initiator.The effects of crystallization conditions on the activity of catalyst,such as different synthesis solvent and ratio,different structure guide agent and different assembly stirring mode,were investigated.At the same time,the influences of different molar ratio,reaction solvent and reaction mode on the air epoxidation of olefin were also discussed.The results showed that under the conditions of reaction temperature of 90 ℃,air flow rate of 40 ml/min and reaction time of 5 h,when the molar ratio of cyclooctene to styrene was 5:1,the conversion of di-olefins was 97.0% and 98.8%,and the selectivity of epoxide was 98.4% and 92.7%,respectively.In the catalytic tri-olefins reaction system,when cycloctene: styrene: α-methylstyrene = 2:3:1,the conversion of olefin was 65.9 %,88.4 % and 98.3 %,respectively,and the corresponding epoxide selectivity was94.5 %,94.3 % and 97.6 %.The ZnCo-MOFs bimetallic spindle catalyst showed good cyclic stability,and the catalytic activity did not decrease significantly after 6 times of repeated use.2.The monometallic Co-MOFs catalyst was prepared by static hydrothermal method and static mixed solvothermal method.The air epoxidation reaction of di/tri-olefins was carried out by heating in ordinary water bath without any reducing agent or initiator.We studied the activity of catalyst synthesized by crystallization under the conditions of different single metal salts,different single cobalt salts and different amounts of single cobalt salts.The results showed that after reaction at 90 ℃,air flow rate 40 ml/min and 5 h,the Co-MOFs spindle-shaped catalyst prepared by solvothermal method could catalyze di-olefins α-pinene and styrene with the conversion of 98.6% and 91.5%,respectively.When the molar ratio ofα-pinene and α-methylstyrene was 5:1,the conversion of di-olefins could reached 97.1 % and98.4 %,and the selectivity of epoxide was 91.9 % and 91.1 %,respectively.When α-pinene:styrene: α-methylstyrene = 3:1:2,the conversion of α-pinene: pinene: α-methylstyrene was88.7 %,86.8 % and 94.2 %,respectively,and the selectivity of epoxide was 96.9 %,94.1 %and 98.8 %.The monometallic single-solvent Co-MOFs showed stable catalytic activity in epoxidation of α-pinene and α-methylstyrene with air,and the activity of the catalysts did not decrease significantly after five cycles of use. |
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