Efficient Epoxidation And Reaction Mechanism Of Multi-olefins With Air Over Bimetal MOFs Catalysts Assisted By Microwave/Ultrasound

The development of science and technology has brought about a lot of technological progress,microwave/ultrasonic technologies have also been fully developed and applied in various fields.Among those,more and more scientific researchers use microwave/ultrasonic as a heating method in scientific researches.This heating method is cleaner and more economical than traditional ones,and it takes less time to reach the target temperature.Based on these advantages,microwave/ultrasonic technology has been gradually used in many heating reactions,e.g.in epoxidation reactions.This heating method can shorten the reaction time and effectively increase the product yield.However,in many epoxidation reactions,it is necessary to add organic peroxides such as tert-butyl hydroperoxide as an initiator,which not only makes the reaction process more complicated,but also increases the separation cost.Therefore,we have researched and developed several types of bifunctional MOFs catalyst materials to realize the high-efficiency epoxidation reaction of olefins and air assisted by microwave/ultrasonic methods without any initiator and co-reducing agent.The main research contents of this thesis are as follows:1.A series of bifunctional ZnCo-MOF materials were synthesized by rotating hydrothermal method using ZnO as the zinc source.It could catalyze the epoxidation reaction of multi-olefins with air under microwave heating without any initiator or co-reducing agent.The effects of different preparation methods,different metal oxides,different ZnO content,and other crystallization synthesis conditions on the catalyst activity were discussed.The effects of different olefin molar ratios,different reaction modes,and different solvents on the air epoxidation of multi-olefins were also investigated.At the same time,the electron transfers mechanism between diolefins and the reaction mechanism of di-olefin epoxidation were explored as well.Under the reaction conditions of 85℃,30 mL/min air and 4 h,whenα-pinene andα-methylstyrene were mixed at a reaction molar ratio of 5:1,the conversion of two olefins reached 86.3 and 99.8 mol%,and the epoxide selectivity were 93.8 and 94.3%,respectively.In the tri-olefin reaction system,whenα-pinene,styrene andα-methylstyrene were mixed in a reaction molar ratio of 3:1:2,the three olefins reached the highest conversions of 96.7,95.3 and 97.5 mol%,in which the total conversion attained above 96mol%.2.By adopting the static hydrothermal crystallization method,a series of double-ligand ZnCo-MOFs catalyst materials were synthesized using terephthalic acid and2-methylimidazole as mixed ligands.It was used to catalyze the epoxidation reaction of multi-olefins with air.In addition,we discussed the effects of different assembly and stirring methods,ligands,synthesis methods,metal sources,and other conditions on the epoxidation activity.The effects of different microwave powers and different oxidants on the reaction were also explored;and the mutual promotion of different diolefins and different triolefins was discussed as well.The results showed that using the microwave-assisted heating reaction method without any initiator or co-reducing agent,cyclooctene and styrene obtained the high conversions of 80.8 and 96.1 mol%,respectively.Under the same reaction conditions,in the reaction system of triolefins cyclooctene,styrene,andα-methylstyrene,the optimal reaction molar ratio was 3:1:2,with which the promotion effect among three olefins was enhanced notably,with 82 mol%conversions of olefins.3.Zn（OH）₂/Co-MOF composite was successfully synthesized by post implantation method,which catalyzed the epoxidation reaction of diolefins with air without the presence of initiator and co-reducing agent.The effects of stirring mode,different amounts of Zn（OH）₂ or Co-MOF on the catalytic performance of the composites were discussed.The different reaction conditions in the air epoxidation of olefins were also investigated.The research results indicated that under the reaction mode of microwave-assisted heating,the conversions ofα-pinene and styrene reached 80.9 and 81.4 mol%,with the epoxide selectivity of 94.8 and 95.0%,at 85℃ and 30 mL/min air flow rate for 4 h.