Studies On Environmentally Friendly Catalytic Epoxidation Of Propylene And Styrene

ZHOU Ning (Organic Chemistry)Directed by Prof. XI Zuwei and Prof. CAO GuoyingPropylene oxide is an important fundamental chemical material, and styrene oxide is an important intermediate for making medicine and perfume. Propylene oxide is produced with chlorohydrin method or Halcon method which gives rise to environmental pollution or a large amount of co-product. Styrene oxide is produced with bromohydrin method with serious environmental pollution. Molecular oxygen is the most desired oxygen source because it is clean and inexpensive. But except ethylene, epoxidation of other oleflns with 02 usually gives poor selectivity due to the severe reaction conditions. Our research group reported a new catalytic system, including 02 / 2-ethylanthrahydroquinone (EAHQ) / [~t -C5H5NC16H3313[P04(W03)4j (A), for epoxidation of many olefins with good catalytic activity and selectivity (except styrene). The catalyst A precipitates after epoxidation reaction for easy recycling. In this thesis, this system is used for epoxidation of propylene and styrene with good results.The solvent effect is investigated for epoxidation of styrene. In the mixed solvent of dimethyl phthalate / TBP or phenyl ether / TBP, the selectivity for styrene oxide is good but the conversion of styrene is low due to the coordination to the catalyst of the solvent. When part of dimethyl phthalate or phenyl ether is replaced by toluene, the conversion increases and the selectivity keeps constant. Under optimal conditions, in toluene / dimethyl phthalate / TBP, after EAHQ was oxidized with 02, then the catalyst and styrene were added, the conversion of styrene based on EAHQ is 68%, the selectivity for styrene oxide l~ased on styrene is 92% and theivTON of the catalyst is 500; in toluene / phenyl ether / TBP, epoxidation of styrene was performed with H202 generated in situ, the conversion is 46%, the selectivity is 94% and the product can be separated by distillation under reduced pressure.This catalytic system of 02 I EAHQ/ A is used for epoxidation of propylene for the first time, and a new concept of reaction-controlled phase transfer catalysis is proposed. Under optimal conditions, in the mixed solvent of xylene I TBP, the selectivity for propylene oxide based on propylene is 94%, and the yield based EAHQ is 85%. The catalyst is stable enough to recycle three times without loss in activity and selectivity it possesses the advantages of both homogeneous and heterogeneous catalysts. I~I2O2 generated by the most environmentally friendly 02 / 1-12 coupled with a reversible EAQ/EAHQ redox system, is used for direct transformation of propylene to propylene oxide with good selectivity. This is a novel, environmentally friendly and economical method for making propylene oxide without co-product. The paper about the epoxidation of propylene with this novel reaction-controlled phase transfer catalytic system has been accepted by SCIENCE.In the mixed solvent of xyleneITBP, the saturated concentration of EAHQ is 0.62 mol/L, in which the conversion of propylene based on EAHQ is 96% and the selectivity for propylene oxide based on propylene is 88%. In order to improve the efficiency of the system, we use anisole/toluene/ TBP as the solvent, in which the concentration of EAHQ is improved to 1.0 mol/L during the recycles of EAQ/EAHQ redox system. In this mixed solvent, the conversion of propylene based on EAHQ is 81% and the selectivity for propylene oxide based on propylene is 96%. The conversion and the selectivity keep constant when the system is recycled two times.The mechanism of the reaction-controlled phase transfer catalysis is studiedVby the determination of active oxygen and JR spectra. A turns into soluble active species [~r -C5H5NC16H33]3{P04[W02(02)j4} for epoxidation under the effect of H202. After H202 is used up, the active species returns into the original structure to precipitate.