Preparation Of Phosphotungstic Heteropolyacid Catalyst Membrane And Its Catalytic Performance In Cyclohexene Epoxidation

Membrane separation process is a novel technology applied in separation,concentration and purification with high efficiency.Modifications on membrane preparation material and applications of membrane separation are always the focus of membrane technology research.Catalytic membranes Often defined as in the separation reaction system wihich have a separation and catalysis double function.Catalytic membrane reactor(catalytic membrane reactor)is a comprehensive system,which combination of the process of separation and catalytic organically,In this system,the membrane separation unit is not combined with the catalytic reaction unit simply,use some methods to allow two units to combine together and interact each other to achieve the separation efficiency,the selectivity of reactants and products,the yield of products and so on,satisfy the demand of industry.How to prepare Catalytic membranes with high catalytic activity and improve the catalytic activity are still important and challenging.Take the above ideas into account,we synthesized catalytic membranes and catalysis with phosphoric acid on polyion liquid.The structures of these synthesized catalysts were characterized by IR spectrum,and the amounts of tungsten in the catalysts were determined by inductive coupled plasma emission spectrometer(ICP).These synthesized catalysts were used in the proposed solvent method for cyclohexene epoxidation with aqueous hydrogen peroxide to synthesize the cyclohexene oxide.The capability of catalysts and catalytic films were characterized by the conversion rate of cyclohexene and the selectivity of cyclohexene oxide.The main contents are as follows:The first chapter.Introduces the development and characteristics of membrane separation technology,the classification and application of catalytic films briefly.And then introduces the content and significance of the topic.The Second Chapter.we carried out a series of experiments on the surface of PVDF films to prepare catalytic films.First,to prepare PVDF-OH membrane,the PVDF film was modified with KOH and LiOH solution,the hydrophilicity and antifouling ability of membranes were improved.PVDF-Br membranes were prepared by the hydroxyl of on the surface of PVDF-OH films fixed initiator Br.Then PVDF-P4VP films were grafted onto the PVDF-Br membrane using SI-AGET ATRP method.Finally,prepare the PVDF-Q-P4VP membrane with a positively charged by PVDF-P4VP membrane reacted with bromo-n-octane in ethanol solution.The Third Chapter.First,1-vinyl-3-octyl-imidazolium bromide and 1-allyl-3-octyl imidazole bromide two kinds of ion salts were synthesized.PVDF-MPS membrance was successfully synthesized by the PVDF membrane and 3-Methacryloxypropyltrimethoxysilane(MPS).AIBN as the initiator,MPS was reacted with 3-octyl-Imidazolium bromide to get brown MPS-VOIMBr polymerized salt.The Four Chapter.The PVDF-P4VP film was immersed in peroxophosphoric acid solution,after the reaction was over,the film was treated and dried to get a catalytic film.Catalysts were prepared by ion exchange of MPS-VOIMBr and peroxotungstous acid solution.The capability of MPS-VOIM-GHPW catalysts and catalytic films were characterized by the conversion rate of cyclohexene and the selectivity of cyclohexene oxide.In the catalytic oxidation experiment of cyclohexene,the conversion of cyclohexene and the selectivity of cyclohexene oxide were determined by MPS-VOIM-GHPW and catalytic film use two different experimental devices.It was found that the conversion of cyclohexene was increased at first then remained constant,the change trend of the conversion rate was the same with the cyclohexene epoxidation experiment In the homogeneous system.The conversion rate reach 87%at 3 h and then the ratio is basically unchanged with the MPS-VOIM-GHPW.Under the condition of catalytic film,the conversion rate is constant at 7 h and the conversion efficiency reach 21%.It can be seen that the catalytic efficiency of the MPS-VOIM-GHPW is higher than the catalytic film.The experiment of cyclohexene oxidation in membrane reactors with the catalytic membrane,the selectivity of cyclohexene oxide increases at first then decreases,reaching the maximum value of 11.7%at 6 h.The change trend of selectivity of cyclohexene oxide is different from in the homogeneous reaction.