Preparation And Catalytic Performance Of ZSM-5 Immobilized Ionic Liquids Catalyst

Greenhouse effect has become a major problem in the process of industrialization,which needs to be tackled urgently.As the major component of greenhouse gases,the increase of carbon dioxide emissions directly leads to the aggravation of greenhouse effect.Therefore,the effective use of carbon dioxide resources has great economic and environmental significance.However,the chemical properties of carbon dioxide are stable,and the choice of catalysts is the key of its chemical conversion.Firstly,four kinds of molecular sieves ZSM-5 with different silicon-aluminum ratios.(Si/Al=21,38,50,85)were pretreated by hydrothermal method.Their chemical and crystalline structures were characterized by infrared spectroscopy and X-ray diffraction,and their thermal properties were tested by thermogravimetric analyzer.The results showed that the molecular sieve with a silicon-aluminum ratio of 50 has better performance and could be used as a carrier for the preparation of supported ionic liquid catalysts.Double salt ionic liquid [BMIM]Zn2Br5 was prepared by one-pot method,and then reacted with modified ZSM-5 carrier to prepare the immobilized ionic liquid catalyst ZSM-5-[BMIM]Zn2Br5.The chemical structure,crystalline structure,thermal properties and apparent morphology of the catalyst were analyzed by infrared spectroscopy,X-ray diffraction,thermogravimetric analysis and scanning electron microscopy,respectively.Catalytic properties of carbon dioxide and ethylene oxide/propane were investigated in autoclaves and fixed-bed reactors.The interaction of reaction temperature,pressure and time were investigated by orthogonal experiments in the process of autoclave catalysis.The number of cycles of immobilized catalysts was also studied.Single factor experiments were used to optimize the space velocity and feed ratio in the fixed bed catalytic process,and the service life of the catalyst was evaluated.The results showed that ZSM-5 immobilized double salt ionic liquid catalyst had good catalytic effect.Under the reaction conditions with reaction pressure of 2.5 MPa,reaction temperature of 130?,the feed ratio of 130:1 and the space velocity of 0.75 h-1,the conversion rate of raw materials could reach 84.3%and the selectivity of products could reach 96.1%for 10 h,and good catalytic performance could be maintained after continuous using for 80 h.