Synthesis And Modification Of Small Crystal HZSM-5 Zeolite And Catalytic Performance In Methanol To Aromatics

As an important chemical raw material,light aromatic hydrocarbons are widely used in the industries of medicine,dyestuff,energy,etc.,which play an important role in the life of the people and the development of the country.In recent years,the traditional aromatics production route is not conform to the strategy of sustainable development with the shortage of oil resources and the increase in the demand for aromatics.Due to the methanol overcapacity,synthesis of high additional-value aromatics by the low-cost methanol,which can not only get rid of dependence on oil and gas resources,but also supplement the shortage of domestic aromatics and relieve the excess capacity of methanol,so the methanol to aromatics reaction has aroused wide attention and research.In this paper,the small crystal HZSM-5 zeolite was prepared and modified with metal zinc,the relationship of texture properties and acid characteristics with the catalytic performance in methanol to aromatics was studied.In this study,the small crystal HZSM-5(S-HZ)zeolite was prepared by adding the surfactant and reducing the temperature of the hydrothermal reaction in the synthesis,the catalytic reactivity of these catalysts for the conversion of methanol to aromatic was tested.Under the reaction conditions: the temperature of 430 °C,the pressure of 0.1 Mpa,the LHSV of 1.2 h-1 and the flow of N2 = 25 m L/min,the BTX yield of S-HZ zeolite(27 %)is slightly higher than micro-size HZSM-5(M-HZ)zeolite(24 %),and the life-span of S-HZ zeolite is 218 h,which is far longer than M-HZ zeolite.The zeolite was characterized by XRD,SEM,TEM,N2 isothermal adsorption-desorption and NH3-TPD.The results show that compared with M-HZ zeolite,S-HZ zeolite with smaller crystal size,higher surface and larger pore volume,can improve the carbon capacity of zeolite catalyst which determine higher stability of S-HZ.Zn-containing S-HZ(Zn/S-HZ)zeolite was prepared by impregnation,ion exchange,direct synthesis and physical mixing.The zeolite was characterized by XRD,SEM,TEM,N2 isothermal adsorption-desorption,NH3-TPD and XPS,the catalytic reactivity of these catalysts for the conversion of methanol to aromatic was tested.The BTX yield of Zn/S-HZ zeolite is higher than S-HZ,in addition,Zn(IE)/S-HZ zeolite was prepared by ion exchange shows the highest BTX yield is 45.5 %,due to the introduction of Zn species exist in the form of Zn OH+ and contain more medium-strength acid.Zn(DS)/S-HZ zeolite was prepared by direct synthesis shows the largest pore volume is 0.257 cm3g-1,which shows the longest life-span is 276h.