Study On The New Method Of Synthesis Of EU-1 Molecular Sieve

EU-1molecular sieve displays a one-dimensional orthorhombic system with10-membered ring?MR?openings?0.58�0.41 nm?running along the direction connected to the side pockets by 12 MR?0.68�0.58 nm?.Much attention has been focused on owing to its unique pore structure,which shows excellent selectivity and activity in many shape selective reactions.This paper is an exploratory study on new method for synthesis of EU-1molecular sieve:?1?EU-1 molecular sieve was synthesized by using organic base instead of inorganic base system.The aim was to expand the synthesis phase region,and to synthesize the high-silica EU-1 molecular sieve with strong acidity and high hydrothermal stability;?2?Hierarchical EU-1 molecular sieves was synthesized in situ pore forming,which vapor phase assisted biomass.Firstly,high-silica EU-1 molecular sieve with strong acidity and hydrothermal stability,had good application prospect in methanol to olefins reaction?MTP?process.So the synthetic study had important theory and application value.The study found that the adjustable SiO₂/Al₂O₃ ratio of synthetic EU-1 molecular sieve was in a narrow range in the conventional hydrothermal system:the pure EU-1molecular sieve could be obtained,when the SiO₂/Al₂O₃ ratios of the synthetic initial sol were lower than 120;co-crystallized ZSM-48 and EU-1 could be obtained when the SiO₂/Al₂O₃ ratios between 120 and 240;and the pure ZSM-48 molecular sieve was available when the SiO₂/Al₂O₃ ratios were greater than 240.However,the preparation of high-silica EU-1 molecular sieve usually needed auxiliary steam phase or dry gel and other special means of using special template.These methods made the scale application more difficult.This research group innovative attempted that high-silica EU-1 molecular sieves were prepared by TEAOH instead of NaOH as the base source in hydrothermal system.In order to investigate the feasibility and synthesis of the rules of the synthesis of EU-1,the samples were characterized by XRD,TG-DTG,zeta potential,pH value,SEM,FT-IR and NH₃-TPD techniques.Na⁺ations were conducive to the synthesis of more aluminous molecular sieve.TEA⁺cations were conducive to the synthesis of high-silica EU-1 molecular sieve owing to effectively balancing the low density framework negative charge of high silica molecular sieve.TPA⁺ations and TBA⁺ations acted strong template effect.Secondly,the EU-1 molecular sieve with one-dimensional pore structure had the disadvantages of diffusion limited,which seriously affected the catalytic activity and selectivity.The porous molecular sieve has the characteristics of strong acidity and stability,and the mass transfer performance can be improved through the introduction of the mesoporous.Therefore,it is of great academic research and practical value to explore the synthesis of hierarchical EU-1molecular sieve.In this paper,a new method for the synthesis of hierarchical EU-1molecular sieve,which was a kind of steam phase method and assisted in situ synthesis of biomass?sucrose,starch,etc?was explored.The EU-1 molecular sieves were synthesized under vapor phase synthesis condition.The influence factors of synthesis were investigated,such as crystallization time,solid-liquid ratio,template-silica ratio,alkali-silicon ratio,silicon source,etc.The samples were characterized by XRD,SEM and NH₃-TPD techniques.Comparing to traditional hydrothermal system,the samples were well crystallized,the dosage of the template and the base reduced,no mother liquor and high yield in the vapor phase system.Vapor phase synthesis was a kind of green and efficient synthesis method.On this basis,according to the new idea of the in situ pore forming of biomass?sucrose,starch and so on?,a new method of synthesis of hierarchical EU-1 molecular sieve was explored.First to prepare a semi-carbonization or fully carbonization of carbon silicon aluminum complex,and then the use of steam assisted synthesis of hierarchical EU-1.In order to investigate the effects of different carbonization methods and different sucrose content on the synthesis of EU-1 molecular sieve,the samples were characterized by XRD,SEM,FT-IR,NH₃-TPD and N₂ adsorption-desorption techniques.Its catalytic performance was tested by xylene isomerization.It was found that the samples which were prepared by adding semi-carbonization or fully sucrose possessed small size and rough surface in the vapor phase system.The mesoporous pore volume and surface area of the samples was increased significantly detected by N₂adsorption-desorption.The fully carbonization sucrose was more easy to realize the mesoporous because of different degree of carbonation.The catalytic activity and selectivity of hierarchical EU-1 molecular sieves which synthesized by adding semi-carbonization sucrose or fully carbonization sucrose were effectively improved.It can be seen that the method is feasible to improve the activity and selectivity of xylene isomerization through the synthesis of hierarchical EU-1 molecular sieve.