| Composite zeolite are two and two or more single zeolite combined together through different synthetic methods,it can get the perfoemance which a single zeolite dose not have and be able to play a mutual synergy.Due to composite zeolite combined the pore structure and acidity of two or more zeolite,so they have hierarchical porous,high hydrothermal stability and more acidity center.So that they can shows good performance in catalysis and adsorption reaction,they also plays an important role in many fields such as methanol conversion and petrochemical industry.ZSM-5 zeolite with a unique three-domensional cross channel structure,its ten-membered ring channels not only limit aromatic hydrocarbons under C10,but also limit large molecules to enter.L zeolite with a one-dimensional twelve-membered ring pore structure,suitable acidity,good hydrothermal stability and a wide range of catalytic properties,it can complement each other with ZSM-5 zeolite.Therefore taking ZSM-5 zeolite combined with L zeolite to play a synergistic effect,which will be a composite material with good catalytic performance.In this paper,in the system of K2O-HMBr2-SiO2-Al2O3-H2 O,L/ZSM-5 composite zeolite containing heteroatom with lamellar aggregationmosaic structure were synthesized by using TPAOH pre-treating ZSM-5 zeolite as crystal seed and using boric acid and nine water ferric nitrate as heteroatom source by crystal seed method.The synthetic samples were characterized by XRD,SEM,TEM,N2 adsorption-desorption,electrophoresis,NH3-TPD and so on.Exploring the influence of the amount of heteroatom on the composite zeolite with mosaic structure and synthesis technology of L/ZSM-5 composite zeolite.The results showed that B-L/ZSM-5 and Fe-L/ZSM-5 composite zeolite have large specific surface area,they were 370m2?g-1 and 373m2?g-1,respectively.It has changed the ratio of the amount of strong acid and the amount of weak acid of composite zeolite after introducing heteroatom.The synthetic samples have the characteristics of small spherical particles attached or embedded on the surface of the lamellar aggregates.With the increasing of the amount of iron atoms added,the absolute value of zeta potential decreased and the uniformity and aggregation degree were more obvious of the composite zeolite.The optimized of synthesis conditions were m（ZSM-5）/m（system）=0.0640.096,n（K2O）/n（Si O2）=0.40.45,n（Si O2）/n（Al2O3）=2528 and crystallization time was24 h.Hexamethonium bromide is the template with high charge density,it can guide growth and play a guiding and supporting role in the skeleton structure of the zeolite.At the same time,it has the function of balancing the skeleton charge and enhancing the thermal stability.Research group have synthesized L and EU-1 zeolite using the same template hexamethonium bromide,so try rocombine them together and improve the pore structure and microscopic property of the composite zeolite.L/EU-1 composite zeolite containing boron and iron was rapid synthesized by dry gel method with a small amount hexamethonium bromide as template.The synthetic samples were characterized in physical and chemical properties and structure,which were used in methanol aromatization probe reaction.The results showed that with increasing the mass fraction of boron and iron in the original sol-gel,the characteristic diffraction peaks of composite zeolites in the 22.7° and 25.6° migrate to higher angle and lower angle direction,respectively.The synthetic samples have the characteristics of mosaic morphology about 0.53μm of small spherical particles embedded in the side of tubular body.The pore properties showed that the composite zeolite containing both microporous and mesoporous.The amount and strength of acid of composite zeolite have changed after the introduction of boron and iron.For the preparation of L/EU-1 composite zeolite,the optimum conditions were n（K2O）/n（SiO2）=0.40.45,R=n（K2O）/n（K2O+Na2O）=1.The catalytic results showed that the quality composition of light aromatic hydrocarbon BTX in B-L/EU-1 and Fe-L/EU-1 composite zeolite methanol aromatization products were 40.89% and 33.93%,respectively.The content of xylene were highest among the two kinds of zeolite and the quality composition of xylene in B modified L/EU-1 composite zeolite methanol aromatization products is higher than Fe modified L/EU-1 composite zeolite by 4.9 percentage points. |
