The Studies On The Synthesis Of Composite Zeolites With EUO Framework

Aromatic hydrocarbons, generally come from coal and petroleum, are important materials of organic chemical engineering. But their traditional production costs are high. Methanol can convert into aromatic hydrocarbons through some reactions such as dehydrogenation, dehydration, oxidation on the acidity of catalyst active sites. Thus, it can provide a new way to synthesize aromatic hydrocarbons. Therefore, selecting suitable catalyst has become the key to this synthesis process. The ZSM-5 possess particular two-dimensional ten-membered rings channel structure and excellent shape-selectivity. When modified ZSM-5 with metal is used in methanol transformation reaction, products has very strong trend of aromatization. The EU-1 zeolite, which possesses one-dimensional sinusoidal ten-membered ring pore channel and twelve-membered ring side-pocket, has special channel structure. It has strong acidity, stability and excellent shape-selectivity. ZSM-5 and EU-1 zeolites both can be used in catalytic reaction of methanol-to-olefins and xylene isomerization. Taking advantage of ten-membered rings of them, ZSM-5 and EU-1 are combined, then modified using metal. Thus EU-1/ZSM-5 compound optimized zeolite pore structure and active sites, and exhibited favorable synergistic effect in methanol aromatization reaction, which are valuable and important in theories research and practical application.Microporous EU-1/ZSM-5 composite zeolites containing iron were synthesized using preset crystal seed method in the alkaline system. The as-synthesized Fe-EU-1/ZSM-5 samples were characterized by a serious of techniques including X-ray diffraction (XRD), scanning electron microscopy (SEM), thermogravimetric-derivative thermogravimetric (TG-DTG), N2 adsorption/desorption, UV-visible diffuse reflectance spectroscopy (UV-Vis DRS) and X-ray absorption fine structure (XAFS). Focused on the influences of ZSM-5 content, SiO2/Al2O3 ratio of ZSM-5 and Fe content. The optimized synthesis conditions for the microporous EU-1/ZSM-5 composite zeolites containing iron are as follows:0.075～0.15% of the mass fraction of Fe in the original sol-gel,15.0～20.0% of the mass fraction of ZSM-5 zeolite in the original sol-gel and 50-60 of SiO2/Al2O3 molar ratio of ZSM-5 zeolite.Under the state of automotive cold start, the content of aromatic hydrocarbons in exhaust is highest. While the hydrocarbons (HCs) discharged are mostly alkanes in hot start or normal start. So the hydrocarbons (HCs) discharged in cold start is more harmful to the environment. Micro-mesoporous composite zeolite has synergistic effect in adsorbing macromolecules. So it has wide application foreground in the field of adsorption macromolecule. EU-1 microporous zeolite, which has well-developed one-dimensional microporous, is a significant shape-selective catalyst. But its pore size is smaller, so it is difficult to make macromolecules into its pores and to make macromolecules formed in the pores escape quickly from them. MCM-41 mesoporous zeolite which can adsorb macromolecules, such as toluene, has homogeneous and single pore. But its wall is thinner and its heat stability is poor. Considering high hydrothermal stability of microporous zeolite and channel superiority of mesoporous materials, micro-mesoporous composite molecular sieves was synthesized. It has wide application foreground in the field of adsorption and separation macromolecules.The EU-1/MCM-41 composite zeolite was synthesized in hydrothermal method by using TEOS, EU-1 seed and template CTAB. The as-synthesized samples were characterized by a serious of techniques including X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), N2 adsorption/desorption, UV-visible diffuse reflectance spectroscopy (UV-Vis DRS). The results show that the synthesized samples are EU-1/MCM-41 composite materials, and it can desorb toluene easily after adsorption. Focused on the influences of the proportion of EU-1 seeds, SiO2/Al2O3 ratio of EU-1, different synthesized method EU-1 seed, different silica source ratio, Na2O/SiO2 ratio and Fe content.Activation energy is an important dynamic parameter. According to the relationship charts of crystallization temperature to composite zeolite crystal coring speed and crystal growth speed, apparent coring activation energy (En) of EU-1/ZSM-5 is 44.71 kJ/mol and apparent growth activation energy (Eg) of EU-1/ZSM-5 is 56.89 kJ/mol. And apparent coring activation energy (En) of Fe-EU-1/ZSM-5 is 22.74 kJ/mol and apparent growth activation energy (Eg) of Fe-EU-1/ZSM-5 is 56.71 kJ/mol. The results show that iron ion added into composite zeolite is beneficial to crystal nucleation.