【作者】 熊晓云；

【导师】 李守贵； 肖丰收；

【作者基本信息】 吉林大学 ， 无机化学， 2007， 博士

【摘要】 本文研究以NaY沸石导向剂作为活性硅源合成A、X、Y型沸石的合成研究工作。旨在探讨硅源活化法合成沸石分子筛特点、规律及该方法在合成某些特征产物上的优势,如晶化速度,产物粒度,硅铝比等。在第一章绪论中,介绍了无机多孔材料的分类,详细介绍了无机微孔材料的历史,发展现状,分类,应用,晶化机理及合成路线以及本课题选题的目的和意义,主要结果等;第二章中应用导向剂提供全部硅源法低温快速合成了纳米A型沸石,讨论了导向剂配比及各种合成因素的影响,对导向剂进行了初步表征;第三章中合成了纳米NaX型沸石,并详细讨论了各种合成因素,如合成温度,硅铝比,水铝比,碱铝比对合成产物的影响,讨论了NaY沸石导向剂作为活性硅源在合成中晶化速度快和容易生成纳米晶的优势,并对合成的纳米X型沸石进行了表征;第四章中应用导向剂为硅源在60°C¹40°C宽的温度范围内和SiO₂/Al₂O₃=8²0宽的投料硅铝比范围内合成了NaY沸石。详细讨论NaY沸石导向剂作为活性硅源在合成NaY沸石时的规律,特点,合成出了纳米NaY沸石及高硅NaY沸石,讨论了各种合成因素的影响;第五章中发现了在同一低硅铝比（SiO₂/Al₂O₃=2）配比下,随晶化温度升高,晶化产物由X型沸石向A+X型沸石和A型沸石变化的新现象,应用导向剂为硅源在钠体系中合成出了低硅X型沸石和低硅A+X型沸石混晶,并对合成低硅X型沸石的各种因素进行了讨论;第六章为总的结论、讨论及展望。更多还原

【Abstract】 Zeolites molecular sieves have been widely used in many fields such as ion-exchange, adsorption, separation and catalysis for its special and uniform pores. The discovery of zeolites is early and the kinds of zeolites have been greatly enriched by semicentennial development, but few zeolites have been applied in the industry except A, X, Y, L, MOR, ZSM-5, and Beta. Zeolites A, X, Y are the earliest discovered molecular sieves, but until now, they are still widely used in the industry. The study of their growth not only has theory meaning but also has practical worthiness.Many factors could influence the syntheses of zeolites, and silica source is a most important one. The active of silica source could influence the synthesized product, for example, in the synthesis of NaY zeolite with water glass, 5% NaY seeds solution is needed. In this work, zeolites A, X, and Y are synthesized by using NaY seeds solution as silica source, and the crystallization kinetics are studied in detail. Furthermore, NaY seeds solution has been primarily characterized. The reasons for the three zeolites we selected are as follow: （1） they are all widely used in industry; （2）βcage is the same building units for the three zeolites.Zeolite A has been widely used in laundy detergents. In this work, zeolite A was fast crystallized at low temperature by using NaY seeds solution as a silica source and the nucleation/crystallization kinetics of A zeolite were investigated in detail. It was found that NaY seeds solution with a proper ratioes of SiO₂/Al₂O₃ and Na₂O/SiO₂ is suitable for the synthesis of A zeolite. The composition of NaY seeds solution with molar ratios of 18Na₂O:1Al₂O₃: 19SiO₂: 365H₂O was chosen for the study. The obvious advantages of the seeds solution method for the synthesis of zeolite A are fast crystallization rate and low crystallization temperature. For example, by using NaY seeds solution as silica source, zeolite A can be fully crystallized for 4⁵ h at 60°C with the batch composition 4Na₂O:1Al₂O₃: 2SiO₂: 100H2O, while 9¹0 h is needed if the silica source is water glass and the crystallinity is only 90%. Furthermore, the method is of benefit to the synthesis of nano-sized A zeolite at low alkalinity. In the reference, nano-sized A zeolite was synthesized with H₂O/Na₂O=13, while in this work, the same sized A zeolite was obtained with H₂O/Na₂O=20. A zeolite with different particle size was obtained and the corresponding Ca²⁺ ion exchange capacity was studied. It was found that zeolite A with crystal diameters of 500¹000 nm has good calcium ion exchange capacity, and too small particle size affects calcium ion exchange capacity of A zeolite for particle aggregating. Characterization of NaY seed solution by 29Si NMR and UV Raman techniques suggests that zeolite primary building units such as 4-ring, 6-ring andβcage contained in NaY seed solution possibly promote the nucleation and growth of LTA zeolite.There are considerable interests in the syntheses of nanosized zeolites in the past decade owing to their widely applications as supports for catalytic, catalyst for petrochemical reactions, sorbent, and in the preparing of functional materials. In this work, nanosized NaX zeolite have been synthesized using NaY seeds solution as silica source, and the factors in the synthesis, such as crystallization temperature, SiO₂/Al₂O₃ ratio, H₂O/Al₂O₃ ratio and Na₂O/ Al₂O₃ ratio are discussed. Different factors are taken into account and the final synthesis condition is chosen with the batch composition 5.5Na₂O:Al₂O₃: 3SiO₂: 156H2O, and crystallized at 60°C for 8 h. SEM images of the NaX nanocrystals show that the particle sizes of the NaX nanocrystals are mostly in the range of 20⁵0 nm. The high external surface estimated from the N₂ adsorption isotherms and a new broad silanol vibration in the FT-IR spectra also suggest that the particle sizes are very small. For comparision, water glass instead of zeolite Y seeds solution as silica source is used to synthesize NaX zeolite. It is found that: （1） With the same gel composition of 5.5Na₂O:Al₂O₃: 3SiO₂: 156H₂O, the induction period and crystallization time of NaX zeolite are about 2h and 6⁸h when NaY seeds solution is used as silica source. While the induction period and crystallization time are prolonged to 6h and 14¹6h when water glass is used as silica source. （2） B. Z. Zhan et al. synthesized NaX nanocrystals at low temperature （60°C） with gel composition 5.5Na₂O: Al₂O₃: 4SiO2: 190H2O. The particle sizes of the product increase to be in the micron range with the crystallization temperature increase to 90°C. However, nanosized NaX zeolite could be obtained at 60⁹0°C by using NaY seeds solution as a silica source. Compared with conventional synthesis, the method shows obvious advantages including relatively short crystallization time and small crystal sizes.NaY zeolite is one of the most important zeolites for its wide applications in petrochemical industry. Compared with NaX zeolte, the synthesis of NaY zeolite is more difficult for its higher SiO₂/Al₂O₃ ratio, and requiring active raw material. For example, synthesis of NaY zeolite is difficult from water glass as single silica source, and usually NaY seeds solution is needed. Here, we demonstrate the synthesis of the NaY zeolite by using NaY seeds solution as a silica soure at the temperature ranged 60¹40°C and SiO₂/Al₂O₃ ratio 8²0. Furthermore, different factors of the synthesis are discussed, such as crystallization temperature, crystallization time, SiO₂/Al₂O₃ ratio and Na₂O/SiO₂ ratio, and we find that low temperature （≤100°C） and short crystallization time are preferred for the preparation of nanocrystals. Particlularly, the crystallization temperature could be ranged from 100 to 140°C using NaY zeolite seeds solution while NaY zeolite is normally synthesized in the temperature of 100°C using water glass as silica source. Different factors for the synthesis of NaY zeolite and the kinetics of crystallization of NaY zeolite are studied, and we findd that with the crystallization temperature increased, the crystallization rate of zeolite Y increased and hydrothermal conversion from Y to zeolite P became faster, but the crystallization area of zeolite Y is reduced. Furthermore, reducing the molar ratio of Na₂O/SiO2 or increasing the molar ratio of SiO₂/Al₂O₃ could severely redue the crystallization rate. Interestingly, when the crystallization temperature is higher than 100°C, not only P but also ECR-1 and MOR could appear when the Na₂O/SiO₂ ratio is further reduced. Moreover, proper conditions for the crystallization of nanocrystals of NaY zeolite are obtained including aproperate long aging time of NaY seeds solution; low crystallization temperature and short crystallization time. Additionally, NaY zeolite with high SiO₂/Al₂O₃ ratio about 6 was also synthesized according to the reaction condition. The physical properties of the high silica NaY was characterized by several methods.The SiO₂/Al₂O₃ ratio of X-type zeolite is between 2 and 3, and it is usually above 2.4. X-type zeolite with SiO₂/Al₂O₃ about 2 is more efficient in removing not only calcium hardness but also magnesium hardness from water than zeolite A because of its larger pore size and high aluminates content. It is well known that in Na+ system, zeolite A crystallizes when the SiO₂/Al₂O₃ ratio is below 3 in the aluminosilicate gel. However, if K+ is added in the system, high aluminum content of NaX zeolite （SiO₂/Al₂O₃≈2） crystallizes. In this system, the present of potassium ion can suppress the nuclei of NaA zeolite. However, sodium form of the zeolite exchanging calcium and magnesium from solution is faster than the mixed sodium potassium form, and until now, few papers report the crystallization of high aluminous zeolite X （SiO₂/Al₂O₃≈2） from pure sodium system. We studied in detail on the synthesis of high aluminous zeolite X with low SiO₂/Al₂O₃ molar ratio in the batch by using NaY seeds solution as a silica source, and found that the product will change from X zeolite to mixture of A+X to A zeolite with the crystallization temperature increased, which was explained from the view of mesostability, thermodynamics and kinetics. In my work, NaX zeolite with SiO₂/Al₂O₃≈2 was successfully synthesized by optimizing the reaction condition and was characterized by several methods. The content of A and X zeolite in the product can be controlled by changing the crystallization temperature or the ratio of Na₂O/SiO₂. Additionally, it is also a new method for the synthesis of high aluminous zeolite X+A zeolite mixture, which is important for the potential use in laundry detergents. Compared with conventional synthesis from water glass as silica source, NaY seeds solution as silica source in the synthesis has obvious advantages such as short crystallization time and preparing highly aluminous zeolite X.This work demomstrate a novel method to synthesize A, NaX and NaY by using NaY seeds solution as silica source, and it is also a method of activation of silica source in the synthesis of aluminosiliacte zeolites. In this method, the active siliceous or aluminosiliceous precursors were obtained by adding definite quantity of sodium hydroxide and aluminate source to sodium silicate. Possibly, the promotion of crystallization for the three zeolites may due to the same building unit exisiting in the zeolites and the NaY seeds solution. The method should be extended to the synthesis of other zeolites.更多还原