论文总字数：31700字

摘 要

Beta分子筛是一种广泛应用于裂化、异构化和烷基化等石油化工过程的催化剂。一般的合成方法得到的是微米级的Beta分子筛，而纳米级的分子筛具有更好的比表面积，短的分子晶内扩散路径，反应速率高，失活慢等优点。此外，为了扩展分子筛的应用范围，许多金属经浸渍或者离子交换被引入分子筛，但是此时金属大多位于分子筛表面或者孔道内而导致孔道易被阻塞，因此，更理想的途径是通过直接合成法将金属引入分子筛骨架，制备相应的骨架杂原子分子筛。本文在充分分析前人及本课题组已有成果的基础上，通过直接静态水热法新路线合成得到杂原子Mg-Beta分子筛，所用方法的关键是在酸性条件下水解正硅酸乙酯（tetraethylorthosilicate, TEOS）得到硅的前驱物后，向其中加入模板剂（tetraethylammonium hydroxide, TEAOH，氢氧化四乙胺）和铝源（NaAlO_2，偏铝酸钠），生成碱性凝胶，然后在水热晶化得到产物。具体结果如下:

（1）分别采用金属Mg的硝酸盐与TEOS在酸性条件下共水解路线，水热合成相应的杂原子Beta分子筛，并通过XRD、IR、UV-vis、ICP元素分析、SEM等表征所得样品。结果表明，通过酸性条件下共水解的直接静态水热合成法成功合成了上述骨架杂原子Beta分子对比之下，传统碱水解条件下得到的Mg-Beta样品结晶度要低得多，甚至无法得到Mg-Beta分子筛。

(2) 将合成出的杂原子Beta型分子筛用作Knoevenagel缩合反应的催化剂，结果表明，骨架Mg-Beta分子筛的催化性能明显高于浸渍的样品,碱土金属杂原子Silicalite-1分子筛表现出较高的催化活性和稳定性。

关键词：杂原子分子筛 水热合成 酸水解正硅酸乙酯

Synthesis of hetero atoms Mg-Beta zeolites and performanMg study

ABSTRACT

Zeolite Beta has been widely used as the catalysts for petrochemical processes such as isomerization, cracking and alkylation. The micro-sized zeolite crystals are often obtained by the traditional synthesis routes. Since nanocrystalline zeolites can result in high BET surface areas, shortening of the molecular diffusion path, and improvement of the catalytic activity, there has been a growing interest in the synthesis of nano-sized zeolites, including zeolite Beta. Moreover, to introduce additional functionalities and broaden their applications, many heteroatoms have been incorporated into the framework of zeolites through impregnation or ion-exchange, where the heteroatoms mainly exist on the surface or in the pores of zeolites, blocking micro-channels. So, the incorporation of metal ions into the framework of zeolite via a direct hydrothermal synthesis is a more desirable approach. Based on this background and the recent research progress of our group, this dissertation concentrates on the synthesis of Mg-Beta, through a direct and static hydrothermal route. The silica (or silica-metal) precursor was prepared by the hydrolysis of teraethylorthosilicate (TEOS) (or with metal ions) in an unconventional acidic media, and the subsequent hydrothermal crystallization was carried out under the conventional strong basic condition by adding the structural directing agent (tetraethylammonium hydroxide, TEAOH) and Al sourMg (sodium aluminate, NaAlO₂).

(1) Isomorphously substituted Me-Beta zeolites were synthesized by a directly hydrothermal method through the co-hydrolysis of TEOS with metal ions in acidic media. The as-calcined Me-Beta zeolites were characterized by XRD, ICP elemental analysis, BET surfaMg area, IR, UV-vis, SEM. The metal ions have been successfully introduced into the framework of zeolite Beta and the morphologies of

the obtained zeolites are smiliar to that of the pure zeolite Beta. Compared to the conventional route that was co-hydrolyzed of TEOS with metal ions in the basic condition, all the Me-Beta synthesized by the acidic co-hydrolysis have better BEA phase. For Mg-Beta, it can’t be obtained in the base co-hydrolysis condition. Thus, it can be seen that the acidic co-hydrolysis step is proposed to facilitate the formation of the metal-bearing nucleus for the further growing of zeolite crystals.

(2) The obtained heteroatomic zeolites were used as catalysts for Knoevenagel condensation reaction. The results show that the activity of Mg-Beta were significantly higher than the impregnation samples,

KEYWORDS: Beta zeolite; n; Heteroatom-Substituted zeolite; Hydrothermal Synthesis; acid-catalyzed hydrolysis of tetraethylorthosilicate；

目 录

摘要 I

ABSTRACT II

目 录 1

第一章 文献综述 1

1.1 Beta分子筛结构及应用 1

1.1.1 固体碱的应用 1

1.1.2 Beta分子筛结构 3

1.1.3 Beta分子筛的应用 4

1.2 分子筛的合成方法 5

1.2.1 水热合成法 5

1.2.2 溶剂热法合成 6

1.2.3 蒸汽相合成法 7

1.2.4 极浓体系合成法 7

1.2.5 微波合成法 8

1.2.6 导向剂法 8

1.2.7 转晶法 9

1.3 沸石合成的影响因素 9

1.3.1 SiO₂/Al₂O₃的影响 10

1.3.2 晶化pH值的影响 10

1.3.3 水含量影响 11

1.3.4 硅源的类型 11

1.3.5 模板剂种类及用量影响 12

1.3.6 碱性无机阳离子的影响 13

1.3.7 晶化温度的影响 13

1.4 沸石分子筛的合成机理 14

1.4.1 固相转变机理 14

1.4.2 液相转变机理 15

1.4.3 双相转变机理 15

1.5分子筛在Knovevebagel缩合反应中的应用 16

1.5 论文研究思路和内容 16

第二章 实验方法 18

2.1 实验所用试剂及仪器 18

2.2 分子筛的制备 18

2.2.1 酸水解TEOS和金属源水热合成Mg-Beta分子筛 18

2.3 分子筛的表征 19

2.3.1 X射线衍射仪（XRD） 19

2.3.2 扫描电镜（SEM） 19

2.3.3 透射电镜（TEM） 20

2.3.4 红外光谱分析（IR） 20

2.3.5 比表面积和孔径分布测试（BET） 20

2.3.6 电感耦合等离子发射光谱仪（ICP） 20

2.3.7 紫外可见漫反射分析（UV-vis） 20

第三章 Mg—Beta沸石分子筛的合成和催化性能 21

3.1. 不同Mg含量对合成Mg-Beta的影响 21

3.2 碱土金属Mg-Beta的表征 22

3.2.1 UV-vis分析 23

3.2.2 FT-IR分析 23

3.4 SEM 24

3.5合成条件对其的影响 25

3.5.1 H₂O/SiO₂ 25

3.5.2 SiO₂/Al₂O₃ 25

3.5.3晶化天数 26

3.6 催化性能 27

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