【作者】 王莉；

【导师】 陈丰秋； 程党国；

【作者基本信息】 浙江大学 ， 工业催化， 2014， 硕士

【摘要】 多级孔道沸石分子筛由于结合了微孔沸石分子筛良好的催化性能和介孔材料优异的传质性能等优点,在大分子参与的反应中表现出良好的催化活性。硅烷偶联剂是一类具有有机官能团的有机硅化合物,它可与硅铝物种进行化学键接而植入沸石相中,通过抑制沸石分子筛晶体的生长而得到具有多级孔道的纳米晶体聚集体。本论文以正硅酸四乙酯为硅源,异丙醇铝、硝酸铝、偏铝酸钠等为铝源,四丙基氢氧化铵为模板剂,以硅烷偶联剂3-氨丙基三乙氧基硅烷(APTES)为软模板,通过水热法制备多级孔道ZSM-5沸石分子筛,并考评它在正庚烷催化裂解反应中的性能。具体研究内容如下：(1)考察了硅铝比、APTES用量、预晶化、碱度、铝源等对分子筛合成的影响,并对低硅铝比多级孔分子筛的合成进行了初步探索,采用XRD、FT-IR、 SEM、N2吸脱附及TEM等测试方法对样品的结构和形貌进行表征。结果表明,当APTES添加量为0.05,硅铝比由200增加至∞时,分子筛由纳米晶体聚集体转变为单晶,其外比表面积和介孔孔容减少。当硅铝比为200,APTES添加量由0增加到0.1时,其外比表面积和介孔孔容增加,但是结晶度有所降低,说明APTES对晶体生长有一定的抑制作用。全硅时,APTES添加量对样品的形貌影响不大,均是棺材型单晶,外比表面积和介孔孔容随APTES添加量的增加而增大。预晶化与否对样品的形貌、孔结构及收率都有一定的影响,尤其是APTES添加量较高的情况下。碱度的提高可缩短晶化时间,但样品尺寸增加,外比表面积和介孔孔容降低。以硝酸铝和偏铝酸钠为铝源时,所合成样品均是几百纳米大小的单晶,仍具有较高的外比表面积和介孔孔容。低硅铝比(SiO2/Al2O3=60)下,以偏铝酸钠为铝源,在较短的预晶化、硅烷化和晶化时间下,成功得到多级孔道ZSM-5沸石分子筛。(2)将采用不同的工艺条件(如铝源、软模板添加量)制备的多级孔道沸石分子筛材料用作考评催化剂,命名为H-1、H-2和H-3,其酸性通过NH3-TPD进行测试。H-2和H-3这两个催化剂的酸强度相近,H-1除了具备和它们相当强度的酸性位外,还含有一部分超强酸性位,总酸量：H-3>H-2>H-1。考察了以上几个催化剂在正庚烷裂解反应中的活性和稳定性,结果表明,这几种催化剂的初始活性都很高。其中H-1不但活性高,而且稳定性很好,H-3和H-2的稳定性不如H-1。更多还原

【Abstract】 Hierarchically porous zeolites, combing good catalytic performance of microporous zeolites and excellent mass transport of mesoporous materials, exhibit better catalytic effect in the reactions involving bulky molecules. Silane coupling agents with organic functional groups can be implanted into zeolite phase through chemically bonding with aluminosilica species. In such way, nanocrystals aggregates can be obtained by inhibiting crystal growth. In this thesis, hierarchically porous ZSM-5zeolite were prepared through hydrothermal method with tetraethyl orthosilicate as silicon source, aluminium isopropoxide, aluminum nitrate and sodium aluminate as aluminum source, tetrapropylammonium hydroxide (TPAOH) as template, silane coupling agent3-aminopropyltriethoxysilane (APTES) as soft template. The prepared samples have been evaluated in cracking reaction of n-heptane. The detailed results are summarized as follows:(1) Some factors affecting the synthesis were investigated, such as silica/alumina ratio, APTES content, pre-crystallization, alkalinity, aluminum source, etc. The structure and morphology of the samples were characterized by XRD, FT-IR, SEM, TEM and N2adsorption-desorption. The results indicate that the morphologies of the zeolites change from nanocrystals aggregates into single crystals when increasing silica/alumina ratio from200to∞at constant APTES content of0.05, the external specific surface area and mesopore decrease as well. When increasing amount of APTES at silica/alumina ratio of200, the external surface area and mesopore volume of the samples increase, while the degree of crystallinity decrease, indicating that the crystal growth is inhibited by APTES. When synthesizing Silicalite-Ⅰ, the morphology of the samples is coffin-type single crystal and do not change by APTES addition. The external specific surface area and mesopore volume also increase with increasing APTES content. Pre-crystallization has a certain impact on crystallinity, morphology, pore structure and yield of samples, especially under the condition of higher APTES addition. Improved alkalinity shortens the crystallization time, but the sample size increases and the external specific surface area and mesopore volume reduce. When using aluminum nitrate and sodium aluminate as aluminum source, samples are single crystals with a few hundred nanometers size and still have high specific surface area and mesopore volume. When synthesizing at low silica/alumina ratio (SiO2/Al2O3=60) with sodium aluminate as aluminum source, under the condition of shorter pre-crystallization, silylation and crystallization time, hierarchically porous ZSM-5zeolites are successfully obtained.(2) We name the hierarchically porous zeolite synthesized by different process parameters (such as aluminum source, APTES addition) as H-1, H-2and H-3. Their acidic properties were characterized by NH3-TPD. H-2and H-3have equivalent acid strength.H-1contains stronger acid site, in addition to acid sites equivalent with acid strength of H-2and H-3. The total amount of acid:H-3> H-2> H-1. Activity and stability of the above catalysts were evaluated in the n-heptane cracking reaction. The results indicate that all the catalysts exhibit very high initial activity, wherein stability of H-1catalyst is very good, but the stability of the other two is not.更多还原