层状分子筛的层间修饰与结构解析
发布时间：2018-07-17 07:39
【摘要】：本论文以改善分子筛对大分子反应物与大分子产物的扩散限制,提高催化活性中心的可接近性,合成新型分子筛材料为目的,先后开展分子筛层状前驱体的层间扩孔、硅锗分子筛后处理与直接合成分子筛纳米片等研究工作。第一部分采用有机硅烷Me2Si(OEt)2 (DEDMS)对分子筛层状前驱体Nu-6(1)插硅,获得结构新颖的IEZ-Nu-6(1)分子筛。通过考察合成条件,首次发现在乙醇溶液中可以获得有序的晶体材料,而在水溶液中有序程度要差。因Nu-6(1)的层间模板剂在水中易从层间扩散至溶液中,此时有机硅烷没有插入层间,导致扩孔失败,而在乙醇中模板剂扩散速度较慢,模板剂脱除过程与插硅过程速度平衡,扩孔易成功。对IEZ-Nu-6(1)进行结构优化与精修,表明IEZ-Nu-6(1)具有两套孔径大小不同的十元环孔道。将Nu-6(2)、IEZ-Nu-6(2)用于催化乙醇与乙酸的酯化反应,后者具有更高的转化率,因其具有更大的孔径和亲水性。第二部分利用分子筛层状前驱体的结构特点,合成超大孔分子筛。目前为止,采用层间插硅合成的分子筛,其孔道均不超过十二元环。本文采用分子筛层状前驱体PREFER,以及有机硅烷1,3,5,7-四甲基环四硅烷(D4h),在硝酸溶液中层间插硅扩孔,获得含有十四元环的晶体材料IEZ-FER(D4h)。采用DFT对结构进行优化与精修,结果表明IEZ-FER(D4h)具有一套十四元环和一套十二元环孔道。通过XRD、 UV-Ramaru NMR、IR、N2吸附等手段表征IEZ-FER(D4h)物理化学性能,并采用蒸汽吸附表征材料的孔道大小、亲疏水性与水热稳定性。第三部分采用1-丁基-3-甲基咪唑盐为模板剂,合成了2个晶胞厚度的硅锗分子筛纳米片ECNU-9,不仅具有很高的比表面积,而且含有多级孔道。分子筛纳米片ECNU-9具有规则的形状,而且分散性好。ECNU-9沿着c轴方向具有一套十元环和一套十二元环。在ECNU-9的晶化研究基础上,首次提出在球状胶束作用下,弯曲限制晶化的机理。加入有水合作用的无机盐后,导致离子液体团聚形成表面带正电荷的胶束,而SiO44-与GeO44-带负电荷,由于电荷平衡作用,SiO44-与GeO444-被吸引到胶束表面,沿胶束表面原位晶化,当弯曲的晶体厚度达到一定值时,外表面受到的张力限制晶体的进一步生长。第四部分考察了IM-20分子筛在不同酸性条件下后处理的结构变化。硅锗分子筛IM-20的拓扑结构为UWY,其骨架含有两类双四元环,本文利用ADoR机理,首次选择性脱除双四元环。在室温、强酸性水溶液下,对IM-20酸洗,可以获得两类双四元环均脱除的结构,记作ECNU-12.而在333 K、强酸性乙醇溶液下,可以获得只有一类双四元环脱除的结构,记作ECNU-13.采用DFT优化两种结构,并用优化的结构得到了与实验值接近的XRD谱图。
[Abstract]:In order to improve the diffusion limitation of molecular sieve to macromolecular reactants and macromolecular products, to improve the accessibility of catalytic active centers and to synthesize new molecular sieve materials, the interlaminar pore reaming of molecular sieve layered precursors was carried out successively. Study on the post-treatment and direct synthesis of silica-germanium molecular sieve nanoparticles. In the first part, organosilane Me2Si (OET) 2 (DEDMS) was used to intercalate the molecular sieve layered precursor Nu-6 (1) to obtain the novel structure of IEZ-Nu-6 (1) molecular sieve. By investigating the synthesis conditions, it was found for the first time that the ordered crystal material could be obtained in the ethanol solution, but the order degree was poor in the aqueous solution. Because Nu-6 (1) interlaminar template diffuses easily from interlayer to solution in water, the organic silane does not insert into the interlayer at this time, which leads to the failure of pore reaming, while in ethanol, the diffusion rate of template agent is slow, and the removal process of template agent is balanced with that of silicon intercalation process. Reaming is easy to succeed. The structure optimization and refinement of IEZ-Nu-6 (1) show that IEZ-Nu-6 (1) has two sets of 10-element annular channels with different pore sizes. Nu-6 (2) IEZ-Nu-6 (2) was used to catalyze the esterification of ethanol with acetic acid. The latter has higher conversion due to its larger pore size and hydrophilicity. In the second part, super porous molecular sieves were synthesized by using the structure of layered precursors. Up to now, molecular sieves synthesized by interlayer intercalation silicon have no more than 12 rings. In this paper, molecular sieve layered precursor PREFER and organosilane 1 / 3 / 5 / 7- tetramethylcyclotetrasilane (D 4 h) were used to fabricate the crystal material IEZ-FER (D 4 h) with tetrad ring in the middle of nitric acid solution. The structure was optimized and refined by DFT. The results show that IEZ-FER (D4h) has a set of 14-member rings and a set of 12-member ring channels. The physical and chemical properties of IEZ-FER (D4h) were characterized by means of XRD, UV-Ramaru NMR-IRN _ 2 adsorption, and the pore size, hydrophobicity and hydrothermal stability of the materials were characterized by steam adsorption. In the third part, using 1 Ding Ji-3-methyl imidazole salt as template, two silicon-germanium molecular sieve nanocrystals ECNU-9 with cell thickness were synthesized, which not only have high specific surface area, but also contain multilevel pore channels. The molecular sieve nanochip ECNU-9 has regular shape and good dispersibility. ECNU-9 has a set of 10-member ring and a set of 12-member ring along the c-axis direction. On the basis of the crystallization of ECNU-9, the mechanism of bending limiting crystallization under the action of spherical micelles is proposed for the first time. The addition of inorganic salts with water cooperation results in the aggregation of ionic liquids to form positively charged micelles on the surface, while SiO44- and GeO44- are negatively charged. Due to charge balance, SiO44- and GeO444- are attracted to the micelle surface and crystallized in situ along the micellar surface. When the thickness of the curved crystal reaches a certain value, the tension on the outer surface limits the further growth of the crystal. In the fourth part, the structure changes of IM-20 molecular sieve after treatment under different acidic conditions were investigated. The structure of SiGe molecular sieve IM-20 is UWY, and its skeleton contains two kinds of double quaternary rings. In this paper, the first selective removal of double quaternary rings is made by using the ADoR mechanism. At room temperature and in strong acidic aqueous solution, two kinds of double quaternary ring structures can be obtained for IM-20 acid pickling, which can be described as ECNU-12. However, at 333K, strong acid ethanol solution, only a class of double quaternary ring destructions can be obtained, which can be described as ECNU-13. The two structures were optimized by DFT, and the XRD spectra close to the experimental values were obtained by using the optimized structure.
【学位授予单位】：华东师范大学
【学位级别】：博士
【学位授予年份】：2015
【分类号】：TB383.1
本文编号：2129631
[Abstract]:In order to improve the diffusion limitation of molecular sieve to macromolecular reactants and macromolecular products, to improve the accessibility of catalytic active centers and to synthesize new molecular sieve materials, the interlaminar pore reaming of molecular sieve layered precursors was carried out successively. Study on the post-treatment and direct synthesis of silica-germanium molecular sieve nanoparticles. In the first part, organosilane Me2Si (OET) 2 (DEDMS) was used to intercalate the molecular sieve layered precursor Nu-6 (1) to obtain the novel structure of IEZ-Nu-6 (1) molecular sieve. By investigating the synthesis conditions, it was found for the first time that the ordered crystal material could be obtained in the ethanol solution, but the order degree was poor in the aqueous solution. Because Nu-6 (1) interlaminar template diffuses easily from interlayer to solution in water, the organic silane does not insert into the interlayer at this time, which leads to the failure of pore reaming, while in ethanol, the diffusion rate of template agent is slow, and the removal process of template agent is balanced with that of silicon intercalation process. Reaming is easy to succeed. The structure optimization and refinement of IEZ-Nu-6 (1) show that IEZ-Nu-6 (1) has two sets of 10-element annular channels with different pore sizes. Nu-6 (2) IEZ-Nu-6 (2) was used to catalyze the esterification of ethanol with acetic acid. The latter has higher conversion due to its larger pore size and hydrophilicity. In the second part, super porous molecular sieves were synthesized by using the structure of layered precursors. Up to now, molecular sieves synthesized by interlayer intercalation silicon have no more than 12 rings. In this paper, molecular sieve layered precursor PREFER and organosilane 1 / 3 / 5 / 7- tetramethylcyclotetrasilane (D 4 h) were used to fabricate the crystal material IEZ-FER (D 4 h) with tetrad ring in the middle of nitric acid solution. The structure was optimized and refined by DFT. The results show that IEZ-FER (D4h) has a set of 14-member rings and a set of 12-member ring channels. The physical and chemical properties of IEZ-FER (D4h) were characterized by means of XRD, UV-Ramaru NMR-IRN _ 2 adsorption, and the pore size, hydrophobicity and hydrothermal stability of the materials were characterized by steam adsorption. In the third part, using 1 Ding Ji-3-methyl imidazole salt as template, two silicon-germanium molecular sieve nanocrystals ECNU-9 with cell thickness were synthesized, which not only have high specific surface area, but also contain multilevel pore channels. The molecular sieve nanochip ECNU-9 has regular shape and good dispersibility. ECNU-9 has a set of 10-member ring and a set of 12-member ring along the c-axis direction. On the basis of the crystallization of ECNU-9, the mechanism of bending limiting crystallization under the action of spherical micelles is proposed for the first time. The addition of inorganic salts with water cooperation results in the aggregation of ionic liquids to form positively charged micelles on the surface, while SiO44- and GeO44- are negatively charged. Due to charge balance, SiO44- and GeO444- are attracted to the micelle surface and crystallized in situ along the micellar surface. When the thickness of the curved crystal reaches a certain value, the tension on the outer surface limits the further growth of the crystal. In the fourth part, the structure changes of IM-20 molecular sieve after treatment under different acidic conditions were investigated. The structure of SiGe molecular sieve IM-20 is UWY, and its skeleton contains two kinds of double quaternary rings. In this paper, the first selective removal of double quaternary rings is made by using the ADoR mechanism. At room temperature and in strong acidic aqueous solution, two kinds of double quaternary ring structures can be obtained for IM-20 acid pickling, which can be described as ECNU-12. However, at 333K, strong acid ethanol solution, only a class of double quaternary ring destructions can be obtained, which can be described as ECNU-13. The two structures were optimized by DFT, and the XRD spectra close to the experimental values were obtained by using the optimized structure.
【学位授予单位】：华东师范大学
【学位级别】：博士
【学位授予年份】：2015
【分类号】：TB383.1
【参考文献】
相关期刊论文 前1条
1 王一川;常见的分子筛──沸石的妙用[J];化学世界;1995年05期
，本文编号：2129631
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