具有Pm3n对称结构的超微孔氧化硅和硅铝材料的合成及其催化性能研究
发布时间：2018-09-14 17:55
【摘要】：超微孔材料(孔径大小为1-2 nnm)有望同时解决沸石分子筛孔道内扩散受限和引入介孔后择形性消失或减弱的问题。现有报道的超微孔材料绝大多数具有p6mm或者无序的结构,但三维结构(如Pm3n结构)的孔道内的扩散限制更小。Pm3n结构的孔道由笼状孔和连接“窗口”构成,这种特殊的结构有利于择形催化的发生。传统合成Pm3n结构氧化硅使用不可从市售获取的十六烷基三乙基溴化铵模板剂在强酸性条件下进行。本论文中使用短链模板剂合成Pm3n结构的氧化硅和硅铝材料,目的在于：1)得到孔径更小的(超微孔)材料；2)逐步解决模板剂不可从市售获取的问题；3)避免使用强酸,合成条件更绿色、环保,原料中铝源的利用率更高,主要包括以下结果：1、使用十二烷基三乙基溴化铵(DTEAB)模板剂合成得到了Pm3n结构的超微孔氧化硅和硅铝材料。当合成在弱碱性进行时,SO42-的Hofmeister salting-out阴离子效应有助于减小表面活性剂的堆积参数(g)；当合成在弱酸性条件下进行时,有机固体羧酸的亲疏水性决定了氧化硅的对称结构,其中丙二酸、丁二酸亲水性较好,可以有效降低表面活性剂的堆积参数,因而容易得到Pm3n结构氧化硅。超微孔硅铝材料在环己酮与季戊四醇的缩酮反应中表现出了高于分子筛催化剂的催化活性和较好的稳定性。2、使用市售的十二烷基三甲基溴化铵(C12TMAB)模板剂合成得到了Pm3n结构的超微孔氧化硅和硅铝材料。合成中使用了氨水为碱源(弱碱性合成条件),但需要少量H2SO4水解TEOS,并且利用SO42-的Hofineister salting-out阴离子效应使表面活性剂g参数减小以得到Pm3n结构的氧化硅。超微孔硅铝材料在环己酮与季戊四醇的缩酮反应中表现出了高活性和很好的稳定性；在邻苯二酚与叔丁醇的气相烷基化反应中具有最高的催化活性和目标产物4-叔丁基邻苯二酚(4-TBC)产率。3、为了进一步缩小材料的孔径,使用碳链更短的癸基三甲基溴化铵(C10TMAB)模板剂合成得到了Pm3n结构的超微孔氧化硅和硅铝材料。合成中使用了氨水为碱源(弱碱性合成条件),表面活性剂本身堆积参数较小,SO42-和NH4+的Hofmeister salting-out离子效应也促进了Pm3n结构的生成。在甲缩醛和三聚甲醛缩合制聚甲醛二甲醚(PODEW)的反应中,Pm3n结构的超微孔硅铝材料表现出了高催化活性和最高的目标产物PODE3-8的选择性,体现出了超微孔材料孔道内独特的择形催化。4、除了控制氧化硅的孔径之外,在合成体系中加入羧甲基纤维素钠(CMC)作分散剂还可以控制氧化硅的形貌、颗粒尺寸和粒径分布。在优化的条件下,可以合成得到Pm3n结构的单分散氧化硅纳米颗粒,氧化硅的初级孔尺寸在超微孔价孔的边界上,纳米颗粒尺寸小于100 nm,氧化硅的总孔容在1cm3·g-1以上。
[Abstract]:Ultrafine porous materials (pore size is 1-2 nnm) are expected to solve the problem of confined diffusion in zeolite channels and the disappearance or weakening of shape selectivity after introducing mesoporous materials. The traditional synthesis of Pm3n-structured silica is carried out using cetyltriethylammonium bromide templates which are not available for commercial use under strong acidic conditions. In this paper, short-chain templates were used to synthesize Pm3n-structured silica and silica-aluminium materials. The purpose is: 1) to obtain smaller pore size (ultra-micro porous) materials; 2) to gradually solve the template can not be obtained from the market; 3) to avoid the use of strong acid, synthesis conditions are greener, environmental protection, the utilization of aluminum sources in raw materials is higher, mainly including the following results: 1, the use of dodecyl triethyl ammonium bromide (DTEAB) template synthesis of Pm3n The anionic effect of SO42-Homeister salting-out helps to reduce the stacking parameters (g) of surfactants when synthesis proceeds in weak alkalinity; the hydrophobicity of organic solid carboxylic acids determines the symmetrical structure of silicon oxide, in which malonic acid, succinic acid Pm3n-structured silica is easily obtained because of its good hydrophilicity and can effectively reduce the stacking parameters of surfactants. Ultrafine porous silica-aluminium materials exhibit higher catalytic activity and better stability than zeolite catalysts in the ketal reaction of cyclohexanone with pentaerythritol. 2. The commercially available dodecyl trimethyl ammonium bromide (C12TMA) is used. Ultrafine porous silica and silica-aluminium materials with Pm_3n structure were synthesized by template synthesis. Ammonia water was used as alkaline source (weak alkaline synthesis condition), but a small amount of H2SO4 was needed to hydrolyze TEOS. The surfactant g parameters were reduced by using the anionic effect of SO42-Hoofineister salting-out to obtain Pm_3n-structured silica. The material exhibited high activity and good stability in the ketal reaction of cyclohexanone with pentaerythritol, and had the highest catalytic activity and yield of 4-tert-butyl catechol (4-TBC) in the vapor phase alkylation of catechol with tert-butanol. Ultrafine porous silica and silica-aluminium materials with Pm3n structure were synthesized by using C10TMAB as template. Ammonia water was used as alkaline source (weak alkaline synthesis condition). The surfactant accumulation parameters were small. The ionic effect of SO42 - and NH4 + on the formation of Pm3n structure was also promoted. The formation of Pm3n structure was also promoted by the ionic effect of Homeister salting-out. In the reaction of aldehyde condensation to polyoxymethylene ether (PODEW), Pm3n-structured ultra-micro-porous silica-aluminium materials exhibit high catalytic activity and the highest selectivity of the target product PODE3-8, reflecting the unique shape-selective catalysis in the pores of the ultra-micro-porous materials. 4. Besides controlling the pore size of silica, sodium carboxymethylcellulose (C-MC) was added into the synthesis system. MC) can also be used as dispersant to control the morphology, particle size and particle size distribution of silica. Under the optimized conditions, monodisperse silica nanoparticles with Pm3n structure can be synthesized. The primary pore size of silica is less than 100 nm at the boundary of the valence pore of the ultramicro-pore, and the total pore volume of silica is more than 1 cm 3.g-1.
【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】：O643.36;TB383.4
本文编号：2243444
[Abstract]:Ultrafine porous materials (pore size is 1-2 nnm) are expected to solve the problem of confined diffusion in zeolite channels and the disappearance or weakening of shape selectivity after introducing mesoporous materials. The traditional synthesis of Pm3n-structured silica is carried out using cetyltriethylammonium bromide templates which are not available for commercial use under strong acidic conditions. In this paper, short-chain templates were used to synthesize Pm3n-structured silica and silica-aluminium materials. The purpose is: 1) to obtain smaller pore size (ultra-micro porous) materials; 2) to gradually solve the template can not be obtained from the market; 3) to avoid the use of strong acid, synthesis conditions are greener, environmental protection, the utilization of aluminum sources in raw materials is higher, mainly including the following results: 1, the use of dodecyl triethyl ammonium bromide (DTEAB) template synthesis of Pm3n The anionic effect of SO42-Homeister salting-out helps to reduce the stacking parameters (g) of surfactants when synthesis proceeds in weak alkalinity; the hydrophobicity of organic solid carboxylic acids determines the symmetrical structure of silicon oxide, in which malonic acid, succinic acid Pm3n-structured silica is easily obtained because of its good hydrophilicity and can effectively reduce the stacking parameters of surfactants. Ultrafine porous silica-aluminium materials exhibit higher catalytic activity and better stability than zeolite catalysts in the ketal reaction of cyclohexanone with pentaerythritol. 2. The commercially available dodecyl trimethyl ammonium bromide (C12TMA) is used. Ultrafine porous silica and silica-aluminium materials with Pm_3n structure were synthesized by template synthesis. Ammonia water was used as alkaline source (weak alkaline synthesis condition), but a small amount of H2SO4 was needed to hydrolyze TEOS. The surfactant g parameters were reduced by using the anionic effect of SO42-Hoofineister salting-out to obtain Pm_3n-structured silica. The material exhibited high activity and good stability in the ketal reaction of cyclohexanone with pentaerythritol, and had the highest catalytic activity and yield of 4-tert-butyl catechol (4-TBC) in the vapor phase alkylation of catechol with tert-butanol. Ultrafine porous silica and silica-aluminium materials with Pm3n structure were synthesized by using C10TMAB as template. Ammonia water was used as alkaline source (weak alkaline synthesis condition). The surfactant accumulation parameters were small. The ionic effect of SO42 - and NH4 + on the formation of Pm3n structure was also promoted. The formation of Pm3n structure was also promoted by the ionic effect of Homeister salting-out. In the reaction of aldehyde condensation to polyoxymethylene ether (PODEW), Pm3n-structured ultra-micro-porous silica-aluminium materials exhibit high catalytic activity and the highest selectivity of the target product PODE3-8, reflecting the unique shape-selective catalysis in the pores of the ultra-micro-porous materials. 4. Besides controlling the pore size of silica, sodium carboxymethylcellulose (C-MC) was added into the synthesis system. MC) can also be used as dispersant to control the morphology, particle size and particle size distribution of silica. Under the optimized conditions, monodisperse silica nanoparticles with Pm3n structure can be synthesized. The primary pore size of silica is less than 100 nm at the boundary of the valence pore of the ultramicro-pore, and the total pore volume of silica is more than 1 cm 3.g-1.
【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】：O643.36;TB383.4
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