Mesopore-Modified Zeolites: Preparation, Characterization, and Applications
Mesopore-Modified Zeolites: Preparation, Characterization, and Applications
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DOI：
10.1002/chin.200621223
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发表时间：
2006-05
期刊：
影响因子：
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通讯作者：
Y. Tao;H. Kanoh;L. Abrams;K. Kaneko
中科院分区：
文献类型：
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作者：
Y. Tao;H. Kanoh;L. Abrams;K. Kaneko
对环境友好和更有效的技术的需求增加了对多孔固体的使用和开发的兴趣。这些材料通常具有高表面积，这与其独特的表面化学性质相结合，提供了独特的反应和吸附选择性。沸石是多孔结晶固体，其孔具有分子尺寸，从而为客体分子提供尺寸和形状选择性。沸石由于其均匀、小孔径、高内表面积、柔性骨架和可控化学性质而广泛用于催化以及分离和纯化领域。1-12沸石的主要缺点是小尺寸的通道（小于0.8nm）和空腔（通常<1.5nm）对反应施加了扩散限制，这可能导致流动系统上的高背压。12-16已经反复证明，传质限制在使用沸石的工业应用中起重要作用。为了规避由沸石结构施加的扩散限制，已经探索了几种潜在的解决方案：·制备具有较大孔的沸石;·制备较小的沸石颗粒;·将较大孔插入沸石颗粒中。一些努力致力于开发具有较大孔（> 1.5nm）的沸石材料，1，2但孔径的增加是适度的。此外，这些新材料在与大尺寸分子的反应或石油裂化反应中不是非常有效。2.减小沸石颗粒尺寸已被用作减小晶内扩散路径长度的手段。20-33然而，正如Camblor等人所报道的，合成粒度低于100 nm的沸石由于不太完美的结晶而导致沸石体积的降低。34，35其他所需的性能也受到影响;例如，由于其胶体性质，较小沸石颗粒的过滤是困难的。对于小颗粒沸石，水热稳定性降低，并且在活化脱铝过程中发生结晶度的相当大的损失。合成高硅铝比的Y型分子筛可以弥补稳定性的下降，但活性降低。与沸石微孔的尺寸（< 2 nm）相比，中孔（2-50 nm）允许客体分子在主体框架中更快地迁移。由于反应物和产物在催化剂活性中心之间的快速传质是催化剂所必需的，因此在沸石颗粒中引入介孔的概念引起了人们的广泛关注。本文综述了近五年来发表的有关沸石中孔形成和表征的各种方法。本文综述了中孔沸石的实验条件和孔结构参数，并将其列于表1。制备含有介孔的规则结构的主要方法如下：
The demand for environmentally friendly and more efficient technology has enhanced interest in the use and development of porous solids. These materials typically have high surface areas, which, coupled with their unique surface chemistries, offer unique reaction and adsorption selectivities. Zeolites are porous crystalline solids whose pores are of molecular dimensions thereby providing size and shape selectivity for guest molecules. Zeolites are widely used in catalysis as well as in the separation and purification fields due to their uniform, small pore size, high internal surface area, flexible frameworks, and controlled chemistry. 1-12 The major drawback of zeolites is that the small size of the channels (less than∼ 0.8 nm) and cavities (typically< 1.5 nm) imposes diffusional limitations on reactions that can cause high back pressure on flow systems. 12-16 It has been repeatedly demonstrated that mass transfer limitations play an important role in industrial applications using zeolites. 17-19 To circumvent the diffusional limitation imposed by zeolitic structures, several potential solutions have been explored:• making zeolites with larger pores;• making smaller zeolite particles;• inserting larger pores into the zeolite particles. Some effort was devoted to the development of zeolite materials with larger pores (> 1.5 nm), 1, 2 but the increases in pore size were modest. Further, these new materials are not very effective in reactions with large-sized molecules or for petroleum cracking reactions. 2 The reduction of zeolite particle sizes has been employed as a means of reducing the intracrystalline diffusion path length. 20-33 However, as Camblor et al. reported, synthesizing zeolites with particle sizes below 100 nm caused a decrease in the micropore volume due to less perfect crystallization. 34, 35 Other desirable properties are also affected; for example, filtration of the smaller zeolite particles is difficult due to their colloidal properties. For small particle zeolites, hydrothermal stability is reduced and considerable loss of crystallinity occurs during the activation dealumination process. The reduction in stabilty can be countered by synthesizing zeolite Y with a higher Si/Al ratio, but the activity decreases. 36, 37Compared to the dimensions of the zeolite micropores (< 2 nm), mesopores (2-50 nm) permit faster migration of guest molecules in the host frameworks. Since fast mass transfer of the reactants and products to and from the active sites is required for catalysts, the concept of infusing mesopores into zeolite particles has attracted much attention. This review covers articles published within the past five years describing different methods of creating and characterizing mesopores in zeolitic particles. The experimental conditions and pore structural parameters of mesoporous zeolites discussed in this review are included in the Summary as Table 1. The main approaches toward making mesopore-containing regular structures are as follows: