SBA-15介孔分子筛及其主-客体复合材料研究的某些进展

对分子筛的发展历程、SBA-15介孔分子筛的合成方法、近年来以SBA-15介孔分子筛作主体合成主-客体复合材料的研究情况、SBA-15分子筛及其复合材料的应用进行了综述,并对SBA-15介孔分子筛在未来的发展进行了展望.     

介孔分子筛SBA-15的研究进展

介孔分子筛SBA-15具有独特的物理化学性质和广阔的应用前景,成为众多研究领域的一个研究热点。本文介绍了介孔分子筛SBA-15的特点、制备方法及主要用途。简述了近年来SBA-15的研究进展。本文最后对SBA-15在可控合成、改性以及复合过程中的可能应用进行了展望与总结。     

Al-SBA-15介孔分子筛的制备及应用进展

介孔分子筛SBA-15通过化学改性,可将一些官能团引入到其骨架中改善催化性能,其中以铝改性效果最好,铝改性后的SBA-15介孔分子筛的水热稳定性及酸性明显提高。介绍了Al-SBA-15介孔分子筛的合成及应用现状,展望了介孔分子筛Al-SBA-15未来的发展方向。     

AI-SBA-15介孔分子筛的制备及应用进展

介孔分子筛SBA-15通过化学改性,可将一些官能团引入到其骨架中改善催化性能,其中以铝改性效果最好,铝改性后的SBA-15介孔分子筛的水热稳定性及酸性明显提高。介绍了A1-SBA-15介孔分子筛的合成及应用现状,展望了介孔分子筛A1-SBA-15未来的发展方向。     

钛硅有序介孔分子筛合成及应用研究进展

基于国内外固体催化剂的研究成果,主要研究钛硅有序介孔分子筛催化材料。首先介绍了钛硅有序介孔分子筛材料的合成机理,然后综述了Ti-MCM-41、Ti-SBA-15两类重要的有序介孔分子筛合成及其在光催化、环氧反应以及其它方面的应用研究,最后结合现状对钛硅有序介孔分子筛材料的发展进行了展望。     

介孔分子筛合成及应用的研究进展

本文综述了介孔分子筛的研究现状,重点阐述了介孔分子筛的合成与应用,介孔分子筛的合成方法主要有水热晶化法、微波辐射合成法、溶胶凝胶法、室温合成法、干粉制备法和极浓体系合成法,在纳米材料、环保和催化领域应用前景广阔。     

介孔氧化铝的合成及应用

通过对介孔氧化硅合成工艺的优化与修正可以用来制备介孔氧化铝分子筛。在合成介孔分子筛的前驱物中掺杂其他金属元素而将其引入骨架或将活性组分负载到介孔分子筛的基体上,可以实现对介孔分子筛表面进行表面修饰与改性,以调变分子筛表面的酸催化性能。本文综述了介孔氧化铝合成、改性研究的历史与现状,及在酸催化过程中的应用。     

合成条件对SBA-15介孔分子筛晶体结构及水热稳定性影响

以X射线衍射(XRD)为表征手段,研究了SBA-15介孔分子筛合成过程中酸类型、加料顺序和搅拌时间对介孔分子筛晶体结构的影响,结果表明:不同酸合成的SBA-15介孔分子筛的结晶度顺序为高氯酸盐酸硫酸氢氟酸。同时研究了焙烧法和溶剂萃取法去除模板剂对SBA-15介孔分子筛水热稳定性的影响,结果表明:焙烧法去除模板剂后得到的分子筛的水热稳定性更高。     

介孔分子筛SBA-15在催化领域的应用进展

从负载固体酸催化剂、金属和金属氧化物以及手性催化剂三方面综述了介孔分子筛SBA-15在催化领域应用的研究进展;并展望了介孔分子筛SBA-15在催化领域的研究方向。     

具有微-介孔的分子筛复合材料的研究现状

分子筛是一种特定空间结构的催化剂,根据孔结构大小可以分为微孔分子筛和介孔分子筛,微孔分子筛侧重介绍了Y型分子筛、β型分子筛和ZSM-5分子筛,介孔分子筛侧重介绍了MCM分子筛和SBA分子筛,由于微孔和介孔分子筛都存在缺点,所以将二种孔结构的材料复合,制备新型催化剂将是未来发展趋势。     

An overview of ordered mesoporous material SBA-15: synthesis,functionalization and application in oxidation reactions

Ordered mesoporous materials are attracting wide concern because of their applications in the field of catalysis, adsorption, separations, drug delivery systems and gas sensors owing of their extremely high surface area combined with well-defined pore structures with narrow pore size distributions. Various mesoporous materials such as MCM-41, MCM-48, SBA-15 and SBA-16 have been reported in past two decades. Synthesis of mesoporous materials involves the concept of aggregation of surfactants as structure directing agents under acidic or basic conditions. The dimensions of these mesopores can be obtained by type of surfactant, auxiliary chemicals and synthesis conditions. At present, SBA-15 has attracted more attention among different mesoporous silica structures due to their desirable properties such as thick pore wall and hexagonal mesopores (4–12 nm), high surface area, ease of synthesis and functionalization and high thermal and mechanical stability. In last few years, great effort has been made on the development of various methods for the synthesis of mesoporous materials as support for oxidation reactions. The aim of this review article is to focus mainly on mesoporous SBA-15 together with its application as support for various oxidation reactions.     

Facile synthesis route to monodispersed platelet-like SBA-15 silica

We here report a facile synthesis route to monodispersed platelet-like SBA-15 mesoporous silica employing kinetically controlled micelles as templates. In previous preparations of SBA-15 silica, it was believed that thermodynamically equilibrated micelles were used as templates. The kinetically controlled micelle has never been used before to generate periodic mesoporous materials with unique morphology. Monodispersed hexagonal platelet-like SBA-15 microparticles were prepared via a very facile synthesis route by tuning the micelle formation process, i.e. the stirring rate and the time of dissolution of the triblock copolymer and formation of the micelles. Shorter micelle formation time and faster stirring are essential to generate platelet-like SBA-15 silica particles. It is expected to apply in the synthesis of a wide variety of mesophase materials.     

Synthesis,analysis and characterization of ordered mesoporous TiO2/SBA-15 matrix: Effect of calcination temperature

Mesoporous TiO₂/SBA-15 matrix was prepared by the sol–gel synthesis of TiO₂ in previously prepared SBA-15 particles. Nonionic surfactant was used as liquid template and Na₂SiO₄ as SiO₂ precursor for the synthesis of mesoporous silica SBA-15 with high specific surface area. Different calcination temperature was used for the synthesis and analysis of TiO₂/SBA-15 matrix. The synthesized titania/silica composites were characterized by X-ray diffraction, FTIR, TEM, UV–vis spectroscopy, etc. TEM micrographs showed titania is successfully embedded in SBA-15 channel. Different calcination temperature indicates different size of particle formation and different photocatalytic properties. The activity test indicated that TiO₂/SBA-15 composite prepared by this method had better photocatalytic performance than pure TiO₂. The preparation method and the textural characteristics of mesoporous materials have great influence for the photocatalytic activity.     

Trypsin immobilization on mesoporous silica with or without thiol functionalization

The effects of pore size, structure, and surface functionalization of mesoporous silica on the catalytic activity of the supported enzyme, trypsin, were investigated. For this purpose, SBA-15 with 1-dimensional pore arrangement and cubic Ia3d mesoporous silica with 3-dimensional pores were prepared and tested as a support. Materials with varying pore diameters in the range 5–10 nm were synthesized using a non-ionic block copolymer by controlling the synthesis temperature. Thiol-group was introduced to the porous materials via siloxypropane tethering either by post synthesis grafting or by direct synthesis. These materials were characterized using XRD, SEM, TEM, N₂ adsorption, and elemental analysis. Trypsin-supported on the solids prepared was active and stable for hydrolysis of N-α-benzoyl-DL-arginine-4-nitroanilide (BAPNA). Without applying thiol-functionalization, cubic Ia3d mesoporous silica with ca. 5.4 nm average pore diameter was found to be superior to SBA-15 for trypsin immobilization and showed a better catalytic performance. However, enzyme immobilized on the 5% thiol-functionalized SBA-15 prepared by directly synthesis was found to be the most promising and was also found recyclable.     

Synthesis of hexagonal and cubic mesoporous silica using power plant bottom ash

An alkali fusion method was adopted to extract silicate species from coal bottom ash in a power plant and the supernatant solution was used for the synthesis of MCM-41, SBA-15, and SBA-16 mesoporous silica materials. The minor impurities present in the bottom ash were not found to be detrimental to the successful formation of mesoporous silica phases. Additional silica from sodium metasilicate was introduced to improve the textural properties for SBA-15 and SBA-16. According to SEM analyses, particle morphology of the samples gradually approaches those prepared using pure chemical as the amount of external silica source increases. XRD analyses confirmed well-ordered mesostructures in all of these silica materials. N₂ adsorption–desorption isotherms of MCM-41 prepared using bottom ash showed a type IV isotherm with a region of steep increase due to capillary condensation, whilst SBA-15 and SBA-16 showed type IV isotherm with H1 and H2 hysteresis loops, respectively. ²⁷Al MAS NMR analysis of MCM-41 synthesized from the supernatant solution reveals that the extracted Al species from bottom ash were tetrahedrally incorporated in the framework. TEM clearly showed the uniform pore structure of the materials prepared using the industrial waste.     

Trypsin immobilization on mesoporous silica with or without thiol functionalization

The effects of pore size, structure, and surface functionalization of mesoporous silica on the catalytic activity of the supported enzyme, trypsin, were investigated. For this purpose, SBA-15 with 1-dimensional pore arrangement and cubic Ia3d mesoporous silica with 3-dimensional pores were prepared and tested as a support. Materials with varying pore diameters in the range 5–10 nm were synthesized using a non-ionic block copolymer by controlling the synthesis temperature. Thiol-group was introduced to the porous materials via siloxypropane tethering either by post synthesis grafting or by direct synthesis. These materials were characterized using XRD, SEM, TEM, N₂ adsorption, and elemental analysis. Trypsin-supported on the solids prepared was active and stable for hydrolysis of N-α-benzoyl-DL-arginine-4-nitroanilide (BAPNA). Without applying thiol-functionalization, cubic Ia3d mesoporous silica with ca. 5.4 nm average pore diameter was found to be superior to SBA-15 for trypsin immobilization and showed a better catalytic performance. However, enzyme immobilized on the 5% thiol-functionalized SBA-15 prepared by directly synthesis was found to be the most promising and was also found recyclable.     

Flash induction calcination: A powerful tool for total template removal and fine tuning of the hydrophobic/hydrophilic balance in SBA-15 type silica mesoporous materials

A new rapid calcination method has been used to completely remove the organic template from SBA-15 ordered mesoporous silica, and to preserve a high number of silanol in these materials. This calcination method provided by an induction furnace was found to considerably reduce the calcination time and therefore the energy consumption associated. Moreover, adjustment of both calcination temperature and duration allowed tuning the hydrophobic/hydrophilic balance of the mesoporous SBA-15 silica materials. For comparison, short and long time conventional muffle furnace calcination was performed. The induction calcination was also successfully applied to different type of mesoporous silica materials such as SBA-16 and MCM-41.     

Synthesis of mesoporous materials SBA-15 and CMK-3 from fly ash and their application for CO2 adsorption

A supernatant solution of silicate species extracted from coal fly ash in a power plant by alkali fusion was used in acidic condition to prepare a mesoporous silica SBA-15. The SBA-15 was used as a template for the synthesis of a mesoporous carbon CMK-3 using sucrose as a carbon source. Characterization of the produced mesoporous materials by XRD, N₂ adsorption-desorption, SEM, and TEM confirmed the formation of well-ordered hexagonal mesostructures. Textural properties were found close to those prepared by pure chemicals. SBA-15 after polyethyleneimine impregnation and CMK-3 were tested for carbon dioxide adsorption, successfully demonstrating the possibility of recycling the industrial waste product in a power plant into a useful adsorbent.     

Morphological control of mesoporous silica SBA-15 synthesized at low temperature without additives

Fiber-like or rod-like mesoporous SBA-15 silicas with different lengths and diameter of macrostructures and pore diameter could be synthesized by the self-assembly of silica-surfactant (commonly used Pluronic P123 (EO₂₀-PO₇₀EO₂₀) as a structure-directing agent) through careful control of the synthetic temperature and stirring time without any additives. X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM), and nitrogen adsorption–desorption isotherms are used to characterize these mesoporous silica materials. Compared with those reports on conventional SBA-15, our work is focused on one-step synthesis and the morphological control of ordered mesoporous silica synthesized at low temperature under low concentration of P123 (0.67 wt%) without the addition of inorganic salts, where pre-hydrolyzed silica species may favor the self-assembly of silica-polymer hybrid micelles. Moreover, the pore diameter of fiber-like SBA-15 synthesized at 40 °C is slightly smaller than that of conventional SBA-15, revealing that the average micellar radius of P123 micelles in this low concentration of P123 solution was almost same as that for the conventional synthesis of SBA-15.     

Simultaneous control of rod length and pore diameter of SBA-15 for PPL loading

Mesoporous silica materials are attractive materials for immobilizing enzymes because of their well-ordered structures, large surface area are pore volume. Diffusion of large enzyme molecules such as porcine pancreatic lipase (PPL) through the lengthy channels of MPS takes place too slowly. Therefore, the squat of the enzyme at the pore mouth entrance, actually makes the rest of the channel useless. In this study, to overcome this problem, synthesis parameters of SBA-15 were changed, since along with pore diameter increasing, the mesochannel length becomes shorter. The main point to obtain a well-ordered 2D hexagonal pore structure was the pre-hydrolysis of tetraethyl orthosilicate (TEOS) before the addition of 1,3,5-trimethyl benzene as a micelle swelling agent. Due to the strong effect of zirconium in changing the morphology of SBA-15 particles, we modified SBA-15 in the presence of a small amount of ZrOCl₂ in the synthesis solution under acidic conditions. As a result, mesochannel length of SBA-15-Zr was shortened from 600 to <200 nm. The morphology of mesoporous silica was also changed from rod-like to platelet, because of the accelerating effect of Zr(IV) on the self-assembly rate of P123 and TEOS condensation. Characteristic results conducted by low angle XRD, high resolution transmission electron microscopy and nitrogen adsorption, confirmed tuning effect of Zr(IV) in SBA-15. Furthermore, it was shown that the number of pore entrances increases with decreasing the length of SBA-15 mesochannels, leading to obvious improvement of enzyme uptake. PPL has been successfully immobilized in the mesoporous channels of SBA-15-Zr. The total amount of lipase adsorbed on the mesoporous SBA-15-Zr was measured by thermal gravimetric analysis. The largest PPL adsorption capacity was 784 mg/g belonging to the SBA-15-Zr with the length of 150 nm and the mean pore size diameter of 9.22 nm.