Improvement of hydrothermal stability of an ordered mesoporous molecular sieve via multistage recrystallization

2007 ◽  
Vol 85 (5) ◽  
pp. 379-382 ◽  
Author(s):  
Yong M Luo ◽  
Zhao Y Hou ◽  
Rong T Li ◽  
Xiao M Zheng
Keyword(s):  
Mesoporous Materials ◽  
Molecular Sieves ◽  
Molecular Sieve ◽  
Mesoporous Molecular Sieve ◽  
Hydrothermal Stability ◽  
Hexagonal Symmetry ◽  
Stability Tests ◽  
Ordered Mesoporous ◽  
Mesoporous Aluminosilicate

A highly ordered mesoporous aluminosilicate molecular sieve, designated as MSAMS-4, has been synthesized via multistage recrystallization. Hydrothermal-stability tests revealed that MSAMS-4 has retained a well-ordered hexagonal-symmetry mesostructure both after treatment with 100 °C water for 120 h and after steaming at 800 °C for 6 h.Key words: aluminosilicates molecular sieves, mesoporous materials, multistage recrystallization, hydrothermal stability.

Characterization and investigation mechanism of hydrothermal stability for micropore-free ordered mesoporous molecular sieves

2012 ◽  
Vol 258 (22) ◽  
pp. 8895-8901 ◽  
Author(s):  
Hongping Pu ◽  
Caiyun Han ◽  
Hua Wang ◽  
Siwei Xu ◽  
Liuyi Zhang ◽  
...  
Keyword(s):  
Molecular Sieves ◽  
Hydrothermal Stability ◽  
Mesoporous Molecular Sieves ◽  
Ordered Mesoporous

Microwave Molecular Sieves Synthesis and Capillary Crystal Growth by Geometric Confinement.

2003 ◽  
Vol 782 ◽  
Author(s):  
Steven B. Ogunwumi ◽  
John F. Wight ◽  
James C. Fajardo
Keyword(s):  
Molecular Sieves ◽  
Molecular Sieve ◽  
Crystal Size ◽  
Mesoporous Molecular Sieve ◽  
Guest Molecules ◽  
Microwave Hydrothermal ◽  
Geometric Confinement ◽  
Capillary Bundle ◽  
And Control ◽  
Mcm 41

ABSTRACTMicrowave heating is an alternate means for material processing. The technique is promising for the accelerated synthesis of new materials. Microwave molecular sieves synthesis is combined with capillary confinement as a novel synthetic method. It is successfully demonstrated in the preparation of small ZSM-5 crystals by microwave hydrothermal synthesis within 1–1.7 μm channels of a capillary bundle. The geometric and spatial confinement offered by the capillary is expected to define and control the resulting crystal size distribution and orientation.MCM-41, a mesoporous molecular sieve with a uni-dimensional regular array of hexagonal channels is investigated as a candidate for capillary confinement. The large porous channels of MCM-41(>35 å ) is attractive as a host for promoting inclusions of guest molecules or templates. The successful confinement of MCM-41 represents an important step towards the alignment of molecular sieves in a defined orientation within thin capillaries bundled (less than 5 μm channels). Ultimately, such an approach may be useful for the fabrication of new molecular sieve devices.

Synthesis and Catalytic Applications of Novel Mesoporous Aluminosilicate Molecular Sieves

1996 ◽  
Vol 454 ◽  
Author(s):  
Kondam Madhusudan Reddy ◽  
Chunshan Song
Keyword(s):  
Molecular Sieves ◽  
Supported Catalysts ◽  
Metal Sulfide ◽  
Sodium Aluminate ◽  
Mesoporous Molecular Sieve ◽  
Mesoporous Molecular Sieves ◽  
Hydrogenation Catalysts ◽  
Mesoporous Aluminosilicate ◽  
Catalytic Applications ◽  
Mcm 41

ABSTRACTThis paper reports on the synthesis of four series of mesoporous aluminosilicate molecular sieves (Al-MCM-41) and their catalytic applications. Four different aluminum compounds were examined as Al source in the hydrothermal synthesis of the mesoporous aluminosilicates of MCM-41 type, including pseudo boehmite (alumina), aluminum sulfate, aluminum isopropoxide, and sodium aluminate. Each Al source was examined at three different feed Si/Al ratios in the synthesis. XRD results show that there are differences in the dioo-spacings for the samples prepared with different Al sources: sodium aluminate > Al isopropoxide > Al sulfate > pseudo boehmite. Such differences reveal that Al incorporation in the framework increases in the following order: pseudo boehmite < Al sulfate < Al isopropoxide < sodium aluminate. XRD also indicates that the synthesized Al-MCM-41 samples have different crystallinity. 27Al NMR and 29Si NMR reveal that most of the Al species in the samples prepared with pseudo boehmite were present in octahedral coordination, whereas in other samples nearly all the Al species are tetrahedral (in the framework). The acid characteristics of the synthesized molecular sieves were characterized by temperature-programmed desorption of n-butylamine, and by using 1,3,5-triisopropylbenzene hydrocracking as probe reaction. The results of TPD and probe reaction clearly indicate that the Al source used for synthesis has a major impact on the acidic and catalytic properties of Al-MCM-41. The samples prepared with Al isopropoxide and sodium aluminate are better as catalysts than those with Al sulfate and pseudo boehmite. We also explored the potential of mesoporous molecular sieves as support for noble metal hydrogenation catalysts and metal sulfide-based hydrotreating catalysts. Pd and Pt-loaded mesoporous molecular sieves were prepared and applied for hydrogenation of naphthalene and phenanthrene. The results show that mesoporous molecular sieve-supported catalysts are much more active than alumina- and titania-supported catalysts. The data for dibenzothiophene hydrodesulfurization suggest that Al-MCM-41 supported Co-Mo may be effective for deep desulfurization of distillate fuels.

Synthesis and Characterization of Large Pore Size and Highly Ordered Mesoporous Molecular Sieve SBA-15

2012 ◽  
Vol 554-556 ◽  
pp. 620-623
Author(s):  
Xiang Diao
Keyword(s):  
Electron Microscopy ◽  
Pore Size ◽  
Molecular Sieve ◽  
Triblock Copolymer ◽  
Mesoporous Molecular Sieve ◽  
Large Pore ◽  
Ordered Mesoporous ◽  
Poly Ethylene Oxide ◽  
Poly Ethylene ◽  
Large Pore Size

In this study, large pore size and highly ordered mesoporous molecular sieve SBA-15 was successfully synthesized in the acidic medium by using n-propanol as the pore-expanding agent, and tetraethyl orthosilicate (TEOS) as silicon source and poly(ethylene oxide)-block-poly(propylene oxide)-block-poly(ethylene oxide) triblock copolymer (P123 triblock copolymer) as a template agent. The samples were characterized by Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM) and Nitrogen Adsorption-Desorption. It is found that the particles of mesoporous molecular sieve SBA-15 have regular morphology and ordered pore structure, and also have high specific surface area, large pore size and pore volume.

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