The Experts below are selected from a list of 249 Experts worldwide ranked by ideXlab platform
Suk Bong Hong - One of the best experts on this subject based on the ideXlab platform.
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Crystallization Mechanism of Zeolite UZM‑5
2015Co-Authors: Min Bum Park, Christopher P. Nicholas, Gregory J. Lewis, Nak Ho Ahn, Robert W. Broach, Suk Bong HongAbstract:A reliable formation pathway for UZM-5 zeolite crystals in the presence of tetraethylammonium, Tetramethylammonium, and Na+ ions at 150 °C has been proposed based on the 13C MAS NMR and IR spectra of a series of solid products recovered as a function of time during the crystallization process, as well as on the crystal structure of as-made UZM-5 determined using synchrotron powder X-ray diffraction and Rietveld analyses. The nucleation of this cage-based small-pore zeolite begins with the construction of the largest 26-hedral lta-cages among its four different structural units. The next step is the attachment of 14-hedral wbc-cages to the preorganized lta-cage at shared 6-rings in an appropriate orientation that will allow the growth of two wbc-cage layers linked by 8-hedral rth-cage formation along both a and b axes. The resulting interlayer space is readily converted to a layer of lta-cages by interconnecting two opposing wbc-cages, with the concomitant formation of interlayer d4r-cages and 8-rings. Over the outer surface of the resulting UZM-5 nuclei, which resembles one-half of an lta-cage, the crystal growth may take place in a self-assembled manner as described above
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Zeolite Synthesis from a Charge Density Perspective: The Charge Density Mismatch Synthesis of UZM-5 and UZM-9
Chemistry of Materials, 2014Co-Authors: Min Bum Park, Him Chan Jeon, Christopher P. Nicholas, Gregory J. Lewis, Suk Bong HongAbstract:A charge density model of aluminosilicate zeolite synthesis is presented. This model has been applied to the charge density mismatch (CDM) synthesis of UZM-5 and UZM-9 zeolites at 150 and 100 °C, respectively, using the same synthesis mixture that includes tetraethylammonium (TEA+), Tetramethylammonium (TMA+), and Na+ ions as structure-directing agents (SDAs). It allows a seamless description of the contributions of both the hydroxide and SDA components of the CDM barrier to zeolite synthesis. The syntheses are described as temperature-driven confrontations with the CDM barrier, resulting in disproportionation to solution and solid products with diverging charge densities. The presence of the CDM barrier and this tunable disproportionation in charge density, along with the suitable choice of SDA concentrations, allows a flexible and cooperative participation of SDAs, as the synthesis medium initially forms aluminosilicate networks that maximize Coulombic stabilization under the conditions at hand. The UZM...
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zeolite synthesis in the tetraethylammonium Tetramethylammonium mixed organic additive system
Microporous and Mesoporous Materials, 2009Co-Authors: Seok Han Kim, Min Bum Park, Hyungki Min, Suk Bong HongAbstract:Abstract The synthesis of zeolites UZM-5, UZM-9, and offretite in the tetraethylammonium–Tetramethylammonium two-organic component system, with or without some monovalent inorganic ions present, and their characterization results are described. The phase selectivity of the crystallization was found to differ notably according not only to the synthesis temperature, but also to the type of inorganic cations replacing half of Tetramethylammonium ions in the synthesis mixture. A combination of elemental analysis and 13 C MAS NMR measurements allows us to reasonably estimate the intrazeolitic locations and populations of the two organic additives encapsulated within as-made UZM-5 and UZM-9, as well as within as-made offretite, which are further altered by the presence of additional inorganic cations. When a small amount of Na + ions is used as a supplementary crystallization agent in UZM-9 synthesis, unexpectedly, it is observed that the average size of crystals obtained increases continuously with increasing the autoclave rotation speed up to 150 rpm at the crystallization temperature.
Zhongmin Liu - One of the best experts on this subject based on the ideXlab platform.
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synthesis of ti mcm 41 using colloidal silica and titanium trichloride i synthesis of ti mcm 41 molecular sieve
2001Co-Authors: Q Xin, Zhongmin LiuAbstract:silicon source and using TiCl3 solution as titanium source. Among the used auxiliary templates, Tetramethylammonium hydroxide (TMAOH) and tetraethylammonium hydroxide (TEAOH) were found to be the most effective ones to improve the long-range order. Titanium content (molar fraction) in the Ti-MCM-41 can be up to 3.75% which is higher than that in Ti-MCM-41 synthesized from organic precursors.
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ti mcm 41 synthesized from colloidal silica and titanium trichloride synthesis characterization and catalysis
Chemistry of Materials, 2001Co-Authors: Zhaochi Feng, Q Xin, Zhongmin LiuAbstract:Titanium-containing mesoporous molecular sieve Ti−MCM-41 has been synthesized using colloidal silica as the silicon source and TiCl3 solution as the titanium source and was characterized by X-ray diffraction, N2 adsorption, UV−vis, and UV−Raman spectroscopies. The formation of anatase TiO2 can be avoided during the synthesis and the crystallization of the molecular sieve because of the relatively low hydrolysis rate of an inorganic TiCl3 solution. The characterization results confirm that most Ti4+ ions are isolated and tetrahedrally coordinated in the framework of MCM-41. Different auxiliary templates, Tetramethylammonium hydroxide (TMAOH), tetraethylammonium hydroxide (TEAOH), tetrabutylammonium hydroxide, and NH3·H2O were used to synthesize the Ti−MCM-41 molecular sieve. Among them, TMAOH and TEAOH were found to be the most effective auxiliary templates to improve the long-ranged order of the molecular sieves.
Min Bum Park - One of the best experts on this subject based on the ideXlab platform.
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Crystallization Mechanism of Zeolite UZM‑5
2015Co-Authors: Min Bum Park, Christopher P. Nicholas, Gregory J. Lewis, Nak Ho Ahn, Robert W. Broach, Suk Bong HongAbstract:A reliable formation pathway for UZM-5 zeolite crystals in the presence of tetraethylammonium, Tetramethylammonium, and Na+ ions at 150 °C has been proposed based on the 13C MAS NMR and IR spectra of a series of solid products recovered as a function of time during the crystallization process, as well as on the crystal structure of as-made UZM-5 determined using synchrotron powder X-ray diffraction and Rietveld analyses. The nucleation of this cage-based small-pore zeolite begins with the construction of the largest 26-hedral lta-cages among its four different structural units. The next step is the attachment of 14-hedral wbc-cages to the preorganized lta-cage at shared 6-rings in an appropriate orientation that will allow the growth of two wbc-cage layers linked by 8-hedral rth-cage formation along both a and b axes. The resulting interlayer space is readily converted to a layer of lta-cages by interconnecting two opposing wbc-cages, with the concomitant formation of interlayer d4r-cages and 8-rings. Over the outer surface of the resulting UZM-5 nuclei, which resembles one-half of an lta-cage, the crystal growth may take place in a self-assembled manner as described above
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Zeolite Synthesis from a Charge Density Perspective: The Charge Density Mismatch Synthesis of UZM-5 and UZM-9
Chemistry of Materials, 2014Co-Authors: Min Bum Park, Him Chan Jeon, Christopher P. Nicholas, Gregory J. Lewis, Suk Bong HongAbstract:A charge density model of aluminosilicate zeolite synthesis is presented. This model has been applied to the charge density mismatch (CDM) synthesis of UZM-5 and UZM-9 zeolites at 150 and 100 °C, respectively, using the same synthesis mixture that includes tetraethylammonium (TEA+), Tetramethylammonium (TMA+), and Na+ ions as structure-directing agents (SDAs). It allows a seamless description of the contributions of both the hydroxide and SDA components of the CDM barrier to zeolite synthesis. The syntheses are described as temperature-driven confrontations with the CDM barrier, resulting in disproportionation to solution and solid products with diverging charge densities. The presence of the CDM barrier and this tunable disproportionation in charge density, along with the suitable choice of SDA concentrations, allows a flexible and cooperative participation of SDAs, as the synthesis medium initially forms aluminosilicate networks that maximize Coulombic stabilization under the conditions at hand. The UZM...
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zeolite synthesis in the tetraethylammonium Tetramethylammonium mixed organic additive system
Microporous and Mesoporous Materials, 2009Co-Authors: Seok Han Kim, Min Bum Park, Hyungki Min, Suk Bong HongAbstract:Abstract The synthesis of zeolites UZM-5, UZM-9, and offretite in the tetraethylammonium–Tetramethylammonium two-organic component system, with or without some monovalent inorganic ions present, and their characterization results are described. The phase selectivity of the crystallization was found to differ notably according not only to the synthesis temperature, but also to the type of inorganic cations replacing half of Tetramethylammonium ions in the synthesis mixture. A combination of elemental analysis and 13 C MAS NMR measurements allows us to reasonably estimate the intrazeolitic locations and populations of the two organic additives encapsulated within as-made UZM-5 and UZM-9, as well as within as-made offretite, which are further altered by the presence of additional inorganic cations. When a small amount of Na + ions is used as a supplementary crystallization agent in UZM-9 synthesis, unexpectedly, it is observed that the average size of crystals obtained increases continuously with increasing the autoclave rotation speed up to 150 rpm at the crystallization temperature.
Chen Biaohua - One of the best experts on this subject based on the ideXlab platform.
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Synthesis of UZM-5 Zeolite by a Hydrothermal Method Using Tetraethylammonium Hydroxide-Tetramethylammonium Chloride as Organic Templates
Chinese Journal of Catalysis, 2010Co-Authors: Chen BiaohuaAbstract:The synthesis of UZM-5 zeolite by the hydrothermal method in the tetraethylammonium hydroxide(TEAOH)-Tetramethylammonium chloride(TMACl) two-organic component system was studied.The products were characterized using X-ray diffraction,infrared spectroscopy,and thermogravimetry.The crystallization process and growth of UZM-5 zeolite were investigated.The results indicated that the UZM-5 zeolite could be synthesized when the initial mixture was SiO2:(0.16-0.5)Al2O3:(0.4-1.0)TEAOH:(0.06-0.13)TMACl:20H2O.Too high temperature was disadvantageous to the crystallization process.UZM-5 zeolite could be synthesized in the temperature range of 403-423 K.Too long time led to the crystallization of sodalite zeolite.The synthesis of UZM-5 zeolite with silica sol needs 2 days,while silicic acid 4 days and silica gel 5 days.A small amount of Na+ ions resulted in the crystallization of UZM-9 zeolite and had an effect on the phase selectivity.
Q Xin - One of the best experts on this subject based on the ideXlab platform.
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synthesis of ti mcm 41 using colloidal silica and titanium trichloride i synthesis of ti mcm 41 molecular sieve
2001Co-Authors: Q Xin, Zhongmin LiuAbstract:silicon source and using TiCl3 solution as titanium source. Among the used auxiliary templates, Tetramethylammonium hydroxide (TMAOH) and tetraethylammonium hydroxide (TEAOH) were found to be the most effective ones to improve the long-range order. Titanium content (molar fraction) in the Ti-MCM-41 can be up to 3.75% which is higher than that in Ti-MCM-41 synthesized from organic precursors.
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ti mcm 41 synthesized from colloidal silica and titanium trichloride synthesis characterization and catalysis
Chemistry of Materials, 2001Co-Authors: Zhaochi Feng, Q Xin, Zhongmin LiuAbstract:Titanium-containing mesoporous molecular sieve Ti−MCM-41 has been synthesized using colloidal silica as the silicon source and TiCl3 solution as the titanium source and was characterized by X-ray diffraction, N2 adsorption, UV−vis, and UV−Raman spectroscopies. The formation of anatase TiO2 can be avoided during the synthesis and the crystallization of the molecular sieve because of the relatively low hydrolysis rate of an inorganic TiCl3 solution. The characterization results confirm that most Ti4+ ions are isolated and tetrahedrally coordinated in the framework of MCM-41. Different auxiliary templates, Tetramethylammonium hydroxide (TMAOH), tetraethylammonium hydroxide (TEAOH), tetrabutylammonium hydroxide, and NH3·H2O were used to synthesize the Ti−MCM-41 molecular sieve. Among them, TMAOH and TEAOH were found to be the most effective auxiliary templates to improve the long-ranged order of the molecular sieves.
