Center for Ordered Nanoporous Materials Synthesis

Pohang, South Korea

Center for Ordered Nanoporous Materials Synthesis

Pohang, South Korea
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Shin J.,Center for Ordered Nanoporous Materials Synthesis | Ahn N.H.,Center for Ordered Nanoporous Materials Synthesis | Cho S.J.,Chonnam National University | Ren L.,Zhejiang University | And 2 more authors.
Chemical Communications | Year: 2014

Rietveld analyses of the synchrotron X-ray diffraction data for various cation forms of zeolite ECR-1 have demonstrated framework Al zoning, which parallels the alternation of Al-rich maz and Al-poor mor layers. This can be further supported by notable differences in the average bond valence of its 10 crystallographically distinct tetrahedral sites. © 2014 The Royal Society of Chemistry.


Shin J.,Center for Ordered Nanoporous Materials Synthesis | Ahn N.H.,Center for Ordered Nanoporous Materials Synthesis | Camblor M.A.,CSIC - Institute of Materials Science | Cho S.J.,Chonnam National University | Hong S.B.,Center for Ordered Nanoporous Materials Synthesis
Angewandte Chemie - International Edition | Year: 2014

The transformation from a disordered into an ordered version of the zeolite natrolite occurs on prolonged heating of this material in the crystallizing medium, but not if the mother liquor is replaced by water or an alkaline solution. This process occurs for both aluminosilicate and gallosilicate analogues of natrolite. In cross experiments, the disordered Al-containing (or Ga-containing) analogue is heated while in contact with the mother liquor of the opposite analogue, that is, the Ga-containing (or Al-containing) liquor. Therefore, strong evidence for the mechanism of the ordering process was obtained, which was thus proposed to proceed by intraframework migration of tetrahedral atoms without diffusion along the pores. Migration is first triggered, then fuelled by surface rearrangement through reactions with the mother liquor, and stops when an almost fully ordered state is attained. Classical dissolution-recrystallization and Ostwald ripening processes do not appear to be relevant for this phase transformation. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.


Park M.B.,Center for Ordered Nanoporous Materials Synthesis | Jo D.,Center for Ordered Nanoporous Materials Synthesis | Jeon H.C.,Center for Ordered Nanoporous Materials Synthesis | Nicholas C.P.,UOP LLC | And 2 more authors.
Chemistry of Materials | Year: 2014

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-5 synthesis at 150 °C is characterized by much higher fractional Si and Al yields (0.85 Si and 0.94 Al vs 0.30 Si and 0.70 Al) and a higher Si/Al ratio (ca. 7 vs 3) compared to UZM-9 synthesis at 100 °C. Unlike the latter case, TEA+ plays an important role in the nucleation of UZM-5. However, TMA+ was found to be essential for the nucleation of both zeolites. While Na+ is required to crystallize UZM-9, the nucleation rate of UZM-5 is about twice as fast in the absence of Na+. On the other hand, the crystal growth rate of this small-pore zeolite is over 10 times faster with Na+ present, giving a considerably larger crystallite size. © 2014 American Chemical Society.


Park M.B.,Center for Ordered Nanoporous Materials Synthesis | Park M.B.,ETH Zurich | Ahn N.H.,Center for Ordered Nanoporous Materials Synthesis | Broach R.W.,UOP LLC | And 3 more authors.
Chemistry of Materials | Year: 2015

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. © 2015 American Chemical Society.


Shin J.,Center for Ordered Nanoporous Materials Synthesis | Ahn N.H.,Center for Ordered Nanoporous Materials Synthesis | Camblor M.A.,CSIC - Institute of Materials Science | Zicovich-Wilson C.M.,Autonomous University of the State of Morelos | Hong S.B.,Center for Ordered Nanoporous Materials Synthesis
Chemistry of Materials | Year: 2014

A study was conducted to demonstrate the synthesis of aluminosilicate natrolites and control of their tetrahedral atom ordering. A robust method was developed to synthesize the aluminosilicate version (Al-NAT) of this natural mineral using a small amount of the mineral natrolite, scolecite or previously prepared Al-NAT zeolites as seed crystals. The synthesis of Al-NAT materials with nonfibrous morphologies was valuable for providing opportunities for industrial and environmental applications. The situ disorder-order transformation allowed controlling the degree of T-atom ordering in the zeolite framework and the corresponding chemical and physicochemical properties. The characterization results showed a smooth and continuous transformation in Al-NAT zeolites under the crystallization conditions investigated under the study.


Park M.B.,Center for Ordered Nanoporous Materials Synthesis | Park M.B.,ETH Zurich | Ahn S.H.,Center for Ordered Nanoporous Materials Synthesis | Ahn N.H.,Center for Ordered Nanoporous Materials Synthesis | Hong S.B.,Center for Ordered Nanoporous Materials Synthesis
Chemical Communications | Year: 2015

Nanocrystalline MEI- and BPH-type zeolites, denoted as PST-11 and PST-12, respectively, have been synthesized using both tetraethylammonium and tetramethylammonium ions, the two simplest alkylammonium species, in the presence of Li+ and Sr2+. PST-12 formation is the first example of a combination of forced and multiple cooperative structure-directions in the charge density mismatch synthesis of zeolites. This journal is © 2015 The Royal Society of Chemistry.


Jo D.,Center for Ordered Nanoporous Materials Synthesis | Lim J.B.,Center for Ordered Nanoporous Materials Synthesis | Ryu T.,Center for Ordered Nanoporous Materials Synthesis | Nam I.-S.,Center for Ordered Nanoporous Materials Synthesis | And 2 more authors.
Journal of Materials Chemistry A | Year: 2015

We have synthesized an aluminosilicate RTH-type zeolite with Si/Al = 10 using 1,2,3-trimethylimidazolium (123TMI+) as an organic structure-directing agent (OSDA) together with Na+ or K+ in hydroxide media and without the use of seed crystals. The zeolite obtained is characterized by a cuboid morphology made of very small ill-defined crystallites, largely different from the plank-like morphology typically observed for RTH-type zeolite crystals thus far. More interestingly, we show experimental evidence demonstrating that two 123TMI+ ions are located within each [46586484] cavity of the RTH framework, forming antiparallel dimers, as found by Rietveld refinement. When hydrothermally aged at 1023 K, Cu-RTH is much less active for NO reduction with NH3 than Cu-SSZ-13, the best catalyst known for this reaction to date. However, while the CO2 uptake (3.2 mmol g-1) on Na-RTH at 298 K and 1.0 bar is lower than that (4.5 mmol g-1) on zeolite Na-Rho, a well-studied small-pore zeolite that selectively adsorbs CO2, it exhibits much faster CO2 sorption kinetics. This renders our RTH zeolite potentially useful as a selective CO2 adsorbent. © The Royal Society of Chemistry 2015.


Jo D.,Center for Ordered Nanoporous Materials Synthesis | Lim J.B.,Center for Ordered Nanoporous Materials Synthesis | Ryu T.,Center for Ordered Nanoporous Materials Synthesis | Nam I.-S.,Center for Ordered Nanoporous Materials Synthesis | And 2 more authors.
Journal of Materials Chemistry A | Year: 2015

We have synthesized an aluminosilicate RTH-type zeolite with Si/Al = 10 using 1,2,3-trimethylimidazolium (123TMI+) as an organic structure-directing agent (OSDA) together with Na+ or K+ in hydroxide media and without the use of seed crystals. The zeolite obtained is characterized by a cuboid morphology made of very small ill-defined crystallites, largely different from the plank-like morphology typically observed for RTH-type zeolite crystals thus far. More interestingly, we show experimental evidence demonstrating that two 123TMI+ ions are located within each [46586484] cavity of the RTH framework, forming antiparallel dimers, as found by Rietveld refinement. When hydrothermally aged at 1023 K, Cu-RTH is much less active for NO reduction with NH3 than Cu-SSZ-13, the best catalyst known for this reaction to date. However, while the CO2 uptake (3.2 mmol g-1) on Na-RTH at 298 K and 1.0 bar is lower than that (4.5 mmol g-1) on zeolite Na-Rho, a well-studied small-pore zeolite that selectively adsorbs CO2, it exhibits much faster CO2 sorption kinetics. This renders our RTH zeolite potentially useful as a selective CO2 adsorbent. This journal is © The Royal Society of Chemistry 2015.


Byun Y.,Center for Ordered Nanoporous Materials Synthesis | Jo D.,Center for Ordered Nanoporous Materials Synthesis | Shin D.N.,Korea Advanced Institute of Science and Technology | Hong S.B.,Center for Ordered Nanoporous Materials Synthesis
ACS Catalysis | Year: 2014

The strain energies of three trimethylated diphenylmethane (3mDPM) and six tetramethylated diphenylmethane (4mDPM) isomers serving as the main reaction intermediates of m-xylene isomerization and disproportionation over eight medium-pore zeolites with different framework topologies have been determined theoretically in order to elucidate the effects of zeolite pore structure on this aromatic transformation. Although the strain energies of 3mDPM and 4mDPM derivatives in MCM-22, TNU-9, and NU-87, all of which have large 12-ring cavities/channels, are always lower than 40 kJ mol-1, some of them in cavity-free ZSM-5, ZSM-57, and TNU-10 are characterized by the strain energies higher than 40 kJ mol-1. In particular, all the species in ZSM-22 and ZSM-23 with narrower one-dimensional 10-ring channels have the strain energies much higher than 40 kJ mol-1. On the other hand, the energy difference (<30 kJ mol-1) between the (dimethylphenyl)methylium ion and the transition state for formation of the tetramethylated benzenium-type carbenium ions was calculated to be much lower than the energy barrier (183 kJ mol-1) to the hydride transfer from the reactant molecule. The overall results of this study clearly show that transition-state shape selectivity is responsible for the formation of 3mDPM derivatives, as well as of slightly larger 4mDPM ones, in medium-pore zeolites. © 2014 American Chemical Society.


PubMed | Center for Ordered Nanoporous Materials Synthesis
Type: Journal Article | Journal: Angewandte Chemie (International ed. in English) | Year: 2014

The transformation from a disordered into an ordered version of the zeolite natrolite occurs on prolonged heating of this material in the crystallizing medium, but not if the mother liquor is replaced by water or an alkaline solution. This process occurs for both aluminosilicate and gallosilicate analogues of natrolite. In cross experiments, the disordered Al-containing (or Ga-containing) analogue is heated while in contact with the mother liquor of the opposite analogue, that is, the Ga-containing (or Al-containing) liquor. Therefore, strong evidence for the mechanism of the ordering process was obtained, which was thus proposed to proceed by intraframework migration of tetrahedral atoms without diffusion along the pores. Migration is first triggered, then fuelled by surface rearrangement through reactions with the mother liquor, and stops when an almost fully ordered state is attained. Classical dissolution-recrystallization and Ostwald ripening processes do not appear to be relevant for this phase transformation.

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