Search results

The synthesis of crystalline microporous materials containing large pores is in high demand by industry, especially for the use of these materials as catalysts in chemical processes involving bulky molecules. An extra-large-pore silicoaluminophosphate with 16-ring openings, ITQ-51, has been synthesized by the use of bulky aromatic proton sponges as organic structure-directing agents. Proton sponges show exceptional properties for directing extra-large zeolites because of their unusually high basicity combined with their large size and rigidity. This extra-large-pore material is stable after calcination, being one of the very few examples of hydrothermally stable molecular sieves containing extra-large pores. The structure of ITQ-51 was solved from submicrometer-sized crystals using the rotation electron diffraction method. Finally, several hypothetical zeolites related to ITQ-51 have been proposed. ; The authors gratefully acknowledge Dr. Alejandro Vidal-Moya for the SUP>27 /SUP>Al MQ MAS NMR experiment. The authors also acknowledge financial support from Ministerio de Economia y Competitividad of Spain (MAT2012-37160), Consolider Ingenio 2010-MULTICAT, Generalitat Valenciana through the PROMETEO program, Universitat Politecnica de Valencia through PAID-06-11 (n.1952), the Swedish Research Council (VR), the Swedish Governmental Agency for Innovation Systems (VINNOVA), and the Goran Gustafsson Foundation. M. M. also acknowledges "Subprograma Ramon y Cajal" for Contract RYC-2011-08972. The TEM used in this study was purchased from a grant by the Knut and Alice Wallenberg Foundation. ; Martínez Franco, R.; Moliner Marin, M.; Yun, Y.; Sun, J.; Wan, W.; Zou, X.; Corma Canós, A. (2013). Synthesis of an extra-large molecular sieve using proton sponges as organic structure-directing agents. Proceedings of the National Academy of Sciences. 110(10):3749-3754. https://doi.org/10.1073/pnas.1220733110 ; S ; 3749 ; 3754 ; 110 ; 10

The combination of different experimental techniques, such as solid C-13 and H-1 magic-angle spinning NMR spectroscopy, fluorescence spectroscopy and powder X-ray diffraction, together with theoretical calculations allows the determination of the unique structure directing the role of the bulky aromatic proton sponge 1,8-bis(dimethylamino)naphthalene (DMAN) towards the extra-large-pore ITQ-51 zeolite through supra-molecular assemblies of those organic molecules. ; This work has been supported by the Spanish Government through Consolider Ingenio 2010-Multicat, the 'Severo Ochoa Programme' (SEV 2012-0267), MAT2012-37160; UPV through PAID-06-11 (no. 1952); the Swedish Research Council (VR) and the Swedish Governmental Agency for Innovation Systems (VINNOVA). ; Martínez Franco, R.; Sun, J.; Sastre Navarro, GI.; Yun, Y.; Zou, X.; Moliner Marin, M.; Corma Canós, A. (2014). Supra-molecular assembly of aromatic proton sponges to direct the crystallization of extra-large-pore zeotypes. Proceedings of the Royal Society of London. Series A, Mathematical and physical sciences. 470:1-13. https://doi.org/10.1098/rspa.2014.0107 ; S ; 1 ; 13 ; 470 ; Moliner, M., Rey, F., & Corma, A. (2013). Towards the Rational Design of Efficient Organic Structure-Directing Agents for Zeolite Synthesis. Angewandte Chemie International Edition, 52(52), 13880-13889. doi:10.1002/anie.201304713 ; Freyhardt, C. C., Tsapatsis, M., Lobo, R. F., Balkus, K. J., & Davis, M. E. (1996). A high-silica zeolite with a 14-tetrahedral-atom pore opening. Nature, 381(6580), 295-298. doi:10.1038/381295a0 ; Wagner, P., Yoshikawa, M., Tsuji, K., Davis, M. E., Wagner, P., Lovallo, M., & Taspatsis, M. (1997). CIT-5: a high-silica zeolite with 14-ring pores. Chemical Communications, (22), 2179-2180. doi:10.1039/a704774f ; Burton, A., Elomari, S., Chen, C.-Y., Medrud, R. C., Chan, I. Y., Bull, L. M., … Vittoratos, E. S. (2003). SSZ-53 and SSZ-59: Two Novel Extra-Large Pore Zeolites. Chemistry - A European Journal, 9(23), 5737-5748. ...

[EN] The synthesis of crystalline molecular sieves with pore dimensions that fill the gap between microporous and mesoporous materials is a matter of fundamental and industrial interest(1-3). The preparation of zeolitic materials with extralarge pores and chiral frameworks would permit many new applications. Two important steps in this direction include the synthesis(4) of ITQ-33, a stable zeolite with 18 x 10 x 10 ring windows, and the synthesis(5) of SU-32, which has an intrinsically chiral zeolite structure and where each crystal exhibits only one handedness. Here we present a germanosilicate zeolite (ITQ-37) with extralarge 30-ring windows. Its structure was determined by combining selected area electron diffraction ( SAED) and powder X-ray diffraction (PXRD) in a charge-flipping algorithm(6). The framework follows the SrSi2 (srs) minimal net(7) and forms two unique cavities, each of which is connected to three other cavities to form a gyroidal channel system. These cavities comprise the enantiomorphous srs net of the framework. ITQ-37 is the first chiral zeolite with one single gyroidal channel. It has the lowest framework density (10.3 T atoms per 1,000 angstrom(3)) of all existing 4-coordinated crystalline oxide frameworks, and the pore volume of the corresponding silica polymorph would be 0.38 cm(3) g(-1). ; This project is supported by the CICYT ( Project MAT 2006-14274-C02-01 and Prometeo 2008 GV), the Swedish Research Council (VR) and the Swedish Governmental Agency for Innovation Systems (VINNOVA). J.S. and C. B. are supported by post-doctoral grants from the Carl-Trygger and Wenner-Gren foundations respectively. M. M. thanks ITQ for a scholarship. ; Sun, J.; Bonneau, C.; Cantin Sanz, A.; Corma Canós, A.; Díaz Cabañas, MJ.; Moliner Marin, M.; Zhang, D. (2009). ITQ-37 a chiral zeolite framework following the SrSi2 net and containing 30-ring extra-large gyroidal channels. Nature. 458(7242):1154-1158. https://doi.org/10.1038/nature07957 ; S ; 1154 ; 1158 ; 458 ; 7242 ; Davis, M. E. Ordered porous ...

[EN] It was found that either polymorph B or polymorph C of zeolite beta can be obtained from the same structure directing agent: 4,4-dimethyl-4-azonia-tricyclo[5.2.2.0(2,6)] undec-8-ene hydroxide. The synthesis occurs through a consecutive process where polymorph B is first formed and then transformed into polymorph C. It is possible to produce a zeolite highly enriched in polymorph B, provided that the transformation of this phase into polymorph C is slowed down up to the point where polymorph C is only detected at trace levels. The structure of polymorph B was determined for the first time by electron crystallography with SAED and HRTEM from areas of unfaulted polymorph B crystals. ; Financial support from the Spanish Government (Project MAT2006-14274-C02–01) and the EU Commission (TOPCOMBI Project) is gratefully acknowledged. M.M. thanks CSIC for an I3P grant. J.S. is supported by a postdoctoral grant from the Carl Trygger Foundation. The Berzelii Centre EXSELENT is supported by the Swedish Research Council (VR) and the Swedish Governmental Agency for Innovation Systems (VINNOVA). ; Corma Canós, A.; Moliner Marin, M.; Cantin Sanz, A.; Díaz Cabañas, MJ.; Jorda Moret, JL.; Zhang, D.; Sun, J. (2008). Synthesis and structure of polymorph B of zeolite Beta. Chemistry of Materials. 20(9):3218-3223. doi:10.1021/cm8002244 ; S ; 3218 ; 3223 ; 20 ; 9

As an alternative technology to energy intensive distillations, adsorptive separation by porous solids offers lower energy cost and higher efficiency. Herein we report a topology-directed design and synthesis of a series of Zr-based metal-organic frameworks with optimized pore structure for efficient separation of C6 alkane isomers, a critical step in the petroleum refining process to produce gasoline with high octane rating. Zr6O4(OH)4(bptc)3 adsorbs a large amount of n-hexane but excluding branched isomers. The n-hexane uptake is ~70% higher than that of a benchmark adsorbent, zeolite-5A. A derivative structure, Zr6O4(OH)8(H2O)4(abtc)2, is capable of discriminating all three C6 isomers and yielding a high separation factor for 3-methylpentane over 2,3-dimethylbutane. This property is critical for producing gasoline with further improved quality. Multicomponent breakthrough experiments provide a quantitative measure of the capability of these materials for separation of C6 alkane isomers. A detailed structural analysis reveals the unique topology, connectivity and relationship of these compounds. ; We would like to thank the financial support from the Materials Sciences and Engineering Division, Office of Basic Research Energy Sciences of the U.S. Department of Energy through Grant no. DE-FG02-08ER-46491. Y.H. acknowledges the KAUST CCF fund for supporting this study. The Advanced Light Source is supported by the Director, Office of Science, Office of Basic Energy Sciences, of the U.S. Department of Energy under Contract No. DE-AC02-05CH11231. T.T. acknowledges generous support from the Simons Foundation through Grant no. 391888, which endowed his sabbatical at MIT. D.M.P. thanks the Russian Government (Grant 14.B25.31.0005). E.V.A. is grateful to the Russian Science Foundation (Grant no. 16-13-10158). The RU team would also like to acknowledge Micromeritics Instrument Corp. for the award of a 3Flex system through its Instrument Grant program. H.W. would like to thank Ever Velasco for helpful discussions.