Browsing by Author "Schmidt, Joel E."

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    Enantiomerically enriched, polycrystalline molecular sieves
    (2023-05-09) Davis, Mark E.; Brand, Stephen Kramer; Schmidt, Joel E.; Deem, Michael W.; Rice University; California Institute of Technology; William Marsh Rice University; United States Patent and Trademark Office
    This disclosure describes enantiomerically enriched chiral molecular sieves and methods of making and using the same. In some embodiments, the molecular sieves are silicates or germanosilicates of STW topology.
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    Enantiomerically enriched, polycrystalline molecular sieves
    (2021-12-21) Davis, Mark E.; Brand, Stephen Kramer; Schmidt, Joel E.; Deem, Michael W.; Rice University; California Institute of Technology; United States Patent and Trademark Office
    This disclosure describes enantiomerically enriched chiral molecular sieves and methods of making and using the same. In some embodiments, the molecular sieves are silicates or germanosilicates of STW topology.
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    Facile Synthesis and Catalysis of Pure-Silica and Heteroatom LTA
    (American Chemical Society, 2015) Boal, Ben W.; Schmidt, Joel E.; Deimund, Mark A.; Deem, Michael W.; Henling, Lawrence M.; Brand, Stephen K.; Zones, Stacey I.; Davis, Mark E.
    Zeolite A (LTA) has many large-scale uses in separations and ion exchange applications. Because of the high aluminum content and lack of high-temperature stability, applications in catalysis, while highly desired, have been extremely limited. Herein, we report a robust method to prepare pure-silica, aluminosilicate (product Si/Al = 12–42), and titanosilicate LTA in fluoride media using a simple, imidazolium-based organic structure-directing agent. The aluminosilicate material is an active catalyst for the methanol-to-olefins reaction with higher product selectivities to butenes as well as C5 and C6 products than the commercialized silicoalumniophosphate or zeolite analogue that both have the chabazite framework (SAPO-34 and SSZ-13, respectively). The crystal structures of the as-made and calcined pure-silica materials were solved using single-crystal X-ray diffraction, providing information about the occluded organics and fluoride as well as structural information.
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    Synthesis of a Specified, Silica Molecular Sieve Using Computationally Predicted Organic Structure Directing Agents
    (Wiley, 2014) Schmidt, Joel E.; Deem, Michael W.; Davis, Mark E.
    Crystalline molecular sieves are used in numerous applications, where the properties exploited for each technology are the direct consequence of structural features. New materials are typically discovered by trial and error, and in many cases, organic structure-directing agents (OSDAs) are used to direct their formation. Here, we report the first successful synthesis of a specified molecular sieve through the use of an OSDA that was predicted from a recently developed computational method that constructs chemically synthesizable OSDAs. Pentamethylimidazolium is computationally predicted to have the largest stabilization energy in the STW framework, and is experimentally shown to strongly direct the synthesis of pure-silica STW. Other OSDAs with lower stabilization energies did not form STW. The general method demonstrated here to create STW may lead to new, simpler OSDAs for existing frameworks and provide a way to predict OSDAs for desired, theoretical frameworks.
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    Template–Framework Interactions in Tetraethylammonium-Directed Zeolite Synthesis
    (Wiley, 2016) Schmidt, Joel E.; Fu, Donglong; Deem, Michael W.; Weckhuysen, Bert M.
    Zeolites, having widespread applications in chemical industries, are often synthesized using organic templates. These can be cost-prohibitive, motivating investigations into their role in promoting crystallization. Herein, the relationship between framework structure, chemical composition, synthesis conditions and the conformation of the occluded, economical template tetraethylammonium (TEA+) has been systematically examined by experimental and computational means. The results show two distinct regimes of occluded conformer tendencies: 1) In frameworks with a large stabilization energy difference, only a single conformer was found (BEA, LTA and MFI). 2) In the frameworks with small stabilization energy differences (AEI, AFI, CHA and MOR), less than the interconversion of TEA+ in solution, a heteroatom-dependent (Al, B, Co, Mn, Ti, Zn) distribution of conformers was observed. These findings demonstrate that host–guest chemistry principles, including electrostatic interactions and coordination chemistry, are as important as ideal pore-filling.