Bulletin of the American Physical Society
APS March Meeting 2019
Volume 64, Number 2
Monday–Friday, March 4–8, 2019; Boston, Massachusetts
Session P31: Advances in Hierarchical Systems: Theory and Experiments IIInvited
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Sponsoring Units: DCP Chair: Neeraj Rai, Mississippi State University; Dongxia Liu, University of Maryland Room: BCEC 203 |
Wednesday, March 6, 2019 2:30PM - 3:06PM |
P31.00001: Nanosized zeolites: targets and challenges Invited Speaker: Svetlana Mintova This presentation will highlight recent developments in the synthesis and unconventional applications of nanosized zeolites. The factors controlling the formation of nanosized zeolites underlining the most promising approaches from the viewpoint of large-scale production will be discussed. The strategies available for the preparation of nanosized zeolites including organic-template assisted, organic-template free, and seed approach will be presented. A special attention will be paid to zeolite formation in conventional organic-template-free zeolite yielding systems. Additionally the preparation of defect free zeolites using a “soft” chemistry approach will be discussed. |
Wednesday, March 6, 2019 3:06PM - 3:42PM |
P31.00002: Characterization of silanol defect sites on amorphous versus crystalline 2-D silicate surfaces Invited Speaker: Alexander Katz We compare and contrast the nature of silanols on open, two-dimensional surfaces comprising amorphous and crystalline siliceous materials. We compare the thermal treatment of silanols in both sets of materials, using several forms of spectroscopy for characterization. The ramifications of the observed differences on applications will be highlilghted. |
Wednesday, March 6, 2019 3:42PM - 4:18PM |
P31.00003: Synthesis and Catalytic Performance of Hierarchical Materials Derived from Metal-Organic Frameworks Invited Speaker: Jason Hicks Hierarchical materials have many benefits in catalytic applications. We have been specifically interested in the synthesis of hierarchical materials for a variety of energy-related applications including biomass fast pyrolysis, coupling of aldehydes and/or ketones from biomass feed streams, and sulfur removal from petroleum feed sources.1-4 This presentation will provide our current progress in the following areas: 1) synthesis and characterization of hierarchical metal-organic framework (MOF) materials, and 2) metal nanoparticles supported on hierarchical carbon supports derived from MOFs. I will discuss a vapor-assisted crystallization method developed in our lab using zeolite synthesis literature as inspiration, where a dry gel is initially formed that promotes MOF crystallization and the formation of hierarchical materials. The detailed characterization of these novel materials will be discussed, as well as their catalytic performance. |
Wednesday, March 6, 2019 4:18PM - 4:54PM |
P31.00004: Simulating Adsorption and Transport in Hierarchical Zeolites Invited Speaker: J. Ilja Siepmann Hierarchical zeolites are advanced materials possessing the catalytic and adsorption properties of conventional zeolites while potentially eliminating their transport limitations through the introduction of mesopores. Recent experiments comparing the adsorption and transport in hierarchical self-pillared pentasil (SPP) zeolites (SPP) to microporous silicalite-1 (MFI) revealed an interesting crossover in sorbate loading and significantly slower than expected diffusion for alkanes, but explanation for these observations are not readily available through experimental probes due to the complications arising from the presence of multiple adsorption sites and blocked pore entrances. In this talk, we will present results from Gibbs ensemble Monte Carlo and canonical ensemble molecular dynamics simulations to unravel the peculiar properties of SPP zeolites. Computed isotherms for argon, hydrogen, alkanes, ethanol, and water demonstrate striking differences in the adsorption behavior for these adsorbates. Depending on the loading, diffusion can proceed via the micropores, on the mesopore walls, or through the mesopore interior. |
Wednesday, March 6, 2019 4:54PM - 5:30PM |
P31.00005: Unexpected Long Walks in Hierarchical Porous Materials with Combined Surface and Configurational Diffusion Invited Speaker: Wei Fan Hierarchical zeolites and zeolite nanocrystals with micropore lengths on the order of nanometers have been synthesized with the aim of reducing mass transfer limitation. However, due to the large external surface to volume ratios, the mass transport in these materials can be hindered by a secondary rate limitation step imposed on the external surface of the zeolites. In this talk, I will present our recent study on the mass transport in hierarchical zeolites and zeolite nanoparticles. We show that surface barrier is related to the presence of pore re-entry caused by strong sorbate/sorbent interaction at the zeolite surface. In order to understand the nature of the surface barrier, a set of silica nanoparticle (SNP)/Silicalite-1 composites with different external surface to micropore surface ratios was synthesized. It was found that the strong sorbate/sorbent interaction at the external surface of Silicalite-1 nanoparticles can cause diffusing molecules to re-enter into micropores and repeat the micropore diffusion process. This pore re-entry step can lead to an unusually long micropore diffusion length. We also demonstrate that this repeated micropore diffusion process can be effectively reduced by mixing the zeolite nanoparticles with secondary, nonporous nanoparticles. It was concluded that the surface barrier in hierarchical zeolites and zeolite nanoparticles is likely due to a combination of pore re-entry of adsorbates and pore blockage. |
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