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Title: Isolating Clusters of Light Elements in Molecular Sieves with Atom Probe Tomography

Abstract

Understanding the 3-D distribution and nature of active sites in heterogeneous catalysts is critical to developing structure–function relationships. However, this is difficult to achieve in microporous materials as there is little relative z-contrast between active and inactive framework elements (e.g., Al, O, P, and Si), making them difficult to differentiate with electron microscopies. We have applied atom probe tomography (APT), currently the only nanometer-scale 3-D microscopy to offer routine light element contrast, to the methanol-to-hydrocarbons (MTH) catalyst SAPO-34, with Si as the active site, which may be present in the framework as either isolated Si species or clusters (islands) of Si atoms. 29Si solid-state NMR data on isotopically enriched and natural abundance materials are consistent with the presence of Si islands, and the APT results have been complemented with simulations to show the smallest detectable cluster size as a function of instrument spatial resolution and detector efficiency. We have identified significant Si–Si affinity in the materials, as well as clustering of coke deposited by the MTH reaction (13CH3OH used) and an affinity between Brønsted acid sites and coke. A comparison with simulations shows that the ultimate spatial resolution that can be attained by APT applied to molecular sieves is 0.5–1more » nm. Finally, the observed 13C clusters are consistent with hydrocarbon pool mechanism intermediates that are preferentially located in regions of increased Brønsted acidity.« less

Authors:
 [1];  [2];  [1];  [1]; ORCiD logo [3];  [3];  [1];  [1];  [1]; ORCiD logo [1];  [1];  [1];  [3]; ORCiD logo [1]
  1. Univ. of Utrecht (Netherlands)
  2. Grinnell College, IA (United States)
  3. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
Publication Date:
Research Org.:
Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
Sponsoring Org.:
USDOE
OSTI Identifier:
1474493
Grant/Contract Number:  
AC05-00OR22725
Resource Type:
Accepted Manuscript
Journal Name:
Journal of the American Chemical Society
Additional Journal Information:
Journal Volume: 140; Journal Issue: 29; Journal ID: ISSN 0002-7863
Publisher:
American Chemical Society (ACS)
Country of Publication:
United States
Language:
English
Subject:
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY

Citation Formats

Schmidt, Joel E., Peng, Linqing, Paioni, Alessandra Lucini, Ehren, Helena Leona, Guo, Wei, Mazumder, Baishakhi, Matthijs de Winter, D. A., Attila, Özgün, Fu, Donglong, Chowdhury, Abhishek Dutta, Houben, Klaartje, Baldus, Marc, Poplawsky, Jonathan D., and Weckhuysen, Bert M. Isolating Clusters of Light Elements in Molecular Sieves with Atom Probe Tomography. United States: N. p., 2018. Web. doi:10.1021/jacs.8b04494.
Schmidt, Joel E., Peng, Linqing, Paioni, Alessandra Lucini, Ehren, Helena Leona, Guo, Wei, Mazumder, Baishakhi, Matthijs de Winter, D. A., Attila, Özgün, Fu, Donglong, Chowdhury, Abhishek Dutta, Houben, Klaartje, Baldus, Marc, Poplawsky, Jonathan D., & Weckhuysen, Bert M. Isolating Clusters of Light Elements in Molecular Sieves with Atom Probe Tomography. United States. doi:10.1021/jacs.8b04494.
Schmidt, Joel E., Peng, Linqing, Paioni, Alessandra Lucini, Ehren, Helena Leona, Guo, Wei, Mazumder, Baishakhi, Matthijs de Winter, D. A., Attila, Özgün, Fu, Donglong, Chowdhury, Abhishek Dutta, Houben, Klaartje, Baldus, Marc, Poplawsky, Jonathan D., and Weckhuysen, Bert M. Fri . "Isolating Clusters of Light Elements in Molecular Sieves with Atom Probe Tomography". United States. doi:10.1021/jacs.8b04494. https://www.osti.gov/servlets/purl/1474493.
@article{osti_1474493,
title = {Isolating Clusters of Light Elements in Molecular Sieves with Atom Probe Tomography},
author = {Schmidt, Joel E. and Peng, Linqing and Paioni, Alessandra Lucini and Ehren, Helena Leona and Guo, Wei and Mazumder, Baishakhi and Matthijs de Winter, D. A. and Attila, Özgün and Fu, Donglong and Chowdhury, Abhishek Dutta and Houben, Klaartje and Baldus, Marc and Poplawsky, Jonathan D. and Weckhuysen, Bert M.},
abstractNote = {Understanding the 3-D distribution and nature of active sites in heterogeneous catalysts is critical to developing structure–function relationships. However, this is difficult to achieve in microporous materials as there is little relative z-contrast between active and inactive framework elements (e.g., Al, O, P, and Si), making them difficult to differentiate with electron microscopies. We have applied atom probe tomography (APT), currently the only nanometer-scale 3-D microscopy to offer routine light element contrast, to the methanol-to-hydrocarbons (MTH) catalyst SAPO-34, with Si as the active site, which may be present in the framework as either isolated Si species or clusters (islands) of Si atoms. 29Si solid-state NMR data on isotopically enriched and natural abundance materials are consistent with the presence of Si islands, and the APT results have been complemented with simulations to show the smallest detectable cluster size as a function of instrument spatial resolution and detector efficiency. We have identified significant Si–Si affinity in the materials, as well as clustering of coke deposited by the MTH reaction (13CH3OH used) and an affinity between Brønsted acid sites and coke. A comparison with simulations shows that the ultimate spatial resolution that can be attained by APT applied to molecular sieves is 0.5–1 nm. Finally, the observed 13C clusters are consistent with hydrocarbon pool mechanism intermediates that are preferentially located in regions of increased Brønsted acidity.},
doi = {10.1021/jacs.8b04494},
journal = {Journal of the American Chemical Society},
number = 29,
volume = 140,
place = {United States},
year = {2018},
month = {7}
}

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