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Title: Coke formation in a zeolite crystal during the methanol-to-hydrocarbons reaction as studied with atom probe tomography

Abstract

Understanding the formation of carbon deposits in zeolites is vital to developing new, superior materials for various applications, including oil and gas conversion processes. Herein, atom probe tomography (APT) has been used to spatially resolve the 3D compositional changes at the sub-nm length scale in a single zeolite ZSM-5 crystal, which has been partially deactivated by the methanol-to-hydrocarbons reaction using 13C-labeled methanol. The results reveal the formation of coke in agglomerates that span length scales from tens of nanometers to atomic clusters with a median size of 30–60 13C atoms. These clusters correlate with local increases in Brønsted acid site density, demonstrating that the formation of the first deactivating coke precursor molecules occurs in nanoscopic regions enriched in aluminum. Here, this nanoscale correlation underscores the importance of carefully engineering materials to suppress detrimental coke formation.

Authors:
 [1];  [2];  [2];  [1];  [1];  [1];  [1];  [3];  [1]
  1. Utrecht Univ., Utrecht (Netherlands)
  2. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
  3. SLAC National Accelerator Lab., Menlo Park, CA (United States)
Publication Date:
Research Org.:
Oak Ridge National Laboratory (ORNL), Oak Ridge, TN (United States). Center for Nanophase Materials Sciences (CNMS)
Sponsoring Org.:
USDOE Office of Science (SC)
OSTI Identifier:
1324189
Grant/Contract Number:
AC05-00OR22725
Resource Type:
Journal Article: Accepted Manuscript
Journal Name:
Angewandte Chemie (International Edition)
Additional Journal Information:
Journal Name: Angewandte Chemie (International Edition); Journal Volume: 55; Journal Issue: 37; Journal ID: ISSN 1433-7851
Publisher:
Wiley
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; 37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY; zeolites; atom probe tomography; carbon deposits; Al zoning; methanol to hydrocarbons

Citation Formats

Schmidt, Joel E., Poplawsky, Jonathan D., Mazumder, Baishakhi, Attila, Özgün, Fu, Donglong, de Winter, D. A. Matthijs, Meirer, Florian, Bare, Simon R., and Weckhuysen, Bert M.. Coke formation in a zeolite crystal during the methanol-to-hydrocarbons reaction as studied with atom probe tomography. United States: N. p., 2016. Web. doi:10.1002/anie.201606099.
Schmidt, Joel E., Poplawsky, Jonathan D., Mazumder, Baishakhi, Attila, Özgün, Fu, Donglong, de Winter, D. A. Matthijs, Meirer, Florian, Bare, Simon R., & Weckhuysen, Bert M.. Coke formation in a zeolite crystal during the methanol-to-hydrocarbons reaction as studied with atom probe tomography. United States. doi:10.1002/anie.201606099.
Schmidt, Joel E., Poplawsky, Jonathan D., Mazumder, Baishakhi, Attila, Özgün, Fu, Donglong, de Winter, D. A. Matthijs, Meirer, Florian, Bare, Simon R., and Weckhuysen, Bert M.. Wed . "Coke formation in a zeolite crystal during the methanol-to-hydrocarbons reaction as studied with atom probe tomography". United States. doi:10.1002/anie.201606099. https://www.osti.gov/servlets/purl/1324189.
@article{osti_1324189,
title = {Coke formation in a zeolite crystal during the methanol-to-hydrocarbons reaction as studied with atom probe tomography},
author = {Schmidt, Joel E. and Poplawsky, Jonathan D. and Mazumder, Baishakhi and Attila, Özgün and Fu, Donglong and de Winter, D. A. Matthijs and Meirer, Florian and Bare, Simon R. and Weckhuysen, Bert M.},
abstractNote = {Understanding the formation of carbon deposits in zeolites is vital to developing new, superior materials for various applications, including oil and gas conversion processes. Herein, atom probe tomography (APT) has been used to spatially resolve the 3D compositional changes at the sub-nm length scale in a single zeolite ZSM-5 crystal, which has been partially deactivated by the methanol-to-hydrocarbons reaction using 13C-labeled methanol. The results reveal the formation of coke in agglomerates that span length scales from tens of nanometers to atomic clusters with a median size of 30–60 13C atoms. These clusters correlate with local increases in Brønsted acid site density, demonstrating that the formation of the first deactivating coke precursor molecules occurs in nanoscopic regions enriched in aluminum. Here, this nanoscale correlation underscores the importance of carefully engineering materials to suppress detrimental coke formation.},
doi = {10.1002/anie.201606099},
journal = {Angewandte Chemie (International Edition)},
number = 37,
volume = 55,
place = {United States},
year = {Wed Aug 03 00:00:00 EDT 2016},
month = {Wed Aug 03 00:00:00 EDT 2016}
}

Journal Article:
Free Publicly Available Full Text
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Cited by: 9works
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  • The conditions in which coke deposits are formed on active centers inside the channels of zeolites of the pentasil type were determined. The nature of the coke deposits was studied by EPR and thermography. The EPR spectra of coke-clogged zeolites were obtained for the first time and are the superposition of three signals corresponding to three types of coke deposits, one of which is inaccessible to O/sub 2/ molecules.
  • Methanol was converted to hydrocarbons, primarily olefins, and water over a low-activity HZSM-5 zeolite catalyst with a SiO/sub 2//Al/sub 2/O/sub 3/ ratio of 1600/1. Mixtures of methanol and individual C/sub 2/-C/sub 4/ olefins were also used to simulate conditions in the catalyst bed at low conversions. Facile methylation of olefins with methanol to produce the next higher olefinic homolog was observed. Ethylene was the major primary hydrocarbon produced from methanol at low conversion. The olefin mixtures isolated under various conditions of reaction were fitted to the chain-growth kinetics as described by the Flory equation. Good to excellent correlation coefficients weremore » found at low and medium conversions of methanol. This is consistent with a stepwise growth in molecular weight of the olefins, starting with propylene, by alkylation of the olefins with methanol. However, since ethylene is produced by a different mechanism, it does not fit the Flory equation. At higher temperatures and conversions, the olefins undergo scrambling or thermodynamic equilibration reactions also producing olefin mixtures with good correlation coefficients. Under the latter conditions, a distinction between the stepwise growth and thermodynamic equilibration reactions cannot be made since both contribute to the product mixture.« less
  • It is shown by SEM imaging of the tip and by observing the emission pattern of the evaporated atoms that laser assisted evaporation in an atom probe can lead to nonhemispherical tip shapes and time-dependent nonuniform emission. We have investigated this nonuniformity by observing the change in field of view when using laser wavelengths of 515 nm and 343 nm on silicon. The change is monitored in situ by 0.5 nm thick silicon oxide. We demonstrate that the field of view can easily be changed by more than 10 nm and that the apparent oxide layer thickness can deviate substantiallymore » from its correct value. The dependence of the tip shape deformations and the reconstruction artifacts on the laser wavelength are explained through simulations of the laser-tip interaction and nonhomogeneous heating effects.« less
  • In the conversion of oxygen-containing compounds on high-silicon zeolites (HSZ), a large amount of water (up to 56 wt.%) is formed, which results in significant changes in the catalytic properties of the HSZ at high temperatures. The effect of coke formation and water on conversion of methanol on HSZ was investigated in this study. The studies were conducted on HSZ with a silicate modulus of 50. Conversion of methanol was studied in a flow-type installation at atmospheric pressure, 663/sup 0/K, and with a volume flow rate of 0.8-0.9 h/sup -1/. The acid properties of the HSZ were studied with adsorptionmore » of ammonia by the thermal desorption method.« less
  • The benefit of direct coupling of APT with TEM dark field imaging to investigate early stages of phase transformation in multicomponent alloys is demonstrated by analyzing alpha phase precipitated in a model Ti-10 at% Mo-10 at% Al alloy during annealing at 400oC. Through such a direct coupling approach a thermodynamically unexpected solute partitioning trend between beta matrix and alpha precipitate is observed in the early stages of precipitation, which is explained based on possible nucleation of alpha phase in the Ti rich (Mo and Al depleted regions) created as a result of phase separation in beta matrix. On further highermore » temperature annealing at 600oC for 1 hour, the alpha precipitates were shown to grow and get enriched in Al and further depleted in Mo reaching the thermodynamic equilibrium.« less