Molecular behaviour of phenol in zeolite Beta catalysts as a function of acid site presence: a quasielastic neutron scattering and molecular dynamics simulation study

Carlos Hernandez-Tamargo, Alexander O'Malley, Ian P. Silverwood, Nora H. de Leeuw

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Abstract

Quasielastic neutron scattering (QENS) experiments complemented by classical molecular dynamics (MD) simulations at 393–443 K were employed in a study of the mobility and interactions of phenol in acidic zeolite H-Beta, to understand systems relevant to potential routes for the depolymerization and hydrodeoxygenation of lignin. QENS experiments observed isotropic phenol rotation with a fraction of static molecules, yielding rotational diffusion coefficients between 2.60 × 1010 and 3.33 × 1010 s−1 and an activation energy of rotation of 7.2 kJ mol−1. The MD simulations of phenol in the acidic and all-silica zeolite corroborate the experimental results, where molecules strongly adsorbed to the acidic sites behave as an immobile fraction with minimal contribution to the rotational diffusion, and the mobile molecules yield similar rotational diffusion coefficients to experiment. Translational diffusion is too slow to be detected in the instrumental time window of the QENS experiments, which is supported by MD-calculated activation energies of translation larger than 25 kJ mol−1. The study illustrates the effect of active sites in potential catalyst structures on the dynamical behaviour of molecules relevant to biomass conversion.
Original languageEnglish
Pages (from-to)6700-6713
Number of pages14
JournalCatalysis Science and Technology
Volume9
Issue number23
Early online date4 Nov 2019
DOIs
Publication statusPublished - 31 Dec 2019

Bibliographical note

Funding Information:
This work was performed using the computational facilities of the Advanced Research Computing @ Cardiff (ARCCA) Division, Cardiff University, and HPC Wales. Via our membership of the UK's HEC Materials Chemistry Consortium, which is funded by EPSRC [grant number: EP/ L000202], this work used the ARCHER UK National Supercomputing Service (http://www.archer.ac.uk). The authors acknowledge EPSRC [grant number: EP/K009567/2] and NERC [grant number: NE/R009376/1] for funding. C. H. T. thanks Dr. S. E. Ruiz-Hernandez for valuable consultations. A. J. O. M. acknowledges the Ramsay Memorial Trust for the provision of a Ramsay Memorial Fellowship, and Roger and Sue Whorrod for the funding of the Whorrod Fellowship. The STFC Rutherford Appleton Laboratory is thanked for access to neutron beam facilities; the data from our experiment RB1720221 can be found at DOI:10.5286/ISIS.E.87772570. All computer simulation data created during this research is openly available from the University of Cardiff Research Portal at http://doi.org/10.17035/d.2019.0082440884.

Publisher Copyright:
© 2019 The Royal Society of Chemistry.

ASJC Scopus subject areas

  • Catalysis

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