title: Methanol diffusion in zeolite HY: a combined quasielastic neutron scattering and molecular dynamics simulation study.
abstract: The diffusion of methanol in zeolite HY is studied using tandem quasielastic neutron scattering (QENS) experiments and molecular dynamics (MD) simulations at 300-400 K. The experimental diffusion coefficients were measured in the range 2-5 × 10(-10) m(2) s(-1) and simulated diffusion coefficients calculated in the range of 1.6-3.2 × 10(-9) m(2) s(-1). Activation energies were measured as 8.8 and 6.9 kJ mol(-1) using QENS and MD respectively. Differences may be attributed predominantly to the experimental use of a dealuminated HY sample, containing significant defects such as strongly adsorbing silanol nests, compared to a perfect simulated crystal containing only evenly distributed Brønsted acid sites. Experimental and simulated diffusivities measured in this study are lower than those obtained from those previously calculated in siliceous faujasite, due to methanol H-bonding to Brønsted acid sites as observed in the MD simulations. However, both experimental and simulated diffusivities were significantly higher than those obtained in NaX, due to the higher concentration of extraframework cations present in the previously studied structures.
authors.affiliation: Department of Chemistry, Materials Chemistry, University College London, Third Floor, Kathleen Lonsdale Building, Gower Street, London, WC1E 6BT, UK. c.r.a.catlow@ucl.ac.uk and The UK Catalysis Hub, Research Complex at Harwell, Rutherford Appleton Laboratory, Oxfordshire, OX11 0FA, UK.
authors.forename: Alexander J
authors.initials: AJ
authors.lastname: O'Malley
authors.affiliation: ISIS Facility, STFC Rutherford Appleton Laboratory, Chilton, Didcot, Oxfordshire, OX11 0QX, UK.
authors.forename: Victoria
authors.initials: V
authors.lastname: García Sakai
authors.affiliation: ISIS Facility, STFC Rutherford Appleton Laboratory, Chilton, Didcot, Oxfordshire, OX11 0QX, UK.
authors.forename: Ian P
authors.initials: IP
authors.lastname: Silverwood
authors.affiliation: Cardiff Catalysis Institute, School of Chemistry, Cardiff University, CF10 3AT, UK.
authors.forename: Nikolaos
authors.initials: N
authors.lastname: Dimitratos
authors.affiliation: The UK Catalysis Hub, Research Complex at Harwell, Rutherford Appleton Laboratory, Oxfordshire, OX11 0FA, UK and ISIS Facility, STFC Rutherford Appleton Laboratory, Chilton, Didcot, Oxfordshire, OX11 0QX, UK.
authors.forename: Stewart F
authors.initials: SF
authors.lastname: Parker
authors.affiliation: Department of Chemistry, Materials Chemistry, University College London, Third Floor, Kathleen Lonsdale Building, Gower Street, London, WC1E 6BT, UK. c.r.a.catlow@ucl.ac.uk and The UK Catalysis Hub, Research Complex at Harwell, Rutherford Appleton Laboratory, Oxfordshire, OX11 0FA, UK and Cardiff Catalysis Institute, School of Chemistry, Cardiff University, CF10 3AT, UK.
authors.forename: C Richard A
authors.initials: CR
authors.lastname: Catlow