title: Modelling metal centres, acid sites and reaction mechanisms in microporous catalysts.
abstract: We discuss the role of QM/MM (embedded cluster) computational techniques in catalytic science, in particular their application to microporous catalysis. We describe the methodologies employed and illustrate their utility by briefly summarising work on metal centres in zeolites. We then report a detailed investigation into the behaviour of methanol at acidic sites in zeolites H-ZSM-5 and H-Y in the context of the methanol-to-hydrocarbons/olefins process. Studying key initial steps of the reaction (the adsorption and subsequent methoxylation), we probe the effect of framework topology and Brønsted acid site location on the energetics of these initial processes. We find that although methoxylation is endothermic with respect to the adsorbed system (by 17-56 kJ mol(-1) depending on the location), there are intriguing correlations between the adsorption/reaction energies and the geometries of the adsorbed species, of particular significance being the coordination of methyl hydrogens. These observations emphasise the importance of adsorbate coordination with the framework in zeolite catalysed conversions, and how this may vary with framework topology and site location, particularly suited to investigation by QM/MM techniques.
authors.affiliation: Department of Chemistry, University College London, 20 Gordon St., London WC1 HOAJ, UK and UK Catalysis Hub, Research Complex at Harwell, Science and Technology Facilities Council Rutherford Appleton Laboratory, Harwell Science and Innovation Campus, Oxon OX11 0QX, UK.
authors.forename: Alexander J
authors.initials: AJ
authors.lastname: O'Malley
authors.affiliation: Department of Chemistry, University College London, 20 Gordon St., London WC1 HOAJ, UK and Cardiff Catalysis Institute, School of Chemistry, Cardiff University, CF10 3AT, UK.
authors.forename: A J
authors.initials: AJ
authors.lastname: Logsdail
authors.affiliation: Department of Chemistry, University College London, 20 Gordon St., London WC1 HOAJ, UK.
authors.forename: A A
authors.initials: AA
authors.lastname: Sokol
authors.affiliation: Department of Chemistry, University College London, 20 Gordon St., London WC1 HOAJ, UK and Cardiff Catalysis Institute, School of Chemistry, Cardiff University, CF10 3AT, UK and UK Catalysis Hub, Research Complex at Harwell, Science and Technology Facilities Council Rutherford Appleton Laboratory, Harwell Science and Innovation Campus, Oxon OX11 0QX, UK.
authors.forename: C R A
authors.initials: CR
authors.lastname: Catlow