Dewi Lewis | University College London (original) (raw)
Papers by Dewi Lewis
Chem Mater, 1996
... John Meurig Thomas. Davy Faraday Research Laboratory, The Royal Institution of GB, 21 Albemar... more ... John Meurig Thomas. Davy Faraday Research Laboratory, The Royal Institution of GB, 21 Albemarle St., London, W1X 4BS UK. Chem. Mater. ... Commun. 1993, 1861. (2) Wright, PA; Sayag, C.; Rey, F.; Lewis, DW; Gale, JD; Natarajan, S.; Thomas, JM J. Chem. Soc., Faraday Trans. ...
The Journal of Physical Chemistry, 1995
Microporous solids are industrially important materials used for catalysis, ion exchange, and gas... more Microporous solids are industrially important materials used for catalysis, ion exchange, and gas separation. Synthesis of such materials usually involves crystallization from a gel medium under hydrothermal conditions. These gels are multi-component systems containing ...
The Journal of Physical Chemistry, 1995
Page 1. J. Phys. Chem. 1995,99, 2377-2383 2377 Structure of Iron-Substituted ZSM-5 Dewi W. Lewis,... more Page 1. J. Phys. Chem. 1995,99, 2377-2383 2377 Structure of Iron-Substituted ZSM-5 Dewi W. Lewis, C. Richard A. Catlow," and Gopinathan Sankar Davy-Faraday Laboratory, The Royal Institution of Great Britain, 21 Albemarle St., London, WIX 4BS, UK ...
Stud Surf Sci Catal, 2005
Density Functional Theory calculations are used to probe the energetics of the formation of key p... more Density Functional Theory calculations are used to probe the energetics of the formation of key pre-nucleation species implicated in the formation of zeolites. We demonstrate that the role of solvent and pH is to control specific condensation reactions, especially those involving cyclization. Our results are compared with available experimental data relating to silicate species in synthesis gels.
In 2009 Ieee Sensors Vols 1 3 Ieee, Oct 1, 2009
The use of zeolites to enhance the response and discriminating power of solid state metal oxide s... more The use of zeolites to enhance the response and discriminating power of solid state metal oxide semiconductor gas sensors is demonstrated. Thick film sensors were prepared by screen printing layers of chromium titanium oxide (CTO) with various zeolites as over-layers. The sensors gas response was tested against two similar gases; ethanol and isopropyl alcohol. The modified sensors effectively discriminated between the two gases.
Journal of the Chemical Society Faraday Transactions, 1995
ABSTRACT MCM-22 with different Si/Al ratios were synthesised using hexamethylenimine as the struc... more ABSTRACT MCM-22 with different Si/Al ratios were synthesised using hexamethylenimine as the structure directing agent. The synthesised materials were characterised by XRD, BET, TGA, FT-IR, DRIFT and SEM techniques. The catalytic activity of the materials was examined in the vapour phase tert-butylation of phenol using tert-butyl alcohol as the alkylating agent. The influence of reaction parameters such as reaction temperature, reactant feed ratio, WHSV and time on stream was studied and the results are correlated with physicochemical characteristics of the catalysts. 4-tert-Butyl phenol (4-TBP) was obtained with high selectivity. It is presumed that the 10 membered ring channel present in MCM-22 might be the cause for selective production of 4-TBP.
Journal of the Chemical Society Faraday Transactions, 1998
ABSTRACT
Studies in Surface Science and Catalysis, 1995
ABSTRACT
Stud Surf Sci Catal, 1997
ABSTRACT
Studies in Surface Science and Catalysis, 2004
Periodic cell lattice energy calculations are used to study isolated Si atoms and small islands i... more Periodic cell lattice energy calculations are used to study isolated Si atoms and small islands in SAPO-31. The unique zigzag shape of the main channel provides considerable flexibility. We find that isolated acid sites preferentially occupy the 04 sites, whilst 02 and 03 are preferred when islands are considered.
Computer Modelling of Electronic and Atomic Processes in Solids, 1997
ChemInform, 2010
ABSTRACT ChemInform is a weekly Abstracting Service, delivering concise information at a glance t... more ABSTRACT ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.
Studies in Surface Science and Catalysis, 1997
ABSTRACT
Nature 382 604 606, Aug 14, 1996
THE synthesis of microporous materials such as aluminosilicates and aluminophosphates, which are ... more THE synthesis of microporous materials such as aluminosilicates and aluminophosphates, which are widely exploited as solid acid catalysts, ion exchangers and in gas separation, is facilitated by the use of structure-directing agents (often referred to as templates)1. These are generally organic bases, and are included in an inorganic gel medium so that the microporous framework condenses around them; the final structure of the framework reflects, to differing degrees, the shape of the template. Although there is growing confidence2 in being able to target a particular microporous structure by adroit choice of structure-directing agent3-7, no a priori method has been described for generating potential templates for either existing or hypothetical structures. Here we present a method for de novo design of template molecules, which are computationally 'grown' in the desired inorganic framework. Our method is successful in generating known templates for existing microporous materials, and a new candidate suggested by this method succeeds as a template for the target material. Our method should be generally applicable to the field of template-directed hydrothermal synthesis of crystals and to other fields of chemistry involving host-guest recognition.
Topic Catalysis, 1994
We investigate the surface defect chemistry of MgO and Li/MgO paying special attention to the eff... more We investigate the surface defect chemistry of MgO and Li/MgO paying special attention to the effects of added chloride ions on the active sites in the materials when used as partial oxidation catalysts. We calculate that chloride ions will segregate to the surface of these materials and will be preferentially sited at low coordinate sites. The [LiCI] defect cluster is also calculated to be bound, both of which effects will have a major influence on catalytic properties. From our calculations we also comment on the siting and selectivities of the active sites in MgO and Li/MgO.
Journal of Materials Chemistry
Static lattice simulations are presented on the microporous aluminophosphate AlPO4-5. Minimisatio... more Static lattice simulations are presented on the microporous aluminophosphate AlPO4-5. Minimisation methods together with lattice dynamical calculations are able to identify stable minima for the structure. We show, in agreement with the recent work of Henson et al., that reduction of the symmetry of the structure from P6cc to P6 leads to the relaxation of Al-O-P angles from the linear structure reported in earlier crystallographic structures. We find that the orthorhombic space group Pcc2 suggested recently by Mora et al. has only a very slightly higher energy than that calculated for the P6 structure. Differences in bond lengths and angles between the two structures are correspondingly small. We find that the inclusion of a representation of the polarisability of the oxygen in the potential model is essential in removing the linear Al-O-P angles in the simulated structures.
Studies in Surface Science and Catalysis, 2001
Studies in Surface Science and Catalysis, 2007
... REFERENCES [1] RM Barrer and EAD White, J. Chem. Soc., (1951) 1267 [2] S. Hansen and L. F lth... more ... REFERENCES [1] RM Barrer and EAD White, J. Chem. Soc., (1951) 1267 [2] S. Hansen and L. F lth, Zeolites, 2 (1982) 162 [3] CTG Knight, JP Wang and SD Kinrade, Phys. Chem. Chem. ... Int. Ed., 41 (2002) 1235. [9] M. Haouas and F. Taulelle, J. Phys. Chem. B, 110 (2006) 3007. ...
Chinese Journal of Catalysis, 2015
Chem Mater, 1996
... John Meurig Thomas. Davy Faraday Research Laboratory, The Royal Institution of GB, 21 Albemar... more ... John Meurig Thomas. Davy Faraday Research Laboratory, The Royal Institution of GB, 21 Albemarle St., London, W1X 4BS UK. Chem. Mater. ... Commun. 1993, 1861. (2) Wright, PA; Sayag, C.; Rey, F.; Lewis, DW; Gale, JD; Natarajan, S.; Thomas, JM J. Chem. Soc., Faraday Trans. ...
The Journal of Physical Chemistry, 1995
Microporous solids are industrially important materials used for catalysis, ion exchange, and gas... more Microporous solids are industrially important materials used for catalysis, ion exchange, and gas separation. Synthesis of such materials usually involves crystallization from a gel medium under hydrothermal conditions. These gels are multi-component systems containing ...
The Journal of Physical Chemistry, 1995
Page 1. J. Phys. Chem. 1995,99, 2377-2383 2377 Structure of Iron-Substituted ZSM-5 Dewi W. Lewis,... more Page 1. J. Phys. Chem. 1995,99, 2377-2383 2377 Structure of Iron-Substituted ZSM-5 Dewi W. Lewis, C. Richard A. Catlow," and Gopinathan Sankar Davy-Faraday Laboratory, The Royal Institution of Great Britain, 21 Albemarle St., London, WIX 4BS, UK ...
Stud Surf Sci Catal, 2005
Density Functional Theory calculations are used to probe the energetics of the formation of key p... more Density Functional Theory calculations are used to probe the energetics of the formation of key pre-nucleation species implicated in the formation of zeolites. We demonstrate that the role of solvent and pH is to control specific condensation reactions, especially those involving cyclization. Our results are compared with available experimental data relating to silicate species in synthesis gels.
In 2009 Ieee Sensors Vols 1 3 Ieee, Oct 1, 2009
The use of zeolites to enhance the response and discriminating power of solid state metal oxide s... more The use of zeolites to enhance the response and discriminating power of solid state metal oxide semiconductor gas sensors is demonstrated. Thick film sensors were prepared by screen printing layers of chromium titanium oxide (CTO) with various zeolites as over-layers. The sensors gas response was tested against two similar gases; ethanol and isopropyl alcohol. The modified sensors effectively discriminated between the two gases.
Journal of the Chemical Society Faraday Transactions, 1995
ABSTRACT MCM-22 with different Si/Al ratios were synthesised using hexamethylenimine as the struc... more ABSTRACT MCM-22 with different Si/Al ratios were synthesised using hexamethylenimine as the structure directing agent. The synthesised materials were characterised by XRD, BET, TGA, FT-IR, DRIFT and SEM techniques. The catalytic activity of the materials was examined in the vapour phase tert-butylation of phenol using tert-butyl alcohol as the alkylating agent. The influence of reaction parameters such as reaction temperature, reactant feed ratio, WHSV and time on stream was studied and the results are correlated with physicochemical characteristics of the catalysts. 4-tert-Butyl phenol (4-TBP) was obtained with high selectivity. It is presumed that the 10 membered ring channel present in MCM-22 might be the cause for selective production of 4-TBP.
Journal of the Chemical Society Faraday Transactions, 1998
ABSTRACT
Studies in Surface Science and Catalysis, 1995
ABSTRACT
Stud Surf Sci Catal, 1997
ABSTRACT
Studies in Surface Science and Catalysis, 2004
Periodic cell lattice energy calculations are used to study isolated Si atoms and small islands i... more Periodic cell lattice energy calculations are used to study isolated Si atoms and small islands in SAPO-31. The unique zigzag shape of the main channel provides considerable flexibility. We find that isolated acid sites preferentially occupy the 04 sites, whilst 02 and 03 are preferred when islands are considered.
Computer Modelling of Electronic and Atomic Processes in Solids, 1997
ChemInform, 2010
ABSTRACT ChemInform is a weekly Abstracting Service, delivering concise information at a glance t... more ABSTRACT ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.
Studies in Surface Science and Catalysis, 1997
ABSTRACT
Nature 382 604 606, Aug 14, 1996
THE synthesis of microporous materials such as aluminosilicates and aluminophosphates, which are ... more THE synthesis of microporous materials such as aluminosilicates and aluminophosphates, which are widely exploited as solid acid catalysts, ion exchangers and in gas separation, is facilitated by the use of structure-directing agents (often referred to as templates)1. These are generally organic bases, and are included in an inorganic gel medium so that the microporous framework condenses around them; the final structure of the framework reflects, to differing degrees, the shape of the template. Although there is growing confidence2 in being able to target a particular microporous structure by adroit choice of structure-directing agent3-7, no a priori method has been described for generating potential templates for either existing or hypothetical structures. Here we present a method for de novo design of template molecules, which are computationally 'grown' in the desired inorganic framework. Our method is successful in generating known templates for existing microporous materials, and a new candidate suggested by this method succeeds as a template for the target material. Our method should be generally applicable to the field of template-directed hydrothermal synthesis of crystals and to other fields of chemistry involving host-guest recognition.
Topic Catalysis, 1994
We investigate the surface defect chemistry of MgO and Li/MgO paying special attention to the eff... more We investigate the surface defect chemistry of MgO and Li/MgO paying special attention to the effects of added chloride ions on the active sites in the materials when used as partial oxidation catalysts. We calculate that chloride ions will segregate to the surface of these materials and will be preferentially sited at low coordinate sites. The [LiCI] defect cluster is also calculated to be bound, both of which effects will have a major influence on catalytic properties. From our calculations we also comment on the siting and selectivities of the active sites in MgO and Li/MgO.
Journal of Materials Chemistry
Static lattice simulations are presented on the microporous aluminophosphate AlPO4-5. Minimisatio... more Static lattice simulations are presented on the microporous aluminophosphate AlPO4-5. Minimisation methods together with lattice dynamical calculations are able to identify stable minima for the structure. We show, in agreement with the recent work of Henson et al., that reduction of the symmetry of the structure from P6cc to P6 leads to the relaxation of Al-O-P angles from the linear structure reported in earlier crystallographic structures. We find that the orthorhombic space group Pcc2 suggested recently by Mora et al. has only a very slightly higher energy than that calculated for the P6 structure. Differences in bond lengths and angles between the two structures are correspondingly small. We find that the inclusion of a representation of the polarisability of the oxygen in the potential model is essential in removing the linear Al-O-P angles in the simulated structures.
Studies in Surface Science and Catalysis, 2001
Studies in Surface Science and Catalysis, 2007
... REFERENCES [1] RM Barrer and EAD White, J. Chem. Soc., (1951) 1267 [2] S. Hansen and L. F lth... more ... REFERENCES [1] RM Barrer and EAD White, J. Chem. Soc., (1951) 1267 [2] S. Hansen and L. F lth, Zeolites, 2 (1982) 162 [3] CTG Knight, JP Wang and SD Kinrade, Phys. Chem. Chem. ... Int. Ed., 41 (2002) 1235. [9] M. Haouas and F. Taulelle, J. Phys. Chem. B, 110 (2006) 3007. ...
Chinese Journal of Catalysis, 2015