Beulah Griffe - Academia.edu (original) (raw)
Papers by Beulah Griffe
Zenodo (CERN European Organization for Nuclear Research), 2017
Los cálculos químico-cuánticos se realizaron usando la metodología ONIOM2 a dos niveles de cálcul... more Los cálculos químico-cuánticos se realizaron usando la metodología ONIOM2 a dos niveles de cálculo, B3LYP (DFT) para el nivel alto y UFF (Mecánica Molecular) para el nivel bajo. Se calcularon los agregados pequeños para analizar las geometrías de Au 2-3 y Cu 2-3 soportados sobre SAPO-11. Igualmente CO-Au 2-3 /SAPO-11 y CO-Cu 2-3 /SAPO-11 obtenidos por interacción con CO y su oxidación, fueron calculados. Se reporta el cambio de energía ∆E ads de los agregados metálicos con la adsorción de CO, las distancias de enlaces CO , M-CO y las frecuencias vibracionales calculadas de C=O. Las estructuras más estables de Au 2-3 y Cu 2-3 /SAPO-11 son similares, excepto que el Au 3 exhibe una geometría triangular escaleno y Cu 3 una geometría triangular isósceles. Los valores de CO ΔE ads revelan que la adsorción de CO es más estable en Au 2-3 /SAPO-11 que en Cu 2-3 /SAPO-11. Se obtiene la oxidación de todos los CO-clúster pero la oxidación es completa sólo en el caso de Cu 2 lográndose especies oxidadas intermedias en los fragmentos Au 2 , Au 3 y Cu 3 .
Chemischer Informationsdienst, Oct 16, 1984
Acta científica venezolana, 1987
Journal of Molecular Catalysis A-chemical, Jan 2, 2010
Quantum chemistry calculations were carried out, using ONIOM2 methodology, in order to investigat... more Quantum chemistry calculations were carried out, using ONIOM2 methodology, in order to investigate the thiophene interaction with gold supported on silicoaluminophospates molecular sieves (Au/SAPO-11) catalysts. Two models were studied, one containing one ...
Applied Catalysis, Jun 1, 1984
The influence of pretreatment of a silver catalyst with carbon dioxide (CO) at high temperature i... more The influence of pretreatment of a silver catalyst with carbon dioxide (CO) at high temperature in the air oxidation of ethylene (E) to ethylene oxide (E 6) was studied separately and in conjunction with ethylene dichloride (ED). This study was done by determining the conversion (C) and selectivity (S) of the silver catalyst by gas-chromatography. The experimental results show that the pretreatment of all the silver catalysts investigated with CO at 260°C for 64 h invariably results in some deactivation of the catalysts an 5 usually in an increase in selectivity (S).
Journal of Computational Methods in Sciences and Engineering, Mar 9, 2017
Quantum chemistry calculations were carried out using the ONIOM2 methodology at two different lev... more Quantum chemistry calculations were carried out using the ONIOM2 methodology at two different levels of calculation, B3LYP for the high level and UFF for the low level. These calculations were performed on aggregates to analyze the geometries of small clusters of Au1−3 and Cu1−3 supported on SAPO-11. Similarly CO-Au1−3/SAPO-11 and CO-Cu1−3/SAPO-11 moieties obtained by their interaction with CO, were calculated and the results of both cases are compared. The formation energy ΔEF of the metal aggregates and with CO adsorption, CO and M-CO bond distances and calculated C=O stretching frequencies are reported.The most stable structures of the aggregates of Au1−3 and Cu1−3/SAPO-11 are similar, Au3 exhibits acute triangle geometry and Cu3 shows isosceles triangle with a large side geometry. The CO ΔEads values reveal that the CO adsorption is more stable in Au1−3/SAPO-11 than in Cu1−3/SAPO-11. Au-CO distances are larger than Cu-CO.
Surface Science, Nov 1, 2018
This is a PDF file of an unedited manuscript that has been accepted for publication. As a service... more This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain. Highlights DFT calculated interactions of Mo species on a pyrolytic graphite platform Calculations shed some lights on Mo adsorbed species during the ETAAS processes Molybdenum oxide species strongly bonded to pyrolytic graphite edges Mo adsorbs tightly on dehydrogenated and decarbonized sites of graphite surface Correspondence between adsorption energies of Mo species and XPS data
Computational and Theoretical Chemistry, Aug 1, 2014
SN applied sciences, Jun 29, 2020
Quantum chemistry calculations were carried out using the ONIOM2 methodology at two different lev... more Quantum chemistry calculations were carried out using the ONIOM2 methodology at two different levels of calculation, B3LYP for the high level and UFF for the low level. These calculations were performed on Cu/SAPO-11, NO-Cu/SAPO-11, NH 3-Cu/SAPO-11 and NO + NH 3-Cu/SAPO-11 to investigate the reaction pathway of the selective catalytic reduction of nitrogen oxides by ammonia in the presence of Cu/SAPO-11. NH 2 NO is formed, and then is decomposed into N 2 and H 2 O over Cu/SAPO-11 for the catalytic reduction of NO in two steps. The adsorption energy ΔE ads of NO, NH 3 on Cu/SAPO-11 and the change of energy of the reduction reaction are presented. The energy profile of the formation of NH 2 NO-Cu/ SAPO-H key intermediate is shown. Some relevant charges and bond indexes were calculated. On adsorbing NH 3 or NO on Cu/SAPO-11 there is charge transfer to the aggregates. Vibrational frequencies of adsorbed NH 3 , NO and of NH 2 NO-Cu/SAPO-11cluster are reported. The importance of adsorbing NH 3 previously to the reduction of NO is emphasized.
Journal of Computational Methods in Sciences and Engineering, Dec 3, 2012
Journal of Molecular Catalysis A-chemical, Jun 1, 2004
Journal of Computational Methods in Sciences and Engineering, Oct 19, 2009
Journal of Computational Methods in Sciences and Engineering, Mar 20, 2014
ABSTRACT Quantum chemistry calculations were done, using the ONIOM2 methodology at two different ... more ABSTRACT Quantum chemistry calculations were done, using the ONIOM2 methodology at two different levels of calculation, B3LYP for the high level and UFF for the low level. These calculations were performed on Au5/SAPO-11, Au6/SAPO-11, CO-Au5/SAPO-11 and CO-Au6/SAPO-11 aggregates to analyze the geometries of small clusters of Au5 and Au6 on SAPO-11 support. Au5 cluster presents a pentagonal structure in Au5/SAPO-11. Au6 aggregate shows a "multi triangular" structure (as from a trapezoidal "W shaped" Au5) in Au6/SAPO-11. Au5 is also obtained as an "X shaped" structure. Similarly another Au6 aggregate configuration is obtained also multi triangular but as from X shape Au5 cluster. The CO interaction with Au5 and Au6/SAPO-11 is studied. The formation energy ΔEF of the aggregates, the CO adsorption energy ΔE ads on them and CO frequency are presented.
International Journal of Quantum Chemistry, Jul 8, 2010
As Haruta et al.1 reported that gold catalytic behavior depends markedly on the type of support, ... more As Haruta et al.1 reported that gold catalytic behavior depends markedly on the type of support, degree of dispersion, and preparation method, the Au research about its use as catalyst has become of great importance and relevance. When gold is deposited on selected ...
Los cálculos químico-cuánticos se realizaron usando la metodología ONIOM2 a dos niveles de cálcul... more Los cálculos químico-cuánticos se realizaron usando la metodología ONIOM2 a dos niveles de cálculo, B3LYP (DFT) para el nivel alto y UFF (Mecánica Molecular) para el nivel bajo. Se calcularon los agregados pequeños para analizar las geometrías de Au2-3 y Cu2-3 soportados sobre SAPO-11. Igualmente CO-Au2-3/SAPO-11 y COCu2-3/SAPO-11 obtenidos por interacción con CO y su oxidación, fueron calculados. Se reporta el cambio de energía ∆Eads de los agregados metálicos con la adsorción de CO, las distancias de enlaces C-O, M-CO y las frecuencias vibracionales calculadas de C=O. Las estructuras más estables de Au2-3 y Cu2-3/SAPO-11 son similares, excepto que el Au3 exhibe una geometría triangular escaleno y Cu3 una geometría triangular isósceles.<br> Los valores de CO ΔEads revelan que la adsorción de CO es más estable en Au2-3/SAPO-11 que en Cu2-3/SAPO11. Se obtiene la oxidación de todos los CO-clúster pero la oxidación es completa sólo en el caso de Cu2 lográndose especies oxidadas i...
Journal of Computational Methods in Sciences and Engineering, 2014
ABSTRACT Quantum chemistry calculations were done, using the ONIOM2 methodology at two different ... more ABSTRACT Quantum chemistry calculations were done, using the ONIOM2 methodology at two different levels of calculation, B3LYP for the high level and UFF for the low level. These calculations were performed on Au5/SAPO-11, Au6/SAPO-11, CO-Au5/SAPO-11 and CO-Au6/SAPO-11 aggregates to analyze the geometries of small clusters of Au5 and Au6 on SAPO-11 support. Au5 cluster presents a pentagonal structure in Au5/SAPO-11. Au6 aggregate shows a "multi triangular" structure (as from a trapezoidal "W shaped" Au5) in Au6/SAPO-11. Au5 is also obtained as an "X shaped" structure. Similarly another Au6 aggregate configuration is obtained also multi triangular but as from X shape Au5 cluster. The CO interaction with Au5 and Au6/SAPO-11 is studied. The formation energy ΔEF of the aggregates, the CO adsorption energy ΔE ads on them and CO frequency are presented.
2015 27th International Conference on Microelectronics (ICM), 2015
This is your personal schedule ONLY. Registration to attend the meeting or special events and ses... more This is your personal schedule ONLY. Registration to attend the meeting or special events and sessions is required.
Resumen Este trabajo forma parte de una serie de cálculos teóricos del anclaje del Mo 2 (η 3 C 3 ... more Resumen Este trabajo forma parte de una serie de cálculos teóricos del anclaje del Mo 2 (η 3 C 3 H 5) 4 en SiO 2 . Abstract This work is one of a series of theoretical calculations of the anchoring of Mo 2 (η 3 C 3 H 5) 4 on SiO 2 . In this case, propene evolution and the formation of resulting species due to reduction are considered. The calculations were done, using the semipirical method CNDO. Interatomic distances, diatomic energies, bond orders, binding diatomic energies will be evaluated.
International Journal of Quantum Chemistry, 2008
The dimeric complex dioxo (mu-oxo) thiocyanato of molybdenum(VI) bearing a 4,4prime-di-ter-butyl-... more The dimeric complex dioxo (mu-oxo) thiocyanato of molybdenum(VI) bearing a 4,4prime-di-ter-butyl-2,2prime-bipyridine ligand in trans conformation (complex 1) has been used in catalytic reactions of olefins (ethylene) oxidation, giving as intermediate a dimeric complex oxo bis (mu-oxo) thiocyanato of molybdenum(V) in cis conformation (complex 2). Binding and electronic properties were calculated using the parametric quantum chemistry method for catalytic reactions, CATIVIC.
Zenodo (CERN European Organization for Nuclear Research), 2017
Los cálculos químico-cuánticos se realizaron usando la metodología ONIOM2 a dos niveles de cálcul... more Los cálculos químico-cuánticos se realizaron usando la metodología ONIOM2 a dos niveles de cálculo, B3LYP (DFT) para el nivel alto y UFF (Mecánica Molecular) para el nivel bajo. Se calcularon los agregados pequeños para analizar las geometrías de Au 2-3 y Cu 2-3 soportados sobre SAPO-11. Igualmente CO-Au 2-3 /SAPO-11 y CO-Cu 2-3 /SAPO-11 obtenidos por interacción con CO y su oxidación, fueron calculados. Se reporta el cambio de energía ∆E ads de los agregados metálicos con la adsorción de CO, las distancias de enlaces CO , M-CO y las frecuencias vibracionales calculadas de C=O. Las estructuras más estables de Au 2-3 y Cu 2-3 /SAPO-11 son similares, excepto que el Au 3 exhibe una geometría triangular escaleno y Cu 3 una geometría triangular isósceles. Los valores de CO ΔE ads revelan que la adsorción de CO es más estable en Au 2-3 /SAPO-11 que en Cu 2-3 /SAPO-11. Se obtiene la oxidación de todos los CO-clúster pero la oxidación es completa sólo en el caso de Cu 2 lográndose especies oxidadas intermedias en los fragmentos Au 2 , Au 3 y Cu 3 .
Chemischer Informationsdienst, Oct 16, 1984
Acta científica venezolana, 1987
Journal of Molecular Catalysis A-chemical, Jan 2, 2010
Quantum chemistry calculations were carried out, using ONIOM2 methodology, in order to investigat... more Quantum chemistry calculations were carried out, using ONIOM2 methodology, in order to investigate the thiophene interaction with gold supported on silicoaluminophospates molecular sieves (Au/SAPO-11) catalysts. Two models were studied, one containing one ...
Applied Catalysis, Jun 1, 1984
The influence of pretreatment of a silver catalyst with carbon dioxide (CO) at high temperature i... more The influence of pretreatment of a silver catalyst with carbon dioxide (CO) at high temperature in the air oxidation of ethylene (E) to ethylene oxide (E 6) was studied separately and in conjunction with ethylene dichloride (ED). This study was done by determining the conversion (C) and selectivity (S) of the silver catalyst by gas-chromatography. The experimental results show that the pretreatment of all the silver catalysts investigated with CO at 260°C for 64 h invariably results in some deactivation of the catalysts an 5 usually in an increase in selectivity (S).
Journal of Computational Methods in Sciences and Engineering, Mar 9, 2017
Quantum chemistry calculations were carried out using the ONIOM2 methodology at two different lev... more Quantum chemistry calculations were carried out using the ONIOM2 methodology at two different levels of calculation, B3LYP for the high level and UFF for the low level. These calculations were performed on aggregates to analyze the geometries of small clusters of Au1−3 and Cu1−3 supported on SAPO-11. Similarly CO-Au1−3/SAPO-11 and CO-Cu1−3/SAPO-11 moieties obtained by their interaction with CO, were calculated and the results of both cases are compared. The formation energy ΔEF of the metal aggregates and with CO adsorption, CO and M-CO bond distances and calculated C=O stretching frequencies are reported.The most stable structures of the aggregates of Au1−3 and Cu1−3/SAPO-11 are similar, Au3 exhibits acute triangle geometry and Cu3 shows isosceles triangle with a large side geometry. The CO ΔEads values reveal that the CO adsorption is more stable in Au1−3/SAPO-11 than in Cu1−3/SAPO-11. Au-CO distances are larger than Cu-CO.
Surface Science, Nov 1, 2018
This is a PDF file of an unedited manuscript that has been accepted for publication. As a service... more This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain. Highlights DFT calculated interactions of Mo species on a pyrolytic graphite platform Calculations shed some lights on Mo adsorbed species during the ETAAS processes Molybdenum oxide species strongly bonded to pyrolytic graphite edges Mo adsorbs tightly on dehydrogenated and decarbonized sites of graphite surface Correspondence between adsorption energies of Mo species and XPS data
Computational and Theoretical Chemistry, Aug 1, 2014
SN applied sciences, Jun 29, 2020
Quantum chemistry calculations were carried out using the ONIOM2 methodology at two different lev... more Quantum chemistry calculations were carried out using the ONIOM2 methodology at two different levels of calculation, B3LYP for the high level and UFF for the low level. These calculations were performed on Cu/SAPO-11, NO-Cu/SAPO-11, NH 3-Cu/SAPO-11 and NO + NH 3-Cu/SAPO-11 to investigate the reaction pathway of the selective catalytic reduction of nitrogen oxides by ammonia in the presence of Cu/SAPO-11. NH 2 NO is formed, and then is decomposed into N 2 and H 2 O over Cu/SAPO-11 for the catalytic reduction of NO in two steps. The adsorption energy ΔE ads of NO, NH 3 on Cu/SAPO-11 and the change of energy of the reduction reaction are presented. The energy profile of the formation of NH 2 NO-Cu/ SAPO-H key intermediate is shown. Some relevant charges and bond indexes were calculated. On adsorbing NH 3 or NO on Cu/SAPO-11 there is charge transfer to the aggregates. Vibrational frequencies of adsorbed NH 3 , NO and of NH 2 NO-Cu/SAPO-11cluster are reported. The importance of adsorbing NH 3 previously to the reduction of NO is emphasized.
Journal of Computational Methods in Sciences and Engineering, Dec 3, 2012
Journal of Molecular Catalysis A-chemical, Jun 1, 2004
Journal of Computational Methods in Sciences and Engineering, Oct 19, 2009
Journal of Computational Methods in Sciences and Engineering, Mar 20, 2014
ABSTRACT Quantum chemistry calculations were done, using the ONIOM2 methodology at two different ... more ABSTRACT Quantum chemistry calculations were done, using the ONIOM2 methodology at two different levels of calculation, B3LYP for the high level and UFF for the low level. These calculations were performed on Au5/SAPO-11, Au6/SAPO-11, CO-Au5/SAPO-11 and CO-Au6/SAPO-11 aggregates to analyze the geometries of small clusters of Au5 and Au6 on SAPO-11 support. Au5 cluster presents a pentagonal structure in Au5/SAPO-11. Au6 aggregate shows a "multi triangular" structure (as from a trapezoidal "W shaped" Au5) in Au6/SAPO-11. Au5 is also obtained as an "X shaped" structure. Similarly another Au6 aggregate configuration is obtained also multi triangular but as from X shape Au5 cluster. The CO interaction with Au5 and Au6/SAPO-11 is studied. The formation energy ΔEF of the aggregates, the CO adsorption energy ΔE ads on them and CO frequency are presented.
International Journal of Quantum Chemistry, Jul 8, 2010
As Haruta et al.1 reported that gold catalytic behavior depends markedly on the type of support, ... more As Haruta et al.1 reported that gold catalytic behavior depends markedly on the type of support, degree of dispersion, and preparation method, the Au research about its use as catalyst has become of great importance and relevance. When gold is deposited on selected ...
Los cálculos químico-cuánticos se realizaron usando la metodología ONIOM2 a dos niveles de cálcul... more Los cálculos químico-cuánticos se realizaron usando la metodología ONIOM2 a dos niveles de cálculo, B3LYP (DFT) para el nivel alto y UFF (Mecánica Molecular) para el nivel bajo. Se calcularon los agregados pequeños para analizar las geometrías de Au2-3 y Cu2-3 soportados sobre SAPO-11. Igualmente CO-Au2-3/SAPO-11 y COCu2-3/SAPO-11 obtenidos por interacción con CO y su oxidación, fueron calculados. Se reporta el cambio de energía ∆Eads de los agregados metálicos con la adsorción de CO, las distancias de enlaces C-O, M-CO y las frecuencias vibracionales calculadas de C=O. Las estructuras más estables de Au2-3 y Cu2-3/SAPO-11 son similares, excepto que el Au3 exhibe una geometría triangular escaleno y Cu3 una geometría triangular isósceles.<br> Los valores de CO ΔEads revelan que la adsorción de CO es más estable en Au2-3/SAPO-11 que en Cu2-3/SAPO11. Se obtiene la oxidación de todos los CO-clúster pero la oxidación es completa sólo en el caso de Cu2 lográndose especies oxidadas i...
Journal of Computational Methods in Sciences and Engineering, 2014
ABSTRACT Quantum chemistry calculations were done, using the ONIOM2 methodology at two different ... more ABSTRACT Quantum chemistry calculations were done, using the ONIOM2 methodology at two different levels of calculation, B3LYP for the high level and UFF for the low level. These calculations were performed on Au5/SAPO-11, Au6/SAPO-11, CO-Au5/SAPO-11 and CO-Au6/SAPO-11 aggregates to analyze the geometries of small clusters of Au5 and Au6 on SAPO-11 support. Au5 cluster presents a pentagonal structure in Au5/SAPO-11. Au6 aggregate shows a "multi triangular" structure (as from a trapezoidal "W shaped" Au5) in Au6/SAPO-11. Au5 is also obtained as an "X shaped" structure. Similarly another Au6 aggregate configuration is obtained also multi triangular but as from X shape Au5 cluster. The CO interaction with Au5 and Au6/SAPO-11 is studied. The formation energy ΔEF of the aggregates, the CO adsorption energy ΔE ads on them and CO frequency are presented.
2015 27th International Conference on Microelectronics (ICM), 2015
This is your personal schedule ONLY. Registration to attend the meeting or special events and ses... more This is your personal schedule ONLY. Registration to attend the meeting or special events and sessions is required.
Resumen Este trabajo forma parte de una serie de cálculos teóricos del anclaje del Mo 2 (η 3 C 3 ... more Resumen Este trabajo forma parte de una serie de cálculos teóricos del anclaje del Mo 2 (η 3 C 3 H 5) 4 en SiO 2 . Abstract This work is one of a series of theoretical calculations of the anchoring of Mo 2 (η 3 C 3 H 5) 4 on SiO 2 . In this case, propene evolution and the formation of resulting species due to reduction are considered. The calculations were done, using the semipirical method CNDO. Interatomic distances, diatomic energies, bond orders, binding diatomic energies will be evaluated.
International Journal of Quantum Chemistry, 2008
The dimeric complex dioxo (mu-oxo) thiocyanato of molybdenum(VI) bearing a 4,4prime-di-ter-butyl-... more The dimeric complex dioxo (mu-oxo) thiocyanato of molybdenum(VI) bearing a 4,4prime-di-ter-butyl-2,2prime-bipyridine ligand in trans conformation (complex 1) has been used in catalytic reactions of olefins (ethylene) oxidation, giving as intermediate a dimeric complex oxo bis (mu-oxo) thiocyanato of molybdenum(V) in cis conformation (complex 2). Binding and electronic properties were calculated using the parametric quantum chemistry method for catalytic reactions, CATIVIC.