A theoretical-experimental study of Wells-Dawson acid. An explanation of their catalytic activity
A theoretical-experimental study about the behaviour of the protons and their interactions with water molecules on the Wells-Dawson acid and their influence on the catalytic activity was done. The Wells-Dawson acid (H6P2W18 O62·nH2O) was characterised by TGA analysis. Besides, DRIFTS and 1H MAS-NMR...
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2003
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| Acceso en línea: | https://bibliotecadigital.exactas.uba.ar/collection/paper/document/paper_13811169_v191_n1_p35_Sambeth http://hdl.handle.net/20.500.12110/paper_13811169_v191_n1_p35_Sambeth |
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paper:paper_13811169_v191_n1_p35_Sambeth2023-06-08T16:12:18Z A theoretical-experimental study of Wells-Dawson acid. An explanation of their catalytic activity DRIFTS Extended Hückel method (EHMO, ASED) Heteropolyacids Tungsten Wells-Dawson acid Dehydration Molecules Negative ions Protons Water Relative energy Catalysts acid proton unclassified drug water Wells Dawson acid acidity analytic method article calculation catalysis chemical analysis chemical bond chemical structure energy mathematical analysis molecular interaction proton nuclear magnetic resonance temperature theory A theoretical-experimental study about the behaviour of the protons and their interactions with water molecules on the Wells-Dawson acid and their influence on the catalytic activity was done. The Wells-Dawson acid (H6P2W18 O62·nH2O) was characterised by TGA analysis. Besides, DRIFTS and 1H MAS-NMR measurements as a function of acid treatment temperature were done. These experimental results, consistent with prior studies, suggest that the protonic acidity is related to the presence of water molecules in the heteropolyoxoanion (HPA) structure. In particular, the H5O2+ species associated with the last two H2O molecules determined by TGA analysis and the 1H MAS-NMR measurements show that the presence of H5O2+ species plays an important role in the acidity - catalytic activity relationship. The Wells-Dawson acid structure formation was studied by calculating the relative energy of the system. The possible acid molecular structure (P2W18O62 H6·nH2O) was analysed considering different steps by associating to the Wells-Dawson anion (P2W18O62)-6, the protons, water molecules and secondary structures. The theoretical calculus by extended Hückel method (EHMO) was done analysing the most energetically favourable positions for the protons. The theoretical results indicate that three different water species associated to the Wells-Dawson acid structure can exist. Besides, these results show that the H5O2+ species are the most energetically stable ones in the acid structure. These species bonds two secondary structures of Wells-Dawson acid leading to minimum system energy. It can be expected that these species are the last water molecules lost in the acid structure at the end of acid dehydration process. This assumption is in agreement with the results obtained with the three experimental techniques previously mentioned. © 2002 Elsevier Science B.V. All rights reserved. 2003 https://bibliotecadigital.exactas.uba.ar/collection/paper/document/paper_13811169_v191_n1_p35_Sambeth http://hdl.handle.net/20.500.12110/paper_13811169_v191_n1_p35_Sambeth |
| institution |
Universidad de Buenos Aires |
| institution_str |
I-28 |
| repository_str |
R-134 |
| collection |
Biblioteca Digital - Facultad de Ciencias Exactas y Naturales (UBA) |
| topic |
DRIFTS Extended Hückel method (EHMO, ASED) Heteropolyacids Tungsten Wells-Dawson acid Dehydration Molecules Negative ions Protons Water Relative energy Catalysts acid proton unclassified drug water Wells Dawson acid acidity analytic method article calculation catalysis chemical analysis chemical bond chemical structure energy mathematical analysis molecular interaction proton nuclear magnetic resonance temperature theory |
| spellingShingle |
DRIFTS Extended Hückel method (EHMO, ASED) Heteropolyacids Tungsten Wells-Dawson acid Dehydration Molecules Negative ions Protons Water Relative energy Catalysts acid proton unclassified drug water Wells Dawson acid acidity analytic method article calculation catalysis chemical analysis chemical bond chemical structure energy mathematical analysis molecular interaction proton nuclear magnetic resonance temperature theory A theoretical-experimental study of Wells-Dawson acid. An explanation of their catalytic activity |
| topic_facet |
DRIFTS Extended Hückel method (EHMO, ASED) Heteropolyacids Tungsten Wells-Dawson acid Dehydration Molecules Negative ions Protons Water Relative energy Catalysts acid proton unclassified drug water Wells Dawson acid acidity analytic method article calculation catalysis chemical analysis chemical bond chemical structure energy mathematical analysis molecular interaction proton nuclear magnetic resonance temperature theory |
| description |
A theoretical-experimental study about the behaviour of the protons and their interactions with water molecules on the Wells-Dawson acid and their influence on the catalytic activity was done. The Wells-Dawson acid (H6P2W18 O62·nH2O) was characterised by TGA analysis. Besides, DRIFTS and 1H MAS-NMR measurements as a function of acid treatment temperature were done. These experimental results, consistent with prior studies, suggest that the protonic acidity is related to the presence of water molecules in the heteropolyoxoanion (HPA) structure. In particular, the H5O2+ species associated with the last two H2O molecules determined by TGA analysis and the 1H MAS-NMR measurements show that the presence of H5O2+ species plays an important role in the acidity - catalytic activity relationship. The Wells-Dawson acid structure formation was studied by calculating the relative energy of the system. The possible acid molecular structure (P2W18O62 H6·nH2O) was analysed considering different steps by associating to the Wells-Dawson anion (P2W18O62)-6, the protons, water molecules and secondary structures. The theoretical calculus by extended Hückel method (EHMO) was done analysing the most energetically favourable positions for the protons. The theoretical results indicate that three different water species associated to the Wells-Dawson acid structure can exist. Besides, these results show that the H5O2+ species are the most energetically stable ones in the acid structure. These species bonds two secondary structures of Wells-Dawson acid leading to minimum system energy. It can be expected that these species are the last water molecules lost in the acid structure at the end of acid dehydration process. This assumption is in agreement with the results obtained with the three experimental techniques previously mentioned. © 2002 Elsevier Science B.V. All rights reserved. |
| title |
A theoretical-experimental study of Wells-Dawson acid. An explanation of their catalytic activity |
| title_short |
A theoretical-experimental study of Wells-Dawson acid. An explanation of their catalytic activity |
| title_full |
A theoretical-experimental study of Wells-Dawson acid. An explanation of their catalytic activity |
| title_fullStr |
A theoretical-experimental study of Wells-Dawson acid. An explanation of their catalytic activity |
| title_full_unstemmed |
A theoretical-experimental study of Wells-Dawson acid. An explanation of their catalytic activity |
| title_sort |
theoretical-experimental study of wells-dawson acid. an explanation of their catalytic activity |
| publishDate |
2003 |
| url |
https://bibliotecadigital.exactas.uba.ar/collection/paper/document/paper_13811169_v191_n1_p35_Sambeth http://hdl.handle.net/20.500.12110/paper_13811169_v191_n1_p35_Sambeth |
| _version_ |
1768542330386644992 |