INVESTIGADORES
SAMBETH jorge Enrique
artículos
Título:
A theoreticalexperimental study of WellsDawson acid
Autor/es:
SAMBETH, JORGE; BARONETTI, GRACIELA; THOMAS, HORACIO JORGE
Revista:
JOURNAL OF MOLECULAR CATALYSIS A-CHEMICAL
Editorial:
Elsevier
Referencias:
Lugar: Nederland; Año: 2003 vol. 191 p. 35 - 43
ISSN:
1381-1169
Resumen:
Abstract
A theoreticalexperimental study about the behaviour of the protons and their interactions with water molecules on the
WellsDawson acid and their influence on the catalytic activity was done. The WellsDawson acid (H6P2W18O62·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 aciditycatalytic activity relationship.
TheWellsDawson acid structure formation was studied by calculating the relative energy of the system. The possible acid
molecular structure (P2W18O62H6·nH2O) was analysed considering different steps by associating to theWellsDawson 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 WellsDawson 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
WellsDawson 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.6P2W18O62·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 aciditycatalytic activity relationship.
TheWellsDawson acid structure formation was studied by calculating the relative energy of the system. The possible acid
molecular structure (P2W18O62H6·nH2O) was analysed considering different steps by associating to theWellsDawson 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 WellsDawson 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
WellsDawson 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.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 aciditycatalytic activity relationship.
TheWellsDawson acid structure formation was studied by calculating the relative energy of the system. The possible acid
molecular structure (P2W18O62H6·nH2O) was analysed considering different steps by associating to theWellsDawson 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 WellsDawson 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
WellsDawson 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.5O2+ 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 aciditycatalytic activity relationship.
TheWellsDawson acid structure formation was studied by calculating the relative energy of the system. The possible acid
molecular structure (P2W18O62H6·nH2O) was analysed considering different steps by associating to theWellsDawson 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 WellsDawson 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
WellsDawson 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.2O molecules determined by TGA analysis and the 1H MAS-NMR measurements show that the presence
of H5O2+ species plays an important role in the aciditycatalytic activity relationship.
TheWellsDawson acid structure formation was studied by calculating the relative energy of the system. The possible acid
molecular structure (P2W18O62H6·nH2O) was analysed considering different steps by associating to theWellsDawson 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 WellsDawson 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
WellsDawson 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.5O2+ species plays an important role in the aciditycatalytic activity relationship.
TheWellsDawson acid structure formation was studied by calculating the relative energy of the system. The possible acid
molecular structure (P2W18O62H6·nH2O) was analysed considering different steps by associating to theWellsDawson 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 WellsDawson 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
WellsDawson 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.2W18O62H6·nH2O) was analysed considering different steps by associating to theWellsDawson 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 WellsDawson 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
WellsDawson 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.2W18O62)−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 WellsDawson 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
WellsDawson 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.5O2+ species are the most energetically stable ones in the acid structure. These species bonds two secondary structures of
WellsDawson 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.