INVESTIGADORES
PADRO Cristina Liliana
artículos
Título:
Comparative Study of n-Hexane Aromatization on Pt/KL, Pt/Mg(Al)O, and Pt/SiO2 Catalysts: Clean and Sulfur-Containing Feed
Autor/es:
G. JACOBS, C. L. PADRO, AND D.E. RESASCO
Revista:
JOURNAL OF CATALYSIS
Editorial:
Elsevier
Referencias:
Año: 1998 vol. 179 p. 43 - 55
ISSN:
0021-9517
Resumen:
The n-hexane aromatization has been studied on Pt/KL, Pt/
Mg(Al)O, and Pt/SiO2 catalysts at 773 K using sulfur-free and
0.6 ppm sulfur containing feedstocks. Examination of the product
distribution as a function of conversion suggests that the formation
of benzene is preceded by the formation of hexenes. In contrast
with previous reports, it has been found that the Pt/KL catalyst
exhibits much higher aromatization activity than the Pt/Mg(Al)O
catalyst. On Pt/KL the main product is benzene, with hexenes and
lighter compounds as the principal by-products. By contrast, on the
Pt/Mg(Al)O, the main products were hexenes. Since hexenes are primary
products and benzene is a secondary product, the exceptional
aromatization activity of Pt/KL is explained in terms of its ability
to convert hexene into benzene. In the presence of sulfur, the Pt/KL
exhibits a rapid loss in n-hexane conversion and benzene selectivity.
Under these conditions, the sulfided Pt/KL catalyst presents a catalytic
behavior typical of Pt/Mg(Al)O and Pt/SiO2, generating larger
amounts of hexenes. The observed results are consistent with the
hypothesis that the most important role of the zeolite is to inhibit
bimolecular interactions that lead to coke formation. The formation
of coke has the net effect of selectively deactivating aromatization
sites which require a large ensemble of atoms to constitute the active
site but not affecting the dehydrogenation activity which is less
ensemble-sensitive. Therefore, those particles that are not protected
against coking inside the channels of the zeolite rapidly become unselective.
In support of this hypothesis, the hydrogenolysis reaction
which also requires a large ensemble of atoms, decreases in parallel
with the aromatization reaction. The high sensitivity of Pt/KL to
sulfur may be due to a combination of effects which may involve
growth of metal particles outside the zeolite which would become
unselective and partial poisoning of the particles inside the zeolite,
causing a similar selective deactivation.
amounts of hexenes. The observed results are consistent with the
hypothesis that the most important role of the zeolite is to inhibit
bimolecular interactions that lead to coke formation. The formation
of coke has the net effect of selectively deactivating aromatization
sites which require a large ensemble of atoms to constitute the active
site but not affecting the dehydrogenation activity which is less
ensemble-sensitive. Therefore, those particles that are not protected
against coking inside the channels of the zeolite rapidly become unselective.
In support of this hypothesis, the hydrogenolysis reaction
which also requires a large ensemble of atoms, decreases in parallel
with the aromatization reaction. The high sensitivity of Pt/KL to
sulfur may be due to a combination of effects which may involve
growth of metal particles outside the zeolite which would become
unselective and partial poisoning of the particles inside the zeolite,
causing a similar selective deactivation.
Under these conditions, the sulfided Pt/KL catalyst presents a catalytic
behavior typical of Pt/Mg(Al)O and Pt/SiO2, generating larger
amounts of hexenes. The observed results are consistent with the
hypothesis that the most important role of the zeolite is to inhibit
bimolecular interactions that lead to coke formation. The formation
of coke has the net effect of selectively deactivating aromatization
sites which require a large ensemble of atoms to constitute the active
site but not affecting the dehydrogenation activity which is less
ensemble-sensitive. Therefore, those particles that are not protected
against coking inside the channels of the zeolite rapidly become unselective.
In support of this hypothesis, the hydrogenolysis reaction
which also requires a large ensemble of atoms, decreases in parallel
with the aromatization reaction. The high sensitivity of Pt/KL to
sulfur may be due to a combination of effects which may involve
growth of metal particles outside the zeolite which would become
unselective and partial poisoning of the particles inside the zeolite,
causing a similar selective deactivation.
amounts of hexenes. The observed results are consistent with the
hypothesis that the most important role of the zeolite is to inhibit
bimolecular interactions that lead to coke formation. The formation
of coke has the net effect of selectively deactivating aromatization
sites which require a large ensemble of atoms to constitute the active
site but not affecting the dehydrogenation activity which is less
ensemble-sensitive. Therefore, those particles that are not protected
against coking inside the channels of the zeolite rapidly become unselective.
In support of this hypothesis, the hydrogenolysis reaction
which also requires a large ensemble of atoms, decreases in parallel
with the aromatization reaction. The high sensitivity of Pt/KL to
sulfur may be due to a combination of effects which may involve
growth of metal particles outside the zeolite which would become
unselective and partial poisoning of the particles inside the zeolite,
causing a similar selective deactivation.
0.6 ppm sulfur containing feedstocks. Examination of the product
distribution as a function of conversion suggests that the formation
of benzene is preceded by the formation of hexenes. In contrast
with previous reports, it has been found that the Pt/KL catalyst
exhibits much higher aromatization activity than the Pt/Mg(Al)O
catalyst. On Pt/KL the main product is benzene, with hexenes and
lighter compounds as the principal by-products. By contrast, on the
Pt/Mg(Al)O, the main products were hexenes. Since hexenes are primary
products and benzene is a secondary product, the exceptional
aromatization activity of Pt/KL is explained in terms of its ability
to convert hexene into benzene. In the presence of sulfur, the Pt/KL
exhibits a rapid loss in n-hexane conversion and benzene selectivity.
Under these conditions, the sulfided Pt/KL catalyst presents a catalytic
behavior typical of Pt/Mg(Al)O and Pt/SiO2, generating larger
amounts of hexenes. The observed results are consistent with the
hypothesis that the most important role of the zeolite is to inhibit
bimolecular interactions that lead to coke formation. The formation
of coke has the net effect of selectively deactivating aromatization
sites which require a large ensemble of atoms to constitute the active
site but not affecting the dehydrogenation activity which is less
ensemble-sensitive. Therefore, those particles that are not protected
against coking inside the channels of the zeolite rapidly become unselective.
In support of this hypothesis, the hydrogenolysis reaction
which also requires a large ensemble of atoms, decreases in parallel
with the aromatization reaction. The high sensitivity of Pt/KL to
sulfur may be due to a combination of effects which may involve
growth of metal particles outside the zeolite which would become
unselective and partial poisoning of the particles inside the zeolite,
causing a similar selective deactivation.
amounts of hexenes. The observed results are consistent with the
hypothesis that the most important role of the zeolite is to inhibit
bimolecular interactions that lead to coke formation. The formation
of coke has the net effect of selectively deactivating aromatization
sites which require a large ensemble of atoms to constitute the active
site but not affecting the dehydrogenation activity which is less
ensemble-sensitive. Therefore, those particles that are not protected
against coking inside the channels of the zeolite rapidly become unselective.
In support of this hypothesis, the hydrogenolysis reaction
which also requires a large ensemble of atoms, decreases in parallel
with the aromatization reaction. The high sensitivity of Pt/KL to
sulfur may be due to a combination of effects which may involve
growth of metal particles outside the zeolite which would become
unselective and partial poisoning of the particles inside the zeolite,
causing a similar selective deactivation.
Under these conditions, the sulfided Pt/KL catalyst presents a catalytic
behavior typical of Pt/Mg(Al)O and Pt/SiO2, generating larger
amounts of hexenes. The observed results are consistent with the
hypothesis that the most important role of the zeolite is to inhibit
bimolecular interactions that lead to coke formation. The formation
of coke has the net effect of selectively deactivating aromatization
sites which require a large ensemble of atoms to constitute the active
site but not affecting the dehydrogenation activity which is less
ensemble-sensitive. Therefore, those particles that are not protected
against coking inside the channels of the zeolite rapidly become unselective.
In support of this hypothesis, the hydrogenolysis reaction
which also requires a large ensemble of atoms, decreases in parallel
with the aromatization reaction. The high sensitivity of Pt/KL to
sulfur may be due to a combination of effects which may involve
growth of metal particles outside the zeolite which would become
unselective and partial poisoning of the particles inside the zeolite,
causing a similar selective deactivation.
amounts of hexenes. The observed results are consistent with the
hypothesis that the most important role of the zeolite is to inhibit
bimolecular interactions that lead to coke formation. The formation
of coke has the net effect of selectively deactivating aromatization
sites which require a large ensemble of atoms to constitute the active
site but not affecting the dehydrogenation activity which is less
ensemble-sensitive. Therefore, those particles that are not protected
against coking inside the channels of the zeolite rapidly become unselective.
In support of this hypothesis, the hydrogenolysis reaction
which also requires a large ensemble of atoms, decreases in parallel
with the aromatization reaction. The high sensitivity of Pt/KL to
sulfur may be due to a combination of effects which may involve
growth of metal particles outside the zeolite which would become
unselective and partial poisoning of the particles inside the zeolite,
causing a similar selective deactivation.
Mg(Al)O, and Pt/SiO2 catalysts at 773 K using sulfur-free and
0.6 ppm sulfur containing feedstocks. Examination of the product
distribution as a function of conversion suggests that the formation
of benzene is preceded by the formation of hexenes. In contrast
with previous reports, it has been found that the Pt/KL catalyst
exhibits much higher aromatization activity than the Pt/Mg(Al)O
catalyst. On Pt/KL the main product is benzene, with hexenes and
lighter compounds as the principal by-products. By contrast, on the
Pt/Mg(Al)O, the main products were hexenes. Since hexenes are primary
products and benzene is a secondary product, the exceptional
aromatization activity of Pt/KL is explained in terms of its ability
to convert hexene into benzene. In the presence of sulfur, the Pt/KL
exhibits a rapid loss in n-hexane conversion and benzene selectivity.
Under these conditions, the sulfided Pt/KL catalyst presents a catalytic
behavior typical of Pt/Mg(Al)O and Pt/SiO2, generating larger
amounts of hexenes. The observed results are consistent with the
hypothesis that the most important role of the zeolite is to inhibit
bimolecular interactions that lead to coke formation. The formation
of coke has the net effect of selectively deactivating aromatization
sites which require a large ensemble of atoms to constitute the active
site but not affecting the dehydrogenation activity which is less
ensemble-sensitive. Therefore, those particles that are not protected
against coking inside the channels of the zeolite rapidly become unselective.
In support of this hypothesis, the hydrogenolysis reaction
which also requires a large ensemble of atoms, decreases in parallel
with the aromatization reaction. The high sensitivity of Pt/KL to
sulfur may be due to a combination of effects which may involve
growth of metal particles outside the zeolite which would become
unselective and partial poisoning of the particles inside the zeolite,
causing a similar selective deactivation.
amounts of hexenes. The observed results are consistent with the
hypothesis that the most important role of the zeolite is to inhibit
bimolecular interactions that lead to coke formation. The formation
of coke has the net effect of selectively deactivating aromatization
sites which require a large ensemble of atoms to constitute the active
site but not affecting the dehydrogenation activity which is less
ensemble-sensitive. Therefore, those particles that are not protected
against coking inside the channels of the zeolite rapidly become unselective.
In support of this hypothesis, the hydrogenolysis reaction
which also requires a large ensemble of atoms, decreases in parallel
with the aromatization reaction. The high sensitivity of Pt/KL to
sulfur may be due to a combination of effects which may involve
growth of metal particles outside the zeolite which would become
unselective and partial poisoning of the particles inside the zeolite,
causing a similar selective deactivation.
Under these conditions, the sulfided Pt/KL catalyst presents a catalytic
behavior typical of Pt/Mg(Al)O and Pt/SiO2, generating larger
amounts of hexenes. The observed results are consistent with the
hypothesis that the most important role of the zeolite is to inhibit
bimolecular interactions that lead to coke formation. The formation
of coke has the net effect of selectively deactivating aromatization
sites which require a large ensemble of atoms to constitute the active
site but not affecting the dehydrogenation activity which is less
ensemble-sensitive. Therefore, those particles that are not protected
against coking inside the channels of the zeolite rapidly become unselective.
In support of this hypothesis, the hydrogenolysis reaction
which also requires a large ensemble of atoms, decreases in parallel
with the aromatization reaction. The high sensitivity of Pt/KL to
sulfur may be due to a combination of effects which may involve
growth of metal particles outside the zeolite which would become
unselective and partial poisoning of the particles inside the zeolite,
causing a similar selective deactivation.
amounts of hexenes. The observed results are consistent with the
hypothesis that the most important role of the zeolite is to inhibit
bimolecular interactions that lead to coke formation. The formation
of coke has the net effect of selectively deactivating aromatization
sites which require a large ensemble of atoms to constitute the active
site but not affecting the dehydrogenation activity which is less
ensemble-sensitive. Therefore, those particles that are not protected
against coking inside the channels of the zeolite rapidly become unselective.
In support of this hypothesis, the hydrogenolysis reaction
which also requires a large ensemble of atoms, decreases in parallel
with the aromatization reaction. The high sensitivity of Pt/KL to
sulfur may be due to a combination of effects which may involve
growth of metal particles outside the zeolite which would become
unselective and partial poisoning of the particles inside the zeolite,
causing a similar selective deactivation.
0.6 ppm sulfur containing feedstocks. Examination of the product
distribution as a function of conversion suggests that the formation
of benzene is preceded by the formation of hexenes. In contrast
with previous reports, it has been found that the Pt/KL catalyst
exhibits much higher aromatization activity than the Pt/Mg(Al)O
catalyst. On Pt/KL the main product is benzene, with hexenes and
lighter compounds as the principal by-products. By contrast, on the
Pt/Mg(Al)O, the main products were hexenes. Since hexenes are primary
products and benzene is a secondary product, the exceptional
aromatization activity of Pt/KL is explained in terms of its ability
to convert hexene into benzene. In the presence of sulfur, the Pt/KL
exhibits a rapid loss in n-hexane conversion and benzene selectivity.
Under these conditions, the sulfided Pt/KL catalyst presents a catalytic
behavior typical of Pt/Mg(Al)O and Pt/SiO2, generating larger
amounts of hexenes. The observed results are consistent with the
hypothesis that the most important role of the zeolite is to inhibit
bimolecular interactions that lead to coke formation. The formation
of coke has the net effect of selectively deactivating aromatization
sites which require a large ensemble of atoms to constitute the active
site but not affecting the dehydrogenation activity which is less
ensemble-sensitive. Therefore, those particles that are not protected
against coking inside the channels of the zeolite rapidly become unselective.
In support of this hypothesis, the hydrogenolysis reaction
which also requires a large ensemble of atoms, decreases in parallel
with the aromatization reaction. The high sensitivity of Pt/KL to
sulfur may be due to a combination of effects which may involve
growth of metal particles outside the zeolite which would become
unselective and partial poisoning of the particles inside the zeolite,
causing a similar selective deactivation.
amounts of hexenes. The observed results are consistent with the
hypothesis that the most important role of the zeolite is to inhibit
bimolecular interactions that lead to coke formation. The formation
of coke has the net effect of selectively deactivating aromatization
sites which require a large ensemble of atoms to constitute the active
site but not affecting the dehydrogenation activity which is less
ensemble-sensitive. Therefore, those particles that are not protected
against coking inside the channels of the zeolite rapidly become unselective.
In support of this hypothesis, the hydrogenolysis reaction
which also requires a large ensemble of atoms, decreases in parallel
with the aromatization reaction. The high sensitivity of Pt/KL to
sulfur may be due to a combination of effects which may involve
growth of metal particles outside the zeolite which would become
unselective and partial poisoning of the particles inside the zeolite,
causing a similar selective deactivation.
Under these conditions, the sulfided Pt/KL catalyst presents a catalytic
behavior typical of Pt/Mg(Al)O and Pt/SiO2, generating larger
amounts of hexenes. The observed results are consistent with the
hypothesis that the most important role of the zeolite is to inhibit
bimolecular interactions that lead to coke formation. The formation
of coke has the net effect of selectively deactivating aromatization
sites which require a large ensemble of atoms to constitute the active
site but not affecting the dehydrogenation activity which is less
ensemble-sensitive. Therefore, those particles that are not protected
against coking inside the channels of the zeolite rapidly become unselective.
In support of this hypothesis, the hydrogenolysis reaction
which also requires a large ensemble of atoms, decreases in parallel
with the aromatization reaction. The high sensitivity of Pt/KL to
sulfur may be due to a combination of effects which may involve
growth of metal particles outside the zeolite which would become
unselective and partial poisoning of the particles inside the zeolite,
causing a similar selective deactivation.
amounts of hexenes. The observed results are consistent with the
hypothesis that the most important role of the zeolite is to inhibit
bimolecular interactions that lead to coke formation. The formation
of coke has the net effect of selectively deactivating aromatization
sites which require a large ensemble of atoms to constitute the active
site but not affecting the dehydrogenation activity which is less
ensemble-sensitive. Therefore, those particles that are not protected
against coking inside the channels of the zeolite rapidly become unselective.
In support of this hypothesis, the hydrogenolysis reaction
which also requires a large ensemble of atoms, decreases in parallel
with the aromatization reaction. The high sensitivity of Pt/KL to
sulfur may be due to a combination of effects which may involve
growth of metal particles outside the zeolite which would become
unselective and partial poisoning of the particles inside the zeolite,
causing a similar selective deactivation.
n-hexane aromatization has been studied on Pt/KL, Pt/
Mg(Al)O, and Pt/SiO2 catalysts at 773 K using sulfur-free and
0.6 ppm sulfur containing feedstocks. Examination of the product
distribution as a function of conversion suggests that the formation
of benzene is preceded by the formation of hexenes. In contrast
with previous reports, it has been found that the Pt/KL catalyst
exhibits much higher aromatization activity than the Pt/Mg(Al)O
catalyst. On Pt/KL the main product is benzene, with hexenes and
lighter compounds as the principal by-products. By contrast, on the
Pt/Mg(Al)O, the main products were hexenes. Since hexenes are primary
products and benzene is a secondary product, the exceptional
aromatization activity of Pt/KL is explained in terms of its ability
to convert hexene into benzene. In the presence of sulfur, the Pt/KL
exhibits a rapid loss in n-hexane conversion and benzene selectivity.
Under these conditions, the sulfided Pt/KL catalyst presents a catalytic
behavior typical of Pt/Mg(Al)O and Pt/SiO2, generating larger
amounts of hexenes. The observed results are consistent with the
hypothesis that the most important role of the zeolite is to inhibit
bimolecular interactions that lead to coke formation. The formation
of coke has the net effect of selectively deactivating aromatization
sites which require a large ensemble of atoms to constitute the active
site but not affecting the dehydrogenation activity which is less
ensemble-sensitive. Therefore, those particles that are not protected
against coking inside the channels of the zeolite rapidly become unselective.
In support of this hypothesis, the hydrogenolysis reaction
which also requires a large ensemble of atoms, decreases in parallel
with the aromatization reaction. The high sensitivity of Pt/KL to
sulfur may be due to a combination of effects which may involve
growth of metal particles outside the zeolite which would become
unselective and partial poisoning of the particles inside the zeolite,
causing a similar selective deactivation.
amounts of hexenes. The observed results are consistent with the
hypothesis that the most important role of the zeolite is to inhibit
bimolecular interactions that lead to coke formation. The formation
of coke has the net effect of selectively deactivating aromatization
sites which require a large ensemble of atoms to constitute the active
site but not affecting the dehydrogenation activity which is less
ensemble-sensitive. Therefore, those particles that are not protected
against coking inside the channels of the zeolite rapidly become unselective.
In support of this hypothesis, the hydrogenolysis reaction
which also requires a large ensemble of atoms, decreases in parallel
with the aromatization reaction. The high sensitivity of Pt/KL to
sulfur may be due to a combination of effects which may involve
growth of metal particles outside the zeolite which would become
unselective and partial poisoning of the particles inside the zeolite,
causing a similar selective deactivation.
Under these conditions, the sulfided Pt/KL catalyst presents a catalytic
behavior typical of Pt/Mg(Al)O and Pt/SiO2, generating larger
amounts of hexenes. The observed results are consistent with the
hypothesis that the most important role of the zeolite is to inhibit
bimolecular interactions that lead to coke formation. The formation
of coke has the net effect of selectively deactivating aromatization
sites which require a large ensemble of atoms to constitute the active
site but not affecting the dehydrogenation activity which is less
ensemble-sensitive. Therefore, those particles that are not protected
against coking inside the channels of the zeolite rapidly become unselective.
In support of this hypothesis, the hydrogenolysis reaction
which also requires a large ensemble of atoms, decreases in parallel
with the aromatization reaction. The high sensitivity of Pt/KL to
sulfur may be due to a combination of effects which may involve
growth of metal particles outside the zeolite which would become
unselective and partial poisoning of the particles inside the zeolite,
causing a similar selective deactivation.
amounts of hexenes. The observed results are consistent with the
hypothesis that the most important role of the zeolite is to inhibit
bimolecular interactions that lead to coke formation. The formation
of coke has the net effect of selectively deactivating aromatization
sites which require a large ensemble of atoms to constitute the active
site but not affecting the dehydrogenation activity which is less
ensemble-sensitive. Therefore, those particles that are not protected
against coking inside the channels of the zeolite rapidly become unselective.
In support of this hypothesis, the hydrogenolysis reaction
which also requires a large ensemble of atoms, decreases in parallel
with the aromatization reaction. The high sensitivity of Pt/KL to
sulfur may be due to a combination of effects which may involve
growth of metal particles outside the zeolite which would become
unselective and partial poisoning of the particles inside the zeolite,
causing a similar selective deactivation.
0.6 ppm sulfur containing feedstocks. Examination of the product
distribution as a function of conversion suggests that the formation
of benzene is preceded by the formation of hexenes. In contrast
with previous reports, it has been found that the Pt/KL catalyst
exhibits much higher aromatization activity than the Pt/Mg(Al)O
catalyst. On Pt/KL the main product is benzene, with hexenes and
lighter compounds as the principal by-products. By contrast, on the
Pt/Mg(Al)O, the main products were hexenes. Since hexenes are primary
products and benzene is a secondary product, the exceptional
aromatization activity of Pt/KL is explained in terms of its ability
to convert hexene into benzene. In the presence of sulfur, the Pt/KL
exhibits a rapid loss in n-hexane conversion and benzene selectivity.
Under these conditions, the sulfided Pt/KL catalyst presents a catalytic
behavior typical of Pt/Mg(Al)O and Pt/SiO2, generating larger
amounts of hexenes. The observed results are consistent with the
hypothesis that the most important role of the zeolite is to inhibit
bimolecular interactions that lead to coke formation. The formation
of coke has the net effect of selectively deactivating aromatization
sites which require a large ensemble of atoms to constitute the active
site but not affecting the dehydrogenation activity which is less
ensemble-sensitive. Therefore, those particles that are not protected
against coking inside the channels of the zeolite rapidly become unselective.
In support of this hypothesis, the hydrogenolysis reaction
which also requires a large ensemble of atoms, decreases in parallel
with the aromatization reaction. The high sensitivity of Pt/KL to
sulfur may be due to a combination of effects which may involve
growth of metal particles outside the zeolite which would become
unselective and partial poisoning of the particles inside the zeolite,
causing a similar selective deactivation.
amounts of hexenes. The observed results are consistent with the
hypothesis that the most important role of the zeolite is to inhibit
bimolecular interactions that lead to coke formation. The formation
of coke has the net effect of selectively deactivating aromatization
sites which require a large ensemble of atoms to constitute the active
site but not affecting the dehydrogenation activity which is less
ensemble-sensitive. Therefore, those particles that are not protected
against coking inside the channels of the zeolite rapidly become unselective.
In support of this hypothesis, the hydrogenolysis reaction
which also requires a large ensemble of atoms, decreases in parallel
with the aromatization reaction. The high sensitivity of Pt/KL to
sulfur may be due to a combination of effects which may involve
growth of metal particles outside the zeolite which would become
unselective and partial poisoning of the particles inside the zeolite,
causing a similar selective deactivation.
Under these conditions, the sulfided Pt/KL catalyst presents a catalytic
behavior typical of Pt/Mg(Al)O and Pt/SiO2, generating larger
amounts of hexenes. The observed results are consistent with the
hypothesis that the most important role of the zeolite is to inhibit
bimolecular interactions that lead to coke formation. The formation
of coke has the net effect of selectively deactivating aromatization
sites which require a large ensemble of atoms to constitute the active
site but not affecting the dehydrogenation activity which is less
ensemble-sensitive. Therefore, those particles that are not protected
against coking inside the channels of the zeolite rapidly become unselective.
In support of this hypothesis, the hydrogenolysis reaction
which also requires a large ensemble of atoms, decreases in parallel
with the aromatization reaction. The high sensitivity of Pt/KL to
sulfur may be due to a combination of effects which may involve
growth of metal particles outside the zeolite which would become
unselective and partial poisoning of the particles inside the zeolite,
causing a similar selective deactivation.
amounts of hexenes. The observed results are consistent with the
hypothesis that the most important role of the zeolite is to inhibit
bimolecular interactions that lead to coke formation. The formation
of coke has the net effect of selectively deactivating aromatization
sites which require a large ensemble of atoms to constitute the active
site but not affecting the dehydrogenation activity which is less
ensemble-sensitive. Therefore, those particles that are not protected
against coking inside the channels of the zeolite rapidly become unselective.
In support of this hypothesis, the hydrogenolysis reaction
which also requires a large ensemble of atoms, decreases in parallel
with the aromatization reaction. The high sensitivity of Pt/KL to
sulfur may be due to a combination of effects which may involve
growth of metal particles outside the zeolite which would become
unselective and partial poisoning of the particles inside the zeolite,
causing a similar selective deactivation.
2 catalysts at 773 K using sulfur-free and
0.6 ppm sulfur containing feedstocks. Examination of the product
distribution as a function of conversion suggests that the formation
of benzene is preceded by the formation of hexenes. In contrast
with previous reports, it has been found that the Pt/KL catalyst
exhibits much higher aromatization activity than the Pt/Mg(Al)O
catalyst. On Pt/KL the main product is benzene, with hexenes and
lighter compounds as the principal by-products. By contrast, on the
Pt/Mg(Al)O, the main products were hexenes. Since hexenes are primary
products and benzene is a secondary product, the exceptional
aromatization activity of Pt/KL is explained in terms of its ability
to convert hexene into benzene. In the presence of sulfur, the Pt/KL
exhibits a rapid loss in n-hexane conversion and benzene selectivity.
Under these conditions, the sulfided Pt/KL catalyst presents a catalytic
behavior typical of Pt/Mg(Al)O and Pt/SiO2, generating larger
amounts of hexenes. The observed results are consistent with the
hypothesis that the most important role of the zeolite is to inhibit
bimolecular interactions that lead to coke formation. The formation
of coke has the net effect of selectively deactivating aromatization
sites which require a large ensemble of atoms to constitute the active
site but not affecting the dehydrogenation activity which is less
ensemble-sensitive. Therefore, those particles that are not protected
against coking inside the channels of the zeolite rapidly become unselective.
In support of this hypothesis, the hydrogenolysis reaction
which also requires a large ensemble of atoms, decreases in parallel
with the aromatization reaction. The high sensitivity of Pt/KL to
sulfur may be due to a combination of effects which may involve
growth of metal particles outside the zeolite which would become
unselective and partial poisoning of the particles inside the zeolite,
causing a similar selective deactivation.
amounts of hexenes. The observed results are consistent with the
hypothesis that the most important role of the zeolite is to inhibit
bimolecular interactions that lead to coke formation. The formation
of coke has the net effect of selectively deactivating aromatization
sites which require a large ensemble of atoms to constitute the active
site but not affecting the dehydrogenation activity which is less
ensemble-sensitive. Therefore, those particles that are not protected
against coking inside the channels of the zeolite rapidly become unselective.
In support of this hypothesis, the hydrogenolysis reaction
which also requires a large ensemble of atoms, decreases in parallel
with the aromatization reaction. The high sensitivity of Pt/KL to
sulfur may be due to a combination of effects which may involve
growth of metal particles outside the zeolite which would become
unselective and partial poisoning of the particles inside the zeolite,
causing a similar selective deactivation.
Under these conditions, the sulfided Pt/KL catalyst presents a catalytic
behavior typical of Pt/Mg(Al)O and Pt/SiO2, generating larger
amounts of hexenes. The observed results are consistent with the
hypothesis that the most important role of the zeolite is to inhibit
bimolecular interactions that lead to coke formation. The formation
of coke has the net effect of selectively deactivating aromatization
sites which require a large ensemble of atoms to constitute the active
site but not affecting the dehydrogenation activity which is less
ensemble-sensitive. Therefore, those particles that are not protected
against coking inside the channels of the zeolite rapidly become unselective.
In support of this hypothesis, the hydrogenolysis reaction
which also requires a large ensemble of atoms, decreases in parallel
with the aromatization reaction. The high sensitivity of Pt/KL to
sulfur may be due to a combination of effects which may involve
growth of metal particles outside the zeolite which would become
unselective and partial poisoning of the particles inside the zeolite,
causing a similar selective deactivation.
amounts of hexenes. The observed results are consistent with the
hypothesis that the most important role of the zeolite is to inhibit
bimolecular interactions that lead to coke formation. The formation
of coke has the net effect of selectively deactivating aromatization
sites which require a large ensemble of atoms to constitute the active
site but not affecting the dehydrogenation activity which is less
ensemble-sensitive. Therefore, those particles that are not protected
against coking inside the channels of the zeolite rapidly become unselective.
In support of this hypothesis, the hydrogenolysis reaction
which also requires a large ensemble of atoms, decreases in parallel
with the aromatization reaction. The high sensitivity of Pt/KL to
sulfur may be due to a combination of effects which may involve
growth of metal particles outside the zeolite which would become
unselective and partial poisoning of the particles inside the zeolite,
causing a similar selective deactivation.
n-hexane conversion and benzene selectivity.
Under these conditions, the sulfided Pt/KL catalyst presents a catalytic
behavior typical of Pt/Mg(Al)O and Pt/SiO2, generating larger
amounts of hexenes. The observed results are consistent with the
hypothesis that the most important role of the zeolite is to inhibit
bimolecular interactions that lead to coke formation. The formation
of coke has the net effect of selectively deactivating aromatization
sites which require a large ensemble of atoms to constitute the active
site but not affecting the dehydrogenation activity which is less
ensemble-sensitive. Therefore, those particles that are not protected
against coking inside the channels of the zeolite rapidly become unselective.
In support of this hypothesis, the hydrogenolysis reaction
which also requires a large ensemble of atoms, decreases in parallel
with the aromatization reaction. The high sensitivity of Pt/KL to
sulfur may be due to a combination of effects which may involve
growth of metal particles outside the zeolite which would become
unselective and partial poisoning of the particles inside the zeolite,
causing a similar selective deactivation.
amounts of hexenes. The observed results are consistent with the
hypothesis that the most important role of the zeolite is to inhibit
bimolecular interactions that lead to coke formation. The formation
of coke has the net effect of selectively deactivating aromatization
sites which require a large ensemble of atoms to constitute the active
site but not affecting the dehydrogenation activity which is less
ensemble-sensitive. Therefore, those particles that are not protected
against coking inside the channels of the zeolite rapidly become unselective.
In support of this hypothesis, the hydrogenolysis reaction
which also requires a large ensemble of atoms, decreases in parallel
with the aromatization reaction. The high sensitivity of Pt/KL to
sulfur may be due to a combination of effects which may involve
growth of metal particles outside the zeolite which would become
unselective and partial poisoning of the particles inside the zeolite,
causing a similar selective deactivation.
2, generating larger
amounts of hexenes. The observed results are consistent with the
hypothesis that the most important role of the zeolite is to inhibit
bimolecular interactions that lead to coke formation. The formation
of coke has the net effect of selectively deactivating aromatization
sites which require a large ensemble of atoms to constitute the active
site but not affecting the dehydrogenation activity which is less
ensemble-sensitive. Therefore, those particles that are not protected
against coking inside the channels of the zeolite rapidly become unselective.
In support of this hypothesis, the hydrogenolysis reaction
which also requires a large ensemble of atoms, decreases in parallel
with the aromatization reaction. The high sensitivity of Pt/KL to
sulfur may be due to a combination of effects which may involve
growth of metal particles outside the zeolite which would become
unselective and partial poisoning of the particles inside the zeolite,
causing a similar selective deactivation.