INVESTIGADORES
DIEZ veronica Karina
artículos
Título:
Effect of the acid-base properties of Mg-Al mixed oxides on the catalyst deactivation during aldol condensation reactions
Autor/es:
VERÓNICA K. DÍEZ; CARLOS R. APESTEGUÍA; JUANA I. DI COSIMO
Revista:
LATIN AMERICAN APPLIED RESEARCH
Editorial:
PLAPIQUI(UNS-CONICET)
Referencias:
Año: 2003 vol. 33 p. 79 - 86
ISSN:
0327-0793
Resumen:
The effect of chemical composition of
Mg-Al mixed oxides on both the acid-base properties
and the deactivation process during the gas phase
self-condensation of acetone was studied. The
activity and selectivity for acetone oligomerization
depended on the catalyst acid-base properties. Mgrich
catalysts selectively yielded mesityl oxides
whereas Al-rich MgyAlOx oxides produced mainly
isophorone. The initial deactivation rate, increased
linearly with the density of surface basic sites,
thereby suggesting that although MgyAlOx oxides
promote the self-condensation of acetone by both
acid- and base-catalyzed mechanisms, the
deactivation rate would be closely related to the
surface basic properties. The MgyAlOx activity
declines in the acetone oligomerization reaction due
to a blockage of both base and acid active sites by a
carbonaceous residue formed by secondary
reactions. The amount and the nature of the carbon
deposits were characterized by temperatureprogrammed
oxidation technique. MgyAlOx and
Al2O3 formed more and heavier coke than pure MgO
but the latter deactivates faster. The deactivation
rate and coke composition are defined by the nature
of the active site involved in the coke-forming
reactions at different catalyst compositions rather
than by the carbon amount or polymerization
degree.yAlOx oxides produced mainly
isophorone. The initial deactivation rate, increased
linearly with the density of surface basic sites,
thereby suggesting that although MgyAlOx oxides
promote the self-condensation of acetone by both
acid- and base-catalyzed mechanisms, the
deactivation rate would be closely related to the
surface basic properties. The MgyAlOx activity
declines in the acetone oligomerization reaction due
to a blockage of both base and acid active sites by a
carbonaceous residue formed by secondary
reactions. The amount and the nature of the carbon
deposits were characterized by temperatureprogrammed
oxidation technique. MgyAlOx and
Al2O3 formed more and heavier coke than pure MgO
but the latter deactivates faster. The deactivation
rate and coke composition are defined by the nature
of the active site involved in the coke-forming
reactions at different catalyst compositions rather
than by the carbon amount or polymerization
degree.yAlOx oxides
promote the self-condensation of acetone by both
acid- and base-catalyzed mechanisms, the
deactivation rate would be closely related to the
surface basic properties. The MgyAlOx activity
declines in the acetone oligomerization reaction due
to a blockage of both base and acid active sites by a
carbonaceous residue formed by secondary
reactions. The amount and the nature of the carbon
deposits were characterized by temperatureprogrammed
oxidation technique. MgyAlOx and
Al2O3 formed more and heavier coke than pure MgO
but the latter deactivates faster. The deactivation
rate and coke composition are defined by the nature
of the active site involved in the coke-forming
reactions at different catalyst compositions rather
than by the carbon amount or polymerization
degree.yAlOx activity
declines in the acetone oligomerization reaction due
to a blockage of both base and acid active sites by a
carbonaceous residue formed by secondary
reactions. The amount and the nature of the carbon
deposits were characterized by temperatureprogrammed
oxidation technique. MgyAlOx and
Al2O3 formed more and heavier coke than pure MgO
but the latter deactivates faster. The deactivation
rate and coke composition are defined by the nature
of the active site involved in the coke-forming
reactions at different catalyst compositions rather
than by the carbon amount or polymerization
degree.yAlOx and
Al2O3 formed more and heavier coke than pure MgO
but the latter deactivates faster. The deactivation
rate and coke composition are defined by the nature
of the active site involved in the coke-forming
reactions at different catalyst compositions rather
than by the carbon amount or polymerization
degree.2O3 formed more and heavier coke than pure MgO
but the latter deactivates faster. The deactivation
rate and coke composition are defined by the nature
of the active site involved in the coke-forming
reactions at different catalyst compositions rather
than by the carbon amount or polymerization
degree.