Aluminum-promoted tungstated zirconia catalyst in n-butane isomerization reaction
Resource
Journal of Catalysis 215(2003), 45-56
Journal
Journal of Catalysis 215(2003)
Pages
45-56
Date Issued
2003
Date
2003
Author(s)
DOI
246246/2006111501275315
Abstract
The promotion effect of Al on tungstated zirconia (WZ) catalyst was studied in a butane isomerization reaction and compared with Fepromoted
catalyst (FWZ). XRD and EXAFS studies revealed an interaction between Al and WOx , whereas XANES analysis indicates that
the octahedral symmetry around W sites remained unchanged. Two Al3+ sites are present on co-precipitated Al-promoted WZ (AWZC)
catalyst; one is formed by the substitution of Al species in the WOx structure and the other is the terminal Al species anchoring on the WOx
surface. Only the terminal Al3+ sites are evident in impregnated AWZ catalyst. Our NH3-TPD and DRIFT results suggest that these Al3+
sites are Lewis acid in nature with at least moderate acid strength. They are stronger than those Brönsted and Lewis acid sites originally
present in WOx. Exposure of the catalyst to atmospheric water results in the poisoning of these Al3+ sites by chemisorbed water, forming
octahedral species. In an n-butane isomerization reaction, Al addition onto WZ increases both the activity and the stability of the catalysts.
The catalytic activity of fresh catalysts decreases in the order FWZI > AWZC WZC, whereas regenerated catalysts follow the order
AWZC FWZI > WZC. The improved activity of AWZC over WZC catalyst is related to the increased acidity created by the Al promoter.
Most importantly, a great enhancement in catalytic activity was observed for regenerated catalyst relative to the fresh catalyst. The regenerated
AWZC catalyst is as active as the FWZI catalyst.
Subjects
Tungstated zirconia
n-Butane isomerization
Promoter
Aluminum
Iron
Lewis acid site
Acid catalyst
EXAFS
NH3-TPD
DRIFT
Publisher
Taipei:National Taiwan University Dept Chem Engn
Type
journal article