cs5b00761_si_001.pdf (588.15 kB)
Design of Base Zeolite Catalysts by Alkali-Metal Grafting in Alcoholic Media
journal contribution
posted on 2015-09-04, 00:00 authored by Tobias
C. Keller, Kartikeya Desai, Sharon Mitchell, Javier Pérez-RamírezThis study investigates the synthesis
of base catalysts through
the postsynthetic grafting of alkali cations (Li, Na, K, Rb, or Cs)
onto USY zeolites in alcoholic solutions of the corresponding metal
hydroxides. In contrast to previous studies conducted in aqueous media,
the utilization of alcohols (MeOH, EtOH, or iPrOH)
offers increased control over the metalation process while simultaneously
averting degradation and dissolution of the crystalline framework.
The achievement of close to an atomic dispersion of the alkali metals
in the zeolite is confirmed by in-depth characterization combining 23Na MAS NMR, microscopy, elemental mapping, and CO2 chemisorption. Both the size of the alkali cation and the carbon
number of the alcohol influence the incorporation efficiency, which
is found to correlate with the expected basic strength of the corresponding
metal alkoxide. The presence of framework aluminum results in higher
sodium loadings due to the parallel incorporation by both ion exchange
and metalation. However, cations exchanged to the Al sites do not
provide the distinct basic properties of the grafted metals, and thus,
high-silica zeolites attain the highest basicity. Catalytic testing
in the self-condensation of propanal, a model reaction for the deoxygenation
of bio-oil, demonstrates excellent activity, with a > 90% selectivity
to the aldol reaction and a stable performance. The selective character
arising from the distinctive strength coupled with the isolated nature
and high accessibility of the grafted basic sites holds a large potential
for the development of superior zeolite catalysts for base-catalyzed
applications.
History
Usage metrics
Categories
Keywords
alkali cationsUSY zeolitesmetalation processCatalytic testingmetal alkoxideion exchangeAlcoholic MediaThis studyincorporation efficiencyaldol reactionCO 2 chemisorptionmetal hydroxideszeolite catalystsBase Zeolite Catalystsframework aluminum resultssodium loadingsAl sitescarbon numberstrengthmodel reactionalkali metals23 Na MAS NMRalkali cationbase catalystsalcohol influence
Licence
Exports
RefWorks
BibTeX
Ref. manager
Endnote
DataCite
NLM
DC