Probing the basic character of alkali-modified zeolites by CO{sub 2} adsorption microcalorimetry, butene isomerization, and toluene alkylation with ethylene

Journal Article · Sat Jan 01 04:00:00 EST 2000 · Journal of Catalysis

DOI:https://doi.org/10.1006/jcat.1999.2703· OSTI ID:20014522

Bordawekar, S V; Davis, R J

Two types of alkali-modified zeolites X and Y were studied, namely, zeolites containing occluded cesium oxides and zeolites containing occluded alkali metals (Na, Cs). Zeolites with occluded CsO{sub X}, obtained via impregnation and decomposition of cesium acetate, exhibited higher CO{sub 2} adsorption capacities and higher heats of adsorption than the corresponding ion-exchanged zeolites. However, the heats of adsorption were significantly lower on the zeolite-supported oxides ({approximately}85 kJ/mol) compared to bulk cesium oxide ({approximately}270 kJ/mol). The CO{sub 2} adsorption capacities of the zeolites containing occluded CsO{sub X} increased linearly with the amount of occluded cesium (1 CO{sub 2} per 4 occluded Cs atoms), and the catalytic activity for 1-butene isomerization was commensurate with the CO{sub 2} uptake on the materials. Stronger base sites were created in zeolites by decomposition of impregnated alkali azides (Na, Cs), due to the formation of alkali metal species. These materials were active catalysts for the side-chain alkylation of toluene with ethylene, whereas zeolites containing occluded CsO{sub X} were inactive for the reaction. Dioxygen adsorption followed by thermal treatment of zeolites containing occluded alkali metal resulted in the elimination of their activity for toluene alkylation whereas their activity for butene isomerization was retained. Alkali oxide- and alkali metal-containing microporous carbon materials exhibited significantly different adsorption properties and catalytic activities from their zeolite counterparts, possibly due to the different nature of the occluded species and/or steric constraints in the amorphous carbon.

• Research Organization: Univ. of Virginia, Charlottesville, VA (US)
• Sponsoring Organization: US Department of Energy
• DOE Contract Number: FG05-95ER14549
• OSTI ID: 20014522
• Journal Information: Journal of Catalysis, Journal Name: Journal of Catalysis Journal Issue: 1 Vol. 189; ISSN 0021-9517; ISSN JCTLA5
• Country of Publication: United States
• Language: English

Related Subjects

02 PETROLEUM
ADSORPTION
ADSORPTION HEAT
ALKYLATION
BUTENES
CARBON DIOXIDE
CATALYTIC EFFECTS
CESIUM
CESIUM OXIDES
ISOMERIZATION
SODIUM
SORPTIVE PROPERTIES
TOLUENE
ZEOLITES