Calorimetric and IR-spectroscopic study of methanol adsorption on zeolites
- Russian Academy of Sciences, Petersburg (Russian Federation). I.V. Grebenshchikov Inst. of Silicate Chemistry
The heats of CH[sub 3]OH adsorption on sodium faujasites and mordenites with different Si/Al ratios in the framework and on zeolites A, ZK-4, and ZK-5 were measured calorimetrically. The IR spectra of adsorbed CH[sub 3]OH were determined for the same zeolites. The decrease of cation concentration with increasing Si/Al ratio in the framework of faujasites, mordenites, and zeolites A and ZK-4 results in the decrease of CH[sub 3]OH adsorption heats for the broad coverage range and in weakening of the [nu][sub OH] disturbance for adsorbed CH[sub 3][sub OH]. For highly dealuminated faujasite, the OH vibrations in adsorbed CH[sub 3]OH are strongly perturbed due to intermolecular interactions even at small coverages. The adsorption heat is very low in this case. Sodium cations at 8-membered oxygen rings of zeolite ZK-5 are more tightly bonded to the framework and so they are less active adsorption centers for CH[sub 3]OH molecules as compared to the appropriate cations of zeolite Na-A. The step on the adsorption heat curve for CH[sub 3]OH on zeolite Na-A in the coverage interval from 3 to 5 molecules/unit cell corresponds to the transition of adsorbed molecules from the interactions with cations in 8-membered oxygen rings to those with cations in 6-rings. The second step at coverages about 6 molecules/unit cell results from the crystallographic nonidentity of adsorption complexes formed by CH[sub 3]OH molecules with cations at 4-rings for different uptakes. The acidic structural OH groups of decationated mordenite are involved in strong hydrogen bonds with adsorbed CH[sub 3]OH molecules or protonate them.
- OSTI ID:
- 7169853
- Journal Information:
- Journal of Colloid and Interface Science; (United States), Journal Name: Journal of Colloid and Interface Science; (United States) Vol. 165:2; ISSN 0021-9797; ISSN JCISA5
- Country of Publication:
- United States
- Language:
- English
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37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
400201 -- Chemical & Physicochemical Properties
ABSORPTION SPECTROSCOPY
ADSORPTION
ADSORPTION HEAT
ALCOHOLS
CALORIMETRY
CATALYSTS
ELECTROMAGNETIC RADIATION
ENTHALPY
HYDROXY COMPOUNDS
INFRARED RADIATION
INORGANIC ION EXCHANGERS
ION EXCHANGE MATERIALS
MATERIALS
METHANOL
MINERALS
ORGANIC COMPOUNDS
PHYSICAL PROPERTIES
RADIATIONS
SILICATE MINERALS
SORPTION
SORPTIVE PROPERTIES
SPECTROSCOPY
SURFACE PROPERTIES
THERMODYNAMIC PROPERTIES
ZEOLITES