Mechanisms of methanol adsorption on silicalite and silica. IR spectra and ab-initio calculations

Journal Article · Thu Nov 18 04:00:00 EST 1993 · Journal of Physical Chemistry; (United States)

DOI:https://doi.org/10.1021/j100148a023· OSTI ID:5651695

Pelmenschikov, A G; Paukshtis, E A ^[1]; Morosi, G; Gamba, A ^[2]; Zecchina, A; Bordiga, S ^[3]

---

1. Inst. of Catalysis, Novosibirsk (Russian Federation)
2. Universita di Milano (Italy)
3. Universita di Torino (Italy)

Combined IR and ab-initio studies suggest the presence of two chemisorbed species of methanol on ZSM5-like silicalite, namely, free and hydrogen-bonded SiOCH[sub 3] groups, which are in thermodynamic equilibrium. Upon decreasing the temperature, the relative concentration of the free SiOH groups increases due to the SiOH transition from the hydrogen-bonded SiOCH[sub 3] groups into hydrogen-bonded SiOH aggregates. Physically adsorbed methanol forms large hydrogen-bonded polymers, even at high concentration of unoccupied SiOH groups. The CH frequencies of the chemisorbed and physically adsorbed species on silicalite are equal to those on silica, indicating the identity of these forms on both solids. Owing to the extremely high local concentration of SiOH groups in atomic-scale defects in silicalite, the effect of the reversible transformation of two chemisorbed forms to each other, on changing the temperature, is more pronounced for this solid than for silica. 45 refs., 10 figs., 7 tabs.

• OSTI ID: 5651695
• Journal Information: Journal of Physical Chemistry; (United States), Journal Name: Journal of Physical Chemistry; (United States) Vol. 97:46; ISSN JPCHAX; ISSN 0022-3654
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
400102 -- Chemical & Spectral Procedures
400201* -- Chemical & Physicochemical Properties
99 GENERAL AND MISCELLANEOUS
990200 -- Mathematics & Computers
ADSORPTION
ALCOHOLS
CHALCOGENIDES
DATA
EXPERIMENTAL DATA
HYDROCARBONS
HYDROXY COMPOUNDS
INFORMATION
INFRARED SPECTRA
MATHEMATICAL MODELS
METHANOL
MINERALS
NUMERICAL DATA
ORGANIC COMPOUNDS
ORGANIC POLYMERS
OXIDE MINERALS
OXIDES
OXYGEN COMPOUNDS
POLYMERS
SILICA
SILICON COMPOUNDS
SILICON OXIDES
SORPTION
SPECTRA
THEORETICAL DATA