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Interaction of Methanol with Alkali Metal Exchanged Molecular Sieves. 1. IR Spectroscopic Study

2000; American Chemical Society; Volume: 104; Issue: 35 Linguagem: Inglês

10.1021/jp0001945

1520-6106

M. Rep, A.E. Palomares, G. Eder-Mirth, J.G. van Ommen, Notker Rösch, Johannes A. Lercher,

Catalytic Processes in Materials Science

The adsorption of methanol over various alkali metal exchanged zeolites (ZSM5, MOR, and FAU) was studied by in situ IR spectroscopy and gravimetry. Lower Si/Al ratios (increasing the polarity of the zeolite lattice) increased the interaction between methanol hydrogens, i.e., hydroxy as well as the methyl hydrogens, and the lattice oxygen. Similarly, this interaction was strengthened as the atomic weight of the alkali metal cation increased. This stronger hydrogen bonding did not lead to an overall higher heat of adsorption. This suggests that the most important interaction occurs between the electron lone-pair donor function of methanol (i.e., the oxygen) and the electron pair acceptor function of the zeolite (i.e., the alkali metal cation). The methanol adsorption complexes in the zeolite pores are discussed.