FTIR study of CO adsorbed at low temperature on zeolite L
Evidence for an ordered distribution of aluminium atoms
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Gemma Turnes Palomino, Carlos Otero Areán, Francesco Geobaldo, Gabriele Ricchiardi, Silvia Bordiga and Adriano Zecchina
Abstract
FTIR spectroscopy of CO adsorbed at liquid-nitrogen temperature on zeolite K-L revealed two main IR absorption bands at 2161 and at 2150 cm-1, respectively. These bands were assigned to the C–O-stretching mode of carbon monoxide interacting, through the carbon atom, with K+ ions present in the main channel of the zeolite and which are present in two different environments. This strongly suggests (in agreement with previous NMR studies) an ordered partition of aluminium atoms in the zeolite framework. When zeolite K-L was partially exchanged with Na+ ions, the corresponding IR absorption bands were observed at 2174 and at 2157 cm-1. Minor bands, centred at 2137 and ca. 2121 cm-1 for CO adsorbed on both zeolite K-L and zeolite Na, K-L were also observed and discussed.