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An infrared study of H2O and D2O on HZSM-5 and DZSM-5

1993; Elsevier BV; Volume: 13; Issue: 2 Linguagem: Inglês

10.1016/0144-2449(93)90069-f

1873-3115

L.M. Parker, D.M. Bibby, Gary R. Burns,

Catalysis and Oxidation Reactions

Distinct differences are observed in the FTi.r. spectra of HZSM-5 + H2O, HZSM-5 + D2O, DZSM-5 + H2O, and DZSM-5 + D2O when water is sorbed in a ratio of one molecule of water per zeolite Al, or less, at 80°C. A peak at 3700 cm−1 and broad bands with maxima at ∼ 2900 and ∼ 2470 cm−1 were the same for HZSM-5 with either H2O or D2O sorbed and have been assigned to the spectrum of the zeolite Brönsted hydroxyl. A broad band at ∼ 3600 cm−1 was observed for sorbed H2O on HZSM-5 and DZSM-5, but not for D2O. These differences imply that hydrogen exchange between the zeolite Brönsted hydroxyls and sorbed water is slow under the conditions used here. To explain these observations, it is proposed that each sorbed water molecule is both partially protonated and is interacting with the zeolite lattice.