Hydroxidgruppen an Zeolithen. III. Eigenschaften von Hydroxidgruppen an ZnNaY-, CuNaY-, NiNaY- und CrNaY-Zeolithen

Hydroxide Groups on Zeolites. III. Properties of Hydroxide Groups on ZnNaY, CuNaY, NiNaY, and CrNaY Zeolites The properties of hydroxide groups in dependence on the degree of exchange were studied by IR spectroscopy of ZnNaY, CuNaY, NiNaY, and CrNaY zeolites. Five kinds of hydroxide groups occur on these zeolites: Hydroxid groups limiting the lattice, 3 kinds of structural hydroxide groups, and MeOH⁺ groups. These are the same kinds of hydroxide groups as exist on alkaline earths-Y-zeolites. Some of the OH groups act as acid Brönsted centers. The number of acid Brönsted centers reaches maximum values at degrees of exchange of 40–50% after a pretreatment at 300–400°C. The zeolitic structure is partially destroyed in ZnNaY, CuNaY, and especially CrNaY, at high degree of exchange.