Abstract
This chapter describes high-temperature magic angle spinning nuclear magnetic resonance (MAS NMR) investigation of the mobility of cations and guest compounds in zeolites X and Y. The rapid exchange of sodium cations in dehydrated zeolite Na-Y starts at ca. 573 K as shown by high-temperature sodium ( 23 Na) MAS NMR spectroscopy and is characterized by an activation energy of E A = 20±2 kJ/mol. The rapid exchange of cesium (Cs) cations in dehydrated zeolite CsNa-Y starts at ca. 423 K. Activation energy for the cesium exchange in zeolite Y equal to that for the sodium exchange is determined by applying 133 Cs MAS NMR spectroscopy. These activation energies are significantly lower than those estimated for cesium exchange processes observed at temperatures of 423 to 773 K for dehydrated zeolites CsNa-Y and CsNa-X impregnated with cesium hydroxide as guest compound.
Published Version
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