Abstract
The interaction between ammonium NH3 and H2O molecules in zeolitic nanopores is studied by in situ 1H nuclear magnetic resonance (NMR) method. The powder and single crystal samples of natural zeolites, heulandites Ca4[Al8Si28O72]·24H2O and clinoptilolite (Na, K,Ca1/2)6[Al6Si30O72], were used as the model system. It is shown that penetration of NH3 into the zeolitic nanopores is accompanied by disordering of the hydrogen sublattice of zeolitic water and by the fast proton exchange NH3 + H2O ↔ [NH4]+ + [OH]− characterized by correlation frequency vc = ~40 kHz. Another nanoreactor interactions are represented by interaction of [NH4]+ ions with exchangeable Na+ and Ca2+ ions of the zeolitic structure. The slow ionic exchange [NH4]+ → [Na,Ca1/2]+ and binding of [NH4]+ in cationic sites of the framework were visualized by NMR spectroscopy along with stepwise release of (Na,Ca1/2)OH from zeolitic pores to the external surface of zeolite grains.
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