In situ 1H NMR Study of Nanoreactor Interaction NH3–H2O in Zeolite Nanopores

The interaction between ammonium NH 3 and H 2 O molecules in zeolitic nanopores is studied by in situ 1 H nuclear magnetic resonance (NMR) method. The powder and single crystal samples of natural zeolites, heulandites Ca 4 [Al 8 Si 28 O 72 ]·24H 2 O and clinoptilolite (Na, K,Ca 1/2 ) 6 [Al 6 Si 30 O 72 ], were used as the model system. It is shown that penetration of NH 3 into the zeolitic nanopores is accompanied by disordering of the hydrogen sublattice of zeolitic water and by the fast proton exchange NH 3 + H 2 O ↔ [NH 4 ] + + [OH] − characterized by correlation frequency v c = ~40 kHz. Another nanoreactor interactions are represented by interaction of [NH 4 ] + ions with exchangeable Na + and Ca 2+ ions of the zeolitic structure. The slow ionic exchange [NH 4 ] + → [Na,Ca 1/2 ] + and binding of [NH 4 ] + in cationic sites of the framework were visualized by NMR spectroscopy along with stepwise release of (Na,Ca 1/2 )OH from zeolitic pores to the external surface of zeolite grains.