Investigation of the hydration of zeolite NaA by two-dimensional sodium-23 nutation NMR

A 2-dimensional nutation NMR expt. is used to observe the change of quadrupole parameters of Na+ ions in zeolite NaA when the zeolite is loaded in steps with H2O. Two Na sites were obsd. in the dry zeolite, at, resp., 6-rings and 8-rings, and the H2O absorption was monitored at these sites. When the amt. of absorbed H2O is increased in steps, the quadrupole interaction of Na at the 6-rings at first decreases; with more absorbed H2O the quadrupole interaction of the Na+ ions at the 8-rings becomes small. Relaxation effects in the rotating frame, studied by combining rotary echoes with nutation NMR, indicate a mobility of Na+ ions or H2O mols.