Abnormalities of cation movements in 3A zeolite

The dielectric spectra of dehydrated and partially hydrated 3A zeolites with the cation composition of Na6.1K5.9-A were measured to investigate movements of cations in the zeolite (‘A’ stands for the framework of A zeolite). The spectra of dehydrated state showed two relaxations (relax I in the lower frequency side and relax II in the higher frequency side) in the ranges of 2 < log(f/Hz) < 7 and 389 K < T < 650 K. Both relaxations were affected by the first adsorbed water molecule per unit cell. From the result and the similarity of cation distribution between Na6.1K5.9-A and Na12-A (or K12-A), both relaxations were attributed to the movements of cation occupying site 3 in the ground state. The activation energies related to the cation movements in relax I and II were EI = 78 and EII = 64 kJ mol−1, respectively. EI (EII) in Na6.1K5.9-A was not in between EI’s (EII’s) in Na12-A and K12-A, even though the cation composition of Na6.1K5.9-A was intermediate between those of Na12-A and K12-A. In order to examine a relative magnitude of activation energy, heated behaviors of three zeolites by microwave irradiation were measured. The heated temperatures under the same condition were in the order of Na12-A > K12-A > Na6.1K5.9-A in every condition, and suggested the order of E(Na12-A) < E(K12-A) < E(Na6.1K5.9-A). The reason why EI (EII) in Na6.1K5.9-A was not in between EI’s (EII’s) in Na12-A and K12-A was considered from three factors (the coulombic attraction, coulombic repulsion and steric hindrance), but could not be explained by the factors. An influence of another factor was strongly expected.

Graphical abstractThe abnormality of cation movements in Na6.1K5.9-A zeolite found in dielectric measurements also appeared in microwave heating as shown in the figure, that is, the behaviors of cations in Na6.1K5.9-A were not in between those in Na12-A and K12-A.Figure optionsDownload full-size imageDownload as PowerPoint slideHighlights► Cation movements in 3A showed larger activation energies than those in Na-A and K-A. ► The heated temp. of 3A by MW irradiation was not in between those of Na-A and K-A. ► Temp. heated by MW reflected the magnitude relation of activation energy of movement. ► Abnormalities of cation in 3A could not be explained by conventional three factors.