STUDIES ON ZEOLITE TRANSFORMATION OF HIGHSILICA GMELINITE INTO ANALCIME

An aluminosilicate system containing mixed bases (tetraethylammonium and sodium cations) at 423 K initially formed gmelinite and later transformed into analcime after 312 h. Solid-state Si-29 and Al-27 MAS n.m.r. spectroscopic results indicated that the transformation takes place with an increase in the relative intensity of the Si(1Al) peak and some distortion in the Al nucleus. An increase in (Si/Al) n.m.r. from gmelinite to analcime was also observed. These synthetic gmelinite and analcime samples were also more siliceous. Results from thermal analysis indicated a decrease in occlusion of organics with the increase in the gmelinite crystallinity. No occlusion of the organics was observed in the case of analcime. Deammoniation of ammonium-exchanged gmelinite also leads to transformation into analcime. Framework i.r. spectra were also in agreement with the phase transformation. Sorption experiments indicated the presence of stacking faults developed in the gmelinite during synthesis. Analcime sorbed only water, whereas gmelinite sorbed methanol, n-hexane, and cyclohexane in addition to water.