SYNTHESIS OF A MERLINOITE-TYPE ZEOLITE WITH AN ENHANCED SI AL RATIO VIA PORE FILLING WITH TETRAETHYLAMMONIUM CATIONS/

A merlinoite type zeolite with an enhanced Si/Al ratio (around 3.8) co mpared to known isostructural materials has been synthesised hydrother mally from a gel with Si/Al=5 in the presence of tetraethylammonium an d K+ cations. The zeolite has been characterised by a number of techni ques and in its calcined form the structure was refined from synchrotr on powder X-ray diffraction data [a = 14.1291 (10), b = 14.1308(10), c = 9.9274(5)Angstrom, Immm]. The different techniques reveal the enhan ced Si/Al ratio of the zeolite. Tetraethylammonium is occluded within the tridimensional small pore channels, forcing the K+ and hence the A l content to diminish by 30-50% compared to conventional merlinoite-ty pe zeolites. The thermal stability of the material is greatly improved , although if K+ cations in the zeolite are exchanged by NH4+ the stab ility decreases as a function of the degree of exchange, suggesting a low stability for the acidic form of merlinoite.