SPECTROSCOPIC AND CATALYTIC EVIDENCE FOR THE INCORPORATION OF GALLIUMIN THE AEL FRAMEWORK

Ga-71 MAS n.m.r. analysis and the catalytic behavior during the transf ormation of l-butene and n-butane strongly suggest the incorporation o f Ga into the AIPO(4)-11 (AEL) framework during the synthesis of GaAPS O-11. A unique clear signal at around +120 ppm is proposed to be assoc iated with the presence of tetrahedral Ga in the AEL framework of the unmodified GaAPSO-11. Migration of structural Ga atoms to the silicon domain of the AEL framework seems to occur as a result of a mild hydro thermal treatment, giving rise to an additional signal at +156 ppm, pr eviously associated with tetrahedral gallium in gallosilicates with th e MFI topology. The fact that GaAPO-11 and GaAPSO-11 behaved in a way similar to their counterparts AIPO(4)-11 and SAPO-11 during the skelet al isomerization of n-butenes reinforces the idea of an isomorphous su bstitution of Al(III) by Ga(Ill) in the AEL framework. The transformat ion of n-butane was shown to be a valuable test for detecting the pres ence of small amounts of hydro-dehydrogenating extraframework gallium species (EFGS) in Ga-supported SAPO-11 (Ga/SAPO-11). The fact that the sample of GaAPSO-11 was completely inactive for Eh is transformation leads us to believe that the incorporation of gallium into the tetrahe dral positions of the AEL framework was almost complete. (C) Elsevier Science Inc. 1997.