Insights on Ga-zeolite catalysts: X-ray powder diffraction and absorption spectroscopy characterization at ambient conditions

Gallium substituted L, mordenite and ferrierite zeolites, obtained through wet impregnation, were characterized combining adsorption isotherms, X-ray powder diffraction (XRPD) and X-ray adsorption spectroscopy (XAS) to elucidate nature and structure of the Ga3+ sites of the materials. The saturation capacity of L was higher than those of mordenite and ferrierite. Rietveld refinements on saturated materials confirm the presence of Ga3+ within the zeolites pores system. Besides, the analysis of the structural features (i.e., lightening of tetrahedral bond distances and narrowing of interthetraedral angles) suggest that small fractions of metal cation have been also incorporated in tetrahedral sites. This is corroborated by XAS analysis, which confirms the effective inclusion of gallium into the zeolites frameworks, thus indicating that the incorporation of Ga3+ from wet impregnation within the zeolite structures occurs in both framework and non-framework positions.