MICROWAVE SYNTHESIS OF MNAPO MNAPSO-44 AND MNAPO-5 - STABILITY OF MN2+ IONS ON FRAMEWORK POSITIONS/

Aluminophosphate molecular sieves of structure 44 and structure 5 with incorporation of manganese (up to 11 mass% MnO) were prepared by micr owave synthesis. The MnAPO samples were characterized in comparison to the corresponding SAPO samples by X-ray diffraction, light microscopy , infrared spectroscopy, thermal analysis, ESR spectra, nitrogen adsor ption and calorimetric measurements of the heat of NH3 adsorption. Man ganese replaces aluminium on tetrahedrally coordinated framework posit ions. The ESR measurements reveal a cluster-like arrangement of Mn2+ i ons (Mn2+-O-P-O-Mn2+). The as-synthesized samples are colourless. Afte r calcination in air under static conditions a blue/deep blue colour i s observed which is associated with the full adsorption capacity. The adsorption of polar molecules, as water and ammonia, causes marked str ucture destruction, and the colour changes from blue to pink or to gre y shades. P-OH groups and Lewis acid sites are detected by infrared sp ectroscopy.