Methanol to olefins conversion over metal containing MFI-type zeolites

A series of metal containing MFI-type zeolites were synthesized by the rapid crystallization method with in two hours. Al(III), Cr(III), Cu (II), and Fe(III) metal ions were incorporated in the structure. Pure siliceous (Al free) MFIstructured zeolite was also prepared by the same procedure as used for the metallosilicate synthesis. Si/M ratio of the synthesis gel was 100 for metallosilicates aiming for high-silica zeolites. The products have been characterized by elemental analysis, specific surface area determination, scanning electron microscopy with EDX analysis, electron spin resonance, and thermal analysis. Catalytic property of the zeolites was measured for methanol to olefin conversion reaction. The results of XRD measurement showed the only crystalline phase present was that of MFI-type zeolite. E.s.r spectroscopy has been used to study the isomorphic substitution of the metal ions incorporated in the structure. The results show that Fe(III) and Cu (II) were mainly incorporated while, Cr(III) was observed to be present in non-framework sites. The amount of template occluded into the structure was determined by thermal analysis and found to be the same for metallosilicates and highly crystalline aluminum free zeolite. The results of catalytic activity showed that about 85% selectivity (based on gaseous hydrocarbon) for C ₂ ⁼-C ₄ ⁼ olefin was achieved in the case of iron containing synthesized high-silica zeolite as compared with 58% in the case of Al-containing zeolite catalyst.