Synthesis of MFI type ferrisilicate zeolite (Fe-MFI) nanocrystals by a dry gel conversion (DGC) method and their application to methanol to olefin (MTO) reactions

We have synthesized MFI type ferrisilicate zeolite (Fe-MFI) nanocrystals with a crystal size smaller than 100 nm by a dry gel conversion (DGC) method using a sole template (tetrapropylammonium hydroxide). The crystal size of Fe-MFI synthesized by the DGC method was much smaller than that of Fe-MFI synthesized by a conventional hydrothermal synthesis (HTS) method despite using the same precursor solution. The catalytic performance of the nano-sized Fe-MFI in methanol to olefin (MTO) reactions was investigated. The Fe-MFI catalysts showed higher propylene to ethylene (P/E) ratios and lower light paraffin yields compared with MFI type aluminosilicate zeolites (Al-MFI) for both the synthesis methods. In addition, nano-sized Fe-MFI showed a higher P/E ratio (ca. 30) and a longer catalyst lifetime than macro-sized Fe-MFI synthesized by the HTS method.