A series of MFI aluminosilicate (Al-MFI), MFI ferrisilicate (Fe-MFI) and MFI ferroaluminosilicate ((Al,Fe)-MFI), with crystal sizes of approximately 100 nm, were synthesized using an emulsion method. UV-vis spectra and ac-NH3-TPD profiles confirmed the isomorphous substitution of Fe for Si into the MFI framework and showed that almost all Fe3+ species were well dispersed without forming bulky iron oxide particles. In addition, the presence of Bronstead acid sites in MFI ferroaluminosilicate, derived from both Al and Fe, was confirmed from IR spectra. The selective production of propylene from methanol was examined using MFI ferrisilicate with different crystal sizes. The nano-sized MFI ferrisilicate exhibited a longer catalyst lifetime and gave a higher propylene to ethylene ratio compared with the macro-sized MFI ferrisilicate. Although the weak acidity of the MFI ferrisilicate suppressed the formation of aromatics to a greater extent than was found with the MFI aluminosilicate, the former generated a lower propylene yield. The MFI ferroaluminosilicate gave a high propylene yield of 47.9 C-mol% together with a low aromatics yield of 1.9 C-mol%. Product yield for methanol conversion reaction at 723 K over nano-sized MFI aluminoferrisilicate. [GRAPHICS]