New iron-containing MFI-type zeolites in the catalytic conversion of ethanol, propane, and N2O

For the first time, two groups of iron-containing zeolites (MFI type) of general compositions (H-x)[Fex3+Si12-x4+O24] (FeHZSM-5, module Si/Fe = 34; hydrothermal method) and Fe2O3/(H-x)[Alx3+Si12-x4+O24] x wH(2)O with the Fe2O3 polycrystalline initial content 10, 35, 50 wt%. (Fe2O3/AlHZSM-5, Si/Al = 12, 25, 40; precipitation from the solutions and gas phase) were synthesized and studied. It was found (XRD, EXAFS/XANES, XPS, FTIR spectroscopies) that FeHZSM-5 and Fe2O3/AlHZSM-5 differ in surface compositions, the oxygen environment around Fe3+ ions, and the iron oxide state. Amorphous or nanocrystallized iron oxide phases uniformly distributed over the zeolite particles surface with the formation of Fe-O-H-O-Si(Al) bonds. In the reaction of ethanol, propane, and N2O conversion composites, Fe2O3/AlHZSM-5 are more active than FeHZSM-5 in the low-temperature region. The conversion degree of ethanol, propane, and N2O is suppressed with an increase in the zeolite module Si/Al, the initial Fe2O3 content, and when replacing nanosized Fe2O3 with the amorphous one in the composites.