New iron-containing MFI-type zeolites in the catalytic conversion of ethanol, propane, and N 2 O

For the first time, two groups of iron-containing zeolites (MFI type) of general compositions (H x )[Fe x 3+ Si 12− x 4+ O 24 ] (FeHZSM-5, module Si/Fe = 34; hydrothermal method) and Fe 2 O 3 /(H x )[Al 3+ x Si 4+ 12− x O 24 ] × w H 2 O with the Fe 2 O 3 polycrystalline initial content 10, 35, 50 wt%. (Fe 2 O 3 /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 Fe 2 O 3 /AlHZSM-5 differ in surface compositions, the oxygen environment around Fe 3+ 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 N 2 O conversion composites, Fe 2 O 3 /AlHZSM-5 are more active than FeHZSM-5 in the low-temperature region. The conversion degree of ethanol, propane, and N 2 O is suppressed with an increase in the zeolite module Si/Al, the initial Fe 2 O 3 content, and when replacing nanosized Fe 2 O 3 with the amorphous one in the composites. Graphical abstract