Iron-containing defect-rich mixed metal oxides for Friedel–Crafts alkylation

Several stable iron-containing spinel oxides with the composition CuFe2O4 or FeCr2O4 were prepared by different methods including thermal nitrate decomposition, combustion synthesis, and mechano-chemical synthesis. Materials were compared to commercially available spinels produced by conventional ceramic route with respect to their structural properties and catalytic activity. Phase compositions and microstructures of the catalysts were studied in detail. The catalysts were tested in the Friedel–Crafts alkylation of various aromatic compounds with different alkyl halides as alkylating agents. Microstructural properties (microstrains) of the synthesized binary oxides have been identified as a reason for the increased reactivity. Even at low reaction temperatures of 50–70 °C catalysts maintained their high activity resulting in TOFs of up to 3000 h−1 and excellent selectivity with total heterogeneous behavior in catalysis.

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► Achieved TOFs for the CuFe2O4 and FeCr2O4 materials far exceed literature data.
► Combustion and mechano-chemical synthesis lead to much more defective materials.
► Synthesized materials are much more active allowing lower reaction temperatures.
► Also less activated arenes and secondary alkyl chlorides can be converted.
► Microstructural properties show major influence on the catalytic performance.