Activity of catalysts consisting of Fe2O3 nanoparticles decorating entire internal structure of mesoporous Al2O3 bead for toluene total oxidation

- NiO or Fe2O3 nanoparticles were deposited on mesoporous Al2O3 substrate.
- Fe2O3 nanoparticles were deposited even at the core part of mesoporous Al2O3 bead.
- Fe2O3/Al2O3 showed high catalytic activity due to the high loading and dispersion.
- 100% of oxidation of toluene using Fe2O3/Al2O3 with long-term stability was achieved.

Fe2O3 nanoparticles with a mean size of ∼1 nm were evenly distributed inside the mesoporous Al2O3 with a diameter of ∼1 mm using temperature-regulated chemical vapor deposition (TR-CVD), in which Fe(Cp)2 vapor and air were use as metal precursor and oxidizing agent, respectively. For comparison, NiO/Al2O3 was prepared by a similar method using Ni(Cp)2 vapor as Ni precursor, and the resulting structure showed NiO nanoparticles decorating only the shell part of the Al2O3 bead with a shell depth of ∼50 μm. After post-annealing of these samples under air at 450-750 °C, these structures were used as catalysts for oxidation of toluene in the reaction temperature range of 150-350 °C. Fe2O3/Al2O3 showed significantly higher catalytic activity than NiO-based catalysts, which can be attributed to the unique structure of Fe2O3/Al2O3, i.e., very small catalytically active nanoparticles are distributed inside the entire structure of the mesoporous supporting material. 100% conversion of toluene into CO2 with a long-term stability of the catalytic activity was realized at 350 °C using Fe2O3/Al2O3 under both dry and humid conditions with a toluene concentration of 10,000 ppm in the feed gas. It is worth noting that the unique structure of the Fe2O3/Al2O3 is stable after air-post-annealing at 750 °C. Our Fe2O3/Al2O3 catalysts are active for toluene oxidation, and stable upon annealing at high temperature, showing that one can use our Fe2O3/Al2O3 as a component of catalytic converter of harmful volatile organic compounds.

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