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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