Honeycomb-supported perovskite catalysts for high-temperature processes

Structured Perovskite-Based Catalysts and Their Application as Three-Way Catalytic Converters—A Review

“…Immersion of the structured carrier in an aqueous solution of salt precursors in the absence of any additive [100,101] or in the presence of citric acid [102] is employed to prepare perovskite-type active phases directly on the substrate. Citric acid acts as a chelating agent and enables the preparation of highly concentrated precursor solutions.…”

“…The increased viscosity and concentration of such solutions result in increased amounts of deposited material. A variation of this preparation protocol uses a polymerized solution of nitrate precursors, citric acid and ethylene glycol prepared by the Pechini method [101,[103][104][105]. After withdrawal of the impregnated carrier, the excess solution is removed by blowing pressurized air.…”

“…After withdrawal of the impregnated carrier, the excess solution is removed by blowing pressurized air. Drying can be carried out in a conventional furnace (80-200 °C) [102][103][104], under air-flow at room temperature [101], or in a microwave oven [106]. The latter option allows a homogeneous drying, preventing the redistribution of the active material and therefore ensuring its good distribution on the carrier [107].…”

“…The latter option allows a homogeneous drying, preventing the redistribution of the active material and therefore ensuring its good distribution on the carrier [107]. Finally, calcination at 700-1100 °C [101,102,104] converts the precursors into the desired perovskite-type oxide. Phase pure materials are generally obtained but secondary phases are sometimes detected [101].…”

“…Finally, calcination at 700-1100 °C [101,102,104] converts the precursors into the desired perovskite-type oxide. Phase pure materials are generally obtained but secondary phases are sometimes detected [101]. However, the method presents some drawbacks.…”