Ceria spray pyrolysis

The catalysts were synthesized as films, with ceria prepared by spray pyrolysis of 0.1 M solutions of Ce(N03)3 onto nonporous alumina wafers held at 250 °C. The ceria was then calcined at 300 °C, resulting in a crystallite size of 10 nm. Pt, Pd, or Rh was vapor deposited onto the oxide film. For kinetics testing, the temperature was 300 °C. To determine the reaction order of H20, Pco was maintained constant at 0.026 atm. For the reaction order on CO, Ph2o was maintained constant at 0.02 atm. The kinetic parameters are tabulated in Table 69. 

Aqueous methods and conversion methods In aqueous solutions, the Ce " ions would precipitate even in quite acidic solutions while the Ce " " ions would precipitate as Ce(OH)3 at much higher pH values (7-9) Ce(OH)3 precipitate could be oxidized into ceria in air. In nonaqueous solutions, ceria forms with decomposition of appropriate precursor, with or without the oxidation by air or other oxidative species. If doping is a target, the doping ions would be introduced during the synthesis, and the coprecipitation, sol-gel, combustion/spray pyrolysis, or hydrothermal techniques are usually employed for such a task. 

Polycrystalline films can be prepared by spray pyrolysis. In this technique a spray of an aqueous solution of cerium salt is nebulized and directed by a stream of compressed gas onto a heated substrate. Various parameters are important for determining the resulting structure of the ceria film. The effects of the spray solution and of substrate temperature for films deposited upon silica substrates have... 

The adsoqjtion of NO on metal loaded ceria has been examined for Pt, and Pd, As known from work on single crystals, NO dissociates to some extent on each of these metals. The amount of dissociation is dependent upon the structure of the metal surface. Gorte considered Pt and Pd particles deposited on rough, poly crystal line ceria films grown by spray pyrolysis.For Pt they found variation in the TPD results (amount of NO uptake and shape of N2 desorption profile) that varied with the size of the Pt particles. However, the results were comparable to NO TPD results from Pt grown on sapphire. It was concluded that no unusual interaction existed between Pt and the (oxidized) ceria. For Pd it was found that a pronounced difference in the TPD product ratio, NO/N2, occurred for Pd on ceria compared to Pd on sapphire. They attributed the difference to NO adsorption on reduced ceria. 

A series of catalysts for the low temperature WGS reaction has been prepared by flame spray pyrolysis. The catalysts consist of a traditional Cu/Zn0/Al203 sample, a ceria promoted Cu/Zn0/Al203 catalyst and a series of ceria and/or zirconia supported Cu or Pt catalysts. Flame spray pyrolysis results in high surface area catalysts with good dispersion. The WGS activity of the catalyst samples has been measured in a plug-flow reactor in the temperature range 180-315 °C. ... 

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