High Surface Area Ceria for CO Oxidation Prepared from Cerium -Butoxide by Combined Sol-Gel and Solvothermal Processing.

ABSTRACT

CeO was synthesized by combined sol-gel and solvothermal processing of gels obtained from acetaldoximate-modified cerium(IV) -butoxide in the presence of the non-ionic surfactant Pluronic F127. The use of cerium(IV) -butoxide as precursor contrasts very favorably with the often used ceric ammonium nitrate and results in more reliable and tailorable properties of the final materials. The kind of post-synthesis treatment of the gels and the composition of the precursor mixture proved to be crucial for obtaining high surface area ceria with a high Ce proportion. Calcination in air or under nitrogen was compared with solvothermal treatment in ethanol or water and a combination of solvothermal treatment and calcination. The obtained materials are composed of 3.5-5.5 nm ceria nanoparticles. The highest specific surface area of 277 m/g was obtained after solvothermal treatment, and 180 m/g when solvothermal treatment was followed by calcination in air to remove residual organic groups. The highest Ce proportion was 18 % after solvothermal treatment in ethanol and additional calcination in air. CO oxidation on selected samples indicated that activity scaled with surface area and thus was largest for samples solvothermally treated in ethanol. The reaction rate of the best sample was about 75-times larger than that of commercial ceria.