Synthesis and Characterization of Bismuth-Cerium Oxides for the Catalytic Oxidation of Diesel Soot

In this paper, the syntheses of a set of cerium-bismuth mixed oxides with the formula Ce_1-xBi_xO_2-x/2, where the range of x is 0.0 to 1.0 in 10 mol% steps, via co-precipitation methods is described. Two synthesis routes are tested: The "normal" and the so called "reverse strike" (RS) co-precipitation route. The syntheses are performed with an automated synthesis robot. The activity for Diesel soot oxidation is measured by temperature programmed oxidation with an automated, serial thermogravimetric and differential scanning calorimetry system (TGA/DSC). P90 is used as a model soot. An automated and reproducible tight contact between soot and catalyst is used. The synthesized catalysts are characterized in terms of the specific surface area according to Brunauer, Emmett and Teller (S), as well as the dynamic oxygen storage capacity (OSC). The crystalline phases of the catalysts are analysed by powder X-ray diffraction (PXRD) and Raman spectroscopy. The elemental mass fraction of the synthesized catalysts is verified by X-ray fluorescence (XRF) analysis. A correlation between the T values, OSC and S has been discovered. The best catalytic performance is exhibited by the catalyst with the formula RS-Ce_0.8Bi_0.2O_x which is synthesized by the reverse strike co-precipitation route. Here, a correlation between activity, OSC, and S can be confirmed based on structural properties.