Cerium, additive

Oh, S.H. (1990) Effects of cerium addition on the CO-NO reaction kinetics over alumina-supported rhodium catalysts, J. Catal. 124, 477. 

Figure 17 shows a comparison of the fresh SO2 removal ability for these five major types of commercially available SOx catalysts. The materials were tested at 1350 F at various concentrations with a very low capacity cracking catalyst. The magnesia-based catalyst is much better than lanthanum-based catalyst followed by platinum or cerium on alumina and finally alumina alone. The reverse order in activity observed for the lanthanum-based and cerium additives, compared to the relative results given previously for lanthanum and cerium, was not investigated, but may be related to the presence of cerium on the lanthanum-based additive (27). 

The minimum temperature, where the additive filter systems can operate, is in the range of 625 - 650 K. The additive dosage rates to the diesel fuel generally are 30 - 50 ppm metal content on a weight basis. The resulting ash from cerium and iron does not plug the filter, in contrast to copper, where serious filter pluggings are reported. When 25 ppm of cerium additive is used for a typical heavy duty truck, the filler will be 50 % filled after 75,000 to 150,000 miles [5]. Copper is reported to... 

A combination of a fuel additive and a CR-DPF could possibly cover the temperature window from 575 K and higher and preferably at temperatures lower than 575 K. The combination of a platinum fuel additive for NO oxidation with a cerium additive for catalysed soot oxidation with O2 was studied as a possible application in which the above mentioned two mechanisms are incorporated. 

The platinum additive studied was Platinum Plus 3100, supplied by Clean Diesel Technologies, Inc. The copper additive was OS9640K a gift from Lubrizol. The cerium additive was DPX9 from Rhodia, and the iron additive was ferrocene from Aldrich. 

All combinations of platinum with other additives lead lo a decreased balance point temperature. The largest effect of platinum in the fuel and on the filter is observed when it is used in combination with a cerium additive. The minimum temperature is lowered with a total of 160 K. Copper and iron are more active as an individual additive, whereas the minimum temperature is higher when these additives are used, instead of cerium, in combination with the platinum additive and filter. The lowest additive concentration studied with this equipment was platinum/cerium 0.5/5 ppni/ppm. Field tests showed that the platinum concentration can be reduced to 0.25 ppm. A typical back pressure of the system at balance temperature is around 80 mbar. 

The NO reduction was measured when the platinum/cerium additive was used and it ranged from 15% in the beginning of the experimental programme. After the programme, the engine-out NO, emission was measured. This was approximately 20% below the engine-out emission before the start of the programme. 

Oh, S., Mitchell, R and Siewert, R. (1991). Methane oxidation over alumina-supported metal catalysts with and without cerium additives, J. Catal., 132, p. 287. 

Manganese oxide mesoporous materials were prepared by using template assisted method followed by an acidic treatment. The cerium addition to manganese oxide mesoporous stmcture was also studied. All the solids were characterized by XRD and specific surface area and pore size distributions were calculated from nitrogen sorption studies. XRD results suggested the formation of the Mn0x-Ce02 solid solution widi the fluorite-type stmcture. The BET surface area values and the pore size distributions allowed to conclude the important role of the surfactant by the creation of narrow mesopores in the material. 

---