Search

Browse

• Communities
• Authors
• Year
• Titles
• Subjects

My Space

• Login

The effect of x% Al2O3 -y% CeO2 -z% ZrO2 (ACZ) mixed oxide support composition on thermal stability and activity (in CO oxidation) of Ir-based catalysts prepared by wet impregnation method

Gkiata Ourania

Full record

---

Summary

One of the three major pollutants, that a three-way catalytic converter has to deal with, is CO. CO to CO2 conversion, is a simple reaction that has been studied extensively in recent years. Of particular interest, is the use of Iridium catalysts in Environmental Catalysis and more specifically in the oxidation of CO. Iridium is a relatively inexpensive noble metal, whose tendency for agglomeration in the carrier was the main obstacle to its application. Research has shown the ability of high oxygen storage capacity (OSC) carriers to stabilize Ir. In the present thesis, the effect of the support on the activity and thermal stability of Ir-based catalysts under CO oxidation was studied. More specifically, the effect of 60wt% Al2O3 - 40wt% CexZr(1-x)O2 (ACZ) mixed oxide support with varying Ce/Zr composition (x=0, x=0.25, 0.5 and 0.75) was investigated in detail. Alumina-Ceria-Zirconia (ACZ) mixed oxide supports were synthesized by co-precipitation, while Iridium loading 1wt% was incorporated by wet impregnation method. Catalysts were studied in the temperature range of 100-450°C under conditions of excess oxygen. Their catalytic activity was studied under two different pretreatment conditions a) in reducing and b) in oxidizing conditions. Moreover, thermal stability experiments took place at the temperature of 320°C, after thermal aging conditions. At the same time, physicochemical properties of catalysts were analyzed through different characterization techniques (Brunauer-Emmett-Teller (B.E.T), Hydrogen Temperature Programmed Reduction (H2 – TPR), Η2 Chemisorption and Χ - Ray Powder Diffraction method (XRD)). According to the results, it can be said that Ir/ACZ catalysts are very effective in CO oxidation and they keep their thermal stability in the studied conditions. Moreover, it seems that catalysts behavior is better at their pre-reduced condition. Alumina supports seems to be more active over the maximum conversion temperatures of the pollutant. However, the increase of ZrO2 seems to reduce the reverse phenomenon, that is most observed at the pre-reduced catalysts. These results are very promising for future application, under the condition of further study in more difficult reactions.

Available Files

Services