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Activity of perovskitic materials in conjunction with Ir in CO oxidation

Nikolaou Vasileios

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Year 2021
Type of Item Diploma Work
Bibliographic Citation Vasileios Nikolaou, "Activity of perovskitic materials in conjunction with Ir in CO oxidation ", Diploma Work, Department of Chemical and Environmental Engineering, Technical University of Crete, 2021
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One of the most important reactions in the catalytic converter and in the heterogeneous is the oxidation of CO, i.e. the process of its conversion to CO2. The right metal/support combination is very important for maximum CO conversion efficiency at low temperatures. Ir (Iridium) is a relatively inexpensive noble metal and a very promising material in the field of environmental catalysis, as well as for the oxidation reaction of CO. According to recent studies, Ir particles are "stabilized" at high temperatures in excess oxygen. In the present thesis the catalytic properties of the perovskite oxides with chemical formula La1-xSrxMnO3 (x=0, 0,3, 0,5 and 0,7) (or LSMxx) in a support role in combination with the active phase of the noble metal Ir. The Ir/La1-xSrxMnO3 catalysts were studied in the temperature range of 100-450oC under conditions of excess oxygen. LSM supports were synthesized by co-precipitation, Iridium loading of 2wt% was incorporated on the LSM supports using the conventional wet impregnation method. Their catalytic activity was studied under different pretreatment conditions (in reducing and oxidizing conditions). At the same time, catalyst characterization techniques (by the Brunauer-Emmett-Teller (BET) method, powder X-ray diffraction (XRD) method and hydrogen temperature programmed reduction (H2-TPR) ), an attempt was made to understand how it is related the structure, activity and stability of Ir/LSMxx. Catalytic activity and stability experiments were performed on pre-oxidized, pre-reducing and aging catalysts. According to the results of the experiments, Ir/LSMxx catalysts were found to be particularly effective in CO oxidation in the temperature range 100-450oC. The Ir/LSMxx catalyst was significantly more active than the LSMxx and particularly in their pre-reduced situation. The increase in Sr content in LSM supports does not further enhance the catalytic oxidation of CO, however it reduces the hysteresis phenomena observed in CO oxidation. In addition, it was found that, despite the aging of the catalysts at high temperatures (600 & 750oC) in conditions of excess O2, Ir/LSMxx almost show excellent thermal stability. These results are very promising for future application of these materials in other reactions.

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