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Επίδραση του φορέα στην καταλυτική συμπεριφορά καταλυτών με βάση το Ir κατά την ξηρή αναμόρφωση του βιοαερίου

Palioudaki Georgia

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Summary

This MSc thesis aims at an experimental study of Ir catalysts, supported on various carriers for their performance, during the reaction of the dry reforming of biogas. Alumina (Al2O3), modified cerium oxide (CeO2) and zirconia oxide (ZrO2), are the three carriers involved in the study. The dry reforming of biogas utilizes biogas and carbon dioxide simultaneously, two extremely important pollutants for the production of composition gas, according to the following reaction:CH_4+CO_2↔2H_2+2CO, ΔΗ_298Κ^ο=247kJ/mol To be more precise, this study involves 1%Ir/GDC, 1%Ir/YSZ and 1%Ir/Al2O3 catalysts. Through conducting catalytic performance and stability experiments, it was aimed to be identified, not only the extent to which the carrier acts in the intrinsic activity of iridium, but also the stability exhibited by the catalyst over extended operating conditions.In conclusion, all three catalysts led to satisfactory results in the conversion of the reactants and the production of the products. Furthermore, they exhibited sustainable stability in long operating times, which indicates the resistance of iridium catalysts on carbon deposition.However, there were no effects of carriers in intrinsic activity of iridium, as they exhibit insignificant differences in performance and stability of the three catalysts. One of the most remarkable conclusions of this study comes from the repeated cycles of oxidation – reduction experiments. During these experiments, it was observed extreme stability of Ir in oxidation – reduction cycles, when it is supported on carrier containing CeO2. The remaining two carriers do not seem to feature any protective capacity of the catalyst. The catalyst though tends to be deactivated completely after applying in two reduction – oxidation cycles. This is observed particularly in the case of YSZ. This particular property of cerium oxide is practically significant, since oxidation – reduction cycles are often used in industrial practice to recover hydrocarbon reforming catalysts that have undergone extensive deactivation by carbon deposition.

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