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Biogas reforming on Ni catalyst supported on CeO2 synthesized with different methods

Pavlineri Maria

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Summary

This diploma thesis concerns the study of biogas reforming using monometallic nickel (Ni) catalysts supported on cerium oxide (CeO₂), with different nanostructures. The aim of the research is to evaluate the catalytic activity and stability of these catalysts in the dry reforming of methane (CH₄) with carbon dioxide (CO₂), a promising technology for the production of synthesis gas (syngas) while simultaneously reducing greenhouse gas emissions. The theoretical background of the dry reforming of methane is presented, which is a catalytic reaction that converts CH₄ and CO₂ into syngas, holding particular importance for energy utilization and environmental management of greenhouse gases.The properties of the CeO₂ supports are also examined, as well as the effects of different synthesis methods on the structural and catalytic behavior of the materials. In the experimental section, cerium oxide (CeO₂) supports were synthesized using various methods and were subsequently used for the preparation of monometallic nickel catalysts with a 10 wt.% metal loading (10 wt.% Ni/CeO₂) and characterized using XRD and BET techniques, in order to determine their crystalline structure and specific surface area. The catalytic activity of the materials was then evaluated in the dry reforming of methane over a temperature range of 350–750°C, under equimolar reactant composition (CH₄/CO₂ = 50%:50%) and a total flow rate of 50 cc/min. Catalytic stability was studied under continuous operation conditions for 30 hours at 750°C. The results showed that the preparation method significantly affects catalytic performance, with certain catalysts exhibiting high CH₄ and CO₂ conversion and increased resistance to carbon deposition. The 10% Ni/CeO₂ catalyst, whose CeO2 support was prepared by the hydrothermal method, demonstrated the highest activity, approaching the maximum conversion values (approximately 85%) according to the thermodynamic equilibrium curve of the DRM reaction reported in the literature. The 10% Ni/CeO₂ catalyst, whose CeO2 support was prepared by the precipitation method, and the 10% Ni/CeO₂ catalyst, whose CeO2 support is commercially available, showed lower conversion rates, approximately 30% and 50% respectively. Furthermore, regarding the stability of the Ni/CeO₂-Pr catalyst, a significant decline in performance was observed after prolonged operation at 750°C. In conclusion, this study contributes to the understanding of the relationship between the synthesis method of Ni/CeO₂ catalysts and their performance in the dry reforming of methane, offering valuable insights for the development of more efficient and durable catalytic systems for the sustainable production of synthesis gas.

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