Catalytic Methane Combustion in Microreactors

The current thesis deals with the catalytic methane combustion in microreactors with wall-coated Pt/γ-Al2O3 catalyst. The Pt/γ-Al2O3 washcoat preparation, the single- and multi-layer catalytic coating systems, and the different designs of microreactor geometries were particularly investigated. Various aspects were thus addressed, including the preparation procedures of the catalyst coating (e.g., the binder properties, pH value, initial Al2O3 particle size), the optimization of different reaction conditions with single- and multi-layer coating systems (e.g., temperature, flow rate, O2/CH4 molar ratio, Pt loading and coating thickness), the effect of internal channel configurations in the microreactor (i.e., involving straight parallel channels, cavity, double serpentine channels, obstacled parallel channels, meshed circuit and vascular network) on the reaction performance. An obvious decrease in the methane conversion could be found over the multi-layer systems compared to their respective single-layer counterparts (if the Pt mass in the catalyst was kept equal), due to the more significant internal diffusion limitation in thicker coatings. Among all the tested microreactor geometries washcoated with Pt/γ-Al2O3 catalyst, the highest methane conversion could be obtained in the double serpentine channel microreactor and the lowest presented in the mesh circuit microreactor, which can be explained based on the available coating surface area, flow distribution and residence time property. In order to achieve a desirable methane conversion in microreactors, a proper tuning of the catalytic coating properties (e.g., surface area, Pt loading and thickness), the residence time, the fluid distribution uniformity and other reaction parameters (e.g., temperature and oxygen to methane molar ratio) are required.