On The Partial Catalyst-Coating Of Monoliths for High Pressure Methane Combustion: An Experimental and Modeling Approach

Catalytic combustion is a valuable route to generate power with near-zero emissions and through an inherently safe operation. However, a commercial breakthrough has never been attained mainly for cost and durability limitations of catalytic materials. The occurrence of combustion at the catalytic surface poses serious thermal management issues associated with the generation of hot spots and consequent catalyst aging and/or deactivation, eventually affecting the lifetime of the catalyst itself. Computational Fluid Dynamis (CFD) has demonstrated itself to be a powerful tool to simulate the occurrence of temperature excursions over the catalyst as a result of complex interplay among fluid flow, chemical reaction and heat exchange. Hence, through the use of CFD models, it is possible to gain more information about the phenomena that take place in catalytic combustors and also to develop novel reactor configurations. By developing a two-dimensional CFD model, we successfully simulated both steady and unsteady behavior of a 20 wt. % LaMnO3/La-?-Al2O3 catalytic monolith fueled with methane and operated at high pressure. In particular, simulation results have demonstrated the strongly synergistic coupling established between gas-phase and catalytic reactions. Starting from these results, we have showed that complete fuel conversion can be obtained in novel partially catalyst-coated honeycomb reactors. In particular, in the "core-shell" reactor configuration we proposed, the catalyst is deposited only over the external channels, thus allowing for cost saving. Catalytic reactions are responsible for activation of homogeneous reactions, and fuel ignition first takes place in the coated channels and then in the un-coated ones (thanks to radial heat transfer). We experimentally prepared these novel catalytic monoliths and successfully tested them for high-pressure methane combustion. This work reviews the most relevant results of the modeling/experimental activity we carried out, highlighting the importance of CFD when coupled with appropriate experimental campaign.