(491c) Methane Partial Oxidation over a Rh-Containing Monolith Studied by Spatially Resolved Intra-Channel Species and Temperature Measurements

Fuel reformers are important for advanced power generation technologies. A high profile reformer application is the conversion of hydrocarbons into hydrogen for use in fuel cells. Due to its simple reactor design, rapid lightoff, and ability to convert various hydrocarbons, partial oxidation using noble metal catalysts is an alternative to conventional steam reforming for distributed hydrogen generation. Although substantial progress has been made in recent years, this technology still requires significant improvement in catalyst design and system engineering, which in turn necessitates mechanistic and kinetic process details. However, the underlying kinetics and reaction mechanisms have proven difficult to elucidate due to the highly exothermic and non-isothermal nature of the process. Moreover, mass transfer often controls reforming reactions. As a result, data found in the literature are not always explained without ambiguity and reactor-outlet composition and temperature measurements often lead to highly convoluted data whose interpretation is not straightforward. In this respect, the ability to measure the composition and temperature profiles inside a working reformer is highly desirable for elucidating underlying mechanisms and kinetics. To the best of our knowledge, such intra-reactor data are absent in the literature. In this study, we have applied two minimally invasive techniques to resolve species and temperature profiles along a rhodium-containing washcoated monolith during methane partial oxidation. Spatially Resolved Capillary Inlet Mass Spectrometer (SpaciMS) was used for species measurements and fiber-coupled pyrometry was used for temperature measurements. Thermocouple was also used for comparison. The results show that SpaciMS and fiber-coupled temperature probe can measure useful information under realistic reformer conditions. In particular, the combined intra-channel species and temperature measurements provide a clear picture of how the partial oxidation process evolves axially along the catalyst. At the front portion of the monolith, a fraction of the methane undergoes total oxidation consuming all the oxygen available and producing CO2, H2O and a significant exotherm. Further downstream, the total oxidation product H2O and the released heat are used for steam reforming of the remaining methane to produce hydrogen and carbon monoxide. In this presentation, we will discuss how the space velocity affects the species and temperature distribution along the catalyst length during partial oxidation. These will be compared with modeling results. Moreover, we will describe in detail the SpaciMS and pyrometry techniques that appear, as a result of this study, to be valuable tools for reformer research, design, and modeling.