Kinetics of hydrogen oxidation on Rh/Al2O3 catalysts studied in a stagnation-flow reactor

A newly established stagnation flow reactor with analysis of spatially resolved concentrations profiles is presented as useful tool for the investigation of heterogeneously catalyzed gas-phase reactions. The simplicity of this laboratory-scale reactor enables detailed modeling of the diffusive and convective transport within the one-dimensional gas-phase boundary-layer coupled with elementary-step homogeneous and heterogeneous reaction mechanisms. This set-up is applied to study the kinetics of hydrogen oxidation over Rh/Al2O3. By combining experimental and modeling results for a wide range of temperature and fuel/oxygen ratios, a thermodynamically consistent set of kinetic data for a 12-step surface reaction mechanism is derived. The applicability of the mechanism is further tested by the model prediction of experimentally derived ignition temperatures in a stagnation flow reactor and oxygen conversion in H2-rich hydrogen oxidation in an annular flow reactor at varying flow rate and temperature.

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► A stagnation-flow reactor set-up is proposed for studying catalytic kinetics.
► H2 oxidation over Rh/Al2O3 is studied experimentally and numerically.
► A thermodynamically consistent multi-step reaction mechanism is proposed.
► The reaction mechanism is successfully tested in a continuous annulus flow reactor.