Kinetics of the water-gas shift reaction over Rh/Al2O3 catalysts

• Experimental and numerical study on preferential CO oxidation, WGS and RWGS over Rh catalysts.
• Thermodynamically consistent surface reaction kinetics presented.
• Stagnation-flow reactor set-up proposed as lab reactor for studying catalytic kinetics.
• Applicability of the reaction kinetics successfully tested by modeling WGS and RWGS in tubular flow reactor.

The kinetics of the water-gas shift (WGS) reaction over Rh/Al2O3 catalyst is studied experimentally and numerically. Using the experimentally determined conversion in WGS, reverse WGS, and preferential oxidation of CO over a catalytically coated disk and over a honeycomb monolith, a thermodynamically consistent multi-step reaction mechanism with the associated rate expressions was developed. Both the experimental configurations were numerically simulated coupling models for the flow field with this heterogeneous reaction mechanism. The main reaction path for CO2 formation on this catalyst is concluded to be the direct oxidation of CO with O species at high temperatures, whereas the formation of the carboxyl (COOH) group is significant at temperature below 600 °C. The reaction kinetics reproduced the experimental observations, also for the subsystems of hydrogen and CO oxidation.

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