H2 production by methane steam reforming over Rh/Al2O3 catalyst packed in Cu foams: A strategy for the kinetic investigation in concentrated conditions

The concept of Rh/Al2O3 catalyst pellets packed in highly conductive copper foams has been successfully tested in methane steam reforming showing the beneficial effects of thermal conductivity on the obtainment of gradient-less radial temperature profiles. In this work, the same concept is proposed as a strategy for the lab-scale kinetic investigation under concentrated conditions at ambient pressure; thanks to the homogeneous heating of the catalyst mass across the reactor section and the measurement of axial temperature profiles, well-controlled temperature conditions are obtained, and the experimental investigation can be extended to usually unfeasible conditions of high reactant concentrations, overcoming the typical challenges for the kinetic study. Here, steam reforming experiments were performed with CH4 and H2O feed molar fractions in the ranges of 10-20 % and 40-90 %, respectively. The co-feed of CO and H-2 was also investigated. A kinetic scheme was developed that substantially confirmed the main results of previous kinetic investigations in annular micro-reactor, performed under diluted conditions; in particular, the first order dependence of the rate of steam reforming on methane partial pressure, the independence from H2O partial pressure, and the important inhibiting effect of CO were confirmed. The independence of the reaction rate from the H-2 co-feed was here demonstrated for the first time. The new experimental campaign allowed to identify more clearly the kinetic dependencies of the water gas shift reaction, positively influenced by H2O partial pressure but scarcely affected by CO partial pressure, which could be also explained based on the inhibiting effect of surface CO coverage. Parameter estimates were obtained by model fit over a wide temperature range (400-850 degrees C), conveying robustness to the proposed kinetic scheme for future reactor design applications.