CFD Analysis of the Channel Shape Effect in Monolith Catalysts for the CH₄ Partial Oxidation on Rh

Abstract

Catalysts monoliths with circular and square ducts are theoretically analyzed in detail as reactor configurations for the adiabatic CH4 partial oxidation on Rh for short‐contact‐times hydrogen production. By the means of CFD coupled with a detailed microkinetic description of the surface reactivity, it was found that the different transport properties of the investigated configurations primarily affect the thermal behavior of the reactor. O2 consumption is fully external mass transfer limited, and thus, local variations in mass transport properties are responsible of the differences in surface temperature.

Stable Rh particles in hydrotalcite-derived catalysts coated on FeCrAlloy foams by electrosynthesis

“…CH 4 is converted by the exothermic total or partial oxidation reactions, and by the endothermic SR. On the whole, in diluted reaction conditions, the higher the Rh loading and coating thickness, the better the performances are. Considering that oxidation reactions are fast and controlled by O 2 mass-transfer [27], the differences in conversion and selectivity may be related to the ability of the catalyst to perform the consecutive SR reaction. A small amount of exposed Rh 0 active sites due to low Rh loading in the coating, the formation of large particles or the presence of unreduced Rh 3+ species, may decrease the CH 4 conversion by SR. For instance, in Rh5-c900 and Rh2-c900 catalysts, the activation observed with TOS suggests that the presence of some hardly reducible Rh 3+ species decreases their initial activity, while the reaction conditions may help to reduce some of them and enhance the performances.…”

“…From our results it appears that, despite the high temperatures reached in the catalytic bed, some Rh 3+ species are still present. The oxidation of CH 4 is a fast reaction and the consumption rate of O 2 is mass transfer limited [27]. However, the CH 4 molecule firstly has to be activated by the metallic particles.…”

“…The O 2 mass transfer and, therefore, the heat released by exothermic reactions is controlled by the size and shape of the channels in honeycomb monoliths [26,27]. In non-adiabatic reactors, radiative heat loss helps to decrease hot spots [28,29].…”

Evaluating Catalytic Fixed‐Bed Reactors for Dry Reforming of Methane with Detailed CFD

“…Consequently, first‐principles‐based multiscale modeling, as described by Dudukovic 16, of heterogeneous catalytic fixed beds has to combine a detailed description of the flow field, i.e., spatially resolved bed structure, with a detailed description of the reaction mechanism, i.e., micro kinetics. In recent years, this rigorous modeling approach was applied among others for multi‐channel catalysts 17, 18, catalytic gauzes 19 and catalytic foams 9, 20.…”

Effect of substrate geometry and flow condition on the turbulence generation after a monolith

“…However, both the shape of the whole substrate and the cross‐section of the channels are commonly limited to simple shapes. Reported works on channel shape optimization usually investigate only basic geometries such as square, circular, and triangular cross‐sections . Also, the entire substrate is typically cylindrical and the literature analyzing its shape optimization is sparse .…”