Experimental and Modeling Analysis of the Thermal Behavior of an Autothermal C₃H₈Catalytic Partial Oxidation Reformer

Abstract

In this work, a spatially resolved sampling technique is applied to characterize the performance of a C3H8 CPO reformer and to compare it with that of a CH4 reformer. The case of Rh-coated honeycomb catalysts is examined. The axial profiles show that higher temperatures are reached in C3H8 CPO, especially at the reactor inlet. Surface hot-spot temperatures around 950 °C lead the catalyst to rapid loss of activity. A detailed model analysis is also applied to better understand the reasons for the observed differences of the thermal behavior. On one hand, the heat release via oxidation reactions is controlled by O2 mass transfer rate and thus proportional to O2 inlet concentration, which is 20% higher in the C3H8/air mixture at equal C/O ratio. On the other hand, while CH4 steam reforming is partly chemically controlled, C3H8 steam reforming is mainly limited by gas–solid diffusion. Thus, a less efficient balance between exo- and endothermic reactions occurs in the case of C3H8 CPO, and this results in much higher hot-spot temperatures. As a consequence, specific strategies for the optimization of the thermal behavior are required depending on the fuel. Modeling of the C3H8 CPO results shows that an increased catalyst load or a suitable aspect ratio of the reactor, combined with a decrease of the flow rate, produces a beneficial moderation of the hot-spot temperature of the catalytic wall

Spatial Concentration Profiles for the Catalytic Partial Oxidation of Jet Fuel Surrogates in a Rh/Al2O3 Coated Monolith

“…Compared to former studies of CPOX of methane on Rh [10,12,18,21,35] and propane on Rh [14,35], the two major observations of this study for higher hydrocarbons have not been reported: the extended region for consumption of oxygen and the delayed formation of hydrogen. For DD and all other fuels which were investigated within our study, we clearly see an indirect formation route for hydrogen via water as intermediate, as has already been suggested for e.g., high hydrocarbons [22].…”

“…For higher hydrocarbons as a fuel, the adsorption and activation of hydrocarbons on the catalytic surface plays an important role in the first reaction zone. CO 2 and H 2 O are formed as total oxidation products in this region, which is true for all studies on CPOX of hydrocarbons [10,12,14,18,21,35]. For CPOX of DD and TMB, CO generation was also observed but no hydrogen.…”

“…Higher hydrocarbons have shown a tendency to form cracking products, which is mainly due to gas-phase reactions, occurring at high temperatures and fuel rich conditions [14,27,35,41]. In several studies on CPOX of higher hydrocarbons, the influence of gas-phase reactions is already unraveled on the product gas yield [22,[41][42][43].…”

Multiscale modeling of methane catalytic partial oxidation: From the mesopore to the full‐scale reactor operation

“…This evidence is in agreement with the lower contact times (shorter reactors) that are required to reach the thermodynamic equilibrium by increasing the effective diffusivities and catalyst loading/dispersion (see Figures a–d). These trends on effective diffusivities and active surface area are responsible for weakening the effects of pore diffusion on the overall regime governing the macroscale performance, in such a way that the full‐scale reactor becomes gradually controlled by the regimes observed in the absence of diffusion limitations: external transport of O 2 for the oxidation reactions and a mixed external transport–kinetic regime for CH 4 consumption through reforming reactions …”

Thermal Deactivation of Rh/α-Al2O3 in the Catalytic Partial Oxidation of Iso-Octane: Effect of Flow Rate

“…The coating proceeded through the dip-coating technique. Further details on synthesis methodology can be found elsewhere [34].…”