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(42a) CH4 Conversion By Steam Reforming during Oxidation over Pt + Pd/Al2O3 Monolith Catalysts: Kinetic Model Development

Karinshak, K., University of Houston
Liu, R. F., CDTi Advanced Materials Inc
Grabow, L., University of Houston
Harold, M., University of Houston
Four-way catalysts are needed for stoichiometric natural gas vehicles (NGVs) emission control. Platinum group metal (PGM) based catalysts under lean/rich feed modulation and the addition of spinel oxides (AB2O4) to reduce the requisite PGM loading effectively convert CH4 in addition to CO, NOx and other hydrocarbons [1]. To further improve these catalysts we have developed a kinetic model for PGM + Mn0.5Fe2.5O4 spinel monolith catalysts that accounts for coupled conversion of CH4 by oxidation and steam reforming (MSR) along with water gas shift (WGS) in a near-stoichiometric feed. The kinetic model has been incorporated into a dual-layer monolith reactor model for optimizing catalyst formulation and the operation of stoichiometric NGVs emission.

A Langmuir-Hinshelwood type rate expression was used to model the MSR and WGS reactions. The MSR + WGS kinetic model output and experimental data are compared in Figure 1(a). The decrease in CH4 conversion with increasing CH4 feed concentration is caused by the faster formation of the inhibiting products CO and H2. To couple the MSR and WGS kinetics with CH4 oxidation reaction and incorporate into the monolith reactor model, we adapted the CH4 oxidation scheme from Chin et al. [2]. Figure 1(b) compares the preliminary results of a tuned, three global reaction model (oxidation, MSR and WGS) to collected flow reactor data. As the O2 concentration increases, the CH4 consumption rate reaches a maximum for a given temperature before rapidly decreasing, due to the rate inhibition by O2. Our reactor model containing the kinetics shows good agreement for CH4 conversion over a wide range of O2 feed concentrations and feed temperatures.


[1] S. B. Kang, K. Karinshak, P. W. Chen, S. Golden, M. P. Harold, Catalysis Today, 360 (2021) 284-293.

[2] Y. H. Chin, C. Buda, M. Neurock, E. Iglesia, J. Am. Chem. Soc., 133 (2011) 15958.