Chemical Engineering Science 63 (2008) 1098 – 1116 www.elsevier.com/locate/ces Stability and performance of catalytic microreactors: Simulations of propane catalytic combustion on Pt Niket S. Kaisare, Soumitra R. Deshmukh, Dionisios G. Vlachos ∗ Department of Chemical Engineering, Center for Catalytic Science and Technology (CCST), University of Delaware, Newark, DE 19716, USA Received 27 February 2007; received in revised form 23 October 2007; accepted 3 November 2007 Available online 17 November 2007 Abstract A pseudo-two-dimensional (2D) model is developed to analyze the operation of platinum-catalyzed microburners for lean propane–air combustion. Comparison with computational ﬂuid dynamics (CFD) simulations reveals that the transverse heat and mass transfer is reasonably captured using constant values of Nusselt and Sherwood numbers in the pseudo-2D model. The model also reasonably captures the axial variations in temperatures observed experimentally in a microburner with a 300 m gap size. It is found that the transverse heat and mass transport strongly depend on the inlet ﬂow rate and the thermal conductivity of the burner solid structure. The microburner is surface reaction limited at very low velocities and mass transfer limited at high velocities. At intermediate range of velocities (preferred range of reactor operation), mass transfer affects the microburner performance strongly at low wall conductivities, whereas transverse heat transfer affects stability under most conditions and has a greater inﬂuence at high wall conductivities. At sufﬁciently low ﬂow rates, complete fuel conversion occurs and reactor size has a slight effect on operation (conversion and temperature). For fast ﬂows, propane conversion strongly depends on residence time; for a reactor with gap size of 600 m, a residence time higher than 6 ms is required to prevent propane breakthrough. The effect of reactor size on stability depends on whether the residence time or ﬂow rate is kept constant as the size varies. Comparisons to homogeneous burners are also presented.  2007 Elsevier Ltd. All rights reserved. Keywords: Catalytic combustion; Energy; Fuel; Simulation; Microburner extinction; Propane 1. Introduction The growing interest in hydrocarbon-based sources for de- centralized power generation and as replacements of existing batteries (Fernandez-Pello, 2003; National Research Council, 2004) has spawned a signiﬁcant research effort in small-scale homogeneous (Kim et al., 2007; Miesse et al., 2004) and cat- alytic reactors (Kolb and Hessel, 2004, Norton et al., 2004, 2006, Ouyang et al., 2005; Pattekar and Kothare, 2004; Rebrov et al., 2001; Srinivasan et al., 1997). These micro chemical systems are used either for generation of hydrogen for fuel cells (Deshmukh et al., 2004; Deshmukh and Vlachos, 2005; Ganley et al., 2004; Karim et al., 2005; Kolios et al., 2005; Tonkovich et al., 2007) or for direct conversion of ther- mal energy released via combustion to electrical energy using ∗ Corresponding author. Tel.: +1 302 831 2830; fax: +1 302 831 1048. E-mail address: vlachos@udel.edu (D.G. Vlachos). 0009-2509/$ - see front matter  2007 Elsevier Ltd. All rights reserved. doi:10.1016/j.ces.2007.11.014 thermoelectrics (Federici et al., 2006) or thermo-photovoltaics (Yang et al., 2004). Hydrocarbon combustion is typically needed to ensure autothermal operation of these devices. Homo- geneous combustion is often the preferred mode of operation at larger scales, for example, in power plants (Kiameh, 2002) and industrial reformers for hydrogen production (Udengaard et al., 1995). However, the situation rapidly changes at smaller scales due to the high surface area to volume ratio. While homoge- neous combustion becomes less stable due to thermal and rad- ical quenching (Aghalayam et al., 1998, Norton and Vlachos, 2003, 2004, Raimondeau et al., 2003), faster mass transfer can potentially result in high effective rates of catalytic reactions (Jensen, 2001). We previously studied homogeneous combustion of stoichio- metric methane–air and propane–air mixtures in microburners (Norton and Vlachos, 2003, 2004) (i.e., burners with charac- teristic dimension less than 1 mm). The burner solid structure had a signiﬁcant inﬂuence on the stability (Leach and Cadou,