(314e) Design and Testing of Microreactors for Kinetic Experiments of Catalytic Oxidation of Small Alkanes Over Platinum

Catalytic combustion of hydrocarbons has become an interesting technology based on its potential in distributed energy systems and portable power generation (1). For example, catalytic combustion of fuels, such as propane, butane, and jet fuel could provide the necessary heat to drive endothermic reactions, such as steam reforming or ammonia decomposition, for the production of hydrogen. In addition, it is the dominant chemistry in the upstream section of partial oxidation reactors. In order to design and study these multifunctional reactors, accurate kinetic parameters must be acquired. However, due to the high exothermicity and speed, it is very difficult to avoid heat and mass transfer limitations within conventional experimental reactors. As a result, there are significant discrepancies between experimental data within the literature. A catalytic microreactor was designed and fabricated for obtaining kinetic parameters of the catalytic oxidation of hydrocarbons. The microscale gap size allows for facilitated heat and mass transfer. The system is enclosed in a high thermal conductivity casing such that heat is dissipated evenly over the reaction zone. The packed bed catalyst is highly diluted in order to allow for the system to be controlled by kinetics . Detailed characterization of the catalyst has been performed. It was found that effective kinetic parameters depend on experimental conditions. For example, under fuel-lean conditions the rate is first-order in the fuel and negative-order in oxygen. The experimental kinetics of light alkanes are compared to a published reduced rate expression (2). In addition, a revised full microkinetic model (3) extended to larger hydrocarbons and network analysis will be discussed.

References:

1. J. A. Federici et al., J. Power Sources 161, 1469 (2006).

2. S. Deshmukh, D. G. Vlachos, Combustion and Flame 149, 366 (2007).

3. A. B. Mhadeshwar, D. G. Vlachos, Ind. Eng. Chem. Res. 46, 5310 (2007).