(626g) The Investigation of the Catalytic Partial Oxidation of Methane in a Shock Tube

Robyn E. Smith¹, Marco J. Castaldi¹, Kenneth Brezinsky2

¹Department of Chemical Engineering, The City College of New York, City University of New York, New York, NY 10031

²Department of Mechanical and Industrial Engineering, The University of Illinois at Chicago, Chicago, IL 60607

Introduction

The societal and environmental drive to become an energy and resource conscious world has lead to significant research concentrating on uncovering new methods of producing and utilizing energy. This can be done successfully by using catalytic processes to improve current and generate new methods. The production of synthesis gas from methane is one example, where the existing technology utilizes the steam reforming of methane to generate syn-gas, however this method requires continuous energy input. Conversely, the catalytic partial oxidation of methane, which also produces syn-gas, generates energy as a product of reaction, therefore is a more energy conscious method.

However, the chemical kinetic mechanism of the catalytic partial oxidation of methane has long been debated in scientific literature. This is a seemingly simple reaction proceeding through either partial oxidation followed by complete oxidation^1â??5 or complete oxidation followed by reforming steps^6â??12. This dispute is due to the complexity of the catalytic cycle, which becomes further convoluted when comparing the reaction performance data over various catalyst conformations. This study focuses on the effects that catalyst conformation has on the performance of the catalytic partial oxidation of methane using a unique shock tube apparatus to generate short reaction times in stagnant reaction conditions.

Experimental Results

In these experiments, a mixture of dilute methane and oxygen were reacted in a shock tube at temperatures and pressures ranging from 1030-1200 K and 2.3-2.8 bar. The reaction times varied between 2.3 and 6.4 milliseconds. Experiments over a platinum on γ-alumina catalyst in a conventional configuration was compared to those using a fixed catalyst. For direct comparison, the performance of each catalyst was defined by the conversion of methane to products per catalyst weight.

Product gas analysis unveiled that the performance of the conventional catalyst was two orders of magnitude higher than that of the fixed catalyst. The results also showed that methane conversion corresponded to the production of carbon dioxide without the production of carbon monoxide for all temperatures, pressures, reaction times and both catalyst conformations. This second finding suggests that the mechanism for the catalytic partial oxidation of methane over both catalyst configurations goes through complete oxidation followed by reforming steps.

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