(337f) Spatially-Resolved Species Profiles in Millisecond Reactors: Catalytic Partial Oxidation of Methane

A new method for measuring spatial species and temperature profiles inside foam monoliths has been developed for the examination of millisecond-contact time reactors. Species are sampled via a small-diameter (0.7mm) fused silica capillary in a slightly larger channel drilled axially through the catalytic foam monoliths. Temperatures are measured at the location of species sampling with a small diameter thermocouple (0.25mm) that is inserted inside the fused silica capillary. Precise axial positioning of the sampling orifice is achieved by a computer-controlled linear translation stage giving > 40 data points in a 10mm long catalyst. The reactor effluent flow is pumped through the capillary and analyzed using a quadrupole mass spectrometer giving real time species data at each sampling location. The sampling technique has a minimal impact on the reacting system because the sampled gas volume (< 10ml/min) is very small compared to the total reactor flow (> 5000ml/min), and the annular space between the capillary and monolith is approximately the same as the average pore size.

Steady state methane partial oxidation has been examined around the syngas stoichiometry as a function of preheat on rhodium coated alumina monoliths. The results of these experiments show very interesting structure within the catalyst. First there is an oxidation zone lasting 2-3 mm in which all oxygen is consumed and a considerable amount of syngas is produced. Next there is a reforming zone in which water and methane are consumed giving H₂ and CO in the approximate methane steam reforming stoichiometry. A peak in temperature is generally observed in the middle of the catalyst towards the beginning of the reforming zone indicating the beginning of endothermic chemistry in the catalyst.

This novel method for collecting species and temperature can be used to gather a large amount of data within the catalyst for steady state experiments (e.g. for methane and other fuels) which will be very useful for validating and updating existing reaction mechanisms. Because of the fast response of the data collection scheme, this experimental system also lends itself to the analysis of transient experiments which can be even more powerful for validating reaction mechanisms and carbon coverages within the catalyst.