The proposed work uses an innovative technique to investigate the chemical kinetics and mechanisms of catalytic reactions by combining a high pressure shock tube normally used for homogeneous reaction analysis and adapting it to study heterogeneous reactions. This technique will resolve the mechanistic uncertainties that have evolved using conventional continuous flow techniques and through their resolution lead to potentially significant impacts on energy generation and the quality of the environment.
The new technique incorporates a catalyzed short contact time (SCT) reactor substrate into a high pressure single pulse shock tube. The combination of a SCT reactor and shock tube enables the study, by detection of intermediates, of the mechanism of complex heterogeneous reactions over a catalyst for very well defined times and conditions in the absence of transport effects that plague conventional techniques. The mechanistic understanding arising from the unique conditions of the shock tube will facilitate a smooth transition in scale-up from the lab to industrial applications where high pressures are necessary for increased process throughput.
One example of the mechanistic information that will be the focus of the proposed work is the resolution of the routes to synthesis gas (an alternate energy source) during the Catalytic Partial Oxidation (CPOX) of methane. One hypothesized route is through a partial oxidation step which must be terminated, for syn-gas production, before complete oxidation. This route can be established by detection of CO and H2 before CO2 formation. An alternative route is through complete oxidation to CO2 followed by secondary reforming to syn-gas which can be evaluated through measurements of the relative rates of the co-formation of CO2 and CO/H2.
Another mechanistic problem to be addressed arises in the catalytic reforming of the green house gas CO2 with methane. Although the atmospheric pressure, water free mechanism of this process has been established its relevance to practical process conditions has not. Process conditions would probably require the use of steam to suppress carbon formation on the reforming catalysts and elevated pressure to increase throughput. A catalytic process operating at elevated pressure with water addition will almost certainly involve a different mechanism than the one already established. Detection and quantification of key oxygenated intermediates, such as methanol and formaldehyde, by the new technique of combining a SCT reactor with a high pressure single pulse shock tube will establish the mechanism and guide practical reactor design.
Broader impacts and Societal Benefits 1) Elucidation of the mechanism of catalytic partial oxidation of methane to synthesis gas for its use as an alternative energy source in environmentally friendly processes. 2) Optimization of methane reforming of carbon dioxide potentially leading to the reduction of these greenhouse gases. 3) Development and evaluation of a novel short contact time reactor/single pulse shock tube methodology for studying catalytic reactions important to maintaining a clean living environment. 4) Development of catalytic methods at high pressures for increased process throughput. 5) Investigation of alternate catalysts for CPOX and CO2 reforming. 6) Education of graduate students in the cross disciplinary fields of catalytic chemistry, environmental science, high pressure shock tube experimentation and reaction engineering.
