Microwave-Catalyst Interactions in the Reforming of Hydrocarbons.

Portable reforming technology for the production of synthesis gas (CO & H2) from hydrocarbons has the potential to be used in distributed chemical manufacturing, emissions control and engine cold-start technology, as well as in portable power generation in conjunction with fuel-cells. Catalytic reforming of hydrocarbon fuels is frequently plagued by deactivation via carbon deposition and sulfur poisoning. Performance further degrades when catalysts are supplied with non-ideal feed gas compositions. The present study examines a method of dealing with hypothetical feed disturbance events and resulting deactivation by irradiation of the catalyst in the microwave band (2.45 GHz). A high temperature microwave reactor was constructed to probe interactions of electromagnetic radiation with catalysts consisting of cordierite monoliths washcoated with Ni on a Ce-Zr mixed oxide. Reaction conditions were selected to promote carbon deposition with low O/C and H2O/C ratios using propane and ethylene as the fuel. Irradiation of active reforming catalysts was found to alter product distributions and carbon deposition. Experiments were conducted to probe the effects of microwave irradiation on product distributions and carbon deposition while operating under regimes of partial-oxidation and autothermal reforming with and without sulfur present in the form of thiophene. Comparisons were drawn between irradiated samples and samples exposed to elevated temperatures within a furnace to extract microwave specific heating effects. The microwave-heating environment was found to exhibit unique effects dependent upon the feed composition. Volumetric microwave heating was found to reduce the prevalence of cracking and dehydrogenation products in sulfur poisoned experiments while supplying energy to the typically heat-transfer-limited steam-reforming region of the catalyst. Microwaves were found to couple strongly to carbon, resulting in selective oxidation of carbon deposits when sufficient oxygen is available. Similarly, product distributions were found to change based on enhanced steam-reforming and water-gas shift activity resulting from volumetric heating of the catalyst and reduced entrance region temperatures. Finally, several methods for estimating the temperature rise experienced by an irradiated reforming catalyst are presented to gain further insight into the conditions experienced when reforming hydrocarbons within an electromagnetic field.PHDChemical EngineeringUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/97871/1/edmundst_1.pd