Influence of Microwave Band Irradiation On Catalytic Reforming Systems Operating Under Deleterious Conditions

In catalyst systems microwave radiation has been shown to increase reaction rates, lower the bulk temperature at which reactions occur, and assist in the desorption of sulfur.  Past research into zeolite and catalytic systems has examined the effects of microwaves on adsorbate equilibriums with the goal of altering equilibrium states.  Despite beneficial effects, the large-scale application of microwaves in adsorption and catalytic systems has remained limited.  Significant gaps exist in the understanding of microwave interactions in complex catalytic systems.

The present study on Ni-based reforming catalysts examines the influence of irradiation in the microwave band (2.45GHz, λ=12.1cm) on carbon deposition. Catalytic reforming of hydrocarbon fuels is frequently plagued by catalyst deactivation via carbon deposition, sulfur poisoning, and oxidation of metal surface sites. To probe interactions with electromagnetic radiation a model catalyst system was chosen consisting of cordierite monolith to minimize internal field attenuation, washcoated with a Ni/Ce_0.75Zr_0.25O­₂ catalyst.  Autothermal reforming of a mixture of propane and ethylene was used in this study with O/C and H₂O/C ratios chosen to create reaction conditions where significant deactivation due to carbon deposition would be expected.  Experiments were performed in a single mode microwave cavity varying the source power from 0-900Watts with continuous monitoring of the effluent using an electron ionization mass spectrometer.  The results of microwave band catalyst irradiation on: (i) Carbon deposition and morphology, and (ii) changes in the product distributions and fuel conversion are discussed.