(657g) Influence of Microwave Band Irradiation On Sulfur Poisoning in Catalytic Reforming Systems

Catalytic reforming of hydrocarbon fuels is frequently plagued by deactivation via carbon deposition and sulfur poisoning. Further deactivation may occur when catalysts are operated adiabatically without a sufficient exotherm to heat the catalyst and prevent oxidation of the active metal. The present study examines a means of dealing with hypothetical feed disturbance events and resulting deactivation from sulfur poisoning via irradiation of the catalyst in the microwave band (2.45GHz, λ=12.1cm). To probe interactions with electromagnetic radiation and to minimize internal field attenuation, a model system was chosen consisting of cordierite monolith supported catalysts, washcoated with a Ni/Ce_0.75Zr_0.25O­₂ catalyst. Propane was used as a model fuel due to its potential in portable power and chemical synthesis applications.  Sulfur was supplied to the reaction system in form of thiophene, with O/C and H₂O/C ratios chosen to represent scenarios where significant deactivation is expected.

Microwaves have been utilized in a vast array of processes over the past 60 years.  The ability to efficiently generate microwave radiation has led to energy savings in many drying, heating and cooking operations, particularly in food related applications.  Past research into zeolite and catalytic systems has examined the effects of microwaves on adsorbate equilibriums with the goal of altering equilibrium states.  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.  Despite beneficial effects, the large-scale application of microwaves in industrial adsorption and catalytic systems has remained limited.  Significant gaps exist in the understanding of microwave interactions in complex catalytic systems.

This contribution will present results of microwave band catalyst irradiation on: (i) changes in the product distributions and fuel conversion; (ii) carbon deposition; and (iii) catalyst morphology. 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.