An experimental facility for the examination of the preferential oxidation of carbon monoxide in the presence of a large excess of hydrogen

An experimental testing facility was developed for the study of the preferential oxidation of carbon monoxide in the presence of a large excess of hydrogen (PROX). The capabilities of the facility were utilized to test whether samples of a platinum and an iridium catalyst possessed the characteristics required in a PROX catalyst. A PROX reactor must completely remove CO from the gaseous fuel stream that is introduced to a proton exchange membrane fuel cell.; Two reactors were developed, and a numerical model was modified for use in this study. An integral reactor was constructed to screen potential catalysts and probe the effects of reaction conditions and changes in the inlet gas stream. The experimental facility was applied to study of a promoted, proprietary Pt-based catalyst in the integral reactor.; The results on the Pt-based catalysts demonstrated the utility of the integral reactor in PROX studies. Repeated tests failed to demonstrate CO conversion greater than 50% up to an inlet temperature of 200°C, the operational design limit of the catalyst. Further, irreparable damage was caused by a temperature excursion, suggesting a catalyst not suitable for the rigors of application. The CO conversion was not affected by the addition of CO ₂ or H₂O to the inlet stream. However, the O₂/CO ratio had a pronounced effect on the catalyst behavior.; A second suite of experiments demonstrated the utility of the CFR. The results demonstrated the unique capabilities of the CFR. The existence of reactions not detectable through examination of the inlet and outlet streams was demonstrated. Species concentrations at the catalyst surface and surface reaction rates were obtained.; The iridium catalyst surface was occasionally found to be covered in preadsorbed oxygen despite efforts to clean the surface. A stable and unreactive surface oxide (IrO₂) was present in the downstream portion of the catalyst. The IrO₂ covered surface promoted the water-gas shift and methanation reactions, while the clean surface was moderately active for oxidation reactions. However, the clean surface did not demonstrate high selectivity. Selectivity did not exceed 30% and decreased with increasing CO conversion. (Abstract shortened by UMI.)...