(460i) In-Situ Spectroscopic Analysis of Adsorbents for Desulfurization of Industrial Reformate Gases for Application in Low Temperature PEM Fuel Cells

Chemical industries have supplied us with plastics, fertilizers, pharmaceuticals, detergents etc. These products are manufactured in large chemical plants & the production is monitored via temp, pressure & flow alone. However, chemical composition is mostly analyzed separately. This implies that sample analysis could be done at a later time and/or even away from the process. The time for analysis may cause a waste in raw materials & energy if an undesired product quality is obtained. With the advent of fiber optic spectroscopy, you can now look into the process. This would enable to adjust the process variables to prevent waste of material and energy. This technology is environmentally friendly too. Our focus is on the desulfurization process of reformate gases for applications in low temp PEM fuel cells as one of the clean energy sources in the future. Industrial hydrocarbon gases may contain between less than 1 PPM & close to 10,000 PPM of hydrogen sulfide (H₂S) depending on the geographical sources of these gases. H₂S is a poison for metallic catalysts in other fuel processing units & its concentration in feed stocks must be reduced to sub PPM levels. To achieve this, zinc oxide based sorbents have been employed for decades in the industry. At low temp (<100°C), nanostructured ZnO exhibits higher reactivity with H2S in comparison with classical sorbents made of micro-meter ZnO particles. Recently, this reactivity at low temp was improved by doping the ZnO based sorbents with transition metals like Mn, Fe, Co, Ni or Cu oxides allowing an increase in breakthrough capacity for H₂S capture. There is a color change with the adsorption of sulfur compounds providing a visual indication of the impending breakthrough.  The dopant could be used as an efficient center for optical absorption in the UV-Vis region. Thus, optical Spectroscopy in this region is useful to study the process. Real-time synthesis, adsorption & desorption tests on these particles are discussed with the idea of operando spectroscopy emphasized for similar domains of work.