Co-impregnated Rh/Al sub 2 O sub 3. 2. Nitric oxide reduction and SO sub 2 poisoning

• Published in: Journal of catalysis 1991-03, Vol.128:1
• Main Authors: Hepburn, J.S., Stenger, H.G., Jr, Lyman, C.E.
• Format: Article
• Language: English
• Subjects: 01 COAL, LIGNITE, AND PEAT; 010800 - Coal, Lignite, & Peat- Waste Management; 20 FOSSIL-FUELED POWER PLANTS; 200202 - Fossil-Fueled Power Plants- Waste Management- Noxious Gas & Particulate Emissions; 400201 - Chemical & Physicochemical Properties; 540120 - Environment, Atmospheric- Chemicals Monitoring & Transport- (1990-); ADSORPTION; ALUMINIUM COMPOUNDS; ALUMINIUM OXIDES; CATALYST SUPPORTS; CATALYSTS; CATALYTIC EFFECTS; CHALCOGENIDES; CHEMICAL ANALYSIS; CHEMICAL REACTION KINETICS; CHEMICAL REACTIONS; COMPARATIVE EVALUATIONS; DEACTIVATION; DENITRIFICATION; DIFFUSION; ELECTRON MICROPROBE ANALYSIS; ELEMENTS; ENVIRONMENTAL SCIENCES; EQUATIONS; FLUE GAS; FLUORINE; GASEOUS WASTES; HALOGENS; HYDROGEN; INHIBITION; INORGANIC, ORGANIC, PHYSICAL AND ANALYTICAL CHEMISTRY; KINETIC EQUATIONS; KINETICS; MATHEMATICAL MODELS; METALS; MICROANALYSIS; NITRIC OXIDE; NITROGEN COMPOUNDS; NITROGEN OXIDES; NONDESTRUCTIVE ANALYSIS; NONMETALS; OXIDES; OXYGEN COMPOUNDS; PLATINUM METALS; POISONING; REACTION KINETICS; REDUCTION; RHODIUM; SELECTIVE CATALYTIC REDUCTION; SORPTION; SULFUR; SULFUR COMPOUNDS; SULFUR DIOXIDE; SULFUR OXIDES; TRANSITION ELEMENTS; WASTES
• ISSN: 0021-9517; 1090-2694
• DOI: 10.1016/0021-9517(91)90065-C

In the present study, the catalytic reduction of nitric oxide by H{sub 2} with eggshell and egg-white HF co-impregnated Rh on {gamma}-Al{sub 2}O{sub 3} honeycomb catalysts has been investigated to determine the effects of diffusion resistances on the rate and selectivity of the reduction reaction. Intrinsic kinetic data for NO reduction with H{sub 2} over Rh/{gamma}-Al{sub 2}O{sub 3} was measured at 165{degree}C and fit to a simplified Langmuir-Hinshelwood kinetic expression. The intrinsic kinetic model was used to develop a reactor model for NO reduction with Rh/{gamma}-Al{sub 2}O{sub 3} honeycomb catalysts. Theoretically predicted reaction rates and selectivities for the honeycomb catalysts were found to agree closely with measured reactor performance data. Poisoning the honeycomb-supported catalysts with SO{sub 2} showed that the eggshell and egg-white Rh catalysts deactivated at similar rates. Electron probe microanalysis (EPMA) of the poisoned catalysts revealed that sulfur was distributed throughout the support, indicating that SO{sub 2} is not limited by diffusion in this system. Analytical electron microscopy (AEM) confirmed a high degree of S/Rh coordination within the egg-white Rh honeycomb catalyst and much less coordination of sulfur with the alumina support. This was attributed to high concentrations of fluorine (1 to 2 wt%) deposited on the support from co-impregnation with HF. This fluorine is postulated to inhibit SO{sub 2} adsorption onto the support surface.