Palladium catalysts on alumina and ceria supports have been reported in the literature to be effective in oxidizing methane and carbon monoxide in exhaust gases above 4500C. The main objective of this project is to develop palladium catalysts on alumina and ceria-alumina mixed supports for low temperature catalytic combustion of methane. Two catalysts [5% Pd/y-alumina (5-Pd/Al2O3) and 5% Pd/20% ceria-y-alumina (5-Pd 20-CeO2/Al2O3)] were prepared by a modified syringe pump injection-vortex method for intense mixing and better dispersion. For the preparation of 5-Pd/Al2O3 catalyst, a slurry of the y-alumina support and water was made in a vortex tube, and palladium nitrate hydrate solution was pumped at the rate of 20 uL/min from an injection syringe and syringe pump. For the 5-Pd 20-CeOx/Al2O3 catalyst, the same method was followed except that a precursor solution of palladium nitrate hydrate and cerium nitrate hexahydrate was added to the alumina slurry. Both catalysts were dried at 1050C and then calcined at 5000C for 5 hours. The catalyst were characterized by Brunauer-Emmett-Teller (BET), and pulse chemisorption. The properties of both catalysts were similar [total surface area, 114-132 m2/g; dispersion, 18.3-18.7%; particle size, 6.0 nm]. The activity experiments were conducted in a temperature-controlled fixed bed flow reactor. Two reacting gas mixtures [a stoichiometric gas mix of 1% CH4, 4% O2, balanced N2; and a simulated diesel exhaust containing 1% CH4, 5.5% CO2, 9.1% O2, balanced N2] and a gas hourly space velocity of 45,000 cc/g.catalyst.hr-1 were used. The conversions of methane by both gas mix were similar in the temperature range of 200-3000C, with 100% conversion at 3000C for the 5-Pd/Al2O3 catalyst after 20 and 40 minutes of reaction time. However, the conversions were much lower for the 5-Pd 20-CeOx/Al2O3 catalyst in these conditions. The preparation, activity data, and the role of ceria support will be presented.

Preparation and activity of palladium catalysts on alumina and ceria-alumina mixed supports

Macromolecular Chemistry: The Second Century

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ACS Spring 2020 National Meeting & Expo

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