Plasma Synthesis: A Novel Way of Making Catalysts
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Plasma Synthesis: A Novel Way Of Making Catalysts Biberger, M.,Leamon, D., Qi, X., Sawayda, R., and Yin, Q. SDCmaterials, Inc., 940 S. Park Lane, Suite #2, Tempe, AZ 85281, USA
ABSTRACT In the present paper a novel method of manufacturing mobile emission control catalysts (MECC) is presented. The manufacturing of these novel catalysts consists of three steps: In a first processing step micron sized powders consisting of an oxide powder, typically Al2O3 or SiO2 or the like, and micron sized precious metal powders, Pt, Pd, Rh or the like, are co-fed into a DC plasma gun. Inside the gun the powders are vaporized at temperatures of approximately 25,000 K. After the powders are vaporized the vapor is rapidly quenched at rates of approximately 1,000,000 K/s. This process step yields so-called Nano on Nano Catalysts™, where nano clusters of precious metals atoms are condensed onto the nano sized oxide particles. In a second processing step these Nano on Nano Catalysts™ are dispersed in water. This step is followed by a third, and final processing step, where the Nano on Nano Catalysts™ are integrated onto the final support, i.e. the monoliths (or honeycombs), which ultimately are canned and located downstream of a vehicle’s engine. Catalysts manufactured under the above conditions are then tested against reference catalysts, both under fresh and aged conditions. Test results show that the plasma based catalysts have better light off temperaturesafter aging than the reference catalysts if they contain the same amount of precious metals as the reference catalyst. If the precious metal amount for the plasma based catalysts is reduced to approx. half the amount of the reference catalysts then both catalysts show approx. the same light off temperatures after aging. Above results show that with catalysts based on plasma technology one can either lower the light off temperatures while maintaining the precious metal content compared to reference catalysts, or match the performance of the reference catalysts while reducing the precious metal content to approx. 50%, compared to the reference catalysts.
INTRODUCTION Traditionally catalysts are manufactured using wet chemistry technology. I.e. elemental precious metals such as Platinum, Palladium, Rhodium, also called Platinum Group Metals (PGM’s) are first dissolved in acids to form salts. These salts are subsequently combined with water. These salt solutions are then mixed into so-called washcoat slurries. The basic ingredients of awashcoat slurry are water and micron sized powder mixes. The micron sized powder mixes are comprised of porous Aluminumoxide, Rare Earth Oxides, Zeolites and Boehmite. After combining the washcoat slurries and the PGM salt solutions they get coated onto the final substrates, also called monoliths. After the coating step the monoliths are then dried and calcined and the catalystsare ready to be canned and then installed into the vehicles. Above manufacturing methodology is a traditional (over 40 years of history), reliable and proven technol
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