Coking- and Sintering-Resistant Palladium Catalysts Achieved Through Atomic Layer Deposition

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Science  09 Mar 2012:
Vol. 335, Issue 6073, pp. 1205-1208
DOI: 10.1126/science.1212906

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A Useful Cover-Up

Many industrial catalysts that consist of metal nanoparticles adsorbed on metal oxide supports undergo deactivation after prolonged use. Organic reactants can decompose and cover the metal with carbon (“coking”), and other processes can push the size distribution to fewer but larger particles that have less overall surface area available for reaction (“sintering”). Lu et al. (p. 1205) used atomic-layer deposition to apply a uniform overlayer of alumina onto supported palladium nanoparticles. This coating greatly increased the resistance of the nanoparticles to coking and sintering during the oxidative dehydration of ethane to ethylene.


We showed that alumina (Al2O3) overcoating of supported metal nanoparticles (NPs) effectively reduced deactivation by coking and sintering in high-temperature applications of heterogeneous catalysts. We overcoated palladium NPs with 45 layers of alumina through an atomic layer deposition (ALD) process that alternated exposures of the catalysts to trimethylaluminum and water at 200°C. When these catalysts were used for 1 hour in oxidative dehydrogenation of ethane to ethylene at 650°C, they were found by thermogravimetric analysis to contain less than 6% of the coke formed on the uncoated catalysts. Scanning transmission electron microscopy showed no visible morphology changes after reaction at 675°C for 28 hours. The yield of ethylene was improved on all ALD Al2O3 overcoated Pd catalysts.

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