Low-Temperature Methanol Synthesis Catalyzed over Ultrafine Palladium Particles Supported on Cerium Oxide

Ceria-supported palladium prepared by the coprecipitation method efficiently catalyzes the methanol synthesis from carbon monoxide and hydrogen at a reaction temperature as low as 170°C. The methanol yield produced with the catalyst pre-reduced at 300°C is significantly higher than with that reduced at 500°C. The catalysts contain ultrafine palladium particles that are cationic even after reduction at 500°C while a part of palladium atoms are suggested to interact directly with ceria via Pd–O–Ce bonding. The valence of the major cationic species is probably close to +1. The lower activity of the catalyst reduced at 500°C is caused from the lower surface area of palladium and less activity of the larger particles whose crystallite size is estimated to be 4 nm.