Selectively catalytic oxidation of 1,2-propanediol to lactic, formic, and acetic acids over Ag nanoparticles under mild reaction conditions

Abstract

Selectively catalytic oxidation of 1,2-propanediol with O2 to lactic, formic, acetic acids over Ag nanoparticles was investigated. Ag nanoparticles and alkali cocatalyzed the oxidation of 1,2-propanediol. The Ag nanoparticles with the average particle sizes of 15.2–43.2nm were prepared by using citric acid (CA), sodium dodecylbenzenesulfonate, tween-80 (Tween), D-sorbitol, and polyvinylpyrrolidone as organic modifiers. When the oxidation of 1,2-propanediol was catalyzed by AgTween nanoparticles at 120°C for 4h in NaOH solution, the lactic acid selectivity was 62% at the 1,2-propanediol conversion of 65.6% while over AgCA nanoparticles, the acetic and formic acids selectivities were 63.2% and 30.5%, respectively, at the complete conversion of 1,2-propanediol. The small-sized Ag nanoparticles favored the formation of acetic and formic acids while the Ag nanoparticles with the average particle sizes of 19.4–25.3nm favored the formation of lactic acid. The Ag nanoparticle sizes also affected the kinetics for the catalytic oxidation of 1,2-propanediol.