Efficient Transfer Hydrodehalogenation of Halophenols Catalyzed by Pd Supported on Ceria

Abstract

The transfer hydrodehalogenation (THD) of halophenols is efficiently catalyzed by palladium supported on high surface ceria (Pd/CeO2) under mild conditions (65 °C) using isopropanol (iPrOH) as hydrogen source. The reactivity of 4-halophenols (4-X-PhOH) varies in the order 4-F-PhOH > 4-Cl-PhOH > 4-Br-PhOH >> 4-I-PhOH and appears to be controlled by the desorption of halides from the catalyst surface. Kinetic analysis of the reactions and temperature programmed surface reaction (TPSR) experiments indicate that oxidative addition of C-X bonds and H-abstraction from isopropoxide compete for the same active sites on Pd. The catalyst was able to conduct the THD of various hazardous pollutants and emerging contaminants (DDT, pentachlorophenol, pentafluorophenol and triclosan).