Carbon-Supported Palladium–Cobalt Catalysts in Chlorobenzene Hydrodechlorination

Abstract

Bimetallic and monometallic composite materials containing ultra-microporous carbon, the structure of which is similar to that of activated carbon, Pd0, CoO, and possibly PdCoO2 nanoparticles are synthesized via the pyrolysis of sawdust impregnated with a solution of palladium nitrate and cobalt nitrate. According to TEM, the size distribution of metal-containing particles in the bimetallic catalysts is slightly broader than the one in monometallic catalysts, and the average particle size of the former is larger than that of the latter. Some metal-containing particles are localized on the support surface, while others are pressed into the support matrix or coated with a carbon shell. Bimetallic catalysts exhibit high stability and activity in gas-phase chlorobenzene hydrodechlorination (HDC) to form mostly benzene; in the presence of all cobalt-containing catalysts, chlorobenzene conversion is greater than 85% throughout the investigated range of temperatures (150–300°C). XPS shows that during HDC, the metals are chlorinated and the carbon shells of the metal particles are partially degraded under the action of hydrogen chloride. This is accompanied by the emergence of active metal particles on the catalyst's surface. Introducing cobalt helps reduce the deactivation of the catalysts' palladium-containing sites and ensures the formation of additional active sites based on CoO.