The origin of the extraordinary stability of mercury catalysts on the carbon support: the synergy effects between oxygen groups and defects revealed from a combined experimental and DFT study

Abstract

Thermal stability of HgCl2 has a pivotal importance for the hydrochlorination reaction as the loss of mercuric compounds is toxic and detrimental to environment. Here we report a low-mercury catalyst which has durability over 10000 h for acetylene hydrochlorination under the industrial condition. The stability of the catalyst is carefully analyzed from a combined experimental and density functional theory study. The analysis shows that the extraordinary stability of mercury catalyst is resulted from the synergy effects between surface oxygen groups and defective edge sites. The binding energy of HgCl2 is increased to be higher than 130 kJ/mol when adsorption is at the edge site with a nearby oxygen group. Therefore, the present study revealed that the thermal stability problem of mercury-based catalyst can be solved by simply adjusting the surface chemistry of activated carbon. Furthermore, the reported catalyst has already been successfully applied in the commercialized production of vinyl chloride.