Low-Temperature Reactions of HCl with Metal-Doped Carbon

A model carbon prepared from phenolic resin was activated with O2 and then impregnated with Ca, Cu, or Zn to examine the relationship between the amount of HCl desorbed from carbon samples containing various metals in this lower temperature range (100 and 300 °C) and clarified the effect of active sites on HCl adsorption. The results showed that interactions between HCl and carbon were enhanced at temperatures in the range of 100–300 °C and that the amount of HCl reacted was increased by doping with these metals. The different HCl concentration profiles at 100 and 300 °C were obtained with a greater overall decrease in HCl at the lower temperature (100 °C). Those are attributed to increased physical adsorption of HCl at 100 °C. The mass of HCl reacted increased in the order of Cu < Ca < Zn at 300 °C and Ca < Cu < Zn at 100 °C, and HCl reacted at 300 °C was evidently more stable than that reacted at 100 °C. Organochlorine compounds, chemisorbed HCl, and inorganic chlorides were all identified on the carbon surfaces following exposure to a flow of HCl. The organochlorine species and chemisorbed HCl were desorbed, along with the generation of H2O, upon heating the samples to 700 °C, while inorganic chlorides and additional H2O were desorbed above this temperature. Both the mass of organochlorines generated and the amount of HCl absorbed were found to increase with the number of active sites at 300 °C; however, that was exceeded remarkably at 100 °C.