Formation of surface chlorine species by low temperature reaction of HCl with metal-doped carbon

Abstract

Abstract A model carbon prepared from phenolic resin was O2-activated and then impregnated with Ca, Cu or Zn to clarify chlorine behavior in coal utilization. Ease of interaction between HCl and the carbon material was enhanced at 100–300\u202f°C. The concentration at which HCl reacted with Ca, Cu and Zn was high. The surface chloric species that were generated by reaction of the carbon substrate with HCl were studied using X-ray photoelectron spectroscopy (XPS) and temperature programmed desorption (TPD). XPS measurements suggested the presence of inorganic chloride and organic chlorine species after reaction with HCl. When the carbon samples were washed after the HCl reaction, most of the HCl was eluted. Chemically adsorbed HCl species were also detected by TPD measurement; the presence of inorganic chloride, organic chlorine and chemically adsorbed HCl species were indicated. No correlation was determined between the amount of organic chlorine species generated and the number of activated carbon sites at 100\u202f°C. However, the amount of organic chlorine at 300\u202f°C indicated a tendency to increase with the number of carbon sites, and the surface functional oxygen groups acted as sites for the generation of C-Cl bonds. As a result, possible scheme for the generation of organic chlorine species at low temperature by reaction between HCl and the metal-doped (Ca, Cu or Zn) carbon is discussed.