Activated carbon production from lignite in supercritical water

Conversion of Xiaolongtan lignite to activated carbon was conducted in a semi-continuous supercritical water(SCW)reactor.The effects of temperature(600-700℃),pressure(0.1-30MPa)and KOH loading(mass fraction 0%-15%)were investigated.The coal conversion,iodine number and BET surface area of the activated carbon increase with temperature,and the meso-pore formation is also enhanced at relatively higher temperatures.Compared with steam activation at ambient pressure at the same temperature,SCW activation yields activated carbon with an excellent adsorption and develops mesopores.When the activation pressure increase from 0.1MPa to 25MPa at 650℃,the BET surface area and meso-pore ratio increase by 74% and 38%,respectively.The activated carbon has a BET surface area of 825m2/g with the addition of mass fraction 10% KOH in lignite as catalyst.Moreover,the ash content of the activated carbon is lower than mass fraction 2% after washing with dilute HCl.