High-porosity carbons prepared from bituminous coal with potassium hydroxide activation

Porous carbons with a very high porosity were prepared from an Australian bituminous coal with KOH activation. The preparation process consisted of KOH impregnation followed by carbonization in nitrogen at 500-1000 degrees C for 0-3 h. Surface area and pore volume of the resulting carbons were found to increase with the carbonization temperature to a maximum at 800 degrees C and then begin to decrease. It has been suggested that carbon gasification by the released CO2 and the oxygen in potassium containing compounds plays an important role in determining the pore structures. The porosity development was affected by the chemical ratio of KOH to coal. The optimum chemical ratio for preparing a high-porosity carbon varies with carbonization conditions. A process;consisting of impregnation at a chemical ratio of 4.25 followed by carbonization at 800 degrees C for 1 h was recommended for producing a high surface area (>3000 m(2)/g) carbon.