GB412209A - Improved process for the preparation of activated or absorbent carbon or decolourising carbon - Google Patents

Abstract

In the preparation of active carbon, a naturally occurring carbonaceous material such as coal, cannel, lignite, peat or wood is first chlorinated, then briquetted by pressure alone, carbonized, and finally activated. Chlorination may be effected while the coal &c. is suspended in a non-reactive liquid, e.g. carbon tetrachloride or by passing the chlorine through the finely divided coal, or by letting the coal fall repeatedly through the chlorine: the temperature of chlorination should not normally exceed 100 DEG C., cooling being effected if necessary. The suspending liquid is recovered from the chlorinated product by distillation. Hydrogen chloride and chlorine and any residual suspending liquid are removed by reducing the pressure, by heating at atmospheric or reduced pressure, or by washing with water; inorganic matter is also removed by washing with water. In an example, air-dried bituminous coal is chlorinated while suspended in carbon tetrachloride and, after removal of the tetrachloride, is heated to 80 DEG C. under a pressure of 15 millimetres of mercury; the product is briquetted, carbonized at 900 DEG C., and activated. In a second example, gas coal is ground in a tube mill through which chlorine is passed, the temperature being kept at 60 DEG C. by water cooling. The product is pressed into tablets, carbonized at 850 DEG C., and activated at 800 DEG C. by steam, preceded or not by treatment at 90 DEG C. with nitrogen saturated with p moisture. According to the Provisional Specification the chlorine may be produced in the suspending liquid.