SEQUENTIAL CARBONIZATION AND ACTIVATION OF FIBROUS MATERIAL IN A CARBON DIOXIDE ATMOSPHERE

摘要

1310011 Active fibrous carbon DEFENCE SECRETARY OF STATE FOR 8 April 1970 [8 Jan 1969] 1150/69 Heading C1A Active fibrous carbon, i.e. filaments, yarns or fabrics of carbon are formed by passing a fibrous organic material 6, upward relative to a source of heat, e.g. electric elements 3, so as to heat the material through a carbonizing temperature range of up to 600‹ C., the material being spaced from the heating source so as to permit an upward convective gas flow between the fibres and the heat source so as to remove volatile decomposition products from the carbonized material, and then contacting the carbonized material at a temp. between 600‹ and 1000‹ C. with CO 2 or steam to activate it. The organic material may be a polymer fibre containing at least C, H and O, e.g. it may be, oxidized polyacrylonitrile, polyvinyl alcohol or carbohydrate polymersuch as viscose rayon, cuprammonium rayon, or cellulose ester rayon. The convective gas flow over the organic material may be increased by admitting additional gas to the furnace, e.g. through inlet 12 to give a total gas flow relative to the surface of the material between 50 and 25 cm./minute. This gas may be the activating gas, i.e. CO 2 or steam, and the heating elements 3 may be arranged so that the organic material is carbonized, raised to activating temp. and activated all in a single furnace, the speed of the material through the furnace being such that it has a residence time at its critical decomposition temp. of at least 15 mins. The speed of the feed rolls 6, 9 and take-up rolls, 10, 8 may be adjusted to submit the material to tension during carbonization and/or activation. Between 0À1 and 10% of a Lewis acid selected from the dihalides of Ba, Ca, Mg and Zn, and the trihalides of Fe, Cr and A1 may be incorporated into the organic starting material.