GB446889A - Non-structural activated carbon and process for the production thereof - Google Patents

Abstract

Active carbon for use in finely divided condition is obtained by mixing (1) an inactive carbon of mineral origin such as mineral coal or coke, (2) a finely divided active carbon of non-mineral origin, e.g. animal carbon, bone char, or comminuted solid organic material adapted to yield an active carbon upon carbonization, or carbon black obtained from natural gas, and (3) a bituminous binder charring upon heating, then carbonizing the mixture without first compressing it, and finally activating the product. Carbonization may be carried out by heating for 20--60 minutes at 480--985 DEG C., preferably 650--820 DEG C. in thin layers, preferably in a rotary drum furnace. Activation is then effected by further heating in the presence of steam, air, chlorine, flue gas or other activating gas for 1--5 hours at 650--985 DEG C. The product may be treated with water and/or dilute acid to remove ash. The mixture of inactive and active carbons may be mixed with (a) the emulsified binder, or the carbon may be suspended in an aqueous medium and then mixed with the emulsified binder. Water may be separated if desired; (b) a solution of the binder in a solvent such as benzol, naptha, petroleum hydrocarbons or coal tar fractions which are then separated by distillation; (c) a liquid bituminous binder such as tar or an oil-pitch mixture; (d) a solid pitch or other solid bituminous binder and then with a liquid such as oil or tar which will dissolve or flux with the binder. Preferably the oil is added in the form of an emulsion; (e) a pitchy binder rendered fluid by heating. Substances such as calcium or magnesium carbonates or oxides, finely divided metals, oxides or salts may be added to the carbonaceous mixture, these substances being removed from the activated carbon by treatment with water or dilute acid. Materials which volatilize or react with the carbonaceous material during treatment, e.g. zinc chloride or phosphoric acid, may also be added. The inactive carbon may comprise cokes and coals; and the active carbon may include wood charcoal, e.g. from maple, oak, hickory, birch, &c., vegetable carbons, e.g. from straw, hulls or peat, and carbon black obtained by the incomplete combustion of natural gas, or it may be formed during the carbonization step by using finely divided organic substances of non-mineral origin such as straw, hulls or wood. Suitable bituminous binders include tar pitches from wood, bones, coal, oil shales, lignite, peat, straw, hulls, bitumens, water gas and oil gas; oil pitches from the distillation and cracking of animal, vegetable and petroleum oils; pitches from the destructive distillation of stearin, palm oil, bone fat, fat waste, natural bitumens, asphalts, asphaltites, coal, peat and lignite. Oils and tars may also be used in conjunction with the above pitches. A preferred binder is the pitch obtained as a residue from the distillation of "soluble tar" which is itself the residue from the distillation of the aqueous or tarry pyroligneous acid layer formed in the destructive distillation of hard wood. Soluble wood tar or the pitch therefrom may be blended with settled wood tar or coal tar or the corresponding pitches. According to an example, a mixture of finely divided hardwood charcoal and petroleum coke is formed into a paste with water containing a protective colloid. It is then mixed with an emulsion of soft pitch prepared by suspending finely divided hard coal tar or wood tar pitch in water containing casein dissolved in alkali to which is added an emulsion of a tar distillate, e.g. anthracene or creosote oils, obtained by agitating the oil with an equal volume of an emulsifying agent consisting of water containing a protective colloid, e.g. alkali casein. Preferably only sufficient water is present to permit thorough mixing, excess being removed by filtering. The mass may also be dried at 88--122 DEG C. and the residue carbonized. Suitable mixtures include hardwood char, petroleum coke and wood tar or coal tar pitch; or petroleum coke, carbon black and wood tar pitch. The mixtures of inactive and active carbons may vary from 10 per cent or less of char to 90 per cent or more of coke and vice-versa, and the ratio of carbon to binder may vary from 1 : 1 to 4 : 1, preferably 2 : 1.