Patent GB-445342-A (GB)
Title: Structural activated carbon and process for the production thereof
IPC: C01B32/384
Filed: 1934-08-01
Abstract: Activated carbon having sufficient mechanical strength for use in granular form is prepared by compressing, heating and activating an intimate mixture consisting of (1) an inactive carbon of mineral origin; (2) a comminuted active carbon base of non-mineral origin, such as animal carbon or bone char, or a comminuted solid organic material yielding active carbon on carbonization; or carbon black from natural gas; and (3) a bituminous binder charring upon heating. The active and inactive carbons are ground to pass a sieve of 20 mesh or more, and preferably 80 mesh or more, per cm.  The mixture of carbons and binder is compressed before carbonization at pressures preferably from 140 to 1400 kgms. per sq. cm., but the range of pressure may extend from 30 to several hundred thousand kgms. per sq. cm.  The inactive carbon may be anthracite, semi-anthracite, bituminous and sub-bituminous coal, coke from mineral oil, from tar, from pitch, from asphalt, and from lignite.  Active carbon bases specified are wood-charcoal from maple, oak, hickory, birch, beech; chars from straw, hulls, wood-waste and shavings, corn stalks, husks, and cobs, sugar cane bagasse, nut hulls and shells, fruit pips, alcohol slops and from waste liquors from the paper industry; and animal chars from bone, blood and leather; similar comminuted vegetable and animal materials instead of the chars; and carbon obtained from peat, and from some types of lignite.  Bituminous binders specified are tar, pitches, from water-gas tar, oil-gas tar, or from the tars from wood, bone, coal, shale, lignite, peat, straw, vegetable matter and bitumen: pitches from animal, vegetable or petroleum oils; pitches from stearin, palm oil, bone fat, garbage and other wastes; pitches from native bitumens, asphalts and asphaltites. The pitch may be mixed with tar oils, petroleum oils, or cracked petroleum residues.  The binder may consist of the pitch present in the coke, e.g. coke from petroleum and tars, used as the inactive carbon ingredient, and oil or tar may be added to facilitate moulding.  If there is an excess of pitch in the coke, additional inactive carbon may be added; if there is insufficient pitch present, additional binder may be added.  Bituminous coals which cake readily and form hard coke serve as auxiliary binders.  The binder may be used in the form of an aqueous emulsion, or as a solution in volatile hydrocarbon, or the carbons may be mixed directly with a liquid binder.  When a non-fluid binder is used the materials may be heated or wetted with oil, or both wetted and heated, tar or emulsion; stirring mixing, and when they are mixed without wetting, the mixture is heated subsequently; and the carbons may be first wetted once then mixed with the non-fluid binder.  When an aqueous emulsion or a solution of binder is used, the water or solvent may be removed before briquetting.  The briquetts may be dried before carbonizing. The mixture may be moulded by extrusion in place of briquetting.  The moulded product is preferably comminuted to proper size before carbonizing; the carbonized product may be activated by treatment with steam or dilute acid, and it may then be treated with acid or hot water, or with both to remove ash, and finally washed with water and dried.  Calcium carbonate, calcium oxide, dolomite, finely divided metals, metal oxides, or salts may be added to the mixture of carbons and binder, and removed after activation by extraction with water or dilute acid.  Zinc chloride, or phosphoric acid or other dehydrating agents which will volatilize or react with the carbonaceous material may be added to the mixture of carbons and binder.  Carbonization may be effected by heating the material preferably in thin layers, for 30 to 90 minutes at 650--820 DEG  C., e.g. in a continuous rotary retort, and activation by heating in presence of steam for 30 minutes up to 2 hours, or longer in some cases, at 820--985 DEG  C.  Steam may be introduced during carbonization.  In one of the examples, a petroleum coke and a hardwood charcoal are mixed with an emulsion of coal-tar pitch, (m.p. 90--125 DEG  C.)  To prepare the emulsion the pitch is crushed, then ground in an alkaline solution of casein; and the suspension is mixed with an emulsion of creosote oil or anthracene oil in an alkaline solution of casein.  The mixture contains an emulsion of soft pitch and may be stabilized by adding ammonium tannate.