Catalyst – solid sorbent – or support therefor: product or process – Solid sorbent – Free carbon containing
Patent
1990-07-19
1993-04-13
Konopka, Paul E.
Catalyst, solid sorbent, or support therefor: product or process
Solid sorbent
Free carbon containing
264 292, 4234475, 502180, 502423, 502426, 502427, C01B 3112, D01F 912
Patent
active
052023028
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The invention relates to the manufacture of fibrous or film-type activated carbons which can be used as supports for catalysts or for the adsorption of materials from a gaseous and/or liquid phase in applications such as, for example, industrial filtration, decolouration of solutions, air filtration, respirators, air-conditioning, filter hoods, adsorption from solution, medical, bacterial or viral adsorption or filtration and microtoxin adsorption.
Processes for producing fibrous or film-type activated carbons have been known for some years. Such processes chiefly comprise carbonising fibrous organic starting materials by heating in an inert atmosphere to drive off volatile matter and then `activating` the material to form the desired porous active surface in the carbonised fibrous material (char) by further heating to a temperature higher than the carbonising temperature.
It has been found in such processes that pre-treatment with various chemicals prior to the carbonisation step greatly enhances the quality of the activated carbon product. For example in GB Patent No. 1301101 a method of making activated fibrous carbon is disclosed in which the fibrous starting material is treated with one or more alkali metal halides, collectively known as `Lewis acids`. A disadvantage of this pre-treatment is that it is only capable of generating a microporous (pore diameter 2 nm) material and for some applications, in particular when the activated fibrous carbon is used as a catalyst support, a mesoporous (pore diameter 2 to 50 nm) material is preferred.
An improved activated carbon fibre material having high adsorbancy and superior physical strength is also disclosed in GB Patent No. 1455531 in which during manufacture a cellulose fibre is impregnated with a phosphorus compound prior to carbonisation. More recently, in GB-A-2164327, a process has been described for making an activated carbon fibrous material having a substantial percentage of mesopores in which pretreatment comprises impregnation with one or more compounds of boron and at least one alkali metal.
DISCLOSURE OF THE INVENTION
An impregnation treatment has now been found which, depending on the activation conditions, can result in a microporous or mesoporous carbon, without the incorporation of Lewis acids, and which allows pore size distribution to be controlled.
In accordance with the invention a process for preparing fibrous or film type activated carbon comprises the steps of carbonising a celluloses material and activating the resulting carbon between 200.degree. C. and 1100.degree. C. in an inert atmosphere wherein prior to activation the celluloric material or carbon is impregnated with at least one boron-containing compound and at least one phosphorus-containing compound.
Preferably at least one boron-containing compound and at least one phosphorus-containing compound are combined in an impregnation preparation. The boron-containing compound may be an acid or a salt. Particularly suitable boron-containing compounds are boric acid, boric oxide, borax, sodium metaborate, sodium tetraborate, lithium metaborate, lithium pentaborate, lithium tetraborate, potassium tetraborate or potassium metaborate. Particularly suitable phosphorus containing compounds are acids such as phosphoric acid, metaphosphoric acid, pyrophosphoric acid, phosphorus acid, phosphonic acid, phosphonous acid, phosphinic acid and phosphinous acid, or their salts, or phosphonium salts, phosphines and phosphine oxides. The impregnation preparation may contain a mixture of several of the aforementioned boron compounds combined with a mixture of several of the aforementioned phosphorus compounds.
The boron and phosphorus compounds which form the impregnating preparation may be impregnated onto or into the carbon by contacting the carbon with the impregnating preparation when the preparation is dissolved in a solvent and then drying the carbon leaving the boron and phosphorus compounds incorporated therein or as an external coating on the surface. The impregnation pr
REFERENCES:
patent: 3969268 (1976-07-01), Fukuda et al.
patent: 4197279 (1980-04-01), Saito et al.
patent: 4412937 (1983-11-01), Ikegami et al.
patent: 4699896 (1987-10-01), Sing et al.
De La Pena John M. D.
Roberts Richard A.
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