Chemistry of inorganic compounds – Modifying or removing component of normally gaseous mixture – Carbon dioxide or hydrogen sulfide component
Patent
1992-07-09
1995-02-14
Konopka, Paul E.
Chemistry of inorganic compounds
Modifying or removing component of normally gaseous mixture
Carbon dioxide or hydrogen sulfide component
95139, 423236, 4234471, 502416, 502437, C01B 3120, C01B 3108, C01C 304, B01D 5302
Patent
active
053893506
DESCRIPTION:
BRIEF SUMMARY
This invention relates to a process for the preparation of activated carbons by pyrolysis of polyarylamides, to adsorbent activated carbon materials produced by the said process and to uses for these materials.
Adsorbent activated carbons are widely used for the absorption of materials, in particular gases, for example in industrial filtration, air purification, and respirators. Such carbon materials are also used in decolourisation, for example to remove coloured impurities from solutions, and as supports for catalysts. Often such materials are quite effective at removing large organic molecules from the air but are less effective at removing smaller molecules such as carbon dioxide.
These carbon materials are generally prepared by carbonization (pyrolysis) of an organic precursor in an inert atmosphere at an elevated temperature, followed by activation in an activating atmosphere, also at an elevated temperature. Often it is also necessary to treat the precursor or the carbonized product with various chemicals, such as metal compounds, to ensure or to improve the activated product.
Fibrous activated carbons are currently manufactured from a number of precursors including fibrous carbohydrates, viscous rayon, polyacrylonitrile (`PAN`), phenolic resins and coal tar pitch. These materials provide a group of increasingly important adsorbents in both liquid and vapour phase applications. Those derived from rayon are particularly versatile in terms of the range of pore sizes which can be formed during activation, after appropriate pretreatment with aqueous impregnants. Such materials are for example described in GB 1301101 and GB 2164327.
Viscous rayon is a form of regenerated cellulose having quite low crystallinity. Some investigations have been carried out into the possibility of using more ordered fibrous precursors for preparation of activated carbon materials. Among more recently developed high-performance polymers polybenzimidazole (see U.S. Pat. No. 4,460,708) is claimed to be a promising precursor for activated carbon production but requires a pre-oxidation stage to stabilise the polymer and also requires chemical pre-treatment to form a salt prior to carbonization. PAN also requires a pre-oxidation stage.
It was suggested in GB 1515874 that aromatic polyamides might be suitable for formation of active carbon materials. This document teaches the impregnation of fibres with flame retardant agent, carbonization at up to 400.degree. C. in an oxygen containing atmosphere followed by activation with 10 to 70% by volume of steam with carbon dioxide and carbon monoxide at above 500.degree. C. No data for such polyamides is given, only cellulose and polyacrylonitrile fibres being exemplified. Tomizuka et al, Tanso 106 (1981), 93, reported investigating production of carbon fibres from Kevlar but hitherto no attempt has been made to develop a pore structure in chars derived from this polymer by gaseous activation.
`Kevlar` is a condensation product of 1,4-diaminobenzene and terephthalic acid, the resulting polymer being a polyarylamide having the repeat unit; ##STR1##
Kevlar fibres are highly crystalline and according to Dobb et al. J Polym. Symp. 58 (1977) 237 and J Polym. Sci. Polym. Phys. Ed. 15 (1977) 2201, consist of a system of sheets regularly pleated along their long axes and arranged radially. The relatively small amount of disorder in the structure is due to chain termination or defects in the packing of these sheets. A similar fibre is sold by the trademark `Twaron` by Akzo NV.
Further known aromatic polyaramide fibres are sold under the trademark `Nomex` and result from polymerising 1,3-diaminobenzene with isophthalic acid to provide a copolymer with the repeat unit ##STR2## these also never having being reported as being carbonized and gaseously activated. The materials are available in various forms, including, e.g. Kevlar pulp (used as an asbestos replacement) and all such forms are considered to have potential for use with the present invention.
It is an object of the present invention to provi
REFERENCES:
patent: 4046525 (1977-09-01), Matsuo et al.
patent: 4073869 (1978-02-01), Kalnin
patent: 4118341 (1978-10-01), Ishibashi et al.
patent: 4401588 (1983-08-01), Turner
Freeman John J.
Gimblett Frederick G. R.
Hayes Robert A.
Sing Kenneth S. W.
Konopka Paul E.
The Secretary of State for Defence in Her Britannic Majesty's Go
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