Catalyst – solid sorbent – or support therefor: product or process – Forming or treating a sphere – process only – Treating preformed sphere only
Reexamination Certificate
2000-03-15
2002-04-23
Hendrickson, Stuart L. (Department: 1754)
Catalyst, solid sorbent, or support therefor: product or process
Forming or treating a sphere, process only
Treating preformed sphere only
C502S432000
Reexamination Certificate
active
06376404
ABSTRACT:
The invention relates to a process for the production of evenly shaped high-performance adsorbents by steam activation in a rotary tunnel kiln operating in batch mode. The high-performance adsorbents produced are extremely versatile. They may, in particular, be employed for air separation, adsorptive cooling and as adsorbent components in textiles and synthetic fabrics.
It is known to use already pre-formed starting materials for the production of adsorbents. It is also known to produce shaped starting products from carbon-based materials and a binder using various processes, and subsequently to process them by carbonising and activation to form adsorbents.
WP 27 022 describes the production of adsorbent carbon by charring ion exchange resins.
WP 63 768 discloses a process for the production of shaped activated carbon for oil sorption from water, sulphonated styrene-divinylbenzene cation exchange resins being heat-treated at temperatures of from 250° C. to 1000° C. so as to form a carbon Process for the production of shaped high-performance adsorbents product having a carbon content of 80-90% which is subsequently activated using steam.
Both processes start from pre-formed starting materials. The adsorbents produced have too low an adsorption capacity. The pore structure needed for high-performance adsorbents cannot be formed owing to the nature of the process.
U.S. Pat. No. 4,040,990 describes partially pyrolized particles with a macroporous pore distribution of from 50 to 100,000 angstroms and high abrasion strength for use in adsorption, molecular separation and catalysis. The starting products are preformed, macroporous synthetic polymers which are partially pyrolized in an inert-gas flow. Because of the insufficiently formed pore structure distribution and the excessively low total pore volume, these partially pyrolized particles do not meet the quality criteria required of high-performance adsorbents. A controlled distribution, defined as a function of the intended purpose, of the micro-, meso- and macropores cannot be produced by using pyrolysis.
U.S. Pat. No. 4,957,897 discloses a process for the production of carbonised adsorbents from pre-formed, sulphonated, macroporous, aromatic polymers. By pyrolysis at from more than 300° C. to more than 1200° C., a multimodal pore size distribution with a micropore volume of at least 0.02 cm
3
/g is obtained in an inert-gas atmosphere. The pyrolysis process may also take place in the presence of an activating atmosphere consisting of steam or ammonia at temperatures of 800° C.-1000° C. Furthermore, a pretreatment of the carbonised adsorbents by means of sulphonating, chloromethylating, amines or hydrogen bromide is proposed. This process also is unsuitable for producing high-performance adsorbents with a BET surface area of at least 1400 m
2
/g and a defined pore structure. The pre-treatment with special organic and inorganic products increases the equipment expenditure, but not the quantitative and quantitative yields.
The subject of DE 19 60 02 37 and DE 19 62 50 69 is the production of granular activated carbon from a spherical styrene/divinylbenzene copolymer matrix. The styrene-divinyl copolymer matrix is carbonised at 750° C. or higher with from 5 to 50 per cent by weight sulphuric acid, 39-92 per cent by weight concentrated sulphuric acid and/or oleum, and then activated at a temperature of from 800 to 900° C. with the addition of steam, atmospheric oxygen or carbon dioxide in a rotary tunnel kiln or in a fluidised bed. The use of sulphuric acid and/or oleum during the carbonising leads to an increased environmental burden, associated with greater equipment expenditure. Together with the additional costs for sulphuric acid and/or oleum, the low total yield of 15% compromises the economic results. The quality targets stipulated for high-performance adsorbents are not met.
A process for the production of spherical activated carbon from carbon-based renewable raw materials, which are impregnated with lithium salts and mixed with rich coal, cellulose and a self-curing synthetic resin binder, then dried, cured, carbonised and activated, is disclosed by DE 44 16 576 and DE 19 53 83 73.
It is also known to produce microspheres from ground activated carbon which is dispersed in a water-insoluble synthetic resin and then compressed, powdered, granulated and dried, according to DE 35 10 209.
These processes involve the production of the spherical starting material. The spherical activated carbons produced do not have sufficient abrasion strength, hardness and adsorption performance. The particle size is not exactly defined and the geometrical sphere formation is not uniform. The equipment expenditure with this technology is high owing to the nature of the processes.
The object of the invention is to produce shaped high-performance adsorbents for use in air separation, adsorptive cooling and as adsorbent components in textiles and synthetic fabrics from carbon-based materials of various origin, without great equipment expenditure and using an economical process. The high-performance adsorbents are intended to have a high adsorption capacity, very good stability with respect to mechanical and hydraulic loading and, for rheological reasons, a uniform spherical shape. With a view to economically viable industrial application, they must be repeatedly regenerable.
The high-performance adsorbents are prepared from spherically pre-formed materials which contain at least 12% fixed carbon expressed in terms of solids content, such as polymer resins, acetylene coke and pearl cellulose by steam activation in an indirectly heated rotary tunnel kiln on a batch scale.
According to the invention, the spherically pre-formed materials are carefully pre-dried in a rotary tunnel dryer with 4-fold product turnover per kiln rotation and with a space/time ratio of from 1 to 2.5 m
3
/h using hot gas to a residual moisture content of at least 25%, then carbonised in an indirectly heated rotary tunnel kiln operating in batches with 6-fold product turnover per kiln rotation, with a space/time ratio of from 5 to 10 m
3
/h and with a reduced pressure on the flue-gas side of 1.5-3.0 mm water column in an inert-gas flow to a fixed carbon content of from 80 to 97%, and activated in batches in an indirectly heated rotary tunnel kiln with 8-fold product turnover per kiln rotation, with a space/time ratio of from 1 to 5 m
3
/h with a reduced pressure on the flue-gas side of 0.05-1.0 mm water column in an inert-gas flow with the addition of from 0.2 to 0.3 kg/h.kg of steam, with a constant product temperature profile over the entire heated kiln range of from 910° C. to 920° C.
During the drying in the kiln, the product temperature is increased in stages by from 8 to 10° C./min to a final temperature of from 200 to 300° C., and the final temperature is kept constant for from 30 to 60 minutes.
The carbonising is carried out in temperature intervals with a heating rate of from 6 to 9° C./min in the temperature range from 30 to 300° C., from 2 to 4° C./min in the temperature range from 300 to 500° C. and from 1 to 30° C./min in the temperature range from 500 to 800° C. final temperature.
During the activation, the required quantity of steam is delivered to the activation kiln in a controlled way through nozzles, with, calculated in terms of the heated kiln length from the product input, 15% of the quantity of steam being added in the 16 to 18% range, 20% of the quantity of steam in the 42 to 44% range, 30% of the quantity of steam in the 53 to 55.20% range, 20% of the quantity of steam in the 66 to 68% range, and 15% in the 82 to 84% kiln range.
The invention makes it possible to produce shaped high-performance adsorbents with very high adsorption capacity, characterised by iodine adsorption, of at least 1400 mg/g and very good resistance to mechanical and hydraulic loading from spherically pre-formed raw materials of various origin. Shaped high-performance adsorbents produced using the process according to the invention have a broad pore spectrum with uniform distribut
Giebelhausen Jann-Micheal
Spieker Hubertus
CarboTex, GmbH
Hendrickson Stuart L.
Keusey, Tutunjian & Bitetto
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