CS224299B1 - Method of manufacture of molecular screen - Google Patents

Description

The invention relates to a process for the production of molecular sieves for the separation of gas from its mixture, in particular the separation of oxygen from the air, by heat treatment of charcoal or xylite containing volatile combustible materials, crushed or roller-shaped, balls.

Zeolite molecular sieves are used for gas separation on this principle. These zeolitic molecular sieves are not chemically inert, their preparation is very complicated and expensive. In case of separation of oxygen-nitrogen (air) mixture, the separated mixture should be completely dried. The desorption then takes place preferentially in nitrogen, which means that, when the air is composed of 21% oxygen and 79% nitrogen, it is necessary to process four times the volume of the mixture than is required for molecular sieves which preferentially adsorb oxygen over nitrogen. .

Carbon molecular sieves made by pyrolysis of plastic materials such as polyvinylidene chloride, polyvinylbenzene and the like are known. They exhibit zero or very weak selectivity in adsorption of gases of approximately the same kinetic molecular dimensions such as oxygen and nitrogen, argon and oxygen or helium and methane. They are difficult to prepare in larger quantities.

Further, hydrocarbon treated sieves treated with hydrocarbon on coke containing up to 5% volatiles at a temperature of from 600 to 900 ° C are known. The carbon released from the hydrocarbon is deposited in the coke and reduces the existing pores. Their main disadvantage is their low lifetime, which results from the fact that the amortized carbon released, reducing the coke pore dimensions, is not stable. The use of hydrocarbon in the main stage of the process increases the cost of adsorbent preparation.

Molecular sieves prepared from carbon powder or other carbonaceous material found in nature by activating the granular material at a temperature of 300 to 400 ° C are then known, and then calcined at a temperature of from 850 to 960 ° C. This gives granular, highly activated carbon. This activated carbon with the so-called controllable eelectivity is intended for separation of hydrocarbon mixtures. The material is characterized by an average pore size of about 0.5 nm and is therefore not suitable for separating the oxygen-nitrogen mixture.

The aforementioned disadvantages are overcome by the process for the production of the carbon molecular sieves according to the invention, characterized in that crushed charcoal or hemixylite with a content of 10 to 60 wt. the volatile combustible materials are heated at a temperature ranging from 1 to 100 ° C per minute with a residence time of 1 to 10 hours to a final temperature of 600 ° C to 1 100 ° C in a non-oxidizing gas atmosphere, after which the product is cooled to 10 to Deň: 32 ° C.

The advantage lies in the fact that the process according to the invention is simpler, the end product ee obtains already at the stage where in other cases only the raw material is ready for a longer process. Relatively high content of volatile combustible material in the starting material guarantees developed microporosity and at the same time high desorption capacity of the ait. The product obtained according to the invention is stable and has a long service life.

The production process consists firstly of crushing the raw material, i.e. charcoal or heaixylity, and sorting the grain in the range of 0.1 to 5 mm. If a shaped screen is to be prepared, the grain is screened below 100 µm, mixed in a suitable ratio and wood tar and formed by, for example, pressing on a hydraulic press or granulator. The sorted fraction or shaped particles are heated in either a fixed or movable bed in an atmosphere of a non-oxidizing gas, such as argon, helium, nitrogen, and the like.

Heating is carried out from a controlled temperature rise in the range of 1 to 100 ° C / min to a final temperature of 600 to 1100 ° C. The decisive stage for product quality is endurance at the final temperature, which ranges from 1 to 10 hours.

In order to improve the course of the carbonization process and favorably influence the properties of the product, it is advisable to carry out a chemical treatment with oxygen or air before the carbonization. This treatment is carried out in a fixed or fluidized bed below the ignition temperature of the treated material for 1 to 50 hours at a gas flow rate of 0.5 to 4 l / g of sample. Low temperature oxidation below the ignition temperature results in uniform oxidation throughout the particle of the material being treated, reduces caking in heat treatment at higher temperatures, and in particular develops microporosity, which means that the proportion of micropores is increased.

To remove undesired oxidation, the final product is cooled to room temperature in a non-oxidizing gas atmosphere.

The porous structure of charcoal and hemixylites is modified as described above. This modification has the effect of limiting the product pore size range, since the pore inlet openings have been narrowed to a diameter of about 0.3 nm. This pore diameter is close to the kinetic diameter of the oxygen molecules, which is a necessary condition for its separation from the air or for the separation of gases with different molecular sizes.

He did

Charge the charcoal from pine wood with a grain size of 2 to 3 mm to heat the fixed bed at a heating rate of 5 ° C / min to a final temperature of 800 ° C in an argon atmosphere with a final temperature of 6 hours. The product is then cooled to room temperature in an argon stream. When subjected to the product, after a one-stage adsorption from air, a gas of 4 ml / g adsorbent containing 26 to 30% Oj is obtained.

Example 2

The weighed hemixylite (Kristina fracture, Hrádek η. N) in a grain size of 2 to 3 mm is subjected to a chemical treatment by air in a fluidized bed at 240 ° C and a flow rate of 30 l air / h.100 g for 4 hours. Heating at 80 ° C / min to a final temperature of 850 ° C is followed by degassing the sample under a nitrogen atmosphere. After cooling, the product nitrogen stream at room temperature, the product is subjected to the test separation of oxygen from air to result in 5 ml gas / g of sample containing 30% 0 _second

The carbon molecular sieve prepared according to the invention can be used for the separation of various gas mixtures, in particular for the selective separation of oxygen from air. In practice, when applied in a pressure swing adsorption method based on rapid alternation of adsorption and desorption cycles, oxygen-enriched gas (35 vol% single-stage, 60-80 vol% multi-stage) can be obtained from the air that can serve it will replace expensive oxygen from fractional distillation as a source for the production of pure oxygen or, more importantly, in various technological processes (steel production, non-ferrous metal production, chemical production, biochemistry, waste water and sewage treatment, coal gasification, combustion processes, etc.) liquefied air. These examples are not limiting in terms of adsorbent quality (capacity and selectivity), but merely illustrate the subject matter of the invention.

Claims (2)

Process for the production of molecular sieves for the separation of gas from its mixture, in particular the separation of oxygen from air, by heat treatment of charcoal or xylite containing volatile combustibles, crushed or shaped into rollers, balls or the like, characterized in and the like, shaped charcoal or hemixylite with a content of 10 to 60 wt. The volatile combustible materials are heated at temperatures ranging from 1 to 100 ° C per minute with a residence time of 1 to 10 hours at a final temperature of 600 to 1100 ° C in a non-oxidizing gas atmosphere, after which the product is cooled to 10 to 40 ° C in the same atmosphere. . 2. A process for the production of molecular sieves according to claim 1, characterized in that the granulated, optionally into rolls, balls or the like, shaped charcoal or hemixylite is treated for 1 to 50 hours chemically with air or oxygen at a temperature of from 80 to 450. Deň: 32 ° C.