Carbon-containing molecular sieves

• US 3,960,522 A
• Filed: 02/21/1974
• Issued: 06/01/1976
• Est. Priority Date: 04/23/1971
• Status: Expired due to Term

• Current Assignee: Bergwerksverband GmbH
• Original Assignee: Bergwerksverband GmbH
• Inventors: Peters, Werner, Knoblauch, Karl, Heimbach, Heinrich, Juntgen, Harald, Korbacher, Werner, Zundorf, Dieter, Munzner, Heinrich
• Primary Examiner(s): Granger, Theodore A.
• Application Number:
  US05/444,383
• Time in Patent Office: 831 Days
• Field of Search: 55/33, 55/58, 55/62, 55/68, 55/75, 55/387, 55/389, 210/63, 210/68, 210/71, 252/421, 252/444, 252/445
• US Class Current: 95/138
• CPC Class Codes: C01B 2210/0045 Oxygen
• CPC Class Codes: C01B 32/306 with molecular sieve properties
• CPC Class Codes: Y10S 95/903 Carbon

Abstract

Process for preparing carbon-containing molecular sieves adapted for separating small molecular gases, in particular oxygen, from nitrogen, which comprises treating coke having a content of volatile components of up to 5% at 600° - 900° C with a hydrocarbon which splits off carbon whereby the split-off carbon is deposited in the carbon framework of the coke thereby narrowing the existing pores.

Claims

1. A method of separating oxygen from gas mixtures containing oxygen and nitrogen, comprising passing a gas mixture which contains oxygen and nitrogen through a carbon containing molecular sieve prepared by heating in a closed oven in the absence of air at a coking temperature of at least 600°

C, particles of a cokable substance having a size between 0.1 and 20 millimeters until the content of volatile components in the resulting coke is not more than 5% by weight and thereafter subjecting the resulting coke to heating in an inert atmosphere at a temperature between 600° and

900°

C while a gaseous stream of a carbonaceous substance which splits off carbon at said temperature is passed into contact with the said coke for such a period between 1 and 60 minutes that the carbon that is thus split off is deposited in the pores of the coke and reduces the effective average size of the pores to less than about 0.3 millimicron, whereby the oxygen in said gas mixture is more rapidly adsorbed by said molecular sieve than the nitrogen in said gas mixture.

2. A method as defined in claim 1, wherein said gaseous mixture is passed through said molecular sieve at pressures between substantially 1 and 40 atmospheres.

3. A method as defined in claim 1, wherein said gaseous mixture is passed through said molecular sieve for a period between substantially 0.5 and 5 minutes.

4. A method as defined in claim 1, wherein said gaseous mixture is passed through said molecular sieve for a period between substantially 10 and 60 seconds.

5. A method as defined in claim 1, said molecular sieve having a predetermined volume;

and wherein a volume of said gaseous mixture which equals substantially 2 to 20 times said predetermined volume is passed through said molecular sieve.

6. A method as defined in claim 1;

and further comprising the step of desorbing the adsorbed gas from said molecular sieve.

7. A method as defined in claim 6, wherein the proportion of said first gas in the desorbed gas is greater than the proportion of said first gas in said gaseous mixture.

8. A method as defined in claim 6, wherein said desorption is effected by subjecting said molecular sieve to pressures lower than atmospheric pressure.

9. A method as defined in claim 8, wherein said desorption is carried out at pressures in excess of substantially 20 torr.

10. A method as defined in claim 6, wherein said desorption is carried out for a period between substantially 0.5 and 5 minutes.

11. A method as defined in claim 6, wherein said gaseous mixture is passed through said molecular sieve at pressures in excess of a predetermined pressure;

and further comprising the step of abruptly reducing the pressure to said predetermined pressure prior to said desorption.

12. A method as defined in claim 6, said molecular sieve comprising at least two discrete portions;

and wherein the steps of passing said gaseous mixture through said molecular sieve and desorbing the adsorbed gas from said molecular sieve are performed alternately for each of said portions.

13. A method as defined in claim 6, wherein said gaseous mixture is passed through said molecular sieve for a period between substantially 0.5 and 5 minutes and at pressures between substantially 1 and 40 atmospheres, said desorption being effected by subjecting said molecular sieve to pressures lower than atmospheric pressure, and said desorption producing a gas which is richer in said oxygen than is said gaseous mixture.

14. A method as defined in claim 13, wherein an equilibrium with respect to adsorption of said oxygen and said nitrogen by said molecular sieve is not achieved during passage of said gaseous mixture through said molecular sieve.

15. A method as defined in claim 13, said gaseous mixture comprising air which has been neither dried nor freed of carbon dioxide, and said molecular sieve having a volume of substantially 20 cubic meters;

and wherein about 6000 cubic meters of said air is passed through said molecular sieve during a period of substantially 100 seconds and at a pressure of substantially 1.05 atmospheres, said desorption being carried out for a period of substantially 100 seconds and at a pressure of substantially 50 torr, and said desorption producing a gas containing about 51 percent by volume of said oxygen and 49 percent by volume of said nitrogen.

16. A method as defined in claim 6, said gaseous mixture comprising air, and said molecular sieve having a volume of substantially 1 liter;

and wherein said air is passed through said molecular sieve for a period of substantially 1 minute and at a velocity of substantially 30 centimeters per second, said desorption being effected by subjecting said molecular sieve to pressures lower than atmospheric pressure, and said desorption producing a gas which contains a minimum of about 35 percent by volume of oxygen.

17. A method as defined in claim 16, wherein said desorption produces a gas containing between substantially 35 and 60 percent by volume of oxygen.