DD154690A1 - METHOD FOR SEPARATING OXYGEN FROM GASES - Google Patents

Abstract

The invention includes a method for the selective separation of oxygen from oxygen-containing gases, in particular air, by means of microporous adsorbents at temperatures between +20 and -78 degrees C using the molecular sieve effect of modified zeolite Na high + A. The modification is carried out by ion exchange with Li high + ions over ion exchange rates of 90%, in particular over 95%, or by ion exchange with Ba hoch 2+ ions in the range of 5 to 45%, in particular 15 to 30% Ba hoch 2+, and subsequent thermal treatment in a shallow Schuettung under air access at 450 degrees C. According to the inventive method can be used in varying degrees with oxygen-enriched gases, eg Nitrogen-oxygen mixtures, for various applications, e.g. the chemical industry, environmental protection and health care.

Description

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Title of the invention

Process for the separation of oxygen from gases

Field of application of the invention

The invention relates to a novel process for separating the oxygen from gases containing such, in particular from the air, by an adsorption-desorption process. In this way, oxygen-enriched gases, e.g. Nitrogen-oxygen mixtures, for various applications, e.g. the chemical industry, metallurgy, environmental protection and health care.

Characteristic of the known technical solutions

For around 20 years, selective adsorption processes have increasingly been used to remove oxygen from gases. However, the approximately 50 known in this regard and mostly set out in patent specifications for this purpose is a fundamental deficiency; the corresponding adsorbents selectively adsorb nitrogen, that is, the component involved in the aggregation of air at almost 80 % . The selective adsorption of nitrogen is energetic, because the nitrogen by its quadrupole moment has a strong interaction with the adsorbent, which is stronger the more polar the adsorbent is ·

Recently, however, methods based on the selective adsorption of oxygen have become known. This procedure is based on the fact that the microporous adsorbent has a pronounced molecular sieve effect

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a pore size range in which the nitrogen (3.64 $. Kinetic molecular diameter) to oxygen (3.46 -S kinetic molecular diameter) is kinetically impeded in its diffusion into the micropores, and thus the energetically preferred nitrogen adsorption does not come to fruition. As such adsorbents were of Jüntgen and coworkers (Chem-Ing.-Techn. ^ (1973) 533) molecular sieving used. However, the latter have some disadvantages compared to zeolitic adsorbents, for example, lower capacities at higher adsorptive concentrations required. There are also some methods known to use zeolitic materials for selective oxygen adsorption; but is contrary to the fact that the pore sizes are largely predetermined by the zeolite and only expensive to the required narrow pore size range adjustable. Accordingly have the known .gewordenen oxygen-selective adsorption on zeolitic materials, for example to ^ -exchanged zeolite K ⁺ Na ⁺ A (US-OS 3,282,028), or Ca ⁺⁺ - ^M ordenit (Barrer, Trans Faraday Soc £ 5 (.. 1949) 1358) or clinoptilolite (Cicisvili, Advan, Chem. Ser. 121 (1973) 291) have only low oxygen capacities and selectivities.

It is also known that there is a lattice narrowing due to decreasing thermal lattice vibrations at low temperatures on narrow-porous adsorbents. Thus, a preferential adsorption of oxygen was on the zeolite Na ⁺ A which is nitrogen-selective at temperatures above 150 ⁰ K, observed (BRD-OS 1259857) "In addition, Präadsorptmoleküle to ^ orenverengung can lead at 8O ⁰ C (" cut-off "-Effect). The disadvantage here are the required low separation temperatures.

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Object of the invention

The object of the invention is a process for preferentially separating the oxygen from such containing gases, especially from the air, with high capacity and selectivity.

Explanation of the essence of the invention

The invention has for its object to find a correspondingly modified new microporous adsorbent for the adsorption of oxygen from gases containing such, in particular from air, ·

It has been found that to achieve an oxygen selectivity of zeolite Ua ⁺ A due to reduction of the -forendurchmesser a more than 90 % _t, preferably over 95 %, Li ⁺ ion-exchanged zeolite NaLiA is suitable, or to 5 to 45 % _t preferably 10 to 30%, the Na ⁺ cations in the zeolite Ha ⁺ A are exchanged for Ba cations, and the zeolite thus obtained between 400 and 600 ⁰ C, preferably at 450 ⁰ C, in a shallow bed (flat bed) is activated with access of air , The X-ray structure search shows a reduction of the unit cell by 0.3 . This reduction is applicable according to the invention to the adsorptive separation of the oxygen from the air in such a way that the nitrogen is largely excluded kinetically.

Since the oxygen separation is based on a kinetic effect according to the invention, corresponding characterizations were also carried out dynamically by gas chromatography and monitoring the kinetics of static adsorption. Table 1 contains the specific gas chromatographically determined retention volumes at 195 ⁰ K for nitrogen and oxygen (under Deduction of the dead time) when using zeolite structures according to the invention in comparison to unmodified zeolite Na ⁺ A.

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The gas adsorption is carried out dynamically and allows up to an adsorbent loading of about 40 % selective oxygen adsorption. As the loading or adsorption time increases, N ₂ -sorbate is increasingly enriched so that the ratio between nitrogen and oxygen in the adsorbate can be adjusted by selecting the time for the termination of the adsorption phase.

The desorption can be carried out thermally and / or by reducing the pressure, with temperatures of 100 to 150 ^° C. being sufficient for the former method. Pur the removal of any of the kuf t adsorbed water vapor, it is appropriate to activate at 350 to 400 ⁰ C.

Table 1:

^V R sp N ₂ ^V R sp ml / g " ml / g

Zeolite Na ⁺ A (untreated) 75 195 ⁰ K. Modification according to the invention claim: 25 cm UaLiA, 95 % exchange rate 9 4 mm UaBaA .11 % Ba | i "36 % Ba ^ ⁺ .8,5 7 Conditions of gas chromatography: Column temperature ' Column length: Column diameter:

26

14

20 14

"Column filling: 2 g dehydrated

Zeölith

Hp flow rate: 1 ml / s Sample amount: _ 0.5 ml of air

Activation: 3 η 45O ⁰ C, flat bed,

air access

Deformation: pressing at ca * 2000 atm,

ΤΓΛνινι · Ρ · ο1, - + · ϊ η «Π OP; _ OA Π mm

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Embodiments:

example 1

A zeolite Ha ⁺ A is subjected to the batch process at 60 ⁰ G by means of a 1N solution of LiCl ion exchange. After adjusting the equilibrium after about 6 h, the zeolite is separated from the solution and re-introduced into LiCl solution. This process v / ill be optionally repeated several times until the flame photometry analysis carried out a - ¹ ones exchange degree of more than 90% _t preferably about 95%, is obtained. After aspirating, washing a little with warm water, drying (11O ⁰ C), pressing (2000 atm) and activating (3h, 45O ⁰ C) of the sample, the installation is carried out in the separation column. Table 1 shows the results of air separation »

Example 2.

A zeolite Na ⁺ A is subjected to ion exchange in a batch process at 6O ⁰ C by means of an O ₁ 1n BaBr _o solution.

2+

The amount of Ba in VaI contained in the solution versus the Ua ⁺ contained in the zeolite is 10 % higher than that required for the desired ion exchange. Thus, ζ _β Β _β achieves an offer of 0.055 meq Ba (as 0.1n solution of BaBr _? ) At a level of 25 g zeolite HaA (corresponding to 0.138 meq Ha), an ion exchange rate of 36 %.

The conditions of the preparation for the Gasauftrennung entsprechenr''Beispiel 1, but care must be taken that the activation of 3 hours at 450 ⁰ C is carried out under air access "Table 1 shows the results of air separation.

Claims (1)

-6 - 22 33 38 Claim for invention 1 "" Process for the selective separation of oxygen from oxygen-containing gases, preferably air, on microporous adsorbents, characterized in that these gas mixtures at temperatures between + 25 and -78 ⁰ C _s, preferably at -78 ° C »over narrow pore crystalline zeolites, in particular zeolite Na A, are conducted with an effective pore diameter of 4.0 to 4.2 ä, to about 90% preferably about 95% ₉ ^m t it Li ions have been exchanged · 2 * Procedure according to point 1 ·, characterized in that the gas mixtures are passed through zeolites of the type Na ⁺ Ba ⁺⁺ A, wherein their Na ions between 5 and 2+ 45 % t, preferably 1o to 30 %, are exchanged with Ba ions, and which has been thermally activated in a shallow bed under air admission