WO1997005944A1

WO1997005944A1 - Oxygen sorbent and process for producing it

Info

Publication number: WO1997005944A1
Application number: PCT/DE1996/001414
Authority: WO
Inventors: Grete Bach; Gudrun KÖTTER; Sinaida Tichonova Dimitrieva
Original assignee: Ifn Gmbh
Priority date: 1995-08-04
Filing date: 1996-07-30
Publication date: 1997-02-20
Also published as: DE19528783A1

Abstract

The invention relates to sorbents capable of removing oxygen and other impurities from technical gases. The aim of the invention is to find sorbents which, by comparison with prior art sorbents like molar filters, metals and metal oxides or active charcoal, have considerably higher retaining capacities for trace impurities, are simple to produce and the sorption capacity of which can easily be adapted for various purposes. This aim can be achieved by the use as sorbents of lithium and boron-containing co-ordination complexes, suitable examples of which are especially those of the types Li[B(OX)4] (lithium borates) and Li[BX4] (lithium boranes), where X = n- and/or iso-CH3-C8H17 or C6H5, and Li[BF4] or mixtures of said complexes. Said complexes are produced in a solid-phase reaction at 45 - 50 °C and may be used as individual compounds or as mixtures of any individual compounds of said structure in any combination. Heat treatment at temperatures < 120 °C and pressures of 0.05-0.03 Pa increases the adsorption capacity. When used up, the sorbents can be generated by heating to 250 °C at normal pressure or to 150-180 °C and pressures of 0.02-0.05 Pa and re-used for gas purification.

Description

Sorbent for oxygen and process for its manufacture Description

The invention relates to sorbents for oxygen on the basis of a new class of substances not previously used for this application and to a process for their production which differs from the classical synthesis processes of this class of substances. The sorbents are suitable as adsorbents for cleaning inert gas and can be regenerated after use

Essentially two methods are used to remove oxygen from gas mixtures. A method which has been known and used for a very long time is based on the use of metals and metal oxides which chemically bind the oxygen to be removed from a gas mixture. Very different metals can be used for this, with metals and metal oxides generally being applied to carrier materials.

It is known e.g. the use of finely divided copper and copper oxide (DE 1 106 293, DE 1 544 007, DE 2 102 039), nickel (DD 224229) and nickel oxide (DE 1 217348) and manganese oxide (DE 1 667 129). However, oxidic metal-containing cleaning compositions must be activated at high temperatures before they can be used in a hydrogen stream. Even when directly using metals such as titanium (DE 2 553 554),

Chromium (DE 1 657 129) or Geltem made of metal alloys (DE 3 926 015) requires high temperatures of up to 1000 ° C for effective cleaning, and a reduction of the foreign gases to less than 1 ppm is not possible in all of the processes mentioned, which means the pure ¬ does not meet the purity gas requirements for many areas of application. The use of activated carbon, as described in DE 3 825 725, or of molecular sieve cokes

(DE 3 433 058, DD 133 195) does not lead to higher degrees of cleaning. Finally, molecular sieves have often been proposed (DE 3 632 995, DE 2 400492) in order to remove oxygen and other gaseous impurities from noble and inert gases. However, molecular sieves generally only remove impurities that correspond to the respective pore volume of the zeolite. Multiple impurities can therefore only be removed using various molecular sieves or other sorbents, the production of which is complex and expensive and which necessitates complicated cleaning technology. The absorption capacity of such metallic or oxidic sorbents is also not very high, so that regeneration is necessary in short periods of time. A fundamental disadvantage of molecular sieve sorbents is also that it is only possible with great effort

Eliminate trace impurities below 1 ppm.

In US 42 38 464 and US 48 67 956 lithium boron complexes have been described which are said to be suitable for the adsorption of carbon dioxide. They consist exclusively of B, lithium (or another alkali or alkaline earth metal) and oxygen and are intended for use in life-saving systems. They are based on the principle that the amounts of up to 30% of oxygen built into the structure of the lithium-boron complex as hydroxides, oxides, peroxides, superoxides or ozonides are deliberately exchanged for CO ₂ if required. whereby oxygen is released. These systems, which can only be produced and used under extreme reaction conditions using ultra-high vacuum and which are also very unstable, are not suitable and are not intended for gas purification. The invention is therefore based on the object of finding sorbents which overcome the disadvantages of the known sorption processes, have a considerably higher absorption capacity for trace impurities in comparison with known sorbents, which are simple to produce and use and whose sorption capacity is slightly different for different purposes can be adjusted

According to the invention, the object is achieved by using coordination complexes containing lithium and boron as sorbents, a class of substances which has been known for a long time (Hollemann-Wiberg, Textbook of Organic Chemistry, 91st-100th edition, Berlin , New York 1985, pp. 834/835), but has not previously been used for the removal of gaseous trace contaminants from inert gases. The new sorbent class has surprisingly excellent application properties and far exceeds the absorption characteristics of known sorbent systems. Complexes of the general formula Li [B (OX) J (lithium borates) and LifBXJ (lithium boranes) have proven to be particularly suitable for the application described. X can be an alkyl substituent with a normal or iso structure, but also an aryl radical. Coordinating complexes of the structure given, in which X is an aryl radical, surprisingly show higher absorption capacities for impurities than complexes in which X are alkyl substituents. In the case of complexes with alkyl substituents, the sorption capacity decreases with increasing chain length and remains constant in the case of alkyl substituents with C numbers> 8. The use of sorbent complexes with alkyl substituents> C _g H _{] 7} is therefore not expedient. However, even for such complexes, the sorption capacity is still considerably above the values which are achieved with known sorbents, for example with molecular sieves

The coordination complexes of the general formulas Li [B (OX) J and LifBXJ can be used both as individual compounds and as mixtures of compounds of both types of complexes with the same or different substituents X, the mixture composition being chosen as desired can, without the sorption ability deteriorating. Surprisingly, it was further found that a particularly high adsorption ability is achieved if complexes of either the LifB (OX) J type or the LifBXJ type or mixtures of both complex types are used in any composition, in which instead of complex components with only a single defined stub substituent X mixtures of compounds with several different homologous alkyl and / or aryl substituents are used Complexes with only one defined substituent X The use of such complex mixtures also has the advantage that no pure, individual starting compounds are required for the synthesis of the complexes, which are very expensive, but that technical fractions can be used which are more easily accessible and Often, they can even be had cheaply as previously unused pre- or post-fractions of technical production processes

A completely new synthetic process was found for the production of the sorbents, which has many advantages over the classic production methods. Thus, when using the new production method, the effort involved in producing the sorbent complexes can be drastically reduced by synthesizing the borate complex LifB (OX). J from the starting components fB (OX),] and Lι (OX) or the synthesis of the borane complex LifBXJ from the starting components BX, and LiX without using solvents in a solid phase reaction in an inert gas atmosphere. The reaction can be carried out with or without mixing, the reaction temperature must not exceed 45 - 50 ° C This type of ReaWon management is new. It has many advantages over conventional synthesis variants. It is particularly advantageous that the complex and uncomfortable handling of flammable solvents may not be necessary, so that their energy-intensive evaporation under vacuum is not necessary, which means that several process steps can be saved compared to conventional synthesis methods.

An increase in the adsorption capacity of the complexes Li [B (OX) J and LifBXJ can be achieved if the complexes are used for 1 - 1.5 h at temperatures <120 ° C in a vacuum at 0.5 - 0.03 Pa before use as a sorbent heated.

In addition to the complexes of the type Li [B (OX) J and LifBXJ, a lithium-boron complex with fluorine substituents (LifBFJ) can also be used as a sorbent for the adsorption of trace impurities. It has an even greater absorption capacity than the lithium borate and lithium borane complexes.

The rate of absorption and the absorption capacity of the complexes described increase in the order LifB (OX) J <LifBXJ <LifBFJ.

All the sorbents mentioned can be easily regenerated by heating them to 250 ° C. If the thermal desorption is carried out in a vacuum at 0.02 - 0.05 Pa, the desorption temperature can be reduced to 150 - 180 ° C. The lithium borate and lithium borane complexes retain their adsorption capacity over 12 - 15 use / regeneration cycles. LifBFJ has a practically unlimited service life and achieves a high adsorption capacity without any thermal preactivation.

The new sorbent class according to the invention has greatly improved adsorption properties compared to known sorbents. Their absorption capacity and the absorption speed are considerably higher, so that trace impurities can be removed from gases quickly and with a great depth of purification. Another advantage of the new sorbent class is the simple manufacturing and regeneration technology. A significant advantage over known sorbents is also the possibility of tailoring the properties of the sorbent to specific applications by using complex mixtures. The sorbents according to the invention and their production methods are described below using examples.

Example 1. Synthesis of lithium tetramethyl borate

1.52 g (0.04 moles) of lithium methylate (CH ₃ OLi) were introduced into a glass flask or a friction bowl and 4.16 g (0.04 moles) of boron trimethyl oxide B (OCH ₃ ) _{3 were} rapidly added with mixing or grinding . The synthesis of the sorbent complex was carried out in a hermetic chamber (box) in an argon or high-purity nitrogen atmosphere. The reaction proceeds with the development of heat. The reaction mixture is then heated to 45-47 ° C. It changes into a solid monolithic block, which after a rest period of 1 - 1.5 hours when shaken, disintegrates into very fine crystals of white color. The elemental analysis gave the following values for the C and H content of the complex [B (OCH ₃ ) JLi: C = 41.97%, H = 8.35%. The theoretical values are C = 42.25%, H = 8.45%. A partial sample of the complex of 0.5 g (0.0035 moles) was first kept in a vacuum at 0.02 Pa and then exposed to an oxygen atmosphere at 20-25 ° C. under normal pressure in order to determine the oxygen uptake.

After a holding time of 35-40 minutes, the sample was again subjected to a vacuum at 20-25 ° C. in order to remove free gaseous and physically adsorbed oxygen. The chemosorbed oxygen was expelled by slowly heating the sample (at a linear heating rate of 13-15 ° C./min at 230-250 ° C. The amount of thermally desorbed oxygen was determined by gas chromatography and gravimetry. It was 0.225 g (0.007 mol ) O ₂ , that is 45% by mass based on the weight of the sorbent.

Example 2. Synthesis of lithium tetrabutyl borate

1.6 g (0.002 moles) of lithium butylate (QJH _g OLi) were introduced into a glass flask or a friction bowl and 4.6 g (0.002 moles) of boron tributyl oxide B (OC ₄ H _< ,) _{3 were} rapidly added with mixing or grinding. The synthesis of the sorbent complex was carried out in a hermetic chamber (box) in an argon or high-purity nitrogen atmosphere. The reaction proceeds with the development of heat. The reaction mixture is then heated to 42-43 ° C. It changes into a solid monolithic block, which after a rest period of 1 - 1.5 hours when shaken, disintegrates into very fine crystals of white color. The elemental analysis gave the following values for the C and H content of the complex [B (OQ, H ₉ ) JLi: C = 62.03%, H = 1 1.8%. The theoretical values are C = 61.49%, H = 1 1.61%. A partial sample of 0.93 g (0.003 mole) of the complex was first kept in a vacuum at 0.015-0.02 Pa and then exposed to an oxygen atmosphere under normal pressure at 20-25 ° C. in order to determine the oxygen uptake. After a holding time of 35-40 minutes, the sample was again subjected to a vacuum at 20-25 ° C in order to remove free and physically adsorbed oxygen. The chemosorbed oxygen was heated to 220 ° C by slowly heating the sample at a linear heating rate of 13 - 15 ° C / min. The amount of thermally desorbed oxygen was 0.192 g (0.006 mole), which is 20.64 mass% based on the weight of the sorbent.

The regenerated sorbent complex was subjected again to the chemosoφtion with oxygen under the conditions specified above after the thermodesoφtion. The amount of thermally desorbed oxygen in the second Soφtions- / Desoφtions cycle increased by 0.048 g (5.15%) and was 25.8% based on the mass of the sorbent complex.

1.25 g (0.004 moles) of the complex [B (OC ₄ FI ₉ ) ₄ ] Li were kept in a vacuum (0.05-0.07 Pa) at 115 ° C for 1.5 h before being used as an oxygen sorbent . After this procedure, the sample was cooled in a flask to 20-25 ° C., the flask was filled with oxygen to atmospheric pressure and left under these conditions for 40 minutes. The sample was then again kept at 20-25 ° C. under vacuum in order to remove excess oxygen and physically adsorbed oxygen. The oxygen chemosorbed on the complex was desorbed by slowly heating the sample at a heating rate of 13 - 15 ° C / min to 220 ° C. The amount of thermally desorbed oxygen was 0.304 g (0.0095 moles), which is 24.32% based on the mass of the sorbent complex. The thermal pretreatment of the complex increased the oxygen chemosoφtion by 3.67% compared to the sorbent complex without thermal sample treatment. Example 3. Synthesis of lithium tetraoctyl borate

1.4 g (0.01 mole) of lithium octylate (C ₈ H ₁₇ OLi) was introduced into a glass flask or a grinding bowl and, while mixing or grinding, 4.0 g (0.01 mole) of boron tri-octyl oxide B (OC _g H ₁₇ ) ₃ added. The synthesis of the sorbent complex was carried out in a hermetic chamber in an argon or high-purity nitrogen atmosphere. The reaction proceeds with the development of heat. The reaction mixture is then heated to 35-37 ° C. It changes into a solid monolithic block, which after a rest period of 1 - 1.5 hours when shaken, disintegrates into very fine crystals of white color. The elementary analysis gave the following values for the C and H content of the complex [B (OC ₈ H ₁₇ ) JLi: C = 71.23%, H = 12, 15%. The theoretical values are C = 71, 91%, H = 12.73%.

0.5 g (0.0011 mole) of the complex was first kept in a vacuum at 0.018-0.02 Pa and then exposed to an oxygen atmosphere at 20-25 ° C. under normal pressure in order to determine the oxygen uptake. After a holding time of 40 minutes, the complex sample was again kept in a vacuum at 23 ° C. in order to remove free and physically adsorbed oxygen. The chemosorbed oxygen was expelled by slowly heating the sample at a linear heating rate of 13-15 ° C./min at 245 ° C. The amount of thermally desorbed oxygen was 0.07 g (0.0022 moles), which is 11.68 mass% of the weight of the sorbent complex. The regenerated sorbent was subjected again to the chemosoφtion with oxygen under the conditions specified above after the thermodose.

The amount of thermally desorbed oxygen in the second Soφtions-ZDesoφtions cycle increased to 0.023 g (3.87%) and was 15.73% based on the mass of the sorbent.

0.8 g (0.0015 mole) of the complex [B (OC ₈ H _I7 ) JLi was first kept at 120 ° C. in a vacuum (0.03 - 0.04 Pa) for 1.5 h before being used as an oxygen sorbent. After this procedure, the sample was cooled in a flask to 22 ° C., the flask was filled with oxygen up to normal pressure and left under these conditions for 40 min. The sample was then again kept at 22 ° C. under vacuum in order to remove excess oxygen and physically adsorbed oxygen. The oxygen chemosorbed on the complex was desorbed by slowly heating the sample at a linear heating rate of 13-15 ° C / min at 246-250 ° C. The amount of thermally desorbed oxygen was determined by gas chromatography to 0.122 g (0.0038 mole) O ₂ , which is 15.25% based on the weight of the sorbent. The thermal pretreatment of the sorbent in a vacuum at 120 ° C increased the oxygen chemosoφtion by 3.4%.

Example 4 Synthesis of lithium tert-butyl tributyl borate 2.0 g (0.025 mole) of tert-lithium butoxide (tert-C ₄ H ₉ Li) were introduced into a glass flask or a grinding bowl and were rapidly mixed or ground 5.75 g (0.025 mole) of boron tributyl oxide B (OC ₄ H ₉ ) _{3 were} added. The synthesis of the sorbent complex was carried out in a hermetic chamber in an argon or high-purity nitrogen atmosphere. The reaction proceeds with the development of heat. The reaction mixture is then heated to 42.degree. It changes into a solid monolithic block, which after a rest period of 1 - 1.5 hours when shaken, disintegrates into very fine crystals of white color. The elemental analysis gave the following values for the C and H content of the complex [tert-C ₄ H ₉ OB (OC ₄ H ₉ ) ₃ ] Li: C = 61.15%, H = 11.33%. The theoretical values are C = 61.94%, H = 1 1.61%. 0.992 g (0.0032 moles) of the complex were first kept in a vacuum at 0.018 Pa and then exposed to an oxygen atmosphere at 23 ° C. for 40 minutes under normal pressure. The complex sample was then again kept at 23 ° C. in vacuo in order to remove free gaseous and physically adsorbed oxygen. The chemosorbed oxygen was expelled in vacuo (0.03 Pa) by slowly heating the sample at a linear heating rate of 13-15 ° C / min to 170 ° C. The amount of thermally desorbed oxygen was 0.205 g (0.0064 mole), which is 20.67 mass% based on the weight of the sorbent. The sorbent complex regenerated in this way was then subjected again to chemo-soφtion with oxygen under the conditions specified above and later heated again. The amount of oxygen thermally sorbed in the second Soφtions- / Desoφtions cycle increased by 0.038 g (3.8%) and was 24.47% based on the mass of the sorbent used.

1.18 g (0.0038 mole) of the complex [tert.-C ₄ H ₉ OB (OC ₄ H ₉ ) ₃ ] Li, which was prepared by the method described above, was in the Va¬ before its use as an oxygen sorbent vacuum (0.06 Pa) heated to 115 ° C and held at this temperature for 1.5 h. After this procedure, the sample was cooled to 23 ° C. in a flask, the flask was filled with oxygen to atmospheric pressure and left under these conditions for 35 min.

The complex sample was then again held at 23 ° C under vacuum to remove excess oxygen and physically adsorbed oxygen. The oxygen chemosorbed on the complex was expelled by slowly heating the sample in vacuo (0.03-0.04 Pa) to 170 ° C. over a period of 1.5 h - 2 h. The amount of the thermally desorbed oxygen was 0.298 g (0.0093 moles), which is 25.25% based on the mass of the sorbent complex. The thermal pretreatment of the sorbent in a vacuum at 1 15 ° C increased the oxygen chemosoφtion by 4.58% compared to the test without thermal test treatment.

Example 5. Synthesis of lithium tert. - Butyl tribenzyl borate 5 1.2 g (0.15 moles) of lithium tert were placed in a glass flask or a friction bowl. - butylate

(C ₄ HoOLi) and 5.13 g (0.015 moles) of boron tri-benzyl oxide BtOCH-QHJ, added quickly while mixing or grinding. The synthesis of the sorbent complex was carried out in a hermetic chamber in an argon or high-purity nitrogen atmosphere. The reaction proceeds with the development of heat. After the reaction of the components, the reaction mixture is heated to 46-47 ° C. It changes into a solid monolithic block that, after a rest period of 1.5 hours, disintegrates into very fine crystals of white color when shaken. The elementary analysis gave the following values for the C and H content of the complex [tert-QHpB (OCH ₂ C ₆ H ₅ ) JLi: C = 72.0%, H = 7.68%. The theoretical values are C = 71.10%, H = 7.1 1%. 5 A partial sample of the sorbent, namely 0.844 g (0.002 mole), was kept in a vacuum at 0.027 Pa and then left in an oxygen atmosphere for 45 minutes at 22 ° C. under normal pressure.

After the oxygen uptake, the sorbent sample was again kept at 22 ° C. in a vacuum in order to remove free gaseous and physically adsorbed oxygen. The chemo-sorbed oxygen was expelled by slowly heating the sample at a linear heating rate of 13 - 15 ° C / min to 240 ° C. The amount of thermally desorbed oxygen was 0.168 g (0.0058 moles), which is 22.04% by mass based on the sorbent complex. The amount of chemosorbed oxygen on the sorbent complex was determined by gas chromatography. 5 The regenerated sorbent complex was again chemo- soφtion subjected to oxygen under the conditions specified above.

In the second Soφtions- / Despoφtions cycle there was no increase in the thermodesorbed

Amount of oxygen observed.

Example 6. Synthesis of lithium-tert-butyltribenzylbor In a glass or porcelain reactor which was installed in a hermetic chamber, 5.68 g (0.02 moles) of tribenzylboron B (CJH ₂ C ₆ H _J ) ₃ were introduced and in addition 1.28 g (0.02 mole) of tert-butyllithium (C ₄ H, Li) were added simultaneously in small batches, with constant mixing, using a metering device. The reaction was carried out under an argon atmosphere. The reaction took place with the development of heat. The temperature in the reaction zone was kept at 18-20 ° C. via the metering rate or by cooling the reactor. The reaction mixture in the reactor gradually turned into a solid block which, after standing for two hours, disintegrated into small crystals of white color when shaken. The elemental analysis showed for the C and H content of the complex [tert. - C ₄ H ₉ B (CH ₂ C ₆ H ₅ ) ₃ ] Li the following values: C = 85.70%, H = 7.98%. The theoretical values are C = 86.21%, H = 8.62%.

A partial sample of the complex, namely 0.696 g (0.002 moles), was subjected to a vacuum at 0.03 Pa and then kept in an oxygen atmosphere at 23 ° C. under normal pressure for 45 minutes. After the oxygen uptake, the complex sample was again kept in a vacuum at 23 ° C. in order to remove free gaseous and physically adsorbed oxygen. The chemosorbed oxygen was expelled to 150 ° C. by slowly heating the sample at a linear heating rate of 13-15 ° C./min in a vacuum (0.02 Pa). The amount of thermally desorbed oxygen was 0.16 g (0.05 mole), which is 23.0% by mass based on the mass of the sorbent. The amount of chemosorbed oxygen on the sorbent complex was determined by gas chromatography.

The sorbent complex regenerated in the manner described was then subjected to a second chemosoφtion stage with oxygen under the conditions described above. No increase in the thermodesorbed oxygen was observed in the second desorption cycle. The sorbent complex was stored either in vacuo or under argon.

Example 7. Synthesis of lithium tetraoctylboron

In a glass or porcelain reactor, which was installed in a hermetic chamber, 5.25 g (0.015 moles) of trioctylboron B (C _g H ₁₇ ) ₃ were introduced and 1.8 g (0.015 moles ) Lithium octyl (C ₈ H _{] 7} Li) added. The reaction took place with the development of heat. The temperature in the reaction zone was kept at 18-20 ° C. via the metering rate or by cooling the reactor. The synthesis of the sorbent complex was carried out in an argon atmosphere. The reaction mixture gradually changed into a solid block, which after standing for two hours disintegrated into small crystals of white color when shaken. Elemental analysis gave the following values for the C and H content of the complex fB (C _g H ₁₇ ) JLi: C = 82.31%, H = 14.98%. The theoretical values are C = 81, 70%, H = 14.47%. A partial sample of the complex, namely 0.47 g (0.001 mole), was kept in a vacuum at 0.03 Pa and then held for 45 minutes at 20-22 ° C. in an oxygen atmosphere under normal pressure. After the oxygen uptake, the sorbent sample was again left in vacuo at 20-22 ° C. in order to remove free gaseous and physically adsorbed oxygen. The chemosorbed oxygen was expelled to 150 ° C. by slowly heating the sample at a linear heating rate of 13-15 ° C./min in vacuo (0.02 Pa). The amount of thermodesorbed oxygen was 0.064 g (0.02 mole), which is 13.62% by mass. based on the mass of the sorbent complex. The regenerated sorbent complex was again subjected to the chemosoφtion with oxygen under the conditions described above after the thermodesoφtion. The amount of thermally desorbed oxygen increased in the second Soφtions- / Desoφtions cycle by 0.06 g (1.08%) and was 14.7% of the mass of the sorbent complex.

Example 8. Synthesis of lithium boron tetrafluoride The complex [BFJLi is a commercial product and was used without further pretreatment for the oxygen soapy. A sample of the complex in an amount of 0.376 g (0.004 moles) was first kept under vacuum (0.025 Pa) and then exposed to an oxygen atmosphere at 22 ° C. for 45 minutes under normal pressure. The complex was then kept under vacuum again in order to remove free gaseous oxygen and physically adsorbed oxygen. The chemosorbed oxygen was then heated by slowly heating the sample to 240 ° C. at a linear heating rate of 13-15 ° C./min in the course of 1.5 hours. The amount of thermally desorbed oxygen was determined by gas chromatography and was 0.256 g (0.08 mole), which is 68.1% of the mass of the sorbent complex. The regenerated sorbent complex was again exposed to an oxygen chemosoφtion under the conditions described above. The amount of thermosorbed oxygen did not change in the second absorption / deodorization cycle.

Example 9. Use of lithium tetra butyl borate to remove oxygen from argon

Using the example of the complex [B (OC ₄ H ₉ ) ₄ ] Li, the suitability of the sorbents for eliminating oxygen from argon was tested under dynamic conditions. For this purpose, 0.31 g (0.001 mole) of the complex was applied to a filter through which argon with an oxygen content of 0.2% by mass flowed over a period of 2-2.5 hours. The oxygen sorbed on the complex was driven off by heating the sorbent to 150 ° C. The amount of thermally desorbed oxygen was determined gravimetrically to be 0.019 g (0.0006 mole oxygen), which is 6% based on the mass of the sorbent complex. After thermal regeneration, the sorbent complex was tested again for its absorption effects for oxygen in the filtration of oxygen-containing argon under the conditions mentioned above.

The sorbed oxygen was expelled by heating the sorbent to 150 ° C and determined gravimetrically to 0.0248 g (0.0008 mole oxygen), which is 8% of the mass of the sorbent complex. The filtered argon no longer contained any traces of oxygen which could be detected by gas chromatography.

Claims

claims

1. Sorbents for oxygen, characterized in that lithium and boron-containing complexes of the general formulas Li [B (OX) J (lithium borates) and / or Li fBXJ (lithium boranes) are used, where X - n and / or iso -Alkyl- and aryl groups can be ..

2. Sorbents according to claim 1, characterized in that the C number of the alkyl substituents is 1-8.

Sorbents according to Claims 1 and 2, characterized in that the lithium borate and lithium borane complexes are used as mixtures with one another or as mixtures of various individual lithium alkyl borates and / or lithium alkyl boranes with any alkyl substituents and / or aryl substituents.

4. Sorbents according to claim 1, characterized in that as a coordination complex

LiBF ₄ is used.

5. Sorbents according to claim 4, characterized in that LiBF _{4 are used} as an individual compound or in a mixture with complexes of the type LifB (OX) J and / or LifBXJ in any mixture composition.

Process for the preparation of lithium borate and lithium borane complexes, characterized in that trialkyl borate (B (OX) ₃ ) and lithium alcoholate (LiOX) as starting substances for the production of the lithium borates (LifB (OX) J) and for the production of the lithium boranes (LifBXJ ) as starting substances trialkylboron (BX ₃ ) and alkyl lithium (LiX) at temperatures <50 ° C under an inert gas atmosphere in a solid phase reaction.

7. A process for the preparation of sorbents according to claim 6, characterized in that the lithium borate and the lithium borane complexes after synthesis and before their use as sorbent for 1 - 1.5 h at temperatures <120 ° C in a vacuum of 80 - 0.03 Pa are heated.