EP1848789A1

EP1848789A1 - Processing or working machine comprising an ionic liquid as the service fluid

Info

Publication number: EP1848789A1
Application number: EP06708277A
Authority: EP
Inventors: Claus Hilgers; Marc Uerdingen; Markus Wagner; Peter Wasserscheid; Eberhard Schlücker
Original assignee: Merck Patent GmbH; Solvent Innovation GmbH
Current assignee: Merck Patent GmbH
Priority date: 2005-02-16
Filing date: 2006-02-15
Publication date: 2007-10-31
Also published as: WO2006087333A1; US20080038123A1; DE102005007100A1; JP2008530441A

Abstract

The invention relates to a processing or working machine comprising a liquid as the service fluid, an ionic liquid constituting said service fluid. The invention also relates to the use of service fluids in processing or working machines, whereby an ionic liquid constitutes the service fluid and is used in particular as a lubricating fluid, confining fluid, sealing fluid, or a pressure transmission fluid.

Description

Process or working machine with ionic liquid as operating fluid

The invention relates to a process or working machine with a liquid as operating fluid.

Operating fluids for functional maintenance and / or safety are used in many conveying, working and operating principles of process and work machines.

Thus, in the field of process machines, such as pumps, in particular vacuum pumps, rotary vane pumps, vane pumps, piston pumps, diaphragm pumps, etc., in compressors, such as screw compressors, etc., and piston machines liquids, preferably oils, as a lubricating fluid, sealing fluid, barrier fluid, pressure transmission fluid , d. H. used in general as a working fluid. As a result, the use of a process machine is made possible in the first place, because it can be used, for example, to reduce the wear, the friction and the gap leakage current.

Typical examples of such applications are:

a) Hydraulic diaphragm pumps. In this case, oil or another liquid is used as hydraulic fluid for the membrane drive and as coupling fluid between the membranes;

b) Different types of vacuum pumps and compressors, such as rotary vane pumps, Roots pumps, rotary piston compressors, screw compressors, reciprocating compressors, Scrol I compressors, etc. Here are lubricating fluids for lubrication, but also for sealing the compressor bodies and for cooling the compressor bodies and the delivery fluids used; c) liquid ring vacuum pumps. These use liquids as operating fluid to generate the conveying effect (liquid piston), for lubrication and to absorb the heat of compression.

d) Work machines and work units such as motors, transmissions, hydraulic systems, etc. Here, liquids enter as lubricating fluids, i. for bearing lubrication, tooth lubrication, etc., as well as for power transmission, especially in hydraulic units, hydraulic cylinders, lifting devices, etc., for use;

As a result, there are certain benefits, including:

a) increase in efficiency, b) protection against wear and c) evaporative cooling, d. H. the liquid evaporates in the pump chambers when the evaporation temperature is exceeded and thus cools the process gas as the liquid absorbs part of the heat of compression.

However, such use of the known operating fluids in process and work machines faces serious disadvantages. Thus, the vapor pressure of such liquids determines the minimum pressure in a process machine, wherein in the case of evaporation of the liquid, it must again be expensively separated from the process gas.

Hydraulic diaphragm pumps are a typical example of the disadvantages described. Due to their hermetic properties and simultaneously high pressure rigidity and conveying accuracy, such hydraulic diaphragm pumps are preferably used for critical conveying tasks, such as conveying toxic, environmentally relevant or hygienic liquids, for conveying at high pressures and for precisely dosing any liquids. In this case, however, a multiple limiting factor is the hydraulic fluid which is used as pressure transfer fluid from the piston to the diaphragm. Usually this mineral oil or synthetic oil, for example, polyglycol with a variety of additives, or special oil is used. Due to the physiological dubiousness of this lubricant, glycerine is also used in food or biotechnology.

All these fluids have disadvantages. For example, when using mineral oil, dissolved gas absolutely limits the minimum suction pressure of the diaphragm pump to 0.4 bar. The thermal limit is reached at about 150 ⁰ C. In addition, there is a large change in viscosity due to temperature change. The use of synthetic oil shows the same drawbacks as with mineral oil, with the thermal limit being slightly higher.

Finally, the use of glycerol requires the use of inhibitors of biological decomposition. Nevertheless, the decomposition can not be prevented. The thermal limit is here only 95 ⁰ C. The viscosity is hereby set in a complex manner by mixing with water.

Another typical example of the disadvantages described are liquid ring vacuum pumps. Here, the rotating liquid ring is needed to seal the impeller chambers against each other and to transfer the necessary compression energy to the gas. The vapor pressure of the ring liquid limits the minimum achievable suction pressure level. At this suction pressure, the impeller chambers then completely fill up with the evaporating working fluid, and the pumping speed of the liquid ring vacuum pump drops to zero. Operating fluids used in practice, preferably water with a vapor pressure at ambient temperature of about 23 mbar and oils with a vapor pressure of about 1 mbar, therefore only allow operation in the so-called rough vacuum range. In contrast, in processes which require the so-called. Fine vacuum range, inevitably other compressors must be used become. However, these have disadvantages due to their operating principles compared to the use of a liquid ring vacuum pump. Especially in the chemical industry, the use of hydrocarbons to compress hydrocarbons is only possible with great safety precautions, since the compressors that can be used require an explosion-proof design.

Therefore, in order to reduce the vacuum area, studies have been conducted with oils and various aqueous-based fluids. However, the lowering of the suction pressure level could only be achieved up to a limit of 1 mbar. However, this minor extension of the field of use is associated with difficulties in handling the most toxic or environmentally hazardous operating fluid. At the same time, it had to be ensured that the ring liquid did not react with the usually aggressive or corrosive gas to be sucked off.

Finally, piston machines are another typical example of the occurrence of the disadvantages described. In such reciprocating engines, a possible technical solution for special applications would be to operate them for the purpose of gas or liquid conveyance with a liquid flask or a liquid feed piston, given a sufficient difference in density and immiscibility. However, this has so far failed at the limits of the known operating fluids, and that is because in the application of aqueous liquids, the known disadvantages, such as evaporation, corrosion, toxicity, gas solubility, etc. arise. The same applies to the application of organic liquids, since the disadvantages of evaporation, toxicity, volatility, etc. occur. Finally, the use of liquid metals has the disadvantages of toxicity, high cost, high density, difficult sealing, etc. The subsequently published DE 10 2004 024 967 A1 discloses the use of ionic liquids as working fluid (ie the liquid to be conveyed) for absorption heat pumps, absorption refrigerating machines and heat transformers. Gas conveying machines, hydraulic diaphragm pumps, liquid ring vacuum Recirculating and piston machines that use ionic liquids as operating fluids are not disclosed in DE 10 2004 024 967 A1.

DE 103 16 418 A1 discloses the use of ionic liquids as heat carriers for the indirect supply or removal of heat from a reactor. The document teaches that due to the higher heat absorption of the cooling media, a reduction in the drive power of the pump is possible and that no special pump arrangements for the promotion of ionic liquids are necessary. It is also disclosed that additional pump seals of the pumps with a barrier liquid are possible and that such barrier fluids may also be ionic liquids.

The present invention is therefore based on the object, a process or working machine of the generic type, which has a fluid as Betriebsflüs- sity designed such that the disadvantages are avoided, without losing the benefits of reaching previously used operating fluids.

In its most general embodiment, this invention relates to a device, in particular a pump, comprising an ionic liquid as the operating medium, in particular as a separating liquid and / or hydraulic fluid.

A first preferred embodiment of the present invention is a gas-conveying machine which is characterized in that it has an ionic liquid as the lubricating fluid.

A second preferred embodiment of the present invention is a hydraulic diaphragm pump which is characterized in that it has an ionic liquid as the hydraulic fluid.

A third preferred embodiment of the present invention is a liquid ring vacuum pump which is characterized in that it can be used as ring liquid. having an ionic liquid. This extends the working range of the pump to the fine vacuum range.

A fourth preferred embodiment of the present invention is a piston type machine characterized in that it is configured with a piston oscillating in a cylinder in the form of a liquid piston or an upstream liquid feed piston made of an ionic liquid. Due to the oscillating movement of the liquid piston, a gas, a low-density immiscible liquid or a high-density liquid can be promoted.

The invention further relates to methods of operating the above device using ionic liquids as the operating medium.

Advantageous embodiments thereof are described in the claims.

The invention is based on the essential idea of designing a process machine in such a way that the operating medium provided in it, that is, the operating fluid, is an ionic fluid. This results in amazing advantages, which are set out in detail below.

As is known, ionic liquids consist of ions, ie anions and cations, and are thus salts. However, in contrast to common salts, for example sodium chloride, they have a lower melting point and can be liquid even at room temperature. By definition, all salts which are liquid in pure form below 100 ^° C. are considered to be ionic liquids.

Ionic liquids can be referred to as liquid salts. They have an extremely low vapor pressure (10 ^"13 bars), have only small gas solubility, are non-flammable, are often physiologically harmless, are often thermally stable up to 250 ⁰ C and lubricity. The list of advantages that ionic liquids , is long, so ionic liquids make one umweit- and resource-saving replacement for the previously described fluids.

In the case of ionic liquids, a suitable gradual adjustment of the polarity and thus a tuning of their properties, in particular their solubility properties, is possible by suitable choice of cation and anion. The spectrum ranges from water-miscible ionic liquids, to water-immiscible liquids, to those that form two phases even with organic solvents. The clever use of these extraordinary properties of ionic liquids is the key to the successful use of these fluids in the sense of the invention.

The inventively provided use of an ionic liquid as a working fluid in process or working machines, the following parameters can be advantageously influenced as desired:

a) Lubricating effect b) Compressive stiffness c) Viscosity as a function of temperature d) Vapor pressure limit e) Chemical inertness f) Thermal inertness g) Solubility h) Physiological compatibility.

This can be achieved with ionic liquids, which improve the aforementioned parameters compared to the previously used operating fluids, the following advantages:

a) lowering the vacuum limit determined by the evaporation pressure. This is based on the fact that the extremely low evaporation pressure of an ionic liquid of about 10 ^"13 bar significantly reduces the achievable VA. For example, in the area of liquid ring vacuum pumps, in which an ionic liquid according to the invention can be used as ring liquid for use.

b) An existing lubricating effect in combination with higher temperature stability and lower vapor pressure leads to lower lubricant consumption and to the saving of oil separators with all lubricated vacuum pump types and compressors while reducing the achievable vacuum.

c) An achievable good lubricating effect in combination with physiological safety and thermal and chemical stability represents a major gain in economy and safety for lubrication requirements in sanitary and hygienic machines and apparatus. Typical examples include hydraulic diaphragm pumps for sanitary operation, gearboxes for hygienic operation, bearing lubrication requirements in hygienic operation, seal lubrication in hygienic operation, etc.

d) A higher compressive stiffness promises higher efficiencies for all pressure generators due to the lower compressibility and thus allows smaller machines for the same capacity.

e) A lesser drop in the viscosity when the temperature rises allows more stable operating conditions and lower leakage losses in pumps at high temperatures. This also increases the efficiency.

f) The low gas solubility and the very low vapor pressure of an ionic liquid allow their use according to the invention as liquid flasks for gases and certain liquids as well as hydraulic fluid for diaphragm pumps with low gas content and thus improved conveying accuracy. A special feature is that special ionic liquids are completely oxidized are willing and therefore can serve as a lubricant for oxygen compression or as a liquid piston.

g) The typical very low vapor pressure of an ionic liquid allows high suction heights for diaphragm pumps.

h) The chemical inertness of an ionic liquid allows its use as lubrication in chemical handling equipment.

Ionic liquids are therefore able to avoid the disadvantages described so far. Due to their extremely low vapor pressure of 10 ^"13 bar (liquid salt), they can achieve extremely low pressures in the vacuum technology and at the same time avoid contamination of the process gas in both vacuum pumps and compressors.

In addition, it is possible in this way to promote critical gases, such as pure oxygen, in liquid-lubricated machines, without causing oxidation or even fires.

Due to the inventively provided use of ionic liquids in process machines, it is now also possible to operate the aforementioned piston machines with a liquid piston, which consists of an ionic liquid, while avoiding the disadvantages described. Here, the use of ionic liquids also has the advantage that a reaction with the conveyed is excluded because they are highly inert.

Finally, even with liquid ring vacuum pumps due to the use according to the invention of ionic liquids as ring liquid, the use of these pumps is also made possible in the fine vacuum range. In this way, liquid ring vacuum pumps can be used instead of the previously used screw compressors, reciprocating compressors, rotating vane compressors, etc. be able to fully exploit their great advantages in terms of robustness, reliability and process reliability.

The disadvantages and difficulties encountered so far are circumvented by the use according to the invention of ionic liquids, since these can be adapted to the respective process conditions and the gases to be extracted. Thus, a reaction with the gas to be extracted can be surely prevented.

The advantages of using ionic liquids as operating fluid are explained below on the basis of the functional principle of a liquid ring vacuum pump and the limits of the fluids used to date.

Thus, a paddle wheel is eccentrically arranged in a cylindrical housing in a liquid ring vacuum pump. The operating fluid in the housing forms due to the rotation of the impeller a co-rotating, concentric liquid ring. This completes together with the rotor blades, the gas volumes in the chambers. Due to the eccentricity of the rotor, the blades in the upper area completely submerge in the liquid ring, so that the chamber volume is filled with operating fluid. During the rotation, the liquid ring lifts off the impeller hub and forms a crescent-shaped space. The gaseous fluid to be delivered is sucked into the working space by the control disk openings arranged on the end faces of the impeller. Just before the gas-filled chamber volume reaches its maximum, the suction slot ends, and the chamber is sealed by the control discs, the impeller blades, and the fluid. Then the liquid ring migrates back to the hub and compresses the gas like a piston. As soon as the pressure slot openings are reached, the compressed gas is expelled.

The operating fluid has to fulfill in liquid ring vacuum pumps above all three functions, namely, first, the function of a moving piston with the Working cycles sucking, compressing and pushing out, secondly the sealing function for sealing the pump chambers against each other and thirdly the absorption of the heat of compression.

To dissipate the heat of compression, a portion of the operating fluid is constantly discharged through the pressure slot, wherein the same amount of fresh liquid is supplied via a fluid channel in the shaft hub of the pump. Due to this permanent recooling, a constant temperature of the operating fluid is achieved.

Basically, the vapor pressure of the working fluid, as known, limits the lowest suction level to be achieved in the intake manifold of the pump. If the suction pressure drops to a value equal to or close to the vapor pressure of the liquid, it cavitates and thus a complete power loss of the pump.

In most applications, water is used as the ring liquid. The advantage here is the high specific heat capacity, the constant availability, the environmental compatibility and finally the price.

The disadvantage, however, is the risk of corrosion in ferritic materials and the limitation of the range of application to the rough vacuum up to about 50 mbar.

Special applications also use oils that have a lower vapor pressure. However, such oils lead to contamination of the pumped medium and pose an environmental risk. Also known is the use of chemicals as a working fluid, for example, concentrated sulfuric acid for chlorine gas compression.

However, these applications require increased safety measures as well as additional equipment such as oil separators, etc. In all cases known hitherto, however, the field of application of liquid ring vacuum pumps remains limited to the rough vacuum.

Here, the invention provides a remedy by extending the range of application of the liquid ring vacuum pumps in the fine vacuum range due to the inventively provided use of ionic liquids. Since such ionic fluids have no appreciable vapor pressure, no cavitation occurs, so that there is no limitation of the suction pressure down. Furthermore, ionic fluids have very good lubricating properties and thus enable a shaft seal adapted to the fine vacuum. In contrast to the use of oil, there is no contamination of the delivery fluid.

Due to the inventively provided use of ionic liquids in process machines, in particular in liquid ring vacuum pumps, therefore their range of application is expanded into the fine vacuum range. Liquid ring vacuum pumps are thus entering a field of application previously covered by rotary and gate valves, Roots pumps or steam jet pumps. However, these have the disadvantage that the necessary oil lubrication of the impeller in the housing leads to a contamination of the pumped medium and that the removal of the heat of compression can be realized only expensive apparatus.

It can therefore liquid ring vacuum pumps in the now possible An- range of fine vacuum (10 ^"3 -10 ^{" 1} mbar) their pump immanent advantages, such as highest reliability, quasi isothermal compression and freedom from oil in the compression process play, and they open up in this way completely new litigation and uses.

The inventively used as operating liquid ionic liquids are compounds which are composed of cations and anions, wherein the cation used

a quaternary ammonium cation of the general formula

[NR ¹ R ² R ³ R] ⁺ , or a phosphonium cation of the general formula

[PR ¹ R ² R ³ R] ⁺ , or an imidazolium cation of the general formula

group, wherein the imidazole-Kem may be substituted with at least one group selected from d-Cβ-alkyl, CrCβ-alkoxy, CrCβ-aminoalkyl, C ₅ - C ₂ -aryl or C ₅ -C ₂ Aryl-C ₁ -C ₆ -alkyl groups,

- Pyridinium cations of the general formula

wherein the pyridin-Kem may be substituted with at least one group selected from -C ₆ alkyl, -C ₆ alkoxy, C ₆ aminoalkyl, C ₅ - - Pyrazolium cations of the general formula

wherein the pyrazole core may be substituted with at least one group selected from -C ₆ alkyl, -C ₆ alkoxy, C ₆ aminoalkyl, C ₅ -

and triazolium cations of the general formula wherein the triazole nucleus may be substituted with at least one group selected from -C ₆ alkyl, -C ₆ alkoxy, C ₆ aminoalkyl, C ₅ - C ₂ -aryl or C ₅ -C _2- aryl-C ₁ -C ₆ -alkyl groups,

represents

and the radicals R ¹ , R ² , R ^{3 are} independently selected from the group consisting of - hydrogen;

- linear or branched, saturated or unsaturated, aliphatic or alicyclic alkyl groups having 1 to 20 carbon atoms;

Heteroaryl, heteroarylCrCβ-alkyl groups having 3 to 8 carbon atoms in the heteroaryl radical and at least one heteroatom selected from N, O and S which may be substituted by at least one group selected from C 1 -C 6 -alkyl groups and / or halogen atoms;

- Aryl, aryl-CrCβ-alkyl groups having 5 to 12 carbon atoms in the aryl radical, which may be optionally substituted with at least one d-Cβ-alkyl groups and / or a halogen atom;

and the remainder R is selected

- Heteroaryl-CrCβ-alkyl groups having 3 to 8 carbon atoms in the aryl radical and at least one heteroatom selected from N, O and S, which may be substituted by at least one d-Cβ-alkyl groups and / or halogen atoms; Aryl-CrCβ-alkyl groups having 5 to 12 carbon atoms in the aryl radical, which may be optionally substituted by at least one d-Cβ-alkyl group and / or a halogen atom,

and wherein the anion of the ionic liquid used is an anion of the group [PF ₆ ] -, [BF ₄ ] -, [CF ₃ CO ₂ ] -, [CF ₃ SO ₃ ] -, [(CF ₃ SO ₂ J ₂ N] -, [(CF ₃ SO ₂₎ (CF ₃ COO) N] -, [R ⁴ - SO _3] ^"[R ⁴ -O-SO _^3]" [R ⁴ COO] ^", Cr, ^Br" , I ^" , [NO ₃ ] ^" , [N (CN) ₂ ] ^" , [HSO ₄ ] ^' or [R ⁴ R ⁵ PO ₄ ] ^" and the radicals R ⁴ and R ^{5 are} independently selected from the group consisting of - hydrogen;

- Heteroaryl, heteroaryl-Ci-C ₆ alkyl groups having 3 to 8 carbon atoms in the heteroaryl radical and at least one heteroatom selected from N, O and S, which is substituted with at least one group selected from d-Cβ-alkyl groups and / or halogen atoms could be;

- Aryl, aryl-CrCβ-alkyl groups having 5 to 12 carbon atoms in the aryl radical, which may be substituted by at least one d-Cβ-alkyl group and / or a halogen atom.

By way of example, mention may be made below of some preferred ionic liquids which have the properties mentioned for certain desired uses:

1) 1-butyl-3-methylimidazolium tetrafluoroborate: water-miscible, stable

> 250 ° C, chemically inert, positive lubricating properties;

2) 1-butyl-3-methylimidazolium hexafluorophosphate: immiscible with water, stable up to 25O ⁰ C, chemically inert, positive lubricating properties; 3) 1-ethyl-3-methylimidazoliumethylsulfat: miscible with water, physiologically harmless (detected), stable up to 25O ⁰ C, chemically inert, available on a ton scale;

4) 1-ethyl-3-methylimidazoliumbistrifluoromethanesulfonylamide: not miscible with water, stable> 300 ° C, chemically inert, positive lubricating properties;

5) 3-methyl-1-ethylpyridiniumethylsulfat: miscible with water, stable up to 25O ⁰ C, chemically inert;

6) Butyltrimethylphosphoniumdimethylphosphat: miscible, stable, chemically inert with water to 200 ⁰ C.

Claims

claims:

1. Gas conveying machine, characterized in that it comprises an ionic liquid as a lubricating or blocking fluid.

2. Hydraulic diaphragm pump, characterized in that it comprises an ionic liquid as hydraulic fluid.

3. liquid ring vacuum pump, characterized in that it comprises an ionic liquid as the ring liquid.

4. piston engine, characterized in that it is designed with a piston oscillating in a cylinder in the form of a liquid piston or an upstream liquid original piston, which consists of an ionic liquid and due to its oscillating movement, a gas or a non-mixable liquid of low density or a liquid promotes high density.

5. Device according to one of the preceding claims, characterized in that the intended as operating liquid ionic liquid is composed of cations and anions, wherein

the cation used

a quaternary ammonium cation of the general formula

[NR ¹ R ² R ³ R] ⁺ , or a phosphonium cation of the general formula [PR ¹ R ² R ³ R] ⁺ , or an imidazolium cation of the general formula group, wherein the imidazole nucleus may be substituted with at least one group selected from -C ₆ alkyl, -C ₆ alkoxy, C ₆ aminoalkyl, C ₅ - C ₂ -aryl or C ₅ -C ₂ -aryl-C ₁ -C ₆ -alkyl groups,

Pyridinium cations of the general formula

wherein the pyridine nucleus may be substituted with at least one group selected from -C ₆ alkyl, -C ₆ alkoxy, C ₆ aminoalkyl, C ₅ -

Ci ₂ -aryl or C ₅ -C ₂ aryl-Ci-C ₆ alkyl groups, pyrazolium cations of the general formula

wherein the pyrazole nucleus may be substituted with at least one group selected from C 1 -C 6 -alkyl, C 1 -C 6 -alkoxy, C 1 -C 6 -aminoalkyl, C ₅ -

Ci ₂ -aryl or C ₅ -C ₂ aryl-Ci-C ₆ alkyl groups,

and triazolium cations of the general formula

wherein the triazole core may be substituted with at least one group selected from d-Cβ-alkyl, CrCβ-alkoxy, CrCβ-aminoalkyl, C ₅ - C ₂ -aryl or C ₅ -C ₂ -aryl -Ci-C ₆ -alkyl groups, represents

Heteroaryl, heteroarylCrC ₆ -alkyl groups having 3 to 8 carbon atoms in the heteroaryl radical and at least one heteroatom selected from N, O and S which may be substituted by at least one group selected from C 1 -C ₆ -alkyl groups and / or halogen atoms ;

and the remainder R is selected

- heteroaryl-CrCβ-alkyl groups having 3 to 8 carbon atoms in the aryl radical and at least one heteroatom selected from N, O and S, which may be substituted with at least one CrC ₆ alkyl groups and / or halogen atoms;

ArylCrCβ-alkyl groups having 5 to 12 carbon atoms in the aryl radical, which may optionally be substituted by at least one C 1 -C 6 -alkyl group and / or a halogenogenic atom,

- and wherein the anion of the ionic liquid used is an anion of the group [PF ₆ ] ^" , [BF ₄ ] ^" , [CF ₃ CO ₂ ] -, [CF ₃ SO ₃ ] -, [(CF ₃ SO ₂ J ₂ N ] -, [(CF ₃ SO ₂ ) (CF ₃ COO) N] -, [R ⁴ -SO ₃ ] -, [R ⁴ -O-SO ₃ ] -, [R ⁴ -COO] -, Cl ^" , Br ^" , I ^" , [NO ₃ ] ^" , [N (CN) ₂ ] ^" , [HSO ₄ ] ^" or [R ⁴ R ⁵ PO ₄ ] ^" and the radicals R ⁴ and R ^{5 are} independently selected from consisting of the group - hydrogen;

- Heteroaryl, heteroaryl-C1-C6-alkyl groups having 3 to 8 carbon atoms in the heteroaryl radical and at least one heteroatom selected from N, O and S, which are substituted with at least one group selected from C1-C6-alkyl groups and / or halogen atoms can;

- Aryl, aryl-C1-C6-alkyl groups having 5 to 12 carbon atoms in the aryl radical, which may be substituted by at least one C1-C6-alkyl group and / or a halogen atom.

6. The device according to claim 5, characterized in that the ionic liquid used as the operating fluid is selected from the group consisting of 1-butyl-3-methylimidazoliumtetrafluoroborat, 1-butyl-3-methylimid- azoliumhexafluorophosphat, 1-ethyl-3-methylimidazoliumethylsulfat, 1-ethyl-3-methylimidazoliumbistrifluoromethanesulfonylamide, 3-methyl-1-ethylpyridinium ethylsulfate and butyltrimethylphosphonium dimethyl phosphate or mixtures thereof.

7. Use of operating fluids in gas carriers, hydraulic diaphragm pumps, liquid ring vacuum pumps or reciprocating engines, characterized in that an ionic liquid is used as the operating fluid, in particular as a lubricating fluid, barrier fluid, Abdichtflüssigkeit, pressure transfer fluid.

8. Use according to claim 7, characterized in that the ionic liquid is used in gas conveying machines as lubricating and sealing liquid.

9. Use according to claim 7, characterized in that the ionic liquid is used in hydraulic diaphragm pumps as hydraulic fluid.

10. Use according to claim 7, characterized in that the ionic liquid is used in liquid ring vacuum pumps as a ring liquid for expanding the working area in the fine vacuum.

11. Use according to claim 7, characterized in that the ionic liquid is used in piston machines as in a cylinder oscillating liquid piston, which is able to promote a gas or a non-miscible liquid of low density or a liquid large density te due to its oscillating movement.

12. A method of operating the device defined in claim 1 to 6 using ionic liquids as the operating medium.