A METHOD FOR SHIFTING AN AZEOTROPE

TECHNICAL FIELD

The present invention concerns a method for shifting an azeotrope. More specifically, the present invention concerns a method for shifting an azeotrope of a pressure sensitive azeotropic mixture comprising vapour or liquid. BACKGROUND

Distillation is one of the most important unit operations in chemistry for separation, purification and/or recovery of chemicals. The technique is based on the exploiting of differences of boiling points of the components of a mixture. In industry, distillation is widely used in various fields such as in the manufacture of crude oil, pharmaceuticals, specialty chemicals and in solvent recovery.

However, distillation is frequently associated with disadvantages such as high energy consumption, formation of so-called azeotropic mixtures, necessity for use of high temperatures/pressures and/or sophisticated equipment. In particular, the formation of azeotropic mixtures is an obstacle to obtaining pure components from a distillation process.

An azeotrope or azeotropic mixture is a mixture of at least two components, such as two liquid components, where at a given pressure and temperature the vapour has the same composition as the liquid and the mixture boiling point is different from the boiling point of the mixture components.

As a result of the formation of an azeotrope, boiling of the mixture provides vapour that has the same composition as the original mixture, i.e. the composition is not changed upon boiling. Therefore, azeotropes are also denoted constant boiling mixtures.

Azeotropes may be minimum-boiling azeotropes or maximum-boiling azeotropes. While minimum-boiling azeotropes exhibit an azeotrope boiling point that is lower than the boiling points of the individual components of the mixture, maximum-boiling azeotropes exhibit an azeotrope boiling point that is higher than the boiling points of the individual components of the mixture. Most of the known azeotropes are minimum-boiling azeotropes.

Further, an azeotrope may be homogenous or heterogeneous. In a homogeneous azeotrope, the vapour phase coexists with a liquid phase at an equilibrium temperature. In a heterogeneous azeotrope, the vapour phase coexists with two or more liquid phases at an equilibrium temperature.

Azeotropic distillation is an important technique for breaking an azeotrope in distillation. Frequently, this technique involves adding a further component to the mixture- a so-called entrainer- whereby the equilibrium of the mixture is shifted leading to breakage of the azeotrope. However, a disadvantage associated with the use of an entrainer may be that the entrainer may contaminate the separated products.

Azeotropic distillation may also involve so-called pressure-swing distillation, which involves changing the pressure at which distillation is performed. Changing the pressure will impact the vapour-liquid equilibrium composition of the azeotropic mixture so that it is moved to a new value thereby facilitating separation. This technique commonly involves transferring the mixture into a further column operating at a pressure different from the pressure to which the mixture was originally subjected, i.e. an additional operating step is required. A disadvantage is that often high temperatures and pressures are required. US 5,061 ,349 discloses a method of isolating trioxane from aqueous solutions by distillation. In the method, a mixture of trioxane, water and optionally formaldehyde and/or acid is distilled in the presence of an inert gas involving cooling to a temperature of 58° to 64° C leading to isolation of trioxane concentrate with a trioxane concentration which is greater than that of the azeotropic mixture. However, the distillation requires two cooling steps and considerable energy input and the cooling is described as being limited to 58° to 64° C.

AIChE Journal, 2016, Vol. 62, No.4, pages 1 192-1 199 discloses separation of azeotropic mixtures using air microbubbles generated by fluidic oscillation. Data are shown for an ethanol-water azeotrope. It is stated that microbubble distillation is a new technology that is still being developed.

SUMMARY

There is provided a method for shifting an azeotrope of a pressure sensitive azeotropic mixture comprising vapour,

said azeotrope existing at a first pressure,

said vapour comprising a dew point pressure,

at a maximum total pressure comprising said dew point pressure,

said method comprising the steps of:

- providing a mixture comprising vapour,

- selecting vapour-liquid equilibrium data applicable for said mixture comprising vapour,

- selecting a desired vapour concentration of at least one further mixture using said vapour-liquid equilibrium data so that the concentration of said further mixture differs from that of said pressure sensitive azeotropic mixture at said first pressure,

- cooling said mixture comprising vapour to at least one temperature to provide said at least one further mixture comprising vapour and liquid,

wherein:

said method steps take place within substantially the same volume, and

said first pressure is different from said dew point pressure.

Further, there is provided a method for shifting an azeotrope of a pressure sensitive azeotropic mixture comprising liquid

said azeotrope existing at a first pressure,

said liquid comprising a bubble point pressure,

at a maximum total pressure comprising said bubble point pressure,

said method comprising the steps of:

- providing a mixture comprising liquid,

- selecting vapour-liquid equilibrium data applicable for said mixture comprising liquid, - selecting a desired liquid concentration of at least one further mixture using said vapour- liquid equilibrium data so that the concentration of said further mixture differs from that of said pressure sensitive azeotropic mixture at said first pressure,

- heating said mixture comprising liquid to at least one temperature to provide said at least one further mixture comprising liquid and vapour, wherein:

said method steps take place within substantially the same volume, and

said first pressure is different from said bubble point pressure. There is also provided a method for operating a device selected from at least one of the following:

distillation device such as a continuously or batchwise operating distillation column, a divided wall distillation column or a superfractionator,

pipe,

heat exchanger,

refrigeration device using a refrigerant having a pressure sensitive azeotrope,

said method comprising

at least one of the method steps as described herein.. BRIEF DESCRIPTION OF THE DRAWINGS

Figure 1 shows a distillation apparatus as known in the art.

Figure2 shows a distillation equipment that may be used for performing the method described herein.

Figure 2 shows vapour-liquid equilibrium data for a minimum boiling azeotropic mixture at two different pressures.

Figure 3 shows vapour-liquid equilibrium data for a maximum boiling azeotropic mixture at two different pressures.

DETAILED DESCRIPTION

It is an object of the present disclosure to overcome or at least mitigate some of the disadvantages associated with known techniques for moving or breaking azeotropes.

Accordingly, there is provided a method for shifting an azeotrope of a pressure sensitive azeotropic mixture comprising vapour,

said azeotrope existing at a first pressure,

said vapour comprising a dew point pressure,

at a maximum total pressure comprising said dew point pressure,

said method comprising the steps of:

- providing a mixture comprising vapour, - selecting vapour-liquid equilibrium data applicable for said mixture comprising vapour,

- selecting a desired vapour concentration of at least one further mixture using said vapour-liquid equilibrium data so that the concentration of said further mixture differs from that of said pressure sensitive azeotropic mixture at said first pressure,

- cooling said mixture comprising vapour to at least one temperature to provide said at least one further mixture comprising vapour and liquid,

wherein:

said method steps take place within substantially the same volume, and

said first pressure is different from said dew point pressure.

As used herein, the expression "dew point pressure" is understood to mean the saturation pressure of a vapour such as a vapour having a specified composition at a specified temperature. The partial pressure of each individual component equals its vapour pressure at the specified temperature.

There is also provided a method as described herein, wherein:

the pressure sensitive azeotropic mixture comprises or consists of vapour, and the mixture comprising vapour has a concentration equal to or lower than an azeotropic concentration of said mixture. Thus, the mixture being subjected to the method may be a pressure sensitive azeotropic mixture comprising or consisting of vapour. Alternatively, the mixture being subjected to the method may be a pressure sensitive non-azeotropic mixture comprising or consisting of vapour, said non-azeotropic mixture having a lower concentration than an azeotropic concentration of said mixture. The azeotrope exists at a first pressure as described herein.

The method described herein may comprise the steps of:

- providing a mixture comprising vapour having a concentration equal to, lower than or higher than the azeotropic concentration of said mixture,

- selecting vapour-liquid equilibrium data applicable for said mixture comprising vapour, - selecting a desired vapour concentration of at least one further mixture comprising vapour and liquid using said vapour-liquid equilibrium data so that the concentration in the vapour of said further mixture exceeds the azeotropic concentration in the vapour of the pressure sensitive azeotropic mixture at said first pressure,

- cooling said mixture comprising vapour to at least one temperature to provide said at least one further mixture comprising vapour and liquid. Thus, there is provided a method for shifting an azeotrope of a pressure sensitive azeotropic mixture comprising or consisting of vapour,

said azeotrope existing at a first pressure,

said vapour comprising a dew point pressure,

at a maximum total pressure comprising said dew point pressure,

said method comprising the steps of:

- providing a mixture comprising vapour having a concentration equal to or lower than the azeotropic concentration of said mixture,

- selecting vapour-liquid equilibrium data applicable for said mixture comprising vapour,

- selecting a desired vapour concentration of at least one further mixture comprising vapour and liquid using said vapour-liquid equilibrium data so that the concentration in the vapour of said further mixture exceeds the azeotropic concentration in the vapour of the pressure sensitive azeotropic mixture at said first pressure,

- cooling said mixture comprising vapour to at least one temperature to provide said at least one further mixture comprising vapour and liquid

wherein:

said method steps take place within substantially the same volume, and

said first pressure is different from said dew point pressure.

The mixture comprising vapour of the method described herein may have a concentration that is equal to the azeotropic concentration of said mixture, i.e. it may be an azeotropic mixture comprising vapour such as a pressure sensitive azeotropic mixture comprising vapour.

The dew point pressure of the method described herein may be a single dew point pressure of a substantially single dew point pressure. The mixture comprising vapour described herein may comprise one or more of the following substances: 2-ethylhexanol, acetic acid, acetone, acrylic acid, acrylonitrile, ammonia, benzene, bisphenol A, butadiene, butanediol, caprolactam, cumene, cyclohexane, dimethyl terephtalate, ethanol, ethyl acetate, ethylbenzene, ethylene dichloride, formaldehyde, isopropanol, maleic anhydride, methanol, methyl-ethyl-ketone (MEK), methyl methacrylate, methyl tertiary butyl ether, methylene di-p-phenylene isocyanate, ortoxylene, paraxylene, perchloroethylene, styrene.

Additionally or alternatively, the mixture comprising vapour described herein may consist of one of the following binary combinations of substances: 1-butanol/n-butyl acetate, 1- butanol/n-octane, 1-propanol/cyclohexane, 1 ,2-butanediol/ethylene glycol, acetic acid/toluene, acetone/methanol, acetonitrile/water, benzene/1 -propanol,

benzene/cyclohexane, benzene/ethanol, benzene/isopropanol, benzene/methanol, benzene/methyl ethyl ketone (MEK), benzene/tert-butyl alcohol, chloroform/methanol, dimethyl carbonate/ethanol, diisopropyl ether (DIPE)/isopropyl alcohol (IPA), dimethyl carbonate/methanol, ethanol/1 ,4-dioxane, ethanol/ethyl acetate, ethanol/n-heptane, ethanol/water, ethyl acetate/methanol, n-heptane/isobutyl alcohol, isopropyl alcohol (IPA)/methyl ethyl ketone (MEK), methanol/methyl acetate, methanol/methyl ethyl ketone (MEK), methanol/methyl tert-butyl ether (MTBE), methanol/pentane,

methanol/tetrahydrofuran, 1-propanol/toluene, pyridine/toluene or tetrahydrofuran/water.

In an example, the mixture comprising vapour described herein may consist of one or more of the following binary combinations of substances: acetone/methanol, diisopropyl ether (DIPE)/isopropyl alcohol (IPA), ethanol/water, isopropyl alcohol (IPA)/methyl ethyl ketone (MEK) or methanol/methyl tert-butyl ether (MTBE).

The pressure sensitive azeotrope described herein may be a ternary azeotrope. For instance, the pressure sensitive azeotropic mixture described herein may consist of a ternary combination of methanol, methyl acetate and chloroform.

The desired vapour concentration of the method described herein may consist of substantially pure substance. Alternatively, it may consist of a substantially pure binary mixture of substances. The method described herein may further comprise a step of:

- separating the liquid and the vapour of said further mixture from each other. The liquid may be zeotropic.

Further, there is provided a method for shifting an azeotrope of a pressure sensitive azeotropic mixture comprising liquid said azeotrope existing at a first pressure,

said liquid comprising a bubble point pressure,

at a maximum total pressure comprising said bubble point pressure,

said method comprising the steps of:

- providing a mixture comprising liquid,

- selecting vapour-liquid equilibrium data applicable for said mixture comprising liquid,

- selecting a desired liquid concentration of at least one further mixture using said vapour- liquid equilibrium data so that the concentration of said further mixture differs from that of said pressure sensitive azeotropic mixture at said first pressure,

- heating said mixture comprising liquid to at least one temperature to provide said at least one further mixture comprising liquid and vapour,

wherein:

said method steps take place within substantially the same volume, and

said first pressure is different from said bubble point pressure.

As used herein, the expression "bubble point pressure" is understood to mean the saturation pressure of a liquid such as a liquid having a specified composition and a specified temperature.

There is also provided a method as described herein, wherein:

the pressure sensitive azeotropic mixture comprises or consists of liquid, and

the mixture comprising liquid has a concentration equal to or lower than an azeotropic concentration of said mixture. Thus, the mixture being subjected to the method may be a pressure sensitive azeotropic mixture comprising or consisting of liquid. Alternatively, the mixture being subjected to the method may be a pressure sensitive non-azeotropic mixture comprising or consisting of liquid, said non-azeotropic mixture having a lower concentration than an azeotropic concentration of said mixture.

Further, there is provided a method as described herein, wherein:

said method comprises the steps of:

-providing a mixture comprising liquid having a concentration equal to or lower than the azeotropic concentration of said mixture,

- selecting vapour -liquid equilibrium data applicable for said mixture comprising liquid; -selecting a desired liquid concentration of at least one further mixture comprising liquid using said vapour-liquid data so that the concentration in the liquid of said further mixture exceeds the azeotropic concentration of the pressure sensitive azeotropic mixture at said first pressure,

-heating said mixture comprising liquid to at least one temperature to provide said at least one further mixture comprising liquid and vapour.

Thus, there is provided a method for shifting an azeotrope of a pressure sensitive azeotropic mixture comprising liquid

said azeotrope existing at a first pressure,

said liquid comprising a bubble point pressure,

at a maximum total pressure comprising said bubble point pressure,

said method comprising the steps of:

-providing a mixture comprising liquid having a concentration equal to or lower than the azeotropic concentration of said mixture,

- selecting vapour -liquid equilibrium data applicable for said mixture comprising liquid; -selecting a desired liquid concentration of at least one further mixture comprising liquid using said vapour-liquid data so that the concentration in the liquid of said further mixture exceeds the azeotropic concentration of the pressure sensitive azeotropic mixture at said first pressure,

-heating said mixture comprising liquid to at least one temperature to provide said at least one further mixture comprising liquid and vapour,

wherein:

said method steps take place within substantially the same volume, and

said first pressure is different from said bubble point pressure.

The mixture comprising liquid of the method described herein may have a concentration equal to the azeotropic concentration of said mixture, i.e. it may be an azeotropic mixture comprising liquid such as a pressure sensitive azeotropic mixture comprising liquid.

The bubble point pressure of the method described herein may be a single bubble point pressure.

The mixture comprising liquid of the method described herein may comprise one of the following binary combinations of substances: acetone/chloroform, acetophenone/phenol, ethylenediamine/water, formic acid/water or hydrochloric acid/water, N,N- dimethylacetamide (DMAC)/water or hydrazine/water. The method described herein may further comprise a step of:

-separating the vapour and the liquid of said at least one further mixture from each other The vapour may be zeotropic. The vapour-liquid equilibrium data described herein may be data provided by DDBST GmbH.

The at least one temperature described herein may comprise three or more temperatures. The azeotropic mixture of the method described herein may be a binary mixture or a ternary mixture.

The pressure sensitive azeotropic mixture described herein may be a minimum boiling azeotrope or a maximum boiling azeotrope.

There is also provided a method as described herein, wherein:

said method is performed in an atmosphere of a non-condensable gas. such as air, oxygen, nitrogen, carbon dioxide, a noble gas such as e.g. argon, a hydrocarbon such as methane, ethane, propane, and any combination of the foregoing gases. The gas may be superheated in a temperature range for performing said method.

The pressure sensitive azeotrope of the method described herein may not comprise or consist of trioxane, water, optionally formaldehyde and optionally acid such as sulphuric acid and/or phosphoric acid. Addditionally or alternatively, said method may be not performed at atmospheric pressure, sub-atmospheric pressure and/or super-atmospheric pressure.

The method described herein is free from microbubble distillation such as microbubble distillation as described above. The method described herein, may be a method for obtaining a zeotropic mixture.

The present disclosure also provides a method for operating a device selected from at least one of the following:

distillation device such as a continuously or batchwise operating distillation column, a divided wall distillation column or a superfractionator, pipe,

heat exchanger,

refrigeration device using a refrigerant having a pressure sensitive azeotrope, said method comprising comprising at least one of the method steps of the method described herein .

Figure 1 shows a distillation apparatus that may be used for performing traditional atmospheric dew pressure distillation. 1 is a temperature control unit. 2 is a reboiler unit such as a flask, which is provided with a temperature control unit 2a such as a

thermometer. 3 is one to two vertically mounted reflux condensers generating reflux condensate for return to the reboiler unit 2. The two reflux condensers 3 are filled with packing material 3b such as crushed borosilicate glass and sliced PTFE tubing and optionally, 3 is provided with insulation 3a. 4 is two angled reflux condensers without any packing material. 5 is a distillate condenser generating distillate for a distillate tank 6. 7 is a back pressure condenser, whose purpose is to condense out any remaining vapour into a condensate 7a and to open up the distillate apparatus to an atmospheric back pressure 8. Cooling to the vertically mounted reflux condensers 3 and to the angled reflux condensers 4 either by surrounding air, or by a cooling water flow from a cooling water circuit 9. The cooling water circuit 9 consists of a water pump 9a, water hose 9b, angled reflux condenser jackets 4a connected to vertical reflux condenser jackets 3c, which continue through a long hose 9c capable of dissipating heat to the ambient air. Finally, the hose 9c returns to the water pump 9a. When in use, said cooling water flows through circuit 9 n a counter-current fashion compared to the vapours coming from reboiler unit 2. The vapour flowing through the reflux condensers 3 and 4 and subsequently through the distillate condenser 5 splits the vapour into a high temperature reflux condensate and a low temperature distillate, thereby creating separation between the high temperature boiling and low temperature boiling substances in the mixture being distilled.

Figure 2 shows a distillation apparatus that may be used for performing the method of the present disclosure. 1 is a reboiler unit such as a flask, which is provided with a reboiler jacket 1a for circulating cooling liquid, a temperature measurement unit 1 b such as a thermometer and a reboiler inert gas injection point 1 c, such as e.g. a stiff hose. A reflux manifold 2 is optionally mounted on reboiler 1. A manifold 2 allows the use of two to three parallell condenser lines to increase the capacity of the distillation apparatus. When no manifold is mounted, a single line of condensers are used. Vertical reflux condensers 3a are mounted on reboiler 1 (one single condenser line) or on the reflux manifold 2 (two or three condenser lines). Due to limited vertical space in the fume hood where the distillation experiments of the present disclosure were carried out, the next condensers, angled reflux condensers 3b are connected to the vertical reflux condensers 3a. The last one of these is called a last angled reflux condenser 3c. This last angled reflux condenser 3c is connected to a distillate condenser 4. 4 is subsequently connected either to a distillate merger manifold 5 (two or three condenser lines) or directly to a distillate tank 6. Said distillate tank 6 is equipped with a distillate tank jacket 6a and a temperature control unit 6b such as a thermometer. Furthermore, when needed to adjust temperatures to which reboiler liquid and inert gas/vapour mixtures are subjected, inert gas hose insulation 13a, glassware insulation 13b and/or cooling liquid hose insulation 13c is applied.

The distillation apparatus of the present disclosure uses a cooling machine 12 to cool a circulating cooling liquid (polydimethylsiloxane). The cooling machine 12 pumps said circulating cooling liquid to the distillate tank jacket 6a, subsequently via a hose to a distillate condenser jacket 4a. 4a in turn is connected via a hose 4b to the jacket of the last angled reflux condenser 3c. As hose 4b is exposed to and heated by ambient room air, the length of hose 4b is used to create a ΔΤ between distillate condenser 4 and the last angled reflux condenser 3c. The temperature drop ΔΤ increases the distillate production of the distillate condenser 4. The jacket of 3c is subsequently connected to the jackets of the other angled reflux condensers 3b. Said jacket of 3b is connected to the jacket of the vertical reflux condenser 3a. A hose 13c connects the jacket of the vertical reflux condensers 3a to the reboiler jacket 1 a. A longer hose 13c creates a bigger ΔΤ between the reboiler 1 and the vertical reflux condensers 3a, which in turn increases the reflux production of the reflux condensers 3a, 3b and 3c. In some of the experiments, the circulating cooling liquid bypasses the reboiler jacket 1 a and instead returns directly from the jacket of the vertical reflux condensers 3a to the cooling machine 12.

One or two compressors 8 compresses inert gas for injection into the liquid mixture in the reboiler 1 , via the reboiler inert gas injection point 1 c. The injection inert gas is lean in vapour, as it originates from the distillate condenser 4, which is very cold and has the lowest dew pressure of the distillation apparatus, and some makeup inert gas from an inert gas supply 9b. The temperature in the reboiler liquid is the highest temperature encountered by inert gas/vapour in the distillation apparatus. Thus, the bubble pressure in the reboiler liquid is higher than the dew pressure of the injected inert gas/vapour.

Evaporation occurs giving vapour with a composition corresponding to applicable vapour- liquid equilibrium data for the reboiler liquid composition at the reboiler's 1 bubble pressure. A mixture of the injected inert gas and vapour from evaporated reboiler liquid now continues into the reflux condensers 3a, 3b and 3c. The inert gas/vapour stream temperature decreases and reflux condensate rich in the high temperature component trickles back into the reboiler liquid. The remaining colder inert gas/vapour stream now enters the distillate condenser 4. As the distillate condenser further cools the inert gas/vapour mixture, distillate with a composition according to applicable vapour-liquid equilibrium data for the vapour composition and for the vapour dew point pressure condensates out. A very cold inert gas/vapour mixture now passes through the distillate tank 6 and enters a suction hose 6c leading to the compressor. On its way through the suction hose 6c, fresh inert gas from an inert gas source 9b is mixed with the inert gas/vapour. A gas tube pressure gauge (for helium supplied) 9a or a height difference Ah (for nitrogen and argon) between a distilled water surface in an erlenmeyer flask 9a and the corresponding water surface inside an inert gas hose submerged into said erlenmeyer flask 9a were used to adjust the flow of fresh inert gas entering into the suction hose 6c. The compressor 8 increases the pressure in the inert gas/vapour mixture from the suction hose 6c. In order to regulate the flow through the inert gas injection point 1c, a

recirculation hose 10 having a throttle valve recirculated inert gas/vapour from the pressure side to the suction side of the compressor 8. As the inert gas/vapour

temperature may be very cold, even room temperature air can heat the inert gas/vapour significantly. A household refrigerator/freezer can be used to cool the recirculation hose 10 and the hose on the outlet pressure side of the compressor 8.

It will be appreciated that the reflux condenser in Figure 1 may be connected to each other. It will be appreciated that the reflux condenser in Figure 2 may be connected to each other.

Figure 3 is a vapour-liquid equilibrium graph for a minimum boiling azeotrope at pressures P1 and P2, respectively. Pressure P1 is higher than pressure P2. 1 shows the dew point curve. 2 shows the bubble point curve. The azeotrope is indicated with A. L is a line going through the azeotropes at pressures P1 and P2, respectively. It can be seen that change of the pressure leads to a change in the azeotropic composition.

Figure 4 is a vapour-liquid equilibrium graph for a maximum boiling azeotrope at pressures P1 and P2, respectively. Pressure P1 is higher than pressure P2. 1 shows the dew point curve. 2 shows the bubble point curve. The azeotrope is indicated with A. L is a line going through the azeotropes at pressures P1 and P2, respectively. It can be seen that change of the pressure leads to a change in the azeotropic composition. It will be appreciated that the invention is not limited by the embodiments described above, and further modifications of the invention within the scope of the claims would be apparent to a skilled person.

The present disclosure also provides for a flash tank, for example one used in a refrigeration cycle. In this flash tank, a pressure sensitive azeotropic refrigerant is flashed into vapour and liquid. For maximum-boiling azeotropic refrigerants, the liquid will be of azeotropic composition. For minimum-boiling azeotropic refrigerants, the vapour will be of azeotropic composition. Such a flash tank may be used to adjust the composition and hence the properties of the refrigerant during operation of said refrigeration cycle.

The disclosure is further illustrated by the following non-limitative Examples

EXAMPLES

General

Operating total pressure: 1 atm

Azeotropic composition^ atm): 66 to 73 mole%, corresponding to

82 to 86 mass% acetonitrile according to DDBST GmbH

Glassware main supplier: Carl Roth

Cooling: Lauda Integral XT 280 or recirculating chiller Fryka DLK 402

Acetonitrile: >=99,95% (≤30 ppm H20), VWR Chemicals,

HiPerSolv Chromanorm, 83639.320

Water: Water, Ultrapure AGR, ArtNo LB.WATR-00A- 10K, (Teknolab Sorbent)

Inert gases: Helium, UN 1046, Mtrl.nr. 105000, AGA GAS AB

Argon 4.6 Premium 50L, AGA GAS AB

Composition analysis laboratory: Samples were analysed by:

(1)

Analytische Laboratorien, Prof. Dr. H. Malissa und G.Reuter GmbH, Lindlar/Germany

Nach DIN EN ISO/I EC 17025 und EN ISO 9001 :2008 durch die GAZ zertifiziertes pruflaboratorium. The Karl-Fischer H ₂ 0 standard deviation was reported to be 3%.

(2)

Q&Q Labs AB, BioVentureHub, 431 83

Molndal/SE

(Karl-Fischer H ₂ 0 analysis)

Abbreviations

CHN elemental analysis

DDBST GmbH Dortmund Data Bank Software and Separation Technology GmbH KF Karl Fischer

wt% per cent by weight

ACN acetonitrile

n.d. no data

ml milliliter(s)

wt% weight percent

N/A not applicable

Compressors used included Hailea ACO 500. Analytical methods included measurement of acetone concentration and I PA concentration, respectively. Traditional distillation

Traditional distillation, i.e. distillation at atmospheric dew pressure, was performed using an equipment as shown in Figure 1.

Example 1

An acetonitrile-water mixture containing 70 wt% of acetonitrile and 30 wt% of water , i.e. an acetonitrile-water mixture below the azeotropic composition at 1 atm was distilled at 1 atm in two steps. Hereinafter the distillation steps are called distillation experiment #1/2 and distillation experiment #2/2, respectively. It will be appreciated that distillation experiment #2/2 used the distillate from distillation experiment #1/2 as starting material. The distillate from the distillation experiment #2/2 was about 92 wt%, i.e. exceeded the azeotropic composition by about 6 mass%. The distillation was performed as indicated below. A glassware distillation setup with a circulating cooler as in fig 1 was used. The reboiler was filled with the substrate mixture, the glassware was flushed with nitrogen emptying it from air, a constant nitrogen external back pressure was maintained, the inert gas circulating compressor was started, the cooling machine temperatures for the first/final condenser were calibrated. Thereafter, the reboiler and nitrogen heating was slowly started and the first/final condenser temperatures was recalibrated.

During the second distillation step, all equipment in contact with the mixture was carefully insulated to keep the temperature low in order to achieve a high concentration of acetonitrile.

The first condenser helped condense out condensate rich in water and the final condenser condensed out vapour rich in acetonitrile. In the second distillation step, the dew pressure had been lowered so much that the azeotropic composition well exceeded the one for 1 atm.

During the experiments, once sufficient distillate quantities had been reached, these were bottled and stored in refrigerator and then transported in refrigerator to the analysis laboratory.

Distillation experiment #1/2

Compositions

Sample Name Composition

(mass% acetonitrile) (CHN+KF) Composition

(mass% acetonitrile) (Karl Fischer)

Starting mixture EXP#1/2 70,86 71 ,09

Distillate EXP#1/2 86,8 86,79

Bottoms liquid EXP#/2 6,39 6,38

Temperature Point of Measurement Temperature (oC)

Reboiler (round flask) 47,5 to 53,5

Before final condenser 25,5 to 32,4

After final condenser 18,2 to 22,8

Distillation #2/2

Sample Name Composition

(mass% acetonitrile) (CHN+KF) Composition

(mass% acetonitrile)

(Karl Fischer)

Starting mixture EXP#2/2

( "Distillate EXP#1/2") 86,8 86,79

Distillate EXP#2/2 91 ,42 91 ,46

Bottoms liquid EXP#/2 82,93 82,86

Temperature Point of Measurement Temperature (oC)

Reboiler (round flask) 1 ,6 to 5,4

Before final condenser 0,3 to 0,9

After final condenser 3,9 to 4,2

It was concluded that the distillate from the first distillation experiment #1/1 provided a substantially azeotropic mixture of acetonitrile and water. Further, it was concluded that the second distillation experiment #2/2 provided a mixture of acetonitrile and water with a higher content of acetonitrile than that of the starting material, i.e. the azeotrope had been shifted. Example 2

An acetonitrile-water mixture, 2615 g, containing 73 wt% of acetonitrile and 27 wt% of water, i.e. an acetonitrile-water mixture below the azeotropic composition at 1 atm was distilled in six distillation steps.

Hereinafter the distillation steps are called distillation experiment #1/6, #2/6, #3/6, #4/6, #5/6 and distillation experiment #6/6, respectively. It will be appreciated that a distillation experiment of a higher number used the distillate from the distillation of its previous number. Table X describes how much equipment was used in each experiment.

Furthermore, it contains volume, density and temperature data, as well as achieved compositions for distillates and bottom liquids.

Experiment #1 and #2 were carried out at atmospheric dew pressure (traditional distillation), while the remaining experiments used argon and lowered temperatures to distil at lower dew pressures.

Experiments #1 and #2 approximately reached the azeotropic composition at atmospheric dew pressure. Experiment #3, #4, #5 and #6 were carried out using argon as inert gas, instead of nitrogen as in Example 1. In experiment #3, small amounts (estimated to 1 - 2 ml) of distilled water from the pressure gauge erlenmeyer flask leaked into the suction hose and hence increased the bottom liquid/distillate water contents. Experiment #4 was carried out at a distillate tank temperature of -42°C and the distillate reached 96,2 mass% acetonitrile - well beyond the atmospheric dew pressure azeotropic composition of 86 mass% acetonitrile. After experiment #5, all starting liquid had distilled over to the distillate tank.

The distillate from the distillation experiment #6/6 was about 96,5 wt%, i.e. exceeded the azeotropic composition by about 10 mass%. The distillation thus obtained a distillate only 3,5 mass% from pure acetonitrile. Extrapolation in a graph representing the acetonitrile- water azeotropic composition as a function of the vapour contents of acetonitrile (source: DDBST GmbH) suggests that the acetonitrile-water azeotrope disappears and that the mixture could become zeotropic at distillation temperatures in the temperature region used in experiment #4. It was concluded that the azeotrope had been shifted. Table 1 shows experimental parameters as well as results obtained in the experiments. Table 1

Experiment No: #1/6 #2/6 #3/6 #4/6 #5/6 #6/6

Atm. dew pressure Yes Yes No No No No

Inert gas No No Argon Argon Argon Argon

T (set, cooling Ambient Ambient -5°C -83°C -83°C -83°C liquid) air air

T(Actual, cooling Ambient Ambient n.d. -63°C -45°C -45°C liquid) air air

T (Reboiler) Bp for Bp for +6°C -12°C -16°C -16°C mixture mixture

T (Distillate tank): Bp for Bp for +3°C -42°C -25°C -25°C comp comp

Composition (ACN) 23,02 80,77 13,87 59, 1 1 n.d. 92,78 (Bottoms liquid,

mass%)

Composition (ACN) 83, 1 1 83, 19 83, 1 96,2 n.d. 96,51 (Distillate, mass%)

Liquid Subjected to 2615 Previous Previous Previo Previou Prevoio Distillation (ml) m distillate distillate us s us

I used used distillat distillate distillate e used used used

Vol( Bottom liquid, 415 ml Approxima 245 ml 80 ml No n.d. ml) tely 100 ml bottom

liquid

remaine d

Vol(Distillate, ml) 2150 ml Approxima 330 ml 180 ml 120 ml n.d.

tely 2000

ml

p(Bottoms liquid, 0,956 0,809 0,976 0,858 n.d. Unknow g/ml) n p(Distillate, g/ml) 0,8137 0,815 0,813 0,782 n.d. n.d.

Reboiler size (ml) 3500 3500 3500 500 500 500

Reboiler jacket N/A N/A Yes Yes Yes Yes cooled

Reflux condensers 3/0 3/0 4/0 0/2 0/2 0/2 packed/unpacked (1/2) (1/2) (1/3) (1/1) (1/1) (1/1)

(vertical/angled)

Parallell reflux lines No No 3 No No No Distillate 1 1 1 1 1 1 Condensers

Parallell distillate No No 3 No No No

lines

Distillate tank size 3500 3500 3500 500 500 500

(ml)

5 Example 3

An acetonitrile-water mixture, 570 ml, containing 88 wt% of acetonitrile and 12 wt% of water, i.e. an acetonitrile-water mixture above the azeotropic composition at 1 atm was distilled at 1 atm in one single step.

Table X describes how much equipment was used in the experiment. Furthermore, it 10 contains volume, density and temperature data, as well as achieved compositions for distillates and bottom liquids.

The experiment used helium (not nitrogen or argon as in Example 1 and 2) and lowered temperatures to distil at lower dew pressures.

The acetonitrile contents in the distillate was higher than in the starting mixture, 15 suggesting that The experiment was carried out at a distillate tank temperature of -20°C and the distillate reached 93.3 mass% acetonitrile - well beyond both the starting composition 88.1 mass% acetonitrile and the atmospheric dew pressure azeotropic composition of 86 mass%.

It was concluded that the azeotrope had been shifted towards a higher acetonitrile when 20 helium was used as inert gas. As example 1 distilled acetonitrile-water using nitrogen as inert gas, example 2 used argon and as example 3 used helium, it was also concluded that for distillation at dew pressures lower than atmospheric pressure, for at least acetonitrile-water no matter which inert gas is used, the same effect is reached - the azeotrope was shifted. Table 2 shows experimental parameters as well as results 25 obtained in the experiments. Table -2f

1!

Example 4

A formic acid-water mixture, 1565 g, containing 14 wt% of water and 86 wt% of formic acid, i.e. an formic acid-water mixture below the azeotropic composition at 1 atm (22 wt%, DDBST GmbH) was distilled in one step.

Hereinafter the distillation steps are called distillation experiment #1/6, #2/6, #3/6, #4/6, #5/6 and distillation experiment #6/6, respectively. It will be appreciated that a distillation experiment of a higher number used the distillate from the distillation of its previous number. Table 3 describes how much equipment was used in each experiment. Furthermore, it contains volume, density and temperature data, as well as achieved compositions for distillates and bottom liquids.

The experiment was mainly carried out under an atmosphere of nitrogen (except during short nitrogen shortages, when argon was used instead) and thus at dew pressures lower than atmospheric.

The distillation was carried out at a reboiler temperature of -2°C and a distillate tank temperature of -6°C to -22°C. During the experiment, a glassware thermometer connection point was damaged. The glassware was mended using a very thick layer of plastic film and pressure was applied to avoid contact with ambient air. During the experiment, heavy corrosion was observed on metal clips on hoses nearby the glassware damage point. When the experiment was finished the bottom liquid (255 g) and the distillate (201 g) were weighed. From the 1565 g of starting mixture, the sum of the product bottom liquid weight and the product distillate weight was 456 g, hence 70% of the starting mixture had leaked out.

The bottom liquid reached 44.9 wt% water - well beyond the atmospheric dew pressure azeotropic composition of 22 wt% water. The distillate had a concentration of 28.2 wt% water. Formic acid-water is a maximum-boiling azeotrope. It was thus concluded that now also a maximum-boiling pressure-sensitive azeotrope had been shifted. Table 3 shows experimental parameters as well as results obtained in the experiments.

Tabie-3f

1

Example 5

An acetone-methanol mixture, 2640 g, containing 75.3 wt% of acetone and 24.7 wt% of methanol, i.e a mixture below the azeotropic composition at 1 atm (86.6 mass%) was distilled in three distillation steps.

Hereinafter the distillation steps are called distillation experiment #1/3, #2/3 and #3/3, respectively. It will be appreciated that a distillation experiment of a higher number used the distillate from the distillation of its previous number. Table 4 describes how much equipment was used in each experiment. Furthermore, it contains volume, density and temperature data, as well as achieved compositions for distillates and bottom liquids. All experiments were carried out at lowered temperatures to distil at lower dew pressures and used nitrogen as inert gas Experiment #3/3 was carried out at a distillate tank temperature of -35°C and the distillate reached 96,4 wt% acetone - well beyond the atmospheric dew pressure azeotropic composition of 86.6 wt% acetone. The distillation thus obtained a distillate only 3,6 mass% from pure acetone. It was concluded that the azeotrope had been shifted. Table 4 shows experimental parameters as well as results obtained in the experiments.

Table 4:

f

Example 6

A mixture comprising diisopropyl ether (DIPE)-isopropyl alcohol (I PA) was used in this example. Table 5

The invention is further illustrated by the following non-limitative claims.