(19)
(11)EP 2 615 079 B1

(12)EUROPEAN PATENT SPECIFICATION

(45)Mention of the grant of the patent:
27.11.2019 Bulletin 2019/48

(21)Application number: 11823563.9

(22)Date of filing:  06.09.2011
(51)International Patent Classification (IPC): 
C07C 17/38(2006.01)
C07C 17/389(2006.01)
B01D 53/28(2006.01)
B01D 53/26(2006.01)
C07C 21/18(2006.01)
(86)International application number:
PCT/JP2011/070253
(87)International publication number:
WO 2012/033088 (15.03.2012 Gazette  2012/11)

(54)

METHOD FOR REMOVING MOISTURE FROM HYDROFLUOROOLEFINE COMPOUNDS

VERFAHREN ZUR ENTFERNUNG VON FEUCHTIGKEIT AUS HYDROFLUOROLEFINVERBINDUNGEN

PROCÉDÉ D'ÉLIMINATION DE L'HUMIDITÉ DE COMPOSÉS HYDROFLUOROOLEFINES


(84)Designated Contracting States:
AL AT BE BG CH CY CZ DE DK EE ES FI FR GB GR HR HU IE IS IT LI LT LU LV MC MK MT NL NO PL PT RO RS SE SI SK SM TR

(30)Priority: 07.09.2010 JP 2010200218

(43)Date of publication of application:
17.07.2013 Bulletin 2013/29

(73)Proprietor: Daikin Industries, Ltd.
Osaka 530-8323 (JP)

(72)Inventor:
  • TAKAHASHI, Kazuhiro
    Settsu-shi Osaka 566-0044 (JP)

(74)Representative: Hoffmann Eitle 
Patent- und Rechtsanwälte PartmbB Arabellastraße 30
81925 München
81925 München (DE)


(56)References cited: : 
JP-A- 2009 539 598
US-A- 2 877 276
JP-B1- S5 012 405
US-A- 5 723 702
  
  • DATABASE WPI Week 197523 Thomson Scientific, London, GB; AN 1975-38585W XP002740419, & JP S50 12405 B (DAIKIN IND LTD) 12 May 1975 (1975-05-12)
 
Remarks:
The file contains technical information submitted after the application was filed and not included in this specification
 
Note: Within nine months from the publication of the mention of the grant of the European patent, any person may give notice to the European Patent Office of opposition to the European patent granted. Notice of opposition shall be filed in a written reasoned statement. It shall not be deemed to have been filed until the opposition fee has been paid. (Art. 99(1) European Patent Convention).


Description

Technical Field



[0001] The present invention relates to a method for removing moisture from hydrofluoroolefins.

Background Art



[0002] Pentafluoroethane (HFC-125), difluoromethane (HFC-32), and other hydrofluorocarbons (HFC) are widely used as important alternatives for chlorofluorocarbons (CFC), hydrochlorofluorocarbons (HCFC), and other substances that may destroy the ozone layer. Hydrofluorocarbons have various applications, such as heat transfer media, refrigerants, foaming agents, solvents, cleaning agents, propellants, and fire extinguishers, and are consumed in large amounts.

[0003] However, these hydrofluorocarbons are potent global-warming substances. Many people are concerned that their diffusion may affect global warming. To combat this, hydrofluorocarbons are collected after being used; however, not all of them can be collected, and, for example, their diffusion due to leakage cannot be disregarded. In particular, for use in e.g. refrigerants or heat transfer media, although substitution of hydrofluorocarbons with CO2 or hydrocarbon-based substances has been studied, CO2 refrigerants have many difficulties in reducing comprehensive greenhouse gas emissions, including energy consumption, because of the requirement of large equipment due to the low efficiency of the CO2 refrigerants, and hydrocarbon-based substances have safety problems due to their high flammability.

[0004] Recently, hydrofluoroolefins with a low warming potential are attracting attention as substances that can solve these problems. "Hydrofluoroolefin" is a generic name for unsaturated hydrocarbons containing hydrogen and fluorine. Most of them are obtained by dehydrohalogenation of corresponding alkanes. For example, as a typical method for producing 2,3,3,3-tetrafluoropropene (HFO-1234yf), which is a hydrofluoroolefin, a method of eliminating HF from 1,1,1,2,3-pentafluoropropane (HFC-245eb) or 1,1,1,2,2-pentafluoropropane (HFC-245cb) is known. Since HFO-1234yf obtained by this method is in the form of a mixture with HF, it is necessary to somehow remove the HF. The simplest method of removing acid from a mixed gas of hydrofluoroolefin and acid is to absorb the acid with water. In this method, however, mist and water corresponding to vapor pressure are inevitably mixed into hydrofluoroolefins. There are various other sources of water, such as moisture contained in the starting materials, moisture produced from the catalyst, and moisture remaining in the equipment. Moisture contained in hydrofluoroolefins, which are finished products, affects, for example, their stability, device corrosiveness and refrigerant capability, and is therefore one of the most important factors of quality control. The method for removing moisture is a particularly important technique.

[0005] As the method for removing moisture from hydrofluoroolefins, a method using a molecular sieve (e.g., zeolite) as a water absorbent is known. For example, WO 2007/144632 discloses a method for drying a fluid of a fluoropropene, such as HFO-1234yf, by passing it through zeolite. However, a large packed column is required to treat fluoropropenes with a low moisture content using a water absorbent, which causes poor treatment efficiency. In addition, in the method using an absorbent, there are problems that it is necessary to regularly stop the equipment to recover the performance of the absorbent and exchange the absorbent, which leads to low productivity and necessitates the use of two series of equipment. Moreover, a large amount of industrial waste is generated during the exchange of the absorbent. Furthermore, depending on the hydrofluoroolefins to be treated, they may be absorbed to the absorbent, presumably inhibiting the absorption of water that should be essentially removed.

[0006] For the above reasons, there is a demand for more efficient methods for removing moisture from hydrofluoroolefins.

[0007] US 2,877,276 describes a process for removing water from halogenated C1-4-hydrocarbons by contacting the same with an aqueous solution of a chloride salt, cooling the contacted halogenated hydrocarbon below its cloud point temperature and above the freezing point of the system, and then separating the halogenated hydrocarbon having reduced water content.

[0008] US 5,723,702 discloses a process for removing moisture from CHClF2 comprising lowering the partial pressure of water in the CHClF2 gas with an aqueous solution of > 5 wt.-% CaCl2.

[0009] JP-B-S50-12405 relates to a process of drying F- and Cl-substituted hydrocarbons by contacting them with concentrated LiCl aqueous solution in a countercurrent contact column.

Summary of Invention


Technical Problem



[0010] The present invention was made in view of the above-described current status of the prior art. A primary object of the invention is to provide an industrially advantageous moisture removal method that can continuously and efficiently remove moisture from hydrofluoroolefins, and that produces less waste.

Solution to Problem



[0011] The present inventor conducted extensive research to achieve the above object. As a result, the present inventor found that the moisture contaminating a hydrofluoroolefin can be continuously and efficiently removed by a method comprising the step of (i) contacting a hydrofluoroolefin contaminated with moisture with an aqueous solution containing lithium chloride (LiCl). The present inventor also found that this method is economically advantageous because the aqueous solution of LiCl used in the dehydration process can be repeatedly used by reducing the moisture content thereof, and that since no waste is generated, the method has less environmental impact and is industrially excellent. Another finding was that after the moisture content of the hydrofluoroolefin is reduced by this method, dehydration is carried out using a water absorbent, such as a molecular sieve, thereby greatly reducing the moisture content of the hydrofluoroolefin by a simple process, and extending the life of the water absorbent and the period of time before having to recover the performance of the water absorbent. The present invention has been accomplished as a result of further research based on these findings.

[0012] More specifically, the present invention provides a method for removing moisture from hydrofluoroolefins, comprising the step of (i) contacting a hydrofluoroolefin contaminated with moisture with an aqueous solution containing lithium chloride (LiCl).

[0013] Preferred embodiments of the present method are as defined in the appended dependent claims and in the following detailed description.

[0014] The method for removing moisture from hydrofluoroolefins according to the present invention is described in detail below.

Target Compounds



[0015] The target compounds of the present invention are hydrofluoroolefins. The method of the present invention is advantageous because products whose moisture content is efficiently reduced can be obtained.

[0016] Specific examples of hydrofluoroolefins to be treated by the present invention include compounds of the following chemical formulae:

CF3CF=CF2 (HFO-1216yc), CF3CF=CHF (HFO-1225ye),

CF3CF=CH2 (HFO-1234yf), CF3CH=CHF (HFO-1234ze),

CF3CH=CH2 (HFO-1243zf), CF3CCl=CH2 (HCFO-1233xf),

CF2ClCCl=CH2 (HCFO-1232xf), CF3CH=CHCl (HCFO-1233zd),

CF3CCl=CHCl (HCFO-1223xd), CClF2CCl=CHCl (HCFO-1222xd),

CFCl2CCl=CH2 (HCFO-1231xf), CH2ClCCl=CCl2 (HCO-1230xa).


Method for Removing Moisture



[0017] In the present method for removing moisture from hydrofluoroolefins, it is necessary to bring the target hydrofluoroolefin contaminated with moisture into contact with an aqueous solution containing LiCl. The moisture contained in the hydrofluoroolefin is thereby absorbed by the LiCl-containing aqueous solution to reduce the moisture content of the hydrofluoroolefin.

[0018] The method of bringing the hydrofluoroolefin contaminated with moisture into contact with the LiCl-containing aqueous solution is not particularly limited. For example, when the hydrofluoroolefin is in the form of a gas, the hydrofluoroolefin is bubbled into the LiCl-containing aqueous solution. Alternatively, the LiCl-containing aqueous solution is directly sprayed onto the hydrofluoroolefin contaminated with moisture; or the LiCl-containing aqueous solution is impregnated into a porous material, such as a ceramic or activated carbon, and the porous material is then brought into contact with the hydrofluoroolefin contaminated with moisture. In particular, the moisture content of the hydrofluoroolefin can be efficiently reduced by using a water absorption column, and by spraying the LiCl-containing aqueous solution from the top portion of the column, introducing the gaseous hydrofluoroolefin from the bottom portion of the column, and extracting it from the top portion. In this method, the hydrofluoroolefin and the LiCl-containing aqueous solution can be efficiently brought into contact with each other by filling the water absorption column with a spherical or granular material that does not react with the hydrofluoroolefin or the LiCl.

[0019] The treatment temperature, treatment pressure, and other conditions of the above method using a water absorption column are not particularly limited. Conditions may be selected so that the hydrofluoroolefin is present as a gas, and the moisture can be efficiently absorbed. Generally, the hydrofluoroolefin may be supplied to the water absorption column at normal temperature and normal pressure while being slightly pressurized under conditions required to introduce the hydrofluoroolefin into the water absorption column.

[0020] The concentration of the LiCl in the LiCl-containing aqueous solution is preferably as high as possible so that the LiCl-containing aqueous solution can efficiently absorb moisture. However, an overly high concentration facilitates crystallization of the LiCl. The specific concentration range may be as high as possible within a range in which the LiCl is not crystallized. For example, the concentration is generally preferably 20-50 wt.-%, and more preferably 36-42 wt.-%.

[0021] The moisture content of the hydrofluoroolefin can also be reduced by using, in place of the LiCl-containing aqueous solution, a water absorbent, such as concentrated sulfuric acid, glycerin, or triethylene glycol, or by using such a water absorbent in combination with the LiCl-containing aqueous solution.

[0022] In the present invention, after moisture is removed from the hydrofluoroolefin by the above method, the moisture content can be further reduced by performing, if necessary, dehydration using a water absorbent, such as a molecular sieve. Thereby, high-quality hydrofluoroolefins with a lower moisture content can be easily obtained. In addition, this method can extend the life of the water absorbent and the period of time before having to recover the performance of the water absorbent, and enables the dehydration of hydrofluoroolefins under industrially advantageous conditions.

[0023] As the water absorbent, known water absorbents can be used. Examples of such water absorbents include zeolite and other molecular sieves, silica gel, silica alumina, etc. Dehydration using a water absorbent can be performed by a known method. For example, the hydrofluoroolefin dehydrated with a LiCl-containing aqueous solution is supplied to a dehydrator filled with a water absorbent, and passed through the dehydrator.

Advantageous Effects of Invention



[0024] According to the present method for removing moisture from hydrofluoroolefins, the moisture content of various hydrofluoroolefins contaminated with moisture can be reduced continuously and efficiently by a simple process. Moreover, the method of the present invention is economically advantageous because the aqueous solution of LiCl used in the dehydration process can be repeatedly used by reducing the moisture content thereof. Furthermore, the method of the present invention has less environmental impact because no waste is generated, and the moisture content of hydrofluoroolefins can be reduced under industrially advantageous conditions.

Brief Description of Drawing



[0025] Fig. 1 is a flow diagram showing the dehydration process of HFO-1234yf in Example 1.

Description of Embodiment



[0026] The present invention is described in more detail below with reference to an Example.

Example 1



[0027] Moisture contained in 2,3,3,3-tetrafluoropropene (HFO-1234yf) was removed by the following method which is described on the basis of the flow diagram shown in Fig. 1.

[0028] Using a water absorption column T11 (height: 3 m, inner diameter: 12 cm), HFO-1234yf with a moisture content of 2,000 weight ppm was continuously supplied from the bottom portion of the column at a rate of 13.8 kg/hr (S11). Meanwhile, an aqueous solution of LiCl with a concentration of 42 wt.-% was supplied from the top portion of the column and sprayed into the column (S13). The pressure to supply HFO-1234yf into the column was 0.05 MPaG, and the column top temperature was 25°C.

[0029] HFO-1234yf supplied from the bottom portion was extracted from the top portion and sent to the subsequent step (S12). This operation allowed sufficient contact of HFO-1234yf contaminated with moisture supplied from the bottom portion with the aqueous solution of LiCl. Consequently, HFO-1234yf with a lower moisture content was obtained from the top portion.

[0030] On the other hand, the aqueous solution of LiCl supplied from the top portion was extracted from the bottom portion and circulated to the top portion (S13). A part of the extracted aqueous solution of LiCl was transferred to a dehydration tank V11 for thermal vacuum dehydration. The water resulting from dehydration was discharged (S15), and the aqueous solution of LiCl with a lower moisture content was placed in the lower part of the water absorption column T11 (S14). The concentration of the circulating aqueous solution of LiCl was thereby maintained constant.

[0031] Table 1 shows the component composition in each step.
[Table 1]
StreamS11S12S13S14S15
 Flow rate (kg/hr)
HFO-1234yf 13.8 13.8      
Water 0.0276 0.0055 10.2 0.28 0.0221
LiCl     7.4 0.22  
Moisture content in gas (weight unit) 2,000 ppm 400 ppm      
Concentration of LiCl aqueous solution (weight unit)     42 wt% 44 wt%  


[0032] As is obvious from these results, the above-described method can continuously and efficiently reduce the moisture content of HFO-1234yf.


Claims

1. A method for removing moisture from hydrofluoroolefins, comprising the step of

(i) contacting a hydrofluoroolefin contaminated with moisture with an aqueous solution containing lithium chloride.


 
2. The method of claim 1, wherein the fluorine-containing compound is 2,3,3,3-tetrafluoropropene.
 
3. The method of claim 1 or 2, wherein the aqueous solution containing lithium chloride has a concentration of 20-50 wt.-%.
 
4. The method of any of claims 1-3, further comprising the steps of

(ii) reducing the water content of the lithium chloride-containing aqueous solution used in step (i), and

(iii) then reusing the solution having a reduced water content in step (i).


 
5. The method of any of claims 1-4, which after step (i) further comprises the step of
(iv) bringing the hydrofluoroolefin treated in step (i) into contact with a water absorbent.
 


Ansprüche

1. Verfahren zum Entfernen von Feuchtigkeit aus Hydrofluorolefinen, das folgenden Schritt umfasst:

(i) Kontaktieren eines mit Feuchtigkeit verunreinigten Hydrofluorolefins mit einer wässrigen Lösung die Lithiumchlorid enthält.


 
2. Verfahren gemäß Anspruch 1, bei dem die fluorhaltige Verbindung 2,3,3,3-Tetrafluorpropen ist.
 
3. Verfahren gemäß Anspruch 1 oder 2, bei dem die wässrige Lösung, die Lithiumchlorid enthält, eine Konzentration von 20-50 Gew.-% aufweist.
 
4. Verfahren gemäß mindestens einem der Ansprüche 1-3, das ferner folgende Schritte umfasst:

(ii) Reduzieren des Wassergehalts der in Schritt (i) verwendeten Lithiumchlorid-enthaltenden wässrigen Lösung, und

(iii) danach Wiederverwendung der Lösung mit einem reduzierten Wassergehalt in Schritt (i).


 
5. Verfahren gemäß mindestens einem der Ansprüche 1-4, das nach Schritt (i) ferner folgenden Schritt umfasst:
(iv) Inkontaktbringen des in Schritt (i) behandelten Hydrofluorolefins mit einem Wasserabsorptionsmittel.
 


Revendications

1. Procédé d'élimination de l'humidité à partir d'hydrofluorooléfines, comprenant l'étape suivante

(i) la mise en contact d'une hydrofluorooléfine contaminée avec de l'humidité avec une solution aqueuse contenant du chlorure de lithium.


 
2. Procédé selon la revendication 1, dans lequel le composé contenant du fluor est le 2,3,3,3-tétrafluoropropène.
 
3. Procédé selon la revendication 1 ou 2, dans lequel la solution aqueuse contenant du chlorure de lithium présente une concentration de 20 à 50 % en poids.
 
4. Procédé selon l'une quelconque des revendications 1 à 3, comprenant en outre les étapes suivantes

(ii) la réduction de la teneur en eau de la solution aqueuse contenant du chlorure de lithium utilisée dans l'étape (i), et

(iii) ensuite la réutilisation de la solution présentant une teneur réduite en eau dans l'étape (i).


 
5. Procédé selon l'une quelconque des revendications 1 à 4, qui après l'étape (i) comprend en outre l'étape suivante
(iv) la mise en contact de l'hydrofluorooléfine traitée dans l'étape (i) avec un absorbeur d'eau.
 




Drawing








Cited references

REFERENCES CITED IN THE DESCRIPTION



This list of references cited by the applicant is for the reader's convenience only. It does not form part of the European patent document. Even though great care has been taken in compiling the references, errors or omissions cannot be excluded and the EPO disclaims all liability in this regard.

Patent documents cited in the description