WO2018178552A1

WO2018178552A1 - Method for the production of 2,3,3,3-tetrafluoropropene

Info

Publication number: WO2018178552A1
Application number: PCT/FR2018/050732
Authority: WO
Inventors: Dominique Deur-Bert; Laurent Wendlinger
Original assignee: Arkema France
Priority date: 2017-03-28
Filing date: 2018-03-27
Publication date: 2018-10-04
Also published as: FR3064627B1; FR3064627A1

Abstract

The present invention relates to a method for the production of 2,3,3,3- tetrafluoropropene, comprising the steps of: a) bringing a compound of formula (I) CH(n+2)(X)m-CHp(X) (n+1)-CX(3+p-m) into contact, in the gaseous phase, with hydrofluoric acid, in which formula X represents independently F or Cl; n, m, p are, independently of one another, 0 or 1 with (n+m) = 0 or 1, (n+p) = 0 or 1 and (m-p) = 0 or 1, at least one X being Cl, in order to produce a flow of products comprising 2,3,3,3-tetrafluoropropene, HCl and HF; b) cooling the flow of products from the reactor in step (a) to a temperature below 100°C, advantageously to a temperature of between 0°C and 70°C, preferably to a temperature of between 20°C and 50°C; c) distilling the flow cooled in step (b) in order to form a first stream comprising 2,3,3,3-tetrafluoropropene and HCl, and a second stream comprising HF; d) compressing the first stream obtained in step (c) in order to form a first compressed stream; e) distilling the first compressed stream obtained in step (d) in order to produce a third stream comprising HCl and a fourth stream comprising 2,3,3,3- tetrafluoropropene; f) purifying the fourth stream obtained in step (e). The method is characterised in that step (a) is carried out at a pressure of less than 10 bar, preferably at a pressure of between 2 and 8 bar, in particular between 3 and 7 bar, and more specifically between 5 and 7 bar.

Description

Process for producing 2,3,3,3-tetrafluoropropene

Technical field of the invention

The present invention relates to a process for producing 2,3,3,3-tetrafluoropropene, also known as HFO-1234yf. In particular, the present invention relates to a process for the production of 2,3,3,3-tetrafluoropropene carried out at high pressure, preferably at a pressure of less than 10 bara.

Technological background of the invention

Hydrofluorocarbons (HFCs) and in particular hydrofluoroolefins (HFOs), such as 2,3,3,3-tetrafluoropropene (HFO-1234yf), are compounds known for their properties as coolants and coolants, fire extinguishers, propellants, foaming agents , blowing agents, gaseous dielectrics, polymerization medium or monomer, carrier fluids, abrasive agents, drying agents and power generating unit fluids. HFOs have been identified as desirable alternatives to HCFCs because of their low ODP (Ozone Depletion Potential or GWP) and GWP (Global Warming Potential) values.

Most of the hydrofluoroolefin manufacturing processes involve a fluorination and / or dehydrohalogenation reaction. This type of reaction is carried out in the gas phase or in the liquid phase and generates impurities which must therefore be eliminated in order to obtain the desired compound in a degree of purity sufficient for the intended applications.

Many processes for the production of hydrofluoroolefins have been developed. For example, WO2012 / 098420 discloses the production of 2,3,3,3-tetrafluoropropene by a catalytic gas-phase fluorination process using 1,1,1,2,3-pentachloropropane and / or 1,1,1,2,3-pentachloropropane. , 2,2,3-pentachloropropane. The process is carried out at a pressure of between 3 and 20 bar. The flow of products from the catalytic fluorination reactor is purified by distillation.

Also known from WO2013 / 114015 is a process for producing 2,3,3,3-tetrafluoropropene in the gas phase from 1,1,1,2,3-pentachloropropane and / or 1,1,2,2, 3-pentachloropropane, the gas stream recovered after the reaction is partially condensed to form a gaseous fraction and a liquid fraction, both being compressed before being distilled. WO 2007/138210 also discloses a process for producing hydrofluorocarbons from hydrofluorochlorocarbon and hydrofluoric acid in the gas phase in the presence of a catalyst. The process is carried out at a pressure of 1 to 3 bar. The gas stream leaving the reactor is compressed using a compressor before being sent to the distillation column.

The processes of the prior art can be simplified in order to improve and increase the industrial and economic viability thereof.

Summary of the invention

According to a first aspect, the present invention provides a process for producing 2,3,3,3-tetrafluoropropene comprising the steps of:

a) contacting, in the gas phase, a compound of formula (I) CH) (X) m-CHp (X) ( _n + 1) -CX + _P -m) wherein X independently represents F or Cl; n, m, p are independently of one another 0 or 1 with (n + m) = 0 or 1, (n + p) = 0 or 1 and (mp) = 0 or 1, at least one X being Cl, with hydrofluoric acid to obtain a product stream comprising 2,3,3,3-tetrafluoropropene, HCl and HF,

b) cooling the product stream from the reactor of step a) at a temperature below 100 ° C, preferably at a temperature of 0 ° C to 70 ° C, preferably at a temperature of 20 ° C to 50 ° VS,

c) distilling the stream cooled in step b) to form a first stream comprising 2,3,3,3-tetrafluoropropene and HCl, and a second stream comprising HF,

d) compressing the first stream obtained in step c) to form a first compressed stream,

e) distilling said first compressed stream obtained in step d) to obtain a third stream comprising HCl and a fourth stream comprising 2,3,3,3-tetrafluoropropene,

f) purifying said fourth stream obtained in step e),

characterized in that step a) is carried out at a pressure of less than or equal to 10 bara, preferably at a pressure of 2 to 8 bara, in particular at a pressure of 3 to 7 bara, more particularly at a pressure of from 5 to 7 bara.

According to a preferred embodiment, said first current obtained in step c) is heated prior to the implementation of step d). According to a preferred embodiment, said first stream obtained in step c) is heated to a temperature between 0 ° C and 40 ° C.

According to a preferred embodiment, in step d), said first stream is compressed at a pressure of between 10 and 25 bara, preferably between 15 and 20 bara.

According to a preferred embodiment, the first compressed stream obtained in step d) is cooled before being distilled.

According to a preferred embodiment, the first compressed stream obtained in step d) is cooled to a temperature below 50 ° C.

According to a preferred embodiment, in step e), the temperature at the top of the distillation column is between 0 ° C. and -35 ° C.

According to a preferred embodiment, the third stream comprising HCl is recovered in step e) at the top of the distillation column and is brought to a temperature of between -40 ° C. and 20 ° C. before being purified according to the steps following:

i) catalytic hydrolysis;

ii) washing with an acid solution;

iii) adsorption of impurities with activated carbon;

iv) adiabatic or isothermal absorption of hydrochloric acid in an aqueous solution, for collecting a solution of hydrochloric acid.

According to a preferred embodiment, the compound of formula (I) is selected from the group consisting of 1,1,1,2,3-pentachloropropane, 1,1,2,3-tetrachloropropene, 2,3,3,3 tetrachloropropene, 2-chloro-3,3,3-trifluoropropene, 2-chloro-1,1,1,2-tetrafluoropropane, 1,2-dichloro-3,3,3-trifluoropropane and 1,1,1,2 2-pentachloropropane, or a mixture thereof; and step a) is carried out in the presence or absence of a catalyst to produce a product stream comprising 2,3,3,3-tetrafluoropropene, HCl, HF and also at least one of the compounds selected from the group consisting of 2-chloro-3,3,3-trifluoropropene, 1,1,1,2,2-pentafluoropropane, 1,1,1,3,3-pentafluoropropane, 1,3,3,3-tetrafluoropropene, 3, 3,3-trifluoropropene, chloromethane, 1,1-difluoroethane, chloropentafluoroethane, 1,1,1,2-tetrafluoroethane, trans-1,2,3,3,3-pentafluoropropene and 1-chloro-3,3,3- trifluoropropene.

According to a preferred embodiment, the fourth stream comprising 2,3,3,3-tetrafluoropropene is purified by decantation at a temperature between -50 ° C and 0 ° C to form a lower phase comprising 2,3,3,3 tetrafluoropropene and an upper phase comprising HF, optionally recycled in step a). According to another preferred embodiment, the fourth stream comprising 2,3,3,3-tetrafluoropropene is purified in step f) by the following steps:

i ') contacting said fourth stream with an aqueous solution of hydrofluoric acid of concentration greater than 40% to form a two-phase stream comprising 2,3,3,3-tetrafluoropropene and HF,

ii ') storing said two-phase current in a buffer tank, said two-phase current consisting of a gas phase G1 and a liquid phase L1,

iii ') passing said gaseous phase G1 of said two-phase stream in an absorption column fed countercurrently with an aqueous stream to form a gaseous stream G2 comprising 2,3,3,3-tetrafluoropropene and an aqueous stream L2 comprising HF .

According to a preferred embodiment, said lower phase or said phase G1 and / or said stream G2 also comprise, in addition to 2,3,3,3-tetrafluoropropene, 1,1,1,2,2-pentafluoropropane and 1,3, 3,3-tetrafluoropropene; and; the lower phase, said G1 gas phase or said G2 stream is distilled by extractive distillation to form a stream comprising 2,3,3,3-tetrafluoropropene and 1,1,1,2,2-pentafluoropropane and a stream comprising 1.3 3,3-tetrafluoropropene; preferably the extractive distillation is carried out in the presence of an organic extractant selected from the group consisting of ethylamine, isopropylamine, diethylether, n-propylamine, diethylamine, diethoxymethane, isopropylacetate, 3-pentylamine, 2-methoxyethanamine, tert-butylacetate , 1,4-dioxane, 1,1-diethoxyethane, trimethoxymethane, n-pentylamine, 1,3-dioxane, sec-butylacetate, 1,2-diaminoethane, 1-methoxy-2-propanol, 1,2-propanediamine, n butylacetate, 2-methoxy-1-propanol, hexanal.

Brief description of the figures

Fig. 1 schematically shows a method according to a particular embodiment of the present invention.

Fig. 2 schematically shows a method according to a particular embodiment of the present invention.

Fig. 3 schematically shows a device for removing hydrofluoric acid according to a particular embodiment of the present invention.

Detailed description of the invention The present invention relates to a process for producing 2,3,3,3-tetrafluoropropene. The present process comprises in step a) bringing into contact a compound of formula (I) CH (n + 2) (X) m-CH _p (X) (n + 1) -CX (3 + pm where X is independently F or Cl; n, m, p are independently of one another 0 or 1 with (n + m) = 0 or 1, (n + p) = 0 or 1 and (mp) = 0 or 1, at least one X being Cl, with hydrofluoric acid to obtain a product stream comprising 2,3,3,3-tetrafluoropropene, HCl and HF. Step a) of the present process can be carried out at a temperature of 200 to 450 ° C, preferably 250 to 400 ° C, preferably 280 to 380 ° C. Step a) of the present process may be carried out at a contact time of 3 to 100 seconds, preferably 4 to 75 seconds, preferably 5 to 50 seconds. Step a) of the present process can be carried out with a HF / compound of formula (I) molar ratio of from 3: 1 to 150: 1, advantageously from 4: 1 to 125: 1, preferably 5: 1 at 100: 1. The process, preferably step a), may be carried out in the presence of a polymerization inhibitor, preferably selected from the group consisting of p-methoxyphenol, t-amylphenol, limonene, d, l-limonene, quinones , hydroquinones, epoxides, amines and mixtures thereof. Step a) of the present process can be carried out in the presence of oxygen or chlorine, advantageously from 0.005 to 15 mole%, preferably from 0.5 to 10 mole% of oxygen or chlorine per mole of compound of formula (I).

Preferably, the compound of formula (I) is selected from the group consisting of 1,1,1,2,3-pentachloropropane, 1,1,2,3-tetrachloropropene, 2,3,3,3-tetrachloropropene, 2 chloro-3,3,3-trifluoropropene, 2-chloro-1,1,2,2-tetrafluoropropane, 1,2-dichloro-3,3,3-trifluoropropene and 1,1,1,2,2-pentachloropropane , or a mixture of these. In particular, the compound of formula (I) is 1,1,1,2,3-pentachloropropane, 2-chloro-3,3,3-trifluoropropene or 1,1,2,3-tetrachloropropene.

Step a) is carried out at a pressure of less than or equal to 10 bara, preferably less than or equal to 7 bara. Step a) is carried out at a pressure of 1 to 8 bara, preferably 2 to 8 bara, preferably 3 to 7 bara, in particular 5 to 7 bara.

Step a) is carried out in the gas phase or in the liquid phase.

Step a) of the present process can be carried out in the liquid phase in the presence of a catalyst. The catalyst may be a Lewis acid, a metal halide-containing catalyst, in particular an antimony halide, tin, tantalum, titanium, a transition metal such as molybdenum, niobium, iron, cesium, transition metal oxides, Group IVb metal halides, Group Vb metal halides, chromium fluoride, fluorinated chromium oxides, or a mixture thereof. For example, the catalyst can be SbCl ₅ , SbCU, TiCl ₄ , SnCl ₄ , TaCl ₅ , NbCl ₅ , TiCl ₄ , FeCl 3, MoC, CsCl, and the corresponding fluorinated compounds. The catalyst may contain an ionic liquid as described for example in applications WO2008 / 149011 (in particular from page 4, line 1 to page 6 line 15, included by reference) and WO01 / 81353, as well as the reference "liquid In the liquid phase, step a) can be carried out at a temperature of between 30 and 200.degree. C., advantageously between 40.degree. and 40.degree. C. and 170 ° C., preferably between 50 and 150 ° C. Preferably, the HF / compound of formula (I) molar ratio may be from 0.5: 1 to 50: 1, advantageously from 3: 1 to 20 : 1 and preferably from 5: 1 to 15: 1.

Preferably, step a) of the present process is carried out in the gas phase. Step a) of the present process may be carried out in the presence or absence of a catalyst.

When it is carried out in the gaseous phase and in the absence of catalyst, step a) can be carried out with a HF / compound of formula (I) molar ratio of from 3: 1 to 150: 1, and preferably at a temperature of 200 to 450 ° C, and preferably 300 to 430 ° C.

When carried out in the gaseous phase and in the presence of a catalyst, step a) can be carried out in the presence of a catalyst based on a metal comprising a transition metal oxide or a derivative or a halide or an oxyhalide of such a metal. For example, FeCU, chromium oxyfluoride, chromium oxides (possibly subjected to fluorination treatments), chromium fluorides and mixtures thereof may be mentioned. Other possible catalysts are carbon-supported catalysts, antimony catalysts, aluminum catalysts (eg AlF 3 and Al 2 O 3, alumina oxyfluoride and alumina fluoride). It is generally possible to use a chromium oxyfluoride, a fluoride or an aluminum oxyfluoride, or a supported or non-supported catalyst containing a metal such as Cr, Ni, Fe, Zn, Ti, V, Zr, Mo, Ge or Sn. Pb, Mg, Sb. Reference can be made in this regard to document WO 2007/079431 (at p.7, 1.1-5 and 28-32), EP 939071 (paragraph [0022]), WO 2008/054781 (at p.9). l.22-p.l0 1.34), and WO 2008/040969 (claim 1), to which reference is expressly made. The catalyst is more preferably based on chromium and it is more particularly a mixed catalyst comprising chromium. According to one embodiment, for any one of the reaction steps a mixed catalyst comprising chrome and nickel. The molar ratio Cr / Ni (based on the metal element) is generally 0.5 to 5, for example 0.7 to 2, for example about 1. The catalyst may contain from 0.5 to 20% by weight of nickel. The metal may be present in metallic form or in the form of a derivative, for example an oxide, halide or oxyhalogenide. These derivatives are preferably obtained by activation of the catalytic metal. The support is preferably made of aluminum, for example alumina, activated alumina or aluminum derivatives, such as aluminum halides and aluminum oxyhalides, for example described in US Pat. US 4,902,838, or obtained by the activation method described above. The catalyst may comprise chromium and nickel in an activated or non-activated form, on a support which has been subjected to activation or not. Reference can be made to WO 2009/118628 (especially at p.4, l.30-p.7 1.16), which is expressly referred to herein. Another preferred embodiment is based on a mixed catalyst containing chromium and at least one co-catalyst chosen from the salts of Co, Mn, Mg and Zn, preferably Zn. Said cocatalyst is preferably present in a content of 1 to 10% by weight based on the weight of the catalyst. Prior to use, the catalyst is preferably activated with air, oxygen or chlorine and / or with HF. For example, the catalyst is preferably subjected to activation with air or oxygen and HF at a temperature of 100 to 500 ° C, preferably 250 to 500 ° C and more preferably 300 to 500 ° C. at 400 ° C. The activation time is preferably from 1 to 200 hours and more particularly from 1 to 50 hours. This activation may be followed by a final fluorination activation step in the presence of an oxidizing agent, HF and organic compounds. The molar ratio of HF / organic compounds is preferably from 2 to 40 and the molar ratio of oxidation agent / organic compounds is preferably from 0.04 to 25. The temperature of the final activation is preferably from 300 to 400 ° C. C and its duration preferably from 6 to 100 h.

In the presence of a catalyst, step a) can be carried out with a HF x compound molar ratio of formula (I) of from 3: 1 to 150: 1, preferably from 4: 1 to 125: 1, preferably from 5: 1 to : 1 to 100: 1. In the presence of a catalyst, step a) can be carried out at a pressure of less than or equal to 10 bara, advantageously from 2 to 8 bara, preferably from 3 to 7 bara, more particularly from 5 to 7 bara. Step a) may be carried out at a temperature of 200 to 450 ° C, preferably 300 to 430 ° C, preferably 320 to 420 ° C. The contact time (catalyst volume divided by total reagent flow, adjusted to operating pressure and temperature) may be from 3 to 100 seconds, preferably from 4 to 75 seconds, preferably from 5 to 50 seconds.

Preferably, step a) of the present process is carried out in the gas phase in the presence of a catalyst and a compound of formula (I) chosen from the group consisting of 2,3,3,3-tetrachloropropene, 1,2-dichloro-3,3,3-trifluoropropane, 1,1,1,2,3-pentachloropropane, 2-chloro-3,3,3-trifluoropropene or 1,1,2,3-tetrachloropropene or a mixture of these to produce a product stream comprising 2,3,3,3-tetrafluoropropene and also at least one of the compounds selected from the group consisting of 2-chloro-3,3,3-trifluoropropene, 1,1,1,2,2-pentafluoropropane and 1,3,3,3-tetrafluoropropene.

In particular, step a) of the present process is carried out in the gas phase in the presence of a catalyst and a compound of formula (I) selected from the group consisting of 2,3,3,3-tetrachloropropene , 1,2-dichloro-3,3,3-trifluoropropane, 1,1,1,2,3-pentachloropropane, 2-chloro-3,3,3-trifluoropropene or 1,1,2,3-tetrachloropropene or mixing them to produce a product stream comprising 2,3,3,3-tetrafluoropropene and also at least one of the compounds selected from the group consisting of 2-chloro-3,3,3-trifluoropropene, 1,1, 1,2,2-pentafluoropropane, 1,1,1,3,3-pentafluoropropane, 1,3,3,3-tetrafluoropropene, 3,3,3-trifluoropropene, chloromethane, 1,1-difluoroethane, chloropentafluoroethane, 1, 1,1,2-Tetrafluoroethane, trans-1,2,3,3,3-pentafluoropropene and 1-chloro-3,3,3-trifluoropropene.

Step a) of the present process can be carried out in two steps according to the following sequence: a1) contacting 2,3,3,3-tetrachloropropene, 1,2-dichloro-3,3,3-trifluoropropane 1,1,1,2,3-pentachloropropane or 1,1,2,3-tetrachloropropene or a mixture thereof with HF to form 2-chloro-3,3,3-trifluoropropene; and a2) contacting the resulting 2-chloro-3,3,3-trifluoropropene with HF to form 2,3,3,3-tetrafluoropropene. Step a1) and step a2) may be carried out in the gas phase or in the liquid phase, preferably in the gas phase. Step a1) and step a2) can be carried out in continuous mode or in batch mode with optionally a step of storage or purification of 2-chloro-3,3,3-trifluoropropene.

Step a1) can preferably be carried out in the gaseous phase in the presence or absence of a catalyst. The catalyst, when present, may be as described above in connection with step a). Step a1) can be carried out with a HF × compound molar ratio of formula (I) of from 3: 1 to 150: 1, advantageously from 4: 1 to 125: 1, preferably from 5: 1 to 100: 1. Step a1) can be carried out at a pressure of less than or equal to 10 bara, advantageously from 2 to 8 bara, preferably from 3 to 7 bara, more particularly from 5 to 7 bara. Step a1) can be carried out at a temperature of 200 to 450 ° C, preferably 300 to 430 ° C, preferably 320 to 420 ° C. The contact time (catalyst volume divided by total reagent flow, adjusted to operating pressure and temperature) may be from 3 to 100 seconds, preferably from 4 to 75 seconds, preferably from 5 to 50 seconds.

Step a2) can be carried out preferably in the gas phase in the presence of a catalyst. The catalyst, when present, may be as described above in connection with step a). Step a2) can be carried out with a HF: compound of formula (I) molar ratio of from 3: 1 to 150: 1, advantageously from 4: 1 to 125: 1, preferably from 5: 1 to 100: 1. Step a2) may be carried out at a pressure of less than or equal to 10 bara, advantageously from 2 to 8 bara, preferably from 3 to 7 bara, more particularly from 5 to 7 bara. Step a2) can be carried out at a temperature of 200 to 450 ° C, preferably 300 to 430 ° C, preferably 320 to 420 ° C. The contact time (catalyst volume divided by total reagent flow, adjusted to operating pressure and temperature) may be from 3 to 100 seconds, preferably from 4 to 75 seconds, preferably from 5 to 50 seconds.

Step a1) and step a2) may be carried out in two reactors arranged in series.

Step b) of the present process consists in cooling the product stream obtained in step a) at a temperature of -20 ° C to 100 ° C, advantageously the product stream obtained in step a) is cooled at a temperature of from -10 ° C to 90 ° C, preferably from 0 ° C to 80 ° C, more preferably from 0 ° C to 70 ° C, in particular from 10 ° C to 60 ° C, more preferably ° C to 50 ° C.

Cooling of product streams can be accomplished by one or a plurality of heat exchangers. Cooling of product streams can be accomplished by passing the product stream obtained in step a) through one, two, three, four, five, six, seven, eight, nine or ten heat exchangers, preferably the number of heat exchangers is between 2 and 8, in particular between 3 and 7.

In step c), the stream cooled in step b) can then be distilled to form a first stream comprising 2,3,3,3-tetrafluoropropene and HCl and a second stream comprising HF. The first stream can be recovered at the top of the distillation column. The second stream can be recovered at the bottom of the distillation column.

The first stream formed in step c) may comprise, in addition to 2,3,3,3-tetrafluoropropene and HCl, at least one of the compounds selected from the group consisting of 2-chloro-3,3,3-trifluoropropene, 1 , 1,1,2,2-pentafluoropropane, 1,1,1,3,3-pentafluoropropane, 1,3,3,3-tetrafluoropropene, 3,3,3-trifluoropropene, chloromethane, 1,1-difluoroethane, chloropentafluoroethane 1,1,1,2-Tetrafluoroethane, trans-1,2,3,3,3-pentafluoropropene and 1-chloro-3,3,3-trifluoropropene. In particular, the first stream may comprise, besides 2,3,3,3-tetrafluoropropene and HCl, 2-chloro-3,3,3-trifluoropropene, 1,3,3,3-tetrafluoropropene and 1,1,1, 2,2-pentafluoropropane. The first stream may optionally also include hydrofluoric acid, preferably in small amounts. The second stream may comprise, in addition to HF, at least one of the compounds selected from the group consisting of 2-chloro-3,3,3-trifluoropropene, 1,1,1,2,2-pentafluoropropane, 1,1,1, 3,3-pentafluoropropane and 1-chloro-3,3,3-trifluoropropene. In particular, the second stream may comprise, besides HF, 2-chloro-3,3,3-trifluoropropene, 1-chloro-3,3,3-trifluoropropene and 1,1,1,3,3-pentafluoropropane.

Said first stream formed in step c) can be heated prior to the implementation of step d). Preferably, said first stream obtained in stage c) can be heated to a temperature between -20 ° C. and 50 ° C., more preferably between -10 ° C. and 50 ° C., in particular between 0 ° C. and 50 ° C. ° C, more particularly between 0 ° C and 40 ° C. In particular, said first stream obtained in step c) can be heated to a temperature between any of the following values: 0, 2, 4, 6, 8, 10, 12, 14, 16, 18, 20 , 22, 24, 26, 28, 30, 32, 34, 36, 38 and 40 ° C. For example, said first stream obtained in step c) can be heated to a temperature between 0 ° C and 2, 4, 6, 8, 10, 12, 14, 16, 18, 20, 22, 24, 26 , 28, 30, 32, 34, 36 or 38 ° C.

Said first stream may be compressed in step d) to form a first compressed stream. Said first compressed stream has the same composition as said first stream as described above. Preferably, said first stream is compressed at a pressure of between 10 and 25 bara, more preferably of 11 to 24 bara, in particular of 12 to 23 bara, more particularly of 13 to 22 bara, and preferably of 14 to 21 bara. , even more privileged from 15 to 20 bara.

According to a particular embodiment, said first compressed stream obtained in step d) can be cooled before being distilled in step e). Preferably, the first compressed stream obtained in step d) can be cooled to a temperature of less than 100 ° C., advantageously less than 95 ° C., preferably less than 80 ° C., more preferably less than 65 ° C., especially less than 50 ° C, more preferably less than 25 ° C.

Said first compressed stream obtained in step d) is distilled in step e) to form a third stream comprising HCl and a fourth stream comprising 2,3,3,3-tetrafluoropropene. The third stream can be recovered at the top of the distillation column. The fourth stream can be recovered at the bottom of the distillation column. According to a particular embodiment, the temperature at the top of the distillation column is between 0 ° C. and -35 ° C., more preferably between -5 ° C. and -30 ° C., in particular between -5 ° C. and -25 ° C. ° C, more particularly between -10 ° C and -20 ° C. The third stream comprising HCl can be recovered in step e) at the top of the distillation column and can be brought to a temperature between -40 ° C and 20 ° C before being purified according to the following steps:

i) catalytic hydrolysis;

ii) washing with an acid solution;

iii) adsorption of impurities with activated carbon;

Preferably, the catalytic hydrolysis step i) is carried out on a bed of activated carbon. The temperature of the catalytic hydrolysis step i) is preferably from 100 to 200 ° C., in particular from 120 to 170 ° C., and more particularly from 130 to 150 ° C. The pressure is preferably 0.5 to 3 barg, especially 1 to 2 barg. Step i) is performed in a dedicated unit for this purpose. The residence time of the first stream in the unit is preferably from 1 s to 1 min, in particular from 2 s to 30 s, more particularly from 4 s to 15 s, and most particularly from 5 s to 10 s. Preferably, the acid solution used during the washing step ii) is a solution of hydrochloric acid and preferably comes from the hydrochloric acid solution collected at the end of the adiabatic or isothermal absorption step. As an acidic solution, it is possible to use a solution of HCl, for example, at a mass concentration ranging from 5 to 60%, especially from 10 to 50%, more preferably from 20 to 45% and in particular from 30 to 35%. The washing with the acidic solution is preferably carried out at a temperature of 5 to 50 ° C, and more particularly of 7 to 40 ° C; and / or at a pressure of 0.1 to 4 barg, preferably from 0.3 to 2 barg, more preferably from 0.5 to 1.5 barg. Preferably, boric acid is added to the acidic solution used for the washing step. An addition of boric acid at the stage of washing with the acid solution makes it possible to complex fluoride ions. For example, the acid solution may contain from 2000 to 8000 ppm of H3BO3. The absorption reaction of the HCl, in step iv), in the water being exothermic, it is preferable to limit the pressure at which this operation is conducted. In general, the pressure is less than 2 barg and preferably less than 1.5 barg. In this way the absorption temperature does not exceed 130 ° C, and preferably 120 ° C. Optionally, the hydrochloric acid solution obtained in step iv) can be contacted with a silica gel.

The fourth stream formed in step e) may comprise, in addition to 2,3,3,3-tetrafluoropropene, at least one of the compounds selected from the group consisting of 2-chloro-3,3,3-trifluoropropene, 1,1 1,2,2-pentafluoropropane, 1,1,1,3,3-pentafluoropropane, 1,3,3,3-tetrafluoropropene, 3,3,3-trifluoropropene, chloromethane 1,1-difluoroethane, chloropentafluoroethane, 1,1,1,2-tetrafluoroethane, trans-1,2,3,3,3-pentafluoropropene and 1-chloro-3,3,3-trifluoropropene. In particular, the fourth stream may comprise, besides 2,3,3,3-tetrafluoropropene, 2-chloro-3,3,3-trifluoropropene, 1,3,3,3-tetrafluoropropene and / or 1,1,1, 2,2-pentafluoropropane. The fourth stream may also include hydrofluoric acid.

According to step f), said fourth stream obtained in step e) and preferably recovered at the bottom of the distillation column can be purified. The purification of said fourth stream may comprise a) a distillation step, a) a decantation step and a) one or more extractive distillation steps. Step f1) may be a distillation intended to reduce the content of 2-chloro-3,3,3-trifluoropropene, 1,3,3,3-tetrafluoropropene and / or 1,1,1,2,2-pentafluoropropane in said fourth stream if these compounds are present therein. Step f1) can be carried out under operating conditions which make it possible to recover at the top of the distillation column a stream comprising 2,3,3,3-tetrafluoropropene and at the bottom of the distillation column a stream comprising a part of 2- chloro-3,3,3-trifluoropropene, 1,3,3,3-tetrafluoropropene and / or 1,1,1,2,2-pentafluoropropane.

As mentioned above, the fourth stream obtained in step e) or the stream obtained in step f1) comprises 2,3,3,3-tetrafluoropropene and also comprises hydrofluoric acid, preferably in weak quantities. Thus, the fourth stream obtained in step e) or the stream obtained in step f1) comprises 2,3,3,3-tetrafluoropropene can be purified by a decantation step f2). In particular, the settling may be carried out at a temperature between 0 ° C and -50 ° C, preferably between -5 ° C and -40 ° C. Decantation makes it possible to form an upper phase comprising HF and a lower phase comprising 2,3,3,3-tetrafluoropropene. Optionally, the lower phase can be brought into contact with water, then treated with a basic solution (for example 20% NaOH or KOH) and then dried. The drying can be carried out in the presence of calcium sulfate, sodium sulfate, magnesium sulfate, calcium chloride, calcium carbonate, silica gel or molecular sieve such as siliporite (for example 3A). The upper phase comprising HF can be recycled in step a).

The stream comprising 2,3,3,3-tetrafluoropropene formed in step f1) and / or the lower phase formed in step f2) may comprise, in addition to 2,3,3,3-tetrafluoropropene, at least one of compounds selected from the group consisting of 1,1,1,2,2-pentafluoropropane and 1,3,3,3-tetrafluoropropene. In particular, the stream comprising 2,3,3,3-tetrafluoropropene formed in step f1) and / or the lower phase formed in step f2) may comprise, in addition to 2,3,3,3-tetrafluoropropene, at least one of the compounds selected from the group consisting of 1,1,1,2 2-pentafluoropropane, 1,3,3,3-tetrafluoropropene, 3,3,3-trifluoropropene, chloromethane, 1,1-difluoroethane, chloropentafluoroethane, 1,1,1,2-tetrafluoroethane and trans-1,2,3 3,3-pentafluoropropene.

Alternatively, the fourth stream obtained in step e) can be purified in step f). Purification of said fourth stream may include a distillation step, a HF removal step, and one or more extractive distillation steps. Step fl ') is identical to step f1) described above. Step f2 ') comprises the following steps:

Preferably, the aqueous solution of hydrofluoric acid used in step i ') is of concentration greater than 40% by weight. In particular, the hydrofluoric acid aqueous solution is of concentration greater than 41%, 42%, 43%, 44%, 45%, 46%, 47%, 48%, 49%, 50%, 51%, 52% 53% 54% 55% 56% 57% 58% 59% 60% 61% 62% 63% 64% 65% 66% 67% 68% 69 % 70% 71% 72% 73% 74% 75% 76% 77% 78% 79% 80% 81% 82% 83% 84% 85% 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94% or 95% by weight. More particularly, the aqueous solution of hydrofluoric acid is of concentration greater than or equal to 50% by weight, or greater than or equal to 60% by weight or greater than or equal to 70% by weight. More particularly, the aqueous solution of hydrofluoric acid may be between any of the values mentioned above. Thus, the hydrofluoric acid aqueous solution may be between 45% and 95% by weight, between 50% and 90% by weight, between 55% and 85% by weight, between 60% by weight and 80% by weight or between 65% by weight and 75% by weight.

Step i ') of the present process allows formation of said second diphasic stream comprising 2,3,3,3-tetrafluoropropene and hydrofluoric acid. Said two-phase current consists of a gas phase G1 and a liquid phase L1. The gas phase can include 2,3,3,3-tetrafluoropropene. Optionally, the gas phase G1 may comprise hydrofluoric acid. When the gas phase G 1 comprises hydrofluoric acid, the content thereof is generally low, preferably less than 5% by weight based on the total weight of said gaseous phase, in particular less than 2% by weight based on the total weight of said gaseous phase, more particularly less than 1% by weight based on the total weight of said gaseous phase. Preferably, said G1 phase comprises in addition to 2,3,3,3-tetrafluoropropene, at least one of the organic compounds selected from the group consisting of 1,1,1,2,2-pentafluoropropane and 1,3,3,3,3-tetrafluoropropene. tetrafluoropropene. Said G1 phase may also comprise, in addition to 2,3,3,3-tetrafluoropropene, at least one of the organic compounds selected from the group consisting of 1,1,1,2,2-pentafluoropropane, 1,3,3,3,3- tetrafluoropropene, 3,3,3-trifluoropropene, chloromethane 1,1-difluoroethane, chloropentafluoroethane, 1,1,1,2-tetrafluoroethane and trans-1,2,3,3,3-pentafluoropropene.

The liquid phase L1 of said two-phase stream may comprise hydrofluoric acid. Said liquid phase L1 may optionally comprise a small amount of 2,3,3,3-tetrafluoropropene, preferably said liquid phase L1 may comprise a 2,3,3,3-tetrafluoropropene content of less than 5% by weight based on total weight of said liquid phase L1, in particular less than 1% by weight ppm based on the total weight of said liquid phase L1, more particularly less than 5000 ppm by weight based on the total weight of said liquid phase L1, in a privileged manner less than 1000 ppm by weight based on the total weight of said liquid phase L1, more preferably less than 500 ppm by weight, particularly preferably less than 100 ppm based on the total weight of said liquid phase L1.

Preferably, said L1 phase further comprises 2,3,3,3-tetrafluoropropene, at least one of the organic compounds selected from the group consisting of 1,1,1,2,2-pentafluoropropane and 1,3,3,3,3-tetrafluoropropene. tetrafluoropropene. Said L1 phase may also comprise, in addition to 2,3,3,3-tetrafluoropropene, at least one of the compounds selected from the group consisting of 1,1,1,2,2-pentafluoropropane, 1,3,3,3-tetrafluoropropene 3,3,3-trifluoropropene, chloromethane 1,1-difluoroethane, chloropentafluoroethane, 1,1,1,2-tetrafluoroethane and trans-1,2,3,3,3-pentafluoropropene.

In this case, said liquid phase L1 may comprise an organic compound content of less than 5% by weight based on the total weight of said liquid phase L1, in particular less than 1% by weight, based on the total weight of said liquid phase L1. , more particularly less than 5000 ppm by weight based on the total weight of said liquid phase L1, advantageously less than 1000 ppm by weight based on the total weight of said liquid phase L1, more preferably less than 500 ppm by weight, particularly preferably less than 100 ppm based on the total weight of said liquid phase ll.

Preferably, the hydrofluoric acid concentration in said liquid phase L1 of said second diphasic stream is greater than the concentration of said hydrofluoric acid aqueous solution used in step i '). Said liquid phase L1 of said second diphasic current may have a hydrofluoric acid concentration of greater than 41% by weight based on the total weight of said liquid phase L1 of said second two-phase current. Advantageously, said liquid phase L1 of said second two-phase current may have a hydrofluoric acid concentration greater than 42%, 43%, 44%, 45%, 46%, 47%, 48%, 49%, 50%, 51%, 52%. %, 53%, 54%, 55%, 56%, 57%, 58%, 59%, 60%, 61%, 62%, 63%, 64%, 65%, 66%, 67%, 68%, 69%, 70%, 71%, 72%, 73%, 74%, 75%, 76%, 77%, 78%, 79%, 80%, 81%, 82%, 83%, 84%, 85% , 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94% or 95% by weight based on the total weight of said liquid phase L1 of said second two-phase current. Preferably, said liquid phase L1 of said second two-phase stream may have a hydrofluoric acid concentration of between 45% and 95% by weight, between 50% and 90% by weight, between 55% and 85% by weight, and between 60% by weight. weight and 80% by weight or between 65% by weight and 75% by weight while being greater than the concentration of said aqueous hydrofluoric acid solution used in stage i ').

Preferably, the hydrofluoric acid aqueous solution used in step i ') is at a temperature of between -20 ° C. and 80 ° C. before being brought into contact with the said first stream, advantageously between -15 ° C. and 70 ° C. C., preferably between -10 ° C. and 60 ° C., more preferably between -5 ° C. and 50 ° C., in particular between -5 ° C. and 40 ° C., more particularly between 0 ° C. and 30 ° C. Thus, in a particularly preferred embodiment, the temperature of the aqueous hydrofluoric acid solution used in step i '), before it is brought into contact with said first stream, can be 0 ° C, 1 ° C, 2 ° C, 3 ° C, 4 ° C, 5 ° C, 6 ° C, 7 ° C, 8 ° C, 9 ° C, 10 ° C, 11 ° C, 12 ° C, 13 ° C, 14 ° C 15 ° C 16 C 17 C 18 C 19 C 20 C 21 C 22 C 23 C 24 C 25 C 26 C 27 ° C, 28 ° C, 29 ° C or 30 ° C. The implementation of said aqueous solution of hydrofluoric acid at the temperatures mentioned above is intended to control the exothermicity occurring during the contacting thereof with said first stream.

As mentioned above, step ii ') of the method according to the present invention implements the storage of said second two-phase current in a buffer tank, said second two-phase current consisting of said liquid phase L1 and said gas phase G1 as described above.

As mentioned above, step iii ') of the method according to the present invention implements, the passage of said gas phase G1 of said second two-phase current in an absorption column fed countercurrently with an aqueous stream to form a gaseous stream G2 comprising 2,3,3,3-tetrafluoropropene and an aqueous stream L2 comprising HF.

Preferably, the flow rate of the aqueous stream used in step iii ') is determined as a function of the amount of hydrofluoric acid contained in said fourth stream. Thus, the ratio between the flow rate of the aqueous flow expressed in kg / h feeding the absorption column in step (iii) and the amount of hydrofluoric acid in said fourth flow expressed in kg / h is between 0.05 and 1.22. Advantageously, the ratio between the flow rate of the aqueous flow expressed in kg / h feeding the absorption column in step iii ') and the quantity of hydrofluoric acid in the said fourth flow expressed in kg / h can be between 0, 11 and 1.00, preferably between 0.18 and 0.82, more preferably between 0.25 and 0.67, in particular between 0.33 and 0.54. Thus the ratio between the flow rate of the aqueous flow expressed in kg / h feeding the absorption column in step iii ') and the amount of hydrofluoric acid in said fourth flow expressed in kg / h may be 0.25, 0.26, 0.27, 0.28, 0.29, 0.30, 0.31, 0.32, 0.33, 0.34, 0.35, 0.36, 0.37, 0, 38, 0.39, 0.40, 0.41, 0.42, 0.43, 0.44, 0.45, 0.46, 0.47, 0.48, 0.49, 0.50, 0.51, 0.52, 0.53, 0.54, 0.55, 0.56, 0.57, 0.58, 0.59, 0.60, 0.61, 0.62, 0, 63, 0.64, 0.65, 0.66, 0.67, 0.68, 0.69 or 0.70.

An additional aqueous stream corresponding to the vaporized water fraction at the top of said absorption column may also supply said column. The aqueous stream as described above is different from said additional aqueous stream linked to the vaporized water fraction at the top of the column and does not include it.

According to a preferred embodiment, said absorption column implemented in step iii ') comprises at least one absorption stage. Advantageously, said absorption column implemented in step iii ') comprises at least two absorption stages. Preferably, said absorption column implemented in step iii ') comprises at least three absorption stages. Said absorption column implemented in step iii ') may thus comprise two, three, four, five, six, seven, eight, nine, ten, eleven, twelve, thirteen, fourteen or fifteen absorption stages.

The implementation of an absorption column having at least one absorption stage, advantageously at least two absorption stages, preferably at least three absorption stages, makes it possible to obtain a G 2 stream having a low content. in hydrofluoric acid. Advantageously, said stream G2 comprises less than 1000 ppm of hydrofluoric acid by weight based on the total weight of said stream G2, preferably less than 900 ppm of hydrofluoric acid, more preferably less than 800 ppm of hydrofluoric acid, in particular less 700 ppm of hydrofluoric acid, more particularly less than 600 ppm of hydrofluoric acid, preferably less than 500 ppm of hydrofluoric acid, even more preferred less than 400 ppm of hydrofluoric acid, preferably less favored 300 ppm of hydrofluoric acid, particularly preferably less than 200 ppm of hydrofluoric acid, more particularly preferred less than 100 ppm of hydrofluoric acid. Thus, said stream G2 may have a hydrofluoric acid content of between 1 and 200 ppm, between 5 and 190 ppm, between 10 and 180 ppm, between 15 and 170 ppm, between 20 and 160 ppm, between 25 and 150 ppm or between 30 and 140 ppm by weight based on the total weight of said G2 stream.

Preferably, at least 80% by weight of the hydrofluoric acid optionally present in said gas phase G1 of said second two-phase current is absorbed by the first absorption stage of said absorption column, in particular at least 85% by weight of the hydrofluoric acid optionally present in said gas phase G1 of said second diphasic current is absorbed by the first absorption stage of said absorption column, more particularly at least 90% by weight of the hydrofluoric acid that may be present in said gaseous phase Gl of said second diphasic current is absorbed by the first absorption stage of said absorption column.

Preferably, said aqueous stream can be introduced at least at the head of the absorption column.

Preferably, said G1 phase and said G2 phase comprise, in addition to 2,3,3,3-tetrafluoropropene, at least one of the compounds chosen from the group consisting of 1,1,1,2,2-pentafluoropropane and 1,3,3,3-tetrafluoropropene. , 3-tetrafluoropropene. Said G1 phase and said G2 phase may also comprise, in addition to 2,3,3,3-tetrafluoropropene, at least one of the compounds selected from the group consisting of 1,1,1,2,2-pentafluoropropane, 1,3,3 , 3-tetrafluoropropene, 3,3,3-trifluoropropene, chloromethane 1,1-difluoroethane, chloropentafluoroethane, 1,1,1,2-tetrafluoroethane and trans-1,2,3,3,3-pentafluoropropene.

According to a preferred embodiment, said stream L2 is in the form of an aqueous solution of hydrofluoric acid. Advantageously, said stream L2 is a solution of hydrofluoric acid with a concentration of less than 30% by weight based on the total weight of said stream L2. Preferably, said stream L2 is a hydrofluoric acid concentration solution less than 25% by weight based on the total weight of said L2 stream. In particular, said stream L2 is a solution of hydrofluoric acid with a concentration of between 5 and 25% by weight based on the total weight of said stream L2, more particularly between 10 and 20% by weight based on the total weight of said stream L2. . According to a preferred embodiment, said stream L2 is recycled in stage ii '). Said stream L2 is thus mixed with liquid phase L1.

According to a preferred embodiment, said method also comprises the steps of:

Iv ') neutralizing said G2 stream obtained in step iii') with an aqueous alkaline solution to form a neutralized stream G3, and

v ') drying said neutralized G3 stream obtained in step iv'), preferably on molecular sieve to form a neutralized and dried G4 stream.

According to a preferred embodiment, said aqueous alkaline solution may be an aqueous solution of hydroxide of an alkali metal or alkaline earth metal. The aqueous alkaline solution may be an aqueous solution of sodium hydroxide, potassium hydroxide, calcium hydroxide or magnesium hydroxide or a mixture thereof. Preferably, said aqueous alkaline solution has a concentration of between 5 and 50% by weight based on the total weight of said alkaline aqueous solution. Advantageously, said alkaline aqueous solution has a concentration of at least 5%, at least 6%, at least 7%, at least 8%, at least 9%, at least 10%. at least 11%, at least 12%, at least 13%, at least 14%, at least 15%, at least 16% or at least weight based on the total weight of said alkaline aqueous solution; and not more than 50%, not more than 48%, not more than 46%, not more than 44%, not more than 42%, not more than 40%, not more than 38%, not more than 36%, not more than 34%, not more than 32%, not more than 30%, not more than 28%, not more than 26%, not more than 24%, at most 22% by weight based on the total weight of said alkaline aqueous solution.

Said neutralized stream G3 formed in step iv ') preferably comprises 2,3,3,3-tetrafluoropropene and optionally any of the organic compounds described above. The hydrofluoric acid content in said neutralized stream G3 is lower than the hydrofluoric acid content of said stream G2, before its neutralization. Said neutralized stream G3 formed in step iv ') may also contain water.

Said neutralized stream G3 formed in step iv ') can thus be dried in step v') of the present process. Preferably, said neutralized stream G3 formed in step iv ') is dried on molecular sieve. For example, said neutralized G3 stream formed in step iv ') is dried on 3A molecular sieve, such as siliporite. Step ν ') of the present process allows the formation of a neutralized and dried G4 stream comprising 2,3,3,3-tetrafluoropropene and optionally any of the organic compounds described above. Said G4 stream can then be compressed and liquefied at a pressure of at most 8 bara to form a compressed G5 stream in which 2,3,3,3-tetrafluoropropene and optionally any of the organic compounds described above are liquid form.

According to a preferred embodiment, the liquid phase resulting from the mixing of said liquid phase L1 with said liquid phase L2 is recycled to step i '). The liquid phase resulting from the mixing of said liquid phase L1 with said liquid phase L2 may have a hydrofluoric acid concentration greater than 41% by weight based on the total weight of the liquid phase resulting from the mixing of said liquid phase L1 with said liquid phase L2. Advantageously, the liquid phase resulting from the mixing of said liquid phase L1 with said liquid phase L2 may have a hydrofluoric acid concentration greater than 42%, 43%, 44%, 45%, 46%, 47%, 48%, 49% 50% 51% 52% 53% 54% 55% 56% 57% 58% 59% 60% 61% 62% 63% 64% 65% 66 % 67% 68% 69% 70% 71% 72% 73% 74% 75% 76% 77% 78% 79% 80% 81% 82% 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94% or 95% by weight based on the total weight of the resulting liquid phase mixing said liquid phase L1 with said liquid phase L2. Preferably, the liquid phase resulting from mixing said liquid phase L1 with said liquid phase L2 may have a hydrofluoric acid concentration of between 45% and 95% by weight, between 50% and 90% by weight, between 55% and 85% by weight. % by weight, between 60% by weight and 80% by weight or between 65% by weight and 75% by weight based on the total weight of the liquid phase resulting from the mixing of said liquid phase L1 with said liquid phase L2.

According to another preferred embodiment, the liquid phase resulting from the mixing of said liquid phase L1 with said liquid phase L2 is distilled to form a stream L3, preferably at the top of the distillation column. Advantageously, said stream L3 comprises hydrofluoric acid containing less than 3000 ppm of water, preferably less than 2000 ppm of water, more preferably less than 1000 ppm of water, in particular less than 500 ppm of water, more particularly less than 200 ppm water, preferably less than 100 ppm water, more preferably less than 50 ppm water based on the total weight of L3 current. Said stream L3 may also comprise less than 50 ppm of hydrochloric acid, advantageously less than 45 ppm of hydrochloric acid, preferably less than 40 ppm of hydrochloric acid, more preferably less than 35 ppm of hydrochloric acid, in particular less 30 ppm hydrochloric acid, more particularly less than 20 ppm of hydrochloric acid based on the total weight of the L3 current. Said stream L3 may also comprise less than 50 ppm of organic compounds, advantageously less than 45 ppm of organic compounds, preferably less than 40 ppm of organic compounds, more preferably less than 35 ppm of organic compounds, in particular less than 30 ppm of organic compounds. organic compounds, more particularly less than 20 ppm of organic compounds based on the total weight of L3 current. An organic compound is a compound comprising at least one carbon atom.

In addition, the distillation of said liquid phase L1 of said second two-phase current forms a stream L4, preferably at the bottom of the distillation column, comprising hydrofluoric acid in the form of an aqueous solution with a concentration of less than 50% by weight. Advantageously, said stream L4 comprising hydrofluoric acid in the form of an aqueous solution of concentration less than 50% by weight, 49% by weight, 48% by weight, 47% by weight, 46% by weight, 45% by weight. weight, 44% by weight, 43% by weight, 42% by weight based on the total weight of said L4 stream. Preferably, said stream L4 comprising hydrofluoric acid in the form of an aqueous solution of concentration greater than 20% by weight based on the total weight of said stream L4. In particular, said stream L4 comprising hydrofluoric acid in the form of an aqueous solution of higher concentration 21% by weight, 22% by weight, 23% by weight, 24% by weight, 25% by weight, 26% by weight. weight, 27% by weight, 28% by weight, 29% by weight, 30% by weight, 31% by weight, 32% by weight, 33% by weight, 34% by weight, 35% by weight based on weight total of said current L4. Said L4 stream may be marketed or destroyed by neutralization.

When said lower phase or said G2, G3, G4 or G5 phase comprises 2,3,3,3-tetrafluoropropene, 1,1,1,2,2-pentafluoropropane and 1,3,3,3-tetrafluoropropene, the latter can be distilled by extractive distillation to form a stream comprising 2,3,3,3-tetrafluoropropene and 1,1,1,2,2-pentafluoropropane; and a stream comprising 1,3,3,3-tetrafluoropropene. The extractive distillation of said lower phase or said G2, G3, G4 or G5 phase can be carried out in the presence of an organic extraction agent. Said organic extractant may be selected from the group consisting of ethylamine, isopropylamine, diethylether, n-propylamine, diethylamine, propanone, methylacetate, butanone, diethoxymethane, isopropylacetate, 3-pentylamine, 2-methoxyethanamine, tert-butylacetate, 1, 4-dioxane, 1,1-diethoxyethane, trimethoxymethane, n-pentylamine, 1,3-dioxane, sec-butylacetate, 1,2-diaminoethane, 1-methoxy-2-propanol, 1,2-propanediamine, n-butylacetate, 2-methoxy-1-propanol, hexanal. Preferably, said organic extraction agent may be selected from the group consisting of ethylamine, isopropylamine, diethylether, n-propylamine, diethylamine, diethoxymethane, isopropylacetate, 3-pentylamine, 2-methoxyethanamine, tert-butylacetate, 1,4-dioxane, 1,1-diethoxyethane, trimethoxymethane, n-pentylamine, 1,3-dioxane, sec-butylacetate, 1,2-diaminoethane, 1-methoxy-2-propanol, 1,2-propanediamine, n-butylacetate, 2-methoxy-1-propanol, hexanal.

Alternatively, when said lower phase or said G2, G3, G4 or G5 phase comprises 2,3,3,3-tetrafluoropropene, 1,1,1,2,2-pentafluoropropane, 1,3,3,3-tetrafluoropropene and minus one of the compounds selected from the group consisting of 3,3,3-trifluoropropene, chloromethane, 1,1-difluoroethane, chloropentafluoroethane, 1,1,1,2-tetrafluoroethane and trans-1,2,3,3,3- pentafluoropropene; this can be purified by extractive distillation. The extractive distillation of said lower phase or said G2, G3, G4 or G5 phase can be carried out in the presence of an organic extraction agent. Said organic extractant may be selected from the group consisting of ethylamine, isopropylamine, diethylether, n-propylamine, diethylamine, propanone, methylacetate, butanone, diethoxymethane, isopropylacetate, 3-pentylamine, 2-methoxyethanamine, tert-butylacetate, 1, 4-dioxane, 1,1-diethoxyethane, trimethoxymethane, n-pentylamine, 1,3-dioxane, sec-butylacetate, 1,2-diaminoethane, 1-methoxy-2-propanol, 1,2-propanediamine, n-butylacetate, 2-methoxy-1-propanol, hexanal. Preferably, said organic extractant may be selected from the group consisting of ethylamine, isopropylamine, diethylether, n-propylamine, diethylamine, diethoxymethane, isopropylacetate, 3-pentylamine, 2-methoxyethanamine, tert-butylacetate, 1,4-dioxane , 1,1-diethoxyethane, trimethoxymethane, n-pentylamine, 1,3-dioxane, sec-butylacetate, 1,2-diaminoethane, 1-methoxy-2-propanol, 1,2-propanediamine, n-butylacetate, 2-methoxy 1-propanol, hexanal. Thus, the extractive distillation makes it possible to obtain a stream comprising 2,3,3,3-tetrafluoropropene and 1,1,1,2,2-pentafluoropropene and a stream comprising 1,3,3,3-tetrafluoropropene. the organic extractant and said at least one of the compounds selected from the group consisting of 3,3,3-trifluoropropene, chloromethane, 1,1-difluoroethane, chloropentafluoroethane, 1,1,1,2-tetrafluoroethane and trans -l, 2,3,3,3-pentafluoropropene.

Said stream comprising 2,3,3,3-tetrafluoropropene and 1,1,1,2,2-pentafluoropropane is then purified, for example by distillation, to form a stream comprising 2,3,3,3-tetrafluoropropene and a current comprising 1,1,1,2,2-pentafluoropropane, the latter being optionally recycled in step a). Figure 1 schematically shows a method according to a particular embodiment of the present invention. Compound (I) is, for example, 1,1,1,2,3-pentachloropropane. A stream of compound (I) is introduced via line 1 into the reaction device 3. A flow of hydrofluoric acid is introduced via line 2 into the reaction device 3. The reaction device 3 may comprise one or more reactors. The stream of products resulting from the reaction between the compound (I) and THF comprises in particular HCl, HF and 2,3,3,3-tetrafluoropropene. The flow of products resulting from the reaction between the compound (I) and THF is transferred from the reaction device 3 to a cooling device 5 via a pipe 4. The flow of products resulting from the reaction between the compound (I) and THF is and cooled to a temperature of 0 ° C to 70 ° C before being introduced into a distillation column 6 via a pipe 12. The distillation column 6 is configured, as explained above, so as to allow the separation between on the one hand hydrochloric acid and 2,3,3,3-tetrafluoropropene and on the other hand hydrofluoric acid. The HF stream is recovered at the bottom of distillation column 6 and recycled to the reaction device 3 via line 17. The stream comprising 2,3,3,3-tetrafluoropropene and hydrochloric acid is recovered at the top of the column. distillation device to be routed via a pipe 13 to a compressor 7. The compressor compresses the stream comprising 2,3,3,3-tetrafluoropropene and hydrochloric acid at a pressure of between 10 and 25 bara. The stream thus compressed is fed through line 15 to distillation column 8. This is configured to separate 2,3,3,3-tetrafluoropropene and hydrochloric acid. The hydrochloric acid is recovered at the top of the distillation column 8 to be conveyed to a purification device 10 via line 14. The hydrochloric acid purification device 10 is as described above in the present application. The 2,3,3,3-tetrafluoropropene is recovered at the bottom of the distillation column to be conveyed via line 16 to a distillation column 9. The distillation column 9 is intended to separate 2,3,3,3-tetrafluoropropene. 1,1,1,2,2-pentafluoropropene possibly present in the stream of products from the reaction device. The 2,3,3,3-tetrafluoropropene is recovered at the top of the distillation column to be conveyed to a purification device 11 via line 18 'described below. The 1,1,1,2,2-pentafluoropropene recovered at the bottom of the distillation column is recycled to the reaction device 3 via line 18. The purification device 11 comprises in particular a device for removing the HF and one or more columns. distillation system capable of purifying the stream comprising 2,3,3,3-tetrafluoropropene of impurities which it may contain, such as, for example, 1,1,1,2,2-pentafluoropropane and / or 1,3 , 3,3-tetrafluoropropene. this is 2 purification device 11 comprises a device for removing HF 19 to separate on one side 2,3,3,3-tetrafluoropene, 1,1,1,2,2- pentafluoropropane and 1,3,3,3-tetrafluoropropene, if present, and on the other hand residual HF. The residual HF can be recycled to the reaction device 3 (not shown). The device for removing HF 19 may be suitable for allowing the decantation of HF or the absorption of HF as described below. The stream comprising 2,3,3,3-tetrafluoropropene, 1,1,1,2,2-pentafluoropropane and 1,3,3,3-tetrafluoropropene is passed to a distillation column 20 via line 23. The distillation column 20 is an extractive distillation column. An extractant is added to the stream comprising 2,3,3,3-tetrafluoropene, 1,1,1,2,2-pentafluoropropane and 1,3,3,3-tetrafluoropropene. A stream comprising 2,3,3,3-tetrafluoropene and 1,1,1,2,2-pentafluoropropane is recovered at the top of distillation column 20 and is conveyed via line 22 to a distillation column 21 allowing separation between 2,3,3,3-tetrafluoropene and 1,1,1,2,2-pentafluoropropane. A stream 27 comprising 2,3,3,3-tetrafluoropene is recovered at the top of the distillation column. A stream 28 comprising 1,1,1,2,2-pentafluoropropane is recovered at the bottom of the distillation column; the latter can be recycled to the reaction device 3. The stream 24 recovered at the bottom of the distillation column 20 comprises the organic extraction agent and 1,3,3,3-tetrafluoropropene. These are separated, for example by distillation, to form a stream 26 comprising 1,3,3,3-tetrafluoropropene. The organic extraction agent is recycled at 25.

Figure 3 shows schematically a device for removing hydrofluoric acid 19 according to a particular embodiment, that is to say by absorption of HF. Stream 31 comprises 2,3,3,3-tetrafluoropropene, 1,1,1,2,2-pentafluoropropane, 1,3,3,3-tetrafluoropropene and HF, and is equivalent to the stream from the top of the column. distillation 9 illustrated in Figure 1 and Figure 2. This feeds a device 32 in which it is brought into contact with a solution of hydrofluoric acid 3 or a solution from the device 34 via the pipe 50 having a varying concentration between 65 and 75% by weight. The device 32 may for example be a hydrolaver. Contacting the hydrofluoric acid solution 3 or a solution from the device 34 via the pipe 50 and the stream 31 generates the formation of a two-phase current which is routed to a storage device 34 via the pipe 43. storage device 34 makes it possible to separate the two-phase current into a gaseous phase and a liquid phase. The gaseous phase of said two-phase current is conveyed via line 44 to the absorption column 33 comprising three absorption stages 51a, 51b and 51c. The column absorption 33 is also supplied by an aqueous stream 37. In this embodiment, the aqueous stream 37 feeds the absorption column 33 at the head of the absorption column 33, that is to say above the three absorption stages 51a-51c. Alternatively, the gas stream 37 can feed the absorption column 33 above each of the absorption stages 51a-51c. A gaseous stream comprising 2,3,3,3-tetrafluoropropene, 1,1,1,2,2-pentafluoropropane, 1,3,3,3-tetrafluoropropene is extracted at the top of absorption column 33 via line 46 to In addition, at the bottom of the absorption column 33, an aqueous solution of hydrofluoric acid is recycled to the storage device 34 via the line 45. The alkaline solution 38, for example an alkaline solution of 20% NaOH feeds the neutralizer 35 through line 49. The neutralized stream is discharged through line 47 and recovered at 40 to be dried on 3A molecular sieve. The latter can therefore be compressed and liquefied at a pressure of at most 8 bara. The stream recovered at 40 can supply the distillation column 20 described in FIG. 2 via line 23. A spent alkaline solution 39 can be extracted from the neutralization device 35 to be recycled via lines 48 and 49 or evacuated via the pipe. 48 for further processing. The liquid phase of the two-phase stream or the mixture resulting from the liquid phase of said two-phase stream and the aqueous hydrofluoric acid solution from the base of the absorption column 33 stored in the storage device 34 is conveyed to a distillation column 36 via the pump 52 and the pipe 53 to form the stream L3 recovered at the top of the distillation column 41 and the stream L4 recovered at the bottom of the distillation column 42. The pump 52 can also be configured to convey the liquid phase of the two-phase stream. stored in the storage device 34 to the device 32 via the pipe 50. The pump 52 is thus configured to allow the supply of the distillation column 36 and the device 32 alternately or simultaneously, preferably simultaneously .

The present invention thus makes it possible to implement a process for producing 2,3,3,3-tetrafluoropropene that is simpler and more economical.

Claims

claims

A process for producing 2,3,3,3-tetrafluoropropene comprising the steps of:

a) contacting, in the gas phase, a compound of formula (I) CH ( _n + 2) (X) m-CH _p (X) (n + 1) -CX (3+ _P -m) where X independently represents F or Cl; n, m, p are independently of one another 0 or 1 with (n + m) = 0 or 1, (n + p) = 0 or 1 and (mp) = 0 or 1, at least one X being Cl with hydrofluoric acid to obtain a product stream comprising 2,3,3,3-tetrafluoropropene, HCl and HF,

f) purifying said fourth stream obtained in step e),

2. Method according to the preceding claim characterized in that said first current obtained in step c) is heated prior to the implementation of step d).

3. Method according to the preceding claim characterized in that said first stream obtained in step c) is heated to a temperature between 0 ° C and 40 ° C.

4. Method according to any one of claims characterized in that in step d), said first stream is compressed at a pressure of between 10 and 25 bara, preferably between 15 and 20 bara.

5. Method according to any one of the preceding claims characterized in that the first compressed stream obtained in step d) is cooled before being distilled.

6. Method according to the preceding claim characterized in that the first compressed stream obtained in step d) is cooled to a temperature below 50 ° C.

7. Method according to any one of the preceding claims, characterized in that in step e), the temperature at the top of the distillation column is between 0 ° C and -35 ° C.

8. Process according to any one of the preceding claims, characterized in that the third stream comprising HCl is recovered in stage e) at the top of the distillation column and is brought to a temperature of between -40 ° C and 20 ° C. before being purified according to the following steps:

i) catalytic hydrolysis;

ii) washing with an acid solution;

iii) adsorption of impurities with activated carbon;

9. Process according to any one of the preceding claims, characterized in that the compound of formula (I) is selected from the group consisting of 1,1,1,2,3-pentachloropropane, 1,1,2,3-tetrachloropropene , 2,3,3,3-tetrachloropropene, 2-chloro-3,3,3-trifluoropropene and 2-chloro-1,1,1,2-tetrafluoropropane, 1,2-dichloro-3,3,3-trifluoropropane and 1,1,1,2,2-pentachloropropane, or a mixture thereof; and step a) is carried out in the presence or absence of a catalyst to produce a product stream comprising 2,3,3,3-tetrafluoropropene, HCl, HF and also at least one of the compounds selected from the group consisting of 2-chloro-3,3,3-trifluoropropene, 1,1,1,2,2-pentafluoropropane, 1,1,1,3,3-pentafluoropropane, 1,3,3,3-tetrafluoropropene, 3, 3,3-trifluoropropene, chloromethane 1,1-difluoroethane, chloropentafluoroethane, 1,1,1,2-tetrafluoroethane, trans-1,2,3,3,3-pentafluoropropene and 1-chloro-3,3,3-trifluoropropene .

10. Process according to any one of the preceding claims, characterized in that the fourth stream comprising 2,3,3,3-tetrafluoropropene is purified by decantation at a temperature of temperature between -50 ° C and 0 ° C to form a lower phase comprising 2,3,3,3-tetrafluoropropene and a higher phase comprising HF, optionally recycled in step a).

11. Method according to any one of claims 1 to 9 characterized in that the fourth stream comprising 2,3,3,3-tetrafluoropropene is purified in step f) by the following steps i ') contacting said fourth running with an aqueous solution of hydrofluoric acid of concentration greater than 40% to form a biphasic current comprising 2,3,3,3-tetrafluoropropene and HF,

ii ') storing said two-phase current in a buffer tank, said second stream consisting of a gas phase G1 and a liquid phase L1,

12. The method of claim 10 or claim 11 characterized in that said lower or said G1 phase and said current G2 also include, in addition to 2,3,3,3-tetrafluoropropene, 1,1,1,2,2-pentafluoropropane and 1,3,3,3-tetrafluoropropene; the lower phase, said gas phase G1 or said G2 stream is distilled by extractive distillation to form a stream comprising 2,3,3,3-tetrafluoropropene and 1,1,1,2,2-pentafluoropropane and a stream comprising 1.3 3,3-tetrafluoropropene; preferably the extractive distillation is carried out in the presence of an organic extractant selected from the group consisting of ethylamine, isopropylamine, diethylether, n-propylamine, diethylamine, diethoxymethane, isopropylacetate, 3-pentylamine, 2-methoxyethanamine, tert-butylacetate , 1,4-dioxane, 1,1-diethoxyethane, trimethoxymethane, n-pentylamine, 1,3-dioxane, sec-butylacetate, 1,2-diaminoethane, 1-methoxy-2-propanol, 1,2-propanediamine, n butylacetate, 2-methoxy-1-propanol, hexanal.