The present invention relates to an azeotropic composition comprising trifluoropropyne. The present invention also relates to a process for purifying a composition comprising trifluoropropyne and 2,3,3,3-tetrafluoropropene.

BACKGROUND OF THE INVENTION

The fluorinated compounds such as hydrofluoroolefins are produced via reactions of fluorination and dehydrofluorination of hydrofluorocarbons, of hydrochlorofluorocarbons or HCFCs. These reactions are generally carried out in the presence of hydrofluoric acid (HF) as fluorination agent. For example, WO2013 / 088195 describes the preparation of 2,3,3,3-tetrafluoropropene.

During these reactions, hydrochloric acid is produced. The latter can be separated from the other reaction products by means of a distillation column to ultimately recover hydrochloric acid without fluorinated impurities. Indeed, the recovered hydrochloric acid in gaseous form is then absorbed into water to produce aqueous solutions of hydrochloric acid which must have a low content of fluorinated products.

In addition to hydrochloric acid, light organic impurities can also be formed in the fluorination reactions. In particular, in the production of 2,3,3,3-tetrafluoropropene (1234yf) light organic impurities are for example trifluoropropyne, trifluoromethane, pentafluoroethane, chloropentafluoroethane and 1,1,1-trifluoroethane. These light organic impurities are extracted from the desired product during its purification by means of a distillation column dedicated to this purpose. Removing these small organic impurities is usually accompanied by a loss of the desired product with a boiling point is often close to that of light organic impurities. This may therefore reduce the overall efficiency of the process. Typically,

There is always a need to implement a fluorination method for minimizing the losses of the desired product during the purification process.

Summary of the Invention

According to a first aspect of the present invention, an azeotropic composition or quasi-azeotropic comprising hydrochloric acid and trifluoropropyne is provided.

According to a particular embodiment, said azeotropic composition or quasi-azeotropic comprises from 85 wt% to 99.999% by weight of hydrochloric acid and 0.001% by weight to 15% by weight of trifluoropropyne based on the total weight of the composition ; preferably said composition has a boiling point of - 60 ° C to 0 ° C; preferably at a pressure between 3 and 26 bara.

According to a preferred embodiment, said composition also comprises pentafluoroethane, chloropentafluoroethane and hexafluoroethane.

The applicant has established that the implementation of azeotropic compositions or quasi-azeotropic above facilitates purification of 2,3,3,3-tetrafluoropropene, particularly promotes the separation of 2,3,3,3-tetrafluoropropene and the trifluoropropyne which have relatively close boiling points.

In a second aspect, the invention provides a process for separating 2,3,3,3-tetrafluoropropene and trifluoropropyne from a composition A comprising 2,3,3,3-tetrafluoropropene and trifluoropropyne, said method comprising the steps of: i) contacting said composition with an inorganic compound to form a composition B,

ii) the composition of B distillation to form a first stream comprising the Bl trifluoropropyne and the inorganic compound; B2 and a second stream comprising 2,3,3,3-tetrafluoropropene.

According to a preferred embodiment, the trifluoropropyne and the inorganic compound forms an azeotropic or near-azeotropic composition.

According to a preferred embodiment, the inorganic compound is hydrochloric acid. According to a preferred embodiment, the amount of trifluoropropyne in said second stream B2 is less than the initial amount of trifluoropropyne in composition B; advantageously the amount trifluoropropyne B2 in the second stream can be less than 10% of the initial amount of trifluoropropyne contained in the composition B; preferably said second stream B2 comprises less than 1000 ppm of trifluoropropyne, more preferably said second B2 stream comprises less than 500 ppm of trifluoropropyne, in particular said second B2 stream comprises less than 100 ppm, more particularly said second stream B2 comprises less 50 ppm; privileged manner said second stream B2 is devoid of trifluoropropyne.

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

A) fluorination in the presence of a catalyst of a compound of formula (I) CX (Y) 2-CX (Y) m - CH m XY where X and Y independently represent a hydrogen, fluorine or chlorine and m = 0 or 1; and / or catalytic fluorination in the presence of a catalyst of a compound of formula (CX n Y 3-n) CHpXi pCH- m X 2-m (II) wherein X is independently of each other Cl, F, I or Br ; Y is independently of each other H, Cl, F, I or Br; n is 1, 2 or 3; and m is 0, 1 or 2; and p is 0 or 1;

B) recovering a stream C comprising 2,3,3,3-tetrafluoropropene, hydrochloric acid and trifluoropropyne;

C) distilling the stream C recovered in step B) to form a first stream D comprising hydrochloric acid and trifluoropropyne; E and a second stream comprising 2,3,3,3-tetrafluoropropene.

According to a preferred embodiment, the first stream D comprising hydrochloric acid and trifluoropropyne is recovered distillation column.

According to a preferred embodiment, the amount of trifluoropropyne in said second stream E is smaller than the initial quantity of trifluoropropyne in stream C; advantageously the amount trifluoropropyne in the second stream E can be less than 10% of the initial amount of trifluoropropyne contained in the stream C; preferably said second stream E comprises less than 1000 ppm of trifluoropropyne, more preferably said second stream E comprises less than 500 ppm of trifluoropropyne, in particular said second stream E comprises less than 100 ppm, more particularly said second stream E comprises less 50 ppm; privileged manner said second stream E is devoid of trifluoropropyne ..

According to a preferred embodiment, the first stream D comprises an azeotropic composition or quasi-azeotropic comprising 85% by weight to 99.999% by weight of hydrochloric acid and 0.001% by weight to 15% by weight based on the trifluoropropyne total weight of the composition; preferably said composition has a boiling point of -60 ° C to 0 ° C preferably at a pressure between 3 and 26 bara.

According to a preferred embodiment, the flow C recovered in step B) and the first flow D also include pentafluoroethane (F125), chloropentafluoroethane (F115) or hexafluoroethane (F116).

Preferably, the flow C recovered in step B) and the first flow D also include difluoromethane (32), 1,1,1-trifluoroethane (143a) and / or hydrofluoric acid.

According to a preferred embodiment, the stream C and the second stream E also include 1,1,1,2,2-pentafluoropropane, 1,3,3,3-tetrafluoropropene and impurities having a lower boiling point to the boiling point of 2,3,3,3-tetrafluoropropene; said second stream E is distilled to form a G stream comprising 2,3,3,3-tetrafluoropropene, 1,1,1,2,2-pentafluoropropane and 1,3,3,3-tetrafluoropropene; and H a ​​stream comprising impurities having a boiling point below the boiling point of 2,3,3,3-tetrafluoropropene.

The implementation of an azeotropic composition or quasi-azeotropic trifluoropropyne and hydrochloric acid makes it easy to purify 2,3,3,3-tetrafluoropropene of trifluoropropyne and produces hydrochloric acid during the reaction fluoridation. Loss of 2,3,3,3-tetrafluoropropene are minimized by eliminating the at least the hydrochloric acid trifluoropropyne has a relatively close boiling point of one of 2,3,3,3-tetrafluoropropene.

Detailed Description of the Invention

The invention is now described in more detail and not limited to the following description.

According to a first aspect, the invention provides an azeotropic composition or quasi-azeotropic comprising hydrochloric acid and trifluoropropyne.

The term "azeotropic composition" refers to a liquid mixture of two or more compounds that behave as a single substance, and which boils at fixed temperature keeping an identical composition in liquid phase to the gas phase. The term "quasi-azeotropic composition" refers to a liquid mixture of two or more compounds having a constant boiling or which tends not to split when subjected to boiling or evaporation.

According to a preferred embodiment, the composition comprises from 85 wt% to 99.999% by weight of hydrochloric acid and 0.001% by weight to 15% by weight of trifluoropropyne based on the total weight of the composition. Advantageously, the composition comprises 87% by weight to 99.999% by weight of hydrochloric acid and 0.001% by weight to 13% by weight of trifluoropropyne based on the total weight of the composition. Preferably, the composition comprises from 88 wt% to 99.999% by weight of hydrochloric acid and 0.001% by weight to 12% by weight of trifluoropropyne based on the total weight of the composition. In particular, the composition comprises from 90% by weight to 99.999% by weight of hydrochloric acid and 0.001% by weight to 10% by weight of trifluoropropyne based on the total weight of the composition.

According to a preferred embodiment, said composition has a boiling point of -60 ° C to 0 ° C, preferably said composition has a boiling point from -55 ° C to 0 ° C, preferably said composition has a boiling point of -50 ° C to -5 ° C.

According to a preferred embodiment, said composition has a boiling point of -60 ° C to 0 ° C, preferably said composition has a boiling point from -55 ° C to 0 ° C, preferably said composition has a boiling point of -50 ° C to -5 ° C at a pressure of 3 to 26 bara.

Advantageously, said composition has a boiling point of -60 ° C to 0 ° C, preferably said composition has a boiling point from -55 ° C to 0 ° C, preferably said composition has a boiling point of -50 ° C to -5 ° C at a pressure of 4-26 bara.

Preferably, said composition has a boiling point of - 60 ° C to 0 ° C, preferably said composition has a boiling point of -55 ° C to 0 ° C, preferably said composition has a boiling point from -50 ° C to -5 ° C at a pressure of 5-23 bara.

According to a preferred embodiment, said composition also comprises pentafluoroethane (F125) and / or chloropentafluoroethane (F115) and / or hexafluoroethane (F116). Advantageously, the total amount of pentafluoroethane (F125), chloropentafluoroethane (F115) or hexafluoroethane (F116) in said composition is less than 2% by weight based on the total weight of said composition. The total amount refers to the sum of the individual proportions of pentafluoroethane (F125), in chloropentafluoroethane (F115) and hexafluoroethane (F116). Preferably, the total amount of pentafluoroethane (F125), chloropentafluoroethane (F115) or hexafluoroethane (F116) in said composition is less than 1% by weight based on the total weight of said composition, in particular less than 0,

According to a second aspect, the present invention provides a process for separating 2,3,3,3-tetrafluoropropene and trifluoropropyne from a composition A comprising 2,3,3,3-tetrafluoropropene and trifluoropropyne, said method comprising the steps of:

i) contacting said composition with an inorganic compound to form a composition B,

ii) purification, preferably distillation, composition B to form a first stream comprising the Bl trifluoropropyne and the inorganic compound; B2 and a second stream comprising 2,3,3,3-tetrafluoropropene.

The inorganic compound may be in liquid form or gaseous form. Preferably, the first stream comprising the Bl trifluoropropyne and the inorganic compound forms an azeotropic or near-azeotropic composition. The first flow Bl may comprise 85% by weight to 99.999% by weight of inorganic compound and 0.001% by weight to 15% by weight of trifluoropropyne based on the total weight of the first flow Bl; preferably 87% by weight to 99.999% by weight of inorganic compound and from 0.001 wt% to 13 wt% of trifluoropropyne; preferably 88% by weight to 99.999% by weight of inorganic compound and 0.001% by weight to 12% by weight of trifluoropropyne; in particular 90% by weight to 99.999% by weight of inorganic compound and 0.001% by weight to 10% by weight of trifluoropropyne.

According to a preferred embodiment, said inorganic compound is hydrochloric acid. Thus, the first flow Bl may comprise an azeotropic composition or quasi-azeotropic comprising trifluoropropyne and hydrochloric acid. The preferred formation of the azeotropic composition or quasi-azeotropic comprising trifluoropropyne and hydrochloric acid facilitates the separation between the trifluoropropyne and 2,3,3,3-tetrafluoropropene contained in the composition A. Thus, the first stream can therefore Bl include under form azeotropic or near-azeotropic, 85% by weight to 99.999% by weight of hydrochloric acid and 0.001% by weight to 15% by weight of trifluoropropyne based on the total weight of the first flow Bl; preferably 87% by weight to 99.999% by weight of hydrochloric acid and 0, 001% by weight to 13% by weight of trifluoropropyne; preferably from 88% by weight to 99.999% by weight of hydrochloric acid and 0.001% by weight to 12% by weight of trifluoropropyne; in particular, 90% by weight to 99.999% by weight of hydrochloric acid and 0.001% by weight to 10% by weight of trifluoropropyne.

The first flow Bl may have a boiling point of -60 ° C to 0 ° C, preferably from -55 ° C to 0 ° C, preferably from -50 ° C to -5 ° C at a pressure of 3 to 26 bara. Advantageously, the first flow Bl may have a boiling point of -60 ° C to 0 ° C, preferably from -55 ° C to 0 ° C, preferably from -50 ° C to -5 ° C at a pressure of 4 to 26 bara. Preferably, the first stream Bl may have a boiling point of -60 ° C to 0 ° C, preferably said composition has a boiling point from -55 ° C to 0 ° C, preferably said composition has a point boiling from -50 ° C to -5 ° C at a pressure of 5-23 bara.

The second B2 stream comprising 2,3,3,3-tetrafluoropropene may contain a small amount trifluoropropyne. The amount in trifluoropropyne B2 in the second stream is less than the initial amount of trifluoropropyne, expressed in moles in the composition B. The amount trifluoropropyne B2 in the second stream can be less than 50% of the initial quantity contained in trifluoropropyne composition B. preferably, the amount in trifluoropropyne in the second flow B2 can be less than 25% of the initial amount of trifluoropropyne contained in the composition B. preferably the amount trifluoropropyne B2 in the second stream can be less than 10 % of the initial amount of trifluoropropyne contained in the composition B. in particular,

According to a preferred embodiment, said second stream B2 comprises less than 1000 ppm of trifluoropropyne; advantageously said second stream B2 comprises less than 500 ppm of trifluoropropyne; preferably said second stream B2 comprises less than 100 ppm of trifluoropropyne; more preferably said second stream B2 comprises less than 50 ppm; in particular said second stream B2 is devoid of trifluoropropyne. The term "free" as used herein refers to an amount of trifluoropropyne in said second flow B2 of less than 20 ppm, preferably less than 10 ppm, preferably less than 1 ppm.

In a third aspect, the invention provides a process for producing 2,3,3,3-tetrafluoropropene. Said method comprises the steps of:

A) fluorination in the presence of a catalyst of a compound of formula (I) CX (Y) 2-CX (Y) m - CH m XY where X and Y independently represent a hydrogen, fluorine or chlorine and m = 0 or 1; and / or fluorination in the presence of a catalyst of a compound of formula (CX n Y 3-n) CHpXi pCH- m X 2-m (II) wherein X is independently of each other Cl, F, I or Br; Y is independently of each other H, Cl, F, I or Br; n is 1, 2 or 3; and m is 0, 1 or 2; and p is 0 or 1;

B) recovering a stream C comprising 2,3,3,3-tetrafluoropropene, hydrochloric acid and trifluoropropyne;

C) Purification, preferably distillation, flow C recovered in step B) to form a first stream D comprising hydrochloric acid and trifluoropropyne; E and a second stream comprising 2,3,3,3-tetrafluoropropene.

According to a preferred embodiment, step A) of the present process may be carried out in the presence of a catalyst from a compound of formula (I) or (II) selected from the group consisting of 2-chloro-3 , 3,3-trifluoro-l-propene (H FCO-1233xf), 1, 1,1,2,3-pentachloropropane (HCC-240db), 1, 1,2,2,3-pentachloropropane (HCC-240aa) , 2,3-dichloro-1, 1,1-trifluoropropane (HCFC-243db), 1, 1,2,3-tetrachloro-l-propene (HCO-1230xa), 2,3,3,3-tetrachloro-l -propene (HCO-1230xf), 2-chloro-l, l, 2-tetrafluoropropane (HCFC-244bb), 1, 1,1,3,3-pentachloropropane (HCC-240fa), 1,1,3, 3-tetrachloropropene (HCO-1230za), 1,3,3,3-tetrachloropropene (HCO-1230zd), l-chloro-3,3,3-trifluoropropene (HCFO-1233zd), 1, 1,1,3-tetrachloropropane (HCC-250fb), 1,1,3-trichloropropene (HCO-1240za), 3,3,3-trichloropropene (HCO-1240zf). Preferably, the

Preferably, the catalytic fluorination is carried out in gaseous phase.

The catalyst used in the present process for producing 2,3,3,3-tetrafluoropropene can be for example based on a metal comprising a transition metal oxide or a derivative or a halide or oxyhalide of such a metal . e.g. FeCu there may be mentioned, the chromium oxyfluoride, chromium oxides (optionally subjected to treatment fluorination), chromium fluorides and mixtures thereof. Other possible catalysts are supported on carbon, the antimony-based catalysts, aluminum catalysts (e.g., AlF3 and Al2O3, alumina and the alumina fluoride oxyfluoride).

in general there may be used a chromium oxyfluoride, fluoride or aluminum oxyfluoride, or a supported or unsupported catalyst containing a metal such as Cr, Ni, Fe, Zn, Ti, V, Zr, Mo, Ge, Sn, Pb, Mg, Sb.

Reference can be made in this regard to WO 2007/079431 (in p.7, 1.1-5 and 28-32), in EP 939 071 (paragraph [0022]), WO 2008/054781 (in p.9 1.22-

p.10 1.34), and WO 2008/040969 (Claim 1), to which reference is expressly made.

The catalyst is more preferably based on chromium and is in particular of a mixed catalyst comprising chromium.

According to one embodiment, using a mixed catalyst comprising chromium and nickel. The molar ratio of Cr / Ni (based on the metal element) is usually 0.5 to 5, for example from 0.7 to 2, for example about 1. The catalyst can contain from 0.5 to 20% by weight of nickel.

The metal may be present in metallic form or as derivative, for example an oxide, halide or oxyhalide. These derivatives are preferably obtained by activation of the catalytic metal.

The support is preferably formed with aluminum, for example alumina, activated alumina or aluminum derivatives such as aluminum halides and oxyhalides of aluminum, for example described in US 4,902,838, or obtained by the activation process described above.

The catalyst may comprise chromium and nickel in an activated or nonactivated form, on a support which has been subjected to activation or not.

Reference may be made to WO 2009/118628 (including p.4, p.7 L.30-1.16), which is expressly referred to here.

Another preferred embodiment is based on a mixed catalyst containing chromium and at least one element selected from Mg and Zn. The atomic ratio of Mg or Zn / Cr is preferably 0.01 to 5.

Before use, the catalyst is preferably subjected to an activation with air, oxygen or chlorine and / or with HF. For example, the catalyst is preferably subjected to an activation with air or oxygen and HF at a temperature of 100 to 500 ° C, preferably from 250 to 500 ° C and more particularly from 300 to 400 ° C. The activation time is preferably 1 to 200 h and more preferably from 1 to 50 h. This activation can be followed by a final fluorination activation step in the presence of an oxidation agent, HF and organics. The molar ratio HF / organic compounds is preferably from 2 to 40 and the molar ratio oxidizing agent / organic compounds is preferably from 0.04 to 25. The temperature of the

The fluorination reaction in the gas phase can be carried out:

- with a molar ratio HF / compound of formula (I) and / or (II) of 3: 1 to 150: 1, preferably 4: 1 to 125: 1 and more preferably from 5: 1 to 100 : 1;

- with a contact time of 3-100 s, preferably 4-75 s and more particularly 5 to 50 s (catalyst volume divided by the total flow entering adjusted to the temperature and operating pressure);

- at a pressure ranging from atmospheric pressure to 20 bar, preferably from 2 to 18 bar and more particularly from 3 to 15 bar;

- at a temperature (catalyst bed temperature) of 200 to 450 ° C, preferably from 250 to 400 ° C, more particularly 280 to 380 ° C.

The duration of the reaction step is typically 10 to 8000 hours, preferably from 50 to 5000 hours, and more preferably from 70 to 1,000 hours.

An oxidizing agent, preferably oxygen, can optionally be added during the fluorination reaction. The molar ratio oxygen / organic compounds may be from 0.005 to 2, preferably 0.01 to 1.5. The oxygen can be fed pure or as air or oxygen / nitrogen mixture. One can also replace oxygen by chlorine.

Preferably, the first stream D comprising hydrochloric acid and trifluoropropyne is recovered distillation column. Preferably, the first stream D is an azeotropic composition or quasi-azeotropic hydrochloric acid and trifluoropropyne.

The formation of an azeotropic composition or quasi-azeotropic hydrochloric acid and trifluoropropyne improves the separation between the trifluoropropyne and 2,3,3,3-tetrafluoropropene. Thus, the stream E comprising 2,3,3,3-tetrafluoropropene will be devoid of or contain trifluoropropyne sufficiently low quantities to facilitate its subsequent purification.

According to a preferred embodiment, the first stream D may include, under azeotropic or near-azeotropic form, 85% by weight to 99.999% by weight of hydrochloric acid and 0.001% by weight to 15% by weight on trifluoropropyne based on total weight of the first stream D; preferably 87% by weight to 99.999% by weight of hydrochloric acid and 0.001% by weight to 13% by weight of trifluoropropyne; preferably 88% by weight to 99.999% by weight of hydrochloric acid and 0.001% by weight to 12% by weight of trifluoropropyne; in particular 90% by weight to 99.999% by weight of hydrochloric acid and 0.001% by weight to 10% by weight of trifluoropropyne.

The first stream D may have a boiling point of -60 ° C to 0 ° C, preferably from -55 ° C to 0 ° C, preferably from -50 ° C to -5 ° C at a pressure of 3 to 26 bara. Advantageously, the first stream may have a boiling point of -60 ° C to 0 ° C, preferably from -55 ° C to 0 ° C, preferably from -50 ° C to -5 ° C at a pressure of 4 to 26 bara. Preferably, the first stream D may have a boiling point of -60 ° C to 0 ° C, preferably from -55 ° C to 0 ° C, preferably from -50 ° C to -5 ° C at a pressure from 5 to 23 bara.

Preferably, step C) of the present process is carried out under process conditions adapted to allow formation of the first stream D comprising hydrochloric acid and one or more compounds which form azeotropic or azeotrope-like with hydrochloric acid . In addition to the azeotropic or azeotrope-like HCl / trifluoropropyne, step C) may be carried out so as to recover in said first stream D, the azeotrope or azeotrope-like HCl / pentafluoroethane (F125), HCI / chloropentafluoroethane ( F115) and / or HCl / hexafluoroethane (F116). Thus, besides the trifluoropropyne, other minor organic impurities can be recovered with hydrochloric acid. Thus, distillation dedicated to the

Thus, in a particular embodiment, the stream C recovered in step B) and said first flow D also include pentafluoroethane (F125) and / or chloropentafluoroethane (F115) and / or hexafluoroethane (F116). Advantageously, the total amount of pentafluoroethane (F125), chloropentafluoroethane (F115) or hexafluoroethane (F116) in said first stream D is less than 2% by weight based on the total weight of said composition. Preferably, the total amount of pentafluoroethane (F125), chloropentafluoroethane (F115) or hexafluoroethane (F116) in said first stream D is less than 1% by weight based on the total weight of said first stream D, in particular less than to 0.5% by weight, more particularly less than 0.1% by weight.

According to a particular embodiment, the stream C recovered in step B) and the first flow D also include difluoromethane (F32) and / or 1,1,1-trifluoroethane (F143a) and / or acid hydrofluoric. Advantageously, the total proportion of difluoromethane and / or 1,1,1-trifluoroethane and / or hydrofluoric acid is less than 0.5% by weight based on the total weight of the first stream D.

According to a particular embodiment, the first stream D may be purified to form a composition comprising hydrochloric acid wherein the trifluoropropyne content is less than 20 ppm, preferably less than 10 ppm, preferably less than 1 ppm. Purifying said first flow D may be effected by the implementation of a catalytic hydrolysis step; washing with an acidic solution; and / or one or several steps of adsorption of impurities by an adsorbent.

Preferably, the catalytic hydrolysis step may be carried out by contacting said first stream with a catalyst bed, which is preferably an activated carbon bed in the presence of water. The temperature of the catalytic hydrolysis step is preferably from 100 to 200 ° C, especially 120 to 170 ° C, more particularly 130 to 150 ° C. The pressure is preferably from 0.5 to 3 barg, especially from 1 to 2 barg. The contact time is preferably from 1 s to 1 min, especially from 2 s to 30 s, more preferably 4 s to 15 s, especially from 5 s to 10 s. The amount of water in said first stream D subjected to catalytic hydrolysis is adjusted so that the molar ratio of water relative to the sum of compounds other than the hydrochloric acid in said first stream D is greater than 1, preferably greater than or equal to 2, or 3, or 4, or 5, or 6 or 6.5. A water intake can be provided if necessary. The catalytic hydrolysis step may be implemented to hydrolyze compounds such as COF2, Cofci, CF3COF if they are present in stream C and the first flow D. Following this catalytic hydrolysis step, a flow fl is recovered. This Fl stream comprises, in addition to hydrochloric acid, trifluoropropyne and optionally pentafluoroethane (F125), chloropentafluoroethane (F115), hexafluoroethane (F116), difluoromethane (F32), 1,1,1-trifluoroethane (F143a) and / or hydrofluoric acid and optionally of trifluoroacetic acid resulting from hydrolysis of CF3COF. The®. It can also be a packed column. Washing the gaseous flow F is preferably carried out against the current: the gas flow Fl is fed with the foot, and an acid solution is fed at the column head. As acid solution, use may in particular HCl solution, at a concentration ranging for example from 5 to 60%, especially 10 to 50%, more preferably from 20 to 45% and in particular from 30 to 35%. Washing the acid solution is preferably carried out at a temperature of 5 to 50 ° C, more particularly from 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. Addition of boric acid at the stage of washing with the acid solution may also be performed in order to complex the fluoride ions. For example, the addition of 2000 to 8000 ppm H3BO3 improves the elimination of certain fluorinated compounds. The washed gas flow F2 resulting from the washing step may be subjected to an adsorption step on activated carbon bed to form a flow F3. Impurities adsorbed by the activated carbon bed are primarily the trifluoropropyne and optionally pentafluoroethane (F125), chloropentafluoroethane (F115), hexafluoroethane (F116), difluoromethane (F32) or 1, 1,1-trifluoroethane (F143a). The adsorption step on activated carbon bed can be implemented in pressure ranges and temperature which have already been mentioned above in connection with the washing step with an acidic solution. The purified gas stream F3 is subjected to a step of adiabatic or isothermal absorption to absorb the hydrochloric acid of the gas flow F3 in an aqueous solution to form an aqueous hydrochloric acid solution F4. This aqueous solution may simply be deionized water, or alternatively may be an acidic solution. Typically, this absorption step is performed on a contacting column against the current, the aqueous solution being provided at the head and the gas flow at the bottom. The absorption reaction of hydrochloric acid in water is exothermic, it is preferred to limit the pressure at which this operation is carried out. 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. To resist corrosion, the column can be made of graphite or steel coated with polytetrafluoroethylene (PTFE). The column internals can be for example either graphite or polyvinylidene fluoride (PVDF). A gas stream deacidized F5 is harvested in mind. This stream can either be discharged into the atmosphere via a neutralization security column or sent to an incinerator. F4 hydrochloric acid solution is collected at the bottom. The mass concentration of hydrochloric acid in the F4 solution may be from 5 to 50%, preferably from 15 to 40%, more particularly from 30 to 35%. If the purity of the collected F4 hydrochloric acid solution is not sufficient, and in particular if the HF content remains above the desired threshold, it is possible to proceed to another processing step, namely an adsorption step on silica gel. The temperature of the hydrochloric acid solution F4 should be as low as possible, and for example less than or equal to 35 ° C, for adsorption onto the silica gel is exothermic. Above this temperature, the adsorption efficiency decreases greatly. The contact time is between a few minutes and a few hours (preferably between 10 and 60 min). crossing speeds are slow and between 1 and 20 m / h and preferably between 3 and 10 m / h. The operating pressure of a few bars (1 to 7 barg and preferably 1 to 5 barg). Silica gel typically has a size of 50 Å pores, whereas conventional gels generally have from 20 Å pore size to the maximum. The fluoride content of the solution

According to a preferred embodiment, the second stream recovered in step E C) of the present method comprising 2,3,3,3-tetrafluoropropene may contain a small amount of trifluoropropyne. Preferably, the amount trifluoropropyne in the second stream E can be less than 10% of the initial amount of trifluoropropyne contained in the stream C. In particular, the amount trifluoropropyne in the second stream E can be less than 5% of the initial amount of trifluoropropyne contained in the stream C. More particularly, the amount trifluoropropyne in the second stream E can be less than 1% of the initial amount of trifluoropropyne contained in the stream C.

According to a preferred embodiment, said second stream E comprises less than 1000 ppm of trifluoropropyne; advantageously said second stream E comprises less than 500 ppm of trifluoropropyne; preferably said second stream E comprises less than 100 ppm of trifluoropropyne; in particular said second stream E is devoid of trifluoropropyne. The term "free" as used herein refers to an amount of trifluoropropyne in said second stream E less than 20 ppm, preferably less than 10 ppm, preferably less than 1 ppm.

According to a preferred embodiment, the stream C and the second stream E also include 1,1,1,2,2-pentafluoropropane (245cb), 1,3,3,3-tetrafluoropropene (1234ze) and impurities a boiling point below the boiling point of 2,3,3,3-tetrafluoropropene; said second stream E is distilled to form a G stream comprising 2,3,3,3-tetrafluoropropene (1234yf), 1,1,1,2,2-pentafluoropropane (245cb) and 1,3,3,3 -tetrafluoropropene (1234ze); and H a ​​stream comprising impurities having a boiling point below the boiling point of 2,3,3,3-tetrafluoropropene. Impurities having a boiling point below the boiling point of 2,3,3,3-tetrafluoropropene can be trifluoromethane (F23) and / or monofluoromethane (F41). In addition, the second flow E may include difluoromethane (F32), pentafluoroethane (F125), 1,1,1-trifluoroethane (F143a) of trifluoropropyne or 1-chloro-pentafluoroethane (F115) in very small quantities. Thus, the second stream E comprises less than 10 ppm of difluoromethane (F32), less than 10 ppm of pentafluoroethane (F125), less than 10 ppm of 1,1,1-trifluoroethane (F143a), less than 10 ppm and trifluoropropyne / or less than 10 ppm of 1-chloro-pentafluoroethane (F115).

According to a preferred embodiment, the G stream comprising 2,3,3,3-tetrafluoropropene, 1,1,1,2,2-pentafluoropropane and 1,3,3,3-tetrafluoropropene contains less than 1 ppm difluoromethane (F32), less than 1 ppm of pentafluoroethane (F125), less

1 ppm of 1,1,1-trifluoroethane (F143a), less than 1 ppm of trifluoropropyne and / or less than 1 ppm of 1-chloro-pentafluoroethane (F115), if the second stream E containing one of these compounds .

The Applicant has thus demonstrated that the combined removal of hydrochloric acid and trifluoropropyne minimizes the loss of 2,3,3,3-tetrafluoropropene by removing or facilitating the distillation dedicated to the removal of organic impurities light given the low levels of light organic impurities contained in the second flow E.

Example

The formation of the azeotrope or azeotrope-hydrochloric acid / trifluoropropyne was simulated with Aspen software. The results are presented in Table 1 below.

Table 1

Azéotrope HCI-Trifluoropropyne

Temperature Pressure azeotropic composition

% weight

° C bara% w HCI

Trifluoropropyne

-60 3,72 93 7

-55 4,33 94 6

-50 5,29 95 5

-45 6,4 97 3

-42 7,15 97,5 2,5

-41 7,41 97,5 2,5

-40 7,69 98,5 1,5

-39 7,96 98,5 1,5

-38 8,25 99 1

-37 8,54 99 1

claims

An azeotropic composition or quasi-azeotropic comprising hydrochloric acid and trifluoropropyne.

The composition of claim 1 comprising 85% by weight to 99.999% by weight of hydrochloric acid and 0.001% by weight to 15% by weight of trifluoropropyne based on the total weight of the composition; preferably said composition has a boiling point of -60 ° C to 0 ° C, preferably at a pressure of 3 to 26 bara.

Composition according to any one of the preceding claims characterized in that it also comprises pentafluoroethane, chloropentafluoroethane and hexafluoroethane.

A process for separating 2,3,3,3-tetrafluoropropene and trifluoropropyne from a composition A comprising 2,3,3,3-tetrafluoropropene and trifluoropropyne, said method comprising the steps of:

i) contacting said composition with an inorganic compound to form a composition B;

ii) the composition of B distillation to form a first stream comprising the Bl trifluoropropyne and the inorganic compound; B2 and a second stream comprising 2,3,3,3-tetrafluoropropene;

said inorganic compound is hydrochloric acid.

Method according to the preceding claim, characterized in that said first flow comprising the Bl trifluoropropyne and the inorganic compound forms an azeotropic or near-azeotropic composition.

A method according to any one of claims 4 or 5 characterized in that the amount of trifluoropropyne B2 of said second stream is less than the initial amount of trifluoropropyne in composition B; advantageously the amount trifluoropropyne B2 in the second stream can be less than 10% of the initial amount of trifluoropropyne contained in the composition B; preferably said second stream B2 comprises less than 1000 ppm of trifluoropropyne, more preferably said second B2 stream comprises less than 500 ppm of trifluoropropyne, in particular said second B2 stream comprises less than 100 ppm, more particularly said second stream B2 comprises less 50 ppm; privileged manner said second stream B2 is devoid of trifluoropropyne.

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

A) fluorination in the presence of a catalyst of a compound of formula (I) CX (Y) 2-CX (Y) m -CH m XY where X and Y independently represent a hydrogen, fluorine or chlorine and m = 0 or 1; and / or fluorination in the presence of a catalyst of a compound of formula (CX n Y 3-n) CHpXi pCH- m X 2-m (II) wherein X is independently of each other Cl, F, I or Br; Y is independently of each other H, Cl, F, I or Br; n is 1, 2 or 3; and m is 0, 1 or 2; and p is 0 or 1;

B) recovering a stream C comprising 2,3,3,3-tetrafluoropropene, hydrochloric acid and trifluoropropyne;

C) distilling the stream C recovered in step B) to form a first stream D comprising hydrochloric acid and trifluoropropyne; E and a second stream comprising 2,3,3,3-tetrafluoropropene.

Method according to the preceding claim characterized in that the first stream D comprising hydrochloric acid and trifluoropropyne is recovered distillation column.

A method according to any one of the preceding claims 7 or 8 characterized in that the amount of trifluoropropyne said second stream E is smaller than the initial quantity of trifluoropropyne in stream C; advantageously the amount trifluoropropyne in the second stream E can be less than 10% of the initial amount of trifluoropropyne contained in the stream C; preferably said second stream E comprises less than 1000 ppm of trifluoropropyne; more preferably said second stream E comprises less than 500 ppm of trifluoropropyne; in particular said second stream E comprises less than 100 ppm; more particularly said second stream E comprises less than 50 ppm; privileged manner said second stream E is devoid of trifluoropropyne.

10. A method according to any one of claims 7 to 9 characterized in that the first stream D comprises an azeotropic composition or quasi-azeotropic comprising 85% by weight to 99.999% by weight of hydrochloric acid and 0.001% by weight to 15% by weight of trifluoropropyne based on the total weight of the first stream D; preferably said composition has a boiling point of -60 ° C to 0 ° C preferably at a pressure between 3 and 26 bara.

11. A method according to any one of claims 7 to 10 characterized in that the stream recovered in step C B) and the first flow D also include pentafluoroethane (F125), chloropentafluoroethane (F115) or hexafluoroethane (F116).

12. A method according to any one of claims 7 to 11 characterized in that the stream recovered in step C B) and the first flow D also include difluoromethane (32), 1, 1,1-trifluoroethane (143a ) and / or hydrofluoric acid.

13. A method according to any one of claims 7 to 12 characterized in that the flow C and the second stream E also comprise 1, 1,1,2,2-pentafluoropropane, 1,3,3,3-tetrafluoropropene and impurities having a boiling point below the boiling point of 2,3,3,3-tetrafluoropropene; said second stream E is distilled to form a G stream comprising 2,3,3,3-tetrafluoropropene, 1,1, 1,2,2-pentafluoropropane and 1,3,3,3-tetrafluoropropene; and H a ​​stream comprising impurities having a boiling point below the boiling point of 2,3,3,3-tetrafluoropropene.