FR3056209A1 - - Google Patents

Abstract

The present invention relates to a process for the preparation of 2-chloro-1,1,1-trifluoropropane (HCFC-253db) by hydrogenation of 2-chloro-3,3,3-trifluoropropene (HCFO-1233xf).

Description

Technical area

The present invention relates to a process for the preparation of 2-chloro-1,1,1 trifluoropropane (HCFC-253db) from 2-chloro-3,3,3-trifluoropropene (HCFO-1233xf).

Context of the invention

2-chloro-1,1,1-trifluoropropane (HCFC-253db) can be used as a heat transfer fluid, propellant, foaming agent, blowing agent, gaseous dielectric, polymerization medium, support fluid, abrasive agent, dehydrating and fluid agent for energy production unit. It can also be used as a starting material in the preparation of agrochemical or pharmaceutical agents.

Various methods for preparing 2-chloro-1,1, l-trifluoropropane (HCFC-253db) from organic raw materials are known.

Several documents (Henne and Whaley, Journal of the American Chemical Society, 1942, vol. 64, p. 1157; McBee et al., Journal of the American Chemical Society, 1947, vol. 69, p. 946; Haszeldine, Journal of the Chemical Society, 1951, p. 249,) describe the preparation of 2-chloro1,1,1-trifluoropropane (HCFC-253db) by chlorination of 1,1,1-trifluoropropane (HFC-263fb). The chlorination reaction produces low yields of the mono- and dichloro derivatives, which are more difficult to separate.

2-chloro-1,1,1-trifluoropropane (HCFC-253db) can also be prepared by fluorination of 1,1,1,2-tertachloropropane (HCC-250db) with anhydrous hydrogen fluoride (HF) in the presence mercury oxide (ll). The molar yield of 2-chloro-1,1,1 ltrifluoropropane (HCFC-253db) is 32% (McBee et al., Journal of the American Chemical Society, 1947, vol. 69, p. 946).

Dmowski and Kolinski, Roczniki Chemii, 1973, vol. 47, p. 1211 relates to a preparation of 2-chloro-l, l, l-trifluoropropane (HCFC-253db) from chloropropionic acid and SF4.

More recently, Hanack and Ullmann, Journal of Organic Chemistry, 1989, vol. 54, n ° 6, p. 1432 describe an easy synthesis of 2-chloro-l, l, l-trifluoropropane (HCFC-253db) by a simple nucleophilic substitution with LiCl of the corresponding nonafluorobutanesulfonate.

These processes produce low yields or typically use raw materials which are not readily available. It has now been discovered that 2-chlorû1,1,1-trifluoropropane (HCFC-253db) can be conveniently prepared from a readily available raw material (2-chloro-3,3,3-trifluoropropene (HCFO-1233xf )), with a correct yield and high selectivity. 2-chloro-3,3,3-trifluoropropene (HCFO-1233xf) is an intermediate widely used in the preparation of 2,3,3,3-tetrafluoropropene (HFO1234yf).

Summary of the invention

The present invention relates to a process for the preparation of 2-chloro-1,1,1 ltrifluoropropane comprising the steps of bringing 2-chloro-3,3,3-trifluoropropene into contact with hydrogen in the presence of a catalyst.

In a preferred embodiment, the catalyst is based on a metal chosen from the group consisting of metals from columns 8 to 10 of the periodic table of the elements and rhenium.

More preferably, the catalyst is based on a metal chosen from nickel, palladium, rhodium, ruthenium, rhenium or platinum.

In a preferred embodiment, 3,3,3-trifluoropropene is also produced as a by-product.

In a preferred embodiment, the step of bringing 2-chloro-3,3,3trifluoropropene into contact with hydrogen is carried out at a temperature of 20 to 200 ° C.

In a preferred embodiment, the method comprises the steps of:

(i) reaction of 2-chloro-3,3,3-trifluoropropene in the gas phase with hydrogen in the presence of a catalyst, (ii) recovery of a first stream comprising 2-chloro-1,1,1, l-trifluoropropane, unreacted hydrogen, and optionally unreacted 2-chloro-3,3,3-trifluoropropene, (iii) recycling a first part of said first stream to the step (i), (iv) recovery of 2-chloro-l, l, l-trifluoropropane from the remaining part of the first stream.

In a preferred embodiment, the first stream further comprises 3,3,3trifluoropropene.

In a preferred embodiment, the remaining part of the first stream comprises 3,3,3-trifluoropropene and 2-chloro-1,1,1-trifluoropropane is recovered from said remaining part of the first stream by purification, preferably by distillation, by formation of a second stream comprising 2-chloro-1,1,1-trifluoropropane and a third stream comprising 3,3,3-trifluoropropene.

In a preferred embodiment, the process is carried out in the gas phase.

In a preferred embodiment, the catalyst is supported on at least one of carbon, alumina, titanium oxide, silica, zirconia or fluorides thereof, calcium fluoride, carbonate calcium, barium sulfate or zeolites.

Detailed description of the present invention

In a first aspect of the present invention, a process for the preparation of 2chloro-1,1,1-trifluoropropane is described. The method includes the step of contacting 2-chloro-3,3,3-trifluoropropene with hydrogen in the presence of a catalyst.

Preferably, the process is carried out continuously. The process is preferably carried out in the gas phase. Therefore, the present process can use a continuous hydrogenation reaction in the gas phase. The process according to the present invention leads to the formation of HCFC-253db with a high yield and excellent selectivity.

In a preferred embodiment, the catalyst is based on a metal chosen from the group consisting of metals from columns 8 to 10 of the periodic table of the elements and rhenium. Consequently, the catalyst can be based on metals such as iron, ruthenium, osmium, cobalt, rhodium, iridium, nickel, palladium, platinum or rhenium. More preferably, the catalyst is based on a metal chosen from nickel, palladium, rhodium, ruthenium, rhenium or platinum. Most preferably, the catalyst is based on platinum or palladium. In particular, the catalyst is based on palladium.

Preferably, the catalyst used in the present process is supported on at least one of carbon, alumina, titanium oxide, silica, zirconia or fluorides thereof, calcium fluoride, carbonate calcium, barium sulfate or zeolites. The term "carbon" in this context includes, but is not limited to, carbon, activated carbon, graphite, carbon nanotubes. The catalyst can also be unsupported such as Raney nickel.

More preferably, the catalyst can be based on platinum or palladium, in particular palladium, supported on carbon or alumina.

In a preferred embodiment, the catalyst can also comprise a cocatalyst based on another metal, for example silver, copper, gold, tellurium, zinc, chromium, molybdenum or thallium . The content of the cocatalyst can be in the range of 0.1 to 20% by weight based on the total weight of the catalyst, preferably 0.5 to 18% by weight, more preferably 1 to 15% by weight , most preferably from 2 to 10% by weight.

The catalyst can be present in any suitable form, for example in the form of a fixed or fluidized bed, preferably in the form of a fixed bed. The direction of flow can be downward or upward. The catalyst bed may further comprise a particular distribution of the catalyst so as to control the heat flows generated by the exothermic reaction. Therefore, it is possible to envisage gradients of charge density, porosity, etc., of the catalyst so as to control the exotherm of the reaction. For example, it can be envisaged for the first part of the bed to include less catalyst, while the second part comprises more.

The present process may include the step of activating the catalyst. The catalyst can be activated by subjecting the catalyst to a stream of gas containing a reducing agent. Activation can be carried out at a temperature of 50 ° C to 250 ° C. The gas stream containing a reducing agent is preferably a mixture of hydrogen and nitrogen. Before activation, the catalyst can be dried. The drying step can be carried out at a temperature of 50 ° C to 200 ° C, preferably from 80 ° C to 150 ° C. The catalyst is preferably dried under an inert atmosphere, such as nitrogen.

The present process may include the step of regenerating the catalyst. The regeneration step can comprise the treatment of the catalyst under an inert atmosphere (nitrogen, argon or helium) and / or under a stream of gas containing an oxidizing agent. The oxidizing agent can be oxygen or air. The regeneration can be carried out at a temperature in the range of 200 ° C to 800 ° C, preferably 250 ° C to 700 ° C, more preferably 300 ° C to 600 ° C, most preferably 350 ° C at 500 ° C. The catalyst can be regenerated by treating the catalyst with a gas stream containing an oxidizing agent to form an oxidized catalyst, optionally cooling the oxidized catalyst, and then treating the catalyst with a gas stream containing a reducing agent. The gas stream containing a reducing agent can be hydrogen. Treatment with the stream of gas containing a reducing agent can be carried out at a temperature of 50 ° C to 250 ° C. The gas stream containing a reducing agent is preferably a mixture of hydrogen and nitrogen.

The step of bringing 2-chloro-3,3,3-trifluoropropene into contact with hydrogen can be carried out at a temperature of 20 to 200 ° C, preferably from 50 ° C to 150 ° C, more preferably from 50 ° C to 100 ° C. The hydrogenation step is exothermic. The reaction temperature can be controlled using means provided for this purpose in the reactor, if necessary. The temperature can vary by a few tens of degrees during the reaction. For example, the inlet temperature can be in the range of 20 ° C to 250 ° C, and the temperature gain can be in the range of 5 ° C to 100 ° C.

The step of bringing 2-chloro-3,3,3-trifluoropropene into contact with hydrogen can be carried out at an absolute pressure of 0.1 to 20 bar, preferably 0.5 to 20 bar, more preferably from 1 to 20 bar, most preferably from 1 to 15 bar, in particular from 1 to 10 bar, more particularly from 1 to 5 bar.

The step of bringing 2-chloro-3,3,3-trifluoropropene into contact with hydrogen can be carried out at a contact time, being defined as being the ratio between the volume of catalyst and the total charge current , from 0.1 to 100 seconds, preferably from 0.5 to 50 seconds, more preferably from 1 to 40 seconds, most preferably from 1 to 30 seconds, in particular from 1 to 20 seconds, more particularly from 2 at 10 seconds.

The step of bringing 2-chloro-3,3,3-trifluoropropene into contact with hydrogen can be carried out at a H ₂ / organic molar ratio, preferably H 2/2-chloro-3,3,3 trifluoropropene, from 1 to 50, preferably from 1.5 to 20, more preferably from 2 to 15, most preferably from 3 to 10, in particular from 3 to 7. A high ratio will lead to dilution, and therefore to a better management of reaction exothermia.

In a particular embodiment, 3,3,3-trifluoropropene is also produced as a by-product. The present process can include a step of purifying 2chloro-1,1,1-trifluoropropane. The purification can be a distillation in order to separate the 2-chloro-1,1,1-trifluoropropane from the unreacted by-products and / or starting materials.

It is possible to control the exotherm of the hydrogenation reaction while maintaining very good conversion and selectivity and / or to reduce the deactivation of the catalyst. Consequently, in a preferred embodiment, the present method can comprise the steps of:

(i) reaction of 2-chloro-3,3,3-trifluoropropene in the gas phase with hydrogen in the presence of a catalyst, (ii) recovery of a first stream comprising 2-chloro-1,1,1, l-trifluoropropane, unreacted hydrogen, and optionally unreacted 2-chloro-3,3,3trifluoropropene, (iii) recycling a first part of said first stream to step (i ), (iv) recovery of 2-chloro-l, l, l-trifluoropropane from the remaining part of the first stream.

Preferably, the first stream recovered in step ii) further comprises 3,3,3trifluoropropene.

The remaining part of the first stream may further comprise 3,3,3-trifluoropropene and 2-chloro-1,1,1-trifluoropropane is recovered from said remaining part of the first stream by purification, preferably by distillation, by forming a second stream comprising 2-chloro-l, l, l-trifluoropropane and a third stream comprising 3,3,3trifluoropropene.

In particular, the present method can comprise the steps of:

(i) reaction of 2-chloro-3,3,3-trifluoropropene in the gas phase with hydrogen in the presence of a catalyst, (ii) recovery of a first stream comprising 2-chloro-1,1,1, l-trifluoropropane, unreacted hydrogen, and optionally unreacted 2-chloro-3,3,3trifluoropropene, (iii) purification, preferably by distillation, of the first stream to form a stream comprising 2-chloro-1,1,1-trifluoropropane and a stream comprising unreacted hydrogen and optionally 2-chloro-3,3,3trifluoropropene unreacted, (iv) recycling the stream comprising unreacted hydrogen, and optionally unreacted 2-chloro-3,3,3-trifluoropropene, to step (i), (v) recovering the stream comprising 2-chloro- l, l, l-trifluoropropane.

More particularly, the first stream recovered in step ii) further comprises 3,3,3-trifluoropropene. Depending on the operating conditions used in step (iii), the 3,3,3trifluoropropene may be in the stream comprising 2-chloro-1,1,1 l-trifluoropropane or in the stream comprising hydrogen not having reacted and optionally unreacted 2-chloro-3,3,3trifluoropropene. When 3,3,3-trifluoropropene is present in the stream comprising 2-chloro-l, l, l-trifluoropropane, the stream comprising 2-chloro-l, l, ltrifluoropropane and 3,3,3-trifluoropropene may be purified, preferably by distillation, to form a fourth stream comprising 2-chloro-1,1,1-trifluoropropane and a fifth stream comprising 3,3,3-trifluoropropene.

The gas stream comprising the recycling loop and the reactants can be preheated before introduction into the reactor. An adiabatic reactor is preferably used.

Example

A tubular reactor is loaded with 10 g of a 0.5% Pd / C wet granule type catalyst. The reactor is housed inside an electric oven. The catalyst is first dried under nitrogen at 110 ° C and at atmospheric pressure. Then, the catalyst is reduced by introducing hydrogen into the nitrogen stream and maintaining the temperature at 110 ° C. After

2 hours, the bed temperature is lowered to 80 ° C, the nitrogen flow is reduced to zero and 2chloro-3,3,3-trifluoropropene (HCFO-1233xf) is fed into the reactor at atmospheric pressure. These feed flows are regulated and regulated by means of mass flow regulators. The molar ratio of hydrogen to organic material is 4.9. The contact time is approximately 5 seconds.

The conversion of 2-chloro-3,3,3-trifluoropropene (HCFO-1233xf) is approximately 100.0%.

The selectivity for the desired 2-chloro-1,1,1-trifluoropropane (HCFC-253db) product is about 91.6%. The main by-product is 3,3,3-trifluoropropene (HFO-1243zf).

Claims (10)

Claims 1. A process for the preparation of 2-chloro-1,1,1 l-trifluoropropane comprising the step of bringing 2-chloro-3,3,3-trifluoropropene into contact with hydrogen in the presence of a catalyst. 2. Method according to the preceding claim in which the catalyst is based on a metal chosen from the group consisting of metals from columns 8 to 10 of the periodic table of the elements and rhenium. 3. Method according to any one of the preceding claims, in which the catalyst is based on a metal chosen from nickel, palladium, rhodium, ruthenium, rhenium or platinum. 4. Method according to any one of the preceding claims, in which 3,3,3trifluoropropene is also produced as a by-product. 5. Method according to any one of the preceding claims, in which the step of bringing 2-chloro-3,3,3-trifluoropropene into contact with hydrogen is carried out at a temperature of 20 to 200 ° C. 6. Method according to any one of the preceding claims, said method comprising the steps of: (i) reaction of 2-chloro-3,3,3-trifluoropropene in the gas phase with hydrogen in the presence of a catalyst, (ii) recovery of a first stream comprising 2-chloro-1,1,1, l-trifluoropropane, unreacted hydrogen, and optionally unreacted 2-chloro-3,3,3-trifluoropropene, (iii) recycling a first part of said first stream to the step (i), (iv) recovery of 2-chloro-l, l, l-trifluoropropane from the remaining part of the first stream. 7. Method according to any one of the preceding claims, in which the first stream further comprises 3,3,3-trifluoropropene. 8. Method according to the preceding claim in which the remaining part of the first stream comprises 3,3,3-trifluoropropene and in which the 2-chloro-l, l, l-trifluoropropane is recovered from said remaining part of the first stream by purification, preferably by 5 distillation, to form a second stream comprising 2-chloro-l, l, l-trifluoropropane and a third stream comprising 3,3,3-trifluoropropene. 9. Method according to any one of the preceding claims, said method being carried out in the gas phase. 10. Method according to any one of the preceding claims, in which said catalyst is supported on at least one of carbon, alumina, titanium oxide, silica, zirconia or fluorides thereof, calcium fluoride, calcium carbonate, barium sulfate or zeolites.