Method for manufacturing 1-chloro-2,2-difluoroethane by fluorination of 1,1,2-trichloroethane and / or 1,2-dichloroethylene in gas phase

Abstract

The present invention relates to a method for producing 1-chloro-2,2-difluoroethane (HCFC-142 or F142), by reacting gaseous 1,1,2-trichloroethane (HCC-140 or T112) and / or 1,2-dichloroethylene (HCO-1130-E or 1,2-DCE) with gaseous anhydrous hydrogen fluoride (HF), in a reactor in the presence of nanodiamonds, which is economically feasible at industrial scale and which provides high yield and selectivity.

Description

METHOD FOR MANUFACTURING 1-CHLORO-2,2-DIFLUOROETHANE BY FLUORINATION OF 1,1,2-TRICHLOROETHANE AND / OR 1,2- DICHLOROETHYLENE IN GAS PHASECross-reference to related application

[0001] This application claims priority to European application No. 24315237.8 filed on May 21 , 2024, the whole content of this application being incorporated herein by reference for all purposes.Technical field

[0002] The present invention relates to a method for producing 1 -chloro-2,2- difluoroethane (HCFC-142 or F142), by reacting gaseous 1 ,1 ,2-trichloroethane (HCC-140 or T112) and / or 1 ,2-dichloroethylene (HCO-1130-E or 1 ,2-DCE) with gaseous anhydrous hydrogen fluoride (HF), in the presence of nano diamonds, which is economically feasible at industrial scale and which provides high yield and selectivity.Background

[0003] 1-chloro-2,2-difluoroethane (HCFC-142), is well known as a blowing agent in foam production. However, it is also an important chemical intermediate useful as raw material for preparing pharmaceutical or agrochemical compounds and fluorinated electrolytes for batteries.

[0004] Different routes and reactants for obtaining 1 -chloro-2,2-difluoroethane (HCFC-142) have been described in the patent literature. Among them, two routes are preferred, both involving the use of anhydrous hydrogen fluoride (HF).

[0005] Route 1 , from trans-1 ,2-dichloroethylene (HCO-1130-E), involving the hydrofluorination of trans-1 ,2-dichloroethylene followed by halogen exchange can be represented by the following overall reaction scheme 1 :

[0006] , catalyst+ 2 HF - ► + HC1(E)- 1 ,2-dichloroethylene1 -chloro-2,2-difluoroethaneScheme 1

[0007] Route 2 , from 1 ,1 ,2-trichloroethane (HCC-140 or T112), involving halogen exchange can be represented by the following overall reaction scheme:

[0008] 1 , 1 ,2- tri chloroethane 1 -chloro-2,2-difluoroethaneScheme 2

[0009] Routes 1 and 2 generally require the use of metal catalyst in the bulk or supported onto chromia or alumina. Both routes can be conducted in liquid phase or in gas phase.

[0010] For example FR2783820 relates to a catalytic process for gas phase fluorination of 1 , 1 ,2-trichloroethane with HF to give 1 -chloro-2,2-difluoroethane. The catalyst which is used is a Lewis acid based on Sb i.e. SbCIs. or a nickel / chromium based catalyst supported onto a mixture of alumina and aluminum fluoride. Conversion of 1 ,1 ,2-trichloroethane is close to completion while selectivity is moderated to high.

[0011] US20020183569 discloses a process for the preparation of 1-chloro-2,2- difluoroethane from fluorination in the gas phase of 1 ,1 ,2-trichloroethane with HF in the presence of a fluorination catalyst which is the fluorinated salt of chromium oxide (Cr2O3).

[0012] US2014330051A2 relates to a process requiring a catalyst for gas phase fluorination of 1 , 1 ,2-trichloroethane and / or 1 ,2-dichloroethylene with HF to give 1-chloro-2,2-difluoroethane which is prepared by co-depositing FeCh andMgCl2 on chromia-alumina, or co-depositing Cr(NO3)3 and Ni(NOs)2 on active carbon, or by doping alumina with ZnCh However, although conversion of 1 ,1 ,2-trichloroethane (HCC-140 or T112) is high during fluorination, selectivity to 1-chloro-2,2-difluoroethane (HCFC-142) is low. Depending on the catalyst, conversion of 1 ,2-dichloroethylene (HCO-1130-E or 1 ,2-DCE) is moderate during fluorination while selectivity to 1 -chloro-2,2-difluoroethane (HCFC-142) is high.

[0013] US20170267612A1 discloses a process for producing 1 -chloro-2,2- difluoroethane from 1 ,1 ,2-trichloroethane and / or 1 ,2-dichloroethylene reacting with hydrofluoric acid (HF) in the gas phase, in the presence of a catalyst and optionally in the presence of an oxidizing agent such as oxygen or chloride. Catalysts that are used are bulk chromium oxide (Cr20s) and chromium oxide (Cr20s) supported on alumina. Yields are moderate to high depending on the catalyst and reaction conditions.

[0014] US20210163381 A1 discloses to a process for producing 1 -chloro-2,2- difluoroethane from 1 ,1 ,2-trichloroethane and / or 1 ,2-dichloroethylene reacting with hydrofluoric acid (HF) in the gas phase, in the presence of a catalyst such as CrO2 or SbCIs. However, although selectivity is reasonably high, conversion is very low.

[0015] Nanodiamonds (ND) have been used as a support material to be functionalized with a catalyst or as a proper catalyst material.

[0016] Using nanodiamonds as catalyst material is a cost effective way to promote chemical reactions without requiring metallic containing catalysts which are difficult to produce and handle and that may be harmful to the environment.

[0017] For example, CN106316749A discloses a nanometer diamond material which is used as a catalyst for oxydehydrogenation reaction of ethylbenzene, in a condition with low oxygen content without water vapour protection, in order to generate styrene.

[0018] US006143939A discloses contacting halogenated compounds with synthetic nanosize diamonds to convert the halogenated compounds to olefins and halogenated olefins via elimination reactions.

[0019] As can be read from the patent literature above-cited, the production of 1- chloro-2,2-difluoroethane from 1 ,1 ,2-trichloroethane and / or 1 ,2- dichloroethylene is sometimes obtained through catalytic reaction in the gas phase involving catalyst which requires metallic species that may be supported on different media.

[0020] The Applicant perceived that there is still the need in the art for improving the manufacturing process of 1 -chloro-2,2-difluoroethane.

[0021] In particular, the Applicant is well aware that the processes disclosed in the prior art require catalyst containing metallic species that may be difficult to prepare and handle and that may be harmful for the environment.

[0022] Therefore, there is a need for new process involving environmentally friendly catalyst suitable for preparing 1 -chloro-2,2-difluoroethane from 1 ,1 ,2- trichloroethane and / or 1 ,2-dichloroethylene with high conversion and high level of selectivity in a gas phase process involving gaseous hydrogen fluoride (HF).Summary of the invention

[0023] With the aim of overcoming the above drawbacks, the Applicant faced the problem of providing a process for preparing 1 -chloro-2,2-difluoroethane from 1 ,1 ,2-trichloroethane and / or 1 ,2-dichloroethylene with high conversion and high level of selectivity in a gas phase process involving gaseous hydrogen fluoride (HF).

[0024] Thus, in a first aspect, the present application relates to a method for producing 1-chloro-2,2-difluoroethane from 1 ,1 ,2-trichloroethane and / or 1 ,2- dichloroethylene with high conversion and high level of selectivity in a gas phase process involving gaseous hydrogen fluoride (HF) comprising the step of reacting gaseous 1 , 1 ,2-trichloroethane and / or gaseous 1 ,2-dichloroethylene with gaseous anhydrous hydrogen fluoride (HF) in the presence of a nanodiamond powder (ND2) obtained from a nanodiamond powder (ND) subjected to an acidic treatment.

[0025] The method for manufacturing 1 -chloro-2,2-difluoroethane from 1 ,1 ,2- trichloroethane and / or 1 ,2-dichloroethylene of the present invention ischaracterised by a high conversion yield and by a high level of selectivity, providing 1 -chloro-2,2-difluoroethane particularly suited for many applications, notably as an intermediate to prepare fluorinated electrolyte used in battery applications.

[0026] Advantageously, the method of the present invention is carried out in gas phase using nanodiamonds catalyst which contains a very low amount of metallic species. In other words, the method of the present invention can be considered as a metal-free method, which means that no substantial amount of metallic species or even no metallic species are added to the reaction mixture during the reaction.

[0027] This is advantageous because those species are generally costly to produce and have to be collected and recycled in order to avoid dissemination in the environment, which also contributes to a less cost effective process.

[0028] Moreover, the presence of traces of metallic species in 1 -chloro-2,2- difluoroethane may lead to contamination of the final fluorinated electrolyte product and may compromise the efficiency and / or the lifetime of a battery comprising such contaminated electrolyte. Accordingly, the problem of the presence of traces of metallic species in 1-chloro-2,2-difluoroethane is likely to demand time and resources consuming steps of purification to be overcome.

[0029] Advantageously, the method of the present invention is a solvent-free method, which means that no solvent is added to the reaction mixture during the reaction. This is advantageous because solvents have to be collected and recycled after reaction, which also contributes to a less cost effective process.

[0030] Still advantageously, nanodiamonds are very stable materials that can be recycled in very demanding conditions such as at very high temperature.Detailed description

[0031] The present application relates to a method for producing 1 -chloro-2,2- difluoroethane, comprising the step of reacting gaseous 1 ,1 ,2-trichloroethane (T112) and / or gaseous 1 ,2-dichloroethylene (1 ,2-DCE) with gaseous hydrogen fluoride (HF) in a reactor in the presence of a nanodiamond powder(ND2) obtained from a nanodiamond powder (ND) subjected to an acidic treatment.

[0032] According to the method of the present invention, gaseous 1 ,1 ,2- trichloroethane and / or 1 ,2-dichloroethylene is reacted with anhydrous HF in the gas phase.

[0033] 1 ,1 ,2-trichloroethane and / or 1 ,2-dichloroethylene in the gas phase may be obtained from liquid 1 ,1 ,2-trichloroethane and / or 1 ,2-dichloroethylene by heating the same to a temperature above 1 ,1 ,2-trichloroethane and / or 1 ,2- dichloroethylene boiling point (respectively bpTU2 and bpi,2-DCE).

[0034] Liquid 1 ,1 ,2-trichloroethane is commercially available on the market or may be produced by any known method, for example by chlorinating ethylene to give 1 ,2-dichloroethane which is further chlorinated to give 1 ,1 ,2-trichloroethane. The boiling point at atmospheric pressure of 1 ,1 ,2-trichloroethane is bpTH2 = 110-115°C.

[0035] Liquid 1 ,2-dichloroethylene exists as cis-1 ,2-dichloroethylene or trans-1 ,2- dichloroethylene. Both isomers are commercially available on the market separately or as a mixture. They may be produced by any known method, generally they are obtained as by-products of the manufacture of vinyl chloride.

[0036] The boiling point at atmospheric pressure of cis-1 ,2-dichloroethylene is bpi,2- DCEZ = 60.2°C . The boiling point at atmospheric pressure of trans-1 ,2- dichloroethylene is bpi,2-DCEE = 48.5°C. The boiling point of the mixture essentially consisting of cis-1 ,2-dichloroethylene and trans-1 ,2- dichloroethylene at atmospheric pressure is influenced by the composition of the mixture.

[0037] In some embodiments, in the method according to the invention gaseous 1 , 1 ,2- trichloroethane, and / or gaseous 1 ,2-dichloroethylene for reacting with gaseous anhydrous HF is obtained from liquid 1 ,1 ,2-trichloroethane, and / or liquid 1 ,2- dichloroethylene loaded into the reactor maintained at a temperature above their respective boiling point.

[0038] The term reactor is not limited and encompasses any vessel equipped with inlet to feed with reactants and outlet to recover products, with heating systemwherein gas phase reaction can be conducted using a solid catalyst optionally at reduced or high pressure.

[0039] In some embodiments, loading 1 ,1 ,2-trichloroethane and / or 1 ,2- dichloroethylene in liquid state into the heated reactor is suitably carried out by cannulation to an inlet. 1 ,1 ,2-trichloroethane and / or 1 ,2-dichloroethylene in liquid state is then instantaneously moved to gaseous phase when introduced in the heated reactor maintained at a temperature of above their respective boiling point.

[0040] In some other embodiments, loading 1 ,1 ,2-trichloroethane and / or 1 ,2- dichloroethylene in liquid state into the heated reactor is suitably carried out by cannulation with carrier gas. A suitable carrier gas for cannulation is nitrogen or argon.

[0041] Still in some other embodiments, loading 1 ,1 ,2-trichloroethane and / or 1 ,2- dichloroethylene in liquid state into the heated reactor is suitably carried out using a pump, for example a syringe pump.

[0042] 1 ,1 ,2-trichloroethane and / or 1 ,2-dichloroethylene in the liquid phase has a purity of at least 95%, preferably of at least 98%, more preferably of at least 99.5%.

[0043] 1 ,1 ,2-trichloroethane and / or 1 ,2-dichloroethylene in liquid phase may be then loaded into the reactor for reacting with gaseous anhydrous hydrogen fluoride (HF) which can be suitably introduced into the reactor by injection.

[0044] Typically, 1 ,1 ,2-trichloroethane and / or 1 ,2-dichloroethylene in the liquid phase is added into the reactor for being contacted with gaseous HF continuously or added in a controlled manner throughout the reaction time at a substantially constant rate.

[0045] Still, in some other embodiments 1 ,1 ,2-trichloroethane and / or 1 ,2- dichloroethylene are previously vaporized at a temperature above their respective boiling point and loaded, by cannulation or using a pump, in gaseous state into the reactor via the inlet.

[0046] Thus, in order to obtain 1 ,1 ,2-trichloroethane and / or 1 ,2-dichloroethylene in gas phase, liquid 1 , 1 ,2-trichloroethane and / or 1 ,2-dichloroethylene may be pre-heated in a suitable apparatus that keeps 1 ,1 ,2-trichloroethane and / or 1 ,2- dichloroethylene in gas phase and which is connected with the reactor through a proper system of injection suitably thermostated to maintain 1 ,1 ,2- trichloroethane and / or 1 ,2-dichloroethylene in the gas phase.

[0047] 1 ,1 ,2-trichloroethane and / or 1 ,2-dichloroethylene can be loaded in gaseous state into the reactor as it is, optionally in admixture with a carrier gas.

[0048] 1 ,1 ,2-trichloroethane and / or 1 ,2-dichloroethylene in the gas phase may be loaded into the reactor as a mixture with a carrier gas [(mixture (M1 )], wherein said mixture (M1 ) can be obtained by bubbling a carrier gas into the 1 ,1 ,2- trichloroethane and / or 1 ,2-dichloroethylene in the gas phase and kept at a temperature above their respective boiling point. Carrier gas to be bubbled into the apparatus can be the same gas used for cannulation, or can be a different gas.

[0049] The term “carrier gas” as used in the process of the present invention is intended to mean any chemically stable and dry gas, with a moisture content not higher than 100 ppm.

[0050] The carrier gas for use in the preparation of mixture (M1 ) is preferably nitrogen.

[0051] Typically, 1 ,1 ,2-trichloroethane and / or 1 ,2-dichloroethylene in the gas phase or the mixture (M1 ) comprising 1 ,1 ,2-trichloroethane and / or 1 ,2- dichloroethylene in the gas phase is added into the reactor for being contacted with gaseous HF continuously or added in a controlled manner throughout the reaction time at a substantially constant rate.

[0052] 1 , 1 ,2-trichloroethane and / or 1 ,2-dichloroethylene in the gas phase has a purity of at least 95%, preferably of at least 98%, more preferably of at least 99.5%.

[0053] 1 , 1 ,2-trichloroethane and / or 1 ,2-dichloroethylene in the gas phase may be then loaded into the reactor for reacting with gaseous anhydrous hydrogen fluoride (HF) which can be suitably introduced into the reactor by injection.

[0054] At atmospheric pressure, the boiling point of HF is 19.5°C. Thus, in order to obtain anhydrous HF in gas phase, liquid anhydrous HF may be pre-heated in a suitable apparatus that keeps anhydrous HF in gas phase and which isconnected with the reactor through a proper system of injection suitably thermostated to maintain anhydrous HF in the gas phase.

[0055] Addition of gaseous anhydrous HF in the reactor is generally carried out continuously.

[0056] Typically, gaseous anhydrous HF is continuously added or added in a controlled manner in the reactor throughout the reaction time at a substantially constant rate.

[0057] Gaseous anhydrous HF can be provided to the reactor as it is. Optionally, gaseous anhydrous HF can be diluted with a carrier gas, and provided to the reactor in the gas phase in admixture with the carrier gas [mixture (M2)].

[0058] The carrier gas for use in the preparation of mixture (M2) is preferably nitrogen.

[0059] Additional carrier gas may be directly fed into the reactor.

[0060] The molar ratio between 1 , 1 ,2-trichloroethane and / or 1 ,2-dichloroethylene and the anhydrous HF is preferably between 1 :2 and 1 :20, preferably between 1 :2 and 1 :10, more preferably between 1 :2 and 1 :8.

[0061] The molar ratio between 1 , 1 ,2-trichloroethane and / or 1 ,2-dichloroethylene and the total amount of carrier gas, when present, in the reactor mixture is preferably between 1 :3 and 1 :30, preferably between 1 :3 and 1 :15.

[0062] The reaction between 1 ,1 ,2-trichloroethane and / or 1 ,2-dichloroethylene and anhydrous HF in the gas phase takes place in a reactor at temperature and pressure conditions that are suitable for keeping all the reactants and carrier gas into the gas phase.

[0063] Typically, the reaction is carried out into a reactor at a temperature of from 150 to 350 °C, more preferably from 180 to 300 °C, still more preferably from 200 to 250 °C. Good results were obtained at 220°C.

[0064] Typically, the reaction is carried out into a reactor at a pressure of from 0.1 to 50 bars, more preferably from 0.5 to 20 bars, still more preferably from 1 to 10 bars. Good results were obtained at 1 barA.

[0065] Any nanodiamond powder (ND) can be used as the catalyst in the process according to the invention.

[0066] Nanodiamonds can be obtained by ultrasonic cavitation starting e.g. from graphite as described in US20140037532A1.

[0067] The transformation of graphitic material into nanodiamond crystallites by the application of circular shockwaves as depicted in US3238019 can also be used.

[0068] Nanoscale diamond particles can be prepared by detonation of explosives such as TNT in an oxygen-deficient atmosphere as described by V.Mochalin et al. in The properties and applications of nanodiamonds, Nature Nanotechnology 7, 11-23 (2012).

[0069] Nanodiamond powder (ND) generally comprises primary crystallites or particles having a diameter in the range of 2 to 10 nm. These particles can be found as primary aggregates of 20-30 nm in size, which form weakly bonded secondary aggregates of from hundreds of nanometers to micrometers in size.

[0070] The structure of the nanodiamond crystallites depends on conditions of synthesis and of chemical purification.

[0071] Nanodiamond primary particles can be seen as bulky molecules having a rigid diamond core made of sp3hybridized carbon atoms surrounded by a shell of sp2sp3hybridized carbons such as graphitic or amorphous carbon that may comprise functional groups which are mainly oxygenated functional groups.

[0072] In some preferred embodiments, nanodiamonds powder (ND) suitable for the invention is prepared by detonation and isolated from the diamond detonation blend according to any process well known by the skilled person.

[0073] Commercially available detonation nanodiamond powder (ND) can be used. Good results were obtained with nanodiamond powder (ND) composed of diamond nanoparticles 4-7 nm provided by ACS Material®.

[0074] In some embodiments, nanodiamond powder (ND) particle size can be reduced by deagglomeration. For example, deagglomeration can be conducted by beads milling in water or solvent medium.

[0075] In some embodiments, nanodiamond average particle size D50 ranges from 2 nm to 200 nm; preferably from 2 nm to 100 nm, more preferably from 4 nm to 50 nm; even more preferably from 4 nm to 20 nm.

[0076] Dx-value denotes the value which is determined with regard to the distribution by volume of the sizes of the particles for which x% of the particles have a size less than or equal to this value Dx. Thus, for example, with respect to D10, 10% of the particles have a size which is less than D10. For example again, with respect to D90, 90% of the particles have a size which is less than D90. D50 corresponds to the median value of the distribution by volume.

[0077] Particle size can be measured by any technique well known by the skilled person, e.g. by transmission electron microscopy (TEM), or by dynamic light scattering (DLS).

[0078] The nanodiamond powder (ND) suitable for the invention has a specific surface area measured by the Brunauer-Emmet-Teller (BET) method generally ranging from 150 m2 / g to 420 m2 / g; preferably from 200 m2 / g to 420 m2 / g; more preferably from 250 m2 / g to 420 m2 / g; even more preferably from 270 m2 / g to 420 m2 / g.

[0079] Specific surface area of the particles can be measured by nitrogen gas adsorption according to Brunauer-Emmet-Teller (BET) method described in “The journal of the American Chemical Society”, vol. 60, page 309, February 1938.

[0080] In the process according to the invention, the nanodiamond powder (ND) is previously subjected to an acidic treatment to give a nanodiamond powder (ND2).

[0081] The inventors have found that nanodiamond powder (ND2) is effective for preparing 1-chloro-2,2-difluoroethane from 1 ,1 ,2-trichloroethane and / or 1 ,2- dichloroethylene with high conversion and high level of selectivity in a gas phase process involving gaseous hydrogen fluoride (HF).

[0082] In some embodiments the acidic treatment of nanodiamond powder (ND) comprises the step of:- i) optionally adding the nanodiamond powder (ND) in hydrochloric acid (HCI) water solution of concentration ranging from 0.1 mol.L’1to 12 mol.L’1(37%) and stirring at a temperature ranging from 10°C to 50°C, for a duration ranging from 0.1 h to 10h to obtain a suspension (S1 );- ii) optionally recovering a nanodiamond powder (ND1 ) from the suspension (S1 );- iii) adding the nanodiamond powder (ND) or the nanodiamond powder (ND1 ) recovered in step (ii) in nitric acid (HNO3) water solution of concentration ranging from 0.1 mol.L’1to 15.3 mol.L’1(68%) and stirring at a temperature ranging from 20°C to 120°C, for a duration ranging from 0.1 h to 15h to obtain a suspension (S2);- iv) recovering a nanodiamond powder (ND2) from the suspension (S2).

[0083] Nanodiamond powder (ND1 ) can be recovered in step ii) e.g. by filtration or centrifugation of suspension (S1 ), washing with water and is optionally further dried.

[0084] Nanodiamond powder (ND2) can be recovered in step iv) e.g. by filtration or centrifugation of suspension (S2), washing with water and is optionally further dried.

[0085] In some embodiments, nanodiamond powder (ND2) recovered in step iv) is further dried until constant weight is observed. Drying is performed at a temperature ranging from 30 °C to 150°C, at ambient or reduced pressure.

[0086] In some preferred embodiments the acidic treatment of nanodiamond powder (ND) comprises the steps i) to iv).

[0087] Nanodiamond powder (ND2) obtained from nanodiamond powder (ND) subjected to acidic treatment is placed into the reactor and the reactants are injected continuously into the reactor via inlet.

[0088] By reactants is meant 1 , 1 ,2-trichloroethane and / or 1 ,2-dichloroethylene and hydrogen fluoride (HF).

[0089] As previously explained when in contact the reactants are in gaseous state.

[0090] The time of contact of the gaseous reactants in the presence of the nanodiamond powder (ND2) catalyst generally ranges from 0.1 seconds to 5minutes; preferably from 0.2 seconds to 2 minutes and more preferably from 0.3 seconds to 60 seconds.

[0091] The reaction conditions are maintained in the reactor such that the 1-chloro- 2,2-difluoroethane, unreacted HF and by-products produced are extracted from the outlet as a gas.

[0092] As can be seen from scheme 1 and scheme 2, a first by-product is HCI.

[0093] Other possible organic by-products may be generated in various amounts, depending on reaction conditions, during the process.

[0094] Without being exhaustive, some organic by-products are supposed to come from the reactions represented on scheme 3.

[0095] 1,2-DCE (Z and E)Scheme 3

[0096] In some embodiments some by-products such as F141 or FHC=CHCI can be recycled and used as reactants in addition to gaseous 1 ,1 ,2-trichloroethane and / or gaseous 1 ,2-dichloroethylene and gaseous hydrogen fluoride (HF).

[0097] At the end of the reaction, 1-chloro-2,2-difluoroethane, unreacted HF and some organic by-products can be separated from the gaseous reaction mixture by condensation, while the other gaseous products, such as HCI byproduct remain in the gas phase.

[0098] 1-chloro-2,2-difluoroethane, unreacted HF and the other organic by-products can be further separated by distillation.

[0099] In some embodiments, HF may be recovered for reuse in the process of fluorination of 1 ,1 ,2-trichloroethane and / or 1 ,2-dichloroethylene.

[0100] According to other embodiments, unreacted HF and HCI by-product can be captured by any method known in the art, for example by absorption into water or neutralization in basic solution.

[0101] Still in some embodiments, HCI by-product is recovered in the form of 35%- 37% aqueous solution for further uses.

[0102] Finally, 1 -chloro-2,2-difluoroethane can be separated from the reaction mixture and further purified e.g. according to the procedure disclosed in US20170267612A1 or in US20200002253A1

[0103] However, any method well known by the skilled person can be used to separate 1 -chloro-2,2-difluoroethane from the reaction mixture and purify it.

[0104] The method according to the present invention advantageously provides a high conversion of 1 ,1 ,2-trichloroethane and / or 1 ,2-dichloroethylene to 1 - chloro-2,2-difluoroethane, with good selectivity.

[0105] 1-chloro-2,2-difluoroethane as obtained at the end of the process of the present invention can be advantageously used as such for other reactions or optionally further purified by any means known from a skilled person, including distillation, etc.

[0106] Some of the steps or all steps of the method according to the invention are advantageously carried out in equipment e.g. a reactor capable of withstanding the corrosion of the reactants, reaction medium and products.

[0107] For this purpose, materials are selected for the part in contact with the reaction medium that are corrosion-resistant, such as the alloys based on molybdenum, chromium, cobalt, iron, copper, manganese, titanium, zirconium, aluminum, carbon and tungsten, sold under the Hastelloy® brands or the alloys of nickel, chromium, iron and manganese to which copper and / or molybdenum are added, sold under the name Inconel® or Monel™, and more particularly the Hastelloy C276 or Inconel 600, 625 or 718 alloys. Use may also be made of equipment consisting of or coated with a polymeric compound resistant to the corrosion of the reaction medium. Mention may in particular be made of materials such as PTFE (polytetrafluoroethylene or Teflon) or PFA(perfluoroalkyl resins). Further, corrosion-resistant SiC materials can be used. It will not be outside the scope of the invention to use an equivalent material.

[0108] Should the disclosure of any patents, patent applications, and publications which are incorporated herein by reference conflict with the description of the present application to the extent that it may render a term unclear, the present description shall take precedence.

[0109] The invention will be now described with reference to the following examples, whose purpose is merely illustrative and not intended to limit the scope of the invention.Experimental section

[0110] Raw materials

[0111] Nanodiamonds obtained by detonation method, having a BET specific surface area of 300-420 m2 / g and an average particle size of 4-7 nm were obtained from ACS Material®. According to the provider, nanodiamonds have less than 20 ppm of ionic impurities.

[0112] 1 , 1 ,2-trichloroethane (T112) was provided by Thermo Fisher Scientific.

[0113] 1 ,2-dichloroethylene (1 ,2-DCE) mixture of cis and trans was provided by Merck.

[0114] Anhydrous HF, was obtained from Rapid’Gaz.

[0115] Catalysts preparation

[0116] Supported metal (Cr, Zn and Mg) catalysts over nanodiamonds were prepared by wetness impregnation of an aqueous solution of the respective metallic nitrate. The impregnation of the support, consisting of nanodiamonds which were previously submitted to acidic treatment as reported below, was carried out at room temperature and atmospheric pressure. The quantity of the metal corresponded to an amount varying from 1 .5 wt% to 10 wt% based on the total weight of the respective supported catalyst. For supported catalysts containing Zn and Cr, the molar atom ratio Zn / (Zn +Cr) ranged from 0 to1 . The resulting products were dried overnight at 110°C under reduced pressure and submitted to a temperature of 380°C during 4 hours under nitrogen atmosphere.

[0117] Bulk chromium oxide resulted from the dehydration of chromium hydroxide prepared by addition of a 5 M aqueous solution of ammonia to a 0.5 M aqueous solution of chromium nitrate. Final pH was equal to 7.5 and the formed hydroxide was stirred at 80 °C during 1 hour so as to obtain complete precipitation. The resulting solid was washed with hot distilled water, dried for 16 hours in an oven at 90 °C and finally submitted to a temperature of 380°C during 8 hours under nitrogen atmosphere.

[0118] ZnCr bulk catalysts were prepared following the same procedure as for bulk chromium oxide catalyst manufacture, starting with an aqueous solution of chromium nitrate and zinc nitrate as precursors, with a Zn / Zn+Cr molar atom ratio varying from 0 to 1.

[0119] Nanodiamonds acidic treatment

[0120] Nanodiamond powder (ND) obtained from ACS Material® was suspended in a 0.3 mol.L’1hydrochloric acid (HCI) water solution and stirred at 25°C during 1 hour. Then nanodiamond powder was recovered by filtration on fritted glass using a buchner funnel and washed with distilled water. Recovered nanodiamond powder (ND1 ) was further suspended in a 5 mol.L’1nitric acid (HNOs) water solution. The suspension was stirred at 90°C during 5 hours, cooled to room temperature and solid material was recovered by filtration on fritted glass using a buchner funnel. The solid material was then washed with distilled water until obtaining a neutral pH for the filtrate and dried at 120°C during 12 hours to give the final nanodiamond powder (ND2).

[0121] T112 fluorination

[0122] Liquid T112 was injected using a syringe pump and instantaneously vaporized into the reactor preloaded with the catalyst and placed in an oven to maintain the temperature at 220°C.

[0123] Simultaneously, anhydrous HF was injected in the gas phase into the reactor. To obtain this gas phase, the bottle of anhydrous HF was placed in a first oven at 54°C. A second oven containing the nozzle and the valves was heated at 72°C. The anhydrous HF in the gas phase was diluted with a cofeeding of nitrogen just before the inlet of the reactor.

[0124] At the outlet, the flow of products of the reaction was neutralized through bubbling in an aqueous solution of KOH and was further passed through dichloromethane before being analysed by online gas chromatography.

[0125] The results of trials carried out at 220 °C, with a time of contact of gaseous flow with nanodiamond catalyst and other catalysts of 0.35s , with a molar ratio: HF / N2 / TH2 = 6 / 1 .6 / 1 and a reaction time of 4.5h, are reported in Tablel .

[0126] It is clear from these results that nanodiamond powder previously subjected to an acidic treatment surprisingly gives good conversion of T112 and the best selectivity in F142 than the other catalytic systems tested (compare runs 6 and 7 with other runs).

[0127] Under the present conditions, nanodiamond previously subjected to an acidic treatment gives better results, in term of yield of F142 recovered, than catalysts commonly disclosed in prior art for this reaction such as bulk Cr20s (compare runs 6 and 7 with run 1 ).

[0128] Surprisingly, untreated nanodiamond gives low conversion and no F142 (see run 8).

[0129] Furthermore, nanodiamond functionalized with metallic catalysts containing Cr, Zn / Cr or Mg gives lower conversion and lower selectivity in F142 than nanodiamond powder previously subjected to an acidic treatment (compare runs 3-5 with runs 6 and 7).SPOP 2024 / 021Table 1Time of contact of gaseous flow with catalyst = 0.35 secondsTemperature of reaction = 220°CHF / N2 / T112 = 6 / 1 .6 / 1Time of reaction 4.5 hours

Claims

ClaimsClaim 1 . A method for producing 1 -chloro-2,2-difluoroethane, comprising the step of reacting gaseous 1 ,1 ,2-trichloroethane (T112) and / or gaseous 1 ,2- dichloroethylene (1 ,2-DCE) with gaseous hydrogen fluoride (HF) in a reactor in the presence of a nanodiamond powder (ND2) obtained from a nanodiamond powder (ND) subjected to an acidic treatment.Claim 2. The method according to claim 1 , wherein the nanodiamond powder (ND) is prepared by detonation.Claim 3. The method according to claim 1 or 2, wherein the acidic treatment of the nanodiamond powder (ND) comprises the step of:- i) optionally adding the nanodiamond powder (ND) in hydrochloric acid (HCI) water solution of concentration ranging from 0.1 mol.L’1to 12 mol.L’1(37%) and stirring at a temperature ranging from 10°C to 50°C, for a duration ranging from 0.1 h to 10h to obtain a suspension (S1 );- ii) optionally recovering a nanodiamond powder (ND1 ) from the suspension (S1 );- iii) adding the nanodiamond powder (ND) or the nanodiamond powder (ND1 ) of step ii) in nitric acid (HNO3) water solution of concentration ranging from 0.1 mol.L’1to 15.3 mol.L’1(68%) and stirring at a temperature ranging from 20°C to 120°C, for a duration ranging from 0.1 h to 15h to obtain a suspension (S2);- iv) recovering a nanodiamond powder (ND2) from the suspension (S2).Claim 4. The method according to any one of the preceding claims, wherein gaseous 1 ,1 ,2-trichloroethane, and / or gaseous 1 ,2-dichloroethylene for reacting with gaseous anhydrous HF is obtained from liquid 1 ,1 ,2-trichloroethane, and / or liquid 1 ,2-dichloroethylene loaded into the reactor maintained at a temperature above their respective boiling point.Claim 5. The method according to anyone of the preceding claims, wherein gaseous 1 , 1 ,2-trichloroethane, and / or gaseous 1 ,2-dichloroethylene is loaded intothe reactor for reacting with gaseous anhydrous HF optionally in admixture with a carrier gas [mixture (M1 )].Claim 6. The method according to any one of the preceding claims, wherein gaseous anhydrous HF is loaded into the reactor for reacting with gaseous 1 ,1 ,2- trichloroethane, and / or gaseous 1 ,2-dichloroethylene optionally in admixture with a carrier gas [mixture (M2)].Claim 7. The method according to claim 5 or claim 6, wherein the carrier gas is nitrogen.Claim 8. The method according to any one of the preceding claims wherein the reaction between 1 ,1 ,2-trichloroethane and / or 1 ,2-dichloroethylene and anhydrous HF in the gas phase takes place in a reactor at temperature and pressure conditions that are suitable for keeping all the reactants and carrier gas when present into the gas phase.Claim 9. The method according to any one of the preceding claims, wherein the molar ratio between 1 ,1 ,2-trichloroethane, and / or 1 ,2-dichloroethylene and the anhydrous HF is between 1 :2 and 1 :20, preferably between 1 :2 and 1 :10, more preferably between 1 :2 and 1 :8.Claim 10. The method according to any one of the preceding claims, wherein the molar ratio between gaseous 1 ,1 ,2-trichloroethane, and / or gaseous 1 ,2- dichloroethylene and the total amount of carrier gas in the reactor mixture is preferably between 1 :3 and 1 :30, preferably between 1 :3 and 1 :15.Claim 11 . The method according to any one of the preceding claims, wherein the step of reacting gaseous 1 ,1 ,2-trichloroethane, and / or gaseous 1 ,2- dichloroethylene with gaseous anhydrous HF is carried out in the reactor at a temperature of from 150 °C to 350 °C, more preferably from 180 °C to 300 °C, still more preferably from 200 °C to 250 °C.Claim 12. The method according to any one of the preceding claims, wherein the reaction is carried out into a reactor at a pressure of from 0.1 to 50 bars, more preferably from 0.5 to 20 bars, still more preferably from 1 to 10 bars.Claim 13. The method according to any one of the preceding claims, wherein the time of contact of the gaseous reactants in the presence of the nanodiamondpowder (ND2) ranges from 0.1 seconds to 5 minutes; preferably from 0.2 seconds to 2 minutes and more preferably from 0.3 seconds to 60 seconds.

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