GB2562103A

GB2562103A - Process

Info

Publication number: GB2562103A
Application number: GB1707205.9A
Authority: GB
Inventors: Low Robert; Lloyd Gary; Giddis Clive
Original assignee: Mexichem Fluor SA de CV
Current assignee: Mexichem Fluor SA de CV
Priority date: 2017-05-05
Filing date: 2017-05-05
Publication date: 2018-11-07
Also published as: GB201707205D0

Abstract

A process for removing water from at least one reactor product stream, wherein the at least one reactor produces hydrohalocarbons, from feed material in the presence of hydrogen fluoride (HF). The process comprises feeding the product stream to a distillation column (28, Fig 6) comprising a side-draw stream located at least one theoretical stage below a feed point, a bottoms stream located at least one theoretical stage below the side drawer stream and an overhead stream located above the feed point. The reactor product stream comprises hydro-halocarbons, HF, water, unreacted feed material, and optionally, intermediate organic products and/or hydrogen chloride (HCl). The process may provide for the production of halogenated olefins that reduces the presence of water in order to protect process vessels from corrosion and to maintain reaction conditions at a desired state for efficient conduction of the reactions. The process also provides a means of removing water from a recycle loop of a process for the production of halogenated olefins through the use of a single distillation column.

Description

(54) Title of the Invention: Process

Abstract Title: Process for removing water (57) A process for removing water from at least one reactor product stream, wherein the at least one reactor produces hydrohalocarbons, from feed material in the presence of hydrogen fluoride (HF). The process comprises feeding the product stream to a distillation column (28, Fig 6) comprising a side-draw stream located at least one theoretical stage below a feed point, a bottoms stream located at least one theoretical stage below the side drawer stream and an overhead stream located above the feed point. The reactor product stream comprises hydro-halocarbons, HF, water, unreacted feed material, and optionally, intermediate organic products and/or hydrogen chloride (HCI). The process may provide for the production of halogenated olefins that reduces the presence of water in order to protect process vessels from corrosion and to maintain reaction conditions at a desired state for efficient conduction of the reactions. The process also provides a means of removing water from a recycle loop of a process for the production of halogenated olefins through the use of a single distillation column.

HF & Water

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Figure 1

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First Column

Second Column

Figure 2

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Figure 3

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Figure 4

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Figure 5

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Figure 6

Process

The present invention relates to a process for the removal of water from a product stream comprising (hydro)halocarbons, in particular a product stream comprising halogenated olefins.

The listing or discussion of a prior-published document in this specification should not necessarily be taken as an acknowledgement that the document is part of the state of the art or common general knowledge.

The production of mixtures comprising halogenated olefins often involves the hydrofluorination (i.e. reaction with HF) of halogenated feed materials in the vapour phase over a solid-phase catalyst so as to yield a reaction product comprising: unreacted starting material; fluorinated intermediate species; desired products including halogenated olefins; HCI, HF and undesired side products comprising further halogenated species.

It is a feature of the chemistries for production of mixtures comprising halogenated olefins that complete conversion of the feed materials in a single reaction step is either impractical or impossible as, for example, considerations of thermodynamic equilibrium may prevent complete conversion of the starting material. Furthermore the nature of the chemistries means that intermediate product species or side products which may be reconverted to desired material, are often produced. As an example, the hydrofluorination of R-1233xf to R-1234yf may also produce R-245cb, which may then be dehydrofluorinated to yield R1234yf.

Industrial processes therefore typically operate with at least one recycle loop to return unreacted species, partially converted species and HF back to the reactor system. This recycle loop must also remove the desired species for final purification, as well as undesired side product and/or contaminants. A typical process for the production of halogenated olefins is represented conceptually in Figure 1.

It is highly desirable that the reaction steps be carried out with a controlled and low level of water as there are several undesirable consequences should excess water be present in the catalytic reaction zone, including the loss of selectivity from hydrolysis reactions of the feed materials or the desired products, and damage to the active catalyst surface by interference with surface chemistry.

An additional and potentially more severe consequence of having water present in such processes is that, if it is not removed, it will build up in the recycle loop over time. This can lead to corrosion damage and attack on the vessels, heat exchangers, valves and pipes that together comprise the operational process plant. This can occur even if the plant items are made from materials normally regarded as corrosion resistant, such as nickel alloys (e.g. Hastelloy or Inconel alloys). Low levels of water in the presence of HF can result in attack of such alloys, which may be compounded by the additional presence of HCI.

The consequences of corrosion in HF-containing process equipment can be: economic (loss of production from interruptions to the process to repair damage); consequential harm to safety of operators, or damage to the environment. The cost of corrosion damage in the worst case can significantly outweigh the cost of reactor selectivity or catalyst damage effects.

Water can be present in halogenated olefin production processes for reasons such as:

— Dissolved water in the HF feed to the process as typical water levels in industrial grades of anhydrous HF can be from 10 from 50 ppm by weight or higher;

— Dissolved water in the organic feed material (particularly if it has been stored in a vented atmospheric tank) as typical chlorinated product water levels can be up to 50 ppm by weight;

— Action of HF or HCI on the metal oxide catalyst can result in liberation of water during reaction. For example chrome (III) oxide (chromia) Cr₂O3 can react with HF to yield a chrome oxyfluoride Cr₂O_xF_y (x+y/2=3) together with water, which under typical reactor conditions will be produced as vapour;

— Ingress of water as humidity in air to the plant during maintenance activities that result in opening of the process vessels or pipe work to the atmosphere;

— Generation of water by in-situ regeneration of a fouled catalyst bed as a consequence of oxidation of hydrogen-containing carbonaceous “coke” deposits; and — Scrubbing operations for acid removal using water as scrubbing liquor.

There is therefore a need for a practical process for production of halogenated olefins that deals with the presence of water in such a way that the fabric of the plant is protected from corrosion and the reaction conditions are maintained at a desired state for efficient conduction of the reactions. This requires the development of a technique for separation of water from reaction product mixtures comprising unreacted feed materials, intermediate products, desired products comprising one or more halogenated olefins, HF and HCI.

Several methods exist in the art for removal of water from reaction product mixtures comprising halogenated hydrocarbons, HF and HCI.

One existing method comprises the step of cooling the reaction product mixture to condense at least a portion of the stream, then separating the condensed portion from the rest of the reaction mixture. The condensation step is operated so that the water is partitioned into the liquid phase and may therefore be removed from the process as a purge stream. The disadvantages of this are that the condenser must treat the whole reactor process flow and HF and organic materials of low volatility, such as feed materials, may also condense and result in the loss of valuable material in the purge.

An alternative method is to dehydrate the reactor off-gas as a vapour by contact with a desiccant such as concentrated sulphuric acid in a suitable contacting device, and thus separate the water by partition into the liquid phase. This however has several disadvantages: the contact introduces a new contaminant to the product stream; the equipment must be sized for the whole recycle plus product flow, and material (both organic and acid) will again be lost in the purge stream that removes the water from the sulphuric acid contactor.

Use of solid phase sorbents or desiccants such as molecular sieves for water removal is not feasible for treating recycle streams of processes for halogenated olefin production because of the presence of HF and HCI.

A feasible method of achieving water separation by distillation is to subject the recycle stream to a sequence of distillation steps so as to separate products from recycle, and then to separate the water from the recycle. This is complicated by the existence of azeotropes between some or all of the organic species and HF, and by the existence of a maximum-boiling azeotrope between water and HF. An example of such a sequence is shown in Figure 2. The practical disadvantage of this approach is that two large, complex distillation columns must be used to achieve the separation, and that both columns must be designed to withstand corrosive mixtures of water with HF and potentially reactive organic species.

The applicants have therefore developed a means of removing water efficiently from the recycle loop of a process for the production of halogenated olefins through the use of a single distillation column.

In a first aspect, the invention provides a process for removing water from at least one reactor product stream, wherein the at least one reactor produces desired (hydro)halocarbons from feed material in the presence of hydrogen fluoride (HF), the process comprising feeding the product stream to a distillation column; wherein the distillation column comprises:

a sidedraw stream located at least one theoretical stage below the feed point; a bottoms stream located at least one theoretical stage below the side drawer stream; and an overhead stream located at least theoretical stage above the feed point, wherein the reactor product stream comprises the desired (hydro)halocarbons, HF, water, unreacted feed material, and optionally, intermediate organic products and/or hydrogen chloride (HCI).

By “theoretical stage” it is meant a sufficient number of trays or column packing to ensure that at least one ideal stage of distillation separation is achieved between the location of the feed and offtake points. This may require the use of multiple trays or a packed bed whose height is greater than that which heuristics known in the distillation art suggest is needed to achieve one theoretical stage. Without wishing to be bound by theory, this is thought to be because the distillation process in the base of the tower is governed by mass transfer between liquid and vapour phases rather than by thermodynamic equilibrium compositional differences. Either a trayed or packed column may be used. If a packed column is used the packing may be random packing or structured packing, and may have a plurality of separate beds between the feed point and column top, and between the recycle offtake point and column base.

Preferably, the bottoms stream is located at between about 1 and about 10 theoretical stages beneath the sidedraw stream. More preferably, the bottoms stream is located at between about 1 and about 5 theoretical stages beneath the sidedraw stream, for example between about 1 and about 2 theoretical stages.

Preferably, the sidedraw stream is located at between about 1 and about 50 theoretical stages beneath the feed point. More preferably, the sidedraw stream is located at between about 1 and about 25 theoretical stages beneath the feed point, for example between about 1 and about 10 theoretical stages, e.g. between about 1 and about 5 theoretical stages.

By (hydro)halocarbons, it is meant any saturated or unsaturated carbon compound, comprising at least one halogen (i.e. fluorine, chlorine, bromine or iodine) atom and optionally one or more hydrogen atoms. Preferably the (hydro)halocarbons contains from 1 to 6 carbon atoms, even more preferably 3 carbon atoms. Advantageously, the (hydro)halocarbon is an halogenated olefin and may be selected from one or more of

2.3.3.3- tetrafluoropropene (R-1234yf), 1,3,3,3-tetrafluoropropene (R-1234ze), 3,3,3trifluoropropene (R-1243zf), 2-chloro-3,3,3-trifluoropropene (R-1233xf) and 1-chloro3.3.3- trifluoropropene (R-1233zd).

Preferably, the product stream is distilled in order to generate a: bottoms stream is enriched in water as compared to the product stream; a sidedraw stream enriched in intermediate organic products as compared to the product stream; and an overhead stream depleted in water and enriched in desired halogenated olefins, and optionally intermediate organic products, as compared to the product stream.

Advantageously, the single distillation step of the invention efficiently achieves removal of substantially all of the water content in the product stream as a stream of aqueous HF, separation of materials from the desired products and removal of the desired products with a low level of HF.

Preferably, the overhead stream contains less than about 100 ppm of water, such as less than 80 ppm, less than 50 ppm, less than 20 ppm, less than 10 ppm or even less than 5 ppm of water.

Preferably, the sidedraw stream contains less than about 100 ppm of water, such as less than 80 ppm, less than 50 ppm, less than 20 ppm, less than 10 ppm or even less than 5 ppm of water. The water content of the sidedraw stream may be adjusted by, for example, adjusting the number of theoretical stages between the sidedraw and the feed point.

The process of the present invention minimises the exposure of the process equipment to potentially corrosive concentrations of aqueous HF by restricting the presence of aqueous HF to a small section of the main column. Furthermore, the process results in a significant simplification in the amount of equipment and process control complexity in comparison to using two distillation columns for the separation of the products and the recycled compounds from the combined product stream.

As noted above, the nature of the chemistries means that intermediate product species or side products which may be reconverted to desired material, are often produced. It is therefore advantageous to operate with at least one recycle loop to return unreacted species, partially converted species, and HF to the reaction system. Thus, the sidedraw stream may be recycled back to the reactor from which the product stream is produced.

In reactions involving chlorine-containing reagents it is frequently desired to remove the HCI side product from the system before separation of desired product and recycle. This is because HCI is typically of higher volatility than the material to be recycled and the desired product. HCI may also disturb the equilibrium of the reaction system and so its recycle to the reaction system may be undesired.

Therefore, the overhead stream from the distillation column may be subsequently treated in order to achieve at least partial separation of any HCI, and optionally any light gases, from the overhead stream. Alternatively, the product stream is treated in order to achieve at least partial separation of any HCI, and optionally any light gases, prior to feeding into the distillation column. Examples of possible light gases are air, nitrogen, carbon oxides or hydrogen arising from internal corrosion of the process equipment.

The separation of any HCI (together with any light gases) may be achieved by one or more of partial condensation, flash distillation, fractional distillation and adsorption into a nonaqueous solvent, or any other method known in the art.

The condenser of the distillation column may be operated as a total condenser, in which case the product is removed in the overhead stream as a liquid. Optionally, the distillation column may be operated as a total condenser but may have a vapour offtake for the removal of light gases, such as air, nitrogen, carbon oxides or hydrogen arising from internal corrosion of the process equipment. The vapour offtake may be batch-wise or continuous.

Alternatively, the distillation column is operated as a partial condenser, in which case the product is removed in the overhead stream as a vapour. This may be advantageous if the overhead stream is to be subject to further distillation at a different pressure for the purposes of recovering HF from the product.

In an embodiment, the product stream is produced in vapour phase reaction between a stream comprising halogenated organic feed material and HF and optionally, recycled material from the sidedraw stream.

The product stream may be produced from one or more of the:

— Reaction of R-240db (CCI₃-CHCI-CH₂CI) or R1230xa (CH₂CI-CCI=CCI₂ with HF to form mixtures comprising R-1233xf (CF3-CCI=CH₂),R-1234yf (CF₃-CF=CH₂) or a mixture of either or both of these species with one or more isomers of pentafluoropropane as the desired product;

— Reaction of R-1233xf with HF to form a mixture comprising R-1234yf and at least one of R-245cb (CF₃-CF₂-CH₃) or R-245eb (CF₃-CHF-CH₂F);

— Reaction of R-240fa (CCI₃-CH₂-CHCI₂) with HF to form mixtures comprising R1233zd (CF₃-CH=CHCI), R-1234ze (CF₃-CH=CHF), or a mixture of either or both of these species with one or more isomers of pentafluoropropane as the desired product;

— Reaction of R-1233zd with HF to form a mixture comprising R-1234ze and R-245fa (CF₃-CH₂-CHF₂);

— Reaction of R-250fb (CCI₃-CH₂-CH₂CI) with HF to form mixtures comprising R1243zf (CF₃-CH=CH₂) or a mixture of this species with one or more isomers of tetrafluoropropane as the desired product;

— Reaction of R-245fa (CF₃-CH₂-CHF₂) or R-245eb (CF₃CHFCH₂F) to form R-1234ze — Reaction of R-245cb or R-245eb to form R-1234yf;

— Reaction of R-253fb (CF₃-CH₂-CH₂CI) or R-254fa (CF₃-CH₂-CH₂F) to form R1243zf; and — Reaction of R-243db (CF₃-CHCI-CH₂CI) to form R-1233xf.

Where reference is made herein to a halogenated olefin that can exhibit stereoisomerism, it is to be understood that the reference applies to mixtures comprising one or both steric isomers of the olefin, unless otherwise stated.

Preferably, the vapour phase reaction is catalysed, even more preferably by a metal oxide catalyst. Examples of catalysts that may be employed for such reactions include (but are not limited to) bulk or supported metal oxide catalysts, such as catalysts formulated to include chromia or alumina species. Preferred catalysts comprise bulk chromia and supported chromia species.

Typical reaction conditions involve elevated temperatures in the range from about 100 to about 400 °C, and pressures at or above atmospheric pressure, for example from about 1 to about 30 atm.

Such reactions may be carried out in the presence of HF or HCI. It is often the case that a molar excess of HF is fed with the starting material to reactors whose function is either hydrofluorination or dehydrohalogenation. While it may seem undesirable to do this if dehydrohalogenation is desired to occur, the use of HF as a diluent and heat carrier gas may provide process operating benefits such as the reduction of catalyst fouling rate and transport of heat of reaction, which can justify its inclusion in the reactor feed.

Advantageously, the catalyst is pre-fluorinated using a gas stream comprising a fluorinating agent (such as HF or NF3), optionally further comprising a diluent gas. The catalyst may be pre-fluorinated in the reactor system, preferably wherein the off-gas is subsequently passed to an aqueous HF still. Alternatively, the catalyst is pre-fluorinated prior to introduction into the reactor system.

The water liberation rate from the catalyst is greatest when the fresh catalyst is initially contacted with HF and the pre-fluorination step can therefore reduce the quantity of water liberated over the lifetime of the catalyst.

Preferably, the product stream is subjected to a desiccation step prior to being fed into the distillation column. As noted above, this desiccation step cannot remove the need for active removal of water, but can reduce the total quantity of water to be separated.

The overhead stream may be fed to a second distillation column, preferably operating under anhydrous conditions and/or a different operating pressure. Advantageously, this second distillation column comprises a first stream with depleted levels of HF as compared to the feed stream and a second stream with enriched levels of HF as compared to the feed stream. The stream with enriched levels of HF is preferably fed back into the first distillation column. Ideally, the stream with enriched levels of HF is fed into the first column at a point where the liquid composition inside the column is approximately equivalent to the second stream from the second column. This configuration ensures that substantially no HF is lost from the process with the desired product.

The bottoms stream may be further distilled in a separate distillation system in order to recover anhydrous HF; or it may be subjected to other purification techniques, such as membrane separation, in order to recover anhydrous HF prior to disposal.

As will be understood by the skilled person, any of the preferred and alternative embodiments presented above may be applicable to any of the described aspects of the invention.

Embodiments of the present invention will now be described with reference to the following Figures.

Figure 1 shows a conceptual representation of a process for the production of halogenated olefins.

Figure 2 shows the two column distillation process as used in the art.

Figure 3 shows an embodiment according to the invention.

Figure 4 shows an alternative embodiment according to the invention.

Figure 5 shows a schematic diagram of an integrated process comprising the present invention.

Figure 6 shows a schematic diagram of an integrated process comprising the present invention.

A process comprising an embodiment is shown in Figure 5. The process is for the coproduction of R-1234yf and R-1234zeE. The process utilises a sequence of reactor D 20, reactor C 24, reactor B 26 and reactor A 30, with a separation train 22 and a distillation column according to the invention 28 being positioned between the reactor D 20 and reactor C 24 and the reactor B 26 and reactor A 30 respectively. A Cb supply 21 is provided into the reactor D 21 and a HF supply line 32 is provided into the reactor C 24. The first separation train 22 has a first recycle line 23 for recycling components to the reactor D 20 and the distillation column 28 has a waste outlet 29 for aqueous HF, a sidedraw stream 27 transporting components to the reactor A 30 and an overhead stream to a R-1234yf collection tank 40 and a R-1234zeE collection tank 50. The process is arranged to produce

R-1234yf as a major component of its output, the production of R-1234zeE being a minor component.

In use, a supply of R-1243zf is charged to the reactor D 20, along with a supply of Cb 21 , in a molar ratio of at least about 1:2 R-1234zf:Cl2. The reactor D 20 preferably contains a transition metal containing catalyst, such as 10wt%Cu on AI2O3 and is preferably heated to around 200°C at 8barg. The reaction produces a product stream which comprises R243db as a major component and one or more 1234ze precursors, such as R-243fa and R-244fa as minor components. Some other R-1234yf precursors, such as R-1233xf may also be produced.

The product stream is passed from the reactor D 20 into the first separation train 22 to separate the product stream from unreacted Cb, trace HCI and R-1243zf, which is recycled to the reactor D 20 through the first recycle line 23. The product stream is then passed as a feed stream into the reactor C 24.

The reactor C 24 is primarily adapted to dehydrochlorinate the R-243db in its feed stream to form a product stream which comprises R-1233xf. However, in addition to the R-1234ze precursors formed in the reaction vessel D 20, the feed stream of the reaction vessel C 24, also contains previously unreacted R-243db. The reactor C 24 may contain a zinc/chromia catalyst and may be operated at a temperature of around 350°C and a pressure of about 15barg The HF supply 32 is provided into reactor C 24 to reduce the fouling of the catalyst and also to supply HF to the following hydrofluorination reaction in reactor B 26.

The product stream comprises R-1233xf as a major component, however the product stream also includes R-1234zeE as a minor component and additionally contains one or more R-1234ze precursors such as R-243fa, R-244fa, R-1233zd, R-245fa and R-1234zeZ, some of which are formed in reactor C 24. It is understood that the R-1234zeE and precursors thereof are produced both as by-products of the R-243db in the product feed, but also from reactions of the R-1234ze precursors in the product feed. R-1234yf may also be formed in reactor C 24.

The product stream of the reactor C 24 is provided as a feed stream to the reactor B 26, which is primarily adapted to hydrofluorinate the R-1233xf in the feed stream to form a product stream comprising R-245cb. The feed stream contains some or all of the HF provided to the reactor C 24 by the HF supply 32. It is preferably contacted with a catalyst such as a zinc/chromia catalyst. The reaction is preferably performed at a temperature of around 350 °C and a pressure of about 15 barg.

The product stream comprises R-245cb as a major component, however the product stream also includes R-1234zeE as a minor component, water and additionally contains one or more R-1234ze precursors such as R-243fa, R-244fa, R-1233zd, R-245fa and R1234zeZ, some of which are formed in reactor B 26. It is understood that the R-1234zeE and precursors thereof are produced both as by-products of the R-1233xf in the product feed, but also from reactions of the R-1234ze precursors in the product feed. R-1234yf is also formed in reactor B.

The product stream of the reactor B 26 is then fed into an intermediate position of the distillation column 28 for separation of the various products and removal of substantially all the water. The feed point is positioned at least one theoretical stage below the overhead stream and at least one theoretical stage above the sidedraw streams 27 and 31. The sidedraw streams are in turn at least one theoretical stage above the bottoms stream 29.

The product stream of the reactor B 26 (comprising 245cb, together with HF, water and precursors such as R-243fa, R-244fa, R-1233zd, R-245fa and R-1234ze) is distilled in order to produce an aqueous stream of HF that exits via the bottoms stream. Substantially all of the water in the product stream is removed via the bottoms stream.

The sidedraw stream 27, enriched in R-245cb relative to the product stream of the reactor B 26 is passed to the reactor A 30. At the same time, an additional sidedraw stream enriched in R-234db product stream of the reactor B 26 is recycled back to reactor C 24. Neither stream contains substantially any water, but both contain HF.

Any R-1234yf and R-1234ze(E) present in product stream of the reactor B 26 at this stage exit the distillation column 28 as the overhead stream together with any light gases, HF and HCI.

The reactor A 30 is primarily arranged to dehydrofluorinate the R-245cb to form R-1234yf. The sidedraw stream 27 containing R-245cb is preferably contacted in the reactor A 30 with a zinc chromia catalyst at a preferred temperature of about 350°C and a preferred pressure of about 2 barg. The product stream 25 from reactor A 30 contains R-1234yf as a major component and also contains R-1234zeE as a minor component, together with one or more R-1234ze precursors such as R-245fa and R-1234zeZ. The product stream is passed to the distillation column 28 where R-1234yf and R-1234ze(E) exit the distillation column 28 as the overhead stream with any light gases, HF and HCI. The overhead stream contains substantially no water.

In this way, the undesired combination of water and HF is limited to one distillation column and the water level cannot increase via recycling in the system to a greater (and thus more detrimental) quantity. The invention ensures that the water quantity in the reaction process can never increase, in any section of the process, beyond the levels present in the HF feed 32.

An alternative process comprising an embodiment of the invention is shown in Figure 6. The process is as described with reference to Figure 5 up until rector B 26. The product stream from reactor B 26 is then directly fed into reactor A 30, which is as described above. The product stream from reactor A 30 therefore comprises R-1234yf as the major component, with R-245cb, water, HF, HCI and a small number of precursors such as R243fa, R-244fa, R-1233zd, R-245fa and R-1234ze also present.

The product stream from reactor A 30 is fed into an intermediate position of the distillation column 28 for separation of the various products and removal of substantially all the water. The feed point is positioned at least one theoretical stage below the overhead stream and at least one theoretical stage above the sidedraw stream 33. The sidedraw stream is in turn at least one theoretical stage above the bottoms stream 29.

The reactor A 30 product stream is distilled in order to produce an aqueous stream of HF that exits via the bottoms stream. Substantially all of the water in the product stream is removed via the bottoms stream.

The sidedraw stream 33, enriched in feed product R-245cb relative to the product stream of the reactor A 30, and containing substantially no water, is recycled back to reactor A 30. Any partially fluorinated precursors and HF will also be recycled back to reactor A 30 and be under conditions suitable for conversion, at least partially, to R-1234yf and R-1234ze.

The R-1234yf and R-1234ze(E) present in the product stream of the reactor A 30 exits the distillation column 28 as the overhead stream, together with any light gases, HF and HCI and substantially no water.

Thus, as with the embodiment described above, the undesired combination of water and HF is again limited to one distillation column and the water level cannot increase via recycling in the system to a greater (and thus more detrimental) quantity. The invention ensures that the water quantity in the reaction process can never increase, in any section of the process, beyond the levels present in the HF feed 32.

The invention is defined by the following claims.

Claims

1. A process for removing water from at least one reactor product stream, wherein the at least one reactor produces desired (hydro)halocarbons from feed material in the presence of hydrogen fluoride (HF), the process comprising feeding the product stream to a distillation column; wherein the distillation column comprises:

2. A process according to claim 1, wherein the desired halogenated (hydro)halocarbons are halogenated olefins.

3. A process according to claim 2, wherein the halogenated olefins are selected from one or more of 2,3,3,3-tetrafluoropropene (R-1234yf), 1,3,3,3-tetrafluoropropene (R1234ze), 3,3,3-trifluoropropene (R-1243zf), 2-chloro-3,3,3-trifluoropropene (R-1233xf) and 1-chloro-3,3,3-trifluoropropene (R-1233zd).

4. A process according to any of the preceding claims, wherein the product stream is distilled in order to generate a: bottoms stream is enriched in water as compared to the product stream; a sidedraw stream enriched in intermediate organic products as compared to the product stream; and an overhead stream depleted in water and enriched in desired (hydro)halocarbons as compared to the product stream.

5. A process according to any of the preceding claims, wherein the sidedraw stream is recycled to the reactor.

6. A process according to any of the preceding claims, wherein the overhead stream is subsequently treated in order to achieve at least partial separation of any HCI from the overhead stream.

7. A process according to any of claims 1 to 5, wherein product stream is treated in order to achieve at least partial separation of any HCI from the product stream prior to feeding into the distillation column.

8. A process according to claims 6 or 7, wherein the separation of any HCI is achieved by one or more of partial condensation, flash distillation, fractional distillation and adsorption into a non-aqueous solvent.

9. A process according to any of the preceding claims, wherein the condenser of the distillation column is operated as a total condenser.

10. A process according to claim 9, wherein the distillation column has a vapour offtake for the removal of light gases.

11. A process according to any of claims 1 to 8, wherein the distillation column is operated as a partial condenser.

12. A process according to any of the preceding claims, wherein distillation column is frayed or packed.

13. A process according to any of the preceding claims, wherein the product stream is produced by a vapour phase reaction between a stream comprising halogenated organic feed material, HF and optionally, recycled material from the sidedraw stream.

14. A process according to claim 13, wherein the vapour phase reaction is catalysed, preferably by a metal oxide catalyst.

15. A process according to claim 14, wherein the catalyst is pre-fluorinated using a gas stream comprising a fluorinating agent, optionally further comprising a diluent gas.

16. A process according to claim 14, wherein the catalyst is pre-fluorinated in the reactor system, preferably wherein the off-gas is passed to an aqueous HF still.

17. A process according to any of the preceding claims, wherein the product stream is subjected to a desiccation step prior to being fed into the distillation column.

18. A process according to any of the preceding claims, wherein the overhead stream is fed to a second distillation column.

19. A process according to claim 18, wherein the second distillation column comprises 5 a stream with depleted levels of HF and a stream with enriched levels of HF.

20. A process according to claim 19, wherein the stream with enriched levels of HF is fed back into the first distillation column.

10

21. A recycle loop comprising a distillation column as defined in claim 1.

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Application No: GB1707205.9