WO2013090354A1

WO2013090354A1 - Process for the production of chlorinated and/or brominated propanes and/or propenes

Info

Publication number: WO2013090354A1
Application number: PCT/US2012/069131
Authority: WO
Inventors: Max Markus Tirtowidjojo; William J. Kruper; David Stephen LAITAR
Original assignee: Dow Global Technologies, Llc
Priority date: 2011-12-13
Filing date: 2012-12-12
Publication date: 2013-06-20

Abstract

Processes for the production of chlorinated and/or brominated propanes and/or propenes are provided. The present processes make use of a feedstream comprising 1,2-dichloropropane and at least one bromination step. Regioselectivities of at least 90% to desired dichlorobromopropanes are provided. The present processes may also include one or more halogen exchange and/or dehydrohalogenation steps that leverage the regioselectivities provided by the initial bromination step.

Description

PROCESS FOR THE PRODUCTION OF CHLORINATED AND/OR BROMINATED

PROPANES AND/OR PROPENES

FIELD

[0001] The present invention relates to processes for the production of chlorinated and/or brominated propanes and/or propenes.

BACKGROUND

[0002] Hydrofluorocarbon (HFC) products are widely utilized in many applications, including refrigeration, air conditioning, foam expansion, and as propellants for aerosol products including medical aerosol devices. Although HFC's have proven to be more climate friendly than the chlorofluorocarbon and hydrochlorofluorocarbon products that they replaced, it has now been discovered that they exhibit an appreciable global warming potential (GWP).

[0003] The search for more acceptable alternatives to current fluorocarbon products has led to the emergence of hydrofluoroolefin (HFO) products. Relative to their predecessors, HFOs are expected to exert less impact on the atmosphere in the form of a lesser, or no, detrimental impact on the ozone layer and their much lower GWP as compared to HFC's. Advantageously, HFO's also exhibit low flammability and low toxicity.

[0004] As the environmental, and thus, economic importance of HFO's has developed, so has the demand for precursors utilized in their production. Many desirable HFO compounds, e.g., such as 2,3,3, 3-tetrafluoroprop-l-ene or 1,3,3,3- tetrafluoroprop-l-ene, may typically be produced utilizing feedstocks of chlorocarbons, and in particular, chlorinated propenes, which may also find use as feedstocks for the manufacture of polyurethane blowing agents, biocides and polymers.

[0005] Unfortunately, many chlorinated propenes may have limited commercial availability, and/or may only be available at prohibitively high cost, due at least in part to the complicated, multi-step processes typically utilized in their manufacture. This may be due at least in part to the fact that conventional processes for their manufacture may require the use of starting materials that are prohibitively expensive to be economically produced by manufacturers on the large scale required to be useful as feedstocks. Additionally, conventional processes may require multiple chlorination and dehydrochlorination steps to arrive at a desired level of chlorination in the final product. Dehydrochlorination steps are typically conducted with an aqueous base, and result in the production of large quantites of waste water containing large quantities of sodium chloride and/or chlorinated organics. Treatment of this waste water is time consuming and expensive, and results in the recovery of low value by-products.

[0006] It would thus be desirable to provide improved processes for the large capacity and/or continuous production of chlorocarbon precursors useful as feedstocks in the synthesis of refrigerants and other commercial products. More particularly, such processes would provide an improvement over the current state of the art if they were less costly in starting materials, processing time, and/or capital costs required to implement and maintain the process. Generation of byproducts having a higher value than sodium chloride, or really any value, would be a further advantage if provided in such a process.

BRIEF DESCRIPTION

[0007] The present invention provides efficient processes for the production of chlorinated and/or brominated propanes and/or propenes. Advantageously, the processes make use of 1,2-dichloropropane, a by-product in the production of chlorohydrin, as a low cost starting material, alone or in combination with 1,2,3-trichloropropane. Selectivity of the process is enhanced over conventional chlorination processes by employing a bromination step that provides for a highly regioselective addition of bromine to the starting material, and thus more regioselective chlorination and dehydrohalogenation reactions thereafter. Further, in some embodiments, the use of caustic cracking steps can be reduced or even eliminated, so that an anhydrous hydrohalide, e.g., HBr and/or HC1, can be recovered from the process. Less waste water is thus generated, providing further time and cost savings.

[0008] In one aspect, the present invention provides a process for the production of chlorinated and/or brominated propanes and/or propenes from a feedstream comprising 1,2- dichloropropane, either alone, or in combination with 1,2,3-trichloropropane. The process comprises at least one bromination step. The at least one bromination step occurs in the presence of a suitable brominating agent, e.g., Br₂, and in some embodiments, a free radical catalyst. l,2-dichloro-2-bromopropane is produced at a ratio of at least 90: 1 relative to 1,2- dichloro-l-bromopropane, or at least 95:5, or even at least 97:3. The process may also comprise at least one halogen exchange step which may occur in the presence of HC1, either alone or in combination with a Lewis acid, and may, in some embodiments, may advantageously result in the preferential formation of 1, 1,2-trichloropropane.

[0009] Dehydrohalogenation steps may also be performed, and may occur in the vapor phase in the presence of a dehydrohalogenation catalyst, i.e., FeCl₃, Cr₂0₃, activated carbon, or combinations of these. In such embodiments, one or more anhydrous hydrohalides, e.g., HC1 and/or HBr, may be recovered from the process, if desired. Alternatively, one or more of the dehydrohalogenation reactions can also be carried out in the liquid phase by reaction with aqueous caustic.

[0010] When the process includes at least one dehydrohalogenation step, the process may result in the production of one or more chlorinated and/or brominated propenes. The chlorinated and/or brominated propene(s) produced may comprise from 3 to 5 chlorine atoms, and in some embodiments, the chlorinated propene may be 1, 1,2,3-tetrachloropropene.

[001 1] The advantages provided by the present processes may be carried forward by utilizing the chlorinated propenes to produce further downstream products, such as, e.g., 2,3,3,3-tetrafluoroprop-l-ene or 1,3,3,3- tetrafluoroprop-l-ene.

DESCRIPTION OF THE FIGURES

[0012] FIG. 1 shows a schematic diagram of a process according to one embodiment; and [0013] FIG. 2 shows a schematic diagram of a process according to a further embodiment. DETAILED DESCRIPTION

[0014] The present specification provides certain definitions and methods to better define the present invention and to guide those of ordinary skill in the art in the practice of the present invention. Provision, or lack of the provision, of a definition for a particular term or phrase is not meant to imply any particular importance, or lack thereof. Rather, and unless otherwise noted, terms are to be understood according to conventional usage by those of ordinary skill in the relevant art. [0015] The terms "first", "second", and the like, as used herein do not denote any order, quantity, or importance, but rather are used to distinguish one element from another. Also, the terms "a" and "an" do not denote a limitation of quantity, but rather denote the presence of at least one of the referenced item, and the terms "front", "back", "bottom", and/or "top", unless otherwise noted, are merely used for convenience of description, and are not limited to any one position or spatial orientation.

[0016] If ranges are disclosed, the endpoints of all ranges directed to the same component or property are inclusive and independently combinable (e.g., ranges of "up to 25 wt.%, or, more specifically, 5 wt.% to 20 wt.%," is inclusive of the endpoints and all intermediate values of the ranges of "5 wt.% to 25 wt.%," etc.). As used herein, percent (%) conversion is meant to indicate change in molar or mass flow of reactant in a reactor in ratio to the incoming flow, while percent (%) selectivity means the change in molar flow rate of product in a reactor in ratio to the change of molar flow rate of a reactant.

[0017] Reference throughout the specification to "one embodiment" or "an embodiment" means that a particular feature, structure, or characteristic described in connection with an embodiment is included in at least one embodiment. Thus, the appearance of the phrases "in one embodiment" or "in an embodiment" in various places throughout the specification is not necessarily referring to the same embodiment. Further, the particular features, structures or characteristics may be combined in any suitable manner in one or more embodiments.

[0018] In some instances, "PDC" may be used as an abbreviation for 1,2-dichloropropane, "TCP" may be used as an abbreviation for 1,2,3-trichloropropane and "TCPE" may be used as an abbreviation for 1, 1,2,3-tetrachloropropene. The terms "cracking" and "dehydrohalogenation" are used interchangeably to refer to the same type of reaction, i.e., one resulting in the creation of a double bond typically via the removal of a hydrogen and a halogen atom from adjacent carbon atoms in halogenated hydrocarbon reagents.

[0019] The present invention provides efficient processes for the production of chlorinated and/or brominated propanes and/or propenes. The present processes comprise conducting at least one bromination step on a feedstream comprising 1,2,-dichloropropane. The use of PDC, a byproduct in many chlorohydrin processes, as a starting material is economically more attractive than disposing of it via incineration, as may be done in connection with some conventional processes.

[0020] The present process is further advantageous since a saleable product can be reached in fewer steps, resulting in lower capital costs as compared to conventional processes. That is, since the addition of bromine to 1,2-dichloropropane can be highly regioselective to l,2,-dichloro-2-bromopropane, further halogen exchange, chlorination and/or dehydrohalogenation steps may also be regioselective to desired intermediates and/or final products.

[0021] The present processes, in some embodiments, may also provide a reduction of caustic cracking steps as compared to conventional processes, and so, one or more anhydrous hydrohalides, e.g., HC1 and/or HBr, can be recovered. Anhydrous HC1 and/or HBr are of greater value than the sodium chloride or sodium bromide that would be produced as byproduct(s) if conventional caustic cracking steps were utilized. The present process thus results in the production of a by-product that may either be sold or used as a feedstock for other processes, e.g., ethylene oxyhalogenation to produce ethylene dichloride or ethylene dibromide.

[0022] The present process makes use of a feedstream comprising 1,2-dichloropropane to produce the desired chlorinated and/or brominated propanes. The process feedstock may also comprise trichloropropane, or other chlorinated alkanes, if desired. And, the 1,2- dichloropropane may be generated upstream of the process, e.g., as a byproduct in a chlorohydrin process, or by any other methods known to those of ordinary skill in the art.

[0023] The brominating step of the process may be conducted using any brominating agent known to those of ordinary skill in the art. Suitable examples include, for example, bromine, phosphorus tribromide, bromine chloride, aluminum tribromide, etc. The brominating step may also desirably be conducted in the presence of a free radical catalyst. Suitable free radical catalysts include, but are not limited to, compounds comprising one or more azo- groups (R-N=N-R') such as azobisisobutyronitrile (AIBN) or 1,1'- azobis(cyclohexanecarbonitrile (ABCN) and organic peroxides such as di-tert-butyl peroxide, benzoyl peroxide, dibenzoyl peroxide, methyl ethyl ketone peroxide, and acetone peroxide. UV or visible light may also be utilized to catalyze brominations that proceed via a free radical mechanism.

[0024] Any chlorinated and/or brominated propane and/or propene may be produced using the present method, although regioselectivity to l,2-dichloro-2-bromopropane is desirable, since subsequent halogen exchange step(s) can then be utilized to provide 1,2,2- trichloropropane with similar regioselectivity. 1,2,2-trichloroproane is a highly desirable starting material in many manufacturing processes, commercially available in quantities to limited to be utilized. In some embodiments then, the bromination step may desirably provide l,2-dichloro-2-bromopropane at a ratio of at least 90: 10 relative to 1,2-dichloro-l- bromopropane, or even a ratio of at least 95:5, or even a ratio of at least 97:3.

[0025] As mentioned above, the processes may also comprise one or more halogen exchange steps, in which chlorine may be exchanged for bromine. Such an exchange, also known to those of ordinary skill in the art as a metathesis reaction, may involve many one or many steps, so long as the net effect is at least one chlorine atom taking the place of at least one bromine atom in a reactant. The one or more halogen exchange step is desirably conducted in the presence of HC1, and optionally, one or more Lewis acids, e.g., ferric chloride, antimony pentafluoride, boron trichloride, aluminum trichloride, and stannic chloride. Combinations of two or more of these may also be used, if desired. In some embodiments, anhydrous aluminum chloride may desirably be utilized as the Lewis acid.

[0026] In some embodiments, the process may incorporate one or more chlorination steps as well. If chlorination steps are to be utilized, they may be carried out using any chlorination agent, and several of these are known in the art. For example, suitable chlorination agents include, but are not limited to chlorine, and/or sulfuryl chloride (SO2CI2). Of these, chlorine may be particularly suitable for use in gas phase chlorinations, while both CI2 and sulfuryl chloride may be particularly suitable for use in liquid phase chlorinations.

[0027] In addition to the free radical catalysts mentioned above, any chlorination steps included in the present process may also be carried out using one or more ionic chlorination catalysts. Exemplary ionic chlorination catalysts include, but are not limited to, aluminum chloride, ferric chloride, iodine, sulfur, iron, etc. [0028] One or more of the dehydrohalogenation steps of the present process may be carried out in the presence of a catalyst so that the use of liquid caustic is reduced, or even eliminated, from the process. In such embodiments, suitable dehydrohalogenation catalysts include, but are not limited to, ferric chloride (FeCy. Ferric chloride, for example, can also be used to dehydrohalogenate 1, 1,1, 2,3 -pentachloropropane to TCPE.

[0029] In some embodiments, one or more of the dehydrohalogenation steps of the present process may be conducted in the presence of a liquid caustic. Although vapor phase dehydrohalogenations advantageously result in the formation of a higher value byproduct than liquid phase dehydrohalogenations, liquid phase dehydrohalogenation reactions can provide cost savings since evaporation of reactants is not required. The lower reaction temperatures used in liquid phase reactions may also result in lower fouling rates than the higher temperatures used in connection with gas phase reactions, and so reactor lifetimes may also be optimized when at least one liquid phase dehydrochlorination is utilized.

[0030] Many chemical bases are known in the art to be useful for liquid dehydrohalogenations, and any of these can be used. For example, suitable bases include, but are not limited to, alkali metal hydroxides, such as sodium hydroxide, potassium hydroxide, calcium hydroxide; alkali metal carbonates such as sodium carbonate; lithium, rubidium, and cesium or combinations of these. Phase transfer catalysts such as quaternary ammonium and quaternary phosphonium salts (e.g. benzyltrimethylammonium chloride or hexadecyltributylphosphonium bromide) can also be added to improve the dehydrohalogenation reaction rate with these chemical bases.

[0031] Any or all of the catalysts utilized in the process can be provided either in bulk or in connection with a substrate, such as activated carbon, graphite, silica, alumina, zeolites, fluorinated graphite and fluorinated alumina. Whatever the desired catalyst (if any), or format thereof, those of ordinary skill in the art are well aware of methods of determining the appropriate format and method of introduction thereof. For example, many catalysts are typically introduced into the reactor zone as a separate feed, or in solution with other reactants.

[0032] The amount of any catalyst utilized will depend upon the particular catalyst chosen as well as the other reaction conditions. Generally speaking, in those embodiments of the invention wherein the utilization of a catalyst is desired, enough of the catalyst should be utilized to provide some improvement to reaction process conditions (e.g., a reduction in required temperature) or realized products, but yet not be more than will provide any additional benefit, if only for reasons of economic practicality.

[0033] For purposes of illustration only, then, it is expected that useful concentrations of any free radical catalyst will range from 10 ppm to 5 wt.%, or from 100 ppm to 0.5 wt.%. Suitable amounts of the Lewis acid will range from 0.001% to 10% by weight each with respect to the dichlorinated alkane, or from 0.01% to 10%, or from 0.1% to 5 wt%, inclusive of all subranges there between. If a dehydrohalogenation catalyst, e.g., FeCi₃, is utilized, useful concentrations may range from 0.01wt% to 5wt%, or from 0.05wt% to 2wt% at temperatures of from 70°C to 200°C. If a chemical base is utilized for one or more dehydrochlorinations, useful concentrations of these will range from 0.01 to 20 grmole/L, or from 1 grmole/L to 10 grmole/L, inclusive of all subranges there between. Relative concentrations of each catalyst/base are given relative to the feed, e.g., 1,2-dichloropropane alone or in combination with 1,2,3-trichloropropane.

[0034] In additional embodiments, one or more reaction conditions of the process may be optimized, in order to provide even further advantages, i.e., improvements in selectivity, conversion or production of reaction by-products. In certain embodiments, multiple reaction conditions are optimized and even further improvements in selectivity, conversion and production of reaction by-products produced can be seen.

[0035] Reaction conditions of the process that may be optimized include any reaction condition conveniently adjusted, e.g., that may be adjusted via utilization of equipment and/or materials already present in the manufacturing footprint, or that may be obtained at low resource cost. Examples of such conditions may include, but are not limited to, adjustments to temperature, pressure, flow rates, molar ratios of reactants, etc.

[0036] That being said, the particular conditions employed at each step described herein are not critical, and are readily determined by those of ordinary skill in the art. What is important is that a feedstream comprising 1,2-dichloropropane, either alone or in combination with 1,2,3-trichloropropane, is used as a starting material and that at least one bromination step is utilized, desirably as a first step. The order of the following reaction steps is unimportant, and those of ordinary skill in the art will readily be able to determine suitable equipment for each step, as well as the particular conditions at which the halogen exchange, chlorination, dehydrohalogenation, separation, drying, and isomerization steps may be conducted.

[0037] In the present process, a feed stream comprising fresh 1,2-dichloropropane, either alone, or in some embodiments, in combination with 1,2,3-trichloropropane is converted to l,2-dichloro-2-bromopropane at a ratio of at least 90: 10, or at least 95:5, or even at least 97:3 relative to 1,2-dichloro-l-bromopropane. When 1,2,3-trichloropropane is fed together with PDC, it is also partially converted to l,2,3-trichloro-2-bromopropane. A subsequent halogen exchange step can thus result in the production of 1,2,2-trichloropropane with similar selectivity relative to other trichloropropanes. In some embodiments, the present process may include one or more dehydrohalogenation steps, and thus result in the formation of one or more propenes, such as TCPE.

[0038] In one exemplary embodiment, PDC is first fed to a bromination reactor, e.g., such as a batch or continuous stirred tank autoclave reactor with an internal cooling coil. A shell and multitube exchanger followed by vapor liquid disengagement tank or vessel can also be used. For reasons of process efficiency, the use of a reactor capable of accommodating a continuous process is preferred.

[0039] Suitable reaction conditions for this initial bromination reaction include, e.g., temperatures of from ambient temperature (e.g., 20°C) to 160°C, or from 40°C to 120°C, or from 50°C to 100°C. Ambient pressure may be used, or pressures of from 100 kPa to 1000 kPa, or from 100 kPa to 500 kPa, or from lOOkPa to 300 kPa. At such conditions, the bromination of PDC will produce l,2-dichloro-2-bromopropane at selectivities of greater than or equal to 90%, or even greater than or equal to 95%, or even up to 97%.

[0040] A schematic illustration of such a process is shown in Figure 1. As shown in Figure 1, process 100 would make use of bromination reactor 102, chlorination reactor 116, bromine regeneration reactor 106, HBr and HCl recovery columns 104 and 118, halogen exchange reactor 110, separation columns 108, 1 12, 1 14, 120 and 122, dehydrohalogenation reactor 124, drying column 126 and isomerization reactor 128. [0041] In operation, 1,2-dichloropropane and a bromine source is fed into bromination reactor 102, which is desirably operated at conditions sufficient to produce HBr and a small fraction of unreacted PDC in an overhead stream thereof. This overhead stream is cooled, condensed and fed to HBr recovery column 104, which may desirably be a distillation column. HBr recovery column 104 is operated at conditions effective to provide HBr as an overhead stream (which may optionally be provided to bromine regeneration reactor 106 to regenerate B¾ by reacting HBr with oxygen) and unconverted B¾ and PDC in a bottoms stream that may be recycled to bromination reactor 102.

[0042] The bottoms stream from bromination reactor 102, comprising dichlorobromopropane isomers and unreacted PDC, is fed to separation column 108, which separates the unreacted PDC and recycles it to bromination reactor 102 as an overhead stream, and provides the dichlorobromopropanes together with HCl to halogen exchange reactor 1 10. Halogen exchange reactor 110 is operated at conditions effective to convert HCl and 1,2-dichloro, 2-bromopropane to produce HBr and 1,2,2-trichloropropane as a product stream.

[0043] The product stream from halogen exchange reactor 110 may be cooled, condensed and fed to separation column 1 12. Separation column 1 12 is operated at conditions effective to provide anhydrous HBr, 1, 1,2-trichloropropane, and unconverted HCl as an overhead stream and the unconverted 1,2-dichloro, 2-bromopropane in bottoms stream. The overhead stream from separation column 1 12 is provided to separation column 1 14, while the bottoms stream from separation column 112 may be recycled to halogen exchange reactor 1 10. The separation column 114 is operated at conditions effective to remove excess HCl and HBr byproduct in the overhead stream which is fed to unit 104 for further HBr and HCl recovery.

[0044] The bottoms stream from separation column 114, comprising trichloropropane, is fed to chlorination reactor 1 16. Chlorination reactor 1 16 is operated at conditions effective to provide an overhead stream comprising HCl and unreacted CI2 that is fed to HCl recovery unit 118. HCl is purified in the overhead stream of unit 118 while the unreacted CI2 is recycled back to chlorination reactor 1 16. The bottom stream of chlorination reactor 116, comprising tetrachloropropane, pentachloropropane, and unreacted tri-chloropropane, is fed to separation columnl20. Separation column 120 is operated at conditions effective to provide recycled trichloropropane and tetrachloropropanes in an overhead stream that is recycled to chlorination reactor 1 16. The bottoms stream of separation column 120, comprising pentachloropropane isomers and heavier products, is fed to separation column 122, which provides the pentachloropropane isomers in an overhead stream and feeds them to dehydrohalogenation reactor 124, and purges the heavy byproducts in a bottom stream.

[0045] Dehydrohalogenation reactor 124 cracks the pentachloropropane isomers to provide TCPE and 2,3,3,3-tetrachloropropene. These tetrachloropropene isomers are provided to drying column 126, from which water and sodium bromide may be purged, and then to isomerization reactor 128 to provide a product stream comprising TCPE.

[0046] For those embodiments wherein a mixture of PDC and 1,2,3-trichloropropane is fed into process 100, the bottom of separation column 108 would comprise 1,2-dichloro, 2- bromopropane and 1,2,3-trichloro, 2-bromopropane. The product of halogen exchange reactor 1 12, in turn, would comprise 1,2,2, 3-tetrachloropropane and 1 ,2,2-trichloropropane. Separation column 1 10 is operated at conditions effective to provide the 1 ,2,2- trichloropropane and tetrachloropropane in an overhead stream. This mixture is then converted to the desired tetrachloropropene product as described above.

[0047] A further embodiment of the present process is shown in Figure 2. Process 200 is similar to process 100, except that the halogen exchange reactor 110, separation column 112 and chlorination reactor 1 14 are replaced by dehydrohalogenation reactor 230 and additional drying unit 232. And so, as shown in Figure 2, process 200 would make use of bromination reactor 202, chlorination reactor 216, bromine regeneration reactor 206, HBr and HCl recovery columns 204 and 218, separation columns 208, 220 and 222, dehydrohalogenation reactors 224 and 230, drying columns 226 and 232 and isomerization reactor 228.

[0048] Process 200 operates similarly to process 100, except that the bottom stream from separation column 208, comprising dichlorobromopropane isomers, is fed to dehydrohalogenation reactor 230 to produce dichloropropene intermediates. The product of dehydrohalogenation reactor 230 is then dried in drying column 232 and the dichloropropenes further chlorinated in chlorination reactor 216 to 1, 1,2,2- tetrachloropropane, 1,2,3-trichloropropene, and pentachloropropenes. Byproduct HCl and excess HCl in the overhead stream of chlorination reactor 216 is fed to recovery column 218 to recover anhydrous HCl in the overhead stream and excess CI2 in the bottom stream that is recycled back to chlorination reactor 216. The chlorinated products of chlorination reactor 216, comprising tetrachloropropane, trichloropropene, and pentachloropropanes, are then fed to separation column 220.

[0049] Separation column 220 is operated at conditions effective to remove trichloropropene and tetrachloropropane intermediate in an overhead stream that is then recycled back to chlorination reactor 216. The bottom stream from separation column 220, comprising pentachloropropanes, is then fed to separation column 222 where they pentachloropropanes are further purified by removing them in the overhead stream of separation column 222, while the heavy byproducts are purged from a bottom stream.

[0050] The overhead stream from separation column 222 is then fed to dehydrohalogenation reactor 224 to produce a mixture of tetrachloropropene isomers that are further processed as described in connection with process 100.

[0051] For those embodiments wherein a mixture of PDC and 1,2,3-trichloropropane is fed into process 200, the bottom stream of separation column 208 will comprise 1,2-dichloro- 2-bromopropane and l,2,3-trichloro-2-bromopropane. The product of dehydrohalogenation reactor 230 comprises 1,2-dichloropropene and 1,2,3 -trichloropropene and this stream is dried in drying unit 232. Chlorination of this stream in chlorination reactor 216 results in the desired intermediate mixture of 1 , 1 ,2,2-tetrachloropopane, 1,2,3 -trichloropropene, pentachloropropane. This mixture is then converted to the desired tetrachloropropene product as described above.

[0052] The chlorinated propenes produced by the present process may typically be processed to provide further downstream products including hydrofluoroolefins, such as, for example, 1,3,3,3-tetrafluoroprop-l-ene (HFO-1234ze). Since the present invention provides an improved process for the production of chlorinated propenes, it is contemplated that the improvements provided will carry forward to provide improvements to these downstream processes and/or products. Improved methods for the production of hydrofluoroolefins, e.g., such as 2,3,3,3-tetrafluoroprop-l-ene (HFO-1234yf), are thus also provided herein.

[0053] The conversion of chlorinated propenes to provide hydrofluoroolefins may broadly comprise a single reaction or two or more reactions involving fluorination of a compound of the formula C(X)_mCCl(Y)_n(C)(X)_m to at least one compound of the formula CF₃CF=CHZ, where each X, Y and Z is independently H, F, CI, I or Br, and each m is independently 1, 2 or 3 and n is 0 or 1. A more specific example might involve a multi-step process wherein a feedstock of a chlorinated propene is fluorinated in a catalyzed, gas phase reaction to form a compound such as l-chloro-3,3,3-trifluoropropene (1233zd). The l-chloro-2,3,3,3- tetrafluoropropane is then dehydrochlorinated to 2,3,3,3-tetrafluoroprop-l-ene or 1,3,3,3- tetrafluoroprop-l-ene via a catalyzed, gas phase reaction.

[0054] Example I: Bromination of 1,2-dichloropropane to l,2-dichlro-2-bromopropane

[0055] A 100 mL flask equipped with a reflux condenser to return unreacted reactants while allowing removal of HBr byproducts and a Teflon-coated stir bar is flushed with nitrogen and then charged with 1,2-dichloropropane (~3 mL). Stirring is initiated and liquid bromine (-0.3 mL) added. The flask is immersed in a water bath which is gradually heated to ~85 °C and held at this temperature for 16 h. The resulting pale yellow mixture is cooled and concentrated. Analysis by NMR spectroscopy indicates that the product composition is >90% 1,2-dichloro- 2-bromopropane.

[0056] Example II: Halogen exchange of l,2-dichloro-2-bromopropane to 1,2,2- trichloropropane

[0057] A pressure vessel was charged with a 10wt% solution of l,2-dichloro-2-bromo propane dissolved in 1,2-dichloropropane followed by iron chloride (5 mol% relative to 1,2- dichloropropane). Stirring is initiated and anhydrous hydrochloric acid (100 psig) is added. The vessel is gradually heated to 60°C and held at this temperature for 16 h. The resulting mixture is cooled and an aliquot is analyzed by NMR spectroscopy to reveal the formation of 1,2,2-trichloropropane.

Claims

CLAIMS:

1. A process for the production of chlorinated and/or brominated propanes and/or propenes from a feed comprising 1,2-dichloropropane, comprising at least one bromination step.

2. The process of claim 1, wherein the bromination step is conducted in the presence of a free radical catalyst.

3. The process of claim 1, wherein l,2-dichloro-2-bromopropane is produced at a ratio of 90: 10 or higher relative to 1,2-dichloro-l-bromopropane.

4. The process of claim 1 or 3, wherein the process further comprises at least one halogen exchange step.

5. The process of claim 4, wherein the halogen exchange step is conducted in the presence of HQ

6. The process of claim 5, wherein the wherein the halogen exchange step is further conducted in the presence of a Lewis acid comprising AICI₃, FeCl₃, antimony chloride or combinations of these.

7. The process of claim 4, 5 or 6, wherein the halogen exchange step results in the production of 1,2,2-trichloropropane.

8. The process of claim 1, wherein the feed further comprises 1,2,3-trichloropropane.

9. The process of claim 1, further comprising at least one dehydrohalogenation step.

10. The process of claim 9, wherein at least one dehydrohalogenation step occurs in the vapor phase and at least one hydrohalide is recovered from the process as anhydrous hydrohalide.

11. The process of claim 9, wherein at least one dehydrohalogenation step occurs in the liquid phase.

12. The process of claim 9, wherein at least one dehydrohalogenation reaction produces a mixture comprising 1,1,2,3- and 2,3,3,3 TCPE.

13. The process of claim 9, wherein the process results in the production of one or more chlorinated and/or brominated propenes.

14. The process of claim 13, wherein the chlorinated propene comprises 3-4 chlorine atoms.

15. The process of claim 1, wherein at least component of the feed stream is generated within, or upstream of, the process.