Process for the synthesis of 2-chloro-1,3-butadiene and 2,3-dichloro-1,3-butadiene

Abstract

The invention relates to a process for the preparation of a halogenated 1,3-butadiene by dehydrohalogenation of a halogenated 1-butene. Preferably, 2-chloro-1,3-butadiene (CP) is prepared from 3,4-di- chloro-1-butene (3,4-DBN), or 2,3-dichloro-1,3-butadiene (DCB) is prepared from 2,3,4-trichloro-1- butene (TCB). The dehydrohalogenation is performed in the presence of an organic base, preferably selected from (i) non-polymeric organic bases and (ii) polymeric organic bases. Upon dehydrohalogenation of the halogenated 1-butene, the organic base preferably provides an organic halide salt, namely (i) a low melting organic halide salt, which is an ionic liquid; or (ii) a polymeric organic halide salt. Preferably, halogenated 1,3-butadiene is separated from the reaction mixture by in-situ distillation. Organic base is preferably recovered from (i) the low melting organic halide salt by e.g. heating and release of hydrohalogenic acid; or from (ii) the polymeric organic halide salt by e.g. reconversion of polymeric organic halide salt into polymeric organic base and an inorganic halide salt, and size-based separation of the inorganic halide salt, preferably by filtration, more preferably selected from microfiltration, ultrafiltration and nanofiltration, still more preferably by nanofiltration. After purification, recovered organic base is preferably recycled into the process.

Description

Process for the synthesis of 2-chloro-l,3-butadiene and 2,3-dichloro-l,3-butadiene

[0001] Priority is claimed of European patent application no. 24 194 939.5 that was filed on 16 August 2024 and of European patent application no. 25 182 974.3 that was filed on 16 June 2025.

[0002] The invention relates to a process for the preparation of a halogenated 1,3-butadiene by dehydrohalogenation of a halogenated 1-butene. Preferably, 2-chloro-l,3-butadiene (CP) is prepared from 3,4-dichloro-l -butene (3,4-DBN), or 2,3-dichloro-l,3-butadiene (DCB) is prepared from 2,3,4-tri- chloro- 1-butene (TCB). The dehydrohalogenation is performed in the presence of an organic base, preferably selected from (i) non-polymeric organic bases and (ii) polymeric organic bases. Upon dehydrohalogenation of the halogenated 1-butene, the organic base preferably provides an organic halide salt, namely (i) a low melting organic halide salt, which is an ionic liquid; or (ii) a polymeric organic halide salt. Preferably, halogenated 1,3-butadiene is separated from the reaction mixture by in-situ distillation. Organic base is preferably recovered from (i) the low melting organic halide salt by e.g. heating and release of hydrohalogenic acid; or from (ii) the polymeric organic halide salt by e.g. reconversion of polymeric organic halide salt into polymeric organic base and an inorganic halide salt, and size-based separation of the inorganic halide salt, preferably by filtration, more preferably selected from microfiltration, ultrafiltration and nanofiltration, still more preferably by nanofiltration. After purification, recovered organic base is preferably recycled into the process.

[0003] 2-Chloro-l,3-butadiene (CP), 2,3-dichloro-l,3-butadiene (DCB) and related monomers are used for manufacturing chloroprene polymer (CR). 2-Chloro-l,3-butadiene (CP) and 2,3-dichloro-l,3-buta- diene (DCB) can be prepared by dehydrochlorination of 3,4-dichloro-l -butene (3,4-DBN) and 2,3,4- trichloro- 1-butene (TCB), respectively:

[0004] It is known to prepare these monomers in a biphasic process (organic / caustic) by phase transfer catalysis using an organic ammonium chloride NR / Cl as catalyst. The catalyst is subsequently decomposed in the aqueous caustic phase to form an alkali salt solution from which chlorine is recuperated.

[0005] For example, US 4,418,232 relates to a process for dehydrohalogenating a halogenated hydrocarbon to an ethylenically unsaturated product in the presence of a phase-transfer catalyst. US 4,629,816discloses a process wherein 2,3-Dichlorobutadiene-(l,3) is obtained from 2,3,4-trichlorobutene-l by dehydrohalogenation in the presence of a phase transfer catalyst, an inhibitor and oxygen.

[0006] US 5,545,781 relates to a process for producing chloroprene by means of dehydrochlorination of 3, 4-dichloro-l -butene. The dehydrochlorination is carried out in the presence of lime and a primary amine.

[0007] It is also known to use ionic liquids in a wide variety of different industrial processes. For details, reference is made to N.V. Plechkova et al., Chem. Soc. Rev., 2008, 37, 123-150; and A. J. Greer et al., Molecules 2020, 25, 5207, 1-31.

[0008] WO 2002 / 000639 relates to a method for separating acids from chemical reaction mixtures by means of an auxiliary base. Said auxiliary base b) forms a salt with the acid, which is liquid at temperatures at which the valuable product is not significantly decomposed during separation, and c) the salt of the auxiliary base and the valuable product or the solution of the valuable product form two immiscible fluid phases in a suitable solvent.

[0009] WO 2002 / 094740 relates to heterogeneous processes for the hydro-dehalogenation of a compound containing at least one C-Cl, C-Br or C-l bond. The processes comprise reacting said compound with a hydrogenating agent and a heterogeneous hydrogenation catalyst in the presence of an ionic liquid.

[0010] WO 2003 / 062251 relates to a method for producing amino dihalophosphines, diamino halo- phosphines, triamino phosphines, phosphite diamides, amino phosphines, diamino phosphines, phosphite amide halogenides, and amino phosphine halogenides by separating an acid in the presence of an auxiliary base. Said auxiliary base b) forms a salt with an acid, which is liquid at temperatures at which the valuable product is not significantly decomposed during separation of the liquid salt, and c) the salt of the auxiliary base and the valuable product or the solution of the valuable product form two immiscible phases in a suitable solvent.

[0011] WO 2005 / 061416 relates to a method for isolating acids from chemical reaction mixtures by means of an auxiliary base, whereby this auxiliary base: b) forms a salt with the acid, which is liquid at temperatures at which the valuable product is not significantly decomposed during the isolation of the liquid salt, and; c) the salt of the auxiliary base, together with the valuable product or with the solution of the valuable product, forms, in a suitable solvent, two non-mixable liquid phases.

[0012] BASF's patented BASIL process (Biphasic Acid-Scavenging utilizing Ionic Liquids) is probably the most widely known and recognized example of industrial implementation of an ionic liquid-based process. The BASIL process is commercially important because of the significant process improvements realized versus the prior process. In the latter, acid scavenging in the reaction was achieved using alkylamines, like triethylamine, forming the protonated trialkyl ammonium halide salt. This product is athick, dense, insoluble slurry that is difficult to handle and remove from the reactor, resulting in inefficienciesand the need for a processing solvent. By utilizing the ionic liquid precursor, 1 -methylimidazole, as an alternative to triethylamine, the acid reaction forms 1-methylimidazolium chloride, a protic ionic liquid with a low melting point (75°C) which separates and forms a biphasic system in the reaction vessel. The lower phase being comprised of pure ionic liquid can readily be removed, resulting in easy isolation of the upper phase product. Furthermore, the ionic liquid can be recycled by deprotonation, regenerating the 1 -methylimidazole reactant (M.A. Benvenuto et al., Green Chemistry in Industry, DeGruyter, 2018, pages 44-45).

[0013] US 5 545 781 A discloses a process for producing chloroprene via the dehydrochlorination of 3,4-dichloro-l -butene (DCB) using lime and a primary amine as reagents. The amine with the general formula R-NH2, (R is a Cl to C15 hydrocarbon) also serves as a reaction medium. During dehydrochlorination the amine forms a hydrochloride which is recycled to the amine by reaction with lime (CaO). The process can be carried out in a single step (with lime and amine present simultaneously) or in two steps, where the amine hydrochloride is subsequently treated with lime to regenerate the amine. Compared to conventional sodium hydroxide-based methods it is claimed that this approach reduces costs and byproduct formation while maintaining high conversion and selectivity. The reaction operates efficiently at 30-70 °C and enables isolation of both chloroprene via distillation.

[0014] DE 20 14195 Al describes a process for producing chloroprene monomer with a reduced acetaldehyde content by dehydrochlorination 3,4-dichloro-l -butene by employing an aqueous alkali metal hydroxide solution in conjunction with an ammonium ion donor. As ammonium ion donor ammonium chloride, ammonium acetate, ammonium nitrate, ammonium sulfate and also aqueous ammonia are used. It is claimed that employing said ammonium compounds suppress formation of acetaldehyde during dehydrochlorination.

[0015] DE 24 14855 Al discloses a continuous process for producing chloroprene by reacting 3,4- dichloro-l -butene with ammonia in a high-boiling polar solvent such as dimethylformamide or dimethylsulfoxide at 50-90°C. Residual ammonia and side product ammonium chloride are separated by flash evaporation at a temperature of 30 to 40°C which prevents fouling of ammonium chloride in the distillation columns. Chloroprene is purified and separated from residual ammonia by distillation. It is claimed that omitting water in the process prevents corrosion, reduces polymerization risk and enables recovery of ammonium chloride as a solid.

[0016] JPS 61 29938 B2 describes the production of chloroprene by reacting 3,4-dichloro-l -butene- 1 with ammonia in high-boiling polar solvents such as dimethylformamide, dimethylsulfoxide and formamide. Ammonia is recovered by evaporation upon pressure reduction, which simultaneously induces crystallization of ammonium chloride from the reaction medium. It is claimed that this approach avoids slurry deposition in reactors and enables a continuous process which is more energy efficient than conventional methods and allows better separation of by-products.

[0017] EP 4 063 005 Al discloses a novel superhydrophobic fluorosilicone rubber membrane and its application in the purifying wastewater resulting from the production of methylene diphenyl diisocyanate. The membrane allows permeation and removal of amines (e.g. aniline, polyamines) present in the wastewater resulting in sufficient purity to process the wastewater by biochemical treatment.

[0018] KR 2020 0101456 A, KR 2020 0113255 A and KR 2020 0113262 A disclose a multi-stage filtration and purification systems to produce high-purity chemical solutions for semiconductor manufacturing. The systems combine several different filter materials to remove particles and gels (by size exclusion through porous materials), trace metals and ions (using ion exchange membranes) and microscopic gels (by adsorption). The resulting purified solutions are claimed to reduce defect formation in lithography, etching and wafer cleaning processes.

[0019] The processes of the prior art for producing halogenated 1,3-butadienes are not satisfactory in every respect because they have high complexity and high energy demand. The processes suffer from low reactivity (e.g., space-time-yield: 2-chloro-l,3-butadiene (CP): 0.36 t / h m3; 2,3-dichloro-l,3-buta- diene (DCB): 0.04 t / h m3). Further, in the course of the preparation due to the employed phase transfer catalyst, a suspension and a sludge are formed that are difficult to separate. Still further, regeneration of the caustic solution is costly.

[0020] The processes of the prior art rely upon complex chemistry for dehydrohalogenation based on two phases with the need of a phase transfer agent (without recycling the catalyst). The resulting aqueous phase needs to be treated internally by complex equipment and high operational costs. The processes are moreover very sensitive to changing conditions and frequently lead to process issues.

[0021] There is a demand for processes for the preparation of halogenated 1,3-butadienes from halogenated 1 -butenes that overcome at least some of the drawbacks of the prior art.

[0022] It is an object of the invention to provide processes for the preparation of halogenated 1,3-butadienes from halogenated 1 -butenes that have advantages compared to the processes of the prior art. The processes should preferably be simplified, more efficient and safer.

[0023] This object has been achieved by the subject-matter of the patent claims.

[0024] It has been surprisingly found that the above advantages can be achieved by a different reaction scheme using an organic base, preferably selected from non-polymeric organic bases and polymeric organic bases. The organic base forms an organic halide salt with eliminated hydrohalogenic acid.

[0025] In preferred embodiments, the organic base is non-polymeric. Upon dehydrohalogenation of the halogenated 1 -butene, the organic base preferably provides a low melting organic halide salt, preferably an organic salt melting below 100°C, which is an ionic liquid.

[0026] In other preferred embodiments, the organic base is polymeric. Examples of polymeric organic bases include but are not limited to polypropylene imines, polyvinyl amines, polyvinylpyrrolidones, polyacrylates, polyethylene imines, or the like, polyethylene imines (PEI) are particularly preferred.Upon dehydrohalogenation of the halogenated 1 -butene, the organic base preferably provides a polymeric organic halide salt.

[0027] The suspension forming phase transfer catalyst of the prior art is avoided while simultaneously providing a process that is more efficient due to the reduction of in-between steps.

[0028] Further, it has been surprisingly found that production for both 2 -chloro- 1,3 -butadiene (CP) and 2,3-dichloro-l,3-butadiene (DCB) can be streamlined with a simplified chemistry at lower equipment and energy costs. This is basically related to wastewater or brine generation and handling. The consumption of fresh water is reduced.

[0029] Compared to the processes of the prior art, the process according to the invention has at least some, preferably all of the following advantages:(i) recycle of auxiliary raw materials, e.g., organic base, organic halide salt or ionic liquid can be recycled; cleaved hydrohalogenic acid or a halide salt thereof can be recovered and used e.g. in other process steps like coagulation, for recovering the halogen in a subsequent step or as a value stream that it sold externally;(ii) lower volume of raw material supply and reduced logistic complexity, e.g., with respect to a phase transfer agent, sodium hydroxide, and hydrochloric acid;(iii) energy savings e.g. with respect to steam for saline and steam for wastewater stripping;(iv) environmental and occupational benefits, e.g., with respect to improved safety due to less holdup within reactors; less freshwater consumption for reaction; elimination of wastewater production and salt freight; no issue regarding total organic carbon (TOC) in wastewater; reduction of waste e.g. phase transfer agent sludge; replacement of hazardous materials; and less manual work for filling of chemicals and process aids (e.g. phase transfer catalyst);(v) less operational complexity, e.g., no or simplified caustic water treatment; difficult and complex to operate, vulnerable process with sludge and sludge treatment; smaller Dehydrohalogenation equipment, less maintenance efforts due to clean process;(vi) increased space-time-yield;(vii) optimization of synthesis.

[0030] A first aspect of the invention relates to a process for the preparation of a halogenated 1,3- butadiene of general formula (I)whereinR means -H or Hal; andINCORPORATED BY REFERENCE (RULE 20.6)Hal independently means -Cl, -Br or -I; preferably -Cl; said process comprising the steps of:(a) providing a reaction mixture containing or essentially consisting of- a halogenated 1 -butene of general formula (II)whereinR means -H or Hal; andHal independently means -Cl, -Br or -I; preferably -Cl;- an organic base, preferably selected from non-polymeric organic bases and polymeric organic bases; and- optionally a catalyst; and- optionally water; and(b) eliminating hydrohalogenic acid from the halogenated 1 -butene to produce the halogenated 1,3- butadiene; and forming an organic halide salt of the eliminated hydrohalogenic acid with the organic base; preferably wherein a low melting organic halide salt, preferably an ionic liquid, is obtained in the reaction mixture when the organic base is a non-polymeric organic base; and preferably wherein a polymeric organic halide salt is obtained in the reaction mixture when the organic base is a polymeric organic base;(c) optionally, separating at least a portion of the halogenated 1,3 -butadiene from the reaction mixture by in-situ distillation;(d) separating the reaction mixture into- a product composition containing halogenated 1,3 -butadiene and optionally residual halogenated 1 -butene; and- an organic halide salt composition containing organic halide salt of the eliminated hydrohalogenic acid with organic base and optionally residual organic base;(e) optionally, purifying the halogenated 1,3 -butadiene that is contained in the product composition; optionally together with the portion of the halogenated 1,3 -butadiene optionally separated in step (c);(f) cleaving the organic halide salt that is contained in the organic halide salt composition to release hydrohalogenic acid from the organic halide salt, and separating the organic halide salt composition into- a hydrohalogenic acid composition containing released hydrohalogenic acid, or an inorganic halide salt composition containing an inorganic halide salt; andINCORPORATED BY REFERENCE (RULE 20.6)Upon dehydrohalogenation of the halogenated 1 -butene, the organic base preferably provides a polymeric organic halide salt.

[0027] The suspension forming phase transfer catalyst of the prior art is avoided while simultaneously providing a process that is more efficient due to the reduction of in-between steps.

[0028] Further, it has been surprisingly found that production for both 2-chloro-l,3-butadiene (CP) and 2,3-dichloro-l,3-butadiene (DCB) can be streamlined with a simplified chemistry at lower equipment and energy costs. This is basically related to wastewater or brine generation and handling. The consumption of fresh water is reduced.

[0029] Compared to the processes of the prior art, the process according to the invention has at least some, preferably all of the following advantages:(i) recycle of auxiliary raw materials, e.g., organic base, organic halide salt or ionic liquid can be recycled; cleaved hydrohalogenic acid or a halide salt thereof can be recovered and used e.g. in other process steps like coagulation, for recovering the halogen in a subsequent step or as a value stream that it sold externally;(ii) lower volume of raw material supply and reduced logistic complexity, e.g., with respect to a phase transfer agent, sodium hydroxide, and hydrochloric acid;(iii) energy savings e.g. with respect to steam for saline and steam for wastewater stripping;(iv) environmental and occupational benefits, e.g., with respect to improved safety due to less holdup within reactors; less freshwater consumption for reaction; elimination of wastewater production and salt freight; no issue regarding total organic carbon (TOC) in wastewater; reduction of waste e.g. phase transfer agent sludge; replacement of hazardous materials; and less manual work for filling of chemicals and process aids (e.g. phase transfer catalyst);(v) less operational complexity, e.g., no or simplified caustic water treatment; difficult and complex to operate, vulnerable process with sludge and sludge treatment; smaller Dehydrohalogenation equipment, less maintenance efforts due to clean process;(vi) increased space-time-yield;(vii) optimization of synthesis.

[0030] A first aspect of the invention relates to a process for the preparation of a halogenated 1,3- butadiene of general formula (I)whereinR means -H or Hal; andERRONEOUSLY FILED (RULE 20.5bis)Hal independently means -Cl, -Br or -I; preferably -Cl; said process comprising the steps of:(a) providing a reaction mixture containing or essentially consisting of- a halogenated 1 -butene of general formula (II)whereinR means -H or Hal; andHal independently means -Cl, -Br or -I; preferably -Cl;- an organic base, preferably selected from non-polymeric organic bases and polymeric organic bases; and- optionally a catalyst; and- optionally water; and(b) eliminating hydrohalogenic acid from the halogenated 1 -butene to produce the halogenated 1,3- butadiene; and forming an organic halide salt of the eliminated hydrohalogenic acid with the organic base; preferably wherein a low melting organic halide salt, preferably an ionic liquid, is obtained in the reaction mixture when the organic base is a non-polymeric organic base; and preferably wherein a polymeric organic halide salt is obtained in the reaction mixture when the organic base is a polymeric organic base;(c) optionally, separating at least a portion of the halogenated 1,3 -butadiene from the reaction mixture by in-situ distillation;(d) separating the reaction mixture into- a product composition containing halogenated 1,3 -butadiene and optionally residual halogenated 1 -butene; and- an organic halide salt composition containing organic halide salt of the eliminated hydrohalogenic acid with organic base and optionally residual organic base;(e) optionally, purifying the halogenated 1,3 -butadiene that is contained in the product composition; optionally together with the portion of the halogenated 1,3-butadiene optionally separated in step (c);(f) cleaving the organic halide salt that is contained in the organic halide salt composition to release hydrohalogenic acid from the organic halide salt, and separating the organic halide salt composition into- a hydrohalogenic acid composition containing released hydrohalogenic acid, or an inorganic halide salt composition containing an inorganic halide salt; andERRONEOUSLY FILED (RULE 20.5bis)- an organic base composition containing organic base;(g) optionally, purifying the organic base that is contained in the organic base composition thereby obtaining purified organic base; and(h) recycling the organic base composition or the purified organic base to the reaction mixture.

[0031] The process according to the invention is drawn to the preparation of a halogenated 1,3-butadi- ene of general formula (I).

[0032] Preferably, the halogenated 1-buten is a 4-halo-l-buten, wherein R and R' independently of one another mean hydrogen or halogen, preferably hydrogen or Cl:

[0033] Preferably, R means Cl.

[0034] Preferably, R means hydrogen or Cl.

[0035] In preferred embodiments, the halogenated 1-buten is 3,4-dichloro-l -butene (3,4-DBN) and the halogenated 1,3-butadiene is 2-chloro-l,3-butadiene (CP):

[0036] In other preferred embodiments, the halogenated 1-buten is 2,3,4-trichloro-l-butene (TCB) and the halogenated 1,3-butadiene is 2, 3 -dichloro- 1,3 -butadiene (DCB):

[0037] Depending upon the nature of the organic base, either non-polymeric organic base or polymeric organic base, step (f) and optional step (g) may involve different measures and work up procedures. When the organic base is non-polymeric, optional step (g) preferably involves rectification. When the organic base is polymeric, optional step (g) preferably involves a size-based separation methodology, preferably selected from microfiltration, ultrafiltration and nanofiltration, more preferably by nanofil- tration.

[0038] Step (a):

[0039] In step (a) of the process according to the invention, a reaction mixture is provided that contains or essentially consisting of a halogenated 1-butene of general formula (II); an organic base, preferably selected from non-polymeric organic bases and polymeric organic bases; optionally a catalyst; and optionally water.

[0040] Preferably, the reaction mixture has a water content of not more than 60 wt.-%, preferably not more than 50 wt.-%, more preferably not more than 40 wt.-%, still more preferably not more than 30 wt.-%, yet more preferably not more than 20 wt.-%, and even more preferably not more than 10 wt.-%, in each case relative to the total weight of the reaction mixture.

[0041] Preferably, the reaction mixture has a water content of not more than 8 wt.-%, preferably not more than 7 wt.-%, more preferably not more than 6 wt.-%, still more preferably not more than 5 wt.- %, yet more preferably not more than 4 wt.-%, even more preferably not more than 3 wt.-%, most preferably not more than 2 wt.-%, and in particular not more than 1 wt.-%, in each case relative to the total weight of the reaction mixture, or is essentially free of water; preferably the total process is performed essentially in the absence of water.

[0042] Preferably, the reaction mixture has a solvent content of not more than 8 wt.-%, preferably not more than 7 wt.-%, more preferably not more than 6 wt.-%, still more preferably not more than 5 wt.- %, yet more preferably not more than 4 wt.-%, even more preferably not more than 3 wt.-%, most preferably not more than 2 wt.-%, and in particular not more than 1 wt.-%, in each case relative to the total weight of the reaction mixture, or is essentially free of solvent; preferably the total process is performed essentially in the absence of solvent; preferably the total process is performed essentially in the absence of solvent.

[0043] Preferably, the reaction mixture has a content of the organic base, preferably polymeric organic base, more preferably polyethylene imine (PEI) of at least 35 wt.-%, preferably at least 40 wt.-%, more preferably at least 45 wt.-%, still more preferably at least 50 wt.-%, yet more preferably at least 55 wt.- %, and even more preferably at least 60 wt.-%, in each case relative to the total weight of the reaction mixture.

[0044] Preferably, the conjugate acid of the organic base, preferably selected from non-polymeric organic bases and polymeric organic bases, has an aqueous PKA value at 25°C of at least 7.0, preferably at least 7.5, more preferably at least 8.0, still more preferably at least 8.5, yet more preferably at least 9.0, even more preferably at least 9.5, most preferably at least 10.0, and in particular at least 10.5.

[0045] Preferably, the conjugate acid of the organic base, preferably selected from non-polymeric organic bases and polymeric organic bases, has an aqueous PKA value at 25°C of at most 14.0, preferably at most 13.5, more preferably at most 13.0, still more preferably at most 12.5, yet more preferably at most 12.0, even more preferably at most 11.5, most preferably at most 11.0, and in particular at most

[0046] Preferably, the conjugate acid of the organic base, preferably selected from non-polymeric organic bases and polymeric organic bases, has an aqueous PKA value at 25 °C of at most 12.4, preferably at most 12.2, more preferably at most 12.0, still more preferably at most 11.8, yet more preferably at most 11.6, even more preferably at most 11.4, most preferably at most 11.2, and in particular at most 11.0.

[0047] Preferably, the organic base contains a nitrogen atom that upon addition of hydrohalogenic acid forms an ammonium salt. Preferably, such formation is reversible, i.e., the thus formed ammonium salt may later be cleaved (decomposed) into the organic base and the hydrohalogenic acid in step (f) of the process according to the invention.

[0048] In preferred embodiments, the organic base is non-polymeric.

[0049] Preferably, the non-polymeric organic base is an amine or hydroxylamine; preferably a primary amine, a primary hydroxyl amine, a secondary amine, a secondary hydroxyl amine, a tertiary amine, or a tertiary hydroxyl amine; preferably a di(C i _i 2-alkyl) or a tri(Ci-i2-alkyl)amine; more preferably a di(Ci. e-alkyl) or a tri(Ci-6-alkyl)amine; still more preferably di-(2-ethylhexyl)amine, triethylamine, tributylamine, or trioctylamine. Preferably, the conjugate acid of the amine or hydroxylamine has an aqueous PKA value at 25°C of at most 12.4, preferably at most 12.2, more preferably at most 12.0, still more preferably at most 11.8, yet more preferably at most 11.6, even more preferably at most 11.4, most preferably at most 11.2, and in particular at most 11.0.

[0050] Preferred primary amines according to the invention include but are not limited to methylamine, ethylamine, n-propylamine, isopropylamine, n-butylamine, sec-butylamine, isobutylamine, tert-butyla- mine, n-pentylamine, neopentylamine, n-hexylamine, n-heptylamine, n-octylamine, n-nonylamine, and n-decylamine.

[0051] Preferred secondary amines according to the invention include but are not limited to dimethylamine, methylethylamine, diethylamine, methylpropylamine, ethylpropylamine, dipropylamine, methylbutylamine, ethylbutylamine, dibutylamine, methylpentylamine, dipentylamine, and dihexylamine.

[0052] Preferred tertiary amines according to the invention include but are not limited to trimethylamine, dimethylethylamine, diethylmethylamine, triethylamine, dimethylpropylamine, methyl diethylamine, tripropylamine, methyl dibutylamine, tributylamine, and trimethylpentylamine.

[0053] Preferably, the non-polymeric organic base is a primary diamine, a secondary diamine, or a tertiary diamine; preferably a tertiary diamine; more preferably (Ci-4-alkyl)2N-(CH2)2-6-N(Ci-4-alkyl)2; still more preferably tetramethyl ethylene diamine (TMEDA). Preferably, the conjugate acid of the primary diamine, a secondary diamine, or a tertiary diamine has an aqueous PKA value at 25 °C of at most 12.4, preferably at most 12.2, more preferably at most 12.0, still more preferably at most 11.8, yet morepreferably at most 11.6, even more preferably at most 11.4, most preferably at most 11.2, and in particular at most 11.0.

[0054] Preferably, the non-polymeric organic base is a heteroaromatic compound; preferably an imidazole; more preferably an alkyl imidazole; still more preferably l-(Ci-6-alkyl)-imidazole; yet more preferably 1-methyl imidazole or 1-butyl imidazole. Preferably, the conjugate acid of the heteroaromatic compound has an aqueous PKA value at 25 °C of at most 12.4, preferably at most 12.2, more preferably at most 12.0, still more preferably at most 11.8, yet more preferably at most 11.6, even more preferably at most 11.4, most preferably at most 11.2, and in particular at most 11.0.

[0055] Preferably, the non-polymeric organic base is a bicyclic compound; preferably a diazabicyclic compound; more preferably l,8-diazabicyclo[5.4.0]undec-7-en (DBU), l,5-diazabicyclo[4.3.0]non-5- en (DBN), (1,4-diazabicyclo [2.2.2]octane (DABCO), or the like. Preferably, the conjugate acid of the bicyclic compound has an aqueous PKA value at 25°C of at most 12.4, preferably at most 12.2, more preferably at most 12.0, still more preferably at most 11.8, yet more preferably at most 11.6, even more preferably at most 11.4, most preferably at most 11.2, and in particular at most 11.0.

[0056] In other preferred embodiments, the organic base is polymeric.

[0057] Preferably, the polymeric organic base is selected from the group consisting of polypropylene imines, polyvinyl amines, polyvinylpyrrolidones, polyacrylates, polyethylene imines, or the like. Polyethylene imines (PEI) are particularly preferred.

[0058] Preferably, the conjugate acid of the polymeric organic base has an aqueous PKA value at 25°C of at most 12.4, preferably at most 12.2, more preferably at most 12.0, still more preferably at most 11.8, yet more preferably at most 11.6, even more preferably at most 11.4, most preferably at most 11.2, and in particular at most 11.0.

[0059] Preferably, the catalyst is selected from (i) trialkyl phosphonium salts; preferably tributyl phosphonium salts; more preferably tributyl phosphonium hydrochlorides; (ii) tetraalkyl phosphonium salts; preferably tetrabutyl phosphonium salts; more preferably tetrabutyl phosphonium chloride; (iii) ammonium salts; and (iv) tetraalkyl ammonium salts; preferably tetrabutyl ammonium salts; more preferably tetrabutyl ammonium chloride.

[0060] Preferably, the catalyst forms in situ between the organic base and hydrohalogenic acid that is eliminated in step (b) (autocatalysis).

[0061] In preferred embodiments, the reaction mixture provided in step (a) is monophasic.

[0062] In other preferred embodiments, the reaction mixture provided in step (a) is biphasic having a first phase and a second phase.

[0063] Preferably, the majority of the halogenated 1-butene is contained in the first phase, and the majority of the organic base is contained in the second phase.

[0064] Step (b):

[0065] In step (b) of the process according to the invention, hydrohalogenic acid is eliminated from the halogenated 1-butene to produce the halogenated 1,3-butadiene; and an organic halide salt of the eliminated hydrohalogenic acid is formed with the organic base.

[0066] The halide that is incorporated in the organic halide salt corresponds to the halide that was incorporated in the halogenated 1-butene and that was subject to dehydrohalogenation: organic halide saltCP

[0067] In preferred embodiments, when the organic base is a non-polymeric organic base, a low melting organic halide salt, preferably an ionic liquid, is obtained as organic halide salt in the reaction mixture.

[0068] In other preferred embodiments, when the organic base is a polymeric organic base, a polymeric organic halide salt is obtained as organic halide salt in the reaction mixture.

[0069] In preferred embodiments, the reaction mixture obtained in step (b) is monophasic.

[0070] In other preferred embodiments, the reaction mixture obtained in step (b) is biphasic having a first phase and a second phase.

[0071] In further preferred embodiments, the reaction mixture obtained in step (b) is triphasic having a first phase, a second phase, and a third phase.

[0072] Preferably, the majority of the halogenated 1,3-butadiene and optionally the majority of residual halogenated 1-butene is contained in the first phase, and the majority of the organic halide salt and optionally the majority of residual organic base is contained in the second phase.

[0073] Preferably, step (b) is operated as batch-reaction, semi-batch-reaction and continuous reaction.

[0074] Preferably, step (b) is performed under boiling conditions.

[0075] Preferably, step (b) is performed at a temperature within the range of from -50 to 300°C.

[0076] Preferably, step (b) is performed at a temperature within the range of from 20 to 100°C, preferably 20 to 90°C, more preferably 20 to 80°C, still more preferably 20 to 70°C; preferably the halogenated 1-buten is 3,4-dichloro- 1-butene (3,4-DBN) and the halogenated 1,3-butadiene is 2-chloro-l,3-bu- tadiene (CP).

[0077] Preferably, step (b) is performed at a temperature within the range of from -30 to 10°C, preferably -20 to 10°C, more preferably -10 to 10°C, still more preferably 0 to 10°C; preferably the halogenated 1-buten is 2,3,4-trichloro-l -butene (TCB) and the halogenated 1,3-butadiene is 2,3-dichloro-l,3- butadiene (DCB).

[0078] Preferably, step (b) is performed at a pressure within the range of from 0 to 16 bara; preferably 1 to 6 bara.

[0079] Preferably, step (b) is performed in a dehydrohalogenation reactor and in a residence time reactor which is arranged downstream of the dehydrohalogenation reactor.

[0080] Step (c):

[0081] In optional step (c) of the process according to the invention, at least a portion of the halogenated 1,3-butadiene is separated from the reaction mixture by in-situ distillation.

[0082] Preferably, the reaction mixture obtained in step (b) is monophasic and in step (c) at least a portion of the halogenated 1,3-butadiene is separated from the reaction mixture by in-situ distillation.

[0083] Preferably, the reaction mixture obtained in step (b) is biphasic and in step (c) at least a portion of the halogenated 1,3-butadiene is separated from the reaction mixture by in-situ distillation.

[0084] Step (d):

[0085] In step (d) of the process according to the invention, the reaction mixture is separated into a product composition containing halogenated 1,3-butadiene and optionally residual halogenated 1-bu- tene; and an organic halide salt composition containing organic halide salt of the eliminated hydrohalo- genic acid with organic base and optionally residual organic base: reaction mixture - * product composition + organic halide salt composition

[0086] In preferred embodiments, when the organic base is a non-polymeric organic base, the organic halide salt in the organic halide salt composition is a low melting organic halide salt, preferably an ionic liquid.

[0087] In other preferred embodiments, when the organic base is a polymeric organic base, the organic halide salt in the organic halide salt composition is a polymeric organic halide salt.

[0088] In preferred embodiments, the reaction mixture obtained in step (b) is monophasic and in step (d) the product composition is separated from the organic halide salt composition by gas / liquid phase separation, preferably in-situ distillation; preferably the halogenated 1-buten is 3,4-dichloro-l -butene (3,4-DBN) and the halogenated 1,3-butadiene is 2-chloro-l,3-butadiene (CP).

[0089] In other preferred embodiments, the reaction mixture obtained in step (b) is biphasic and in step (d) the product composition is separated from the organic halide salt composition by liquid / liquid phase separation or solid / liquid phase separation.

[0090] Preferably, phase separation involves coalescing separation, centrifuging, decanting, filtration, or any combination thereof.

[0091] Preferably, step (d) is operated as batch-reaction, semi-batch-reaction and continuous reaction.

[0092] Preferably, in step (d) the product composition is recycled to the reaction mixture.

[0093] Preferably, step (d) is performed at a temperature within the range of from -50 to 300°C.

[0094] Preferably, step (d) is performed at a temperature within the range of from -40 to 20°C, preferably -30 to 20°C, more preferably -20 to 20°C, still more preferably -10 to 20°C; preferably the halogenated 1-buten is 2,3,4-trichloro-l -butene (TCB) and the halogenated 1,3-butadiene is 2,3-dichloro- 1,3-butadiene (DCB).

[0095] Preferably, step (d) is performed at a pressure within the range of from 0 to 16 bara; preferably 1 to 6 bara.

[0096] Step (e):

[0097] In optional step (e) of the process according to the invention, the halogenated 1,3-butadiene that is contained in the product composition is purified; optionally together with the portion of the halogenated 1,3-butadiene optionally separated in step (c).

[0098] Preferably, in step (e) residual halogenated 1-butene is recycled to the reaction mixture.

[0099] Step (f):

[0100] In step (f) of the process according to the invention, the organic halide salt that is contained in the organic halide salt composition is cleaved to release hydrohalogenic acid from the organic halide salt, and the organic halide salt composition is separated into- a hydrohalogenic acid composition containing released hydrohalogenic acid, or an inorganic halide salt composition containing an inorganic halide salt; and- an organic base composition containing organic base.

[0101] When the organic halide salt is cleaved, both hydrohalogenic acid and organic base are released.

[0102] Cleavage of the organic halide salt may be achieved catalytically or thermally. The best mode of cleavage may depend upon the nature of the organic base. The released hydrohalogenic acid may be the free acid or may in turn be captured in form of an inorganic halide salt.

[0103] Halide salts of polymeric organic bases or of non-polymeric organic bases may both be cleaved into organic base and inorganic halide salt. This is preferably achieved by alkaline processing with an inorganic base that is a stronger base than the organic base, e.g. sodium hydroxide or potassium hydroxide: organic halide salt + inorganic base organic base + inorganic halide salt

[0104] Under these circumstances, the hydrohalogenic acid that is released from the organic halide salt reacts with the inorganic base to afford an inorganic halide salt and water. For example, when the halide is chloride and the inorganic base is sodium hydroxide, the inorganic halide salt will be sodium chloride.

[0105] In preferred embodiments, especially when the organic base is a non-polymeric organic base and the organic halide salt that is contained in the organic halide salt composition is a low melting organic halide salt, preferably an ionic liquid, the organic halide salt composition is separated into- a hydrohalogenic acid composition containing released hydrohalogenic acid; and- an organic base composition containing organic base.

[0106] In other preferred embodiments, especially when the organic base is a polymeric organic base and the organic halide salt in the organic halide salt composition is a polymeric organic halide salt, the organic halide salt composition is separated into- an inorganic halide salt composition containing an inorganic halide salt; and- an organic base composition containing organic base.

[0107] Preferably, step (f) is operated as batch-reaction, semi-batch-reaction and continuous reaction.

[0108] Preferably, step (f) is performed at a temperature within the range of from -50 to 300°C, preferably 0 to 300°C, more preferably 70 to 300°C. For 2-chloro-l,3-butadiene (CP), the temperature range of from 70 to 300°C is particularly preferred, whereas for 2,3-dichloro-l,3-butadiene (DCB) step (f) can also be performed at lower temperature.

[0109] Depending upon the nature of the organic base, i.e. either (i) a non-polymeric organic base providing upon dehydrohalogenation of the halogenated 1 -butene a low melting organic halide salt / ionic liquid, or (ii) a polymeric organic base providing upon dehydrohalogenation of the halogenated 1 -butene a polymeric organic halide salt, step (f) is preferably operated under different conditions.

[0110] In preferred embodiments, the organic base is a non-polymeric organic base and step (f) is preferably operated under the following conditions:

[0111] Preferably, the organic base is an amine or hydroxyl amine and wherein step (f) is performed at a temperature that is above the melting temperature of the base under the given conditions.

[0112] Preferably, the organic base is an imidazole and wherein step (f) is performed at a temperature that is above the melting temperature of the organic base under the given conditions.

[0113] Preferably, step (f) is performed at a pressure within the range of from 0 to 16 bara; preferably 0.1 to 6 bara.

[0114] In other preferred embodiments, the organic base is a polymeric organic base and step (f) is preferably operated under the following conditions:

[0115] Preferably, step (f) involves alkaline processing and separation, preferably precipitation, preferably separation of inorganic halide salt, more preferably by means of a non-aqueous solvent, most preferably without solvent. Suitable non-aqueous solvents include but are not limited to alcohols such as methanol, ethanol, isopropanol, and the like.

[0116] Preferably, step (f) involves alkaline processing and separation, preferably by fdtration, more preferably by precipitation and subsequent fdtration.

[0117] Preferably, the polymeric organic halide salt is reconverted (cleaved) into polymeric organic base and an inorganic halide salt. This is preferably achieved by alkaline processing with an inorganic base that is a stronger base than the polymeric organic base, e.g. sodium hydroxide or potassium hydroxide.

[0118] For example, when the organic base is a polymeric organic base selected from polyethylene imines (PEI), upon dehydrohalogenation of the halogenated 1 -butene, a polyethylene imine halogenate salt is formed, e.g. polyethylene imine hydrochloride. Alkaline processing with an inorganic base, e.g. sodium hydroxide, reconverts the polymeric organic halogenate salt, e.g. polyethylene imine hydrochloride, into the polymeric organic base, e.g. polyethylene imine, and the corresponding inorganic halide salt of the halogenate (anion) and the inorganic base (cation), e.g. sodium chloride.

[0119] The inorganic halide salt, e.g. sodium chloride, typically has high purity and is preferably recovered. It may be used elsewhere or commercialized.

[0120] The polymeric organic base is preferably recovered and recycled.

[0121] Polymeric organic halide salt is thus preferably subjected to alkaline processing thereby providing polymeric organic base and inorganic halide salt.

[0122] By means of a non-aqueous solvent, the solubility of the inorganic halide salt may be reduced, whereas the polymeric organic base remains in solution. Under suitable conditions, e.g. by adding a suitable amount of a non-aqueous solvent as antisolvent, the inorganic halide salt can thus be selectively precipitated, and subsequently separated from the supernatant by solid-liquid separation such as fdtration. In preferred embodiments, the inorganic halide salt spontaneously precipitates from aqueous solution in the absence of a non-aqueous solvent as antisolvent.

[0123] Preferably, the concentration of the polymeric organic base is high enough so that upon alkaline processing the amount of the thus released inorganic halide salt is above its saturation concentration thereby inducing spontaneous precipitation of the inorganic halide salt.

[0124] Preferably, the thus obtained supernatant contains in solution the majority of the polymeric organic base, and possibly residual inorganic halide salt, whereas the thus obtained precipitate contains the majority of the inorganic halide salt, and possibly residual polymeric organic base:supernatant (majority of polymeric organic base + residual inorganic halide salt )precipitate(majority of inorganic halide salt + residual polymeric organic base)

[0125] Preferably, the inorganic halide salt is a solid (precipitate) that is preferably separated from the polymeric organic base (supernatant) by solid-liquid separation. Preferably, the precipitate is separated from the supernatant by sedimentation (e.g. centrifuging, decanting process, filtration, and the like).

[0126] It is also contemplated that the inorganic halide salt is separated from the polymeric organic base by a size-based separation methodology, preferably selected from microfiltration, ultrafiltration and nanofiltration, more preferably by nanofiltration.

[0127] After solid-liquid separation of supernatant and precipitate, both may separately of one another be subjected to purification.

[0128] Step (g):

[0129] In optional step (g) of the process according to the invention, the organic base that is contained in the organic base composition is purified thereby obtaining purified organic base. In a secondary process stream, the residual inorganic halide salt that is contained in the organic base composition is purified thereby obtaining purified inorganic halide salt.

[0130] Optional step (g) may involve several measures that typically depend upon the nature of the organic base, non-polymeric vs. polymeric.

[0131] When the organic base is a non-polymeric organic base, removal of impurities having a higher boiling point than the non-polymeric organic base can be achieved by rectification. Thus, in preferred embodiments, in step (g) the organic base that is contained in the organic base composition is purified by rectification.

[0132] When the organic base is a polymeric organic base, purification of the organic base that is contained in the organic base composition preferably involves alkaline processing, whereas the inorganic halide salt is preferably separated from the polymeric organic base by precipitation (see above step (f)) and the thus obtained precipitate contains inorganic halide salt and residual organic base. Under these circumstances, the precipitate (mixed solid) is preferably the composition to be purified in step (g).

[0133] For this purpose, the precipitate is preferably dissolved in water and residual polymeric organic base that is contained in the thus obtained solution is purified by a size-based separation methodology, preferably by filtration, more preferably selected from microfiltration, ultrafiltration and nanofiltration, still more preferably by nanofiltration. Preferably, the residual polymeric organic base is recovered by said size-based separation methodology.

[0134] In preferred embodiments, the supernatant containing in solution the majority of the polymeric organic base, and possibly residual inorganic halide salt, is not further purified but directly subjected to step (h).

[0135] In other preferred embodiments, the supernatant containing in solution the majority of the polymeric organic base, and possibly residual inorganic halide salt, is purified in step (g) in order to further reduce the content of residual inorganic halide salt (supernatant = organic base composition), before the thus purified polymeric organic base is subjected to step (h).

[0136] In preferred embodiments, the precipitate containing the majority of the inorganic halide salt, and possibly residual polymeric organic base, is purified in step (g), preferably by a size-based separation methodology, more preferably filtration, still more preferably selected from microfiltration, ultrafiltration and nanofiltration, yet more preferably by nanofiltration (precipitate = organic base composition), before the thus purified polymeric organic base is subjected to step (h) (see below).

[0137] Such purification of the precipitate may serve different purposes. On the one hand, the content of residual inorganic halide salt may be further reduced before the retentate, i.e. the purified polymeric organic base, is subjected to step (h). On the other hand, the purity of the inorganic halide salt may be further increased, before the filtrate, i.e. the purified inorganic halide salt, is used elsewhere:. filtrate (purified inorganic halide salt ) size based separation / precipitate - ► solution - - -x retentate (purified polymeric organic base)

[0138] Therefore, step (f) preferably involves alkaline processing, separation by precipitation and filtration, whereas step (g) involves dissolution of the precipitate and subsequent purification by a sizebased separation methodology. Preferably, in step (f) the inorganic halide salt is precipitated by means of a non-aqueous solvent and separated by solid-liquid separation such as filtration; whereas in step (g) the thus obtained precipitate is dissolved in an aqueous solvent, preferably water; and then purified by a size-based separation methodology, preferably selected from microfiltration, ultrafiltration and nanofiltration, more preferably by nanofiltration (step (g)).

[0139] Preferably,- the recovered polymeric organic base that is contained in the filtrate (supernatant) that contains the majority of the polymeric organic base in solution (see above step (f)) and / or- the recovered residual polymeric organic base that was separated along with the precipitate and subsequently subjected to a size-based separation methodology are subjected to step (h).

[0140] In further preferred embodiments, optional step (g) can be omitted because the organic base does not need to be purified.

[0141] Step (h):

[0142] In step (h) of the process according to the invention, the organic base composition or the purified organic base is recycled to the reaction mixture.

[0143] For the purpose of the specification, a "low melting organic halide salt" is an organic salt, preferably a non-polymeric salt, having a melting temperature of at most 120°C, preferably at most 115 °C, still more preferably at most 110°C, yet more preferably at most 105°C, even more preferably at most 100°C, and most preferably below 100°C.

[0144] For the purpose of the specification, an "ionic liquid" is defined as a compound completely composed of ions with melting point below 100°C.

[0145] For the purpose of the specification, "essentially containing no" means that practically nothing of a certain component is present, whereas it is contemplated that residual amounts of said certain component which might de detectable with sophisticated analytical methods but which have no influence on the overall process may be present.

[0146] For the purpose of the specification, "polymeric" refers to substances that are composed of repeating units, i.e. polymers.

[0147] For the purpose of the specification, "non-polymeric" refers to substances that are not composed of repeating units, i.e. that have comparatively low molecular weight.

[0148] For the purpose of the specification, the terms "halide" and "hydrohalogenic" refer to elements of group VII of the periodic table, e.g. "chloride", "hydrochloric" , "bromide", "hydrobromic" , "iodide", "hydroiodic" and the like, but additionally include pseudohalides such as "nitrile", "azide", "isocyanate" , "isothiocyanate" , and the like, as well as the corresponding hydropseudohalogenics. Preferably, throughout the description "halide" is used interchangeably with "chloride", and "hydrohalogenic" is used interchangeably with "hydrochloric" .

[0149] According to the present invention, it is proposed to alter the process so that instead of the phase transfer agent and inorganic base, an ionic liquid (IL) forming compound, preferably a non-polymeric organic base, e.g. alkyl imidazole, amine, hydroxy-amines, DABCO, DBU, DBN, TMEDA and the like, is used that can capture the cleaved halogen from, e.g., the 3,4-dichloro-l -butene (3,4-DBN) and 2,3,4- trichloro-1 -butene (TCB).

[0150] In preferred embodiments, when an ionic liquid (IL) forming compound is used as organic base, the formation of an ionic liquid (organic halide salt) in the process drives the equilibrium of the initial reaction and simplifies the generation of the (co-)monomers.

[0151] Exemplary amines are primary amines, primary hydroxyl amines, secondary amines, secondary hydroxyl amines, tertiary amines, or tertiary hydroxyl amines.

[0152] Preferred non-polymeric organic bases include but are not limited to di(Ci-i2-alkyl) or a tri(Ci. i2-alkyl)amines; more preferably a di(Ci-e-alkyl) or a tri(Ci-6-alkyl)amine; still more preferably di-(2- ethylhexyl)amine, triethylamine, tributylamine, or trioctylamine. Preferably, the amine is a primary diamine, a secondary diamine, or a tertiary diamine; preferably a tertiary diamine; more preferably (C1-4- alkyl)2N-(CH2)2-6-N(Ci-4-alkyl)2; still more preferably tetramethyl ethylene diamine (TMEDA).

[0153] Alternatively, it is proposed to alter the process so that instead of the phase transfer agent and inorganic base, a polymeric organic halide salt forming compound, preferably a polymeric organic base, e.g. polyethylene imine or the like, is used that can capture the cleaved halogen from, e.g., the 3,4- dichloro-1 -butene (3,4-DBN) and 2,3,4-trichloro-l -butene (TCB). Also in this regard, the polymeric organic base may be used in combination with a catalyst as described herein.

[0154] Preferred polymeric organic bases include but are not limited to polypropylene imines, polyvinyl amines, polyvinylpyrrolidones, polyacrylates, polyethylene imines, or the like. Preferably, the amine functionality is part of the polymeric backbone, more preferably as a secondary amine, or a tertiary amine.

[0155] Within all proposed processes, a regeneration of the formed organic halide salt (ionic liquid or polymeric organic halide salt) is necessary to recycle the organic base and to recover the cleaved halogen. The obtained base will be purified within a separate process step.

[0156] Dehydrochlorination (Reactor):

[0157] The reaction has an increased reactivity compared to the current dehydrochlorination and can be operated as batch-reaction, semi-batch-reaction and continuous reaction. Both dehydrochlorination (CP, DCB) processes can be conducted between -50°C and 300°C, and between 0 bara and 16 bara.

[0158] Based on experimental results, current installation, safety related aspects and due to economic reasons, it is preferred to operate the dehydrochlorination process of 2-chloro-l,3-butadiene (CP) production between 20°C and 100°C. A lower temperature means economical disadvantages (reaction has to be cooled by brine or other cooling agents), whereas higher temperatures had shown fast autopolymerization of 2-chloro-l,3-butadiene (CP) which can be excluded up to 80°C. Moreover, decomposition of 2-chloro-l,3-butadiene (CP) starts around 70°C thereby leading to impurities.

[0159] The preferred temperature of the dehydrochlorination of 2,3-dichloro-l,3-butadiene (DCB) is between 0°C and 10°C. This is related to the fact that the stabilizer for 2, 3-dichloro-l,3-butadiene (DCB) has high reactivity and needs to be oxidized during the reaction, whereas the flashpoint of 2,3-dichloro- 1,3-butadiene (DCB) is 13°C.

[0160] The reaction will preferably not be operated below 1 bara, to prevent oxygen leakages into the reactor. Since there is no need of high-pressure during reaction (liquid-liquid system), the max. operating pressure is preferably limited to 6 bara, to avoid high equipment costs.

[0161] The experiments had shown that the reaction can be facilitated by comprising a catalyst or adding hydrochloride. The catalyst needs to be inert within later regeneration of organic halide salt (ionic liquid or polymeric organic halide salt) to form the organic base.

[0162] The reaction of dehydrochlorination can be accelerated by operation at boiling conditions to separate, e.g., the produced 2-chloro-l,3-butadiene (CP) or 2,3-dichloro-l,3-butadiene (DCB) during reaction process (preferred). An operation without in-situ distillation is possible as well.

[0163] Separation:

[0164] The selection of the organic base is, among others, dependent on reaction kinetic of dehydrohalogenation. However, for the industrial process a liquid / liquid or gas / liquid phase separation is preferred, so the organic base and organic halide salt (ionic liquid or polymeric organic halide salt), respectively, are preferably selected considering also the physical and chemical parameter for phase separation (e.g. miscibility gap, aggregate state).

[0165] The biphasic system containing or essentially consisting of the desired halogenated 1,3-butadi- ene and organic halide salt (ionic liquid or polymeric organic halide salt) is preferably separated mechanically or thermally within a separation process (e.g. coalescing separation, centrifuging, decanting process, fdtration, distillation etc.). The separation process can be operated discontinuously and continuously. In general, the process can be operated between the above-mentioned process parameters for dehydrochlorination (T: - 50°C to 300°C; p: 0 bara to 16 bara).

[0166] The operating conditions for mechanical separation are dependent on miscibility gap, organic halide salt (ionic liquid or polymeric organic halide salt) (aggregate state), economic factors and for brown-field implementation, on infrastructure. For 2,3-dichloro-l,3-butadiene (DCB) / organic halide salt (ionic liquid or polymeric organic halide salt) separation a mechanical process is preferred, due to the high ability for auto-polymerization of the monomer and thermal degradation. This process will preferably be operated between -10°C and 20°C with pressures from preferably 0 bara to 6 bara.

[0167] A thermal separation process is preferred for 2-chloro-l,3-butadiene (CP) / ionic liquid. The boiling point for 2-chloro-l,3-butadiene (CP) at ambient pressure is approx. 64°C. Both processes, dehydrochlorination and separation of 2-chloro-l,3-butadiene (CP), can be conducted within one process step. This allows an economic heat management by using the reaction heat for 2-chloro-l,3-butadiene (CP) vaporization but limits the operating conditions for dehydrochlorination.

[0168] Thanks to targeted process conditions of separation and dehydrochlorination, fewer side products will be formed within the monomer phase. This leads to a high purity of monomers and therewith a high process efficiency of downstream polymerization.

[0169] Regeneration:

[0170] The formed organic halide salt (ionic liquid or polymeric organic halide salt) will be discontinuously or continuously either thermally or chemically regenerated by using specific process conditionsof preferably -50°C to 300°C, and preferably 0 bara to 16 bara. During the process, a halogenic byproduct will be obtained or chemically bound on another substance by decomposing the organic halide salt (ionic liquid or polymeric organic halide salt), forming the originally used organic base. To reduce the thermal stress of components and to facilitate the recovery process, an equipment with a high specific surface should be used. The base will be recycled by recirculation to dehydrochlorination process. The loss of organic base and corresponding organic halide salt (ionic liquid or polymeric organic halide salt) due to thermal and chemical degradation as well as physical losses will be compensated.

[0171] The regeneration efficiency / conditions are dependent on the strength of the organic base and this has an effect on the reaction kinetics of the dehydrochlorination. The desired operational temperature is preferably set to 20°C to 160°C for economic reasons. The operational pressure is preferably between 0 bara to 16 bara.

[0172] Depending upon the nature of the organic base and the corresponding organic halide salt (ionic liquid or polymeric organic halide salt) and the reaction conditions, either a monophasic or a biphasic system is obtained.

[0173] Preferred embodiments of the invention are schematically illustrated in Figures 1 to 3. Figure 1 shows a process flow diagram with in-situ distillation of produced monomer. A single phase is obtained after dehydrohalogenation. Figure 2 shows a process flow diagram with in situ distillation of produced monomer. Two-phases are obtained after dehydrohalogenation. Figure 3 shows a process flow diagram with separation of produced monomer by phase separation.

[0174] Figure 1 schematically illustrates a preferred embodiment of a process obtaining a monophasic system. Halogenated 1 -butene, organic base and optionally catalyst (10) are supplied into a dehydrohalogenation reactor (1) (step (a)). The reaction in step (b) is preferably performed in two stages, namely in dehydrohalogenation reactor (1) and subsequently and optionally in a residence time reactor (3) arranged downstream of the dehydrohalogenation reactor (1). Halogenated 1,3 -butadiene (11) obtained in the dehydrohalogenation reactor (1) is preferably distilled off in situ from the monophasic reaction mixture (step (c)). The remaining residual halogenated 1-butene, halogenated 1,3-butadiene, organic halide salt (ionic liquid or polymeric organic halide salt), and residual organic base (12) are then preferably supplied into the residence time reactor (3) for further reaction in step (b). Halogenated 1,3-butadiene (13) obtained in the residence time reactor (3) is preferably also distilled off in situ from the monophasic reaction mixture in order to shift the equilibrium and to achieve high conversion (product composition of step (d)). The distilled halogenated 1,3 -butadienes (11) and (13) are preferably combined with one another and purified in rectification unit (2) (step (e)) to provide purified halogenated 1,3-butadiene (19). The organic halide salt composition containing organic halide salt (ionic liquid or polymeric organic halide salt), and residual organic base (14) is preferably supplied to regeneration unit (4).

[0175] When the organic halide salt composition containing organic halide salt contains ionic liquid, it is preferably heated to release and separate hydrohalogenic acid (16) from the organic halide salt (hy- drohalogenic acid composition of step (f)). The remaining organic base (15) (organic base composition of step (f)) is preferably supplied to base purification unit (5) where it is preferably separated from high boiling components (17), preferably by rectification.

[0176] When the organic halide salt composition containing organic halide salt contains polymeric organic halide salt, it is preferably reconverted into polymeric organic base and an inorganic halide salt by alkaline processing with an inorganic base that is a stronger base than the polymeric organic base, preferably sodium hydroxide or potassium hydroxide. The inorganic halide salt is preferably separated from the polymeric organic base by a size-based separation methodology, preferably by filtration, more preferably selected from microfiltration, ultrafiltration and nanofiltration, still more preferably by nan- ofiltration.

[0177] In a preferred embodiment, the purification unit (5) is operated discontinuously. The thus purified organic base (18) is preferably recycled to the dehydrohalogenation reactor (1) (step (a)).

[0178] Figures 2 and 3 schematically illustrate preferred embodiments of a process obtaining a biphasic system. The process of Figure 2 involves separation of halogenated 1,3-butadiene by in-situ distillation, the process of Figure 3 involves separation of halogenated 1,3-butadiene by phase separation. Laboratory tests for dehydrohalogenation have shown that an in situ distillation is preferred to increase the conversion (Figure 2). For a biphasic system, the reaction is preferably performed in a single stage.

[0179] According to the embodiment of Figure 2, halogenated 1,3-butadiene (11) obtained in the dehydrohalogenation reactor (1) is preferably distilled off in situ from the monophasic reaction mixture step (c)). In another preferred embodiment, the reaction mixture in step c) is biphasic. The remaining residual halogenated 1-butene, halogenated 1,3-butadiene, organic halide salt (ionic liquid or polymeric organic halide salt), and residual organic base (12) are then preferably supplied into phase separation unit (3a) where they are separated into a product composition containing halogenated 1,3-butadiene and residual halogenated 1-butene (13a) and an organic halide salt composition containing organic halide salt (ionic liquid or polymeric organic halide salt), and residual organic base (14). The product composition (13a) is preferably recycled to the dehydrohalogenation reactor (1). The remaining preferred steps correspond to those illustrated for the embodiment of Figure 1.

[0180] According to the embodiment of Figure 3, the total amount of the halogenated 1,3-butadiene is contained in the product composition containing halogenated 1,3-butadiene and residual halogenated 1- butene (13a), because no in-situ distillation is performed. After phase separation, the product composition (13a) is purified in rectification unit (2) (step (e)) to provide purified halogenated 1,3-butadiene (19). Residual halogenated 1-butene (20) is preferably recycled to the dehydrohalogenation reactor (1). The remaining preferred steps correspond to those illustrated for the embodiments of Figures 1 and 2.

[0181] Particularly preferred embodiments of the invention are compiled as Clauses hereinafter:23-1Clause 1 : A process for the preparation of a halogenated 1,3 -butadiene of general formula (I)whereinR means -H or Hal; andHal independently means -Cl, -Br or -I; preferably -Cl; said process comprising the steps of:(a) providing a reaction mixture containing or essentially consisting of- a halogenated 1 -butene of general formula (II)whereinR means -H or Hal; andHal independently means -Cl, -Br or -I; preferably -Cl;- an organic base; and- optionally a catalyst;(b) eliminating hydrohalogenic acid from the halogenated 1 -butene to produce the halogenated 1,3- butadiene; and forming an organic halide salt of the eliminated hydrohalogenic acid with the organic base;(c) optionally, separating at least a portion of the halogenated 1,3 -butadiene from the reaction mixture by in-situ distillation;(d) separating the reaction mixture into- a product composition containing halogenated 1,3 -butadiene and optionally residual halogenated 1 -butene; and- an organic halide salt composition containing organic halide salt of the eliminated hydrohalogenic acid with organic base and optionally residual organic base;(e) optionally, purifying the halogenated 1,3 -butadiene that is contained in the product composition; optionally together with the portion of the halogenated 1,3 -butadiene optionally separated in step (c);(f) cleaving the organic halide salt that is contained in the organic halide salt composition to release hydrohalogenic acid from the organic halide salt, and separating the organic halide salt composition intoINCORPORATED BY REFERENCE (RULE 20.6)Clause 1: A process for the preparation of a halogenated 1,3 -butadiene of general formula (I)whereinR means -H or Hal; andHal independently means -Cl, -Br or -I; preferably -Cl; said process comprising the steps of:(a) providing a reaction mixture containing or essentially consisting of- a halogenated 1 -butene of general formula (II)R means -H or Hal; andHal independently means -Cl, -Br or -I; preferably -Cl;- an organic base; and- optionally a catalyst;(b) eliminating hydrohalogenic acid from the halogenated 1 -butene to produce the halogenated 1,3- butadiene; and forming an organic halide salt of the eliminated hydrohalogenic acid with the organic base;(c) optionally, separating at least a portion of the halogenated 1,3 -butadiene from the reaction mixture by in-situ distillation;(d) separating the reaction mixture into- a product composition containing halogenated 1,3 -butadiene and optionally residual halogenated 1 -butene; and- an organic halide salt composition containing organic halide salt of the eliminated hydrohalogenic acid with organic base and optionally residual organic base;(e) optionally, purifying the halogenated 1,3 -butadiene that is contained in the product composition; optionally together with the portion of the halogenated 1,3-butadiene optionally separated in step (c);(f) cleaving the organic halide salt that is contained in the organic halide salt composition to release hydrohalogenic acid from the organic halide salt, and separating the organic halide salt composition intoERRONEOUSLY FILED (RULE 20.5bis)- a hydrohalogenic acid composition containing released hydrohalogenic acid, or an inorganic halide salt composition containing an inorganic halide salt; and- an organic base composition containing organic base;(g) optionally, purifying the organic base that is contained in the organic base composition thereby obtaining purified organic base; and(h) recycling the organic base composition or the purified organic base to the reaction mixture.Clause 2: The process according to clause 1, wherein the halogenated 1-buten is 3,4-dichloro-l -butene (3,4-DBN) and the halogenated 1,3-butadiene is 2-chloro-l,3-butadiene (CP):,Clause 3: The process according to clause 1, wherein the halogenated 1-buten is 2,3,4-trichloro-l -butene(TCB) and the halogenated 1,3-butadiene is 2,3-dichloro-l,3-butadiene (DCB):Clause 4: The process according to any of the preceding clauses, wherein the reaction mixture has a water content of not more than 60 wt.-%, preferably not more than 50 wt.-%, more preferably not more than 40 wt.-%, still more preferably not more than 30 wt.-%, yet more preferably not more than 20 wt.- %, even more preferably not more than 10 wt.-%, in each case relative to the total weight of the reaction mixture.Clause 5 : The process according to any of the preceding clauses, wherein the reaction mixture has a water content of not more than 8 wt.-%, preferably not more than 7 wt.-%, more preferably not more than 6 wt.-%, still more preferably not more than 5 wt.-%, yet more preferably not more than 4 wt.-%, even more preferably not more than 3 wt.-%, most preferably not more than 2 wt.-%, and in particular not more than 1 wt.-%, in each case relative to the total weight of the reaction mixture, or is essentially free of water; preferably the total process is performed essentially in the absence of water.Clause 6: The process according to any of the preceding clauses, wherein the reaction mixture has a solvent content of not more than 8 wt.-%, preferably not more than 7 wt.-%, more preferably not more than 6 wt.-%, still more preferably not more than 5 wt.-%, yet more preferably not more than 4 wt.-%, even more preferably not more than 3 wt.-%, most preferably not more than 2 wt.-%, and in particular not more than 1 wt.-%, in each case relative to the total weight of the reaction mixture, or is essentiallyfree of solvent; preferably wherein the total process is performed essentially in the absence of solvent; preferably wherein the total process is performed essentially in the absence of solvent.Clause 7 : The process according to any of the preceding clauses, wherein the conjugate acid of the organic base has an aqueous PKA value at 25 °C of at least 7.0, preferably at least 7.5, more preferably at least 8.0, still more preferably at least 8.5, yet more preferably at least 9.0, even more preferably at least 9.5, most preferably at least 10.0, and in particular at least 10.5.Clause 8: The process according to any of the preceding clauses, wherein the conjugate acid of the organic base has an aqueous PKA value at 25°C of (i) at most 14.0, preferably at most 13.5, more preferably at most 13.0, still more preferably at most 12.5, yet more preferably at most 12.0, even more preferably at most 11.5, most preferably at most 11.0, and in particular at most 10.5; or (ii) at most 12.4, preferably at most 12.2, more preferably at most 12.0, still more preferably at most 11.8, yet more preferably at most 11.6, even more preferably at most 11.4, most preferably at most 11.2, and in particular at most 11.0.Clause 9: The process according to any of the preceding clauses, wherein the organic base is non-poly- meric.Clause 10: The process according to any of the preceding clauses, wherein the organic base is an amine or hydroxylamine; preferably a primary amine, a primary hydroxyl amine, a secondary amine, a secondary hydroxyl amine, a tertiary amine, or a tertiary hydroxyl amine; preferably a di(Ci _i 2-alkyl) or a tri(Ci-i2-alkyl)amine; more preferably a di(Ci-6-alkyl) or a tri(Ci-6-alkyl)amine; still more preferably di- (2-ethylhexyl)amine, triethylamine, tributylamine, or trioctylamine.Clause 11 : The process according to any of the preceding clauses, wherein the organic base is a primary diamine, a secondary diamine, or a tertiary diamine; preferably a tertiary diamine; more preferably (Ci- 4-alkyl)2N-(CH2)2-6-N(Ci-4-alkyl)2; still more preferably tetramethyl ethylene diamine (TMEDA).Clause 12: The process according to any of the preceding clauses, wherein the organic base is a heteroaromatic compound; preferably an imidazole; more preferably an alkyl imidazole; still more preferably l-(Ci-6-alkyl)-imidazole; yet more preferably 1-methyl imidazole or 1-butyl imidazole.Clause 13: The process according to any of the preceding clauses, wherein the organic base is a bicyclic compound; preferably a diazabicyclic compound; more preferably l,8-diazabicyclo[5.4.0]undec-7-en (DBU), l,5-diazabicyclo[4.3.0]non-5-en (DBN), (1,4-diazabicyclo [2.2.2]octane (DABCO), or the like.Clause 14: The process according to any of the clauses 1 to 8, wherein the organic base is polymeric; preferably selected from the group consisting of polypropylene imines, polyvinyl amines, polyvinylpyrrolidones, polyacrylates, and polyethylene imines; more preferably from polyethylene imines.Clause 15: The process according to any of the preceding clauses, wherein the catalyst is selected from (i) trialkyl phosphonium salts; preferably tributyl phosphonium salts; more preferably tributyl phosphonium hydrochlorides; (ii) tetraalkyl phosphonium salts; preferably tetrabutyl phosphonium salts; morepreferably tetrabutyl phosphonium chloride; (iii) ammonium salts; and (iv) tetraalkyl ammonium salts; preferably tetrabutyl ammonium salts; more preferably tetrabutyl ammonium chloride.Clause 16: The process according to any of the preceding clauses, wherein the catalyst forms in situ between the base and hydrohalogenic acid that is eliminated in step (b) (autocatalysis).Clause 17 : The process according to any of the preceding clauses, wherein the reaction mixture provided in step (a) is monophasic.Clause 18: The process according to any of clauses 1 to 16, wherein the reaction mixture provided in step (a) is biphasic having a first phase and a second phase.Clause 19: The process according to clause 18, wherein - the majority of the halogenated 1-butene is contained in the first phase, and - the majority of the organic base is contained in the second phase.Clause 20: The process according to any of the preceding clauses, wherein the reaction mixture obtained in step (b) is monophasic.Clause 21: The process according to any of clauses 1 to 19, wherein the reaction mixture obtained in step (b) is biphasic having a first phase and a second phase.Clause 22: The process according to any of clauses 1 to 19, wherein the reaction mixture obtained in step (b) is triphasic having a first phase, a second phase, and a third phase.Clause 23: The process according to clause 21 or 22, wherein - the majority of the halogenated 1,3- butadiene and optionally the majority of residual halogenated 1-butene is contained in the first phase, and - the majority of the organic halide salt and optionally the majority of residual organic base is contained in the second phase.Clause 24: The process according to any of the preceding clauses, wherein step (b) is operated as batchreaction, semi-batch-reaction and continuous reaction.Clause 25: The process according to any of the preceding clauses, wherein step (b) is performed under boiling conditions.Clause 26: The process according to any of the preceding clauses, wherein step (b) is performed at a temperature within the range of from -50 to 300°C.Clause 27 : The process according to clause 26, wherein step (b) is performed at a temperature within the range of from 20 to 100°C, preferably 20 to 90°C, more preferably 20 to 80°C, still more preferably 20 to 70°C; preferably wherein the halogenated 1-buten is 3,4-dichloro- 1-butene (3,4-DBN) and the halogenated 1,3-butadiene is 2-chloro-l,3-butadiene (CP).Clause 28: The process according to clause 26, wherein step (b) is performed at a temperature within the range of from -30 to 10°C, preferably -20 to 10°C, more preferably -10 to 10°C, still more preferably0 to 10°C; preferably wherein the halogenated 1-buten is 2,3,4-trichloro-l-butene (TCB) and the halogenated 1,3-butadiene is 2,3-dichloro-l,3-butadiene (DCB).Clause 29: The process according to any of the preceding clauses, wherein step (b) is performed at a pressure within the range of from 0 to 16 bara; preferably 1 to 6 bara.Clause 30: The process according to any of the preceding clauses, wherein step (b) is performed in a dehydrohalogenation reactor and in a residence time reactor which is arranged downstream of the dehydrohalogenation reactor.Clause 31 : The process according to any of the preceding clauses, wherein the reaction mixture obtained in step (b) is monophasic and in step (c) at least a portion of the halogenated 1,3-butadiene is separated from the reaction mixture by in-situ distillation.Clause 32: The process according to any of clauses 1 to 30, wherein the reaction mixture obtained in step (b) is biphasic and in step (c) at least a portion of the halogenated 1,3-butadiene is separated from the reaction mixture by in-situ distillation.Clause 33: The process according to any of the preceding clauses, wherein the reaction mixture obtained in step (b) is monophasic and in step (d) the product composition is separated from the organic halide salt composition by gas / liquid phase separation, preferably in-situ distillation; preferably wherein the halogenated 1-buten is 3,4-dichloro-l -butene (3,4-DBN) and the halogenated 1,3-butadiene is 2-chloro- 1,3-butadiene (CP).Clause 34: The process according to any of the preceding clauses, wherein the reaction mixture obtained in step (b) is biphasic and in step (d) the product composition is separated from the organic halide salt composition by liquid / liquid phase separation or solid / liquid phase separation.Clause 35: The process according to clause 34, wherein phase separation involves coalescing separation, centrifuging, decanting, fdtration, or any combination thereof.Clause 36: The process according to any of the preceding clauses, wherein step (d) is operated as batchreaction, semi-batch-reaction and continuous reaction.Clause 37: The process according to any of the preceding clauses, wherein in step (d) the product composition is recycled to the reaction mixture.Clause 38: The process according to any of the preceding clauses, wherein step (d) is performed at a temperature within the range of from -50 to 300°C.Clause 39: The process according to clause 35, wherein step (d) is performed at a temperature within the range of from -40 to 20°C, preferably -30 to 20°C, more preferably -20 to 20°C, still more preferably -10 to 20°C; preferably wherein the halogenated 1-buten is 2,3,4-trichloro-l-butene (TCB) and the halogenated 1,3-butadiene is 2,3-dichloro-l,3-butadiene (DCB).Clause 40: The process according to any of the preceding clauses, wherein step (d) is performed at a pressure within the range of from 0 to 16 bara; preferably 1 to 6 bara.Clause 41: The process according to any of the preceding clauses, wherein in step (e) residual halogenated 1 -butene is recycled to the reaction mixture.Clause 42: The process according to any of the preceding clauses, wherein step (f) is operated as batchreaction, semi-batch-reaction and continuous reaction.Clause 43 : The process according to any of the preceding clauses, wherein step (f) is performed at a temperature within the range of from -50 to 300°C, preferably 0 to 300°C, more preferably 70 to 300°C.Clause 44: The process according to clause 43, wherein the organic base is an amine or hydroxyl amine and wherein step (f) is performed at a temperature that is above the melting temperature of the base under the given conditions.Clause 45: The process according to clause 43, wherein the organic base is an imidazole and wherein step (f) is performed at a temperature that is above the melting temperature of the base under the given conditions.Clause 46: The process according to any of the preceding clauses, wherein step (f) is performed at a pressure within the range of from 0 to 16 bara; preferably 0.1 to 6 bara.Clause 47 : The process according to any of the preceding clauses, wherein the organic halide salt is a polymeric organic halide salt and in step (f) the polymeric organic halide salt is reconverted into polymeric organic base and an inorganic halide salt.Clause 48: The process according to clause 47, wherein the polymeric organic halide salt is reconverted into polymeric organic base and an inorganic halide salt by alkaline processing with an inorganic base that is a stronger base than the polymeric organic base, preferably sodium hydroxide or potassium hydroxide.Clause 49: The process according to clause 47 or 48, wherein the inorganic halide salt is separated from the polymeric organic base by a size-based separation methodology, preferably by fdtration, more preferably selected from microfdtration, ultrafdtration and nanofiltration, still more preferably by nanofil- tration.Clause 50: The process according to any of clauses 47 to 49, wherein the inorganic halide salt is separated from the polymeric organic base by precipitation; the thus obtained precipitate is dissolved in water; and residual polymeric organic base that is contained in the thus obtained solution is purified by a size-based separation methodology, preferably by filtration, more preferably selected from microfiltration, ultrafiltration and nanofiltration, still more preferably by nanofiltration.Clause 51 : The process according to any of the preceding clauses, wherein in step (g) the organic base that is contained in the organic base composition is purified by rectification.

[0182] The following examples further illustrate the invention but are not to be construed as limiting its scope:Example 1 - dehydrochlorination of 3,4-dichloro-l -butene to afford 2-chloro-l,3-butadiene:

[0183] The following experiments were conducted with 3,4-dichloro-l -butene (3,4-DBN):Oct3: trioctylamine; TMEDA: tetramethyl ethylene diamine; NEt3: triethylamine; NBut3: tributylamine; Di-2-EHA: di-(2-ethylhexl)amine; DBU: l,8-diazabicyclo[5.4.0]undec-7-en; Melm: 1-methyl imidazole; Bulm: 1-butyl imidazole; Bu4PCl: tetrabutyl phosphonium chloride.#: Very strong reaction without any analysis due to solids

[0184] Figure 4 shows the reaction kinetics of Example 1-27, which was conducted at 60°C without distillation.

[0185] The product of Example 1-11 (Figure 5) was analyzed by gas chromatography showing the peak of 2-chloro-l,3-butadiene (CP), 3,4-dichloro-l -butene (3,4-DBN) and triethylamine (NEt3) as well as the external standard. Two small peaks indicate the impurities that may result from raw material or reaction.

[0186] With respect to Examples 1-22, the distillate was analyzed without finding residual organic base methylimidazole (Melm).

[0187] Examples 1-7 and 1-8 (3,4-DBN) demonstrate that in specific cases adding hydrochloric acid has the same effect as a catalyst.

[0188] Examples 1-19 and 1-20 show a strong reactivity when employing strong organic bases (DBU). However, when using such strong organic bases, regeneration of ionic liquids will be difficult because hydrohalogenic acid will not be easily released upon heating. With respect to Example 1-19 specifically, no analysis was performed due to solids.

[0189] Examples 1-29 & 1-30 (Figure 6) and 1-35 & 1-37 (Figure 7) shows a strong reactivity increase by comprising a catalyst on the reaction. The same effect has been proven by comprising Melm as base (1-21 & 1-34). The final conversion (Melm) doesn’t increase while using a catalyst.

[0190] Examples 1-29 & 1-31 and 1-35 & 1-36 shows that an increase in base to DBN ratio leads to higher reactivity when comprising Bulm (Figure 6) or Di-2-EHA (Figure 7) whereas this shows no effect when comprising Melm 1-21 & 1-33.

[0191] Examples 1-29 & 1-32 (Figure 6) and 1-36 & 1-38 (Figure 7) shows that the temperature is important for reactivity.Example 2 - dehydrochlorination of 2,3,4-trichloro-l-butene to afford 3,4-dichloro-l -butene:

[0192] The following experiments were conducted with 2,3,4-trichloro-l-butene (TCB):NEt3: triethylamine; NBut3: tributylamine; Melm: 1-methyl imidazole; Bu4PCl: tetrabutyl phosphonium chloride

[0193] Figure 8 shows the development of conversion in percent over time in minutes with respect to dehydrochlorination of 2,3,4-trichloro-l-butene (TCB) for Example 2-5.

[0194] Example 2-1, 2-2 & 2-3 (Figure 9) show a reactivity increase by comprising a catalyst on the reaction.

[0195] According to the extensive experiments related to dehydrochlorination providing 2-chloro-l,3- butadiene (CP) and 2,3-dichloro-l,3-butadiene (DCB), different organic bases have different utility in the two processes. There is indication that the 2-chloro-l,3-butadiene (CP) synthesis delivers advantages by comprising amines as organic base. Other organic bases can be used as well.

[0196] Summing up, the in-situ distillation seems to have advantages for many bases (e.g. methylimidazole). For bases like tributylamine and triethylamine, a multistage distillation (rectification process) would be preferred.Example 3 - dehydrochlorination of 3,4-dichloro-l -butene to afford 2-chloro-l,3-butadiene:

[0197] The following experiments were conducted with 3,4-dichloro-l -butene (3,4-DBN) and polyethylene imine (PEI) solution as organic base:A: Aliquat 336; D: Dodecane

[0198] Reaction time was 30 minutes for each experiment.

[0199] Experiments revealed that a high space time yield can be achieved. No additional phase transfer catalyst is needed because polyethylene imine has the same effect. A high molecular weight of polyethylene imine leads to gelation. A high water content affects the yield negatively. Partial gelation takes place also in presence of a high amount of water. A high amount of phenothiazine (PTZ) suppresses polymerization significantly. Stripping gas facilitates distillation of 2-chloro-l,3-butadiene (CP) and suppresses polymerization reaction. Reaction with partially hydrohalogenated polyethylene imine is possible. Co-solvents such as dodecane and trioctylamine (TOA) do not improve reaction. Low temperatures of 80°C help to reduce polymerization reaction, whereas reactivity is still sufficient. NMR shows no impurities, e.g. alkylation or isomerization products. Separation of 3,4-dichloro-l -butene and 2- chloro-l,3-butadiene (CP) can be improved in distillation process.

[0200] Reference numerals:dehydrohalogenation reactor 13 halogenated 1,3 -butadiene rectification unit 13a halogenated 1, 3 -butadiene + residual educt residence time reactor 14 organic halide salt (ionic liquid or polya phase separation unit meric organic halide salt) + residual orregeneration unit ganic base base purification unit 15 organic base 0 halogenated 1 -butene + organic base 16 hydrohalogenic acid or inorganic halide1 halogenated 1,3 -butadiene salt 2 residual halogenated 1 -butene + halogen17 high boiling components ated 1,3 -butadiene + organic halide salt 18 organic base (ionic liquid or polymeric organic halide 19 halogenated 1,3 -butadiene salt) + residual organic base 20 residual halogenated 1 -butene

Claims

Patent claims:

1. A process for the preparation of a halogenated 1,3 -butadiene of general formula (I)whereinR means -H or Hal; andHal independently means -Cl, -Br or -I; preferably -Cl; said process comprising the steps of:(a) providing a reaction mixture containing or essentially consisting of- a halogenated 1 -butene of general formula (II)Hal - v R di) Hal wherein R means -H or Hal; andHal independently means -Cl, -Br or -I; preferably -Cl;- an organic base; and- optionally a catalyst;(b) eliminating hydrohalogenic acid from the halogenated 1 -butene to produce the halogenated 1,3 -butadiene; and forming an organic halide salt of the eliminated hydrohalogenic acid with the organic base;(c) optionally, separating at least a portion of the halogenated 1,3 -butadiene from the reaction mixture by in-situ distillation;(d) separating the reaction mixture into- a product composition containing halogenated 1,3-butadiene and optionally residual halogenated 1 -butene; and- an organic halide salt composition containing organic halide salt of the eliminated hydrohalogenic acid with organic base and optionally residual organic base;(e) optionally, purifying the halogenated 1,3-butadiene that is contained in the product composition; optionally together with the portion of the halogenated 1,3-butadiene optionally separated in step (c);INCORPORATED BY REFERENCE (RULE 20.6)Patent claims:

1. A process for the preparation of a halogenated 1,3-butadiene of general formula (I)whereinR means -H or Hal; andHal independently means -Cl, -Br or -I; preferably -Cl; said process comprising the steps of:(a) providing a reaction mixture containing or essentially consisting of- a halogenated 1 -butene of general formula (II)whereinR means -H or Hal; andHal independently means -Cl, -Br or -I; preferably -Cl;- an organic base; and- optionally a catalyst;(b) eliminating hydrohalogenic acid from the halogenated 1 -butene to produce the halogenated 1,3-butadiene; and forming an organic halide salt of the eliminated hydrohalogenic acid with the organic base;(c) optionally, separating at least a portion of the halogenated 1,3-butadiene from the reaction mixture by in-situ distillation;(d) separating the reaction mixture into- a product composition containing halogenated 1,3-butadiene and optionally residual halogenated 1 -butene; and- an organic halide salt composition containing organic halide salt of the eliminated hydrohalogenic acid with organic base and optionally residual organic base;(e) optionally, purifying the halogenated 1,3-butadiene that is contained in the product composition; optionally together with the portion of the halogenated 1,3-butadiene optionally separated in step (c);ERRONEOUSLY FILED (RULE 20.5bis)(f) cleaving the organic halide salt that is contained in the organic halide salt composition to release hydrohalogenic acid from the organic halide salt, and separating the organic halide salt composition into- a hydrohalogenic acid composition containing released hydrohalogenic acid, or an inorganic halide salt composition containing an inorganic halide salt; and- an organic base composition containing organic base;(g) optionally, purifying the organic base that is contained in the organic base composition thereby obtaining purified organic base; and(h) recycling the organic base composition or the purified organic base to the reaction mixture; and.

2. The process according to claim 1, wherein the halogenated 1-buten is 3,4-dichloro-l -butene (3,4- DBN) and the halogenated 1,3 -butadiene is 2 -chloro- 1,3 -butadiene (CP):3,4-DBN CP3. The process according to claim 1, wherein the halogenated 1-buten is 2,3,4-trichloro-l -butene (TCB) and the halogenated 1,3-butadiene is 2,3-dichloro-l,3-butadiene (DCB):

4. The process according to any of the preceding claims, wherein the organic base is non-polymeric.

5. The process according to any of the preceding claims, wherein the organic base is an amine or hydroxylamine; preferably a primary amine, a primary hydroxyl amine, a secondary amine, a secondary hydroxyl amine, a tertiary amine, or a tertiary hydroxyl amine; preferably a di(Ci-i2- alkyl) or a tri(Ci-i2-alkyl)amine; more preferably a di(Ci-6-alkyl) or a tri(Ci-6-alkyl)amine; still more preferably di-(2-ethylhexyl)amine, triethylamine, tributylamine, or trioctylamine.

6. The process according to any of the preceding claims, wherein the organic base is a primary diamine, a secondary diamine, or a tertiary diamine; preferably a tertiary diamine; more preferably (Ci-4-alkyl)2N-(CH2)2-6-N(Ci-4-alkyl)2; still more preferably tetramethyl ethylene diamine (TMEDA).

7. The process according to any of the preceding claims, wherein the organic base is a heteroaromatic compound; preferably an imidazole; more preferably an alkyl imidazole; still more preferably l-(Ci-6-alkyl)-imidazole; yet more preferably 1-methyl imidazole or 1-butyl imidazole.

8. The process according to any of the preceding claims, wherein the organic base is a bicyclic compound; preferably a diazabicyclic compound; more preferably l,8-diazabicyclo[5.4.0]undec-7-en (DBU), l,5-diazabicyclo[4.3.0]non-5-en (DBN), (1,4-diazabicyclo [2.2.2]octane (DABCO), or the like.

9. The process according to any of the claims 1 to 3, wherein the organic base is polymeric; preferably selected from the group consisting of polypropylene imines, polyvinyl amines, polyvinylpyrrolidones, polyacrylates, and polyethylene imines; more preferably from polyethylene imines.

10. The process according to any of the preceding claims, wherein the catalyst is selected from (i) trialkyl phosphonium salts; preferably tributyl phosphonium salts; more preferably tributyl phosphonium hydrochlorides; (ii) tetraalkyl phosphonium salts; preferably tetrabutyl phosphonium salts; more preferably tetrabutyl phosphonium chloride; (iii) ammonium salts; and (iv) tetraalkyl ammonium salts; preferably tetrabutyl ammonium salts; more preferably tetrabutyl ammonium chloride.

11. The process according to any of the preceding claims, wherein the catalyst forms in situ between the base and hydrohalogenic acid that is eliminated in step (b) (autocatalysis).

12. The process according to any of the preceding claims, wherein step (b) is performed under boiling conditions.

13. The process according to any of the preceding claims, wherein step (b) is performed in a dehydrohalogenation reactor and in a residence time reactor which is arranged downstream of the dehydrohalogenation reactor.

14. The process according to any of the preceding claims, wherein the organic halide salt is a polymeric organic halide salt and in step (f) the polymeric organic halide salt is reconverted into polymeric organic base and an inorganic halide salt.

15. The process according to any of the preceding claims, wherein in step (g) the organic base that is contained in the organic base composition is purified by rectification.

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