PROCESS FOR THE PREPARATION OF 2-OCTYL(METH)ACRYLATE

Description

[0001] The present invention relates to a process for the preparation of 2-octyl (meth)acrylate by reacting 2-octanol with (meth)acrylic acid in the presence of an acidic esterification catalyst, a polymerization inhibitor and the entraining agent cyclohexane.

[0002] In this document, the term (meth)acrylic acid is an abbreviation for methacrylic acid and / or acrylic acid. Similarly, 2-octyl (meth)acrylate refers to 2-octyl acrylate and / or 2-octyl methacrylate.

[0003] 2-Octyl (meth)acrylate is a monomer that can be used as a homo- and comonomer in radical, cationic, and anionic polymerizations, as well as complex-catalyzed polymerizations. It is suitable for use in emulsion polymerizations, solvent-based polymerizations, and bulk polymerizations.

[0004] Important applications include decorative coatings or technical coatings for the industrial sector as well as adhesives, sealants, paper chemicals such as binders and sizing agents, leather and textile chemicals such as binders and hydrophobizing agents, rheology additives, impact modifiers for plastics, pour point depressants for oil and lubricants, printing inks or reactive thinners for UV-curing resins and systems.

[0005] Known processes for the large-scale production of 2-octyl (meth)acrylate are predominantly based on the transesterification reaction between a (meth)acrylate of a lower alcohol and 2-octanol in the presence of an alkyl titanate as a transesterification catalyst and at least one polymerization inhibitor. Such a process is disclosed in WO 2013 / 110877 A1 (Arkema France). A disadvantage of the transesterification processes is the formation of an azeotrope of the alcohol of the low-boiling (meth)acrylate and the low-boiling (meth)acrylate, for example, but not limited to, methanol / methyl methacrylate or ethanol / ethyl acrylate, which requires complex processing or disposal.

[0006] A process for the direct esterification of 2-octyl acrylate is disclosed in WO 2013 / 064775 A1 (Arkema France). The desired product 2-octyl acrylate is obtained by the direct esterification of acrylic acid with 2-octanol in the presence of a catalyst and a polymerization inhibitor. The esterification water formed during the esterification forms a heterogeneous azeotrope with the 2-octanol and is separated by distillation in a distillation column mounted on the reactor. The reactor is equipped with a stirrer and an external heat exchanger. In a downstream purification step, at least some of the catalyst is recycled to the reactor, and the desired product 2-octyl acrylate is separated.

[0007] Another process for the direct esterification of 2-octyl acrylate is disclosed in WO 2008 / 046000 A1 (3M Innovative Properties Company, USA). The desired product 2-octyl acrylate is obtained by the direct esterification of acrylic acid with 2-octanol in the presence of the catalyst p-toluenesulfonic acid, the polymerization inhibitor phenothiazine, and the entraining agent toluene. The esterification water formed during the esterification forms a heterogeneous azeotrope with the entraining agent toluene. This heterogeneous azeotrope is separated by distillation in a "Dean Stark" distillation column mounted on the reactor.

[0008] These two processes for the direct esterification of 2-octyl acrylate described above have the particular disadvantage of requiring high energy consumption because the esterification water produced during the esterification must be removed from the reactor by evaporation in order to separate the evaporated esterification water in a distillation column attached to the reactor. Thus, the high boiling point of water or the high boiling point of the heterogeneous azeotrope "esterification water with toluene and / or esterification water with excess 2-octanol" in the bottom of the reactor (1) must not only be reached but even exceeded in order to achieve the required boiling point at the top of the distillation column.

[0009] The objective was therefore to provide a process for the production of 2-octyl (meth)acrylate that can be operated with lower energy consumption, at a lower reactor bottom temperature, and at moderate pressures, such as atmospheric pressure, without the need for complex equipment. Furthermore, the process should achieve a better space-time yield than the known processes from the above-cited prior art with the same energy input.

[0010] This object is achieved according to the present invention by a process for preparing 2-octyl (meth)acrylate according to claim 1. Advantageous embodiments of the process are recited in claims 2 to 15.

[0011] The process according to the invention for the preparation of 2-octyl (meth)acrylate by reacting 2-octanol with (meth)acrylic acid in the presence of an acidic esterification catalyst, a polymerization inhibitor and the entraining agent cyclohexane comprises the steps: Providing a reactor unit (24), wherein a reactor (1) with a reactor heating element (30) is located within the reactor unit (24), feeding 2-octanol, (meth)acrylic acid, acidic esterification catalyst, cyclohexane and polymerization inhibitor into the one reactor (1), carrying out an esterification in the one reactor (1) to form a liquid reaction mixture, wherein the esterification in the one reactor (1) takes place at a bottom temperature in the range from 90 to 130 °C and at an absolute pressure in the range from 0.5 to 2.0 bar, and a resulting reaction output is obtained from the one reactor (1), wherein the resulting reaction output contains at least 2-octyl (meth)acrylate, 2-octanol, (meth)acrylic acid, acidic esterification catalyst, cyclohexane, esterification water and polymerization inhibitor, and the esterification water formed during the esterification together with the Entrainer cyclohexane forms a heterogeneous azeotrope,Evaporating the heterogeneous azeotrope from the liquid reaction mixture of one reactor (1), wherein the evaporation is achieved by the one reactor heating element (30), and separating the gaseous heterogeneous azeotrope from the one reactor (1), wherein the gaseous heterogeneous azeotrope is condensed in a condenser (5) and then fed to a phase separator (6) and the esterification water as the lower phase and the cyclohexane as the upper phase are separated in this phase separator (6).

[0012] In this document, the reference symbols in parentheses are intended to aid reading. The reference symbols in parentheses are not limiting, but merely represent one possible example among several possible implementations.

[0013] The individual procedural stages from I to VII are described below, whereby procedural stages II to VII are to be considered optional. Process stage I: Esterification

[0014] The process according to the invention is based on the reactants 2-octanol and (meth)acrylic acid. In this document, (meth)acrylic acid refers to a (meth)acrylic acid grade which preferably contains at least 98% by weight, more preferably at least 99.5% by weight, of (meth)acrylic acid, in addition preferably a maximum of 0.2% by weight of water and preferably a maximum of 0.03% by weight each of acetic acid, propionic acid and isobutyric acid. Preference is given to using a 2-octanol grade containing at least 99% by weight of 2-octanol, a maximum of 0.1% of 2-octanone, a maximum of 0.3% of 1-heptanol, a maximum of 0.3% of octenol (cis / trans), a maximum of 0.1% of other alcohols and a maximum of 0.5% of water. The color number is preferably a maximum of APHA 15, and the acid number a maximum of 0.2 mgKOH / g.

[0015] Suitable polymerization inhibitors that act as stabilizers can be, for example, N-oxides (nitroxyl or N-oxyl radicals, i.e. compounds that have at least one NO group), such as. B. 4-hydroxy-2,2,6,6-tetramethylpiperidine-N-oxyl (HO-TEMPO), 4-oxo-2,2,6,6-tetramethylpiperidine-N-oxyl, 4-acetoxy-2,2,6,6-tetramethylpiperidine-N-oxyl, 2,2,6,6-tetramethylpiperidine-N-oxyl, bis(1-oxyl-2,2,6,6-tetramethylpiperidine-4-yl)sebacate, 4,4',4"-tris(2,2,6,6-tetramethylpiperidine-N-oxyl)phosphite or 3-oxo-2,2,5,5-tetramethylpyrrolidine-N-oxyl; mono- or polyhydric phenols, which may contain one or more alkyl groups, such as alkylphenols, for example o-, m- or p-cresol (methylphenol), 2-tert-butylphenol, 4-tert-butylphenol, 2,4-di-tert-butylphenol, 2-methyl-4-tert-butyl-phenol, 2-tert-butyl-4-methylphenol, 2,6-tert-butyl-4-methylphenol, 4-tert-butyl-2,6-dimethylphenol or 6-tert-butyl-2,4-dimethylphenol; Quinones, such as b.Hydroquinone, hydroquinone monomethyl ether, 2-methylhydroquinone or 2,5-di-tert-butylhydroquinone; hydroxyphenols, such as pyrocatechol (1,2-dihydroxybenzene) or benzoquinone; aminophenols, such as p-aminophenol; nitrosophenols, such as p-nitrosophenol; alkoxyphenols, such as 2-methoxyphenol (guaiacol, pyrocatechol monomethyl ether), 2-ethoxyphenol, 2-isopropoxyphenol, 4-methoxyphenol (hydroquinone monomethyl ether), mono- or di-tert-butyl-4-methoxyphenol; tocopherols, such as α-tocopherol and 2,3-dihydro-2,2-dimethyl-7-hydroxybenzofuran (2,2-dimethyl-7-hydroxycoumaran), aromatic amines, such as B. N,N-diphenylamine or N-nitrosodiphenylamine; phenylenediamines, such as N,N'-dialkyl-p-phenylenediamine, where the alkyl radicals may be the same or different and each independently consists of 1 to 4 carbon atoms and may be straight-chain or branched, such as B.N,N'-Dimethyl-p-phenylenediamine or N,N'-Diethyl-p-phenylenediamine, hydroxylamines such as N,N-diethylhydroxylamine, imines such as methylethylimine or methylene violet, sulfonamides such as N-methyl-4-toluenesulfonamide or N-tert-butyl-4-toluenesulfonamide, oximes such as aldoximes, ketoximes or amidoximes such as diethyl ketoxime, methyl ethyl ketoxime or salicyladoxime, phosphorus-containing compounds such as triphenylphosphine, triphenyl phosphite, triethyl phosphite, hypophosphorous acid or alkyl esters of phosphorous acids; sulfur-containing compounds such as diphenyl sulfide or phenothiazine; Metal salts, such as copper or manganese, cerium, nickel, chromium salts, for example chlorides, sulfates, salicylates, tosylates, acrylates or acetates, such as copper acetate, copper(II) chloride, copper salicylate, cerium(III) acetate or cerium(III) ethylhexanoate, or mixtures thereof.

[0016] Preferably, at least one compound from the group consisting of hydroquinone, hydroquinone monomethyl ether, phenothiazine, 4-hydroxy-2,2,6,6-tetramethylpiperidine-N-oxyl, 4-oxo-2,2,6,6-tetramethylpiperidine-N-oxyl, bis(1-oxyl-2,2,6,6-tetramethyl-piperidine-4-yl) sebacate, 2-tert.-butylphenol, 4-tert.-butylphenol, 2,4-di-tert.-butylphenol, 2-tert.-butyl-4-methylphenol, 6-tert.-butyl-2,4-dimethylphenol, 2,6-di-tert.-butyl-4-methylphenol, 2-methyl-4-tert.-butylphenol, hypophosphorous acid, copper(II) acetate, Copper(I) chloride, copper(II) chloride, copper(II) salicylate and cerium(III) acetate are used.

[0017] Phenothiazine (PTZ) and / or hydroquinone monomethyl ether (MEHQ) are particularly preferably used as polymerization inhibitors.

[0018] PTZ is very particularly preferably used as a polymerization inhibitor in the esterification or in the optional use of an azeotropic rectification column unit (25). In the case of the optional downstream process steps, PTZ is also very particularly preferably used in the cyclohexane separation IV and / or in the 2-octanol separation V.

[0019] In particular, MEHQ is used as a polymerization inhibitor in the optional downstream process steps of pure boiler separation VI and / or high boiler separation VII.

[0020] The polymerization inhibitor is preferably dissolved in one or more liquid organic compounds. The organic compound is preferably 2-octanol and / or 2-octyl (meth)acrylate.

[0021] Suitable esterification catalysts include conventional mineral acids and sulfonic acids, preferably sulfuric acid, phosphoric acid, alkylsulfonic acids (e.g., methanesulfonic acid, trifluoromethanesulfonic acid), and arylsulfonic acids (e.g., benzenesulfonic acid, p-toluenesulfonic acid, or dodecylbenzenesulfonic acid), or mixtures thereof. Acidic ion exchangers or zeolites can also be used. Particularly preferred are sulfuric acid, methanesulfonic acid, p-toluenesulfonic acid, m-toluenesulfonic acid, o-toluenesulfonic acid, or mixtures thereof.

[0022] Methanesulfonic acid is particularly preferably used as an esterification catalyst.

[0023] In the process according to the invention, the reactants (meth)acrylic acid and 2-octanol and the entraining agent cyclohexane are fed continuously or discontinuously to one reactor (1) of the reactor unit (24), with continuous feeding being preferred.

[0024] In the process according to the invention, cyclohexane is used as an entraining agent. It has a boiling point of 81 °C at atmospheric pressure. The cyclohexane forms a heterogeneous azeotrope with the esterification water, and this heterogeneous azeotrope has a boiling point of only 70 °C at atmospheric pressure. With its boiling point of 70 °C, the heterogeneous azeotrope has a lower boiling point than pure water or other azeotropes such as 2-octanol with esterification water, toluene with esterification water, or octene with esterification water. Thus, using cyclohexane requires less energy to evaporate the heterogeneous azeotrope.

[0025] It was discovered that by adding an optimal amount of cyclohexane as an entrainer to one reactor (1) of the reactor unit (24), a lower bottom temperature can be set than with a different entrainer or with a suboptimal amount of cyclohexane, so that fewer secondary components are formed and, at the same time, the gas stream is as pure as possible besides the gaseous heterogeneous azeotrope, and this gas stream thus contains few other components, such as, for example, (meth)acrylic acid. Thus, the bottom temperature required for evaporation of the esterification water can also be significantly influenced by the amount of entrainer used.

[0026] A lower bottom temperature reduces, among other things, the formation of secondary components such as octenes, especially 1-octene and 2-octene. Octenes themselves also act as entrainers, but have a significantly higher boiling point than 2-octanol. For example, 1-octene has a boiling point of 121 °C at atmospheric pressure. The resulting secondary components also increase the separation problem of separating the heterogeneous azeotrope from the reaction mixture, as well as during purification by distillation.

[0027] Surprisingly, it was found that when using the same entrainer concentrations and the same other conditions, such as temperature, reaction time, molar ratios of the starting materials, the conversion is higher when using cyclohexane, but much fewer secondary components are formed, although the bottom temperature does not differ significantly and the bottom temperature at the end of the process is even highest when using cyclohexane, based on the other entrainers toluene and 2-octanol in excess or no entrainer.

[0028] Without an entraining agent, a large amount of water remains in the sump. To effectively remove the water, the process would have to be operated under vacuum conditions. However, processes under vacuum conditions are very complex and incur high costs for operation and for the construction of the process plant.

[0029] The lower boiling point of the heterogeneous azeotrope in one reactor (1) also results in less (meth)acrylic acid evaporating or vaporizing in the one reactor (1) and / or the reactor heating element (30). This increases the separation efficiency for separating the heterogeneous azeotrope from the reaction mixture.

[0030] In this document, the "reaction mixture" defines a liquid mixture which is formed during the esterification in one reactor (1) and thus also contains the desired product 2-octyl(meth)acrylate.

[0031] In this document, the "starting mixture" comprises the reactants 2-octanol and (meth)acrylic acid, as well as the acidic esterification catalyst, the polymerization inhibitor(s), and the entrainer cyclohexane. Through esterification, the starting mixture is converted into the reaction mixture.

[0032] In this document, the bottom temperature covers a temperature range from 90 to 130 °C. Changing the bottom temperature within this range can also influence the reaction kinetics, yield / conversion, selectivity, and / or the formation of secondary components, etc.

[0033] In this document, the terms "reactor sump" or "reactor sump" refer to a liquid mixture located below a gas mixture phase in the reactor (1). Thus, the reactor (1) is only partially filled with a liquid mixture, since during esterification, a portion of the liquid mixture, preferably the heterogeneous azeotrope, also evaporates and thus fills the reactor space above the liquid mixture.

[0034] In this document, the term "rectification column unit" defines one or more rectification columns, which may also contain other standard components such as pressure reducers, flow controllers, or sensors. The rectification column unit thus also includes their control system. In the case of multiple rectification columns, these can be connected in series or parallel.

[0035] Rectification columns are of a known design and feature the usual equipment, such as an evaporator in the bottom section, an evaporator in the high-boiler effluent, or a condenser in the low-boiler effluent. The high-boiler effluent is preferably located in the bottom section and the low-boiler effluent is preferably located in the top section of the rectification column. Typically, a portion of the mass flow of the high-boiler effluent is recycled to the bottom section of the rectification column. In principle, however, it is also possible for the bottom section to be heated, for example, by external wall heating of the column in the bottom section and / or for an evaporator to be integrated into the bottom section.

[0036] Typically, the mass flow of the low-boiling effluent is recycled to the top region of the rectification column after condensation in a condenser in the range of 10 to 200 wt.%.

[0037] In principle, all common column internals can be considered, such as trays, packings, and / or random packings. Bubble-cap trays, sieve trays, valve trays, Thormann trays, and / or dual-flow trays are preferred. Rings, spirals, saddles, or braids are preferred.

[0038] In this document, components are referred to as low boilers if their boiling point at atmospheric pressure is lower than the boiling point of 2-octyl acrylate. Similarly, components are referred to as high boilers if their boiling point at atmospheric pressure is greater than or equal to the boiling point of 2-octyl acrylate. The boiling point of 2-octyl acrylate is 211 °C at atmospheric pressure.

[0039] In this document, the term "reactor with a reactor heating element" generally defines a reactor (1) within a reactor unit (24) having one or more reactor heating elements (30) inside and / or outside the reactor (1) that heat the reaction mixture.The reactor heating element (30) or one of the reactor heating elements is, for example, an immersion heater in the reactor (1), a pipe system comprising pipe coils or half-pipe coils arranged on the outer surface of the reactor (1) and / or within the reactor (1), an electrical heating system arranged on the outer surface of the reactor (1) and / or within the reactor (1), an evaporator located outside the reactor (1), wherein the reaction mixture flows at least partially through the evaporator, or a double-walled embodiment of the reactor outer wall in which a fluid separated from the reaction mixture, such as a liquid, a gas and / or a heating vapor, is tempered and a predetermined heating temperature is thereby set, whereby the reaction mixture in the reactor (1) is heated. In general, several reactor heating elements can be used to heat the reaction mixture in the reactor (1).For example, a double-walled embodiment of the reactor outer wall and an evaporator located outside the reactor (1) can heat the reaction mixture simultaneously or at least partially at different times.

[0040] In this document, the term "evaporator" also refers to a reactor heating element (30). The evaporator may also contain other standard components, such as control valves, pressure reducers, flow regulators, or sensors. The evaporator may therefore also include a control system. In general, the term "evaporator" can also refer to multiple evaporators connected in series or parallel.

[0041] Examples of suitable evaporators are thin-film, falling-film, natural circulation, and forced circulation evaporators. The evaporators can be designed as shell-and-tube heat exchangers or plate heat exchangers. Suitable evaporators are known to those skilled in the art and are described, among others, in: SPX, Evaporator Handbook, APV, available at https: / / user-pages.umbc.edu / ~dfrey1 / ench445 / apv evap.pdf (accessed on November 1, 2021).

[0042] In this document, the term "reactor unit" defines one or more reactors, which may also contain other standard components such as pressure reducers, flow regulators, reactor heating elements, additional heating elements, lines, heat exchangers, or evaporators. The reactor unit (24) may also include control valves and / or sensors. Thus, the reactor unit (24) may also include a process control system. Of course, multiple heat exchangers per reactor or multiple heat exchangers in a network for all reactors of the reactor unit (24) may also be present.

[0043] In a further preferred embodiment, in the case of several reactors, the reactors are connected in parallel.

[0044] In a preferred embodiment, the reactor unit (24) comprises a plurality of reactors, wherein the reactors are connected in series. This enables cascading of two or more reactors connected in series, with the output stream of one reactor forming the feed stream of the next reactor.

[0045] In a preferred embodiment of the cascading, the components for the esterification are fed only to a first reactor (1) and only the reaction output resulting from the esterification is fed to the subsequent reactor.

[0046] In a preferred embodiment, one reactor (1) is equipped with internal or external heating coils and / or with a double-walled embodiment of the reactor outer wall.

[0047] In a preferred embodiment, one reactor (1) is equipped with an external evaporator, with internal and / or external heating coils and / or with a double-walled embodiment of the reactor outer wall.

[0048] In a preferred embodiment, one reactor (1) is equipped with an external evaporator and with a double-walled embodiment of the reactor outer wall.

[0049] In a preferred embodiment, one reactor (1) is equipped with an external evaporator and with internal and / or external heating coils.

[0050] In a preferred embodiment, one reactor (1) contains an external heat exchanger and / or evaporator.

[0051] In a preferred embodiment, one reactor (1) contains an evaporator. In the case of multiple reactors, each individual reactor contains its own evaporator.

[0052] In a further embodiment, the reactor unit (24) contains an evaporator to which all reactors of the reactor unit (24) are connected.

[0053] In a preferred embodiment, one reactor (1) is operated in natural circulation. This has the advantage that the reactor apparatus is more cost-effective because, among other things, it does not require a stirrer or other mechanical aids. The entraining agent cyclohexane ensures increased mixing.

[0054] In a preferred embodiment, the esterification is carried out continuously, in which the feed of the reactants and the entraining agent cyclohexane is carried out continuously and the evaporator unit is also operated continuously.

[0055] In a further embodiment, the esterification is carried out discontinuously, in which the reactants and the entraining agent cyclohexane are fed discontinuously.

[0056] In a preferred embodiment of the process, the gaseous heterogeneous azeotrope is fed to an azeotropic rectification column unit (25) downstream of the reactor unit (24), wherein an azeotropic rectification column (4) is located within the azeotropic rectification column unit (25), and the one azeotropic rectification column (4) is operated at an absolute pressure in the range from 0.5 to 2.0 bar and at a bottom temperature in the range from 90 to 130 °C, and the heterogeneous azeotrope is separated via the top of the one azeotropic rectification column (4), condensed in a condenser and then fed to a phase separator (6), wherein the esterification water is separated as the lower phase in the phase separator (6), whereas the cyclohexane is separated as the upper phase in the phase separator (6).

[0057] In a further embodiment, in the case of several reactors, each individual reactor contains an azeotropic rectification column unit (25) placed on it.

[0058] In a further embodiment, in the case of a plurality of reactors, each individual reactor contains an azeotropic rectification column unit (25) placed thereon, wherein the azeotropic rectification column unit (25) preferably contains exactly one azeotropic rectification column (4).

[0059] In a particularly preferred embodiment, an azeotropic rectification column unit (25) is mounted on the entire reactor unit (24), wherein the azeotropic rectification column unit (25) preferably contains precisely one azeotropic rectification column (4). This has the advantage that only one azeotropic rectification column (4) needs to be operated for the reactor(s), thus making the process energy- and cost-efficient.

[0060] In a preferred embodiment with multiple reactors, the rising vapors from all reactors are fed to a single azeotropic rectification column (4), with the liquid effluent from the azeotropic rectification column (4) being recycled only to the first reactor (1). The azeotropic rectification column unit (25) preferably contains only one azeotropic rectification column.

[0061] In a preferred embodiment, the azeotropic rectification column unit (25) is operated continuously.

[0062] In a preferred embodiment, the cyclohexane obtained as the upper phase in the phase separator (6) is at least partially or completely recycled to the reactor unit (24).

[0063] In a preferred embodiment, the cyclohexane obtained as the upper phase in the phase separator (6) is recycled to the reactor unit (24) in a weight proportion in the range from 40 to 100 wt.%, preferably in the range from 50 to 99.9 wt.%, and the resulting residual proportion of the cyclohexane obtained is recycled in the range from below the top to the middle of one azeotropic rectification column (4).

[0064] This has the advantage that the entraining agent content in the reactor unit (24) and / or the azeotropic rectification column unit (25) can be adjusted in order to be able to efficiently separate the esterification water or also to be able to carry out a targeted adjustment of the bottom temperature by feeding cyclohexane into the reactor (1).

[0065] In a preferred embodiment, the phase separator (6) is operated continuously by continuously flowing the inlets and outlets. Process stage II: Alkaline extraction

[0066] In a preferred embodiment, following the esterification, the resulting reaction product is subjected to alkaline extraction using an alkaline solution, in which, among other things, the acidic esterification catalyst and unreacted (meth)acrylic acid are neutralized in a neutralization-extraction unit (7). This results in an upper neutralization phase containing 2-octyl (meth)acrylate and a lower neutralization phase containing salts generated by the neutralization and water, and these two phases are thus separate from one another. The two neutralization phases are preferably generated by a dispersing apparatus, such as a mixing pump, and subsequently separated from one another in a phase separator (6) located within the neutralization-extraction unit (7).

[0067] In a preferred embodiment, the neutralization-extraction unit (7) is operated continuously by continuously flowing the inlets and outlets. Process stage III: Water wash extraction

[0068] In a preferred embodiment, following the alkaline extraction of the reaction effluent, the upper neutralization phase obtained from the neutralization extraction unit (7) is extracted with water in a water wash extraction unit (8), forming a lower water wash phase containing water and residual salts and an upper water wash phase containing 2-octyl (meth)acrylate, and these two phases are thus separate from one another. Preferably, the two water wash phases are generated by a dispersing apparatus, such as a mixing pump, and subsequently separated from one another in a phase separator (6) located within the water wash extraction unit (8).

[0069] Both the alkaline extraction (process stage II) and the water wash extraction (process stage III) can be carried out, for example, in a stirred tank or other conventional apparatus, e.g., in a column or a mixer-settler apparatus. In a mixer-settler or column, the corresponding processes are preferably carried out continuously. In a stirred tank, the corresponding processes are preferably carried out discontinuously.

[0070] There are different dispersion options for the mixer-settler apparatus, such as dispersion in a stirred tank, in a static mixer, in a pipeline or in a mixing pump and a phase separation apparatus.

[0071] Mixers and settlers can be designed more or less independently of each other. The mixing process can be adjusted, for example, by selecting the right agitator, agitator speed, power input, and / or throughput. In the case of a mixing pump, the power input can be adjusted preferentially.

[0072] Both the alkaline extraction (process stage II) and the water wash extraction (process stage III) can preferably be an extraction column, a centrifugal extractor or a mixer-settler apparatus.

[0073] In a particularly preferred embodiment, in the case of an alkaline extraction (process stage II), the resulting reaction effluent is dispersed with a dilute alkali by a pump, such as a mixing pump, and then fed to a phase separator (6) which separates the upper and lower neutralization phases from one another.

[0074] In terms of process technology, all known extraction and washing processes and extraction apparatus can be used, e.g., those described in Ullmann's Encyclopedia of Industrial Chemistry, 6th edition, 1999 Electronic Release, Chapter: Liquid - Liquid Extraction - Apparatus. These can be single- or multi-stage extractions, preferably single-stage extractions, which can be operated in cocurrent or countercurrent mode.

[0075] Water washing is preferably used when salts are to be separated.

[0076] In a preferred embodiment, the water wash extraction unit (8) is operated continuously by continuously flowing the inlets and outlets.

[0077] In a particularly preferred embodiment, a static mixer is used to disperse the upper neutralization phase obtained from the neutralization-extraction unit (7) with separately supplied water. The mixture dispersed from the static mixer is then fed to a phase separator (6), in which a lower water wash phase containing water and residual salts and an upper water wash phase containing 2-octyl (meth)acrylate are formed.

[0078] The following process stages IV to VII are preferably operated continuously. Process stage IV: Cyclohexane separation

[0079] In a preferred embodiment, following the alkaline extraction of the reaction effluent, the entraining agent cyclohexane is separated from the upper neutralization phase in an entraining agent rectification column unit, wherein an entraining agent rectification column (9) is located within the entraining agent rectification column unit, and the one entraining agent rectification column (9) is operated at a reduced absolute pressure in the range from 0.05 to 0.9 bar and at a bottom temperature in the range from 70 to 120 °C, and an organic phase is withdrawn via the top of the one entraining agent rectification column (9), which contains the entraining agent cyclohexane, octenes, 2-octanol and a mass flow proportion of 2-octyl (meth)acrylate in the range from 0.1 to 5.0%, based on the fed upper neutralization phase, wherein the components withdrawn via the top have an entraining agent mass flow form,this is condensed and fed in the range of 50 to 100% to one reactor (1) of the reactor unit (24), the remaining entraining agent mass flow portion being condensed and recycled at the top of the entraining agent rectification column (9), whereas high boilers containing di(meth)acrylic acid esters and oxyesters, such as the alkoxyalkyl ester of (meth)acrylic acid, as well as 2-octanol and 2-octyl (meth)acrylate are withdrawn through a bottom effluent of one entraining agent rectification column (9), wherein in the range of 20 to 95% of the mass flow of the bottom effluent flows through an evaporator and is then recycled to the one entraining agent rectification column (9).

[0080] In a preferred embodiment, following the water wash extraction, the entraining agent cyclohexane is separated from the upper water wash phase in an entraining agent rectification column unit, wherein an entraining agent rectification column (9) is located within the entraining agent rectification column unit, and the one entraining agent rectification column (9) is operated at a reduced absolute pressure in the range from 0.05 to 0.9 bar and at a bottom temperature in the range from 70 to 120 °C, and an organic phase is withdrawn via the top of the one entraining agent rectification column (9), which contains the entraining agent cyclohexane, octenes, 2-octanol and a mass flow proportion of 2-octyl (meth)acrylate in the range from 0.1 to 5.0%, based on the fed upper water wash phase, wherein the components withdrawn via the top form an entraining agent mass flow, this is condensed and in the range of 50 to 100 wt.-% is fed to one reactor (1) of the reactor unit (24), the remaining entraining agent mass flow portion being condensed and recycled at the top of the entraining agent rectification column (9), whereas high boilers which contain di(meth)acrylic acid esters and oxyesters, such as the alkoxyalkyl ester of (meth)acrylic acid, as well as 2-octanol and 2-octyl (meth)acrylate are withdrawn through a bottom effluent of the one entraining agent rectification column (9), wherein in the range of 20 to 95% of the mass flow of the bottom effluent flows through an evaporator and is then recycled into the one entraining agent rectification column (9).

[0081] In a particularly preferred embodiment, there is exactly one entraining agent rectification column (9) within the entraining agent rectification column unit. Process stage V: 2-octanol separation

[0082] In a particularly preferred embodiment, following the separation of the entraining agent cyclohexane, the 2-octanol is separated from the mass flow passing through the bottom effluent of one entraining agent rectification column (9) in a 2-octanol rectification column unit, wherein a 2-octanol rectification column (10) is located within the 2-octanol rectification column unit, and the

[0083] 2-octanol rectification column (10) is operated at a reduced absolute pressure in the range from 0.005 to 0.10 bar and at a bottom temperature in the range from 70 to 130 °C, and the mass flow given by the bottom outlet of the one entraining agent rectification column (9) is metered in in the range from below the top to the middle of the 2-octanol rectification column (10), and the components discharged via the top of the one 2-octanol rectification column (10) are condensed and fed to the one reactor (1) of the reactor unit (24) in a range of 20 to 50%, based on the mass flow of the components discharged via the top, wherein the discharged components consist of 2 to 40% by weight of 2-octanol.On the other hand, 2-octyl (meth)acrylate and high boilers containing di(meth)acrylic acid esters and oxyesters are withdrawn through a bottom effluent of the 2-octanol rectification column (10), with 20 to 95% of the mass flow of the bottom effluent flowing through an evaporator and then being recycled to the 2-octanol rectification column (10).

[0084] In a preferred embodiment, following the separation of the entraining agent cyclohexane, the 2-octanol is separated from the mass flow passing through the bottom outlet of one entraining agent rectification column (9) in a 2-octanol evaporator unit, wherein a 2-octanol evaporator (110) is located within the 2-octanol evaporator unit, and the one 2-octanol evaporator (110) is operated at a reduced absolute pressure in the range from 0.005 to 0.10 bar and at a bottom temperature in the range from 70 to 130 °C, and the mass flow passing through the bottom outlet of one entraining agent rectification column (9) is metered in at a 2-octanol inlet of the one 2-octanol evaporator, and the 2-octanol evaporator (110) Outlet of the components discharged from a 2-octanol evaporator in the range of 20 to 50%, based on the mass flow of the components discharged at the 2-octanol evaporator outlet, are fed to the reactor unit (24),These removed components consist of 2-octanol in the range of 2 to 40 wt.%. On the other hand, 2-octyl (meth)acrylate and high boilers containing di(meth)acrylic acid esters and oxyesters are removed through a bottom effluent of one 2-octanol evaporator, with 20 to 95% of the mass flow of the bottom effluent flowing through an evaporator and then being recycled to the one 2-octanol evaporator (110).

[0085] In a preferred embodiment, after the cyclohexane separation, the 2-octanol and simultaneously the 2-octyl (meth)acrylate are separated from the remaining components containing cyclohexane in a dividing wall column (131).

[0086] In a preferred embodiment, the dividing-wall column (131) is provided with a vertical dividing wall (138) that prevents cross-mixing of liquid and vapor streams in some areas. The dividing wall (138), which can be made of a flat sheet metal, divides the column longitudinally in its central region into an inlet section (140) and a discharge section (141).

[0087] In a preferred embodiment, the mixture to be separated, which contains low boilers, 2-octyl (meth)acrylate, and high boilers, is fed to the feed section (140), and 2-octyl (meth)acrylate is withdrawn in vapor or liquid form from the withdrawal section (141). The low boilers are separated via the top of the dividing wall column (131) and the high boilers via the bottom of the dividing wall column (131).

[0088] The energy requirements and investment costs are approximately 25% lower than with a conventional column arrangement with two rectification columns. Process stage VI: Pure boiler separation (separation of the target product 2-octyl(meth)acrylate)

[0089] In a preferred embodiment, following the separation of the 2-octanol, a pure boiler separation takes place from the mass flow given through the bottom outlet of the one 2-octanol rectification column (10) in a pure boiler rectification column unit, wherein a pure boiler rectification column (11) is located within the pure boiler rectification column unit, and the one pure boiler rectification column (11) is operated at a reduced absolute pressure in the range from 0.002 to 0.05 bar and at a bottom temperature in the range from 80 to 130 °C, and the mass flow given through the bottom outlet of the one 2-octanol rectification column (10) is metered in in the range from below the top to the middle of the one pure boiler rectification column (11), and to stabilize the one Pure boiler rectification column (11) 2-octyl(meth)acrylate and a polymerization inhibitor each in the range of 0.01 to 1.0%,based on the mass flow given by the bottom outlet of the one 2-octanol rectification column (10), in the region from the bottom to the middle of the one pure boiler rectification column (11), and the 2-octyl (meth)acrylate is withdrawn via the top of the one pure boiler rectification column (11), whereas high boilers, which contain di(meth)acrylic acid esters and oxyesters, such as the alkoxyalkyl ester of (meth)acrylic acid, are withdrawn through a bottom outlet of the one pure boiler rectification column (11).

[0090] In a particularly preferred embodiment, following the separation of the 2-octanol, a pure boiler separation takes place from the mass flow given through the bottom outlet of the one 2-octanol evaporator in a pure boiler evaporator unit, wherein a pure boiler evaporator is located within the pure boiler evaporator unit, and the one pure boiler evaporator (111) is operated at a reduced absolute pressure in the range from 0.002 to 0.05 bar and at a bottom temperature in the range from 80 to 130 °C, and the mass flow given through the bottom outlet of the one 2-octanol rectification column (10) or of the one 2-octanol evaporator is metered into a pure boiler evaporator inlet of the one pure boiler evaporator unit, and to stabilize the one pure boiler evaporator 2-octyl (meth)acrylate and a polymerization inhibitor in the range of 0.01 to 1.0%, based on the mass flow through the bottom outlet of a 2-octanol evaporator,are metered into a pure boiler evaporator inlet of one pure boiler evaporator, and the 2-octyl(meth)acrylate is withdrawn via a pure boiler evaporator outlet of one pure boiler evaporator, whereas high boilers, which contain di(meth)acrylic acid esters and oxyesters, such as the alkoxyalkyl ester of (meth)acrylic acid, are withdrawn through a bottom outlet of one pure boiler evaporator.

[0091] In a particularly preferred embodiment, the pure boiler evaporator unit contains exactly one pure boiler evaporator. Process stage VII: Separation of high boilers (di(meth)acrylic acid esters and oxyesters, such as the alkoxyalkyl ester of (meth)acrylic acid)

[0092] In a preferred embodiment, following the pure boiler removal, a high boiler removal takes place from the mass flow passing through the bottom outlet of one pure boiler rectification column (11) or one pure boiler evaporator in a high boiler rectification column unit, wherein one high boiler rectification column (12) is located within the high boiler rectification column unit, and the one high boiler rectification column (12) is operated at a reduced absolute pressure in the range from 0.002 to 0.05 bar and at a bottom temperature in the range from 80 to 150 °C, and the mass flow passing through the bottom outlet of one pure boiler rectification column (11) is metered in in the range from the bottom to the middle of the one high boiler rectification column (12),and the offtake taken via the top of the one high-boiler rectification column (12) is condensed and is fed in the region from the bottom to the middle of the one pure-boiler rectification column (11) or at the pure-boiler evaporator inlet of the one pure-boiler evaporator.

[0093] In a particularly preferred embodiment, the pure boiler separation is followed by a high boiler separation from the mass flow passing through the bottom effluent of the one pure boiler rectification column (11) or the one pure boiler evaporator in a high boiler evaporator unit, wherein a high boiler evaporator is located within the high boiler evaporator unit, and the one high boiler evaporator is operated at a reduced absolute pressure in the range from 0.002 to 0.05 bar and at a bottom temperature in the range from 80 to 150 °C,and the mass flow passing through the bottom outlet of one pure boiler evaporator is metered into a high boiler evaporator inlet of one high boiler evaporator and is condensed from the offtake taken from one high boiler evaporator and is recycled in the region from the bottom to the middle of one pure boiler rectification column (11) or at the pure boiler evaporator inlet of one pure boiler evaporator.

[0094] In a particularly preferred embodiment, the high-boiling evaporator unit contains exactly one high-boiling evaporator. Further preferred embodiments for process stages I and II

[0095] In a preferred embodiment, the bottom temperature in one reactor (1) of the reactor unit (24) is in the range from 100 to 125 °C, preferably 110 to 115 °C.

[0096] In a preferred embodiment, the esterification takes place at an absolute pressure in the range from 0.8 to 1.5 bar, particularly preferably from 0.9 to 1.2 bar.

[0097] In a preferred embodiment, less than 1.0% octenes are formed in the bottom of the reactor (1), based on the sum of the mass flows of 2-octanol (13), acidic esterification catalyst (15), polymerization inhibitors (31), and (meth)acrylic acid (14) fed to the reactor (1). This can be achieved, among other things, by applying the embodiments from the two preceding paragraphs.

[0098] In a preferred embodiment, cyclohexane is fed to the one reactor (1) of the reactor unit (24) in an amount in the range from 100 to 600 wt.%, preferably in the range from 200 to 500 wt.%, particularly preferably in the range from 350 to 450 wt.%, in each case based on the sum of the mass quantities of 2-octanol (13) and (meth)acrylic acid (14) fed to the one reactor (1) of the reactor unit (24).

[0099] In a preferred embodiment, cyclohexane with a concentration in the range of 10 to 90 wt.% is additionally metered into the one reactor (1) of the reactor unit (24), wherein the weight percentage of the concentration relates to the components present in the one reactor (1) of the reactor unit (24), including the metered-in cyclohexane.

[0100] In a preferred embodiment, the catalyst content in the one reactor (1) of the reactor unit (24) is a maximum of 10 wt.%, based on the sum of the 2-octanol and (meth)acrylic acid components present in the reactor (1) of the reactor unit (24).

[0101] In a preferred embodiment, the alkaline solution in process step (II) is aqueous NaOH, which contains in the range of 5 to 25 wt.% NaOH, preferably in the range of 10 to 20 wt.% NaOH.

[0102] In a preferred embodiment, the reactor contents in one reactor (1) are circulated in natural circulation or forced circulation.

[0103] In a preferred embodiment, the components flowing into one reactor (1) of the reactor unit (24) without the entraining agent cyclohexane have the following weight proportions: • 2-octanol: 40,00 until 84.39 wt% • (Meth)acrylic acid: 15,00 until 59.39 wt% • acid esterification catalyst: 0,50 until 10.00 wt.% • Polymerization inhibitor: 0,01 until 1.00 wt.% • Remaining components: 0,10 until 5.00 wt%.

[0104] The entraining agent cyclohexane is added in such an amount that a concentration of cyclohexane in the range of 10 to 90 wt.% is produced in the reactor (1) of the reactor unit (24), wherein this indication of the wt.% proportion refers to the components present in the reactor (1) of the reactor unit (24), including the cyclohexane.

[0105] In addition, in this preferred embodiment, the total components flowing out of the reactor (1) of the reactor unit (24) without the entraining agent cyclohexane and without the esterification water, namely the resulting liquid reaction effluent plus the portion evaporated from the reaction mixture and discharged from the reactor unit (24), have the following weight proportions: • 2-Octyl(meth)acrylate: 50,00 until 95.00 wt.% • 2-octanol: 1,00 until 30.00 wt.% • (Meth)acrylic acid: 1,00 until 15.00 wt.% • acid esterification catalyst: 0,50 until 10.00 wt.% • Polymerization inhibitor: 0,01 until 1.00 wt.% • Remaining components: 2,49 until 10.00 wt%.

[0106] The heterogeneous azeotrope formed by the cyclohexane and the esterification water flows out of the reactor (1) of the reactor unit (24) in a concentration in the range of 10 to 50 wt.%, whereby this indication of the wt.% proportion refers to the total components flowing out, including the cyclohexane and the esterification water.

[0107] In a particularly preferred embodiment, the components flowing into one reactor (1) of the reactor unit (24) without the entraining agent cyclohexane have the following weight proportions: • 2-octanol: 50,00 until 74.39 wt% • (Meth)acrylic acid: 25,00 until 45.00 wt.% • acid esterification catalyst: 0,50 until 5.00 wt.% • Polymerization inhibitor: 0,01 until 1.00 wt.% • Remaining components: 0,10 until 2.00 wt%.

[0108] The entraining agent cyclohexane is added in such an amount that a concentration of cyclohexane in the range of 10 to 50 wt.% is produced in the reactor (1) of the reactor unit (24), wherein this indication of the wt.% proportion refers to the components present in the reactor (1) of the reactor unit (24), including the cyclohexane.

[0109] In addition, in this particularly preferred embodiment, the components flowing out of the one reactor (1) of the reactor unit (24) without the entraining agent cyclohexane and without the esterification water, namely the resulting liquid reaction effluent plus the portion evaporated from the reaction mixture and discharged from the reactor unit (24), have the following weight proportions: • 2-Octyl(meth)acrylate: 70,00 until 95.00 wt.% • 2-octanol: 1,00 until 15.00 wt.% • (Meth)acrylic acid: 1,00 until 10.00 wt.% • acid esterification catalyst: 0,50 until 10.00 wt.% • Polymerization inhibitor: 0,01 until 1.00 wt.% • Remaining components: 2,49 until 10.00 wt%.

[0110] The heterogeneous azeotrope formed by the cyclohexane and the esterification water flows out of one reactor (1) of the reactor unit (24) in a concentration in the range of 10 to 50 wt.%, whereby this indication of the wt.% proportion refers to the total components flowing out, including the cyclohexane and the esterification water.

[0111] The invention is explained in more detail below with reference to the drawings. The drawings are to be understood as schematic representations. They do not represent a limitation of the invention, for example, with regard to specific dimensions or design variants.

[0112] They show: Fig. 1: Process diagram for the production of 2-octyl (meth)acrylate based on an evaporator as reactor heating element 30 for separating the heterogeneous azeotrope. Fig. 2: Process diagram for the production of 2-octyl (meth)acrylate based on an evaporator as reactor heating element 30 and an azeotrope rectification column unit 25 for separating the heterogeneous azeotrope. Fig. 3: Process diagram for the dividing wall column. List of reference symbols used:

[0113] 1Reactor 1 2Reactor 2 3Reactor 3 4Azeotrope rectification column 5Condenser for the heterogeneous azeotrope 6Phase separator for the heterogeneous azeotrope 7Neutralization extraction unit 8Water wash extraction unit 9Entrainer rectification column 102-octanol rectification column 1102-octanol evaporator 11High boiler rectification column 111High boiler evaporator 12High boiler rectification column 112High boiler evaporator 13Feed of 2-octanol 14Feed of (meth)acrylic acid 15Feed of acidic esterification catalyst 16Discharge of water discharged from the phase separator (6). 17Feed of cyclohexane 18Feed of water for the water wash 19Feed of alkaline solution 20Discharge of water with residual salts from the alkaline and / or water wash extraction 21Discharge of the valuable product 2-octyl (meth)acrylate 22Discharge of high boilers formed during the high boiler separation in the bottoms. 23Discharge of low boilers removed from the process during the cyclohexane separation after the cyclohexane-enriched mass flow is discharged. 24Reactor unit 25Azeotropic rectification column unit 30Reactor heating element 31Feed of polymerization inhibitor and / or other stabilizers 131 Dividing wall column 132 Mixture to be separated in the dividing wall column 134 Distillate stream of the dividing wall column 135 Partial stream of the dividing wall column 136 Condenser of the dividing wall column 137 Evaporator of the dividing wall column 138 Dividing wall of the dividing wall column 139 Common upper column section of the dividing wall column 140 Feed section of the dividing wall column 141 Withdrawal section of the dividing wall column 142 Stripping section of the dividing wall column 143 Rectifying section of the dividing wall column 144 Lower column section of the dividing wall column 145 Vapor stream of the dividing wall column 146 Reflux stream of the dividing wall column 147 Liquid stream of the dividing wall column

[0114] Fig. 1 shows a process diagram for the production of 2-octyl (meth)acrylate with the respective process steps, whereby each reactor contains an evaporator as a reactor heating element for the separation of the heterogeneous azeotrope. Process stage (I): Esterification

[0115] The esterification is carried out in a reactor unit 24 comprising three cascaded reactors 1, 2, and 3. The reactant streams: 2-octanol 13, (meth)acrylic acid 14, acidic esterification catalyst 15, polymerization inhibitors 31, and the entraining agent cyclohexane 17, flow into the first reactor 1 of the cascade. After the first reactor 1 of the cascade reaches a predetermined fill level, a mass flow flows to the second reactor 2 of the cascade. After the second reactor 2 of the cascade reaches a predetermined fill level, a mass flow flows to the third reactor 3 of the cascade. After the third reactor 3 reaches a predetermined fill level, a resulting reaction effluent flows out of the reaction unit. All three reactors 1, 2, 3 of the reactor unit 24 each contain their own evaporator 30 through which the reaction mixture flows, is heated and then returned to the respective reactor.In the evaporator 30, the esterification water formed during esterification and the entraining agent cyclohexane partially evaporate as a heterogeneous azeotrope (cyclohexane / esterification water).

[0116] A gas stream enriched with the heterogeneous azeotrope is withdrawn from the individual reactors 1, 2, and 3 and cooled by a downstream condenser 5 until condensation occurs. In a downstream phase separator 6, an organic upper phase and an aqueous lower phase are formed.

[0117] The aqueous lower phase is discharged from the process. The organic upper phase contains 50 to 99.9 wt.% cyclohexane. This organic upper phase is fed to the first reactor 1 of the cascade and to the azeotropic rectification column 4 in the region from the top to the middle of the column. Process stage (II): Alkaline extraction

[0118] The resulting reaction effluent from the esterification stage is neutralized with an alkaline solution 19 within a neutralization-extraction unit 7, neutralizing the acidic esterification catalyst and unreacted (meth)acrylic acid. This creates an upper neutralization phase containing 2-octyl (meth)acrylate and a lower neutralization phase containing salts generated by the neutralization and water. The lower neutralization phase 20 is discharged from the process. Process stage (III): Water wash extraction

[0119] Following the alkaline extraction, the upper neutralization phase is fed to a water wash extraction unit 8, where, with the addition of water 18, a lower water wash phase 20 containing water and residual salts and an upper water wash phase containing 2-octyl (meth)acrylate are formed. The lower water wash phase 20 is discharged from the process. Process stage (IV): Cyclohexane separation

[0120] The upper water wash phase from the water wash extraction is fed to an entrainer rectification column 9. Low boilers and cyclohexane are removed via the top of this column 9.

[0121] The components withdrawn via the top of column 9 are condensed in the range of 95 to 99.9 wt.% and recycled to the top of the entraining agent rectification column 9. The resulting remaining portion, after separation of gaseous low boilers 23, such as octenes, is fed to the first reactor 1 of the cascade. Typically, cyclohexane is fed from column 9 to the first reactor 1 of the cascade in a range of 2 to 20 wt.%, based on the total mass of cyclohexane fed to the process. Process stage (V): 2-octanol separation

[0122] The portion of the bottoms effluent not recycled to the entraining agent rectification column 9 is fed to a 2-octanol evaporator 110. 2-octanol is withdrawn via the 2-octanol evaporator 110 in an amount ranging from 20 to 60 wt. %, based on the bottoms effluent of the entraining agent rectification column 9 fed to the 2-octanol evaporator 110, condensed, and fed entirely to the first reactor 1 of the cascade. Process stage (VI): Pure boiler separation

[0123] The portion of the bottoms effluent not recycled to the 2-octanol evaporator 110 is fed to a pure boiler evaporator 111. Via a vapor stream from the pure boiler evaporator 111, the valuable product 2-octyl (meth)acrylate is withdrawn in a range of 80 to 95 wt. %, based on the bottoms effluent fed to the pure boiler evaporator 111, condensed, and completely recycled to the pure boiler evaporator 111. The resulting remaining portion of the bottoms effluent from the octanol evaporator 110 is condensed and completely fed to a high boiler evaporator 112. Process stage (VII): High boiler separation

[0124] The corresponding remaining portion of the bottoms effluent from the pure boiler evaporator 111 is fed to a high boiler evaporator 112. Via a vapor stream from the high boiler evaporator 112, low boilers in the range of 40 to 90 wt. %, based on the bottoms effluent from the pure boiler evaporator 111 fed to the high boiler evaporator 112, are withdrawn and completely returned to the pure boiler evaporator 111. The high boilers 22 present in the bottoms of the high boiler evaporator 112 are removed from the process in an amount of 1 to 10 wt. %, based on the circulation of the high boiler evaporator 112, with the resulting remaining portion of the high boilers 22 being evaporated and returned to the high boiler evaporator 112.

[0125] Fig. 2 shows a process diagram for the production of 2-octyl (meth)acrylate with the respective process steps, whereby an azeotropic rectification column 4 is used to separate the heterogeneous azeotrope. Process stage (I): Esterification

[0126] The esterification is carried out in a reactor unit 24 comprising three cascaded reactors 1, 2, and 3. The reactant streams: 2-octanol 13, (meth)acrylic acid 14, acidic esterification catalyst 15, polymerization inhibitors 31, and the entraining agent cyclohexane 17, flow into the first reactor 1 of the cascade. After the first reactor 1 of the cascade reaches a predetermined fill level, a mass flow flows to the second reactor 2 of the cascade. After the second reactor 2 of the cascade reaches a predetermined fill level, a mass flow flows to the third reactor 3 of the cascade. After the third reactor 3 reaches a predetermined fill level, a resulting reaction effluent flows out of the reaction unit. All three reactors 1, 2, 3 of the reactor unit 24 each contain their own evaporator 30 through which the reaction mixture flows, is heated and then returned to the respective reactor.In the evaporator 30, at least some of the esterification water and the entraining agent cyclohexane formed during the esterification evaporate as a heterogeneous azeotrope (cyclohexane / esterification water).

[0127] A gas stream enriched with the heterogeneous azeotrope is withdrawn from the individual reactors 1, 2, and 3 and fed to a downstream azeotrope rectification column 4. The azeotrope rectification column 4 is mounted on the reactor unit 24. Polymerization inhibitors 31 are added to the top of the azeotrope rectification column 4. The gas stream enriched with the heterogeneous azeotrope is passed over the top of the azeotrope rectification column 4 and cooled by a condenser 5 until condensation occurs. In a downstream phase separator 6, an organic upper phase and an aqueous lower phase are formed.

[0128] The aqueous lower phase is discharged from the process. The organic upper phase contains 50 to 99.9 wt.% cyclohexane. This organic upper phase is fed to the first reactor 1 of the cascade and to the azeotropic rectification column 4 in the region from the top to the middle of the column. Process stage (II): Alkaline extraction

[0129] The resulting reaction effluent from the esterification stage is neutralized with an alkaline solution within a neutralization-extraction unit 7, neutralizing the acidic esterification catalyst and unreacted (meth)acrylic acid. This creates an upper neutralization phase containing 2-octyl (meth)acrylate and a lower neutralization phase containing salts generated by the neutralization and water. The lower neutralization phase is discharged from the process. Process stage (III): Water wash extraction

[0130] Following the alkaline extraction, the upper neutralization phase is fed to a water wash extraction unit 8, where, with the addition of water 18, a lower water wash phase 20 containing water and residual salts and an upper water wash phase containing 2-octyl (meth)acrylate are formed. The lower water wash phase 20 is discharged from the process. Process stage (IV): Cyclohexane separation

[0131] The upper water wash phase from the water wash extraction is fed to an entrainer rectification column 9. Low boilers and cyclohexane are removed via the top of this column 9.

[0132] The components withdrawn via the top of column 9 are condensed in the range of 95 to 99.9 wt.% and recycled to the top of the entraining agent rectification column 9. The resulting remaining portion, after removal of low boilers 23, such as octenes, is fed to the first reactor 1 of the cascade. Typically, cyclohexane is fed from column 9 to the first reactor 1 of the cascade in a range of 2 to 20 wt.%, based on the total mass of cyclohexane fed to the process. Process stage (V): 2-octanol separation

[0133] The portion of the bottoms effluent not recycled to the entraining agent rectification column 9 is fed to a 2-octanol rectification column 10. 2-octanol is withdrawn via the top of this column 10 in an amount ranging from 20 to 60 wt. %, based on the bottoms effluent of the entraining agent rectification column 9 fed to column 10. The components withdrawn via the top of column 10 are completely condensed and recycled to the top region of the 2-octanol rectification column 10 in an amount ranging from 0 to 50 wt. %, whereas the resulting remaining portion of the top effluent is fed to the first reactor 1 of the cascade. Process stage (VI): Pure boiler separation

[0134] The portion of the bottoms effluent not recycled to the 2-octanol rectification column 10 is fed to a pure boiler rectification column 11. The valuable product 2-octyl (meth)acrylate is withdrawn via the top of this pure boiler rectification column 11 in a concentration of 80 to 95 wt. %, based on the bottoms effluent fed to column 11. The effluent via the top of the pure boiler rectification column 11 is completely condensed and recycled to the top region of the pure boiler rectification column 11 in a concentration of 0 to 60 wt. %. The resulting remaining portion of the bottoms effluent from the octanol rectification column 10 is fed to a high boiler removal stage. Process stage (VII): High boiler separation

[0135] The corresponding remaining portion of the bottoms effluent from the pure boiler rectification column 11 is fed to a high boiler rectification column 12. Low boilers in the range from 40 to 300 wt. %, based on the bottoms effluent fed to the high boiler rectification column 12, are withdrawn via the top of this high boiler rectification column 12, and a portion of the withdrawal in the range from 40 to 90 wt. % is recycled to the pure boiler rectification column 11, with the resulting remaining portion of the high boiler rectification column 12 being recycled to the top region of the column 12. The high boilers 22 located in the bottom of the high boiler rectification column 12 are at least partially removed from the process, the resulting remaining part of the high boilers 22 being evaporated and recycled in the bottom region of the high boiler rectification column 12.

[0136] Fig. 3 shows a process diagram for the dividing wall column.

[0137] The process diagram shows a dividing wall column 131 with a dividing wall 138, which divides the dividing wall column 131 into a common upper column section 139, an inlet section 140, 142, with a rectifying section 140 and a stripping section 142, a withdrawal section 141, 143 with a stripping section 141 and a rectifying section 143, and a common lower column section 144. The mixture 132 to be separated, which contains low boilers, 2-octyl (meth)acrylate, and high boilers, enters the dividing wall column 131 between the column sections 140 and 142. The pure product 133 is withdrawn between the column sections 141 and 143, preferably in liquid form. The vapor stream 145 accumulating at the top of the column is partially condensed in the condenser 136, which may be supplemented by an aftercooler, and divided into the reflux stream 146 and the distillate stream 134.The uncondensed portion from condenser 136 contains the low-boiling impurities and is withdrawn in vapor form as stream 139. At the lower end of the column, the liquid 147 is partially evaporated in an evaporator 137 and returned to the column via pipe 148. A partial stream 135, which contains the high-boiling impurities, is withdrawn. Evaporator 137 can be designed as a natural circulation evaporator or a forced circulation evaporator; in the latter case, a circulation pump for liquid stream 147 is also required. Particularly advantageous with regard to avoiding undesirable polymerization reactions is the use of a falling-film evaporator or thin-film evaporator instead of the forced circulation evaporator, since this design allows for the shortest residence times.

[0138] In order to reduce the residence time of the liquid in the evaporator system, it is advantageous to arrange the level control not in the lower column hood, but in the feed line of the liquid stream 147. Examples

[0139] In the following examples and throughout this document, the term "qualitative GC" refers to gas chromatography (GC) in which the individual components were assigned by retention time comparison. The concentration of the respective component in the mixture is assumed to be the percentage peak area (area %).

[0140] In the following examples and throughout this document, the term "quantitative GC" refers to gas chromatography (GC) with quantification using the internal standard n-tetradecane. The components 2-octylacrylate, cyclohexane, and 2-octanol were quantified. The concentration of each component in the mixture is expressed as a weight percent (wt%).

[0141] The expected amount of water corresponds to the amount of water at full conversion or infinite reaction time and is calculated from the sum of the water contents of the starting materials used and the esterification water to be formed at 100% conversion. The sum of these water contents is also referred to in this document as the reaction water. The maximum esterification water to be formed can be calculated from the moles of water formed, which are equivalent to the moles of acrylic acid used. A slight carryover of acrylic acid into the aqueous phase was not taken into account in the balance. Example 1: Discontinuous esterification with cyclohexane (process stage I)

[0142] A heatable 0.75 L double-walled reactor equipped with a thermocouple, anchor stirrer, water separator, intensive condenser, and air inlet was charged with 300 g of 2-octanol, 0.6 g of phenothiazine, 0.6 g of a 1 wt% solution of HO-TEMPO in 2-octyl acrylate, 130 g of cyclohexane, 0.015 g of CuCl, and 0.240 g of 50% hypophosphorous acid. Subsequently, 161 g of acrylic acid, stabilized with 200 ppm MeHQ, were added. 6.4 g of 100% methanesulfonic acid were added. The total batch size was 599 g.

[0143] The reaction mixture was heated to a bath temperature of 125 °C. The reaction time began with heating. During the reaction, bottom samples were taken and analyzed by gas chromatography to monitor the reaction progress.

[0144] After 0.58 h, at a bottom temperature of 99 °C, water began to form, and the distillation time began. The reaction was stopped after 6 h of distillation, equivalent to 6.59 h of reaction time, when a bottom temperature of 119 °C was reached. 35.6 g of water was distilled off, corresponding to 88.2% of the expected amount of water.

[0145] The reaction mixture was analyzed by gas chromatography after 6 hours of distillation. 2-Octanol and 2-octyl acrylate were quantified. After 6 hours of distillation, equivalent to 6.59 hours of reaction time, the mixture contained 71.54 wt% octyl acrylate and 5.75 wt% 2-octanol. The reaction mixture contained 0.27 wt% octenes, 1.78 wt% diacrylic acid esters, and 1.85 wt% oxyesters.

[0146] The conversion was 92.56% based on 2-octanol. Comparative Example 1: Discontinuous esterification with toluene (process stage I)

[0147] A heatable 0.75 L double-walled reactor equipped with a thermocouple, anchor stirrer, water separator, intensive condenser, and air inlet was charged with 300 g of 2-octanol, 0.6 g of phenothiazine, 0.6 g of a 1 wt% solution of HO-TEMPO in 2-octyl acrylate, 130 g of toluene, 0.015 g of CuCl, and 0.240 g of 50% hypophosphorous acid. Subsequently, 161 g of acrylic acid, stabilized with 200 ppm MeHQ, were added. 6.4 g of 100% methanesulfonic acid were added. The total batch size was 599 g.

[0148] The reaction mixture was heated to a bath temperature of 125 °C. The reaction time began with heating. During the reaction, bottom samples were taken and analyzed by gas chromatography to monitor the reaction progress.

[0149] After 0.92 h, at a bottom temperature of 108 °C, water began to pass over, and the distillation time began. The reaction was stopped after 6 h of distillation, equivalent to 6.92 h of reaction time, when a bottom temperature of 116 °C was reached. 17.7 g of water was distilled off, corresponding to 43.9% of the expected amount of water.

[0150] The reaction mixture was analyzed by gas chromatography after 6 hours of distillation. 2-Octanol and 2-octyl acrylate were quantified. After 6 hours of distillation, equivalent to 6.92 hours of reaction time, the mixture contained 58.38 wt% octyl acrylate and 13.35 wt% 2-octanol. The reaction mixture contained 0.15 area% octene, 2.18 area% diacrylic acid ester, and 1.57 area% oxyester.

[0151] The conversion was 81.39% based on 2-octanol. Comparative Example 2: Discontinuous esterification with 2-octanol as entrainer (process stage I)

[0152] A heatable 0.75 L double-walled reactor equipped with a thermocouple, anchor stirrer, water separator, intensive condenser, and air inlet was charged with 300 g of 2-octanol, 0.6 g of phenothiazine, 0.6 g of a 1 wt% solution of HO-TEMPO in 2-octyl acrylate, a further 130 g of 2-octanol, 0.015 g of CuCl, and 0.240 g of 50% hypophosphorous acid. Subsequently, 161 g of acrylic acid, stabilized with 200 ppm MeHQ, were added. 6.4 g of 100% methanesulfonic acid were added. The total batch size was 599 g.

[0153] The reaction mixture was heated to a bath temperature of 125 °C. The reaction time began with heating. During the reaction, bottom samples were taken and analyzed by gas chromatography to monitor the reaction progress.

[0154] After 1.22 h, at a bottom temperature of 112 °C, water began to pass over, and the distillation time began. The reaction was stopped after 6 h of distillation, equivalent to 7.22 h of reaction time, when a bottom temperature of 114 °C was reached. 12.8 g of water were distilled off, corresponding to 31.6% of the expected amount of water.

[0155] The reaction mixture was analyzed by gas chromatography after 6 hours of distillation. 2-Octanol and 2-octyl acrylate were quantified. After 6 hours of distillation, equivalent to 7.22 hours of reaction time, the mixture contained 54.64 wt% octyl acrylate and 33.01 wt% 2-octanol. The reaction mixture contained 0.09 wt% octenes, 1.11 wt% diacrylic acid esters, and 2.20 wt% oxyesters.

[0156] The conversion was 62.35% based on 2-octanol. Comparative Example 3: Discontinuous esterification without entraining agent (process stage I)

[0157] A heatable 0.75 L double-walled reactor equipped with a thermocouple, anchor stirrer, water separator, intensive condenser, and air inlet was charged with 383 g of 2-octanol, 0.6 g of phenothiazine, 0.6 g of a 1% solution of Hydroxy-Tempo in 2-octyl acrylate, 0.015 g of CuCl, and 0.240 g of 50% hypophosphorous acid. Subsequently, 206 g of acrylic acid, stabilized with 200 ppm MeHQ, were added. 8.2 g of 100% methanesulfonic acid were added. The total batch size was 599 g.

[0158] The reaction mixture was heated to a bath temperature of 125 °C. The reaction time began with heating. During the reaction, bottom samples were taken and analyzed by gas chromatography to monitor the reaction progress.

[0159] After 1.17 h, at a bottom temperature of 111 °C, water began to pass over, and the distillation time began. The reaction was stopped after 6 h of distillation, equivalent to 7.17 h of reaction time, when a bottom temperature of 113 °C was reached. 11.0 g of water was distilled off, corresponding to 21.4% of the expected amount of water.

[0160] The reaction mixture was analyzed by gas chromatography after 6 hours of distillation. 2-Octanol and 2-octyl acrylate were quantified. After 6 hours of distillation, equivalent to 7.17 hours of reaction time, the mixture contained 59.16 wt% octyl acrylate and 21.33 wt% 2-octanol. The reaction mixture contained 0.06 wt% octene, 2.57 wt% diacrylic acid ester, and 2.00 wt% oxyester.

[0161] The conversion was 73.5% based on 2-octanol. Summary

[0162] All experiments were conducted at a bath temperature of 125 °C. Acid and alcohol were used in the same molar ratio. An exception to this is the experiment with 2-octanol as the entrainer, in which the molar ratio of acrylic acid to 2-octanol was 1:1.45. The catalyst concentration relative to the acid used was always the same.

[0163] The entrainers used in the experiments were cyclohexane, toluene, and 2-octanol, which was present in addition to the 2-octanol for the reaction. Furthermore, no entrainer was used in one experiment. Tabular summary of the results

[0164] Table 1 shows an overview of the reaction in Example 1, which uses cyclohexane as the entrainer. The distillation time, reaction time, bottom temperature, reaction water, and conversion are listed. This water-based conversion was calculated as follows: wasserbasierter Umsatz % = Reaktionsswasser g t = x h Reaktionswasser g t = ∞ × 100 .

[0165] Here, the reaction water with t = ∞ represents the maximum expected amount of reaction water present at complete esterification. The reaction water with t = xh corresponds to the amount of reaction water present at time x hours due to the esterification and the water content of the starting materials used. Table 1: Overview of the reaction in Example 1, which uses cyclohexane as the entrainer. The distillation time, reaction time, bottom temperature, reaction water, and water-based conversion are listed. Distillation time [h] 0 1 2 3 4 5 6 Reaction time [h] 0,58 1,58 2,58 3,58 4,58 5,58 6,58 Sump temperature [°C] 99,2 107,4 112,8 116,1 117,7 118,5 118,9 Reaction water [g] 16,57 28,63 33,08 34,44 35,12 35,6 water-based sales [%] 41,07 70,95 81,98 85,35 87,04 88,23

[0166] Table 2 shows an overview of the GC values of the qualitative GC measurements at different distillation times for Example 1, which uses the entrainer cyclohexane. Listed are the sum of 1-octene and 2-octene, the diacrylic acid ester (DIAS ester), the oxyester, the 2-octyl acrylate content, the conversion calculated from the qualitative GC values, and the ratio of 2-octyl acrylate to the sum of the by-products 1-octene, 2-octene, DIAS ester, and oxyester.

[0167] The turnover was calculated as follows: Umsatz % = GC − Wert 2 − Octylacrylat Fl . − % GC − Wert 2 − Octylacrylat Fl . − % + GC − Wert 2 − Octanol Fl . − % × 100 .

[0168] The GC value (2-octyl acrylate) [area %] refers to the area percentage of 2-octyl acrylate measured by qualitative GC. Similarly, the GC value (2-octanol) [area %] refers to the area percentage of 2-octanol measured by qualitative GC. Table 2: Overview of the GC values of the qualitative GC measurements at different distillation times for Example 1, which uses the entrainer cyclohexane. Listed are the sum of 1-octene and 2-octene, the DIAS ester, the oxyester, the 2-octyl acrylate content, the conversion calculated from the qualitative GC values, and the ratio of 2-octyl acrylate to the sum of the by-products 1-octene, 2-octene, DIAS ester, and oxyester. Distillation time [h] 1 2 3 4 5 6 Total 1-Octene, 2-Octene [FI.-%] 0 0 0,1 0,15 0,21 0,27 DIAS esters [FI%] 1,05 1,34 1,55 1,7 1,76 1,78 Oxyester [FI%] 0,64 1,06 1,39 1,65 1,76 1,85 Content of 2-octylacrylate [FI%] 40,14 55,61 64,07 70,88 70,06 69,89 Sales volume [%] 57,07 77,35 86,36 90,13 91,59 92,36 Ratio of 2-octyl acrylate to the sum of the by-products 1-octene, 2-octene, DIAS ester, oxyester 100 : 4,2 100 : 4,3 100 : 4,7 100 : 4,9 100 : 5,3 100 : 5,6

[0169] Table 3 shows an overview of different distillation times for Example 1, which uses cyclohexane as the entrainer. The weight fraction of 2-octyl acrylate, the weight fraction of 2-octanol, and the molar conversion are listed. The molar conversion is calculated from the quantitative GC values.

[0170] The molar conversion was calculated as follows: Molarer Umsatz % = GC − Wert 2 − Octylacrylat Gew . − % / G _ Mol 2 − Octylacrylat g mol GC − Wert 2 − Octylacrylat Gew . − % / G _ Mol 2 − Octylacrylat g mol + GC − Wert 2 − Octanol Gew . − % / G _ Mol 2 − Octanol g mol 100 , × with the abbreviation G_Mol as molecular weight.

[0171] The GC value (2-octyl acrylate) [wt.%] refers to the proportion of 2-octyl acrylate quantified by gas chromatography. Similarly, the GC value (2-octanol) [wt.%] refers to the proportion of 2-octanol quantified by gas chromatography. Table 3: Overview of GC values at different distillation times for Example 1, which uses the entrainer cyclohexane. The weight fraction of 2-octyl acrylate, the weight fraction of 2-octanol, and the molar conversion are listed. The molar conversion is calculated from the quantitative GC values. Distillation time [h] 3 4 5 6 2-Octylacrylate [wt.%] 66,61 70,27 70,70 71,54 2-octanol [wt.%] 10,20 7,66 6,38 5,75 Molar turnover [%] 82,18 86,63 88,67 89,79

[0172] Table 4 shows an overview of the reaction in Comparative Example 1, which uses toluene as the entrainer. The distillation time, reaction time, bottom temperature, reaction water, and conversion are listed. This water-based conversion was calculated as follows: wasserbasierter Umsatz % = Reaktionsswasser g t = x h Reaktionswasser g t = ∞ × 100 .

[0173] Here, the reaction water with t = ∞ represents the maximum expected amount of reaction water present at complete esterification. The reaction water with t = xh corresponds to the amount of reaction water present at time x hours due to the esterification and the water content of the starting materials used. Table 4: Overview of the reaction in Comparative Example 1, which uses toluene as the entrainer. The distillation time, reaction time, bottom temperature, reaction water, and water-based conversion are listed. Distillation time [h] 0 1 2 3,00 4 5 6 Reaction time [h] 0,92 1,92 2,92 3,92 4,92 5,92 6,92 Sump temperature [°C] 107,8 111,4 113,1 114,1 115,1 115,6 115,9 Reaction water [g] 5,97 10,95 13,87 16,2 17,09 17,73 water-based sales [%] 14,80 27,14 34,37 40,15 42,35 43,94

[0174] Table 5 shows an overview of the GC values of the qualitative GC measurements at various distillation times for Comparative Example 1, which uses toluene as the entrainer. Listed are the sum of 1-octene and 2-octene, the DIAS ester, the oxyester, the 2-octyl acrylate content, the conversion calculated from the qualitative GC values, and the ratio of 2-octyl acrylate to the sum of the by-products 1-octene, 2-octene, DIAS ester, and oxyester.

[0175] The turnover was calculated as follows: Umsatz % = GC − Wert 2 − Octylacrylat Fl . − % GC − Wert 2 − Octylacrylat Fl . − % + GC − Wert 2 − Octanol Fl . − % × 100 .

[0176] The GC value (2-octyl acrylate) [area %] refers to the area percentage of 2-octyl acrylate measured by qualitative GC. Similarly, the GC value (2-octanol) [area %] refers to the area percentage of 2-octanol measured by qualitative GC. Table 5: Overview of the GC values of the qualitative GC measurements at different distillation times for Comparative Example 1, which uses toluene as the entrainer. Listed are the sum of 1-octene and 2-octene, the DIAS ester, the oxyester, the 2-octyl acrylate content, the conversion calculated from the qualitative GC values, and the ratio of 2-octyl acrylate to the sum of the by-products 1-octene, 2-octene, DIAS ester, and oxyester. Distillation time [h] 1 2 3 4,00 5 6 Total 1-Octene, 2-Octene [FI.-%] 0,08 0,11 0,12 0,15 DIAS esters [FI%] 1,59 1,85 2,00 2,18 Oxyester [FI%] 1,24 1,38 1,47 1,57 Content of 2-octylacrylate [FI%] 51,68 54,43 55,84 56,78 Sales volume [%] 73,96 77,56 79,28 80,79 Ratio of 2-octyl acrylate to the sum of the by-products 1-octene, 2-octene, DIAS ester, oxyester 100 : 5,6 100 : 6,1 100 : 6,4 100 : 6,9

[0177] Table 6 shows an overview of various distillation times for Comparative Example 1, which uses toluene as the entrainer. The weight fraction of 2-octyl acrylate, the weight fraction of 2-octanol, and the molar conversion are listed. The molar conversion is calculated from the quantitative GC values.

[0178] The molar conversion was calculated as follows: Molarer Umsatz % = GC − Wert 2 − Octylacrylat Gew . − % / G _ Mol 2 − Octylacrylat g mol GC − Wert 2 − Octylacrylat Gew . − % / G _ Mol 2 − Octylacrylat g mol + GC − Wert 2 − Octanol Gew . − % / G _ Mol 2 − Octanol g mol 100 , × with the abbreviation G_Mol as molecular weight.

[0179] The GC value (2-octyl acrylate) [wt.%] refers to the proportion of 2-octyl acrylate quantified by gas chromatography. Similarly, the GC value (2-octanol) [wt.%] refers to the proportion of 2-octanol quantified by gas chromatography. Table 6: Overview of GC values at different distillation times for Comparative Example 1, which uses toluene as the entrainer. The weight fraction of 2-octyl acrylate, the weight fraction of 2-octanol, and the molar conversion are listed. The molar conversion is calculated from the quantitative GC values. Distillation time [h] 3 4 5 6 2-Octylacrylate [wt.%] 52,87 55,90 57,62 58,38 2-octanol [wt.%] 17,87 15,53 14,46 13,35 Molar turnover [%] 67,64 71,77 73,79 75,55

[0180] Table 7 shows an overview of the reaction in Comparative Example 2, which uses 2-octanol as the entrainer. The distillation time, reaction time, bottom temperature, reaction water, and conversion are listed. This water-based conversion was calculated as follows: wasserbasierter Umsatz % = Reaktionsswasser g t = x h Reaktionswasser g t = ∞ × 100 .

[0181] Here, the reaction water with t = ∞ represents the maximum expected amount of reaction water present at complete esterification. The reaction water with t = xh corresponds to the amount of reaction water present at time x hours due to the esterification and the water content of the starting materials used. Table 7: Overview of the reaction in Comparative Example 2, which uses 2-octanol as the entrainer. The distillation time, reaction time, bottom temperature, reaction water, and water-based conversion are listed. Distillation time [h] 0 1 2 3 4 5 6 Reaction time [h] 1,22 2,22 3,22 4,22 5,22 6,22 7,22 Sump temperature [°C] 112,1 111,1 111,6 112,1 113,2 113,7 114,3 Reaction water [g] 1,24 3,34 6,09 8,96 11,02 12,76 water-based sales [%] 3,07 8,28 15,09 22,21 27,31 31,62

[0182] Table 8 shows an overview of the GC values of the qualitative GC measurements at various distillation times for Comparative Example 2, which uses the entrainer 2-octanol. Listed are the sum of 1-octene and 2-octene, the DIAS ester, the oxyester, the 2-octyl acrylate content, the conversion calculated from the qualitative GC values, and the ratio of 2-octyl acrylate to the sum of the by-products 1-octene, 2-octene, DIAS ester, and oxyester.

[0183] The turnover was calculated as follows: Umsatz % = GC − Wert 2 − Octylacrylat Fl . − % GC − Wert 2 − Octylacrylat Fl . − % + GC − Wert 2 − Octanol Fl . − % × 100 .

[0184] The GC value (2-octyl acrylate) [area %] refers to the area percentage of 2-octyl acrylate measured by qualitative GC. Similarly, the GC value (2-octanol) [area %] refers to the area percentage of 2-octanol measured by qualitative GC. Table 8: Overview of the GC values of the qualitative GC measurements at different distillation times for Comparative Example 2, which uses the entrainer 2-octanol. Listed are the sum of 1-octene and 2-octene, the DIAS ester, the oxyester, the 2-octyl acrylate content, the conversion calculated from the qualitative GC values, and the ratio of 2-octyl acrylate to the sum of the by-products 1-octene, 2-octene, DIAS ester, and oxyester. Distillation time [h] 1 2 3 4 5 6 Total 1-Octene, 2-Octene [FI.-%] 0,12 0,08 0,04 0,09 DIAS esters [FI%] 0,92 0,99 1,04 1,11 Oxyester [FI%] 1,62 1,82 2,00 2,20 Content of 2-octylacrylate [FI%] 51,46 53,71 55,20 56,46 Sales volume [%] 55,40 57,82 59,57 60,99 Ratio of 2-octyl acrylate to the sum of the by-products 1-octene, 2-octene, DIAS ester, oxyester 100 : 5,2 100 : 5,4 100 : 5,6 100 : 6,0

[0185] Table 9 shows an overview of various distillation times for Comparative Example 2, which uses 2-octanol as the entrainer. The weight fraction of 2-octyl acrylate, the weight fraction of 2-octanol, and the molar conversion are listed. The molar conversion is calculated from the quantitative GC values.

[0186] The molar conversion was calculated as follows: Molarer Umsatz % = GC − Wert 2 − Octylacrylat Gew . − % / G _ Mol 2 − Octylacrylat g mol GC − Wert 2 − Octylacrylat Gew . − % / G _ Mol 2 − Octylacrylat g mol + GC − Wert 2 − Octanol Gew . − % / G _ Mol 2 − Octanol g mol 100 , × with the abbreviation G_Mol as molecular weight.

[0187] The GC value (2-octyl acrylate) [wt.%] refers to the proportion of 2-octyl acrylate quantified by gas chromatography. Similarly, the GC value (2-octanol) [wt.%] refers to the proportion of 2-octanol quantified by gas chromatography. Table 9: Overview of GC values at different distillation times for Comparative Example 2, which uses 2-octanol as the entrainer. The weight fraction of 2-octyl acrylate, the weight fraction of 2-octanol, and the molar conversion are listed. The molar conversion is calculated from the quantitative GC values. Distillation time [h] 3 4 5 6 2-Octylacrylate [wt.%] 49,31 51,63 53,43 54,66 2-octanol [wt.%] 37,50 35,49 34,17 33,01 Molar turnover [%] 56,81 50,69 52,48 53,91

[0188] Table 10 shows an overview of the reaction in Comparative Example 3, which does not use an entrainer. The distillation time, reaction time, bottom temperature, reaction water, and conversion are listed. This water-based conversion was calculated as follows: wasserbasierter Umsatz % = Reaktionsswasser g t = x h Reaktionswasser g t = ∞ × 100 .

[0189] Here, the reaction water with t = ∞ represents the maximum expected amount of reaction water present at complete esterification. The reaction water with t = xh corresponds to the amount of reaction water present at time x hours due to the esterification and the water content of the starting materials used. Table 10: Overview of the reaction in Comparative Example 3, which does not use an entrainer. The distillation time, reaction time, bottom temperature, reaction water, and water-based conversion are listed. Distillation time [h] 0 1 2 3 4 5 6 Reaction time [h] 1,17 2,17 3,17 4,17 5,17 6,17 7,17 Sump temperature [°C] 110,7 110,2 110,6 111,1 111,7 112,0 112,5 Reaction water [g] 1,33 3,23 5,67 8,21 9,51 11,00 water-based sales [%] 2,58 6,27 11,01 15,95 18,47 21,37

[0190] Table 11 shows an overview of the GC values of the qualitative GC measurements at various distillation times for Comparative Example 3, which does not use an entrainer. Listed are the sum of 1-octene and 2-octene, the DIAS ester, the oxyester, the 2-octyl acrylate content, the conversion calculated from the qualitative GC values, and the ratio of 2-octyl acrylate to the sum of the by-products 1-octene, 2-octene, DIAS ester, and oxyester.

[0191] The turnover was calculated as follows: Umsatz % = GC − Wert 2 − Octylacrylat Fl . − % GC − Wert 2 − Octylacrylat Fl . − % + GC − Wert 2 − Octanol Fl . − % × 100 .

[0192] The GC value (2-octyl acrylate) [area %] refers to the area percentage of 2-octyl acrylate measured by qualitative GC. Similarly, the GC value (2-octanol) [area %] refers to the area percentage of 2-octanol measured by qualitative GC. Table 11: Overview of the GC values of the qualitative GC measurements at various distillation times for Comparative Example 11, which does not use an entrainer. Listed are the sum of 1-octene and 2-octene, the DIAS ester, the oxyester, the 2-octyl acrylate content, the conversion calculated from the qualitative GC values, and the ratio of 2-octyl acrylate to the sum of the by-products 1-octene, 2-octene, DIAS ester, and oxyester. Distillation time [h] 1 2 3 4 5 6 Total 1-Octene, 2-Octene [FI.-%] 0,06 0,04 0,07 0,06 DIAS esters [FI%] 1,82 2,13 2,34 2,57 Oxyester [FI%] 1,60 1,78 1,88 2,00 Content of 2-octylacrylate [FI%] 59,31 61,47 62,91 63,58 Sales volume [%] 67,13 69,69 71,2 72,41 Ratio of 2-octyl acrylate to the sum of the by-products 1-octene, 2-octene, DIAS ester, oxyester 100 : 5,9 100 : 6,4 100 : 6,8 100 : 7,3

[0193] Table 12 shows an overview of various distillation times for Comparative Example 3, which does not use an entrainer. The weight fraction of 2-octyl acrylate, the weight fraction of 2-octanol, and the molar conversion are listed. The molar conversion is calculated from the quantitative GC values.

[0194] The molar conversion was calculated as follows: Molarer Umsatz % = GC − Wert 2 − Octylacrylat Gew . − % / G _ Mol 2 − Octylacrylat g mol GC − Wert 2 − Octylacrylat Gew . − % / G _ Mol 2 − Octylacrylat g mol + GC − Wert 2 − Octanol Gew . − % / G _ Mol 2 − Octanol g mol × 100 , with the abbreviation G_Mol as molecular weight.

[0195] The GC value (2-octyl acrylate) [wt.%] refers to the proportion of 2-octyl acrylate quantified by gas chromatography. Similarly, the GC value (2-octanol) [wt.%] refers to the proportion of 2-octanol quantified by gas chromatography. Table 12: Overview of GC values at different distillation times for Comparative Example 3, which does not use an entrainer. The weight fraction of 2-octyl acrylate, the weight fraction of 2-octanol, and the molar conversion are listed. The molar conversion is calculated from the quantitative GC values. Distillation time [h] 3 4 5 6 2-Octylacrylate [wt.%] 54,47 56,46 57,96 59,16 2-octanol [wt.%] 25,28 23,19 22,32 21,33 Molar turnover [%] 60,35 63,24 64,73 66,21

[0196] The concentration of by-products increases as the reaction progresses. At similar conversion rates, the formation of by-products is significantly lower when cyclohexane is used as the entrainer compared to the entrainers toluene and 2-octanol, or when no entrainer is used.

[0197] The following Table 13 compares the ratio of 2-octyl acrylate to the sum of the by-products 1-octene, 2-octene, DIAS ester, and oxyester at similar conversions, each determined from the GC values of the qualitative GC. The examples with the respective entrainers cyclohexane, toluene, and 2-octanol are shown, as well as the example without entrainer. Table 13: Comparison of the ratio of 2-octyl acrylate to the sum of the by-products 1-octene, 2-octene, DIAS ester, and oxyester at similar conversions. Examples with the respective entrainers cyclohexane, toluene, and 2-octanol are shown, as well as the example without entrainer. Cyclohexane Sales volume [%] 57,07 77,35 86,36 Ratio of 2-octyl acrylate to the sum of the by-products 1-octene, 2-octene, DIAS ester, oxyester 100 : 4,2 100 : 4,3 100 : 4,7 toluene Sales volume [%] 77,56 80,79 Ratio of 2-octyl acrylate to the sum of the by-products 1-octene, 2-octene, DIAS ester, oxyester 100 : 6,1 100 : 6,9 2-octanol Sales volume [%] 55,40 Ratio of 2-octyl acrylate to the sum of the by-products 1-octene, 2-octene, DIAS ester, oxyester 100 : 5,2 Without entrainer Sales volume [%] 72,41 Ratio of 2-octyl acrylate to the sum of the by-products 1-octene, 2-octene, DIAS ester, oxyester 100 : 7,3

[0198] This results in the following advantages of using cyclohexane when comparing the results with comparative examples 1, 2 and 3: Using cyclohexane as an entrainer, the highest conversion is achieved with the same energy input. This results in fewer losses of (meth)acrylic acid in the subsequent alkaline extraction unit (process stage II). Furthermore, less 2-octanol is recycled, allowing smaller reactors to be used at the same throughput. Using cyclohexane as an entrainer, the reflux starts as quickly as possible after heating begins. This results in a shorter reaction time and less energy is required. Cyclohexane as an entrainer is the most effective at removing water. Using cyclohexane as an entrainer, the 2-octyl acrylate content in the reaction mixture is highest for the same reaction volume and distillation time. This results in the highest absolute space-time yield. Using cyclohexane as an entrainer, fewer by-products are formed at the same conversion. Comparative Example 4: Esterification, alkaline extraction and water washing without entraining agent (process stages I, II and III)

[0199] A heatable 0.75 L double-walled reactor equipped with, among other things, a thermocouple, an anchor stirrer, a glass attachment from Normag (source: www.normag-glas.de), which contains an intensive condenser, a drain port with two needle valves, a vacuum frame with two spindle valves as shut-off valves, and a vent valve, as well as a vacuum pump and an air inlet, was charged with 300 g of 2-octanol, 0.52 g of phenothiazine, 0.012 g of CuCl, and 0.207 g of 50% hypophosphorous acid. Subsequently, 209 g of acrylic acid, stabilized with 200 ppm MeHQ, were added. 6.4 g of 100% methanesulfonic acid were added. The reaction was heated to a bath temperature of 130 °C, which initiated the reaction time. After one hour, at a bottom temperature of 112 °C, water began to evaporate, and the distillation time began. After 2 hours of distillation, the absolute pressure was reduced in 50 mbar increments down to 100 mbar.The maximum internal temperature of the bottom was 122 °C. After 4.1 h of distillation, the reaction was stopped. 71.8 g were distilled off. After cooling, the reaction mixture was extracted with water, with 12.5% NaOH solution, and then again with water. After phase separation, the organic phase was treated with 50 mg of MeHQ. This yielded 403 g of 2-octyl acrylate with a purity of 85.4 GC area %. It still contained 3.5 area % of 2-octanol, 5.9 area % of diacrylic acid ester, and 3.1 area % of oxyester. The two-phase distillate was treated with ethanol to form a single phase and analyzed by qualitative GC, acid-base titration, and Karl Fischer titration. The composition of the distillate before the addition of ethanol was determined mathematically based on these results. The distillate consisted of 51.8% water, 29.5% acrylic acid, 6.3% 2-octanol, 9.5% 2-octyl acrylate and 2.2% octenes. Example 2: Esterification, alkaline extraction and water washing with cyclohexane (process stages I, II and III)

[0200] A heatable 4 L double-walled reactor equipped with, among other things, a temperature sensor, a disc stirrer, a water separator, an intensive cooler, and an air inlet was charged with 1503 g of 2-octanol, 4.01 g of phenothiazine, and 1.94 g of MeHQ. Then, 1082 g of acrylic acid, stabilized with 200 ppm of MeHQ, were added. 65.7 g of p-toluenesulfonic acid monohydrate and 1189 g of cyclohexane were added, and the reactor was heated. At a bottom temperature in the range of 92 to 104 °C, water evaporated. After 7.2 h, the reaction mixture was stopped. After cooling, the reaction mixture was extracted with water, with 12.5% NaOH solution, and then again with water. After phase separation, the organic phase was treated with 250 mg of MeHQ, and the mixture was concentrated in vacuo. 2072 g of 2-octyl acrylate with a purity of 93.2 GC area % were obtained. It also contained 2.6 area % of 2-octanol, 2.0 area % of diacrylic acid ester, and 1.3 area % of oxyester.A GC analysis of the organic liquid present in the water separator showed 99.38 GC area% cyclohexane, 0.47 area% acrylic acid, 0.03 area% 2-octanol, 0.1 area% 2-octyl acrylate, and 0.01 area% octene. A Karl Fischer titration of the aqueous distillate yielded 85 wt% water. Example 3: Esterification, alkaline extraction and water washing with cyclohexane (process stages I, II and III)

[0201] In this example 3, a reactor 1 and an azeotropic rectification column 4 were used, among other things. Process stages I, II, and III for esterification, alkaline extraction, and water scrubbing extraction were operated continuously.

[0202] A heatable 1.6 L double-walled glass reactor 1 was equipped with, among other things, a heatable lid and a 3-stage cross-beam stirrer.

[0203] The azeotropic rectification column 4 was a double-walled, mirrored glass column measuring 50 cm (height) x 43 mm (diameter) with a structured packing from Montz (source: www.montz.de / gewebepackung-typ-3a , accessed on November 1, 2021) was used (Montz Pak type A3-750, 3x 150 mm x 41 mm).

[0204] The setup also included a cooler, a phase separator 6 , a lean air inlet, containers and devices for reactant metering, containers and devices for the heteroazeotrope, a receiver for the bottoms discharge and a receiver for the stabilization of the column.

[0205] First, a stabilized reaction mixture was prepared in a batchwise experiment. It consisted essentially of 2-octanol, acrylic acid, 2-octyl acrylate, and methanesulfonic acid as a catalyst. The starting materials for preparing this reaction mixture were used in the proportions that corresponded to the starting mixture added later. The starting mixture for preparing the reaction mixture contained 45 wt.% 2-octanol, 25 wt.% pure acrylic acid, 0.93 wt.% 100% methanesulfonic acid, 29 wt.% cyclohexane, 0.04 wt.% hypophosphorous acid calculated as 100%, 0.1 wt.% phenothiazine, and 0.002 wt.% CuCl. The preparation was carried out analogously to Example 2.

[0206] The bath temperature was set to 128 °C and the lid temperature to 95 °C.

[0207] A total of 667 g / h of starting mixture was metered into the first reactor 1. The starting mixture can be placed in one or more containers, whereby the substance mixtures in the containers can vary in composition. In total, the starting mixture consisted of 45 wt.% 2-octanol, 25 wt.% pure acrylic acid, 0.93 wt.% 100% methanesulfonic acid, 29 wt.% cyclohexane, 0.04 wt.% hypophosphorous acid (calculated 100%), and 0.1 wt.% phenothiazine. Additionally, CuCl was metered in as a solid at regular intervals, so that the average concentration was 0.002 wt.%.

[0208] In addition, 350 g / h of cyclohexane, stabilized with HO-TEMPO, was added to the top of the column. Material was continuously withdrawn from reactor 1 under level control. The contents of reactor 1 were regularly analyzed by gas chromatography.

[0209] When equilibrium and a constant bottom temperature of 108 °C were reached, the reaction effluent container was changed, the foreshot material was discarded, and the new reaction effluent was collected.

[0210] In a second experiment, this material was fed into reactor 1, which was still filled with the reaction mixture from the previous experiment, at the same rate as the withdrawal in the first experiment. In addition, 150 g / h of cyclohexane was added to the bottom of the column, and 50 g / h of cyclohexane (stabilized with HO-TEM PO) was added to the top of the column. Again, material was continuously withdrawn from reactor 1 at a controlled fill level.

[0211] Once equilibrium and a constant bottom temperature of 113 °C were established, the reaction effluent container was changed, the foreshot material was discarded, and the new reaction effluent was collected.

[0212] In a third experiment, this material was fed into reactor 1, which was still filled with the reaction mixture from the previous experiment, at the same rate as the withdrawal in the second experiment. In addition, 150 g / h of cyclohexane was added to the bottom of the column, and 50 g / h of cyclohexane (stabilized with HO-TEMPO) was added to the top of the column. Again, material was continuously withdrawn from reactor 1 at a controlled fill level.

[0213] Once equilibrium and a constant bottom temperature of 114 °C were established, the reaction effluent container was changed, the foreshot material was discarded, and the new reaction effluent was collected.

[0214] This material was analyzed by acid-base titration and qualitative and quantitative gas chromatography. Octyl acrylate, cyclohexane, and 2-octanol were quantified by gas chromatography, while acrylic acid and methanesulfonic acid were determined by acid-base titration. The content of the minor components octenes, diacrylic acid esters, and oxyesters was determined by qualitative GC. For the minor components, which are present only in small amounts in the reaction mixture, it was further assumed that the values determined as area percentage correspond to the values that would be obtained by quantification.

[0215] This reaction effluent contained 67.6 wt% 2-octyl acrylate, 22.4 wt% cyclohexane, 3.1 wt% 2-octanol, 2.4 wt% acrylic acid, 1.1 wt% methanesulfonic acid, 0.26 wt% octenes, 1.1 wt% diacrylic acid esters and 1.5 wt% oxyesters.

[0216] The reaction effluent was subjected to continuous neutralization within an alkaline extraction unit 7 and subsequently to water washing within a water washing extraction unit 8.

[0217] The alkaline extraction unit 7 contains a continuous apparatus for neutralization with 10% sodium hydroxide solution (NaOH). This continuous apparatus consists of a mixing pump and a phase separator 6 with a diameter of 40 mm and a separation layer control.

[0218] At a temperature of 30°C, 0.76 kg / h of the diluted sodium hydroxide solution NaOH and 3.3 kg / h of the reaction effluent were dispersed via the mixing pump and separated in the phase separator 6. The neutralized organic phase was then washed in the water wash extraction unit 8 with 5 kg / h of water through a static mixer (Kenics mixer (https: / / de.wikipedia.org / wiki / Statischer_Mischer, accessed on November 23, 2021) with 4.9 mm inner diameter and 27 elements) and then separated in a phase separator 6 with a diameter of DN40. Example 4: Distillation (process stages IV to VII)

[0219] The distillative purification of 2-octyl acrylate was carried out in four subsequent, continuously operated process steps: Cyclohexane separation (IV) 2-octanol separation (V) Pure boiler separation (VI) High boiler separation (VII)

[0220] The experimental setup was identical for each process stage IV to VII and included a thin-film evaporator with an area of 0.016 square meters, which was used in the respective rectification columns 9, 10, 11, and 12. The respective rectification columns 9, 10, 11, and 12 had a diameter of 30 mm and a packing length of 100 cm. The packing in the respective rectification columns 9, 10, 11, and 12 was Montz A3-750. The condenser 5 belonging to the respective rectification columns 9, 10, 11, 12 with reflux divider for the reflux and the distillate discharge was of course present, as were the containers and pumps for the metered addition of the reactants, the containers and devices for the distillate, the container for the bottoms discharge and the container for the stabilization of columns 9, 10, 11, 12.

[0221] The thin-film evaporator was heated with Marlotherm oil.

[0222] In this example 4, the individual components were determined using various measurement methods. Water was determined using a Karl Fischer titration, while 2-octyl acrylate, cyclohexane, and 2-octanol were determined using quantitative GC. The remaining components were determined using qualitative GC. Cyclohexane separation

[0223] The mixture coming from the water wash extraction unit 8 had the following composition: Water 0.30 wt.% Cyclohexane 23.80 wt.% Octene 0.29 wt.% 2-octanol 3.95 wt.% 2-Octylacrylate 68.80 wt.% Diacrylic acid esters 1.14 wt.% Oxyester 1.54 wt.% unknown rest

[0224] The feed rate to the top of the entrainer rectification column 9 was 300 g / h.

[0225] The absolute pressure at the top of the column was 100 mbar and the bottom temperature was 105°C.

[0226] The effluent bottom product of 230 g / h had the following composition: Water 0.00 wt.% Cyclohexane 1.07 wt% Octene 0.34 wt% 2-octanol 5.14 wt% 2-Octylacrylate 89.72 wt% Diacrylic acid esters 1.49 wt% Oxyester 2.01 wt.% unknown rest

[0227] The effluent distillate of 70 g / h had the following composition: Water 1.28 wt.% Cyclohexane 98.50 wt.% Octene 0.11 wt.% 2-octanol 0.05 wt.% 2-Octylacrylate 0.06 wt.% Diacrylic acid esters 0.00 wt.% Oxyester 0.00 wt.% 2-octanol separation

[0228] For the separation of 2-octanol, the same experimental apparatus was used as in the previous process step. The bottom effluent from the cyclohexane separation was added at a rate of 230 g / h to the top of the 2-octanol rectification column 10. The absolute pressure at the top of the column was 10 mbar, and the bottom temperature was 89°C.

[0229] The effluent bottom product of 190 g / h had the following composition: Water 0.00 wt.% Cyclohexane 0.00 wt.% Octene 0.00 wt.% 2-octanol 0.01 wt.% 2-Octylacrylate 95.47 wt% Diacrylic acid esters 1.80 wt.% Oxyester 2.43 wt% unknown rest

[0230] The effluent distillate of 40 g / h had the following composition: Water 0.00 wt.% Cyclohexane 6.12 wt.% Octene 1.98 wt.% 2-octanol 29.50 wt.% 2-Octylacrylate 62.40 wt.% Diacrylic acid esters 0.00 wt.% Oxyester 0.00 wt.% Pure boiler separation

[0231] The same experimental apparatus was used for the pure boiler separation as in the previous process steps. The bottom effluent from the 2-octanol separation experiment was added at a rate of 190 g / h to the bottom of the pure boiler rectification column 11. The absolute pressure at the column head was 10 mbar and the bottom temperature was 95 °C. A reflux ratio of 3 g / g was set at the reflux divider. To prevent polymerization in the experimental apparatus, 2-octyl acrylate (stabilized with 1% phenothiazine) was added at the top of the pure boiler rectification column 11 at a rate of 2 g / h.

[0232] The effluent bottom product of 32 g / h had the following composition: Water 0.00 wt.% Cyclohexane 0.00 wt.% Octene 0.00 wt.% 2-octanol 0.00 wt.% 2-Octylacrylate 74.49 wt% Diacrylic acid esters 10.69 wt.% Oxyester 14.44 wt% Phenothiazin 0.13 wt.% unknown rest

[0233] The effluent distillate of 160 g / h had the following composition: Water 0.00 wt.% Cyclohexane 0.00 wt.% Octene 0.00 wt.% 2-octanol 0.01 wt.% 2-Octylacrylate 99.70 wt.% Diacrylic acid esters 0.00 wt.% Oxyester 0.00 wt.% unknown rest High boiler separation

[0234] The same experimental equipment was used to separate the high boilers as in the previous process steps. The bottom effluent from the pure boiler separation was added at a rate of 32 g / h to the bottom of the high boiler rectification column 12. The absolute pressure at the top of the column was 5 mbar, and the bottom temperature was 100°C. A reflux ratio of 3 g / g was set at the reflux divider.

[0235] The effluent bottom product of 16 g / h had the following composition: Water 0.00 wt.% Cyclohexane 0.00 wt.% Octene 0.00 wt.% 2-octanol 0.00 wt.% 2-Octylacrylate 49.27 wt% Diacrylic acid esters 21.37 wt% Oxyester 28.87 wt% Phenothiazin 0.25 wt.% unknown rest

[0236] The effluent distillate of 16 g / h had the following composition: Water 0.00 wt.% Cyclohexane 0.00 wt.% Octene 0.00 wt.% 2-octanol 0.00 wt.% 2-Octylacrylate 99.72 wt.% Diacrylic acid esters 0.00 wt.% Oxyester 0.00 wt.% unknown rest

Claims

1. A process for producing 2-octyl (meth)acrylate by reacting 2-octanol with (meth)acrylic acid in the presence of an acidic esterification catalyst, a polymerization inhibitor and the azeotroping agent cyclohexane, comprising the steps of: • providing a reactor unit (24), wherein a reactor (1) having a reactor heating element (30) is located within the reactor unit (24), • feeding 2-octanol (13), (meth)acrylic acid (14), acidic esterification catalyst (15), cyclohexane (17) and polymerization inhibitor (31) into the reactor (1), • carrying out an esterification in the reactor (1) to form a liquid reaction mixture, wherein the esterification in the reactor (1) is conducted at a bottom temperature in the range of 90 to 130°C and at an absolute pressure in the range of 0.5 to 2.0 bar, and a resulting reaction discharge from the reactor (1) is obtained, wherein the resulting reaction discharge comprises at least 2-octyl (meth)acrylate, 2-octanol, (meth)acrylic acid, acidic esterification catalyst, cyclohexane, water of esterification and polymerization inhibitor, and the water of esterification formed in the esterification together with the azeotroping agent cyclohexane forms a heterogeneous azeotrope, • evaporating the heterogeneous azeotrope from the liquid reaction mixture of the reactor (1), wherein the evaporation is accomplished by the reactor heating element (30), and • removing the gaseous heterogeneous azeotrope from the reactor (1), wherein the gaseous heterogeneous azeotrope is condensed in a condenser (5) and is then fed to a phase separator (6) and the water of esterification is separated off as the lower phase and the cyclohexane as upper phase in this phase separator (6).

2. The process according to claim 1, wherein the gaseous heterogeneous azeotrope is fed to an azeotrope rectification column unit (25) downstream of the reactor unit (24), wherein an azeotrope rectification column (4) is located within the azeotrope rectification column unit (25), and the azeotrope rectification column (4) is operated at an absolute pressure in the range of 0.5 to 2 bar and at a bottom temperature in the range of 90 to 130°C, and the heterogeneous azeotrope is removed via the top of the azeotrope rectification column (4), is condensed in a condenser (5) and is then fed to a phase separator (6), wherein the water of esterification (16) is separated off as the lower phase in the phase separator (6), while the cyclohexane is separated off as the upper phase in the phase separator (6).

3. The process according to claim 1 or 2, wherein the cyclohexane obtained as upper phase in the phase separator (6) is partially or fully recycled to the reactor unit (24).

4. The process according to claim 2, wherein the cyclohexane obtained as upper phase in the phase separator (6) is recycled to the reactor unit (24) at a proportion by weight in the range of 40% by weight to 100% by weight, preferably in the range of 50 to 99.9% by weight, and the resulting residual proportion of the cyclohexane obtained is recycled into the area from below the top to the middle of the azeotrope rectification column (4).

5. The process according to any of claims 1 to 4, wherein subsequent to the esterification, an alkaline extraction of the resulting reaction discharge is carried out by means of an alkaline solution (19), in which the acidic esterification catalyst and unreacted (meth)acrylic acid are neutralized in a neutralization extraction unit (7), and which results in an upper neutralization phase comprising 2-octyl (meth)acrylate, and a lower neutralization phase comprising salts generated by the neutralization and water (20).

6. The process according to claim 5, wherein subsequent to the alkaline extraction of the reaction discharge, the upper neutralization phase obtained from the neutralization extraction unit (7) is extracted with water (18) in a waterwash extraction unit (8), wherein a lower waterwash phase comprising water and salt residues and an upper waterwash phase comprising 2-octyl (meth)acrylate are formed.

7. The process according to claim 5 or 6, wherein subsequent to the alkaline extraction of the reaction discharge or subsequent to the waterwash extraction, the azeotroping agent cyclohexane is separated off from the upper neutralization phase or from the upper waterwash phase in an azeotrope rectification column unit, wherein an azeotrope rectification column (9) is located within the azeotrope rectification column unit, and the azeotrope rectification column (9) is operated at a reduced absolute pressure in the range of 0.05 to 0.9 bar and at a bottom temperature in the range of 70 to 120°C, and an organic phase is removed via the top of the azeotrope rectification column (9) comprising the azeotroping agent cyclohexane, octenes, 2-octanol and a mass flow proportion of 2-octyl (meth)acrylate in the range of 0.1 to 5.0%, based on the upper neutralization phase fed in or the upper waterwash phase fed in, wherein the components discharged overhead form an azeotrope mass flow, this being condensed and fed into the reactor (1) of the reactor unit (24) in the range of 50 to 100%, wherein the residual azeotrope mass flow proportion is condensed and is recycled to the top of the azeotrope rectification column (9), while high boilers comprising di(meth)acrylic acid esters and oxy esters, such as the alkoxyalkyl esters of (meth)acrylic acid, and also 2-octanol and 2-octyl (meth)acrylate are removed through a bottom discharge of the azeotrope rectification column (9), wherein in the range of 20 to 95% of the mass flow of the bottom discharge flows through an evaporator and is subsequently recycled to the azeotrope rectification column (9).

8. The process according to claim 5 or 6, wherein the 2-octyl (meth)acrylate is separated in a dividing wall column (131) from the residual components comprising cyclohexane and 2-octanol.

9. The process according to claim 7, wherein subsequent to the removal of the azeotroping agent cyclohexane, 2-octanol is separated off from the mass flow produced by the bottom discharge of the azeotrope rectification column (9) in a 2-octanol rectification column unit or a 2-octanol evaporation unit, wherein a 2-octanol rectification column (10) is located within the 2-octanol rectification column unit or a 2-octanol evaporator (110) is located within the 2-octanol evaporation unit, and the 2-octanol rectification column (10) or the 2-octanol evaporator (110) is operated at a reduced absolute pressure in the range of 0.005 to 0.10 bar and at a bottom temperature in the range of 70 to 130°C, and the mass flow produced by the bottom discharge of the azeotrope rectification column (9) is metered in to the area below the head to the middle of the 2-octanol rectification column (10) or to a 2-octanol inlet of the 2-octanol evaporator (110), and the components discharged via the head of the 2-octanol rectification column (10) or via a 2-octanol evaporator outlet of the 2-octanol evaporator (110) are fed to the reactor unit (24) in the range of 20 to 50%, based on the mass flow of the discharged components, wherein the discharged components in the range of 2 to 40% by weight consist of 2-octanol, while 2-octyl (meth)acrylate and high boilers comprising di(meth)acrylic acid esters and oxy esters are withdrawn through a bottom discharge of the 2-octanol rectification column (10) or the 2-octanol evaporator (110), wherein 20 to 95% of the mass flow of the bottom discharge flows through an evaporator and is subsequently recycled to the 2-octanol rectification column (10) or to the 2-octanol evaporator (110).

10. The process according to claim 9, wherein subsequent to the separation of 2-octanol, a pure boiler separation from the mass flow provided through the bottom discharge of the 2-octanol rectification column (10) or the 2-octanol evaporator (110) is carried out in a pure boiler rectification column unit or a pure boiler evaporation unit, wherein a pure boiler rectification column (11) is located within the pure boiler rectification column unit or a pure boiler evaporator (111) within the pure boiler evaporation unit, and the pure boiler rectification column (11) or the pure boiler evaporator (111) is operated at a reduced absolute pressure in the range of 0.002 to 0.05 bar and at a bottom temperature in the range of 80 to 130°C, and the mass flow produced by the bottom discharge of the 2-octanol rectification column (10) or the 2-octanol evaporator (110) is metered into the area from below the head to the middle of the pure boiler rectification column (11) or to a pure boiler evaporator inlet of the pure boiler evaporator (111), and to stabilize the pure boiler rectification column (11) or the pure boiler evaporator (111), 2-octyl (meth)acrylate and a polymerisation inhibitor, each in the range of 0.01 to 1.0 %, based on the mass flow produced by the bottom discharge of the 2-octanol rectification column (10) or by the bottom discharge of the 2-octanol evaporator (110), are metered into the area from the bottom up to the middle of the pure boiler rectification column (11) or to a pure boiler evaporator inlet of the pure boiler evaporator (111), and the 2-octyl (meth)acrylate (21) is withdrawn via the head of the pure boiler rectification column (11) or via a pure boiler evaporator outlet of the pure boiler evaporator (111), while high boilers comprising di(meth)acrylic acid esters and oxy esters, such as the alkoxyalkyl esters of (meth)acrylic acid, are withdrawn through a bottom discharge of the pure boiler rectification column (11) or of the pure boiler evaporator (111).

11. The process according to claim 10, wherein subsequent to the pure boiler separation, a high boiler separation from the mass flow produced through the bottom discharge of the pure boiler rectification column (11) or of the pure boiler evaporator (111) is carried out in a high boiler rectification column unit or a high boiler evaporation unit, wherein a high boiler rectification column (12) is located within the high boiler rectification column unit or a high boiler evaporator (112) within the high boiler evaporator unit, and the high boiler rectification column (12) or the high boiler evaporator (112) is operated at a reduced absolute pressure in the range of 0.002 to 0.05 bar and at a bottom temperature in the range of 80 to 150°C, and the mass flow produced by the bottom discharge of the pure boiler rectification column (11) or the pure boiler evaporator (111) is metered into the area from the bottom up to the middle of the high boiler rectification column (12) or to a high boiler evaporator inlet of the high boiler evaporator (112), and the takeoff withdrawn via the top of the high boiler rectification column (12) or the high boiler evaporator (112) is condensed and is fed into the area from the bottom up to the middle of the pure boiler rectification column (11) or to the pure boiler evaporator inlet of the pure boiler evaporator (111).

12. The process according to any of the preceding claims, wherein the bottom temperature in the reactor (1) of the reactor unit (24) is in the range of 100 to 125°C, preferably in the range of 110 to 115°C.

13. The process according to any of the preceding claims, wherein cyclohexane is fed to the reactor (1) of the reactor unit (24) in an amount in the range of 100 to 600% by weight, preferably in the range of 200 to 500% by weight, particularly preferably in the range of 350 to 450% by weight, based on the amounts by mass of 2-octanol (13) and (meth) acrylic acid (14) fed to the reactor (1) of the reactor unit (24).

14. The process according to any of the preceding claims, wherein the proportion of catalyst in the reactor (1) of the reactor unit (24) is at maximum 10% by weight, based on the sum of the components of 2-octanol and (meth)acrylic acid present in the reactor (1) of the reactor unit (24).

15. The process according to any of the preceding claims, wherein the components flowing into the reactor (1) of the reactor unit (24) without the azeotroping agent cyclohexane have the following proportions by weight: • 2-octanol: 40.00% to 84.39% by weight • (meth)acrylic acid: 15.00% to 59.39% by weight • acidic esterification catalyst: 0.50% to 10.00% by weight • polymerization inhibitor: 0.01% to 1.00% by weight • residual components: 0.10% to 5.00% by weight, and the azeotroping agent cyclohexane is added in an amount such that a concentration of cyclohexane forms in the reactor (1) of the reactor unit (24) in the range of 10 to 90% by weight, where these figures of the percentage by weight relate to the components present in the reactor (1) of the reactor unit (24) including the cyclohexane, and / or without the azeotroping agent cyclohexane and without the water of esterification, the total components flowing out of the reactor (1) of the reactor unit (24), namely the resulting liquid reaction discharge plus the portion evaporated from the reaction mixture and discharged from the reactor unit (24) have the following proportions by weight: • 2-octyl (meth)acrylate: 50.00% to 95.00% by weight • 2-octanol: 1.00% to 30.00% by weight • (meth)acrylic acid: 1.00% to 15.00% by weight • acidic esterification catalyst: 0.50% to 10.00% by weight • polymerization inhibitor: 0.01% to 1.00% by weight • residual components: 2.49% to 10.00% by weight, and the heterogeneous azeotrope formed by the cyclohexane and the water of esterification flows out of the reactor (1) of the reactor unit (24) at a concentration in the range of 10 to 50% by weight, where these figures of the percentage by weight relate to the total components flowing out including the cyclohexane and the water of esterification.