Manufacturing method of 2-octyl (meth)acrylate

Abstract

The present invention relates to a method 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 an azeotropic 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), an acidic esterification catalyst (15), cyclohexane (17) and a polymerization inhibitor (31) into a reactor (1); carrying out esterification in a reactor (1) to form a liquid reaction mixture, the esterification in the reactor (1) being carried out at a bottom temperature in the range of from 90 to 130° C. and at an absolute pressure in the range of from 0.5 to 2.0 bar; A reaction effluent obtained from the reactor (1) is obtained, the resulting reaction effluent comprises at least 2-octyl (meth)acrylate, 2-octanol, (meth)acrylic acid, an acidic esterification catalyst, cyclohexane, esterification water, and a polymerization inhibitor, and the esterification water formed in the esterification forms a heterogeneous azeotrope with the cyclohexane azeotroping agent; evaporating a heterogeneous azeotrope from the liquid reaction mixture in the reactor (1), the evaporation being accomplished by a reactor heating element (30); Removing the gas heterogeneous azeotrope from the reactor (1), comprising: the gas heterogeneous azeotrope is condensed in a condenser (5) and then fed to a phase separator (6) in which the esterification water is separated as a lower phase and the cyclohexane is separated as an upper phase; The present invention relates to a method comprising the steps of:

Description

[Technical field]

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

[0002] In this specification, (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 homomonomer and comonomer in radical, cationic and anionic polymerization, as well as complex catalyzed polymerization. It is suitable for use in both emulsion and solvent-based or bulk polymerization.

[0004] Important applications are e.g. decorative or industrial 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 oils and lubricants, printing inks or reactive thinners for UV curing resins and systems. [Background technology]

[0005] Known methods for the industrial-scale production of 2-octyl (meth)acrylate are mainly based on the transesterification between (meth)acrylates of low-carbon alcohols and 2-octanol in the presence of an alkyl titanate as a transesterification catalyst and at least one polymerization inhibitor. Such a method is disclosed in WO 2013 / 110877 (Arkema France). A drawback of the transesterification method is the generation of low-boiling (meth)acrylates and alcohols of low-boiling (meth)acrylates, such as, but not limited to, azeotropes of methanol / methyl methacrylate or ethanol / ethyl acrylate, which must be painstakingly treated or disposed of.

[0006] WO 2013 / 064775 (Arkema France) discloses a process for direct esterification to 2-octyl acrylate. The valuable 2-octyl acrylate product is obtained by direct esterification of acrylic acid with 2-octanol in the presence of a catalyst and a polymerization inhibitor, and the esterification water formed by the esterification forms a heterogeneous azeotrope with 2-octanol and is separated by distillation in a distillation column attached to the reactor. In this case, the reactor is equipped with an agitator and an external heat exchanger. In a downstream purification step, the catalyst is at least partially recycled to the reactor and the valuable 2-octyl acrylate product is separated.

[0007] WO 2008 / 046000 (3M Innovative Properties Company, USA) discloses another process for direct esterification to 2-octyl acrylate. The valuable 2-octyl acrylate product is obtained by direct esterification of acrylic acid with 2-octanol in the presence of the catalyst p-toluenesulfonic acid, the polymerization inhibitor phenothiazine and the azeotropic agent toluene, and the esterification water formed by the esterification forms a heterogeneous azeotrope with the toluene azeotropic agent, which is separated by distillation in a Dean-Stark distillation column attached to the reactor. [Prior art documents] [Patent documents]

[0008] [Patent Document 1] International Publication No. 2013 / 110877 [Patent Document 2] International Publication No. 2013 / 064775 [Patent Document 3] International Publication No. 2008 / 046000 Summary of the Invention [Problem to be solved by the invention]

[0009] The two above-mentioned processes for the direct esterification to 2-octyl acrylate have the particular disadvantage that a high energy input is required, since the esterification water formed during the esterification must be removed from the reactor by evaporation in order to be able to separate it in a distillation column attached to the reactor. Thus, not only must the high boiling point of the water or the high boiling point of the heterogeneous azeotrope "water of esterification with toluene and / or with excess 2-octanol" be reached at the bottom of the reactor (1), but it must also be exceeded in order to be able to reach the required boiling temperature at the top of the distillation column.

[0010] The object was therefore to provide a process for producing 2-octyl (meth)acrylate that does not require the use of complex equipment and can be operated at lower energy input, lower bottom temperatures in the reactor and at moderate pressures, e.g. standard pressure. Furthermore, this process should achieve a better space-time yield with the same energy usage than the known processes from the prior art mentioned above. [Means for solving the problem]

[0011] This object is achieved according to the invention by a process for the preparation of 2-octyl(meth)acrylate according to claim 1. Advantageous embodiments of the process are presented in claims 2 to 15.

[0012] The process according to the invention for preparing 2-octyl (meth)acrylate by reacting 2-octanol and (meth)acrylic acid in the presence of an acidic esterification catalyst, a polymerization inhibitor and the azeotropic agent cyclohexane comprises: 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, (meth)acrylic acid, an acidic esterification catalyst, cyclohexane and a polymerization inhibitor into one reactor (1); carrying out esterification in one reactor (1) to form a liquid reaction mixture, the esterification in the one reactor (1) being carried out at a bottom temperature in the range of 90-130°C and an absolute pressure in the range of 0.5-2.0 bar, and a reaction effluent obtained from the one reactor (1) is obtained, the reaction effluent obtained comprising at least 2-octyl (meth)acrylate, 2-octanol, (meth)acrylic acid, an acidic esterification catalyst, cyclohexane, esterification water and a polymerization inhibitor, the esterification water formed in the esterification forming a heterogeneous azeotrope with the cyclohexane azeotroping agent; evaporating a heterogeneous azeotrope from the liquid reaction mixture in the reactor (1), the evaporation being accomplished by a reactor heating element (30); Removing the gas heterogeneous azeotrope from the reactor (1), comprising: the gas heterogeneous azeotrope is condensed in a condenser (5) and then fed to a phase separator (6) in which the esterification water is separated as a lower phase and the cyclohexane is separated as an upper phase; Includes.

[0013] In this document, reference numbers in parentheses provide a better understanding upon reading. They are not limiting and represent only one possible example of several possibilities for implementation.

[0014] In the following, the individual process steps I to VII are described, process steps II to VII should be considered as optional.

[0015] Process Step I: Esterification The process according to the invention is based on the reactants 2-octanol and (meth)acrylic acid. In this specification, (meth)acrylic acid is used to refer to a grade of (meth)acrylic acid having preferably at least 98% by weight, more preferably at least 99.5% by weight of (meth)acrylic acid, even more preferably at most 0.2% by weight of water, and also preferably at most 0.03% of acetic acid, propionic acid and isobutyric acid, respectively. Preferably, a grade of 2-octanol is used having at least 99% by weight of 2-octanol, at most 0.1% of 2-octanone, at most 0.3% of 1-heptanol, at most 0.3% of octenol (cis / trans), at most 0.1% of other alcohols and at most 0.5% of water. The color number is preferably at most APHA 15 and the acid number at most 0.2 mgKOH / g.

[0016] Suitable polymerization inhibitors acting as stabilizers are, for example, N-oxides (nitroxyl or N-oxyl radicals, i.e. compounds having at least one NO group), such as 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-tetramethylpiperidin-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, optionally having one or more alkyl groups, such as alkylphenols, for example o-, m- or p-cresol (methylphenol), 2-tert-butylphenol, 4-tert-butyl Phenol, 2,4-di-tert-butylphenol, 2-methyl-4-tert-butylphenol, 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 hydroquinone, hydroquinone monomethyl ether, 2-methylhydroquinone or 2,5-di-tert-butylhydroquinone; hydroxyphenols such as catechol (1,2-dihydroxybenzene) or benzoquinone; aminophenols such as p-aminophenol; nitrosophenols such as p-nitrosophenol; alkoxyphenols such as 2-methoxyphenol (guaiacol, catechol 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 N,N-diphenylamine or N-nitrosodiphenylamine; phenylenediamines such as N,N'-dialkyl-p-phenylenediamines (wherein the alkyl groups may be the same or different, each independently have 1 to 4 carbon atoms, and may be linear or branched), such as N,N'-dimethyl-p-phenylenediamine or N,N'-diethyl-p-phenylenediamine, hydroxylamines such as N,N-diethylhydroxylamine, imines such as methylethylimine or methylene violet, N-methyl-4-toluenesulfonyl amine, etc. sulfonamides such as ketoximes such as diethylketoxime, methylethylketoxime or salicylaldoxime, phosphorus-containing compounds such as triphenylphosphine, triphenylphosphite, triethylphosphite, hypophosphorous acid or alkyl esters of phosphorous acid; sulfur-containing compounds such as diphenylsulfide, phenothiazine; metal salts such as copper or manganese, cerium, nickel and chromium salts, for example chlorides, sulfates, salicylates, tosylates, acrylates or acetates, for example copper acetate, copper chloride(ll), copper salicylate, cerium acetate(ll) or cerium ethylhexanoate(ll), or mixtures thereof;

[0017] As polymerization inhibitor or polymerization inhibitor mixture it is preferable to use at least one compound from the group comprising 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-tetramethylpiperidin-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.

[0018] Particular preference is given to using phenothiazine (PTZ) and / or hydroquinone monomethyl ether (MEHQ) as polymerization inhibitors.

[0019] PTZ is particularly preferably used as a polymerization inhibitor in the case of esterification or in the case of the optional use of an azeotrope rectifier unit (25). In the case of the optional downstream process steps, PTZ is also particularly preferably used for cyclohexane separation IV and / or 2-octanol separation V.

[0020] In very particular, MEHQ is used as a polymerization inhibitor in optional downstream process steps in pure boiler separation VI and / or high boiler separation VII.

[0021] The polymerization inhibitor is preferably dissolved in one or more liquid organic compounds, preferably 2-octanol and / or 2-octyl (meth)acrylate.

[0022] Suitable as esterification catalysts are the common mineral 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, but acidic ion exchangers or zeolites may also be used. Particular preference is given to sulfuric acid, methanesulfonic acid, p-toluenesulfonic acid, m-toluenesulfonic acid, o-toluenesulfonic acid or mixtures thereof.

[0023] As the esterification catalyst, methanesulfonic acid is particularly preferably used.

[0024] In the process according to the invention, the reactants (meth)acrylic acid and 2-octanol and the entrainer cyclohexane are fed continuously or discontinuously to one reactor (1) of the reactor unit (24), with continuous feeding being preferred.

[0025] In the process according to the invention, cyclohexane is used as the azeotropic agent. It has a boiling point of 81° C. at standard pressure. Cyclohexane forms a heterogeneous azeotrope with esterified water, which has a boiling point of only 70° C. at standard pressure. Due to its boiling point of 70° C., the heterogeneous azeotrope has a lower boiling point than pure water or other azeotropes, such as 2-octanol and esterified water, toluene and esterified water or octene and esterified water. Therefore, when cyclohexane is used, less energy is required to evaporate the heterogeneous azeotrope.

[0026] It has been recognized that by feeding an optimal amount of cyclohexane azeotropic agent to one reactor (1) of the reactor unit (24) than with another azeotropic agent or a non-optimal amount of cyclohexane, a lower bottom temperature can be set, whereby fewer secondary components are formed and at the same time, in addition to the gas heterogeneous azeotrope, the gas stream is as pure as possible and therefore contains as few other components as possible, such as, for example, (meth)acrylic acid. The bottom temperature required to evaporate the esterification water can therefore also be greatly influenced by the amount of azeotropic agent used.

[0027] Lower bottom temperatures, among others, reduce the formation of secondary components such as octenes, especially 1-octene and 2-octene. Octene itself also acts as an azeotrope, but has a significantly higher boiling point than 2-octanol. For example, 1-octene has a boiling point of 121° C. at standard pressure. The formed secondary components also increase the separation problems of separating the heterogeneous azeotrope from the reaction mixture and in pure distillation.

[0028] Surprisingly, it was found that when the same azeotropic agent concentration is used and other conditions are the same, e.g., based on feed temperature, reaction time and molar ratio, the use of the other azeotropic agents toluene and 2-octanol in excess or no azeotropic agent, the use of cyclohexane results in a higher conversion but much less secondary products are formed, the bottom temperature is not significantly different when using cyclohexane, but still the highest bottom temperature at the end of the process.

[0029] Without the use of an azeotropic agent, a lot of water remains at the bottom. In order to effectively remove the water, the process must be operated under vacuum conditions. However, the process under vacuum is very complicated, and the operating and construction costs of the plant for the process are high.

[0030] The lower boiling point of the heterogeneous azeotrope in the single reactor (1) also results in less (meth)acrylic acid vaporizing in the single reactor (1) and / or the reactor heating element (30), which enhances the separation performance of the heterogeneous azeotrope from the reaction mixture.

[0031] In this document, "reaction mixture" defines the liquid mixture formed during the esterification in one reactor (1) and thus also containing the product value of 2-octyl (meth)acrylate.

[0032] 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 and the azeotropic agent cyclohexane. The starting mixture becomes the reaction mixture by esterification.

[0033] In this specification, the bottom temperature includes the temperature range of 90 to 130° C. By varying the bottom temperature within this range, it is possible to affect the reaction rate, yield / conversion, selectivity and / or formation of secondary components, etc.

[0034] In this specification, the term "reactor bottom" is understood to mean the liquid mixture below the gaseous mixture phase in the reactor (1). The reactor (1) is therefore only partially filled with the liquid mixture, since part of the liquid mixture, preferably a heterogeneous azeotrope, also evaporates during the esterification, thereby filling the reactor space above the liquid mixture.

[0035] In this specification, the term "rectification tower unit" defines one or more rectification towers which may also include further standard components such as pressure reducers, flow regulators or sensors. Thus, the rectification tower unit also includes its control. In the case of two or more rectification towers, these may be connected to each other in series or in parallel.

[0036] The rectification column is of a design known per se and is equipped with the usual devices such as a bottom evaporator, an evaporator at the high boiler outlet or a condenser at the low boiler outlet, whereby the high boiler is preferably located in the bottom region and the low boiler is preferably located in the upper region of the rectification column. A part of the mass flow at the high boiler outlet is usually returned to the bottom region of the rectification column. However, in principle it is also possible to heat the bottom region, for example via outer wall heating of the column in the bottom region, and / or to integrate an evaporator in the bottom region.

[0037] Typically, after condensation in the condenser, the mass flow of the low boiler outlet is returned to the top region of the fractionator in the weight range of 10-200%.

[0038] The column internals used may in principle be all target subinternals, such as trays, structured packings and / or random packings. Among trays, bubble cap trays, sieve trays, valve trays, Thormann trays and / or dual flow trays are preferred. Among random packings, those with rings, spirals, saddles or blades are preferred.

[0039] As used herein, components are referred to as low-boilers if their boiling point at standard pressure is lower than the boiling point of 2-octyl acrylate. Similarly, components are referred to as high-boilers if their boiling point at standard pressure is equal to or higher than the boiling point of 2-octyl acrylate, which has a boiling point of 211° C. at standard pressure.

[0040] As used herein, the term "reactor with reactor heating element" generally defines a reactor (1) in 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 can be, for example, an immersion heater in the reactor (1), a tubing system including coiled or semi-coiled tubing arranged on the outer jacket surface of the reactor (1) and / or inside the reactor (1), an electric heating system arranged on the outer jacket surface of the reactor (1) and / or inside the reactor (1), an evaporator located outside the reactor (1), where the reaction mixture flows at least partially through the evaporator, or a double-wall design of the reactor outer wall, whereby fluids separated from the reaction mixture, such as liquid, gas and / or heating steam, are temperature controlled, whereby a predetermined heating temperature is set, whereby the reaction mixture is heated in the reactor (1). Two or more reactor heating elements can generally be used to heat the reaction mixture in the reactor (1). For example, the reaction mixture can be heated simultaneously or at least partially offset in time using a double-wall design of the reactor outer wall and an evaporator located outside the reactor (1).

[0041] In this specification, the term "evaporator" is also understood to mean a reactor heating element (30). The evaporator may also include further standard components, such as control valves, pressure reducers, flow regulators or sensors. Thus, the evaporator may also include closed loop control. The term "evaporator" may also be generally understood to mean two or more evaporators connected in series or parallel.

[0042] Examples of suitable evaporators are thin layer, falling film, natural and forced circulation evaporators. The evaporator can be designed as a shell-and-tube heat exchanger or a plate heat exchanger. Suitable evaporators are known to those skilled in the art and are described, inter alia, in SPX, Evaporator Handbook, APV, available at https: / / userpages.umbc.edu / ~dfrey1 / ench445 / apv_evap.pdf (retrieved 11.1.2021).

[0043] In this specification, the term "reactor unit" defines one or more reactors that may also include further standard components, such as pressure reducers, flow regulators, reactor heating elements, other heating elements, conduits, heat exchangers or evaporators. The reactor unit (24) may also include control valves and / or sensors. Thus, the reactor unit (24) may also include process control. Of course, it is also possible that there are more than one heat exchanger per reactor or more than one heat exchanger combined for all reactors of the reactor unit (24).

[0044] In a more preferred configuration, in the case of two or more reactors, the reactors are interconnected in parallel with each other.

[0045] In a preferred configuration, the reactor unit (24) comprises two or more reactors interconnected in series with each other, thus allowing a cascade of two or more reactors connected in series, where cascade means that the discharge stream of one reactor forms the feed stream to the downstream reactor.

[0046] In a preferred configuration of the cascade, the components for the esterification are fed only to the first reactor (1) and only the reaction discharge resulting from the esterification is fed to the subsequent reactor in each case.

[0047] In a preferred configuration, one reactor (1) is equipped with internal or external heating coils and / or a double-wall design of the reactor exterior.

[0048] In a preferred configuration, one reactor (1) is equipped with an external evaporator, internal or external heating coils, and / or a double-wall design of the reactor exterior.

[0049] In a preferred configuration, one reactor (1) is equipped with an external evaporator and a double-wall design of the reactor outer wall.

[0050] In a preferred configuration, one reactor (1) is equipped with an external evaporator and internal and / or external heating coils.

[0051] In a preferred configuration, one reactor (1) is equipped with an external heat exchanger and / or an evaporator.

[0052] In a preferred embodiment, one reactor (1) is equipped with an evaporator. In the case of more than one reactor, each individual reactor is equipped with its own evaporator.

[0053] In a further embodiment, the reactor unit (24) comprises an evaporator to which all reactors of the reactor unit (24) are connected.

[0054] In a preferred embodiment, one reactor (1) is operated by natural circulation. This has the advantage, among other things, that the reactor equipment is cheaper to obtain, since no stirrer or other mechanical assistance is required. The cyclohexane azeotrope ensures increased mixing.

[0055] In a preferred embodiment, the esterification is operated continuously, the reactants and cyclohexane azeotrope agent are fed continuously, and the evaporator unit is also operated continuously.

[0056] In a further embodiment, the esterification is operated discontinuously and the reactants and cyclohexane azeotroping agent are fed discontinuously.

[0057] In a preferred embodiment of the process, the gas heterogeneous azeotrope is fed to an azeotrope rectifier unit (25) downstream of the reactor unit (24), and an azeotrope rectifier (4) is located in the azeotrope rectifier unit (25), one azeotrope rectifier (4) is operated at an absolute pressure in the range of 0.5 to 2.0 bar and a bottom temperature in the range of 90 to 130° C., the heterogeneous azeotrope is removed via the top of the one azeotrope rectifier (4), condensed in a condenser and then fed to a phase separator (6), and the esterification water is separated as a lower phase in the phase separator (6) and cyclohexane is separated as an upper phase in the phase separator (6).

[0058] In a further configuration, in the case of more than one reactor, each individual reactor includes an azeotrope rectifier unit (25) located thereon.

[0059] In a further configuration, in case of two or more reactors, each individual reactor is provided with one azeotrope rectifier unit (25) located thereon, the azeotrope rectifier unit (25) preferably comprising exactly one azeotrope rectifier (4).

[0060] In a particularly preferred configuration, one azeotrope rectifier unit (25) is placed over the reactor unit (24), which preferably comprises exactly one azeotrope rectifier (4). This has the advantage that only one azeotrope rectifier (4) has to be operated for the or all reactors, and therefore the process is energy- and cost-efficient.

[0061] In a preferred embodiment having more than one reactor, the rising vapors from all the reactors are fed to a single azeotrope rectifier (4) and the liquid discharge of the azeotrope rectifier (4) is only returned to the first reactor (1). The azeotrope rectifier unit (25) preferably comprises only one azeotrope rectifier.

[0062] In a preferred embodiment, the azeotrope rectifier unit (25) is operated continuously.

[0063] 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).

[0064] In a preferred configuration, the cyclohexane obtained as the upper phase in the phase separator (6) is recycled to the reactor unit (24) in a proportion by weight in the range of 40-100% by weight, preferably in the range of 50-99.9% by weight, and the remaining proportion of the obtained cyclohexane is fed below the top to the central region of one azeotrope rectification column (4).

[0065] This has the advantage that the proportion of azeotropic agent in the reactor unit (24) and / or in the azeotrope rectifier unit (25) can be adjusted so that the water of esterification can be efficiently separated or even a specific adjustment of the bottom temperature can be made by feeding cyclohexane to the reactor (1).

[0066] In a preferred embodiment, the phase separator (6) is operated continuously with continuous inflow and outflow streams.

[0067] Process Step II: Alkaline Extraction In a preferred configuration, following the esterification, an alkaline extraction of the resulting reaction effluent is carried out with an alkaline solution, in particular the acidic esterification catalyst and the unreacted (meth)acrylic acid are neutralized in a neutralization extraction unit (7), resulting in an upper neutralization phase containing 2-octyl (meth)acrylate and a lower neutralization phase containing the salts produced by the neutralization and water, so that these two phases are present separately from each other. The two neutralization phases are preferably produced by a dispersion device, for example a mixing pump, and then separated from each other in a phase separator (6) located in the neutralization extraction unit (7).

[0068] In a preferred embodiment, the neutralization extraction unit (7) is operated continuously with continuous inflow and outflow streams.

[0069] Process Step III: Water Extraction In a preferred configuration, following the alkaline extraction of the reaction effluent, the upper neutralized phase obtained from the neutralization extraction unit (7) is extracted with water in the water washing extraction unit (8) to form a lower water washing phase containing water and salt residues and an upper water washing phase containing 2-octyl (meth)acrylate, these two phases therefore being present separately from each other. The two water washing phases are preferably generated by a dispersing device, e.g. a mixing pump, and then separated from each other in a phase separator (6) located in the water washing extraction unit (8).

[0070] 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 in another conventional apparatus, for example a tower or mixer-settler apparatus. In a mixer-settler or tower, the appropriate process is preferably carried out continuously. In a stirred tank, the appropriate process is preferably carried out discontinuously.

[0071] There are different dispersion options in mixer-settler devices, such as dispersion in a stirred tank, in a static mixer, in a pipeline, or in a mixing pump and phase separator.

[0072] The mixer and settler can be constructed more or less independently of each other. The mixing process can be adjusted, for example, by the correct selection of the agitator, the agitation speed, the power input and / or the throughput. In the case of a mixing pump, the power input can preferably be adjusted.

[0073] Both the alkaline extraction (process stage II) and the water-wash extraction (process stage III) may preferably be in an extraction column, a centrifugal extractor or a mixer-settler apparatus.

[0074] In a particularly preferred embodiment, in the case of the alkaline extraction (process stage II), the reaction effluent obtained is dispersed with dilute alkali by means of a pump, for example a mixing pump, and then fed to a phase separator (6) which separates the upper and lower neutralized phases from each other.

[0075] The process techniques used can be all extraction and washing methods and extraction apparatuses known per se, such as those described in Ullmann's Encyclopedia of Industrial Chemistry, 6th edition, 1999 Electronic Release, Chapter: Liquid-Liquid Extraction-Apparatus. For example, they can be single or multi-stage extractions, preferably single-stage extractions, which can be operated in cocurrent or countercurrent mode.

[0076] When separating salts, it is preferred to use a water wash.

[0077] In a preferred embodiment, the water washing extraction unit (8) is operated continuously with continuous inflow and outflow streams.

[0078] In a particularly preferred embodiment, a static mixer is used to disperse the upper neutralized phase obtained from the neutralization extraction unit (7) with separately fed water. The mixture dispersed by the static mixer is then fed to a phase separator (6) where a lower water wash phase containing water and salt residues and an upper water wash phase containing 2-octyl (meth)acrylate are formed.

[0079] The following process steps IV to VII are preferably operated continuously.

[0080] Process Step IV: Cyclohexane Removal In a preferred configuration, following the alkaline extraction of the reaction effluent, the cyclohexane azeotropic agent is separated from the upper neutral phase in an azeotrope rectification column unit, an azeotrope rectification column (9) is located in the azeotrope rectification column unit, one azeotrope rectification column (9) is operated under 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 withdrawn via the top of one azeotrope rectification column (9) containing the azeotropic agent cyclohexane, octene, 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 neutral phase fed, withdrawn via the top. The components form an azeotropic mass stream which is condensed and fed to one reactor (1) of the reactor unit (24) in the range of 50-100%, the remaining azeotrope mass flow proportion is condensed and fed to the top of the azeotrope rectification column (9), while the high boiler containing di(meth)acrylic esters and oxyesters, for example alkoxyalkyl esters of (meth)acrylic acid, as well as 2-octanol and 2-octyl (meth)acrylate, is removed through the bottom discharge of one azeotrope rectification column (9) and in the range of 20-95% of the mass flow of the bottom discharge flows through an evaporator and is subsequently recycled to one azeotrope rectification column (9).

[0081] In a preferred configuration, following the water wash extraction, the cyclohexane azeotropic agent is separated from the upper water wash phase in an azeotrope rectifier unit, an azeotrope rectifier (9) is located in the azeotrope rectifier unit, one azeotrope rectifier (9) is operated under 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., an organic phase is withdrawn via the top of one azeotrope rectifier (9) containing the azeotropic agents cyclohexane, octene, 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 water wash phase fed, and the components withdrawn via the top An azeotropic mass flow is formed, which is condensed and fed to one reactor (1) of the reactor units (24) in the range of 50-100% by weight, the remaining azeotrope mass flow proportion is condensed and returned to the top of the azeotrope rectification column (9), while a high boiler containing di(meth)acrylic esters and oxyesters, such as alkoxyalkyl esters of (meth)acrylic acid, as well as 2-octanol and 2-octyl (meth)acrylate, is removed through the bottom discharge of one azeotrope rectification column (9) and, in the range of 20-95% of the mass flow of the bottom discharge, flows through an evaporator and then recycled to one azeotrope rectification column (9).

[0082] In a particularly preferred configuration, exactly one azeotrope rectifier (9) is located within the azeotrope rectifier unit.

[0083] Process Step V: 2-Octanol Separation In a particularly preferred configuration, following separation of the cyclohexane azeotropic agent, 2-octanol is separated from the mass stream produced by the bottom discharge of one azeotrope rectifier (9) in the 2-octanol rectifier unit, a 2-octanol rectifier (10) being located in the 2-octanol rectifier unit, the one 2-octanol rectifier (10) being operated under 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. The mass flow generated by the bottom discharge of one azeotrope rectification column (9) is metered in the central region below the top of the 2-octanol rectification column (10), and the components discharged through the top of the one 2-octanol rectification column (10) are condensed and fed to one reactor (1) of the reactor unit (24) in the range of 20-50% based on the mass flow of the components discharged through the top, and the discharge components consist of 2-octanol in the range of 2-40% by weight. Meanwhile, a high boiler containing 2-octyl (meth)acrylate and di(meth)acrylic acid esters and oxyesters is extracted from the bottom discharge of the 2-octanol rectification column (10), and 20-95% of the mass flow of the bottom discharge flows through an evaporator and is then returned to the one 2-octanol rectification column (10).

[0084] In a preferred configuration, following the separation of the cyclohexane azeotropic agent, 2-octanol is separated from the mass stream produced by the bottom discharge of one azeotrope rectification column (9) in a 2-octanol evaporator unit, a 2-octanol evaporator (110) is located in the 2-octanol evaporator unit, the one 2-octanol evaporator (110) is operated under 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 generated by the bottom discharge of one azeotrope rectification column (9) is metered into the 2-octanol inlet of one 2-octanol evaporator, and the components discharged through the 2-octanol evaporator (110) outlet of one 2-octanol evaporator are fed to the reactor unit (24) in the range of 20-50%, and based on the mass flow of the components discharged at the 2-octanol evaporator outlet, these discharge components consist of 2-octanol in the range of 2-40% by weight. Meanwhile, the high boiler containing 2-octyl (meth)acrylate and di(meth)acrylic acid esters and oxyesters is withdrawn through the bottom discharge of one 2-octanol evaporator, and in the range of 20-95% of the mass flow of the bottom discharge flows through the evaporator and subsequently returned to one 2-octanol evaporator (110).

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

[0086] In a preferred configuration, the dividing wall column (131) is provided with a vertical dividing wall (138) which prevents cross-mixing of the liquid and vapor streams in the sub-regions. The dividing wall (138) is made of a flat metal sheet and divides the column longitudinally in its central region into a feed section (140) and a withdrawal section (141).

[0087] In a preferred configuration, the mixture to be separated, including low boiler, 2-octyl (meth)acrylate and high boiler, 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 boiler is separated via the top of the dividing wall column (131) and the high boiler is separated via the bottom of the dividing wall column (131).

[0088] The energy requirements and investment costs are approximately 25% lower than in a conventional column arrangement with two fractionators.

[0089] Process Step VI: Pure Boiler Separation (separation of the target product 2-octyl (meth)acrylate) In a preferred configuration, the separation of 2-octanol is followed by a pure boiler separation from a mass stream generated by the bottom discharge of one 2-octanol rectifier (10) in a pure boiler rectifier unit, a pure boiler rectifier (11) is located in the pure boiler rectifier unit, the one pure boiler rectifier (11) is operated under a reduced absolute pressure in the range of 0.002-0.05 bar and at a bottom temperature in the range of 80-130° C., the mass stream generated by the bottom discharge of the one 2-octanol rectifier (10) is metered in the region below the top to the middle of the one pure boiler rectifier (11), and the one pure boiler rectifier (11) is separated from the mass stream generated by the bottom discharge of the one 2-octanol rectifier (10) in a pure boiler rectifier unit. In order to stabilize the distillation column (11), 2-octyl (meth)acrylate and a polymerization inhibitor are metered into the region from the bottom to the middle of the one pure boiler rectification column (11) in the range of 0.01-1.0%, respectively, based on the mass flow generated by the bottom discharge of the one 2-octanol rectification column (10), and 2-octyl (meth)acrylate is withdrawn via the top of the one pure boiler rectification column (11), while the high boiler containing di(meth)acrylic acid esters and oxyesters, for example alkoxyalkyl esters of (meth)acrylic acid, is withdrawn via the bottom discharge of the one pure boiler rectification column (11).

[0090] In a particularly preferred configuration, the separation of 2-octanol is followed by a pure boiler separation from a mass flow generated by the bottom discharge of one 2-octanol evaporator in a pure boiler evaporator unit, in which a pure boiler evaporator is located, one pure boiler evaporator (111) is operated under a reduced absolute pressure in the range of 0.002-0.05 bar and at a bottom temperature in the range of 80-130° C., and the mass flow generated by the bottom discharge of one 2-octanol rectification column (10) or one 2-octanol evaporator is metered into the pure boiler evaporator inlet of one pure boiler evaporator unit, In order to stabilize one pure boiler evaporator, 2-octyl (meth)acrylate and polymerization inhibitor are metered into the pure boiler evaporator inlet of one pure boiler evaporator, each in the range of 0.01 to 1.0%, based on the mass flow generated by the bottom discharge of one 2-octanol evaporator, and 2-octyl (meth)acrylate is withdrawn through the pure boiler evaporator outlet of one pure boiler evaporator, while a high boiler containing di(meth)acrylic acid esters and oxyesters, for example, alkoxyalkyl esters of (meth)acrylic acid, is withdrawn through the bottom discharge of one pure boiler evaporator.

[0091] In a very particularly preferred configuration, the pure boiler-evaporator unit comprises exactly one pure boiler-evaporator.

[0092] Process Step VII: High Boiler Separation (Di(meth)acrylic acid esters and oxyesters, e.g., alkoxyalkyl esters of (meth)acrylic acid)

[0093] In a preferred configuration, following the pure boiler separation, in a high boiler rectifier unit, the high boiler is separated from the mass flow generated by the bottom discharge of the one pure boiler rectifier (11) or the one pure boiler evaporator, a high boiler rectifier (12) is located in the high boiler rectifier unit, the one high boiler rectifier (12) is operated under a reduced absolute pressure in the range of 0.002-0.05 bar and at a bottom temperature in the range of 80-150°C, the mass flow generated by the bottom discharge of the one pure boiler rectifier (11) is metered into the bottom-to-middle region of the one high boiler rectifier (12), and the draw withdrawn via the top of the one high boiler rectifier (12) is condensed and fed to the bottom-to-middle region of the one pure boiler rectifier (11) or to the pure boiler evaporator inlet of the one pure boiler evaporator.

[0094] In a particularly preferred configuration, following the pure boiler separation, the high boiler is separated from the mass flow generated by the bottom discharge of the one pure boiler rectifier (11) or the one pure boiler evaporator in a high boiler evaporator unit, the high boiler evaporator is located in the high boiler evaporator unit, the one high boiler evaporator is operated under a reduced absolute pressure in the range of 0.002-0.05 bar and at a bottom temperature in the range of 80-150 ° C, the mass flow generated by the bottom discharge of the one pure boiler evaporator is metered to the high boiler evaporator inlet of the one high boiler evaporator, and the draw off from the one high boiler evaporator is condensed and returned to the bottom-to-middle region of the one pure boiler rectifier (11) or to the pure boiler evaporator inlet of the one pure boiler evaporator.

[0095] In a very particularly preferred configuration the high boiler evaporator unit comprises exactly one high boiler evaporator.

[0096] Further preferred embodiments of process steps I and II In a preferred configuration, the bottom temperature in one reactor (1) of the reactor unit (24) is in the range of 100-125°C, preferably 110-115°C.

[0097] In a preferred configuration, the esterification is carried out at a pressure ranging from 0.8 to 1.5 bar absolute, particularly preferably from 0.9 to 1.2 bar.

[0098] In a preferred configuration, less than 1.0% octene is 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 inhibitor (31) and (meth)acrylic acid (14) fed to the reactor (1). This can be achieved, inter alia, when applying the configurations from the previous two paragraphs.

[0099] In a preferred configuration, cyclohexane is fed to one reactor (1) of the reactor unit (24) in an amount in the range from 100 to 600% by weight, preferably in the range from 200 to 500% by weight and particularly preferably in the range from 350 to 450% by weight, based on the sum of the amounts by weight of 2-octanol (13) and (meth)acrylic acid (14) fed in each case to one reactor (1) of the reactor unit (24).

[0100] In a preferred configuration, cyclohexane in a concentration ranging from 10 to 90 wt. % is further metered into one reactor (1) of the reactor unit (24), the weight percentage of the concentration referring to the component present in the one reactor (1) of the reactor unit (24) including the metered cyclohexane.

[0101] In a preferred configuration, the proportion of catalyst in one reactor (1) of the reactor unit (24) is at most 10% by weight, based on the sum of the components 2-octanol and (meth)acrylic acid present in one reactor (1) of the reactor unit (24).

[0102] In a preferred configuration, the alkaline solution in process step (II) is an aqueous NaOH solution containing NaOH in the range of 5-25% by weight, preferably 10-20% by weight.

[0103] In a preferred configuration, the reactor contents are circulated within one reactor (1) by natural or forced circulation.

[0104] In a preferred configuration, the total components entering one reactor (1) of the reactor unit (24) without cyclohexane azeotroping agent 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 component: 0.10~5.00% by weight.

[0105] The entrainer cyclohexane is added in such an amount that a concentration of cyclohexane is formed in the reactor (1) of the reactor unit (24) in the range of 10 to 90% by weight, these figures of percentages by weight relating to the components present in the reactor (1) of the reactor unit (24) that contain cyclohexane.

[0106] Furthermore, in this preferred configuration, free of the entrainer cyclohexane and free of esterification water, all components leaving the reactor (1) of the reactor unit (24), i.e. the resulting liquid reaction effluent plus the portion evaporated from the reaction mixture leaving 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 component: 2.49~10.00% by weight.

[0107] The heterogeneous azeotrope formed by cyclohexane and water of esterification exits reactor (1) of reactor unit (24) in concentrations ranging from 10 to 50% by weight, these figures in weight percent referring to all components exiting, including cyclohexane and water of esterification.

[0108] In a particularly preferred configuration, the total components entering one reactor (1) of the reactor unit (24) without cyclohexane azeotroping agent have the following proportions by weight: 2-Octanol: 50.00 to 74.39% by weight (Meth)acrylic acid: 25.00 to 45.00% by weight Acidic esterification catalyst: 0.50 to 5.00% by weight Polymerization inhibitor: 0.01 to 1.00% by weight Residual ingredients: 0.10~2.00% by weight.

[0109] The entrainer cyclohexane is added in such an amount that a concentration of cyclohexane is formed in the reactor (1) of the reactor unit (24) in the range of 10 to 50% by weight, these figures of proportion by weight relating to the components present in the reactor (1) of the reactor unit (24) that contain cyclohexane.

[0110] Moreover, in this particularly preferred configuration without entrainer cyclohexane and without esterification water, all components leaving one reactor (1) of the reactor unit (24), i.e. the resulting liquid reaction effluent plus the portion evaporated from the reaction mixture leaving the reactor unit (24), have the following proportions by weight: 2-Octyl (meth)acrylate: 70.00 to 95.00% by weight 2-Octanol: 1.00 to 15.00% by weight (Meth)acrylic acid: 1.00 to 10.00% by weight Acidic esterification catalyst: 0.50 to 10.00% by weight Polymerization inhibitor: 0.01 to 1.00% by weight Residual component: 2.49~10.00% by weight.

[0111] The heterogeneous azeotrope formed by cyclohexane and water of esterification exits one reactor (1) of the reactor units (24) in concentrations ranging from 10 to 50% by weight, these figures in weight percent referring to all exiting components including cyclohexane and water of esterification.

[0112] The invention will be considered in more detail below with reference to the drawings, which should be understood as schematic illustrations and which do not constitute a limitation of the invention, for example with regard to specific dimensions or design versions.

[0113] The following is shown: [Brief description of the drawings]

[0114] [Figure 1] Process overview for producing 2-octyl (meth)acrylate based on an evaporator as reactor heating element 30 for separating the heterogeneous azeotrope. [Diagram 2] FIG. 1 is a process overview for producing 2-octyl (meth)acrylate based on an evaporator as reactor heating element 30 and an azeotrope rectifier unit 25 for separating the heterogeneous azeotrope. [Diagram 3] Dividing wall column process overview. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0115] FIG. 1 shows a process overview for producing 2-octyl (meth)acrylate at each process stage, where each reactor includes an evaporator as the reactor heating element for separating the heterogeneous azeotrope.

[0116] Process Step (I): Esterification The esterification is reacted in a reactor unit 24 consisting of three cascaded reactors 1, 2, 3. The reactant streams enter the first reactor 1 of the cascade: 2-octanol 13, (meth)acrylic acid 14, acidic esterification catalyst 15, polymerization inhibitor 31 and azeotropic agent cyclohexane 17. After the first reactor 1 of the cascade reaches a certain level, a mass flow flows into the second reactor 2 of the cascade. After the second reactor 2 of the cascade reaches a certain level, a mass flow flows into the third reactor 3 of the cascade. After the third reactor 3 reaches a certain level, the resulting reaction effluent flows out of the reaction unit. All three reactors 1, 2, 3 of the reactor unit 24 are each equipped with 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 and the azeotropic agent cyclohexane formed during the esterification are partially evaporated as a heterogeneous azeotrope (cyclohexane / esterification water).

[0117] A gas stream enriched with the heterogeneous azeotrope is withdrawn from each reactor 1, 2, 3 and cooled until condensation occurs by downstream condenser 5. In downstream phase separator 6 an upper organic phase and a lower aqueous phase are formed.

[0118] The aqueous lower phase is discarded from the process. The organic upper phase contains up to 50-99.9% by weight of cyclohexane. This organic upper phase is fed to the first reactor 1 of the cascade and to the azeotrope rectification column 4 in the top-to-middle region of the column.

[0119] Process step (II): Alkaline extraction The reaction effluent from the esterification stage is neutralized with an alkaline solution 19 in a neutralization extraction unit 7 to neutralize the acidic esterification catalyst and unreacted (meth)acrylic acid. As a result, an upper neutralization phase containing 2-octyl (meth)acrylate and a lower neutralization phase containing salts formed by neutralization and water are formed. The lower neutralization phase 20 is discarded from the process.

[0120] Process step (III): Water extraction Following alkaline extraction, the upper neutralized phase is fed to a water wash extraction unit 8 where, upon addition of water 18, a lower water wash phase 20 comprising water and salt residues and an upper water wash phase comprising 2-octyl (meth)acrylate are formed. The lower water wash phase 20 is discarded from the process.

[0121] Process step (IV): Cyclohexane removal The upper water wash phase from the water wash extraction is fed to an azeotrope fractionator 9. Low boiler and cyclohexane are removed via the top of this column 9.

[0122] The components removed via the top of the column 9 are condensed in the range of 95-99.9% by weight and returned to the top region of the azeotrope rectification column 9. The remaining part is returned to the gaseous low boiler 23, for example after separation of octene, to the first reactor 1 of the cascade. Cyclohexane is typically conveyed from the column 9 to the first reactor 1 of the cascade in the range of 2-20% by weight, based on the total mass of cyclohexane fed to the entire process.

[0123] Process step (V): 2-octanol separation The proportion of the bottom discharge that is not returned to the azeotrope rectification column 9 is fed to the 2-octanol evaporator 110. 2-octanol is withdrawn via the 2-octanol evaporator 110 in an amount ranging from 20 to 60% by weight, based on the bottom discharge of the azeotrope rectification column 9 fed to the 2-octanol evaporator 110, condensed and fed completely to the first reactor 1 of the cascade.

[0124] Process stage (VI): Pure boiler separation The portion of the bottom discharge not returned to the 2-octanol evaporator 110 is fed to a pure boiler evaporator 111. The valuable 2-octyl (meth)acrylate product is withdrawn via the vapor stream of the pure boiler evaporator 111 in the range of 80-95 wt. %, based on the bottom discharge fed to the pure boiler evaporator 111, condensed and returned entirely to the pure boiler evaporator 111. The remaining residual portion of the bottom discharge of the octanol evaporator 110 is condensed and fed entirely to the high boiler evaporator 112.

[0125] Process Step (VII): High boiler separation The corresponding remaining portion of the bottom discharge of the pure boiler evaporator 111 is fed to the high boiler evaporator 112. The low boiler is withdrawn via the steam flow of the high boiler evaporator 112 in the range of 40-90% by weight, based on the bottom discharge of the pure boiler evaporator 111 fed to the high boiler evaporator 112, and is returned in its entirety to the pure boiler evaporator 111. Based on the circulation of the high boiler evaporator 112, up to 1-10% by weight of the high boiler 22 present at the bottom of the high boiler evaporator 112 is discharged from the process, and the remaining portion of the obtained high boiler 22 is evaporated and returned to the high boiler evaporator 112.

[0126] FIG. 2 shows a process schematic for producing 2-octyl (meth)acrylate in various process stages, in which an azeotrope rectifier 4 is used to separate the heterogeneous azeotrope.

[0127] Process Step (I): Esterification The esterification is reacted in a reactor unit 24 consisting of three cascaded reactors 1, 2, 3. The reactant streams enter the first reactor 1 of the cascade: 2-octanol 13, (meth)acrylic acid 14, acidic esterification catalyst 15, polymerization inhibitor 31 and azeotropic agent cyclohexane 17. After the first reactor 1 of the cascade reaches a certain level, a mass flow flows into the second reactor 2 of the cascade. After the second reactor 2 of the cascade reaches a certain level, a mass flow flows into the third reactor 3 of the cascade. After the third reactor 3 reaches a certain level, the resulting reaction effluent flows out of the reaction unit. All three reactors 1, 2, 3 of the reactor unit 24 are each equipped with 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 the esterification and the azeotropic agent cyclohexane are at least partially evaporated as a heterogeneous azeotrope (cyclohexane / esterification water).

[0128] Gas streams enriched with the heterogeneous azeotrope are withdrawn from the individual reactors 1, 2, 3 and fed to a downstream azeotrope rectifier 4. The azeotrope rectifier 4 is located in the reactor unit 24. A polymerization inhibitor 31 is fed to the top of the azeotrope rectifier 4.

[0129] The heterogeneous azeotrope-enriched gas stream is fed via the top of the azeotrope rectifier 4 and cooled until condensation occurs in the condenser 5. In the downstream phase separator 6, an upper organic phase and a lower aqueous phase are formed.

[0130] The aqueous lower phase is discarded from the process. The organic upper phase contains up to 50-99.9% by weight of cyclohexane. This organic upper phase is fed to the first reactor 1 of the cascade and to the azeotrope rectification column 4 in the top-to-middle region of the column.

[0131] Process step (II): Alkaline extraction The reaction effluent from the esterification stage is neutralized with an alkaline solution in a neutralization extraction unit 7 to neutralize the acidic esterification catalyst and unreacted (meth)acrylic acid. As a result, an upper neutralization phase containing 2-octyl (meth)acrylate and a lower neutralization phase containing salts formed by neutralization and water are formed. The lower neutralization phase is discarded from the process.

[0132] Process step (III): Water extraction Following alkaline extraction, the upper neutralized phase is fed to a water wash extraction unit 8 where, upon addition of water 18, a lower water wash phase 20 comprising water and salt residues and an upper water wash phase comprising 2-octyl (meth)acrylate are formed. The lower water wash phase 20 is discarded from the process.

[0133] Process step (IV): Cyclohexane removal The upper water wash phase from the water wash extraction is fed to an azeotrope fractionator 9. Low boiler and cyclohexane are removed via the top of this column 9.

[0134] The components removed via the top of the column 9 are condensed in the range of 95-99.9% by weight and returned to the top region of the azeotrope rectification column 9. The remaining part obtained is fed to a gaseous low boiler 23, for example after separation of octene, to the first reactor 1 of the cascade. Cyclohexane is typically conveyed from the column 9 to the first reactor 1 of the cascade in the range of 2-20% by weight, based on the total mass of cyclohexane fed to the entire process.

[0135] Process step (V): 2-octanol separation The proportion of the bottom draw that is not returned to the azeotrope 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% by weight, based on the bottom draw of the azeotrope rectification column 9 fed to the column 10. The components withdrawn via the top of the column 10 are fully condensed and returned to the 2-octanol rectification column 10 in a top area ranging from 0 to 50% by weight, while the remaining part of the obtained top draw is fed to the first reactor 1 of the cascade.

[0136] Process stage (VI): Pure boiler separation The portion of the bottom discharge which is not returned to the 2-octanol rectification column 10 is fed to a pure boiler rectification column 11. The valuable 2-octyl (meth)acrylate product is withdrawn via the top of this pure boiler rectification column 11 in the range of 80-95% by weight, based on the bottom discharge fed to the column 11. The discharge via the top of the pure boiler rectification column 11 is fully condensed and returned to the top region of the pure boiler rectification column 11 in the range of 0-60% by weight. The remaining portion of the bottom discharge of the obtained octanol rectification column 10 is fed to a high boiler separation.

[0137] Process (Step VII): High boiler separation The corresponding remaining portion of the bottom discharge of the pure boiler rectifier 11 is fed to the high boiler rectifier 12. A low boiler in the range of 40-300% by weight based on the bottom discharge fed to the high boiler rectifier 12 is withdrawn through the top of this high boiler rectifier 12, a part of the draw in the range of 40-90% by weight is returned to the pure boiler rectifier 11 and the resulting remaining portion is returned to the high boiler rectifier 12 in the top region of the column 12. At least a part of the high boiler 22 present at the bottom of the high boiler rectifier 12 is discharged from the process and the resulting remaining portion of the high boiler 22 is evaporated and returned to the bottom region of the high boiler rectifier 12.

[0138] Figure 3 shows an overview of the dividing wall column process.

[0139] The process overview shows a dividing wall column 131 with a dividing wall 138 dividing the dividing wall column 131 into a common upper column region 139, feed sections 140, 142 with rectification section 140 and stripping section 142, withdrawal sections 141, 143 with stripping section 141 and rectification section 143, and a common lower column region 144. The mixture 132 to be separated, comprising low boiler, 2-octyl (meth)acrylate and high boiler, enters the dividing wall column 131 between column sections 140 and 142. Pure product 133 is withdrawn, preferably in liquid form, between column sections 141 and 143. A vapor stream 145 obtained at the top of the column is partially condensed in condenser 136, which may be supplemented by an aftercooler, and is split into a return stream 146 and a distillate stream 134. The non-condensed fraction from the condenser 136, which contains low-boiling impurities, is withdrawn in vapor form as stream 139. The liquid 147 at the bottom of the column is partially evaporated in the evaporator 137 and returned to the column via conduit 148. A side stream 135 containing high-boiling impurities is discharged. The evaporator 137 can be designed as a natural circulation evaporator or as a forced circulation evaporator, in the latter case a circulation pump is additionally required for the liquid stream 147. Particularly advantageous in terms of avoiding undesired polymerization reactions is the use of falling film evaporators or thin layer evaporators instead of forced circulation evaporators, since the shortest residence times are possible with this design.

[0140] To reduce the residence time of the liquid in the evaporator system, it is preferable to place the level control in the supply conduit for liquid stream 147 rather than in the lower tower cap. EXAMPLES

[0141] In both the following examples and throughout this document, the term "qualitative GC" refers to gas chromatography (GC) where individual components are assigned by comparison of retention times, and the concentration of each component in the mixture is given as the peak area (area %).

[0142] In both the following examples and throughout this document, the term "quantitative GC" refers to gas chromatography (GC) with quantification by reference to the internal standard n-tetradecane. The components 2-octyl acrylate, cyclohexane, and 2-octanol were quantified. The concentration of each component in the mixture is given as weight percent (wt%).

[0143] The expected amount of water corresponds to the amount of water at complete conversion or infinite reaction time and results from the sum of the water content of the starting materials used and the esterification water formed at 100% conversion. The sum of these water contents is also called reaction water in this specification. The maximum esterification water formed can be calculated by the moles of water formed that correspond to the moles of acrylic acid used. Note that in the balance sheet, some carryover of acrylic acid into the aqueous phase is not taken into account.

[0144] Example 1: Discontinuous esterification with cyclohexane (process step I) A 0.75 L heatable double-walled reactor equipped with a thermal sensor, anchor agitator, water separator, jacketed coil condenser and air inlet was initially 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. Then 161 g of acrylic acid was metered in, which was stabilized with 200 ppm of MeHQ. 6.4 g of 100% methanesulfonic acid was added. The total batch size was 599 g.

[0145] The reaction mixture was heated at a bath temperature of 125° C. The reaction time was initiated by heating. During the course of the reaction, bottom samples were taken and analyzed by gas chromatography to monitor the course of the reaction.

[0146] After 0.58 hours, at a bottom temperature of 99° C., water started to pass through and the distillation time began. After a distillation time of 6 hours, corresponding to a reaction time of 6.59 hours, the reaction was terminated when a bottom temperature of 119° C. was reached. 35.6 g of water were distilled off, corresponding to 88.2% of the expected amount of water.

[0147] After 6 hours of distillation, the reaction mixture was analyzed by gas chromatography. 2-octanol and 2-octyl acrylate were quantified. After 6 hours of distillation, corresponding to a reaction time of 6.59 hours, the mixture contained 71.54% by weight of octyl acrylate and 5.75% by weight of 2-octanol. The reaction mixture contained 0.27% by area of ​​octene, 1.78% by area of ​​diacrylates and 1.85% by area of ​​oxyesters.

[0148] The conversion was 92.56% based on 2-octanol.

[0149] Comparative Example 1: Discontinuous esterification with toluene (process stage I) A 0.75 L heatable double-walled reactor equipped with a thermal sensor, anchor agitator, water separator, jacketed coil condenser and air inlet was initially 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. Then 161 g of acrylic acid was metered in, which was stabilized with 200 ppm of MeHQ. 6.4 g of 100% methanesulfonic acid was added. The total batch size was 599 g.

[0150] The reaction mixture was heated at a bath temperature of 125° C. The reaction time was initiated by heating. During the course of the reaction, bottom samples were taken and analyzed by gas chromatography to monitor the course of the reaction.

[0151] After 0.92 hours, at a bottom temperature of 108° C., water started to pass through and the distillation time began. After a distillation time of 6 hours, corresponding to a reaction time of 6.92 hours, the reaction was terminated when a bottom temperature of 116° C. was reached. 17.7 g of water were distilled off, corresponding to 43.9% of the expected amount of water.

[0152] After 6 hours of distillation, the reaction mixture was analyzed by gas chromatography. 2-octanol and 2-octyl acrylate were quantified. After 6 hours of distillation, corresponding to a reaction time of 6.92 hours, the mixture contained 58.38% by weight of octyl acrylate and 13.35% by weight of 2-octanol. The reaction mixture contained 0.15% by area of ​​octene, 2.18% by area of ​​diacrylates and 1.57% by area of ​​oxyesters.

[0153] The conversion was 81.39% based on 2-octanol.

[0154] Comparative Example 2: Discontinuous esterification with 2-octanol as azeotropic agent (process stage I) A 0.75 L heatable double-walled reactor equipped with a thermal sensor, anchor agitator, water separator, jacketed coil condenser and air inlet was initially charged with 300 g of 2-octanol, 0.6 g of phenothiazine, 0.6 g of a 1% by weight solution of HO-TEMPO in 2-octyl acrylate, further 130 g of 2-octanol, 0.015 g of CuCl and 0.240 g of 50% hypophosphorous acid. Then 161 g of acrylic acid was metered in, which was stabilized with 200 ppm of MeHQ. 6.4 g of 100% methanesulfonic acid was added. The total batch size was 599 g.

[0155] The reaction mixture was heated at a bath temperature of 125° C. The reaction time was initiated by heating. During the course of the reaction, bottom samples were taken and analyzed by gas chromatography to monitor the course of the reaction.

[0156] After 1.22 hours, water started to pass through and the distillation time started at a bottom temperature of 112° C. The reaction was terminated after a distillation time of 6 hours, corresponding to a reaction time of 7.22 hours, 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.

[0157] After 6 hours of distillation, the reaction mixture was analyzed by gas chromatography. 2-octanol and 2-octyl acrylate were quantified. After 6 hours of distillation, corresponding to a reaction time of 7.22 hours, the mixture contained 54.64% by weight of octyl acrylate and 33.01% by weight of 2-octanol. The reaction mixture contained 0.09% by area of ​​octene, 1.11% by area of ​​diacrylates and 2.20% by area of ​​oxyesters.

[0158] The conversion was 62.35% based on 2-octanol.

[0159] Comparative Example 3: Discontinuous esterification without azeotropic agent (Process Stage I) A 0.75 L heatable double-walled reactor equipped with a thermal sensor, anchor agitator, water separator, jacketed coil condenser and air inlet was initially 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. Then 206 g of acrylic acid was metered in, which was stabilized with 200 ppm of MeHQ. 8.2 g of 100% methanesulfonic acid was added. The total batch size was 599 g.

[0160] The reaction mixture was heated at a bath temperature of 125° C. The reaction time was initiated by heating. During the course of the reaction, bottom samples were taken and analyzed by gas chromatography to monitor the course of the reaction.

[0161] After 1.17 hours, water started to pass through and the distillation time started at a bottom temperature of 111° C. The reaction was terminated after 6 hours of distillation time, corresponding to a reaction time of 7.17 hours, when a bottom temperature of 113° C. was reached. 11.0 g of water were distilled off, corresponding to 21.4% of the expected amount of water.

[0162] After 6 hours of distillation, the reaction mixture was analyzed by gas chromatography. 2-octanol and 2-octyl acrylate were quantified. After 6 hours of distillation, corresponding to a reaction time of 7.17 hours, the mixture contained 59.16% by weight of octyl acrylate and 21.33% by weight of 2-octanol. The reaction mixture contained 0.06% by area of ​​octene, 2.57% by area of ​​diacrylates and 2.00% by area of ​​oxyesters.

[0163] The conversion was 73.5% based on 2-octanol.

[0164] summary All experiments were carried out at a bath temperature of 125 °C. The same molar ratio of acid and alcohol was used. The exception here was the experiment using 2-octanol as the azeotropic agent, where the molar ratio of acrylic acid to 2-octanol was 1:1.45. The catalyst concentration based on the acid used was always the same.

[0165] The azeotropes in the experiments were cyclohexane, toluene and 2-octanol, which were present in addition to 2-octanol for the reaction. Additionally, in one experiment, no azeotrope was used.

[0166] Tabular summary of results Table 1 shows the reaction summary for Example 1 using cyclohexane as an azeotropic agent. The distillation time, reaction time, bottom temperature, reaction water and conversion are listed. The aqueous conversion was calculated as follows:

number

[0167] Here, the reaction water at t=∞ means the maximum expected amount of reaction water present in the event of complete conversion in the esterification, and the reaction water at t=xh corresponds to the amount of reaction water present at time x due to the esterification and the water content of the starting materials used.

[0168] [Table 1]

[0169] Table 2 summarizes the GC values ​​of the qualitative GC measurements at various distillation times for Example 1 using cyclohexane as an azeotropic agent, including the total of 1-octene and 2-octene, diacrylic acid esters (DIAA esters), oxyesters, and 2-octyl acrylate contents, conversion calculated from the qualitative GC values, and the ratio of 2-octyl acrylate to the total of the by-products 1-octene, 2-octene, DIAA esters, and oxyesters.

[0170] The conversion was calculated as follows:

number

[0171] Here, 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.

[0172] [Table 2]

[0173] Table 3 summarizes various distillation times for Example 1 using cyclohexane as an azeotropic agent. The weight fraction of 2-octyl acrylate, the weight fraction of 2-octanol, and the molar conversion are listed, where the molar conversion is calculated from the quantitative GC value.

[0174] The molar conversion was calculated as follows:

number

[0175] The abbreviation W_Mol is used for molecular weight.

[0176] Here, 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.

[0177] [Table 3]

[0178] Table 4 shows the reaction summary for Comparative Example 1 using toluene as an azeotropic agent. The distillation time, reaction time, bottom temperature, reaction water and conversion are listed. The aqueous conversion was calculated as follows:

number

[0179] Here, the reaction water at t=∞ means the maximum expected amount of reaction water present in the event of complete conversion in the esterification, and the reaction water at t=xh corresponds to the amount of reaction water present at time x due to the esterification and the water content of the starting materials used.

[0180] [Table 4]

[0181] Table 5 shows an overview of the GC values ​​of the qualitative GC measurements at various distillation times for Comparative Example 1 using toluene as an azeotropic agent, including the total of 1-octene and 2-octene, DIAA ester, oxyester, and 2-octyl acrylate contents, conversion calculated from the qualitative GC values, and the ratio of 2-octyl acrylate to the total of the by-products 1-octene, 2-octene, DIAA ester, and oxyester.

[0182] The conversion was calculated as follows:

number

[0183] Here, 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.

[0184] [Table 5]

[0185] Table 6 shows a summary of the distillation time for Comparative Example 1 using toluene as an azeotropic agent. The weight fraction of 2-octyl acrylate, the weight fraction of 2-octanol, and the molar conversion are listed, where the molar conversion is calculated from the quantitative GC value.

[0186] The molar conversion was calculated as follows:

number

[0187] The abbreviation W_Mol is used for molecular weight.

[0188] Here, 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.

[0189] [Table 6]

[0190] Table 7 shows the reaction summary for Comparative Example 2 using 2-octanol as an azeotropic agent. The distillation time, reaction time, bottom temperature, reaction water and conversion are listed. The aqueous conversion was calculated as follows:

number

[0191] Here, the reaction water at t=∞ means the maximum expected amount of reaction water present in the event of complete conversion in the esterification, and the reaction water at t=xh corresponds to the amount of reaction water present at time x due to the esterification and the water content of the starting materials used.

[0192] [Table 7]

[0193] Table 8 shows a summary of the GC values ​​of the qualitative GC measurements at various distillation times for Comparative Example 2 using 2-octanol as an azeotropic agent. The total of 1-octene and 2-octene, DIAA ester, oxyester, and 2-octyl acrylate contents, conversion calculated from the qualitative GC values, and the ratio of 2-octyl acrylate to the total of the by-products 1-octene, 2-octene, DIAA ester, and oxyester are listed.

[0194] The conversion was calculated as follows:

number

[0195] Here, 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.

[0196] [Table 8]

[0197] Table 9 shows a summary of the distillation time for Comparative Example 2 using 2-octanol as an azeotropic agent. The weight fraction of 2-octyl acrylate, the weight fraction of 2-octanol, and the molar conversion are listed, where the molar conversion is calculated from the quantitative GC value.

[0198] The molar conversion was calculated as follows:

number

[0199] The abbreviation W_Mol is used for molecular weight.

[0200] Here, 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.

[0201] [Table 9]

[0202] Table 10 shows the reaction summary for Comparative Example 3 where no azeotropic agent was used. The distillation time, reaction time, bottom temperature, reaction water and conversion are listed. The aqueous conversion was calculated as follows:

number

[0203] Here, the reaction water at t=∞ means the maximum expected amount of reaction water present in the event of complete conversion in the esterification, and the reaction water at t=xh corresponds to the amount of reaction water present at time x due to the esterification and the water content of the starting materials used.

[0204] [Table 10]

[0205] Table 11 shows an overview of the GC values ​​of the qualitative GC measurement at various distillation times for Comparative Example 3 in which no azeotropic agent was used. The total of 1-octene and 2-octene, DIAA ester, oxyester, and 2-octyl acrylate contents, conversion calculated from the qualitative GC values, and the ratio of 2-octyl acrylate to the total of by-products 1-octene, 2-octene, DIAA ester, and oxyester are listed.

[0206] The conversion was calculated as follows:

number

[0207] Here, 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.

[0208] [Table 11]

[0209] Table 12 shows a summary of the distillation time for Comparative Example 3 where no azeotropic agent was used. The weight fraction of 2-octyl acrylate, the weight fraction of 2-octanol, and the molar conversion are listed, where the molar conversion is calculated from the quantitative GC value.

[0210] The molar conversion was calculated as follows:

number

[0211] The abbreviation W_Mol is used for molecular weight.

[0212] Here, 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.

[0213] [Table 12]

[0214] The concentration of by-products increases as the reaction proceeds. At similar conversions, the formation of by-products is significantly lower when cyclohexane is used as the azeotrope agent, compared to when toluene and 2-octanol are used as the azeotrope agent, or when no azeotrope agent is used.

[0215] Table 13 below compares the ratio of 2-octyl acrylate to the sum of by-products 1-octene, 2-octene, DIAA esters and oxyesters at similar conversions, as determined from the GC values ​​of the qualitative GC, with examples shown with and without the respective azeotropes cyclohexane, toluene and 2-octanol.

[0216] [Table 13]

[0217] This leads to the following advantages when using cyclohexane, comparing the results with Comparative Examples 1, 2 and 3: Using cyclohexane as an azeotropic agent results in the highest conversion with the same energy input. This results in less loss of (meth)acrylic acid in the subsequent alkaline extraction unit (process stage II). Furthermore, less 2-octanol is recycled and there is a smaller reactor with the same throughput. By using cyclohexane as an azeotropic agent, reflux begins sooner after heating begins, resulting in shorter reaction times and less energy being required. Cyclohexane azeotrope separates water most efficiently. When cyclohexane is used as an azeotropic agent, the 2-octyl acrylate content in the reaction mixture is the highest for the same reaction volume and the same distillation time, and therefore the absolute space-time yield is the highest. When cyclohexane is used as an azeotropic agent, fewer by-products are formed at the same conversion.

[0218] Comparative Example 4: Esterification, Alkaline Extraction and Water Washing Without Entrainer (Process Steps I, II and III) A heatable 0.75 L double-walled reactor equipped with, inter alia, a Normag glass attachment (source: www.normag-glas.de) including a thermal sensor, an anchor stirrer, a jacketed coil condenser, a wastewater sink with two needle valves, a vacuum frame with two spindle valves as shutoff and vent valves, as well as a vacuum pump and an air inlet, was initially 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. Then, 209 g of acrylic acid were metered in, which was stabilized with 200 ppm of MeHQ. 6.4 g of 100% methanesulfonic acid were added. This was heated to a bath temperature of 130° C. to start the reaction time. After one hour, at a bottom temperature of 112° C., water started to pass through and the distillation time began. After 2 hours of distillation time, the absolute pressure drop was started at 50 mbar and dropped to 100 mbar. The internal temperature in the bottom was a maximum of 122° C. After 4.1 hours of distillation time, the reaction was terminated. 71.8 g were distilled off. After cooling, the reaction mixture was extracted with water, 12.5% ​​NaOH solution and then again with water. After phase separation, 50 mg of MeHQ were added to the organic phase. This gave 403 g of 2-octyl acrylate with a purity of 85.4 GC area %. 3.5 area % of 2-octanol was still present, as well as 5.9 area % of diacrylic acid esters and 3.1 area % of oxyesters. Ethanol was added to the two-phase distillate to form a single phase, which was analyzed by qualitative GC and acid-base and Karl Fischer titrations. Based on these results, the composition of the distillate before the addition of ethanol was mathematically determined. The distillate consisted of 51.8% water, 29.5% acrylic acid, plus 6.3% 2-octanol and 9.5% 2-octyl acrylate, plus 2.2% octene.

[0219] Example 2: Esterification, alkaline extraction and washing with cyclohexane (process steps I, II and III) In a heatable 4 L double-walled reactor equipped inter alia with a thermal sensor, a disk agitator, a water separator, a jacketed coil condenser and an air inlet, 1503 g of 2-octanol, 4.01 g of phenothiazine and 1.94 g of MeHQ were initially charged. Then 1082 g of acrylic acid were metered in, the acrylic acid being stabilized with 200 ppm of MeHQ. 65.7 g of p-toluenesulfonic acid monohydrate and 1189 g of cyclohexane were added and the mixture was heated. Water was passed through at a bottom temperature in the range of 92-104 ° C. After 7.2 hours, the reaction was stopped. After cooling, the reaction mixture was extracted with water, 12.5% ​​NaOH solution and then again with water. After phase separation, 250 mg of MeHQ was added to the organic phase and concentrated in vacuum. This gave 2072 g of 2-octyl acrylate with a purity of 93.2 GC area %. 2.6 area % 2-octanol was still present, as was 2.0 area % diacrylate and 1.3 area % oxyester. GC analysis of the organic liquid exiting the water separator showed 99.38 area % cyclohexane, plus 0.47 area % acrylic acid, 0.03 area % 2-octanol, 0.1 area % 2-octyl acrylate, and 0.01 area % octene. Karl Fischer titration of the aqueous distillate gave 85 wt % water.

[0220] Example 3: Esterification, alkaline extraction and washing with cyclohexane (process steps I, II and III) In this Example 3, inter alia, a reactor 1 and an azeotrope fractionator 4 were used. The process stages I, II and III for esterification, alkaline extraction and water washing extraction were operated continuously.

[0221] A heatable 1.6 L double-walled glass reactor 1 was equipped, inter alia, with a heatable cover and a three-stage crossbeam stirrer.

[0222] The azeotrope rectification column 4 used was a double-walled mirror glass column with dimensions 50 cm (height) × 43 mm (diameter) equipped with structured packing (Montz Pack Type A3-750, 3 × 150 mm × 41 mm) from Montz (source: www.montz.de / gewebepackung-typ-3a, accessed on November 1, 2021).

[0223] The setup was further equipped with a cooler, a phase separator 6, a lean air inlet, a vessel and a device for reactant metering, a vessel and a device for heteroazeotropy, a receiver for the bottom discharge and a receiver for stabilization of the column.

[0224] First, a stabilized reaction mixture was produced by discontinuous experiments consisting essentially of 2-octanol, acrylic acid and 2-octyl acrylate and methanesulfonic acid catalyst. The starting materials for producing this reaction mixture were used in proportions corresponding to the starting mixture that was subsequently metered in. The starting mixture for producing the reaction mixture contained 45% by weight of 2-octanol, 25% by weight of pure acrylic acid, 0.93% by weight of 100% methanesulfonic acid, 29% by weight of cyclohexane, 0.04% by weight calculated as 100% hypophosphorous acid, 0.1% by weight of phenothiazine and 0.002% by weight of CuCl. The production was carried out analogously to Example 2.

[0225] The bath temperature was set at 128°C and the cover temperature was set at 95°C.

[0226] A total of 667 g / h of the starting mixture were metered into the first reactor 1. The starting mixture may be initially charged into one or more vessels, the mixtures of substances in the vessels may differ in their composition. In total, the starting mixture consisted of 45% by weight of 2-octanol, 25% by weight of pure acrylic acid, 0.93% by weight of 100% methanesulfonic acid, 29% by weight of cyclohexane, 0.04% by weight of hypophosphorous acid (calculated 100%) and 0.1% by weight of phenothiazine. CuCl was also added as a solid at equal intervals to an average concentration of 0.002%.

[0227] 350 g / h of cyclohexane, stabilized with HO-TEMPO, were also metered into the top of the column. Level-controlled material was continuously removed from reactor 1. The reactor contents (1) were periodically analyzed by gas chromatography.

[0228] Once equilibrium was reached and a constant bottom temperature of 108° C. was reached, the reaction discharge vessel was replaced, the forecut material was discarded, and fresh reaction discharge was collected.

[0229] In the second experiment, this material was fed at the same rate as it was removed in the first experiment to reactor 1, which was still charged with the reaction mixture from the previous experiment. In addition, 150 g / h of cyclohexane were added to the bottom and 50 g / h of cyclohexane (stabilized with HO-TEMPO) were added to the top of the column. Again, level-controlled material was continuously removed from reactor 1.

[0230] Once equilibrium was reached and a constant bottom temperature of 113° C. was reached, the reaction discharge vessel was replaced, the forecut material was discarded, and fresh reaction discharge was collected.

[0231] In the third experiment, this material was fed at the same rate as it was removed in the second experiment to reactor 1, which was still charged with the reaction mixture from the previous experiment. In addition, 150 g / h of cyclohexane were added to the bottom and 50 g / h of cyclohexane (stabilized with HO-TEMPO) were added to the top of the column. Again, level-controlled material was continuously removed from reactor 1.

[0232] Once equilibrium was reached and a constant bottom temperature of 114° C. was reached, the reaction discharge vessel was replaced, the forecut material was discarded, and fresh reaction discharge was collected.

[0233] The material was investigated by acid-base titration and qualitative and quantitative gas chromatography, where octyl acrylate, cyclohexane and 2-octanol were quantified by gas chromatography, and acrylic acid and methanesulfonic acid were determined by acid-base titration. The contents of the secondary components octene, diacrylate and oxyester were determined by qualitative GC. In the case of secondary components present only in low fractions in the reaction mixture, it was further assumed that the values ​​determined as area percentages correspond to the values ​​obtained by quantification.

[0234] The 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.% octene, 1.1 wt.% diacrylates, and 1.5 wt.% oxyesters.

[0235] The reaction effluent was subjected to continuous neutralization in an alkali extraction unit 7 and then water washing in a water washing extraction unit 8.

[0236] The alkaline extraction unit 7 comprises a continuous device for neutralization with 10% aqueous sodium hydroxide solution NaOH, which consists of a mixing pump, a phase separator 6 with a diameter of 40 mm and a phase interface regulator.

[0237] At a temperature of 30° C., 0.76 kg / h of dilute aqueous sodium hydroxide solution NaOH and 3.3 kg / h of the reaction discharge were dispersed by means of a mixing pump and separated in a phase separator 6.

[0238] The neutralized organic phase was then dispersed in a water washing extraction unit 8 with 5 kg / h of water by a static mixer (Kenics-Mischer (https: / / de.wikipedia.org / wiki / Statischer_Mischer) with an internal diameter of 4.9 mm and 27 elements, retrieved on 23 November 2021) and subsequently separated in a phase separator 6 with a diameter of DN40.

[0239] Example 4: Distillation (Process Steps IV to VII) The distillative purification of 2-octyl acrylate was carried out in four process stages operated continuously. Cyclohexane Separation(IV) 2-Octanol Separation (V) Pure boiler separation (VI) High boiler separation (VII)

[0240] The experimental configuration was identical for each individual process stage IV-VII and included in each case a thin-layer evaporator with a surface area of ​​0.016 m2, which was used in each rectification column 9, 10, 11, 12. Each rectification column 9, 10, 11, 12 had a diameter of 30 mm and a packing length of 100 cm. The packing in each rectification column 9, 10, 11, 12 was Montz A3-750. There was of course a respective condenser 5 belonging to the rectification column 9, 10, 11, 12 with a reflux partition for reflux and distillate discharge, as well as vessels and pumps for the metering of reactants, vessels and devices for distillate, vessels for the bottom discharge, and vessels for stabilization of the columns 9, 10, 11, 12.

[0241] The thin film evaporator was heated with Marlotherm oil.

[0242] In this Example 4, the individual components were determined by various measurement methods. Water was determined by Karl Fischer titration, while 2-octyl acrylate, cyclohexane and 2-octanol were determined by quantitative GC. The remaining components were determined by qualitative GC.

[0243] Cyclohexane Separation The mixture emerging from the water washing extraction unit 8 had the following composition: Water 0.30% by weight Cyclohexane 23.80% by weight Octene 0.29% by weight 2-Octanol 3.95% by weight 2-Octyl acrylate 68.80% by weight Diacrylic acid ester 1.14% by weight Oxyester 1.54% by weight Unknown Remaining

[0244] The feed rate to the top of the azeotropic mixture rectification column 9 was 300 g / h.

[0245] The absolute pressure at the top of the column was 100 mbar and the bottom temperature was 105°C.

[0246] The bottom product, running short at 230 g / h, had the following composition: Water 0.00% by weight Cyclohexane 1.07% by weight Octene 0.34% by weight 2-Octanol 5.14% by weight 2-Octyl acrylate 89.72% by weight Diacrylic acid ester 1.49% by weight Oxyester 2.01% by weight Unknown Remaining

[0247] The distillate discharged at 70 g / h had the following composition: Water 1.28% by weight Cyclohexane 98.50% by weight Octene 0.11% by weight 2-Octanol 0.05% by weight 2-Octyl acrylate 0.06% by weight Diacrylate ester 0.00% by weight Oxyester 0.00% by weight

[0248] 2-Octanol Separation For the separation of 2-octanol the same experimental equipment was used as in the previous process step. The bottom effluent from the cyclohexane separation was metered at a rate of 230 g / h into 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.

[0249] The bottom product, running short at 190 g / h, had the following composition: Water 0.00% by weight Cyclohexane 0.00% by weight Octene 0.00% by weight 2-Octanol 0.01% by weight 2-Octyl acrylate 95.47% by weight Diacrylic acid ester 1.80% by weight Oxyester 2.43% by weight Unknown Remaining

[0250] The distillate discharged at 40 g / h had the following composition: Water 0.00% by weight Cyclohexane 6.12% by weight Octene 1.98% by weight 2-Octanol 29.50% by weight 2-Octyl acrylate 62.40% by weight Diacrylate ester 0.00% by weight Oxyester 0.00% by weight

[0251] Pure boiler separation For the pure boiler separation, the same experimental setup was used as in the previous process step. The bottom effluent from the 2-octanol separation experiment was metered into the bottom of the pure boiler rectifier 11 at a rate of 190 g / h. The absolute pressure at the top of the column was 10 mbar and the bottom temperature was 95° C. A reflux ratio of 3 g / g was set in the reflux partition. To avoid polymerization in the experimental setup, 2 g / h of 2-octyl acrylate (stabilized with 1% phenothiazine) was metered into the top of the pure boiler rectifier 11.

[0252] The bottom product, running short at 32 g / h, had the following composition: Water 0.00% by weight Cyclohexane 0.00% by weight Octene 0.00% by weight 2-Octanol 0.00% by weight 2-Octyl acrylate 74.49% by weight Diacrylic acid ester 10.69% by weight Oxyester 14.44% by weight Phenothiazine 0.13% by weight Unknown Remaining

[0253] The distillate discharged at 160 g / h had the following composition: Water 0.00% by weight Cyclohexane 0.00% by weight Octene 0.00% by weight 2-Octanol 0.01% by weight 2-Octyl acrylate 99.70% by weight Diacrylic acid ester 0.00% by weight Oxyester 0.00% by weight Unknown Remaining

[0254] High boiler separation For the high boiler separation the same experimental equipment was used as for the previous process stage. The bottom effluent obtained from the pure boiler separation was metered into the bottom of the high boiler rectification column 12 at a rate of 32 g / h. The absolute pressure at the top of the column was 5 mbar and the bottom temperature was 100° C. The reflux partition was set with a reflux ratio of 3 g / g.

[0255] The bottom product, running short at 16 g / h, had the following composition: Water 0.00% by weight Cyclohexane 0.00% by weight Octene 0.00% by weight 2-Octanol 0.00% by weight 2-Octyl acrylate 49.27% ​​by weight Diacrylic acid ester 21.37% by weight Oxyester 28.87% by weight Phenothiazine 0.25% by weight Unknown Remaining

[0256] The distillate discharged at 16 g / h had the following composition: Water 0.00% by weight Cyclohexane 0.00% by weight Octene 0.00% by weight 2-Octanol 0.00% by weight 2-Octyl acrylate 99.72% by weight Diacrylic acid ester 0.00% by weight Oxyester 0.00% by weight Unknown Remaining [Explanation of symbols]

[0257] 1. Reactor 1 2. Reactor 2 3. Reactor 3 4 Azeotrope rectification column 5 Condensers for Heterogeneous Azeotropic Mixtures 6 Phase separators for heterogeneous azeotropic mixtures 7 Neutralization Extraction Unit 8. Water washing extraction unit 9 Azeotrope rectification column 10 2-Octanol rectification column 110 2-Octanol Evaporator 11 Pure boiler rectifier 111 Pure boiler evaporator 12 High-temperature boiler rectifier 112 High-pressure boiler evaporator 13 2-Octanol supply 14 (Meth)acrylic acid supply 15 Acid esterification catalyst supply 16 Wastewater discharged from the phase separator (6). 17 Cyclohexane Supply 18 Water supply for washing 19 Alkaline solution supply 20 Discharge of water with salt residues from alkaline extract and / or water-washed extract 21 Discharge of valuable 2-octyl (meth)acrylate product 22 High boiler discharge formed by bottom high boiler removal. 23 Low boiler discharge removed from the process of cyclohexane separation after discharge of the cyclohexane concentrated mass stream. 24 Reactor Unit 25 Azeotropic mixture rectification column unit 30 Reactor Heating Element 31 Provision of polymerization inhibitors and / or further stabilizers 131 Bulkhead Tower 132 Mixtures separated in a dividing wall column 134 Dividing wall column distillate stream 135 Sidestream of Bulkhead Tower 136 Dividing wall column condenser 137 Dividing wall column evaporator 138 Bulkhead Tower Bulkhead 139 Common upper column region of dividing wall columns 140 Dividing wall column feed section 141 Dividing wall column withdrawal section 142 Separation section of dividing wall tower 143 Rectification section of dividing wall column 144 Lower column region of dividing wall column 145 Vapor flow in dividing wall column 146 Return flow of bulkhead tower 147 Liquid flow in dividing wall columns

Claims

1. A method 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 an entrainer (cyclohexane), comprising: providing a reactor unit (24), wherein a reactor (1) having a reactor heating element (30) is located within said reactor unit (24); feeding 2-octanol (13), (meth)acrylic acid (14), an acidic esterification catalyst (15), cyclohexane (17), and a polymerization inhibitor (31) into the reactor (1); carrying out esterification in said reactor (1) to form a liquid reaction mixture, said esterification in said reactor (1) being carried out at a bottom temperature in the range of 90 to 130°C and an absolute pressure in the range of 0.5 to 2.0 bar, and obtaining a reaction effluent obtained from said reactor (1); the resulting reaction effluent comprises at least 2-octyl (meth)acrylate, 2-octanol, (meth)acrylic acid, an acidic esterification catalyst, cyclohexane, esterification water, and a polymerization inhibitor, and the esterification water formed in the esterification forms a heterogeneous azeotrope with the cyclohexane azeotroping agent; evaporating the heterogeneous azeotrope from the liquid reaction mixture in the reactor (1), said evaporation being achieved by the reactor heating element (30); Removing the gas heterogeneous azeotrope from the reactor (1), the gas heterogeneous azeotrope is condensed in a condenser (5) and then fed to a phase separator (6) in which the esterification water is separated as a lower phase and the cyclohexane is separated as an upper phase; A method comprising:

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

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

4. the cyclohexane obtained as the upper phase in the phase separator (6) is recycled to the reactor unit (24) in a proportion by weight ranging from 40% to 100% by weight, preferably ranging from 50 to 99.9% by weight, The remaining portion of the cyclohexane obtained is fed to the lower to middle region of the top of the azeotrope rectification column (4), The method of claim 2.

5. Following the esterification, alkaline extraction of the resulting reaction effluent is carried out with an alkaline solution (19), The acidic esterification catalyst and unreacted (meth)acrylic acid are neutralized in a neutralization extraction unit (7), As a result, an upper neutralized phase containing 2-octyl(meth)acrylate and a lower neutralized phase (20) containing the salt produced by the neutralization and water are obtained. The method according to any one of claims 1 to 4.

6. Following the alkaline extraction of the reaction effluent, the upper neutralized phase obtained from the neutralization extraction unit (7) is extracted with water (18) in a water washing extraction unit (8), A lower water wash phase containing water and salt residues and an upper water wash phase containing 2-octyl (meth)acrylate are formed. The method of claim 5.

7. Following the alkaline extraction or following the water wash extraction of the reaction effluent, the azeotropic agent cyclohexane is separated from the upper neutral phase or the upper water wash phase in an azeotrope rectification column unit; an azeotrope rectifier (9) located within the azeotrope rectifier unit; the azeotrope rectification column (9) is operated under 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 cyclohexane azeotroping agent, octene, 2-octanol and a mass flow portion of 2-octyl (meth)acrylate in the range of 0.1 to 5.0%, based on the upper neutralized phase fed or the upper water wash phase fed, The components fed overhead form an azeotropic mass stream which is condensed and fed to said reactor (1) of the reactor unit (24) in the range of 50-100%; The remaining azeotrope mass flow portion is condensed and recycled to the top of the azeotrope rectification column (9), while high-boilers containing di(meth)acrylic acid esters and oxyesters, such as alkoxyalkyl esters of (meth)acrylic acid, as well as 2-octanol and 2-octyl (meth)acrylate, are removed via the bottom discharge of the azeotrope rectification column (9), In the range of 20 to 95% of the mass flow of the bottom effluent, it flows through an evaporator and is subsequently recycled to the azeotrope rectification column (9).

7. The method according to claim 5 or 6.

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

9. Following removal of the cyclohexane azeotropic agent, 2-octanol is separated from the mass stream produced by the bottom discharge of the azeotropic rectification column (9) in a 2-octanol rectification column unit or a 2-octanol evaporation unit, a 2-octanol rectification column (10) is located in the 2-octanol rectification column unit or a 2-octanol evaporator (110) is located in the 2-octanol evaporation unit, and the 2-octanol rectification column (10) or the 2-octanol evaporator (110) is operated under 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, The mass flow produced by the bottom discharge of the azeotrope rectification column (9) is metered to a region below the top to the middle of the 2-octanol rectification column (10) or to a 2-octanol inlet of the 2-octanol evaporator (110), the components discharged from the top of the 2-octanol rectification column (10) or the 2-octanol evaporator outlet of the 2-octanol evaporator (110) are supplied to the reactor unit (24) in an amount ranging from 20 to 50% based on the mass flow of the discharged components; The discharge component in the range of 2 to 40 wt% consists of 2-octanol, while a high boiler containing 2-octyl (meth)acrylate and di(meth)acrylic acid esters and oxyesters is extracted as a bottom discharge from the 2-octanol rectification column (10) or the 2-octanol evaporator (110); 20 to 95% of the mass flow of the bottom effluent flows through an evaporator and is subsequently recycled to the 2-octanol rectification column (10) or the 2-octanol evaporator (110). The method of claim 7.

10. the separation of the 2-octanol is followed by a pure boiler separation from the mass stream provided via the bottom discharge of the 2-octanol rectifier (10) or the 2-octanol evaporator (110) in a pure boiler rectifier unit or a pure boiler evaporator unit, a pure boiler rectifier (11) located in the pure boiler rectifier unit or in a pure boiler evaporator (111) in the pure boiler evaporator unit; said pure boiler rectification column (11) or said pure boiler evaporator (111) is operated under 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, The mass flow produced by the bottom discharge of the 2-octanol rectification column (10) or the 2-octanol evaporator (110) is metered to the region from below the top to the center of the pure boiler rectification column (11) or to the pure boiler evaporator inlet of the pure boiler evaporator (111), In order to stabilize the pure boiler rectification column (11) or the pure boiler evaporator (111), 2-octyl (meth)acrylate and a polymerization inhibitor are metered in the range of 0.01 to 1.0%, respectively, based on the mass flow generated by the bottom discharge of the 2-octanol rectification column (10) or the bottom discharge of the 2-octanol evaporator (110) into the region from the bottom to the center of the pure boiler rectification column (11) or into the pure boiler evaporator inlet of the pure boiler evaporator (111), The 2-octyl (meth)acrylate (21) is withdrawn via the top of the pure boiler rectification column (11) or the pure boiler evaporator outlet of the pure boiler evaporator (111), while the high boiler containing di(meth)acrylic acid esters and oxyesters, for example alkoxyalkyl esters of (meth)acrylic acid, is withdrawn via the bottom discharge of the pure boiler rectification column (11) or the pure boiler evaporator (111).

10. The method of claim 9.

11. The pure boiler separation is followed by a high boiler separation from the mass flow produced via the bottom discharge of the pure boiler rectifier (11) or the pure boiler evaporator (111) in a high boiler rectifier unit or a high boiler evaporator unit, a high-boiler rectifier (12) located within the high-boiler rectifier unit or a high-boiler evaporator (112) within the high-boiler evaporator unit; said high boiler rectification column (12) or said high boiler evaporator (112) is operated under 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; The mass flow produced by the bottom discharge of the pure boiler rectifier (11) or the pure boiler evaporator (111) is metered into the bottom-to-center region of the high boiler rectifier (12) or into the high boiler evaporator inlet of the high boiler evaporator (112), The draw off from the top of the high boiler rectification column (12) or the high boiler evaporator (112) is condensed and fed to the area from the bottom to the center of the pure boiler rectification column (11) or the pure boiler evaporator inlet of the pure boiler evaporator (111). The method of claim 10.

12. 12. The process according to any one of claims 1 to 11, 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. 13. The process according to claim 1, wherein cyclohexane is fed to the reactor (1) of the reactor unit (24) in an amount in the range from 100 to 600% by weight, preferably in the range from 200 to 500% by weight, particularly preferably in the range from 350 to 450% by weight, based on the amount by weight of 2-octanol (13) and (meth)acrylic acid (14) fed to the reactor (1) of the reactor unit (24).

14. 14. The process according to any one of claims 1 to 13, wherein the proportion of catalyst in the reactor (1) of the reactor unit (24) is at most 10 wt.%, based on the sum of the components 2-octanol and (meth)acrylic acid present in the reactor (1) of the reactor unit (24).

15. The components entering the reactor (1) of the reactor unit (24) without the azeotropic agent cyclohexane are in 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 component: 0.10-5.00% by weight and the azeotropic agent cyclohexane is added in such an amount that a cyclohexane concentration in the reactor (1) of the reactor unit (24) is formed in the range of 10 to 90% by weight, the percentage figures by weight relating to the components present in the reactor (1) of the reactor unit (24) including the cyclohexane, And / or, in the absence of the entrainer cyclohexane and the absence of esterification water, the total components leaving the reactor (1) of the reactor unit (24), i.e., the resulting liquid reaction effluent plus the portion evaporated from the reaction mixture leaving the reactor unit (24), are in 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 component: 2.49-10.00% by weight wherein the heterogeneous azeotrope formed by the cyclohexane and the esterification water exits the reactor (1) of the reactor unit (24) at a concentration ranging from 10 to 50% by weight, these weight percent figures referring to all exiting components including the cyclohexane and the esterification water, 15. The method of any one of claims 1 to 14.

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