Device and process for manufacture of (METH)acrylates

Abstract

The invention relates to a device (1) for production of (meth)acrylates comprising at least one reactor (3), a first rectification column (5) and a second rectification column (7), wherein the at least one reactor (3) is arranged in a first fluidic connection (9) with the first rectification column (5) and an outlet (11) of the first rectification column (5) is arranged in a second fluidic connection (13) with a side feed inlet (15) of the second rectification column (7), the second rectification column (7) comprises a side withdrawal outlet (17) and at least two trays (19) as separation internals (20) and wherein at the second rectification column (7), the side feed inlet (15) is arranged above the side withdrawal outlet (17) and the side withdrawal outlet (17) is arranged between two of the at least two trays (19). The invention further relates to a process for production of (meth)acrylates.

Description

[0001] Device and process for manufacture of (meth)acrylates

[0002] Description

[0003] The present invention relates to a device for production of (meth)acrylates comprising at least one reactor, a first rectification column and a second rectification column, wherein the at least one reactor is arranged in fluidic connection with the first rectification column and an outlet of the first rectification column is connected to a side feed inlet of the second rectification column. The second rectification column comprises a side withdrawal outlet and trays as separation internals. The invention is further related to a process for production of (meth)acrylates.

[0004] (Meth)acrylates, also referred to as (meth)acrylic esters, are generally produced by esterification of (meth)acrylic acid with alcohols in the presence of esterification catalysts. Such processes are known for example from the articles Acrylic Acid and Derivatives in Kirk-Othmer Encyclopedia of Chemical Technology, Wiley, 2002, https: / / doi.org / 10.1002 / 0471238961.0103182502012105.a01.pub2 and Methacrylic Acid and Derivatives in Kirk- Othmer Encyclopedia of Chemical Technology, Wiley, 2003, https: / / doi.Org / 10.1002 / 0471238961 .1305200807181519. a01. pub2. For example, a process for production of C6-C12- alkyl (meth)acrylic esters, in particular 2-ethylhexyl acrylate, is described with focus on implemented purification steps in WO 2023 / 094252 A1. The azeotropic production of n-butyl acrylate is discussed for example in DE 10063510 A1.

[0005] Alkyl esters of (meth)acrylic acid are well known and are of significance, for example, as starting monomers for the preparation of aqueous polymer dispersions which find use, for example, as adhesives, paints or textile, leather and paper auxiliaries.

[0006] Typically, (meth)acrylates are produced by processes comprising an esterification step of esterifying (meth)acrylic acid with a feed alcohol to obtain crude (meth)acrylates and purification steps of purifying the crude (meth)acrylates to obtain the target product. To prevent polymerization of the (meth)acrylates during the production process, high- boiling polymerization inhibitors are metered at one or several points into the production plant. In the purification steps rectification columns are applied to remove side products from the product stream and / or to recycle valuables. To reach high product purities and to remove undesired polymerization inhibitors from gaseous target products, it is customary to equipe rectification columns with external droplet separators, such as centrifugal droplet separators, lamellar separators or demisters. These additional apparatuses cause an increase in plant complexity and the separation efficiency is limited. Further, the droplet separators are prone to soiling or polymer formation.

[0007] DE 19604253 A1 discloses a process for continuous preparation of alkyl esters of (meth)acrylic acid by reacting (meth)acrylic acid with alkanols having from 1 to 8 carbon atoms in the presence of an acid esterification catalyst. A reaction mixture is discharged from a reaction zone and conveyed into a distillative separation zone comprising further rectification units, where the product is separated off. A detailed design of a purifying column is not described and the pure product is fed through a demister for further purification to avoid color number problems and enable a stabilizer change.

[0008] WO 2022 / 228938 A1 is directed to a device and a method for separating liquid droplets from a gas stream by means of a centrifugal mist eliminator. The device is applied to separate stabilizers from acrylate vapor.

[0009] It is an object of the present invention to provide a device and a process for production of (meth)acrylates, wherein the product purity is enhanced and additional gas liquid separators are dispensable.

[0010] This object is achieved by a device for production of (meth)acrylates comprising at least one reactor, a first rectification column and a second rectification column, wherein the at least one reactor is arranged in a first fluidic connection with the first rectification column and an outlet of the first rectification column is arranged in a second fluidic connection with a side feed inlet of the second rectification column, the second rectification column comprises a side withdrawal outlet and at least two trays as separation internals and wherein at the second rectification column, the side feed inlet is arranged above the side withdrawal outlet and the side withdrawal outlet is arranged between two of the at least two trays. With this arrangement, at least one tray is present or located underneath the side withdrawal outlet.

[0011] The object is further achieved by a process for production of (meth)acrylates, wherein the device according to the present invention is used.

[0012] By the presence of at least one tray underneath the side withdrawal outlet, the purity of the produced (meth)acrylate is improved.

[0013] The process according to the present invention preferably comprises the following steps: a. Providing an alcohol and an acid, b. Conversion of the alcohol and the acid in presence of a catalyst to a (meth)acrylate in the at least one reactor, wherein a crude mixture containing the (meth)acrylate is obtained, c. Purification of the crude mixture in the first rectification column and the second rectification column, wherein at least part of the crude mixture is introduced into the first rectification column having a top, a purified mixture, comprising at least 80 wt.-% of the (meth)acryl ate, in particular at least 85 wt.-% of the (meth)acrylate, based on the total purified mixture, and a polymerization inhibitor, is withdrawn from the top of the first rectification column, at least part of the purified mixture is introduced into the second rectification column via the side feed inlet and a pure product, consisting to at least 98 wt.-% of the (meth)acrylate, in particular at least 99.5 wt.-% of the (meth)acrylate, based on the total pure product, is withdrawn from the second rectification column through the side withdrawal outlet.

[0014] Preferably, the pure product is withdrawn from the second rectification column through the side withdrawal outlet in a gaseous state. After withdrawal from the second rectification column the pure product is typically condensed.

[0015] By means of the at least one tray, which is present underneath the side withdrawal outlet, the purity of the pure product is improved, in particular the content of the polymerization inhibitor in the pure product is reduced. An entrainment of the polymerization inhibitor from a bottom of the second rectification column into the side withdrawal outlet is prevented. The at least one tray below the side withdrawal outlet provides a separating effect towards the polymerization inhibitor and the (meth)acrylate, such that the pure product reaches the side withdrawal outlet with higher purity. Beside the thermodynamical separation effect, the at least one tray also serve as barrier for droplets.

[0016] The term below or underneath describes a relative position in or at a column, such as the first rectification column or the second rectification column, with a smaller height and the term above describes a higher position with respect to a longitudinal direction of the column, in particular in or at a column, which is installed in an upright orientation.

[0017] Preferably, the second rectification column comprises at least three trays, more preferably at least four trays, and the side withdrawal outlet is arranged above at least two, more preferably above at least three, of the at least three trays. A higher number of trays below the side withdrawal outlet further improves the purity of the pure product stream, which is removed from the second rectification column.

[0018] Preferably, the second rectification column comprises 10 to 60, more preferably 20 to 55, trays, in particular in total. Preferably the side withdrawal outlet is arranged above two to five trays, for example above three trays. More preferably, the side withdrawal outlet is arranged at a theoretical stage in the region commencing at one or more theoretical stage above the bottommost theoretical stage and ending at 12 or less theoretical stages below the uppermost theoretical stage, of the second rectification column respectively, for example at the third theoretical stage, counted from the bottommost theoretical stage. The side feed inlet is preferably arranged at a theoretical stage in the region commencing at 3 or more theoretical stages above the bottom most theoretical stage and ending eight or less theoretical stages below the uppermost theoretical stage, for example at the fourth theoretical stage, counted from the bottommost theoretical stage, of the second rectification column, respectively.

[0019] Typically, the second rectification column comprises dual flow trays and optionally at least one chimney tray. The side withdrawal outlet can be arranged between two of the dual flow trays. In a preferred embodiment, the second rectification column comprises at least one chimney tray. Preferably, at least one of the at least two trays is a dual flow tray and at least one of the at least two trays is a chimney tray and wherein the side withdrawal outlet is arranged, in particular directly, above the dual flow tray and below the chimney tray.

[0020] Preferably, a chimney of the chimney tray extends through the dual flow tray above which the side withdrawal outlet is arranged and optionally through further dual flow trays, in particular trough all trays present below the side withdrawal outlet. With this means, the gas load of the trays beneath the chimney tray is led separately and divided between the column part above and the column part below the chimney tray, respectively, and the capacity of the trays beneath the chimney tray is increased.

[0021] In particular, the at least one tray is present or arranged between the side withdrawal outlet and a liquid phase, which is collected in the bottom of the second rectification column. Accordingly, the at least one tray is particularly present or arranged between the side withdrawal outlet and a reboiler present at the bottom of the rectification column. Particularly, the side withdrawal outlet is located at or above a lowermost separation stage. The second rectification column can possess a bypass between the tray above the side withdrawal outlet and the liquid phase, which is collected in the bottom of the second rectification column.

[0022] The first rectification column and / or the second rectification column typically comprise at least one heat exchanger. The first rectification column and / or the second rectification column preferably comprise at least one condenser.

[0023] In a preferred embodiment, a polymerization inhibitor stream is added to the first rectification column and / or the second rectification column. More preferably, the polymerization inhibitor stream enters the first rectification column and / or the second rectification column at the top of the respective column. In particular, the polymerization inhibitor stream is fed to the top of the second rectification column. Even more preferably the polymerization inhibitor stream is fed to a condenser at the first rectification column and / or the second rectification column. Preferably, the polymerization inhibitor stream comprises or consists of the polymerization inhibitor and a solvent. The solvent is preferably the alcohol and / or the (meth)acrylate. More preferably, the polymerization inhibitor stream comprises 0.1 wt.-% to 6.0 wt.-%, even more preferably 0.5 wt.-% to 3.0 wt.-%, of the polymerization inhibitor, in particular of phenothiazine and / or 4-methoxyphenol, referring to the total polymerization inhibitor stream. The polymerization inhibitor stream can be mixed with the crude mixture and / or the purified mixture, in particular with the purified mixture, for example in the condenser. For example, the polymerization inhibitor stream added to the first rectification column can comprise 0.1 wt.-% to 4.0 wt.-%, in particular 0.1 wt.-% to 2.0 wt.-%, of phenothiazine, referring to the total polymerization inhibitor stream added to the first rectification column. The polymerization inhibitor stream added to the second rectification column can comprise for example 1.5 wt.-% to 3.0 wt.-%, in particular 1 .5 wt.-% to 3.0 wt.- %, of phenothiazine and / or 4-methoxyphenol, referring to the total polymerization inhibitor stream added to the second rectification column. The at least part of the purified mixture enters the second rectification column preferably in a liquid state. Preferably, the purified mixture entering the second rectification column comprises at least 5 wt.-% of the alcohol, more preferably comprises from 5 wt.-% to 15 wt.-% of the alcohol, referring to the total purified mixture entering the second rectification column. The purified mixture entering the second rectification column comprises preferably at least 10 ppm by weight of the polymerization inhibitor, more preferably at least 10 ppm by weight of phenothiazine, referring to the total purified mixture entering the second rectification column. More preferably, the purified mixture entering the second rectification column comprises from 10 ppm by weight to 500 ppm by weight, even more preferably from 10 ppm by weight to 100 ppm by weight, of the polymerization inhibitor, for example from 10 ppm by weight to 500 ppm by weight, in particular from 10 ppm by weight to 100 ppm by weight, of phenothiazine, referring to the total purified mixture entering the second rectification column.

[0024] Preferably, the second rectification column comprises a baffle plate, which is arranged at least partly in a longitudinal direction of the second rectification column and which divides an inner space of the second rectification column into a main chamber and a sub chamber, wherein the side withdrawal outlet is arranged at the sub chamber. The sub chamber is in particular open towards the bottom of the second rectification column. Preferably, the baffle plate extends into a liquid phase, which is collected in a bottom of the second rectification column.

[0025] By the baffle plate the pure product ascending in the second rectification column to the side withdrawal outlet is spatially isolated from the purified mixture running down into the bottom of the second rectification column, thus a direct material transfer from the incoming purified mixture to the pure product is prevented. In particular, an uptake of the polymerization inhibitor from the incoming purified mixture into the pure product is avoided.

[0026] A radial cross-sectional surface area of the main chamber can be smaller or larger than a radial cross-sectional surface area of the sub chamber. A ratio between the radial cross-sectional surface area of the main chamber to the radial cross-sectional surface area of the sub chamber is preferably in range from 8.00 to 0.12, more preferably from 4.00 to 0.25.

[0027] More preferably, the sub chamber is covered by a deflected part of the baffle plate or by the chimney tray, in particular by the chimney tray arranged directly above the side withdrawal outlet.

[0028] The baffle plate, in particular the deflected part of the baffle plate and / or the chimney tray, protects and separates the side withdrawal outlet from the purified mixture, which descends within the second rectification column into the bottom of the second rectification column and which comprises the polymerization inhibitor in still enhanced amounts. By the baffle plate, in particular the deflected part of the baffle plate and / or the chimney tray, the liquid load of the trays beneath is reduced and the capacity of these trays is enhanced. Preferably, a part of the main chamber extending over the height, in particular the total height, of the sub chamber is free of separation internals. Here the purified mixture can descend freely in the second rectification column and vapors, which are not withdrawn yet, can ascend freely accordingly.

[0029] The second rectification column can comprise two or more, preferably two, baffle plates. In this embodiment, the inner space of the second rectification column is divided into two main chambers and one, preferably central, sub chamber. The side withdrawal outlet is preferably arranged at the sub chamber. The sub chamber is preferably covered by a closed plate. The part of the main chambers along the sub chamber is preferably free of separation internals as described above. Preferably, a first of the two baffle plates extents into the liquid phase, which is collected in the bottom of the second rectification column, wherein a second of the two baffle plates ends above the liquid phase, which is collected in the bottom of the second rectification column. With the baffle extending into the liquid, ascending vapor is separated tightly from descending liquid. More preferably, an upper end of the first of the two baffle plates is arranged below an upper end of the second of the two baffle plates. The upper end of the second of the two baffle plates is advantageously below a cover plate. By this arrangement, liquid can descend in a first of the two main chambers along the first of the two baffle plates, wherein only very limited amounts of vapors ascend in the first main chamber. And vapors from the bottom can ascend in a second of the two main chambers along the second of the first baffle plates. The second main chamber is in particular protected from falling liquid by the cover plate.

[0030] Preferably, a recycle pipe from the side withdrawal outlet enters the second rectification column between the same two of the at least two trays, where the side withdrawal outlet is arranged. More preferably, a recycle stream from the side withdrawal outlet is sprayed onto the tray, which is arranged below, particularly directly below, the side withdrawal outlet. With this arrangement of the recycle pipe, a wetting of the tray, which is arrange directly underneath the side withdrawal outlet, and an intimate contact of gas and liquid on this tray is ensured. The side withdrawal outlet is advantageously located above the recycle pipe.

[0031] The device according to the present application can be combined with an additional gas liquid separator, such as a demister or a centrifugal droplet separator, to improve the product purity even further. Preferably, the side withdrawal outlet is connected to a gas liquid separator, such as a demister or a centrifugal droplet separator. A storage polymerization inhibitor can be fed to the gas liquid separator. The storage polymerization inhibitor is preferably different from the polymerization inhibitor present in the purified mixture. More preferably, the storage polymerization inhibitor is selected from the group consisting of 2,4-dimethyl-6-tert-butylphenol (Topanol A), hydroquinone, butylhydroxytoluene (2,6-di-tert-butyl-p-cresol) and / or 4-methoxyphenol (MeHQ).

[0032] The (meth)acrylate is preferably formed from the acid and the alcohol. The acid is preferably (meth)acrylic acid, more preferably acrylic acid. (Meth)acrylic acid can be synthesized via known processes. For example, the (meth)acrylic acid used in the present invention may be obtained by direct oxidation of propane, propene and acrolein or of isobutane, isobutene and methacrolein.

[0033] In production of (meth)acrylic acid, crude (meth)acrylic acid can be purified by multistage crystallization or, if required, by chemical treatment with an aldehyde scavenger and distillation. The crude as well as the pure or purified (meth)acrylic acid are typically stabilized with the polymerization inhibitor or polymerization inhibitor mixtures against premature polymerization of the (meth)acrylic acid.

[0034] For the process according to the invention, alcohols containing 1 to 8 carbon atoms are preferably used in the conversion step, for example, Ci-Cs-alkanols such as methanol, ethanol, 2-ethylhexanol, tertiarbutanol, n-butanol, isobutanol and 2-octanol are particularly preferred. The alcohol is preferably methanol, ethanol, 2-ethylhexanol, tertiarbutanol, n-butanol or isobutanol, more preferably 2-ethylhexanol, n-butanol or isobutanol.

[0035] The molar ratio of the acid to the alcohol in a reaction mixture to be converted is typically in the range from 0.7 to 2.0, preferably from 0.7 to 1.7, particularly preferably from 0.7 to 1.3. Typically, the acid is used in deficiency, based on the amount of the alcohol used. For example, the molar ratio of the acid to the alcohol in the reaction mixture to be converted is in a range from 0.900 to 0.998, preferably from 0.975 to 0.995.

[0036] The conversion is typically carried out in presence of the catalyst. Preference is given to an acid catalyst, especially to a strongly acidic catalyst. Preferably, the catalyst is a mineral acid or a sulphonic acid, in particular the catalyst is chosen from a group consisting of sulphuric acid; phosphoric acid; alkyl sulfonic acid, such as methanesulfonic acid or trifluoromethanesulfonic acid; aryl sulfonic acid, such as benzenesulfonic acid, p-toluenesulfonic acid (pTSA), m- toluenesulfonic, o-toluenesulfonic acid or dodecylbenzenesulfonic acid; and mixtures thereof. In particular, the catalyst is sulphuric acid or pTSA. The catalyst content usually is 0.1 wt.-% to 10.0 wt.-%, preferably 0.3 wt.-% to 5.0 wt.-%, based on the reaction mixture.

[0037] Preferably, the (meth)acrylate is selected from the group consisting of methyl (meth)acrylate, ethyl (meth)acrylate, 2- ethylhexyl (meth)acrylate, tertiarbutyl (meth)acrylate, n-butyl (meth)acrylate and isobutyl (meth)acrylate. Even more preferably, the (meth)acrylate is selected from the group consisting of 2-ethyl hexyl acrylate (2-EHA), n-butyl acrylate (nBA) and isobutyl acrylate (IBA).

[0038] The terms "(meth)acrylic acid", "(meth)acrylic ester" or "(meth)acrylate" relate to acrylic acid or the corresponding acrylic esters or acrylates and also to methacrylic acid or the corresponding methacrylic esters or methacrylates.

[0039] Unless otherwise stated, the parts, percentages, ppm and ppb data given herein relate to parts by weight, % by weight, ppm by weight and ppb by weight. Here and throughout the specification, the terms "wt.-%" and "% by weight" are used synonymously. The process of the invention may be carried out in a continuous form or batchwise, preferably in a continuous form. The process of the invention is used for the preparation of either methacrylates or acrylates, preferably for the preparation of acrylates.

[0040] In a preferred embodiment, the process comprises at least a conversion step and at least two purification steps but may typically comprise further steps such as a catalyst removal step and a (meth)acrylic acid separation step. In particular, one of the at least two purification steps is carried out in the first rectification column and another of the at least two purification steps is carried out in the second rectification column.

[0041] The conversion is preferably carried out at a conversion temperature in a range from 70°C to 150°C, more preferably from 80°C to 130°C. Further, the conversion is preferably carried out at a conversion total pressure in a range from 100 hPa to 1020 hPa (from 100 mbar to 1020 mbar), more preferably from 200 hPa to 800 hPa (from 200 mbar to 800 mbar), even more preferably from 250 hPa to 700 hPa (from 250 mbar to 700 mbar). The conversion can be carried out in one or more reaction regions. In the case of more than one reaction regions, the conversion temperature is preferably set in such a way that it rises along the cascade.

[0042] The residence time of the reactants, i.e. the acid and the alcohol, in the conversion is preferably 1 hours to 20 hours, more preferably 2 hours to 8 hours. The residence time is understood to mean the time for which the bottoms draw volume resides in the liquid volume of the at least one reactor.

[0043] Heat can be supplied to the conversion and the at least one reactor, respectively, via internal and / or external heat exchangers of conventional design and / or via jacket heating. A usual heat transfer medium is steam. The heat is preferably supplied via external circulation evaporators with natural or forced circulation. A thorough mixing of the reaction mixture is preferably effected in a known manner, for example by stirring, pumped circulation or natural circulation.

[0044] The conversion is preferably performed in the at least one reactor. The at least one reactor can be a vessel, a column or a combination thereof. Preferably, the conversion is carried out in a reaction zone comprising one or more reaction regions, for example a reactor cascade of two to four, preferably two to three reactors. In the embodiment of the invention having a plurality of reaction regions, it is advantageous to cascade these. If more than one reaction region is created within one and the same reactor, e.g. by the use of separating sheets of metal, the number of reaction regions can also be greater than 4.

[0045] The conversion is preferably carried out in presence of the polymerization inhibitor. In general terms, a polymerization inhibitor is a substance that generally prevents the polymerization of chemical compounds. In particular, a suitable polymerization inhibitor reduces the polymerization of chemical compounds within processes for production of (meth)acrylates containing 1 to 8 carbon atoms for example within the production of 2-EHA or nBA. The polymerization inhibitor can be a mixture of different polymerization inhibitors. The polymerization inhibitor is also referred to as stabilizer. Preferably, the polymerization inhibitor is phenothiazine (PTZ), 4-hydroxy-2, 2,6,6- tetramethylpiperidin-1-oxyl (4-hydroxy-TEMPO) and / or 4-methoxyphenol (MeHQ). Most preferably, the polymerization inhibitor is phenothiazine (PTZ).

[0046] The at least one reactor can be equipped with a distillation unit. In this case, a reflux from the distillation unit is passed preferably into a first of the at least one reactor. The distillation unit typically comprises separation internals, such as trays, stacked packings and / or dumped packings. Among the trays, bubble trays, sieve trays, valve trays, Thormann trays and / or dual-flow trays are preferred; among the dumped packings, those comprising rings, coils, saddles, Raschig, Intos or Pall rings, barrel or Intalox saddles, Top-Pak etc. or braids are preferred. The distillation unit preferably comprises from 5 to 20 theoretical stages.

[0047] In a preferred embodiment, water formed during the conversion is discharged via the distillation unit together with low-boiling components, such as acetaldehyde, acrolein, water, acetic acid and / or propionic acid, and / or with solvents which form an azeotrope with water and have a boiling point at a pressure of 0.1 MPa (1 bar) of up to 130°C and which are preferably condensed in a condenser of known design. Preferably no extraneous solvent is used.

[0048] In the frame of this invention a low-boiling component, relative to the (meth)acrylate, is a substance whose boiling point is lower than the boiling point of the (meth)acrylate at 0.1 MPa (1 bar).

[0049] In the frame of this invention a high-boiling component, relative to the (meth)acrylate, is a substance whose boiling point is higher than the boiling point of the (meth)acrylate at 0.1 MPa (1 bar).

[0050] In a preferred embodiment, the conversion is carried out in the at least one reactor in the presence of an intrinsic azeotropic entrainer, in particular in the case where the (meth)acrylate is 2-ethylhexyl acrylate. The azeotropic entrainer preferably is an olefinic compound, generally an olefin having the same carbon number as the alcohol. These olefins are intrinsically generated at low rate in a dehydration side reaction and possibly subsequent isomerisation of the alcohol during the course of the conversion. In the case of 2-ethylhexyl alcohol the olefinic byproducts are typically octenes, e.g. 2-ethylhex-1 -ene, 3-methylhept-2-ene, 3-methylhept-3-ene. Generally, the azeotropic entrainer forms a low boiling azeotrope with water that distills up to the top of the distillation unit, entraining the water.

[0051] The distillate of the distillation unit is preferably condensed in a condenser. In the frame of this invention, the term distillate defines the product withdrawn from a column as side product or as top product. The condensate preferably decomposes into a water phase, which is often discharged, and an organic phase, comprising in particular the (meth)acrylate, more specifically the olefinic entrainer, 2-ethylhexanol, 2-ethylhexyl acetate and propionate. The polymerization inhibitor can be added into the condenser of the distillation unit. A polymerization inhibitor stream can be added into the distillation unit. Preferably, the polymerization inhibitor stream comprises or consists of the polymerization inhibitor and a solvent. The solvent is preferably the alcohol and / or the (meth)acrylate. More preferably, the polymerization inhibitor stream comprises 0.1 wt.-% to 6.0 wt.-%, even more preferably 0.5 wt.-% to 3.0 wt.-%, of the polymerization inhibitor, in particular of phenothiazine and / or 4-methoxy phenol, referring to the total polymerization inhibitor stream. Typically, a solution of the polymerization inhibitor in the (meth)acrylate, for example in 2-ethylhexyl acrylate, is sprayed into the condenser and / or added to a reflux into the conversion.

[0052] In a preferred embodiment, the process comprises a catalyst removal step. Preferably, the crude mixture coming from the conversion, typically comprising the (meth)acrylate, unconverted alcohol, (meth)acrylic acid, low-boiling components, acetate ester, the polymerization inhibitor, the catalyst and high-boiling components such as oxyesters, is fed into a catalyst separation column, where the crude mixture is separated into a bottom fraction and an overhead fraction.

[0053] The overhead fraction is preferably condensed and typically comprises the (meth)acrylate and low-boiling components. The overhead fraction can be partly, preferably 3 vol.-% to 10 vol.-% of the overhead fraction, returned to the catalyst separation column as reflux. The polymerization inhibitor can be added to at least parts of the overhead fraction.

[0054] At least part of the crude mixture, preferably at least part of the overhead fraction, can be fed to a (meth)acrylic acid separation step.

[0055] The bottom fraction typically comprises the catalyst, the polymerization inhibitor, the (meth)acrylate and high-boiling components. For the recuperation of the valuables contained in the bottom fraction, it can be completely or partially returned to the conversion, preferably to the first reactor if a cascade is used, and / or fed to a residue distillation and / or residue cleavage which may be present. Preferably, 1 vol.-% to 30 vol.-% of the bottom fractions are fed to the residue cleavage.

[0056] The catalyst separation column can comprise separation internals and / or one or more droplet precipitators such as a spray precipitator and is typically equipped with a circulation evaporator and a condenser. The feed is preferably fed in the bottom area of the catalyst separation column. The bottom temperature of the catalyst separation column is preferably in a range from 130°C to 160°C and the head pressure is preferably in a range from 50 hPa to 200 hPa (from 50 mbar to 200 mbar).

[0057] The first rectification column can be the catalyst removal column. Further, the process can comprise a (meth)acrylic acid removal step, in particular prior to introducing at least part, preferably part, of the purified mixture into the second rectification column, in particular upstream of the second rectification column. Further, the optional (meth)acrylic acid removal step is preferably performed after introducing at least part, preferably part, of the crude mixture into the first rectification column, in particular dowstream of the first rectification column. In a preferred embodiment, a (meth)acrylic acid removal column is installed between the first rectification column and the second rectification column. In another embodiment the (meth)acrylic acid removal column can be part of the first rectification column.

[0058] The overhead fraction from the first rectification column, in particular the catalyst removal column, can be fed into the (meth)acrylic acid removal column and separated into a bottom stream and head stream. The bottom stream is preferably largely free of (meth)acrylic acid, in particular having a (meth)acrylic acid content below 0.1 wt.-%, referring to the total bottom stream. The bottom stream preferably comprises mostly the (meth)acrylate, in particular comprises more than 90 wt.-% of the (meth)acrylate, referring to the total bottom stream. The bottom stream can also be referred to as crude (meth)acrylate. The head stream typically comprises unreacted alcohol, the (meth)acrylate, (meth)acrylic acid and low-boiling components. The temperature at the bottom of the (meth)acrylic acid removal column is usually in a range from 130°C to 160°C and the pressure at the top of the (meth)acrylic acid removal column is usually in a range from 50 hPa to 130 hPa (from 50 mbar to 130 mbar).

[0059] The (meth)acrylic acid removal column can comprise separation internals, in particular trays. Preferably, the (meth)acrylic acid removal column comprises 20 to 40 theoretical stages. The overhead fraction from the catalyst removal column is preferably fed to an upper half of the (meth)acrylic acid removal column.

[0060] The bottom stream can be partly, preferably 10 vol.-% to 20 vol.-% of the bottom stream, returned to the (meth)acrylic acid removal column as reflux. A part of the bottom stream can be recycled into the conversion.

[0061] In a preferred embodiment, the polymerization inhibitor is fed to a condenser of the (meth)acrylic acid removal column. A polymerization inhibitor stream can be added to the (meth)acrylic acid removal column. Preferably, the polymerization inhibitor stream comprises or consists of the polymerization inhibitor and a solvent. The solvent is preferably the alcohol and / or the (meth)acrylate. More preferably, the polymerization inhibitor stream comprises 0.1 wt.-% to 6.0 wt.-%, even more preferably 0.5 wt.-% to 3.0 wt.-%, of the polymerization inhibitor, in particular of phenothiazine and / or 4-methoxyphenol, referring to the total polymerization inhibitor stream. Typically, a solution of the polymerization inhibitor in the (meth)acrylate, for example in 2-ethylhexyl acrylate, is sprayed into the condenser.

[0062] The at least part of the crude mixture can be led from the at least one reactor directly or indirectly to the first rectification column. Additional separation units, such as additional columns as outline above, can be arranged between the at least one reactor and the first rectification column. In particular, the first rectification column is arranged downstream of the at least one reactor and the second rectification column is arranged downstream of the first rectification column. Particularly, an outlet of the at least one reactor is connected directly or indirectly with an inlet of the first rectification unit, for example by a pipe. The outlet of the first rectification column for the second fluidic connection is preferably located at the top of the first rectification column. The expression fluidic connection is understood to mean that generally two or more traversable components, vessels or apparatuses, such as a plurality of flow tubes by way of example, are connected to one another in such a way that a fluid can flow through these connected components. In general, there should be a sufficient degree of technical imperviousness as a fluid flows through or into. The first fluidic connection and / or the second fluidic connection is for example established by at least one pipe. The at least one pipe can be equipped with further equipment such as valves and / or measurement or control devices.

[0063] The at least part of the purified mixture can be led from the first rectification column directly or indirectly to the second rectification column. Additional separation units, such as one or more extraction column or one or more rectification column, can be arranged between the first rectification column and the second rectification column. For example, the (meth)acrylic acid removal column can be installed between the first rectification column and the second rectification column.

[0064] Preferably, the at least part, more preferably part, of the crude mixture is introduced into the first rectification column. The first rectification column can be referred to as heavies column. In another embodiment, the first rectification column can be applied as catalyst removal column. In a particularly preferred embodiment, the crude (meth)acrylate is introduced into the first rectification column. The at least part of the crude mixture introduced into the first rectification column typically comprises the (meth)acrylate, unreacted alcohol, acetate ester and low-boiling components. When the starting alcohol is 2-ethylhexanol, the low-boiling components comprise in particular 2- ethylhexanol, 2-ethylhexyl acetate and 2-ethylhexyl propionate.

[0065] The at least part of the crude mixture can be fed to the bottom of the first rectification column or to a side inlet of the first rectification column. The first rectification column can comprise separation internals such as trays, structured packing elements and / or random packing elements. Preferably, the first rectification column comprises a packing or 6 to 35 trays, in particular in total. In a preferred embodiment, the first rectification column comprises 5 to 10 trays. In another preferred embodiment, the first rectification column comprises 25 to 35 trays. Preferably, the at least part of the crude mixture is fed to the bottom, thus below the lowermost separation internal, of the first rectification column. An azeotrope can be formed during distillation in the first rectification column, in particular in the case where the (meth) acrylate is n-butyl (meth)acrylate or isobutyl (meth)acrylate. In particular, the azeotrope comprises or is the purified mixture and is withdrawn from the top of the first rectification column. The azeotrope is, in one preferred embodiment, formed for example from n-butyl acrylate, water and n-butanol.

[0066] In the frame of this invention, the bottom is understood as part of a column, which is located underneath all separation internals. The top is understood as part of a column, which is located above all separation internals. The first rectification column preferably has a rectifying section. More preferably, the rectifying section is disposed above a feed point of the at least part of the crude mixture. Preferably, the rectifying section comprises at least 8 theoretical stages, e.g. in the range from 10 to 20.

[0067] In the frame of the invention a packing is understood as solid or hollow bodies of predetermined size, shape, and configuration used as column internals to provide surface area for the liquid to allow mass transfer at the liquid-vapor interface during countercurrent flow of two phases. The packing can be a random packing or a structured packing. A random packing is understood as packing wherein individual members that do not have any particular orientation relative to each other or to the column axis. Random packings comprise in particular small, hollow structures with large surface area per unit volume that are loaded at random into a column. The random packing preferably comprises rings, helices, saddles, Raschig, Intos or Pall rings, Berl or Intalox saddles, and / or braids. A structured packing is understood as a packing wherein individual members have a specific orientation relative to each other and to the column axis. Structured packings usually are made of thin metal foil, expanded metal or woven wire screen stacked in layers or as spiral windings.

[0068] Trays are preferably selected from the group consisting of bubble-cap trays, sieve trays, valve trays, Thormann trays, chimney trays and / or dual-flow trays. A chimney tray is understood as a collector tray, in particular for, preferably only for, the liquid phase. Typically, no contact between the liquid phase and the vapor is established on a chimney tray. A dual flow tray is understood as a sieve tray, which is, in particular, free of downcomers. In particular, the liquid phase and the vapor pass the dual flow tray counter current wise through sieve holes. The dual flow tray can comprise holes of different use. The dual flow tray can comprise holes, through which the liquid phase or the vapor passes, holes, through which both the liquid phase and the vapor pass in counter current, and / or holes without flow.

[0069] The rectifying section of the first rectification column can comprise trays and / or one or more structured packings elements. Typically, the rectifying section of the first rectification column comprises trays, in particular dual flow trays. Structured packing elements are preferably made up of a multiplicity of individual layers of packing elements, such as metal sheets, expanded metals and wire fabrics, which are disposed vertically to one another in a regular structure and are usually held together in a composite by attachments such as metal wires, thin metal rods or metal sheet strips. Usually, the structured packing elements themselves have a geometric structuring, for example in the form of folds or circular holes of from about 4 mm to 6 mm in diameter. Structured packings are usually provided as individual packing layers which are then arranged in the column stacked one above the other. The packing layers often have a height of from 0.17 m to 0.30 m.

[0070] The structured packing layer may have an internal geometry which varies over its height. A structured packing is preferred in which the structured packing has one or more structured packing elements having a surface area density of at least 100 m2 / m3, preferably at least 200 m2 / m3, more preferably at least 300 m2 / m3. In one embodiment, the structured packing has a surface area density in a range from 250 m2 / m3to 350 m2 / m3. The surface area density is understood as surface area of the structured packing per unit volume of the structured packing, and usually is expressed in terms of m2 / m3of the volume occupied by the packing. The structured packing preferably has a total height of at least 6 m, preferably at least 8 m.

[0071] Heat can be supplied to the first rectification column via internal and / or external heat exchangers and / or via jacket heating, wherein the heat transfer medium used is advantageously steam. The heat is preferably supplied via external circulation evaporators with natural or forced circulation.

[0072] In general, the pressure is in a range from 40 hPa to 1500 hPa (from 40 mbar to 1500 mbar), preferably from 50 hPa to 1100 hPa (from 50 mbar to 1100 mbar), measured at the top of the first rectification column. The temperature is preferably in a range from 80°C to 180°C, more preferably from 100°C to 150°C, measured at the bottom of the first rectification column.

[0073] In a preferred embodiment, the polymerization inhibitor is added to the purified mixture at withdrawal from the first rectification column.

[0074] Part of the crude mixture leaving the reactor, in particular the distillation unit, and / or a stream withdrawn from the top of the second rectification column can be fed to an acetate column. In particular, a fraction comprising essentially the alcohol is separated from a stream comprising essentially acetate ester in the acetate column. The stream comprising essentially the alcohol is advantageously at least partly recycled to the conversion. The stream comprising essentially acetate ester is typically discharged.

[0075] Acetic ester preferably concentrates in the distillate at the first rectification column, and in the bottom of the acetate column. The feed to the acetate column preferably comprises less than 10 wt.-% of the (meth)acrylic ester, more preferably less than 5 wt.-% of the (meth)acrylic ester, referring to the total feed to the acetate column.

[0076] The acetate column can comprise separating internals such as trays, random packings or structured packings, more preferably structured packings.

[0077] Preferably, the acetate column is operated at a temperature in a range from 70°C to 170°C, more preferably from 80°C to 160°C, measured at the bottom of the acetate column. The pressure measured at the top of the acetate column is preferably in a range from 90 hPa to 1000 hPa (from 90 mbar to 1000 mbar), more preferably in a range from 100 hPa to 500 hPa (from 100 mbar to 500 mbar), even more preferably in a range from 200 hPa to 400 hPa (from 200 mbar to 400 mbar). In the process according to the present invention, at least part of the purified mixture is introduced, in particular from the first rectification column, into the second rectification column. In addition to the at least two trays, the second rectification column can comprise a packing. The packing can be a structured packing and / or a random packing. The packing is preferably arranged above the side feed inlet of the second rectification column. Typically, the packing is arranged in the second rectification column above the at least two trays, in particular above all trays present in the second rectification column. Details of the structured packings and / or random packings are described above in relation to the first rectification column.

[0078] The pressure is usually from 40 hPa to 200 hPa (from 40 mbar to 200 mbar) measured at the top of the second rectification column. The temperature measured at the bottom of the second rectification column is preferably in a range from 120°C to 180°C.

[0079] The pure product preferably comprises at least 98.0 wt.-% of the (meth)acrylate, more preferably at least 99.0 wt.-%, even more preferably at least 99.5 wt.-% and even more preferably at least 99.6 wt.-%, of the (meth)acrylate, based on the total pure product. In a preferred embodiment, the (meth)acrylate is 2-ethylhexyl acrylate and the pure product comprises less than 2 ppb by weight, more preferably less than 0.5 ppb by weight, of phenothiazine, referring to the total pure product. In another preferred embodiment, the (meth)acrylate is n-butyl acrylate and the pure product comprises less than 0.25 ppm by weight, more preferably less than 0.20 ppm by weight, of phenothiazine, referring to the total pure product.

[0080] Embodiments of the invention are illustrated in the figures and further described in the following.

[0081] The figures show:

[0082] Figure 1 a schematic view of a device and a process for manufacture of (meth)acrylates,

[0083] Figure 2 a schematic view of a first embodiment of a second rectification column of a device for manufacture of

[0084] (meth)acrylates,

[0085] Figure 3 a schematic view of a second embodiment of a second rectification column of a device for manufacture of (meth)acrylates,

[0086] Figure 4 a radial sectional view of the second embodiment of a second rectification column of a device for manufacture of (meth)acrylates,

[0087] Figure 5 a schematic view of a third embodiment of a second rectification column of a device for manufacture of (meth)acrylates, Figure 6 a radial sectional view of the third embodiment of a second rectification column of a device for manufacture of (meth)acrylates,

[0088] Figure 7 a schematic view of a fourth embodiment of a second rectification column of a device for manufacture of (meth)acrylates,

[0089] Figure 8 a schematic view of a fifth embodiment of a second rectification column of a device for manufacture of (meth)acrylates,

[0090] Figure 9 a schematic view of a sixth embodiment of a second rectification column of a device for manufacture of (meth)acrylates,

[0091] Figure 10 a schematic view of a seventh embodiment of a second rectification column of a device for manufacture of (meth)acrylates,

[0092] Figure 11 a schematic view of an eighth embodiment of a second rectification column of a device for manufacture of (meth)acrylates,

[0093] Figure 12 a radial sectional view of the seventh and eighth embodiment of a second rectification column of a device for manufacture of (meth)acrylates and

[0094] Figure 13 a diagram of the separation behavior of phenothiazine and 2-ethylhexyl acrylate.

[0095] Figure 1 shows a schematic view of a device 1 and a process for manufacture of (meth)acrylates. The device 1 for production of (meth)acrylates comprises a reactor 3, and a first rectification column 5 and a second rectification column 7. Here, the reactor 3 is present in form of a reactor cascade 49 and comprises a distillation unit 51 and a phase separator 53. The reactor 3 is arranged in a first fluidic connection 9 with the first rectification column 5. An outlet 11 of the first rectification column 5 is arranged in a second fluidic connection 13 with a side feed inlet 15 of the second rectification column 7. The second rectification column 7 comprises a side withdrawal outlet 17, wherein the side feed inlet 15 is arranged above the side withdrawal outlet 17.

[0096] An alcohol and an acid are provided in the reactor 3 and converted in presence of a catalyst to the (meth)acrylate, wherein a crude mixture containing the (meth)acrylate is obtained. The crude mixture is purified in the first rectification column 5 and the second rectification column 7. At least part of the crude mixture is introduced into the first rectification column 5 having a top 43 and a column bottom 55. A high boiler fraction is conducted from the column bottom 55 of the first rectification column 5 to a high boiler treatment unit 57. A purified mixture is withdrawn from the top 43 of the first rectification column 5 and introduced into the second rectification column 7 via the side feed inlet 15. A pure product is withdrawn from the second rectification column 7 through the side withdrawal outlet 17.

[0097] Figure 2 shows a schematic view of a first embodiment of a second rectification column 7 of a device 1 for manufacture of (meth)acrylates. The second rectification column 7 comprises a side feed inlet 15, a side withdrawal outlet 17, and separation internals 20. Part of the separation internals 20 are present in form of trays 19 and part of the separation internals 20 are present in form of packings 59. The side feed inlet 15 is arranged above the side withdrawal outlet 17 and the side withdrawal outlet 17 is arranged below all separation internals 20 and thus below all trays 19. The side withdrawal outlet 17 is connected to a gas liquid separator 41 and a recycle pipe 39 from the side withdrawal outlet 17 enters into a bottom pipe 61 of the second rectification column 7.

[0098] Figure 3 shows a schematic view of a second embodiment of a second rectification column 7 of a device 1 for manufacture of (meth)acrylates. The second rectification column 7 comprises a side feed inlet 15, a side withdrawal outlet 17, and separation internals 20. Part of the separation internals 20 are present in form of trays 19 and part of the separation internals 20 are present in form of packings 59. The side feed inlet 15 is arranged above the side withdrawal outlet 17. Further, the side withdrawal outlet 17 is arranged between two of the trays 19. The side withdrawal outlet 17 is arranged between a first tray 63 and a second tray 65. The first tray 63 and the second tray 65 are dual flow trays 21.

[0099] Further, the second rectification column 7 comprises a baffle plate 29, which is arranged in a longitudinal direction 31 of the second rectification column 7. The baffle plate 29 divides an inner space 32 of the second rectification column 7 into a main chamber 33 and a sub chamber 35. The side withdrawal outlet 17 is arranged at the sub chamber 35. The sub chamber 35 is covered by a deflected part 37 of the baffle plate 29. A part of the main chamber 33 extending over the height 37 of the sub chamber 35 is free of separation internals 20.

[0100] A recycle pipe 39 from the side withdrawal outlet 17 enters the second rectification column 7 between the same two trays 19, where the side withdrawal outlet 17 is arranged. Thus, the recycle pipe 39 from the side withdrawal outlet 17 enters the second rectification column 7 between the first tray 63 and the second tray 65.

[0101] Figure 4 shows a radial sectional view of the second embodiment of the second rectification column 7 according to figure 3 along a first intersecting plane 67. The total inner space 32 of the second rectification column 7 is divided by the baffle plate 29 into the main chamber 33 and the sub chamber 35. The main chamber 33 is free of separating internals 20 and the sub chamber 35 contains dual flow trays 21 . A radial cross-sectional surface area of the main chamber 33 is larger than a radial cross-sectional surface area of the sub chamber 35. Figure 5 shows a schematic view of a third embodiment of a second rectification column 7 of a device 1 for manufacture of (meth)acrylates. This second rectification column 7 corresponds to a large extend to the second rectification column 7 as shown in figure 3. Here, one of the trays 19 is a chimney tray 23 and the side withdrawal outlet 19 is arranged above a dual flow tray 21 and below the chimney tray 23. The sub chamber 35 is covered by the chimney tray 23.

[0102] Further, the baffle plate 29 extends into a liquid phase 45, which is collected in a bottom 47 of the second rectification column 7.

[0103] Figure 6 shows a radial sectional view of the third embodiment of the second rectification column 7 according to figure 5 along a second intersecting plane 69. Here, the radial cross-sectional surface area of the main chamber 33 is smaller than the radial cross-sectional surface area of the sub chamber 35.

[0104] Figure 7 shows a schematic view of a fourth embodiment of a second rectification column 7 of a device 1 for manufacture of (meth)acrylates. The second rectification column 7 comprises a side feed inlet 15, a side withdrawal outlet 17, and separation internals 20. The side feed inlet 15 is arranged above the side withdrawal outlet 17. The side withdrawal outlet 17 is arranged between two trays 19. The side withdrawal outlet 17 is arranged between a first tray 63 and a second tray 65, wherein the first tray 63 is a chimney tray 23 and the second tray 65 is a dual flow tray 21.

[0105] A recycle pipe 39 from the side withdrawal outlet 17 enters the second rectification column 7 between the same two trays 19, where the side withdrawal outlet 17 is arranged. Thus, the recycle pipe 39 from the side withdrawal outlet 17 enters the second rectification column 7 between the first tray 63 and the second tray 65.

[0106] Further, the second column 7 possesses a bypass 71 between the first tray 63 and a liquid phase 45, which is collected in a bottom 47 of the second rectification column 7.

[0107] Figure 8 shows a schematic view of a fifth embodiment of a second rectification column 7 of a device 1 for manufacture of (meth)acrylates. The second rectification column 7 comprises a side feed inlet 15, a side withdrawal outlet 17, and separation internals 20. The side feed inlet 15 is arranged above the side withdrawal outlet 17. The side withdrawal outlet 17 is arranged between two of the trays 19, which are both dual flow trays 21.

[0108] The side withdrawal outlet 17 is connected to a gas liquid separator 41 and a recycle pipe 39 from the side withdrawal outlet 17 enters a bottom pipe 61 of the second rectification column 7.

[0109] Figure 9 shows a schematic view of a sixth embodiment of a second rectification column 7 of a device 1 for manufacture of (meth)acrylates. This second rectification column 7 corresponds to a large extend to the second rectification column 7 as shown in figure 7. Here, a chimney 25 of the chimney tray 23 extends through the dual flow tray 21, 27 above which the side withdrawal outlet 17 is arranged and through all dual flow trays 21 below the side withdrawal outlet 17.

[0110] Figure 10 shows a schematic view of a seventh embodiment of a second rectification column 7 of a device 1 for manufacture of (meth)acrylates. This second rectification column 7 partly corresponds to the second rectification column 7 as shown in figure 3. Here, the second rectification column 7 comprises two baffle plates 29 and an inner space 32 of the second rectification column 7 is divided into two main chambers 33 and a central sub chamber 35. The side withdrawal outlet 17 is arranged at the central sub chamber 35. The central sub chamber 35 is covered by a closed plate 36. The part of the main chambers 33 along the central sub chamber 35 is free of separation internals 20.

[0111] Figure 11 shows a schematic view of an eighth embodiment of a second rectification column 7 of a device 1 for manufacture of (meth)acrylates. The second rectification column 7 comprises two baffle plates 29 and an inner space 32 of the second rectification column 7 is divided into two main chambers 33 and a central sub chamber 35, as also shown in figure 10. The side withdrawal outlet 17 is arranged at the central sub chamber 35. The central sub chamber 35 is covered by a closed plate 36. The part of the main chambers 33 along the central sub chamber 35 is free of separation internals 20. A first of the two baffle plates 29 extents into the liquid phase 45, which is collected in the bottom 47 of the second rectification column 7, wherein a second of the two baffle plates 29 ends above the liquid phase 45, which is collected in the bottom 47 of the second rectification column 7. An upper end of the first of the two baffle plates 29, 38 is arranged below an upper end of the second of the two baffle plates 29, 40. The upper end of the second of the two baffle plates 29, 40 is located below a cover plate 42.

[0112] Figure 12 shows a radial sectional view of the seventh and eighth embodiment, respectively, of the second rectification column 7 according to figures 10 and 11, respectively. The total inner space 32 of the second rectification column 7 is divided by the two baffle plates 29 into the main chambers 33 and the sub chamber 35. The main chambers 33 are free of separating internals 20 and the sub chamber 35 contains dual flow trays 21 . In the shown embodiment, a radial cross-sectional surface area of the main chambers 33 together is smaller than a radial cross-sectional surface area of the sub chamber 35.

[0113] Examples and comparative examples

[0114] Figure 13 shows a diagram of the separation behavior of phenothiazine (PTZ) and 2-ethylhexyl acrylate. A liquid phase according to the liquid phase in the bottom of the second rectification column and essentially comprising 2- ethylhexyl acrylate was provided. Different amounts of phenothiazine were added to different portions of the liquid phase. Each portion was evaporated in a single stage and the resulting distillates were analyzed. On an abscissa 73 the concentration of PTZ in the different portions of the liquid phase is represented in ppm. On an ordinate 75 the concentration of PTZ in the respective distillates is represented in ppm. A graph 77 represents simulated data for a distillation at 100 hPa (100 mbar) and 140°C. nBA plant

[0115] N-butyl acrylate (nBA) can be produced on an industrial scale by an acid-catalyzed esterification of acrylic acid with n-butanol. One corresponding process is disclosed in document DE 10063510 A1.

[0116] Comparative example 1 :

[0117] According to comparative example 1, the pure product was withdrawn from the second rectification column underneath all separation internals as shown in figure 2. The feed rate of the purified mixture into the second rectification column was 19657 kg / h and 17019 kg / h of the pure product were withdrawn.

[0118] The composition of the purified mixture fed via the side feed inlet in the second rectification column was, referring to the total purified mixture: n-butanol 7.35 wt.-% n-butyl acetate 1.07 wt.-% di-n-butyl ether 0.08 wt.-% n-butyl acrylate 90.00 wt.-% 4-methoxyphenol 4.89 ppb by weight phenothiazine 16.13 ppm by weight residuals

[0119] The composition of the gaseous pure product withdrawn from the side withdrawal outlet at the second rectification column was, referring to the total pure product: n-butanol 0.28 ppm by weight n-butyl acetate 405.89 ppm by weight di-n-butyl ether 485.31 ppm by weight n-butyl acrylate 99.78 wt.-% 4-methoxyphenol 0.15 ppm by weight phenothiazine 2.25 ppb by weight residuals The content of phenothiazine was reduced over the second rectification column to 2.25 ppb (parts per billion) by weight comprised in the pure product.

[0120] Example 1 :

[0121] According to example 1, two dual flow trays were present below the side withdrawal outlet from which the pure product was withdrawn from the second rectification column, as illustrated in principle by figure 8. The feed rate of the purified mixture to the second rectification column was 17127 kg / h and 14130 kg / h of the pure product were withdrawn.

[0122] The composition of the purified mixture fed via the side feed inlet into the second rectification column was, referring to the total purified mixture: n-butanol 10.77 wt.-% n-butyl acetate 0.81 wt.-% di-n-butyl ether 0.13 wt.-% n-butyl acrylate 86.41 wt.-% 4-methoxyphenol 1 .83 ppm by weight phenothiazine 12.74 ppm by weight residuals

[0123] The composition of the gaseous pure product withdrawn from the side withdrawal outlet at the second rectification column was, referring to the total pure product: n-butanol 1.45 ppm by weight n-butyl acetate 0.09 wt.-% di-n-butyl ether 0.12 wt.-% n-butyl acrylate 99.66 wt.-% 4-methoxyphenol 809.84 ppb by weight phenothiazine 0.19 ppb by weight residuals

[0124] The content of phenothiazine was reduced over the second rectification to 0.19 ppb by weight comprised in the pure product.

[0125] 2-EHA plant 2-Ethylhexyl acrylate (2-EHA) can be produced on an industrial scale by an acid-catalyzed esterification of acrylic acid with 2-ethylhexanol. One corresponding process is disclosed in document DE 19604253 A1.

[0126] Comparative example 2:

[0127] According to comparative example 2, the pure product was withdrawn from the second rectification column, also referred to as finishing column, underneath all separation internals as shown in figure 2. The feed rate of the purified mixture to the second rectification column was 19800 kg / h and 13676 kg / h of the pure product were withdrawn.

[0128] The composition of the purified mixture fed via the side feed inlet into the second rectification column was, referring to the total purified mixture:

[0129] 2-ethylhexanol 6.00 wt.-% n-ethylhexyl acetate 0.77 wt.-% 2-ethylhexyl acrylate 84.87 wt.-% 4-methoxyphenol 0.76 ppm by weight phenothiazine 54.09 ppm by weight residuals

[0130] The composition of the gaseous pure product withdrawn from the side withdrawal outlet at the second rectification column was, referring to the total pure product:

[0131] 2-ethylhexanol 0.12 wt.-% n-ethylhexyl acetate 0.15 wt.-% 2-ethylhexyl acrylate 99.59 wt.-% 4-methoxyphenol 3.94 ppm by weight phenothiazine 0.29 ppm by weight residuals

[0132] The content of phenothiazine was reduced over the second rectification column to 0.29 ppm by weight comprised in the pure product.

[0133] Comparative example 3:

[0134] According to comparative example 3, the pure product was withdrawn from the second rectification column, also referred to as finishing column, underneath all separation internals as shown in figure 2. The feed rate of the purified mixture to the second rectification column was 14014 kg / h and 9567 kg / h of the pure product were withdrawn. The composition of the purified mixture fed via the side feed inlet into the second rectification column was, referring to the total purified mixture:

[0135] 2-ethylhexanol 7.80 wt.-% n-ethylhexyl acetate 0.34 wt.-% 2-ethylhexyl acrylate 86.61 wt.-% 4-methoxyphenol 56.30 ppb by weight phenothiazine 59.80 ppm by weight residuals

[0136] The composition of the gaseous pure product withdrawn from the side withdrawal outlet at the second rectification column was, referring to the total pure product:

[0137] 2-ethylhexanol 0.08 wt.-% n-ethylhexyl acetate 0.16 wt.-% 2-ethylhexyl acrylate 99.72 wt.-% 4-methoxyphenol 0.69 ppm by weight phenothiazine 0.19 ppm by weight residuals

[0138] The content of phenothiazine was reduced over the second rectification to 0.19 ppm by weight comprised in the pure product.

[0139] Example 2:

[0140] Example 2 is based on the same process as comparative example 3, with the difference that here two dual flow trays were present below the side withdrawal outlet. Thus, the pure product was withdrawn from the second rectification column as illustrated in principle by figure 8. The feed rate of the purified mixture to the second rectification column accounted to 13928 kg / h and 9567 kg / h of the pure product were withdrawn.

[0141] The composition of the purified mixture fed via the side feed inlet into the second rectification column was, referring to the total purified mixture:

[0142] 2-ethylhexanol 7.79 wt.-% n-ethylhexyl acetate 0.33 wt.-% 2-ethylhexyl acrylate 86.72 wt.-% 4-methoxyphenol 128.80 ppb by weight phenothiazine 60.10 ppm by weight residuals The composition of the gaseous pure product withdrawn from the side withdrawal outlet at the second rectification column was, referring to the total pure product:

[0143] 2-ethylhexanol 0.08 wt.-% n-ethylhexyl acetate 0.16 wt.-% 2-ethylhexyl acrylate 99.74 wt.-% 4-methoxyphenol 0.64 ppm by weight phenothiazine 0.01 ppm by weight residuals The content of phenothiazine was reduced over the second rectification to 0.01 ppm by weight comprised in the pure product.

[0144] List of reference numerals

[0145] I device

[0146] 3 reactor

[0147] 5 first rectification column

[0148] 7 second rectification column

[0149] 9 first fluidic connection

[0150] I I outlet

[0151] 13 second fluidic connection

[0152] 15 side feed inlet

[0153] 17 side withdrawal outlet

[0154] 19 tray

[0155] 20 separation internal

[0156] 21 dual flow tray

[0157] 23 chimney tray

[0158] 25 chimney

[0159] 27 dual flow tray above which the side withdrawal outlet 17 is arranged

[0160] 29 baffle plate

[0161] 31 longitudinal direction

[0162] 32 inner space

[0163] 33 main chamber

[0164] 35 sub chamber

[0165] 36 closed plate

[0166] 37 deflected part

[0167] 38 upper end of the first of the two baffle plates 29

[0168] 39 recycle pipe

[0169] 40 upper end of the second of the two baffle plates 2941 gas liquid separator

[0170] 42 cover plate

[0171] 43 top

[0172] 45 liquid phase

[0173] 47 bottom

[0174] 49 reactor cascade

[0175] 51 distillation unit

[0176] 53 phase separator

[0177] 55 column bottom

[0178] 57 high boiler treatment unit

[0179] 59 packing 61 bottom pipe

[0180] 63 first tray

[0181] 65 second tray

[0182] 67 first intersecting plane 69 second intersecting plane

[0183] 71 bypass

[0184] 73 abscissa

[0185] 75 ordinate

[0186] 77 graph

Claims

Claims1. Device (1) for production of (meth)acrylates comprising at least one reactor (3), a first rectification column (5) and a second rectification column (7), wherein the at least one reactor (3) is arranged in a first fluidic connection (9) with the first rectification column (5) and an outlet (11) of the first rectification column (5) is arranged in a second fluidic connection (13) with a side feed inlet (15) of the second rectification column (7), the second rectification column (7) comprises a side withdrawal outlet (17) and at least two trays (19) as separation internals (20) and wherein at the second rectification column (7), the side feed inlet (15) is arranged above the side withdrawal outlet (17) and the side withdrawal outlet (17) is arranged between two of the at least two trays (19).

2. Device (1) according to claim 1, wherein the second rectification column (7) comprises at least three trays (19) and the side withdrawal outlet (17) is arranged above at least two of the at least three trays (19).

3. Device (1) according to claim 1 or 2, wherein the second rectification column (7) comprises 10 to 60 trays (19).

4. Device (1) according to any of claims 1 to 3, wherein at least one of the at least two trays (19) is a dual flow tray (21) and at least one of the at least two trays (19) is a chimney tray (23) and wherein the side withdrawal outlet (19) is arranged, in particular directly, above the dual flow tray (21) and below the chimney tray (23).

5. Device (1) according to claim 4, wherein a chimney (25) of the chimney tray (23) extends through the dual flow tray (21, 27) above which the side withdrawal outlet (17) is arranged and optionally through further dual flow trays (21).

6. Device (1) according to any of claims 1 to 5, wherein the second rectification column (7) comprises a baffle plate (29), which is arranged at least partly in a longitudinal direction (31) of the second rectification column (7) and which divides an inner space (32) of the second rectification column (7) into a main chamber (33) and a sub chamber (35), wherein the side withdrawal outlet (17) is arranged at the sub chamber (35).

7. Device (1) according to claim 6, wherein the sub chamber (35) is covered by a deflected part (37) of the baffle plate (29) or by the chimney tray (23).

8. Device (1) according to claim 6 or 7, wherein a part of the main chamber (33) extending over the height (37) of the sub chamber (35) is free of separation internals (20).

9. Device (1) according to any of claims 1 to 8, wherein a recycle pipe (39) from the side withdrawal outlet (17) enters the second rectification column (7) between the same two of the at least two trays (19), where the side withdrawal outlet (17) is arranged.

10. Device (1) according to any of claims 1 to 9, wherein the side withdrawal outlet (17) is connected to a gas liquid separator (41), such as a demister or a centrifugal droplet separator.11 . Process for production of (meth)acrylates, wherein the device (1) according to any of claims 1 to 10 is used.

12. Process according to claim 11, wherein the process comprises the following steps: a. Providing an alcohol and an acid, b. Conversion of the alcohol and the acid in presence of a catalyst to a (meth)acrylate in the at least one reactor (3), wherein a crude mixture containing the (meth)acrylate is obtained, c. Purification of the crude mixture in the first rectification column (5) and the second rectification column (7), wherein at least part of the crude mixture is introduced into the first rectification column (5) having a top (43), a purified mixture, comprising at least 80 wt.-% of the (meth)acrylate, in particular at least 85 wt.-% of the (meth)acrylate, based on the total purified mixture, and a polymerization inhibitor, is withdrawn from the top (43) of the first rectification column (5), at least part of the purified mixture is introduced into the second rectification column (7) via the side feed inlet (15) and a pure product, consisting to at least 98 wt.-% of the (meth)acrylate, in particular at least 99.5 wt.-% of the (meth)acrylate, based on the total pure product, is withdrawn from the second rectification column (7) through the side withdrawal outlet (17).

13. Process according to claim 12, wherein the pure product is withdrawn from the second rectification column (7) through the side withdrawal outlet (17) in a gaseous state.

14. Process according to claim 11 or 12, wherein the second rectification column (7) comprises a baffle plate (29), which is arranged at least partly in a longitudinal direction (31) of the second rectification column (7) and which divides an inner space (32) of the second rectification column (7) into a main chamber (33) and a sub chamber (35), wherein the side withdrawal outlet (17) is arranged at the sub chamber (35).

15. Process according to any of claims 12 to 14, wherein the baffle plate (29) extends into a liquid phase (45), which is collected in a bottom (47) of the second rectification column (7).

16. Process according to any of claims 11 to 15, wherein the polymerization inhibitor is phenothiazine (PTZ), 4- hydroxy-2,2,6,6-tetramethylpiperidin-1-oxyl (4-hydroxy-TEMPO) and / or 4-methoxyphenol (MeHQ).

17. Process according to any of claims 11 to 16, wherein the (meth)acrylate is selected from the group consisting of methyl (meth)acrylate, ethyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, tertiarbutyl (meth)acrylate, n-butyl (meth)acrylate and isobutyl (meth)acrylate.

Images