Continuous process for preparing n-butyl (meth) acrylates with catalyst reflux

Abstract

The present invention relates to a process for the continuous production of n-butyl (meth) acrylates by reacting (meth) acrylic acid with n-butanol in the presence of an acidic catalyst and a polymerization inhibitor, the process according to a first embodiment comprising the following steps: performing esterification in a reactor (A) having a column (B) placed on top thereof, wherein the components (meth) acrylic acid and n-butanol are introduced in a molar ratio in the range of 1.0: 1.0 to 1.0: 2.0, preferably in the range of 1.0: 1.1 to 1.0: 1.5, and wherein the esterification takes place at a temperature in the range of 80 DEG C to 150 DEG C, preferably in the range of 100 DEG C to 130 DEG C, and at an absolute pressure in the range of 0.2 bar to 5.0 bar, preferably in the range of 0.4 bar to 1.5 bar, the invention relates to a method for producing n-butyl (meth) acrylate, comprising the steps of:-separating n-butyl (meth) acrylate from n-butyl (meth) acrylate by means of a phase separator (D) so as to obtain a resulting reaction effluent (6) and a vapor stream at the top of a column (B),-discharging the vapor stream at the top of the column (B),-condensing the vapor stream in a condenser (C), forming an organic phase rich in n-butyl (meth) acrylate and an aqueous phase,-continuously separating the organic phase from the aqueous phase by means of a phase separator (D), feeding the resulting reaction effluent (6) into a rectification column (E), separating azeotropes in the rectification column (E): a) water and n-butyl (meth) acrylate, b) n-butanol and n-butyl (meth) acrylate, c) n-butanol and water, d) n-butanol, n-butyl (meth) acrylate and water, and e) n-butanol and n-butyl (meth) acrylate. Wherein the rectification column (E) is operated at a bottom temperature in the range of 80 DEG C to 150 DEG C, a top temperature in the range of 70 DEG C to 130 DEG C and an absolute pressure in the range of 0.2 bar to 5 bar, preferably in the range of 0.4 bar to 1.5 bar, discharging a gas stream enriched by azeotrope at the top of the rectification column (E), condensing the gas stream in a condenser (F), the invention relates to a method for separating n-butyl (meth) acrylate, comprising the steps of forming an organic phase rich in n-butyl (meth) acrylate and an aqueous phase, continuously separating the organic phase from the aqueous phase by means of a phase separator (G), continuously discharging at least a portion of the organic phase from the phase separator (G), the discharged portion of the organic phase rich in n-butyl (meth) acrylate being a crude product stream (15), discharging a reboiler bottom discharge (23) from the bottom of the rectification column (E), the mass flow ratio between the reboiler bottom discharge (23) and the (meth) acrylic acid fed as raw material to the reactor (A) being in the range of 0.5 to 5, feeding a reboiler partial flow (7) of the discharged reboiler bottom discharge (23) into a mixer (H), wherein the mass flow ratio between the reboiler partial flow (7) and the reboiler bottom discharge (23) is in the range of 0.01 to 0.50, preferably in the range of 0.05 to 0.08,-feeding the mixture (10) produced from the mixer (H) into a downstream extraction phase separator (I),-continuously separating the mixture (10) in the extraction phase separator (I), obtaining an organic refined product (11) and a catalyst-containing aqueous extract (12), wherein the aqueous extract (12) is at least partially returned to the reactor (A) and / or the rectification column (E), and wherein external water (19) is fed to the mixer (H), and wherein the mass flow ratio between the mass flow of the external water (19) and the reboiler partial flow (7) of the discharged reboiler bottom discharge (23) is in the range of 0.08 to 0.50, preferably in the range of 0.10 to 0.30.

Description

[0001] The present invention relates to a method for continuously preparing n-butyl (meth)acrylate by reacting (meth)acrylic acid with n-butanol in the presence of an acidic catalyst and a polymerization inhibitor.

[0002] n-Butyl (meth)acrylate is particularly advantageously used for the production of contact lenses or as a crosslinker or adhesion promoter for dispersions which are preferably used as adhesives, coatings, pigments, for example also as printing inks, or textile, leather or paper auxiliaries, and in hardenable coatings.

[0003] When alcohols are esterified with acids, typical equilibrium reactions usually occur, which are catalyzed by strong acids and lead to the separation of esterification water as a typical condensation reaction. The esterification equilibrium is usually shifted toward the positive reaction direction by removing the esterification water from the reaction mixture, thereby increasing the conversion rate of the target product.

[0004] Acidic catalysts typically used in the esterification reaction include inorganic acids such as sulfuric acid, organic acids such as alkylsulfonic acids, ion exchange resins, and the like.

[0005] The separation of the water of esterification can be carried out by distillation as part of an azeotrope which typically also includes the target ester. Typically, the esterification reaction is carried out in such a way that the water of esterification is continuously removed from the reaction mixture, wherein, however, the main amount of the target ester formed remains in the reaction mixture.

[0006] An example of such an esterification is the separation of the esterification water by distillation by adding an organic solvent as an azeotropic entrainer. Alcohols used in excess can also be used as such an azeotropic entrainer.

[0007] One variant for preparing n-butyl (meth)acrylate is to separate the water of esterification by distillation as a component of the heterogeneous azeotrope of n-butyl (meth)acrylate / n-butanol / water, wherein n-butanol and / or n-butyl (meth)acrylate are at least partially recirculated as organic phase to the esterification.

[0008] A challenge of this process is that the esterification water formed in the esterification must be at least partially removed from the process. Furthermore, the removed catalyst portion is typically burned off, which results in undesirable SO formation when, for example, sulfuric acid or sulfonic acid is used. x emission.

[0009] EP 0 795 536 A1 (BASF AG) discloses a process for the continuous preparation of alkyl esters of (meth)acrylic acid with a recirculation of an acidic catalyst into the reaction zone of the reactor. In this document, the recirculation of the acidic catalyst is described only for the alkyl ester 2-ethylhexyl acrylate (2-EHA). The applicability of this technology to the preparation of n-butyl acrylate and the subsequent esterification reaction to give the alkyl ester n-butyl acrylate after specific purification and the transferability to other physical process conditions are not disclosed.

[0010] WO 2012 / 026661 A1 (LG Chem, LTD.) discloses a method for the continuous preparation of alkyl (meth) acrylates, in particular n-butyl acrylate. In this method, an organic acid catalyst is refluxed to the reaction zone of the reactor. However, the reflux is limited to the case where the mass flow at the bottom outlet of the distillation column is already two-phase. Therefore, the mass flow at the bottom outlet of the distillation column already contains an organic phase and an aqueous phase.

[0011] Therefore, the object of the present invention is to provide a continuous process for preparing n-butyl (meth) acrylate with catalyst reflux, so as to make it possible to improve the catalyst recovery rate during the preparation of n-butyl (meth) acrylate using an acidic catalyst, thereby also reducing the amount of catalyst removed.

[0012] Another object is to carry over as little water as possible during the esterification and distillative purification in order to be able to design the process to be energy-efficient. Consequently, the formation of secondary components in the process is also reduced, since the reaction mixture is exposed to lower temperatures in the process.

[0013] Furthermore, the object of higher conversion and yield of n-butyl (meth)acrylate is achieved.

[0014] These objects are achieved according to the invention by claim 1 or alternatively by claim 2. The invention also relates to preferred embodiments of the method according to claims 3 to 14.

[0015] In this document, the reference numerals in brackets are used to improve understanding during reading. The reference numerals in brackets are not restrictive, but each represents a possible example among multiple implementation possibilities.

[0016] The process of the invention is based on the raw materials n-butanol and (meth)acrylic acid. (Meth)acrylic acid is understood in this context to mean a (meth)acrylic acid mass having preferably at least 98 wt %, more preferably at least 99.5 wt % of (meth)acrylic acid, in addition preferably at most 0.2 wt % of water, and preferably at most 0.03 wt % of acetic acid, propionic acid and isobutyric acid, respectively. Preferably, a mass of n-butanol having at least 99.5 wt % of n-butanol, at most 0.05 wt % of n-butyraldehyde, at most 0.02 wt % of dibutyl ether, at most 0.1 wt % of other alcohols and at most 0.05 wt % of water is fed. The color value is preferably a maximum of APHA5, the acid value is preferably a maximum of 0.03 mgKOH / g.

[0017] Suitable polymerization inhibitors, which act as stabilizers, may be, for example, N-oxides (nitroxides or N-oxide radicals, i.e. compounds having at least one NO group), such as 4-hydroxy-2,2,6,6-tetramethylpiperidine-N-oxide (HO-TEMPO), 4-oxo-2,2,6,6-tetramethylpiperidine-N-oxide, 4-acetoxy-2,2,6,6-tetramethylpiperidine-N-oxide, 2,2,6,6-tetramethylpiperidine-N-oxide, bis(1-oxy-2,2,6,6-tetramethylpiperidin-4-yl)sebacate, 4,4',4"-tris(2,2,6,6-tetramethylpiperidin-N -oxide) phosphate or 3-oxo-2,2,5,5-tetramethylpyrrolidine-N-oxide, etc.; monohydric or polyhydric phenols, which may have one or more alkyl groups as appropriate, such as alkylphenols, such as o-, m- or p-cresol (methylphenol), 2-tert-butylphenol, 4-tert-butylphenol, 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, etc.; hydroxyphenols, For example, catechol (1,2-dihydroxybenzene) or benzoquinone, etc.; aminophenols, such as p-aminophenol, etc.; nitrosophenols, such as p-nitrosophenol, etc.; 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, etc.; tocopherols, such as α-tocopherol and 2,3-dihydro-2,2-dimethyl-7-hydroxybenzofuran (2,2-dimethyl-7-hydroxycoumarin), etc., aromatic amines, such as N,N-diphenylamine or N-nitroso-diphenylamine, etc.; phenylenediamines, such as N,N'-dialkyl p-phenylenediamine, etc., wherein the alkyl The radical groups may be the same or different and each independently consists of 1 to 4 carbon atoms and may be straight chain or branched, such as N,N'-dimethyl-p-phenylenediamine or N,N'-diethyl-p-phenylenediamine, etc., hydroxylamines such as N,N-diethylhydroxylamine, etc., imines such as methylethylimine or methyl violet, etc., sulfonamides such as N-methyl-4-toluenesulfonamide or N-tert-butyl-4-toluenesulfonamide, etc., oximes such as aldoxime, ketoxime or acyloxime, such as diethylketoxime, methylethylketoxime or salicylic acid oxime, etc., phosphorus-containing compounds such as triphenylphosphine, triphenylphosphate, triethylphosphate, hypophosphorous acid or alkyl esters of phosphoric acid, etc.; sulfur-containing compounds such as diphenyl sulfide or phenothiazine, etc.;Metal salts, such as copper or manganese, cerium, nickel, chromium salts, for example copper or manganese, cerium, nickel, chromium chlorides, sulfates, salicylates, p-toluenesulfonates, acrylates or acetates, for example copper acetate, copper(II) chloride, copper salicylate, cerium(III) acetate or cerium(III) ethylhexanoate, or mixtures thereof;

[0018] Preferably, at least one compound from the following group is added as polymerization inhibitor or polymerization inhibitor mixture: hydroquinone, hydroquinone monomethyl ether, phenothiazine, 4-hydroxy-2,2,6,6-tetramethylpiperidine-N-oxide, 4-oxo-2,2,6,6-tetramethylpiperidine-N-oxide, bis(1-oxido-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.

[0019] Particular preference is given to using phenothiazine (PTZ) and / or hydroquinone monomethyl ether (MEHQ) as polymerization inhibitors.

[0020] Very particularly preferably, PTZ is used as polymerization inhibitor during the esterification and / or distillation.

[0021] Preferably, the polymerization inhibitor is dissolved in one or more liquid organic compounds. The organic compound is preferably n-butanol and / or n-butyl (meth)acrylate.

[0022] As esterification catalysts, customary mineral acids and sulfonic acids are used, preferably sulfuric acid, phosphoric acid, alkylsulfonic acids (eg methanesulfonic acid, trifluoromethanesulfonic acid) and arylsulfonic acids (eg benzenesulfonic acid, p-toluenesulfonic acid or dodecylbenzenesulfonic acid) or mixtures thereof.

[0023] Sulfuric acid, methanesulfonic acid, p-toluenesulfonic acid, m-toluenesulfonic acid, o-toluenesulfonic acid or mixtures thereof are particularly preferred.

[0024] Very particular preference is given to using p-toluenesulfonic acid as esterification catalyst.

[0025] The acidic catalyst is in particular a homogeneous catalyst. Preferably sulfuric acid, phosphoric acid, alkylsulfonic acids (such as methanesulfonic acid, trifluoromethanesulfonic acid) and arylsulfonic acids (such as benzenesulfonic acid, p-toluenesulfonic acid or dodecylbenzenesulfonic acid) or mixtures thereof are used as acidic catalysts, particularly preferably p-toluenesulfonic acid.

[0026] According to the present invention, a method for continuously preparing n-butyl (meth)acrylate by reacting (meth) acrylic acid with n-butanol in the presence of an acidic catalyst and a polymerization inhibitor comprises the following steps:

[0027] The esterification is carried out in a reactor (A) having a column (B) mounted on top thereof, wherein the ratio of the reaction mixture to the reaction mixture is in the range of 1.0:1.0 to 1.0:2.0, preferably in the range of 1.0:

[0028] The components (meth)acrylic acid and n-butanol are fed in a molar ratio in the range of 1.1 to 1.0:1.5, and wherein the esterification takes place at a temperature in the range of 80° C. to 150° C., preferably in the range of 100° C. to 130° C. and at an absolute pressure in the range of 0.2 bar to 5.0 bar, preferably in the range of 0.4 bar to 1.5 bar, so that a reaction effluent (6) and a steam stream are obtained at the top of the column (B),

[0029] a vapor stream is discharged at the top of the column (B),

[0030] condensing the vapor stream in a condenser (C) to form an organic phase and an aqueous phase,

[0031] · Continuous separation of the organic phase from the aqueous phase by means of a phase separator (D),

[0032] The reaction effluent (6) is fed into a distillation column (E),

[0033] Separation of azeotropes in a distillation column (E):

[0034] a) water and n-butyl (meth)acrylate,

[0035] b) n-butyl alcohol and n-butyl (meth)acrylate,

[0036] c) n-butanol and water,

[0037] d) n-butanol, n-butyl (meth)acrylate and water,

[0038] wherein the distillation column (E) is operated with a bottom temperature in the range of 80° C. to 150° C., a top temperature in the range of 70° C. to 130° C. and an absolute pressure in the range of 0.2 bar to 5 bar,

[0039] At the top of the distillation column (E), a gas stream enriched with azeotropes is discharged,

[0040] condensing the gas stream in a condenser (F) to form an organic phase rich in n-butyl (meth)acrylate and an aqueous phase,

[0041] · Continuous separation of the organic phase from the aqueous phase by means of a phase separator (G),

[0042] continuously removing at least a portion of the organic phase from the phase separator (G), wherein the portion of the organic phase which is rich in n-butyl (meth)acrylate is the crude product stream (15),

[0043] a reboiler bottoms discharge (23) is discharged from the bottom of the rectification column (E), wherein the mass flow ratio between the reboiler bottoms discharge (23) and the (meth)acrylic acid (1) fed as a raw material to the reactor (A) is in the range of 0.5 to 5,

[0044] feeding a reboiler part stream (7) of the discharged reboiler bottoms discharge (23) into a mixer (H), wherein the mass flow ratio between the reboiler part stream (7) and the reboiler bottoms discharge (23) is in the range from 0.01 to 0.50, preferably in the range from 0.05 to 0.08,

[0045] The mixture (10) produced from the mixer (H) is fed to a downstream extract phase separator (I),

[0046] Continuously separating the mixture (10) in an extract phase separator (I) to obtain an organic concentrate (11) and an aqueous extract (12) containing the catalyst, wherein the aqueous extract (12) is at least partially refluxed to the reactor (A) and / or the distillation column (E),

[0047] In this case, external water (19) is fed to the mixer (H), and the mass flow ratio between the mass flow of the external water (19) and the reboiler part flow (7) of the discharged reboiler bottom discharge (23) is in the range of 0.08 to 0.50, preferably in the range of 0.10 to 0.30.

[0048] Surprisingly, it was found that by supplying external water (19) to the mixer (H), after the startup phase of the plant, there is always a two-phase separation of the resulting mixture (10). Therefore, in all operating conditions occurring in the plant, reflux of the catalyst is always possible. In addition, the moisture content in the plant, such as in particular the moisture content in the reactor (A) or the distillation column (E), can also be kept as low as possible. In addition, the method is therefore more energy-efficient and less secondary components are formed in the method. In addition, a higher conversion rate and a higher yield of n-butyl (meth)acrylate are achieved.

[0049] In an alternative method of the present invention, in order to continuously prepare n-butyl (meth)acrylate by reacting (meth) acrylic acid with n-butanol in the presence of an acidic catalyst and a polymerization inhibitor, the following steps are included:

[0050] The esterification is carried out in the reaction zone (E1), wherein the reaction zone (E1) is located at the bottom of the distillation column (E), wherein the ratio of the reaction mixture to the distillation mixture is in the range of 1.0:1.0 to 1.0:2.0, preferably in the range of 1.0:

[0051] The components (meth)acrylic acid and n-butanol are fed in a molar ratio in the range of 1.1 to 1.0:1.5, and wherein the esterification takes place at a temperature in the range of 80° C. to 150° C., preferably in the range of 100° C. to 130° C. and at an absolute pressure in the range of 0.2 bar to 5.0 bar, preferably in the range of 0.4 bar to 1.5 bar,

[0052] Separation of azeotropes formed by esterification:

[0053] a) water and n-butyl (meth)acrylate,

[0054] b) n-butyl alcohol and n-butyl (meth)acrylate,

[0055] c) n-butanol and water,

[0056] d) n-butanol, n-butyl (meth)acrylate and water,

[0057] wherein the separation takes place by means of a rectification column (E) which is operated with a bottom temperature in the range of 80° C. to 150° C., a top temperature in the range of 70° C. to 130° C. and an absolute pressure in the range of 0.2 bar to 5 bar,

[0058] At the top of the distillation column (E), a gas stream enriched with azeotropes is discharged,

[0059] condensing the gas stream in a condenser (F) to form an organic phase rich in n-butyl (meth)acrylate and an aqueous phase,

[0060] · Continuous separation of the organic phase from the aqueous phase by means of a phase separator (G),

[0061] continuously removing at least a portion of the organic phase from the phase separator (G), wherein the portion of the organic phase which is rich in n-butyl (meth)acrylate is the crude product stream (15),

[0062] a reboiler bottoms discharge (23) is discharged from the bottom of the rectification column (E), wherein the mass flow ratio between the reboiler bottoms discharge (23) and the (meth)acrylic acid fed as a raw material to the reaction zone (E1) is in the range of 0.05 to 0.5,

[0063] feeding a reboiler part stream (7) of the discharged reboiler bottoms discharge (23) into a mixer (H), wherein the mass flow ratio between the reboiler part stream (7) and the reboiler bottoms discharge (23) is in the range from 0.01 to 1.00, preferably in the range from 0.10 to 0.70,

[0064] The mixture (10) produced from the mixer (H) is fed to a downstream extract phase separator (I),

[0065] Continuously separating the mixture (10) in an extract phase separator (I) to obtain an organic concentrate (11) and an aqueous extract (12) containing the catalyst, wherein the aqueous extract (12) is at least partially refluxed to the distillation column (E),

[0066] In this case, external water (19) is fed to the mixer (H), and the mass flow ratio between the mass flow of the external water (19) and the reboiler part flow (7) of the discharged reboiler bottom discharge (23) is in the range of 0.08 to 0.50, preferably in the range of 0.10 to 0.30.

[0067] In this alternative method of the present invention, the same technical effects can also be observed. It is therefore also recognized here that by conveying external water (19) to the mixer (H), there is always a two-phase separation of the resulting mixture (10) after the startup phase of the device. Therefore, under all operating conditions occurring in the device, reflux of the catalyst can always be carried out. In addition, the moisture content in the device, such as in particular the moisture content in the reaction zone (E1) or the distillation column (E), can also be kept at a low level as much as possible. In addition, the method is therefore more energy-efficient and less by-components are formed in the method. In addition, a higher conversion rate and a higher yield of n-butyl (meth) acrylate are achieved.

[0068] The term “distillation column” is understood in this context as a general term for apparatuses in which vapors are generated by the supply of heat, which vapors rise and come into contact with an emanating liquid phase.

[0069] The general structure of a distillation column is well known and has common devices, such as an evaporator in the bottom, an evaporator in the heavy boiler effluent or a condenser in the light boiler effluent, wherein the heavy boiler is preferably located in the bottom region of the distillation column, and the light boiler is preferably located in the top region of the distillation column. In a typical case, a part of the mass flow of the heavy boiler effluent is refluxed to the bottom region of the distillation column. In principle, it is also feasible to heat the bottom region via, for example, heating the outer wall of the tower in the bottom region, and / or to integrate an evaporator in the bottom region. In a typical case, a steam stream is extracted at the top of the distillation column and transported to the condenser. The steam stream is also usually referred to as the light boiler effluent. A part of the steam stream condensed in the condenser is refluxed to the distillation column, and the rest of the condensed steam stream is discharged as a distillate. In this case, the reflux ratio describes the ratio between the condensed steam stream refluxed to the tower and the condensed steam stream extracted as a distillate. Usually, the reflux ratio is set in the range of 10% to 200%. In principle, all common internals such as plates, fillers and / or bulk fillers can be used as the internals of the distillation column (E). The plates are preferably bell plates, sieve plates, valve plates, Thormann plates and / or double-flow plates; the bulk fillers are preferably ring-shaped, spiral, saddle-shaped or mesh-shaped fillers. In addition, the distillation column (E) may also contain other standard components for control, such as pressure reducers, flow regulators or sensors. In principle, several distillation columns can also be connected together in series or in parallel, and these distillation columns can also function as a "distillation column" (E) in the form of a composite structure.

[0070] Herein, when acrylic acid is used, a substance component having a boiling point lower than that of n-butyl acrylate at normal pressure is referred to as a low-boiling substance. Similarly, a substance component having a boiling point greater than or equal to that of n-butyl acrylate at normal pressure is referred to as a heavy-boiling substance. The boiling point of n-butyl acrylate is 147° C. at normal pressure.

[0071] Herein, when methacrylic acid is used, a substance component having a boiling point lower than that of n-butyl methacrylate at normal pressure is referred to as a light boiler. Similarly, a substance component having a boiling point greater than or equal to that of n-butyl methacrylate at normal pressure is referred to as a heavy boiler. The boiling point of n-butyl methacrylate is 163° C. at normal pressure.

[0072] In this document, the term "reactor" is generally defined as a reactor (A) or several interconnected reactors that function as a "reactor" (A). The reactor (A) also includes a reactor heating element for heating the reaction mixture. The reactor heating element is, for example, an immersion boiler in the reactor (A), a piping system including coils or semi-coils arranged on the outer side of the reactor and / or inside the reactor (A), an electric heating system arranged on the outer side of the reactor (A) and / or inside the reactor (A), an evaporator located outside the reactor (A), wherein the reaction mixture at least partially flows through the evaporator or a double-walled embodiment of the reactor outer wall, in which the fluid separated from the reaction mixture, such as a liquid, a gas and / or a heating steam, is temperature-controlled to reach a predetermined heating temperature, and the reaction mixture is thus heated in the reactor (A). In general, several reactor heating elements can be used to heat the reaction mixture in the reactor (A). That is, the double-walled embodiment of the reactor outer wall and the evaporator located outside the reactor (A) can exemplarily heat the reaction mixture simultaneously or at least partially staggered in time. The reactor (A) further comprises a column (B) mounted on top thereof, which preferably separates water by distillation. The column (B) itself is a distillation column with internals. Such internals are trays, such as bell trays, perforated plates, in particular dual-flow plates, bulk packing, packing or the like. In another preferred embodiment, the reactor (A) is integrated in a distillation column (E), so that the esterification can take place in the bottom of the distillation column (E), i.e. in the reaction zone (E1).

[0073] In this article, the term "mass flow ratio" between the real value A1 and the real value B1 is equivalent to the division ratio with A1 as the numerator and B1 as the denominator. Therefore, the formula is:

[0074] In this context, the term "external water" (19) refers to water from outside the process, which is introduced into the process through the water inlet at the mixer (H). The external water (19) is preferably deionized water, particularly preferably completely deionized water. The external water (19) preferably has a pH value in the range of 4.5 to 10.5, particularly preferably in the range of 6.5 to 10.0. Preferably, the external water (19) contains no electrolyte components or only trace amounts of electrolyte components, preferably less than 0.1 wt% of electrolyte components.

[0075] Preferably, p-toluenesulfonic acid is put in as an acidic esterification catalyst, i.e., an acidic catalyst. It is suitably 0.1wt% to 10.0wt% in the reaction zone (E1) or the reactor (A) relative to the content of the reaction mixture contained therein, preferably 0.1wt% to 6.0wt%. Other organic sulfonic acids such as methanesulfonic acid, benzenesulfonic acid, dodecylbenzenesulfonic acid and / or sulfuric acid can also be put in. Their amount is equimolar with p-toluenesulfonic acid. Corresponding mixtures are also feasible. The catalytically active acid in the bottom of the rectifying tower (E) can advantageously be p-toluenesulfonic acid between 2.5wt% and 50.0wt% relative to the content of the mixture contained therein, or other organic sulfonic acids and / or sulfuric acid in equimolar amounts.

[0076] In a preferred embodiment of the method, the mixture (10) emerging from the mixer (H) has a temperature at the outlet of the mixer (H) in the range of 20° C. to 100° C., preferably in the range of 70° C. to 95° C. This has the advantage that the aqueous phase and the organic phase do not have to be heated in subsequent stages of the method, so that energy can be saved.

[0077] In a preferred embodiment of the process, the reboiler bottoms discharge (23) has a water concentration of less than 10% by weight, preferably less than 5% by weight. This has the advantage that less water has to be distilled in the distillation column (E), thereby reducing the energy consumed for heating the distillation column (E) and thus reducing the secondary components formed.

[0078] In a preferred embodiment of the process, the substream of the aqueous extract is recirculated to the reactor (A) or the reaction zone (E1), wherein the mass flow ratio between the substream of the aqueous extract and the total mass flow of the aqueous extract (12) is in the range from 0.1 to 1.0, preferably in the range from 0.8 to 1.0. This has the advantage that the catalyst can be efficiently recirculated without increasing the water content in the system.

[0079] In a preferred embodiment of the process, such a mass flow of external water (19) is added to the reboiler substream (7) of the discharged reboiler bottoms discharge (23) in the mixer (H) that a phase ratio of the aqueous extract (12) to be obtained and the organic refined product (11) to be obtained is in the range of 0.08 kg / kg to 0.5 kg / kg, preferably in the range of 0.1 kg / kg to 0.3 kg / kg. The advantages resulting from this are that a two-phase separation of the two phases is ensured, as little catalyst as possible has to be discharged from the process, and the water content is kept as low as possible during esterification and distillation.

[0080] When the mass flow ratio between the mass flow of the external water (19) and the reboiler fraction (7) of the discharged reboiler bottoms discharge (23) is 0.5 kg / kg or less, it is sufficient to achieve a successful reflux of the acidic catalyst and the energy requirement of the process, in particular the energy requirement for the evaporation of the water, is reduced compared to the use of larger amounts of water. When the mass flow ratio between the mass flow of the external water (19) and the reboiler fraction (7) of the discharged reboiler bottoms discharge (23) is at least 0.08 kg / kg, efficient extraction and phase separation in the extractive phase separator (I) are conversely facilitated.

[0081] In a preferred design of the method, at least a fraction of the organic refined product (11) is conveyed to a cleavage reactor (J). In particular, the cleavage reactor (J) is connected downstream of the mixer (H) and the extract phase separator (I). The advantage derived from this is that the organic component, i.e., the organic refined product (11), is conveyed to the cleavage reactor (J) after phase separation, so that the bottom mixture in the cleavage reactor (J) that is conveyed through the pipeline 21 is anhydrous and thus less corrosive. In addition, by this arrangement, it is avoided that the by-products formed in the cleavage reactor (J) are refluxed together with the extract into the reactor (A) or the reaction zone (E1). By this arrangement, the phase separation in the extract phase separator (I) is also improved, mainly because the viscosity of the continuous phase, i.e., the organic refined product (11), is lower and the density difference between the two phases, i.e., the organic refined product (11) and the aqueous extract (12), is greater than that of the extraction downstream of the cleavage reactor (J).

[0082] In a preferred embodiment of the method, a substream of the organic refined product (11) is fed to the cleavage reactor (J), wherein the mass flow ratio between the substream of the organic refined product (11) and the total mass flow of the organic refined product is in the range of 0.1 to 1.0, preferably in the range of 0.95 to 1.0. This has the advantage that the reboiler can be cleaved and the cleavage products, such as (meth)acrylic acid and n-butanol, can be reused in the method as raw materials.

[0083] In a preferred embodiment of the method, the esterification takes place at a temperature in the range of 90° C. to 130° C., preferably in the range of 95° C. to 105° C., and at an absolute pressure in the range of 0.8 bar to 2.0 bar, preferably in the range of 1.0 bar to 1.5 bar. This results in the advantage that the conversion rate is kept as high as possible and the formation of secondary components is kept as low as possible.

[0084] In a preferred embodiment of the method, the substream (8) of the reboiler bottoms discharge (23) is fed to the cleavage reactor (J) in a mass flow ratio of the substream to the reboiler substream (7) of the reboiler bottoms discharge (23) in a range from 0.0 to 10.0, preferably in a range from 0.1 to 1.0. This has the advantage that sufficient catalyst is present in the cleavage reactor (J) for the cleavage reaction.

[0085] In a preferred embodiment of the process, a substream (9) of the reboiler bottom discharge (23) is fed to the reactor (A) at a mass flow ratio of the substream to the total reboiler bottom flow (23) in the range from 0.1 to 0.99, preferably in the range from 0.85 to 0.95. This has the advantage that the catalyst can be refluxed and reused.

[0086] In a preferred embodiment of the method, the reboiler bottoms (23) has a moisture content in the range of 0.1 wt % to 10.0 wt %, more preferably in the range of 0.1 wt % to less than 10.0 wt %, more preferably in the range of 0.1 wt % to less than 5 wt %, in particular in the range of 0.1 wt % to 4.5 wt %. This results in the advantage that there is no excess water in the method, which reduces the energy required and reduces the formation of secondary components. At the same time, however, a single-phase extraction of the reboiler bottoms (23) is ensured and then a two-phase separation of the resulting mixture (10) is ensured after the addition of water in the mixer (H).

[0087] In a preferred embodiment of the method, the reboiler bottom discharge (23) has an oligomer and / or polymer content in the range of 1 wt % to 80 wt %, more preferably in the range of 10 wt % to 65 wt %, in particular in the range of 20 wt % to 60 wt %. Oligomers and / or polymers are molecules with a mass average molecular weight of more than 1000 g / mol. An oligomer and / or polymer content of 80 wt % or less in the reboiler bottom discharge (23) provides the advantage of a lower viscosity, thereby improving the subsequent phase separation in the extraction phase separator (I). The mass flow ratio between the mass flow (19) of the external water and the reboiler subflow (7) of the discharged reboiler bottom discharge (23) can be further reduced.

[0088] In a preferred embodiment of the method, the reboiler bottom discharge (23) has a catalyst content in the range of 0.1 wt % to 10.0 wt %. This has the advantage that it is not necessary to separate too much catalyst, so that the method is more energy-efficient and less catalyst can be used in the method.

[0089] In a preferred embodiment of the process, the acidic catalyst contains p-toluenesulfonic acid in the range of 0 wt % to 100 wt %, preferably in the range of 80 wt % to 100 wt %, particularly preferably in the range of 95 wt % to 100 wt %. This has the advantage that the esterification is very efficient, since the catalyst has a high selectivity, high reactivity and a long service life in the process.

[0090] In another embodiment of the method, the reboiler bottoms discharge (23) is single-phase. In this case, external water (19) is added to the mixer (H) in such an amount that the resulting mixture (10) is two-phase.

[0091] In a further embodiment of the process, a fraction of the organic phase (14) from the phase separator (G) is refluxed to the distillation column (E) at a reflux ratio of the fraction to the organic phase in the range from 0.1 to 1.0, and a fraction of the aqueous phase (16) from the phase separator (G) is refluxed to the distillation column at a reflux ratio of the fraction to the aqueous phase in the range from 1 to 10. This has the advantage that less organic phase has to be discharged from the process or less aqueous phase has to be separated from the process, and both the esterification and the separation in the distillation column (E) are carried out in an energy-efficient manner. In addition, the formation of secondary components is reduced.

[0092] In another embodiment of the process, the acidic catalyst is present in a concentration in the range of 0.1 wt % to 10 wt % in the reaction effluent produced in the reaction zone (E1) of the rectification column (E) or in the reactor (A). This has the advantage that no excess catalyst has to be separated off, so that the process is more energy-efficient and less catalyst can be used in the process.

[0093] In a further embodiment of the process, a substream of the aqueous extract (12) is fed to the reactor (A) in a mass flow ratio of the substream to the total reboiler bottoms discharge (23) in a range from 0.01 to 0.50, preferably in a range from 0.01 to 0.30.

[0094] The invention will be described in more detail below with reference to the drawings. These drawings are to be understood as schematic illustrations. They do not constitute a limitation of the invention, for example in terms of specific dimensions or design variants. Among them:

[0095] Figure 1 A first embodiment of the process of the present invention for continuously preparing n-butyl (meth)acrylate is shown, in which a reactor A is used, which is connected downstream to a distillation column E. In this case, the aqueous extract containing the catalyst is refluxed to the reactor A and / or the distillation column E.

[0096] Figure 2 A second embodiment of the process according to the invention for the continuous preparation of n-butyl (meth)acrylate is shown, in which a reaction zone E1 is integrated in the bottom region of the distillation column E. In this case, the aqueous extract containing the catalyst is refluxed to the distillation column E.

[0097] Figure 3 A third embodiment of continuously preparing n-butyl (meth)acrylate is shown as a comparative example, in which a reactor A is used, and a distillation column E is connected downstream. In this case, the aqueous extract containing the catalyst is not refluxed to the reactor A and / or the distillation column E.

[0098] List of Figure Numbers:

[0099] 1 Pipeline for transporting raw material flow

[0100] 2. Excess steam from condenser C

[0101] 3 Pipe for reflux of the organic phase from the liquid-liquid phase separator D

[0102] 4 Pipe for discharging the organic phase from the liquid-liquid phase separator D

[0103] 5 Pipe for conveying the aqueous phase from the liquid-liquid phase separator D to the liquid-liquid phase separator G

[0104] 6 The pipeline for sending the generated reaction effluent into the distillation tower E

[0105] 7 A pipe for branching the reboiler bottom discharge 23 to the mixer H, or a pipe for branching the reboiler bottom discharge 23 to the mixer H.

[0106] Reboiler fraction of discharge 23 to mixer H

[0107] 8 A pipe for branching the reboiler bottom discharge 23 to the cracking reactor J, or a pipe for branching the reboiler bottom discharge 23 to the cracking reactor J.

[0108] A substream of the bottom discharge 23 to the cleavage reactor J.

[0109] 9 A pipe for returning a portion of the reboiler bottom discharge 23 to the reactor A, or a pipe for returning a portion of the reboiler bottom discharge 23 to the reactor A

[0110] 10 The mixture produced from the mixer H

[0111] 11 is a pipeline for conveying the organic refined product from the extraction phase separator I to the cracking reactor J, or the organic refined product

[0112] 12 The pipeline for reflux the aqueous extract from the extract phase separator I to the reactor or the distillation column E, or the aqueous extract

[0113] 13 Excess steam from condenser F

[0114] 14 The organic phase from the liquid-liquid phase separator G is refluxed to the pipeline of the distillation column E, or the organic phase from the liquid-liquid phase separator G is refluxed to the pipeline of the distillation column E.

[0115] 15 A pipe for discharging the branched flow of the organic phase from the phase separator G, or a crude product flow

[0116] 16 The water phase from the liquid-liquid phase separator G is refluxed to the pipeline of the distillation tower E, or the water phase from the liquid

[0117] - Aqueous phase of liquid phase separator G

[0118] 17 Pipe for discharging the water phase from the liquid-liquid phase separator G

[0119] 19 A pipe for conveying external water to the mixer H, or an external water

[0120] 21 Pipe for discharging the bottom discharge of the reboiled product of the cracking reactor J

[0121] 22 Pipe for discharge of light boilers from cracking reactor J

[0122] 23 Pipe for discharging the reboiled product from the bottom of the distillation column E, or pipe for discharging the reboiled product from the bottom of the distillation column E

[0123] 24 Pipe for conveying polymer inhibitor stream to condenser C

[0124] 25 Pipe for conveying polymer inhibitor stream to condenser F

[0125] A Reactor

[0126] B-pillar

[0127] C Condenser

[0128] D Phase Separator

[0129] E Distillation Tower

[0130] E1 Reactor integrated in the distillation column

[0131] F Condenser

[0132] G Phase Separator

[0133] H Mixer

[0134] I Extraction Phase Separator

[0135] J Cracking Reactor

[0136] Figure 1The process flow diagram schematically shows a process-technical procedure of a first embodiment of the method according to the invention, in which external water 19 is added to the mixer H.

[0137] Via line 1, a raw material mass flow comprising n-butanol, acrylic acid, PTZ and p-toluenesulfonic acid as an esterification catalyst is conveyed to reactor A. Column B arranged above reactor A separates the vapor mixture flowing out of reactor A via its internals which have a separating function. Downstream condenser C at least partially condenses the vapor stream arising from column B, which condenser can also be supplemented by an aftercooler. A solution of polymerization inhibitor PTZ is added to condenser C via line 24. The uncondensed portion from condenser C contains low-boiling impurities and is withdrawn in the form of vapor via line 2.

[0138] The condensed vapor stream is fed as condensate into a liquid-liquid phase separator D. There, the condensate is separated into an aqueous phase and an organic phase. The aqueous phase, which mainly contains water, is led from the liquid-liquid phase separator D to a liquid-liquid phase separator G via a line 5.

[0139] The reaction effluent produced is extracted from the lower part of the reactor A through the pipeline 6, and mainly contains n-butyl acrylate, unreacted raw materials and high-boiling impurities, and is conveyed to the distillation column E having internals for separation. In the distillation column E, water, n-butyl acrylate, ethanol, etc. are mainly separated. The steam escaping from the column is sent to the condenser F and partially condensed therein, and the condenser can also be supplemented by an aftercooler when appropriate. A solution of a polymerization inhibitor PTZ is added to the condenser F through the pipeline 25. The uncondensed part from the condenser F contains low-boiling impurities, which is extracted in the form of steam through the pipeline 13, and the condensate produced flows into the liquid-liquid phase separator G. There, the condensate is separated into an aqueous phase and an organic phase.

[0140] The organic phase mainly containing n-butyl acrylate and n-butanol is partially refluxed again as reflux to the distillation column E through a pipe 14, and the rest is discharged for further treatment through a pipe 15. The aqueous phase mainly containing water is partially refluxed as reflux to the distillation column E through a pipe 16, and the rest is discharged for further treatment through a pipe 17.

[0141] High-boiling impurities and the added catalyst are mainly withdrawn from the lower part of the distillation column E through the pipeline 23 and introduced into the cracking reactor J, the mixer H and the return reactor A through the downstream pipelines 7, 8 and 9. In the mixer H, external water 19 is added as an extractant, wherein the resulting mixture is conveyed to the extracting phase separator I through the pipeline 10.

[0142] In the extract phase separator I, the resulting mixture is separated into an organic refinement and an aqueous extract containing the catalyst. The aqueous extract, which mainly contains water, is refluxed to the reactor A via the conduit 12. The organic refinement is at least partially conveyed to the cleavage reactor J via the conduit 11 for further treatment. The reboiler bottom discharge is also at least partially conveyed to the cleavage reactor J via the conduit 8 for further treatment. The bottom effluent of the cleavage reactor J is discharged from the process via the conduit 21, while the gaseous substances are extracted via the conduit 22 at the top of the cleavage reactor J. The gaseous substances can then be condensed and finally refluxed back to the reactor A.

[0143] Figure 2 A process flow diagram schematically shows a process-technical process of an alternative second embodiment of the method according to the invention, in which external water 19 is added to the mixer H, wherein in this embodiment, in contrast to the first embodiment, a reaction zone E1 is integrated in the bottom of the distillation column E.

[0144] Figure 3 A process flow diagram of a process technology process is schematically shown as a comparative example, wherein, compared with the first embodiment, there is no mixer H and extraction phase separator I, so that the aqueous extract from the extraction phase separator I cannot be refluxed to the reactor A. Example

[0145] The following example of the method is represented by thermodynamic simulation. The software Aspen was used for this purpose. (Aspen), the software is available on the website https: / / www.aspentech.com Aspen is a comprehensive simulation software for modeling, simulation and optimization of chemical processes and equipment in industrial sectors. Aspen has a comprehensive model database for modeling basic operations and a physical property database for material properties of many different substances. The properties of mixtures are calculated by Aspen from the physical property data of pure substances using different thermodynamic models.

[0146] Comparative Example 1

[0147] Execute according to Aspen Figure 3 Thermodynamic simulation of the entire device provides the following results:

[0148] The feed stream is delivered to the reactor A via pipeline 1 at a mass flow rate of 1000 kg / h, wherein the feed stream is a mixture having the following composition:

[0149] n-Butanol: 582.2kg / h

[0150] Acrylic acid: 413.9kg / h

[0151] p-Toluenesulfonic acid: 3.9kg / h.

[0152] Column B, which is arranged above reactor A, separates, via its separating internals, the vapor mixture emerging from reactor A. A downstream condenser C condenses the vapor stream emerging from column B at least partially.

[0153] A solution of a polymerization inhibitor is introduced into the condenser C via the pipeline 24 at a mass flow rate of 2 kg / h, wherein the solution of the polymerization inhibitor has the following composition:

[0154] n-Butyl acrylate: 98wt%

[0155] Phenothiazine: 2 wt%.

[0156] The uncondensed portion from condenser C contains low-boiling impurities and is withdrawn in the form of vapor via line 2 .

[0157] The esterification was carried out in reactor A at a temperature of 105°C, a pressure of 470 mbar and a residence time of 2 hours.

[0158] From the liquid-liquid phase separator D downstream of the condenser C, 27 kg / h of organic phase was extracted as an organic distillate through a pipe 4 , and 798 kg / h of organic phase was refluxed to the column B through a pipe 3 as a reflux.

[0159] The organic phase as organic distillate has the following composition:

[0160] Water: 19.6wt%

[0161] n-Butanol: 77.3wt%

[0162] n-Butyl acrylate: 1.5wt%

[0163] Acrylic acid: <0.01wt%

[0164] n-Butyl acetate: 1.2wt%

[0165] Phenothiazine: <0.01wt%

[0166] Unknown components: 0.4wt%.

[0167] From the liquid-liquid phase separator D, 145 kg / h of aqueous phase are led to the liquid-liquid phase separator G via line 5. The aqueous phase has the following composition:

[0168] Water: 94.0wt%

[0169] n-Butanol: 5.9wt%

[0170] Unknown components: 0.1wt%.

[0171] In the lower part of the reactor A, the resulting reaction effluent is withdrawn via the pipeline 6 at a mass flow rate of 1415 kg / h, having the following composition, and is fed to the distillation column E:

[0172] Water: 0.2wt%

[0173] n-Butanol: 10.2wt%

[0174] n-Butyl acrylate: 68.0wt%

[0175] Acrylic acid: 5.0wt%

[0176] n-Butyl acetate: <0.1wt%

[0177] p-Toluenesulfonic acid: 1.6wt%

[0178] Phenothiazine: 0.1wt%

[0179] Unknown components: 14.8wt%.

[0180] In the distillation column E equipped with 13 theoretical stages, water, n-butanol and n-butyl acrylate are withdrawn in the form of vapor through the top of the distillation column E, condensed in a condenser F, and subsequently sent to a liquid-liquid phase separator G. In the top region of the column, the pressure is 1059 mbar and the temperature is 95° C.

[0181] A solution of a polymerization inhibitor is introduced into the condenser F via the pipe 25 at a mass flow rate of 2 kg / h, wherein the solution of the polymerization inhibitor has the following composition:

[0182] n-Butyl acrylate: 98wt%

[0183] Phenothiazine: 2 wt%.

[0184] From the liquid-liquid phase separator G, 803 kg / h of organic phase was withdrawn as organic distillate via line 15 for further purification. A substream with a mass flow of 365 kg / h was refluxed to the distillation column E via line 14 as reflux.

[0185] The organic phase has the following composition:

[0186] Water: 2.7wt%

[0187] n-Butanol: 16.8wt%

[0188] n-Butyl acrylate: 80.3wt%

[0189] Acrylic acid: <0.01wt%

[0190] n-Butyl acetate: 0.1wt%

[0191] Phenothiazine: <0.01wt%

[0192] Unknown components: 0.1wt%.

[0193] From the liquid-liquid phase separator G, 83 kg / h of aqueous phase was withdrawn as aqueous distillate via line 17. A partial flow of the aqueous phase having a mass flow rate of 724 kg / h was refluxed to the distillation column E via line 16 as reflux.

[0194] The aqueous phase has the following composition:

[0195] Water: 96.7wt%

[0196] n-Butanol: 2.0wt%

[0197] n-Butyl acrylate: 1.3wt%

[0198] Unknown components: <0.1wt%.

[0199] At the lower part of the distillation column E, a substream of the reboiler bottom discharge 23 is introduced to the cleavage reactor J at a mass flow rate of 53 kg / h through a pipe 8, and a substream of the reboiler bottom discharge 23 is returned to the reactor A at a mass flow rate of 585 kg / h through a pipe 9. The steam mixture produced in the cleavage reactor J is sent out through a pipe 22, and the bottom mixture is sent out through a pipe 21.

[0200] The reboiler bottoms discharge 23 has the following composition:

[0201] Water: 3.1wt%

[0202] n-Butanol: 4.3wt%

[0203] n-Butyl acrylate: 21.4wt%

[0204] Acrylic acid: 11.1wt%

[0205] p-Toluenesulfonic acid: 3.4wt%

[0206] Phenothiazine: 0.2wt%

[0207] Unknown components: 56.5wt%.

[0208] Unknown components include oligomers and / or polymers.

[0209] Example 1

[0210] In Example 1, the software Aspen is used to simulate Figure 1 The simulation provides the following results:

[0211] A feed stream is introduced into the reactor A via pipeline 1 at a mass flow rate of 1000 kg / h, wherein the feed stream has the following composition:

[0212] n-Butanol: 584.3kg / h

[0213] Acrylic acid: 414.4kg / h

[0214] p-Toluenesulfonic acid: 1.3kg / h.

[0215] The esterification in reactor A was performed at a temperature of 105°C, a pressure of 470 mbar absolute and a residence time of 2 hours.

[0216] Column B, which is arranged above reactor A, separates, via its separating internals, the vapor mixture emerging from reactor A. A downstream condenser C condenses the vapor stream emerging from column B at least partially.

[0217] A solution of a polymerization inhibitor is introduced into the condenser C via the pipeline 24 at a mass flow rate of 2 kg / h, wherein the solution of the polymerization inhibitor has the following composition:

[0218] n-Butyl acrylate: 98wt%

[0219] Phenothiazine: 2 wt%.

[0220] The uncondensed portion from condenser C contains low-boiling impurities and is withdrawn in the form of vapor via line 2 .

[0221] From the liquid-liquid phase separator D downstream of the condenser C, 27 kg / h of organic phase was extracted as an organic distillate through a pipe 4 , and 934 kg / h of organic phase was refluxed to the column B through a pipe 3 as a reflux.

[0222] The organic phase has the following composition:

[0223] Water: 19.6wt%

[0224] n-Butanol: 76.9wt%

[0225] n-Butyl acrylate: 1.7wt%

[0226] Acrylic acid: <0.01wt%

[0227] n-Butyl acetate: 1.4wt%

[0228] Phenothiazine: <0.01wt%

[0229] Unknown components: 0.4wt%.

[0230] From the liquid-liquid phase separator D, the aqueous phase is conducted via line 5 to the liquid-liquid phase separator G at a mass flow rate of 155 kg / h.

[0231] The aqueous phase has the following composition:

[0232] Water: 94.0wt%

[0233] n-Butanol: 5.9wt%

[0234] Unknown components: 0.1wt%.

[0235] In the lower part of the reactor A, a liquid mixture is withdrawn via the pipeline 6 at a mass flow rate of 1422 kg / h, which has the following composition and is conveyed to the distillation column E:

[0236] Water: 0.2wt%

[0237] n-Butanol: 10.2wt%

[0238] n-Butyl acrylate: 68.0wt%

[0239] Acrylic acid: 5.0wt%

[0240] n-Butyl acetate: 0.0wt% to 0.1wt%

[0241] p-Toluenesulfonic acid: 1.6wt%

[0242] Phenothiazine: 0.2wt%

[0243] Unknown ingredients: 14.7wt% to 14.8wt%

[0244] In the distillation column E equipped with 13 theoretical stages, water, n-butanol and n-butyl acrylate are withdrawn in the form of vapor through the top of the distillation column E, condensed in a condenser F, and then sent to a liquid-liquid phase separator G. In the top region of the distillation column E, the absolute pressure is 1059 mbar and the temperature is 95°C.

[0245] A solution of a polymerization inhibitor is introduced into the condenser F via the pipe 25 at a mass flow rate of 2 kg / h, wherein the solution of the polymerization inhibitor has the following composition:

[0246] n-Butyl acrylate: 98wt%

[0247] Phenothiazine: 2 wt%.

[0248] From the liquid-liquid phase separator G, the organic phase was withdrawn as an organic distillate at a mass flow rate of 807 kg / h via line 15 for further purification. A substream at a mass flow rate of 367 kg / h was refluxed to the distillation column E via line 14 as reflux.

[0249] The organic phase has the following composition:

[0250] Water: 2.6wt%

[0251] n-Butanol: 16.7wt%

[0252] n-Butyl acrylate: 80.5wt%

[0253] Acrylic acid: <0.01wt%

[0254] n-Butyl acetate: 0.1wt%

[0255] Phenothiazine: <0.01wt%

[0256] Unknown components: 0.1wt%.

[0257] From the liquid-liquid phase separator G, an aqueous phase with a mass flow rate of 101 kg / h was withdrawn as aqueous distillate via line 17 for further purification. A substream with a mass flow rate of 728 kg / h was refluxed to the distillation column E via line 16 as reflux.

[0258] At the lower part of the distillation tower E, the split flow is introduced to the mixer H through pipeline 7 at a mass flow rate of 49 kg / h, the split flow is introduced to the cracking reactor J through pipeline 8 at a mass flow rate of 24 kg / h, and the split flow is returned to the reactor A through pipeline 9 at a mass flow rate of 588 kg / h.

[0259] The liquid mixture has the following composition:

[0260] Water: 3.1wt%

[0261] n-Butanol: 4.3wt%

[0262] n-Butyl acrylate: 21.7wt%

[0263] Acrylic acid: 11.1wt%

[0264] p-Toluenesulfonic acid: 3.4wt%

[0265] Phenothiazine: 0.4wt%

[0266] Unknown ingredients: 56.0wt%.

[0267] Unknown components include oligomers and / or polymers.

[0268] In the mixer H, the split stream containing catalyst and high-boiling impurities from the rectification column E is mixed with a mass stream consisting of external water 19 via a pipe 7, thereby forming a phase ratio of 0.2 kg / kg, wherein the phase ratio is obtained by the ratio between the mass flow of external water 19 plus the mass flow of the water phase of the split stream 7 and the mass flow of the organic phase of the split stream 7. Subsequently, the mixture produced from the mixer H is conveyed to the extracting phase separator I via a pipe 10.

[0269] 45 kg / h of organic refined product is sent out as an organic mixture from the extractive phase separator I through the pipeline 11 and added to the cleavage reactor J for further purification. The steam mixture produced in the cleavage reactor J is sent out through the pipeline 22, and the bottom mixture is sent out through the pipeline 21.

[0270] The organic refined product has the following composition:

[0271] Water: 1.9wt%

[0272] n-Butanol: 4.6wt%

[0273] n-Butyl acrylate: 23.8wt%

[0274] Acrylic acid: 9.0wt%

[0275] p-Toluenesulfonic acid: <0.05wt%

[0276] Phenothiazine: 0.2wt%

[0277] Unknown components: 60.5wt%.

[0278] Unknown components include oligomers and / or polymers.

[0279] From the extract phase separator I, the aqueous extract is returned to the reactor A via line 12 at a mass flow rate of 15 kg / h.

[0280] The aqueous extract has the following composition:

[0281] Water: 71.4wt%

[0282] n-Butanol: 0.6wt%

[0283] n-Butyl acrylate: 0.9wt%

[0284] Acrylic acid: 10.1wt%

[0285] p-Toluenesulfonic acid: 11.5wt%

[0286] Phenothiazine: 0.7wt%

[0287] Unknown components: 4.8wt%.

[0288] It can be concluded from these two examples that the following results are obtained when the catalyst concentration in reactor A is the same:

[0289] The catalyst-containing feed stream delivered to the reactor A through the pipeline 1 has a lower catalyst concentration in Example 1 of the present invention than in Comparative Example 1. That is, in Example 1 of the present invention, a mass flow rate of 1.3 kg / h of new catalyst is delivered to the pipeline 1, while in Comparative Example 1, a mass flow rate of 3.9 kg / h of new catalyst is delivered to the pipeline 1.

[0290] This is because in Example 1 of the present invention, the aqueous extract 12 was refluxed to the reactor A at a mass flow rate of 15 kg / h, wherein the catalyst concentration was 11.5 wt%. In Example 1, there was phase separation because the phase ratio between the external water 19 and the reboiler substream 7 of the reboiler bottom discharge 23 at the outlet of the mixer H was 0.2 kg / kg, while in Comparative Example 1, no external water 19 was added, and the water concentration in the reboiler bottom discharge 23 was only 0.03 kg / kg. Therefore, there was no phase separation in Comparative Example 1, and the catalyst could not be refluxed to the reactor A.

[0291] Therefore, 66.7% of the amount of catalyst was saved in Example 1 of the present invention.

[0292] Furthermore, the influence of the components of the cracking reactor J on the process was experimentally investigated.

[0293] Example 2

[0294] In Example 2, the cleavage reactor J is connected downstream of the mixer H and the extractive phase separator I similarly to Example 1. The reboiler fraction 7 of the reboiler bottom discharge 23 from the bottom of the rectification column E is conveyed to the mixer H. The viscosity of the organic refined product 11 taken out from the extractive phase separator I and conveyed to the cleavage reactor J is 0.7 mPas. External water 19 is added to the mixer H, and the mass flow ratio between the mass flow of the external water 19 and the reboiler fraction 7 of the reboiler bottom discharge 23 discharged is in the range of 0.13 kg / kg to 0.34 kg / kg. The separation time in the extractive phase separator I is 60 seconds, and the density difference is 100 kg / m 3 .

[0295] Example 3

[0296] In Example 3, the cleavage reactor J is connected upstream of the mixer H, and a fraction 8 of the reboiler bottom discharge 23 from the bottom of the rectification column E (similar to Figure 3) is first transported to the cleavage reactor J. The reboiler bottom discharge 21 of the cleavage reactor J is then transported to the mixer H, to which an extracting phase separator I is connected downstream. The viscosity of the organic refined product 11 taken out of the extracting phase separator I is 30 mPas. External water 19 is added to the mixer H, and the mass flow ratio between the mass flow of the external water 19 and the reboiler bottom discharge 21 of the cleavage reactor J is 1 kg / kg. The separation time in the extracting phase separator I is 240 s to 300 s, and the density difference is 12 kg / m 3 The low value of .

Claims

1. A method for continuously preparing n-butyl (meth)acrylate by reacting (meth) acrylic acid with n-butanol in the presence of an acidic catalyst and a polymerization inhibitor, comprising the following steps: The esterification is carried out in a reactor (A) having a column (B) mounted on top thereof, wherein the ratio of the reaction mixture to the reaction mixture is in the range of 1.0:1.0 to 1.0:2.0, preferably in the range of 1.0: The components (meth)acrylic acid and n-butanol are fed in a molar ratio in the range of 1.1 to 1.0:1.5, and wherein, The esterification takes place at a temperature in the range of 80° C. to 150° C., preferably in the range of 100° C. to 130° C. and at an absolute pressure in the range of 0.2 bar to 5.0 bar, preferably in the range of 0.4 bar to 1.5 bar, so as to obtain a reaction effluent (6) and a steam stream produced at the top of the column (B), - withdrawing the vapor stream at the top of the column (B), condensing the vapor stream in a condenser (C) to form an organic phase and an aqueous phase, · continuously separating the organic phase from the aqueous phase by means of a phase separator (D), The reaction effluent (6) is sent to a distillation column (E), Separation of azeotropes in the distillation column (E): a) water and n-butyl (meth)acrylate, b) n-butyl alcohol and n-butyl (meth)acrylate, c) n-butanol and water, d) n-butanol, n-butyl (meth)acrylate and water, wherein the rectification column (E) is operated with a bottom temperature in the range of 80° C. to 150° C., a top temperature in the range of 70° C. to 130° C. and an absolute pressure in the range of 0.2 bar to 5 bar, discharging a gas stream enriched with the azeotrope at the top of the rectification column (E), condensing the gas stream in a condenser (F) to form an organic phase rich in n-butyl (meth)acrylate and an aqueous phase, · continuously separating the organic phase from the aqueous phase by means of a phase separator (G), continuously withdrawing at least a portion of the organic phase from the phase separator (G), wherein the portion of the organic phase which is enriched in n-butyl (meth)acrylate is the crude product stream (15), a reboiler bottom discharge (23) is discharged from the bottom of the rectification column (E), wherein the mass flow ratio between the reboiler bottom discharge (23) and the (meth)acrylic acid fed as a raw material to the reactor (A) is in the range of 0.5 to 5, feeding a reboiler fraction (7) of the discharged reboiler bottoms discharge (23) into a mixer (H), wherein the mass flow ratio between the reboiler fraction (7) and the reboiler bottoms discharge (23) is in the range of 0.01 to 0.50, preferably in the range of 0.05 to 0.08, The mixture (10) produced from the mixer (H) is fed to a downstream extractive phase separator (I), Continuously separating the mixture (10) in the extract phase separator (I) to obtain an organic refined product (11) and an aqueous extract (12) containing a catalyst, wherein the aqueous extract (12) is at least partially refluxed to the reactor (A) and / or the distillation column (E), It is characterized in that External water (19) is fed to the mixer (H), wherein the mass flow ratio between the mass flow of the external water (19) and the reboiler part flow (7) of the discharged reboiler bottom discharge (23) is in the range of 0.08 to 0.50, preferably in the range of 0.10 to 0.

30.

2. A method for continuously preparing n-butyl (meth)acrylate by reacting (meth) acrylic acid with n-butanol in the presence of an acidic catalyst and a polymerization inhibitor, comprising the following steps: The esterification is carried out in a reaction zone (E1), wherein the reaction zone (E1) is located at the bottom of the distillation column (E), wherein the components (meth)acrylic acid and n-butanol are fed in a molar ratio in the range of 1.0:1.0 to 1.0:2.0, preferably in the range of 1.0:1.1 to 1.0:1.5, and wherein the esterification is carried out at a temperature in the range of 80° C. to 150° C., preferably occurs at a temperature in the range of 100° C. to 130° C. and at an absolute pressure in the range of 0.2 bar to 5.0 bar, preferably in the range of 0.4 bar to 1.5 bar, Separation of the azeotrope formed by the esterification: a) water and n-butyl (meth)acrylate, b) n-butyl alcohol and n-butyl (meth)acrylate, c) n-butanol and water, d) n-butanol, n-butyl (meth)acrylate and water, wherein the separation also takes place via the rectification column (E), which is operated with a bottom temperature in the range of 80° C. to 150° C., a top temperature in the range of 70° C. to 130° C. and an absolute pressure in the range of 0.2 bar to 5 bar, preferably in the range of 0.4 bar to 1.5 bar, discharging a gas stream enriched with the azeotrope at the top of the rectification column (E), condensing the gas stream in a condenser (F) to form an organic phase rich in n-butyl (meth)acrylate and an aqueous phase, · continuously separating the organic phase from the aqueous phase by means of a phase separator (G), continuously withdrawing at least a portion of the organic phase from the phase separator (G), wherein the portion of the organic phase which is enriched in n-butyl (meth)acrylate is the crude product stream (15), a reboiler bottom discharge (23) is discharged from the bottom of the rectification column (E), wherein the mass flow ratio between the reboiler bottom discharge (23) and the (meth)acrylic acid fed as a raw material to the reaction zone (E1) is in the range of 0.05 to 0.5, feeding the reboiler part stream (7) of the discharged reboiler bottoms discharge (23) into a mixer (H), wherein the mass flow ratio between the reboiler part stream (7) and the reboiler bottoms discharge (23) is in the range of 0.01 to 1.00, preferably in the range of 0.10 to 0.70, The mixture (10) produced from the mixer (H) is fed to a downstream extractive phase separator (I), The mixture (10) is continuously separated in the extract phase separator (I) to obtain an organic refined product (11) and an aqueous extract (12) containing a catalyst, wherein the aqueous extract (12) is at least partially refluxed to the distillation column (E), characterized in that: External water (19) is fed to the mixer (H), wherein the mass flow ratio between the mass flow of the external water (19) and the reboiler part flow (7) of the discharged reboiler bottom discharge (23) is in the range of 0.08 to 0.50, preferably in the range of 0.10 to 0.

30.

3. The method according to claim 1 or 2, wherein the mixture (10) emerging from the mixer (H) has a temperature in the range of 20°C to 100°C, preferably in the range of 70°C to 95°C at the outlet of the mixer (H).

4. The process according to any one of claims 1 to 3, wherein a portion of the aqueous extract is refluxed to the reactor (A) or the reaction zone (E1), wherein the mass flow ratio between the sub-flow of the aqueous extract and the total mass flow (12) of the aqueous extract is in the range of 0.1 to 1.0, preferably in the range of 0.8 to 1.

0.

5. The process according to claim 1 , wherein in the mixer (H) such a mass flow of external water (19) is added to the reboiler substream (7) of the discharged reboiler bottoms discharge (23) that a phase ratio between the aqueous extract (12) to be obtained and the organic refinery (11) to be obtained is in the range of 0.08 kg / kg to 0.5 kg / kg, preferably in the range of 0.1 kg / kg to 0.3 kg / kg.

6. The method according to any one of claims 1 to 5, wherein a fraction of the organic refinery (11) is conveyed to a cleavage reactor (J), wherein the mass flow ratio between the fraction of the organic refinery (11) and the total mass flow of the organic refinery is in the range of 0.1 to 1.0, preferably in the range of 0.95 to 1.

0.

7. The process according to claim 6, wherein a fraction (8) of the reboiler bottoms discharge (23) is fed to a cleavage reactor (J), the mass flow ratio of the fraction (8) to the reboiler fraction (7) of the reboiler bottoms discharge (23) being in the range of 0.0 to 10.0, preferably in the range of 0.1 to 1.

0.

8. The process according to any one of claims 1 to 7, wherein the reboiler bottoms discharge (23) has a moisture content in the range of 0.1 wt% to 10.0 wt%.

9. The process according to any one of claims 1 to 8, wherein the reboiler bottoms discharge (23) has a catalyst content in the range of 0.1 wt% to 10.0 wt%.

10. The process according to any one of claims 1 to 9, wherein the acidic catalyst contains p-toluenesulfonic acid in the range of 0 wt% to 100 wt%, preferably in the range of 80 wt% to 100 wt%, particularly preferably in the range of 95 wt% to 100 wt%.

11. The process according to any one of claims 1 to 10, wherein the reboiler bottoms discharge (23) is single-phase.

12. The method according to any one of claims 1 to 11, wherein a fraction of the organic phase (14) from the phase separator (G) is refluxed to the distillation tower (E), the reflux ratio of the fraction relative to the organic phase being in the range of 0.1 to 1.0, and a fraction of the aqueous phase (16) from the phase separator (G) is refluxed to the distillation tower, the reflux ratio of the fraction relative to the aqueous phase being in the range of 1 to 10.

13. The process according to any one of claims 1 to 12, wherein the acidic catalyst is present in the reaction effluent produced in the reaction zone (E1) of the distillation column (E) or the reactor (A) at a concentration in the range of 0.1 wt% to 10.0 wt%.

14. The process according to claim 1 or any one of claims 3 to 13, wherein a fraction of the aqueous extract (12) is fed to the reactor (A) in a mass flow ratio of the fraction to the entire reboiler bottoms discharge (23) in the range of 0.01 to 0.50, preferably in the range of 0.01 to 0.30.

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