Separation of n-methylethylenediamine from EDA-containing mixtures

Abstract

To provide a method for purifying a mixture comprising water (H2O), ethylenediamine (EDA), and N-methylethylenediamine (NMEDA) so as to realize EDA as specified from the mixture.SOLUTION: Provided is a method for producing ethylenediamine (EDA) from a mixture comprising water (H2O), EDA, and N-methylethylenediamine (NMEDA) by feeding the mixture into a rectification column, the rectification column being operated at a top pressure in the range of 5.0-7.5 bar.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a method for separating N-methylethylenediamine from an EDA-containing mixture. [Background technology]

[0002] Ethylenediamine is primarily used as an intermediate for the production of bleach activators, crop protection agents, pharmaceuticals, lubricants, textile resins, polyamides, paper adjuvants, gasoline additives, and many other materials.

[0003] There are numerous known methods for preparing EDA (see, for example, Ullmann's Encyclopedia of Industrial Chemistry, "Amines Aliphatic", section 8.1.1., DOI:10.1002 / 1436007.a02_001).

[0004] In the preparation of ethylenediamine, N-methylethylenediamine (NMEDA) may be formed by a side reaction.

[0005] For example, in the reaction of monoethanolamine (MEA) with ammonia to give EDA, the decomposition reaction of monoethanolamine can directly give carbon monoxide (CO) and methylamine (decarbonylation), which can then react directly with more monoethanolamine to give NMEDA.

[0006] When aminoethanolamine (AEEA) is decomposed directly to NMEDA by decarbonylation, NMEDA can also form in the dimerization of monoethanolamine to AEEA.

[0007] NMEDA may also be formed in the preparation of EDA from C1 units, for example, hydrogen cyanide and formaldehyde.

[0008] Not only NMEDA but also poly-N-methylated ethylenediamines, such as bis(N-methyl 1,2-ethanediamine), may form, but in terms of quantity, the formation of NMEDA typically predominates.

[0009] For most industrial applications, the market demands a purity of at least 99.5% by weight of EDA. Secondary organic components such as NMEDA may be present in proportions of up to 0.5% by weight. Furthermore, the water content can be up to 0.5% by weight.

[0010] More specifically, in many industrial applications, the purity of EDA is specified when the proportion of NMEDA is less than 1000 ppm by weight.

[0011] As a result of its preparation, EDA with a higher NMEDA content must be correspondingly post-treated to obtain EDA with the required specifications.

[0012] In a mixture containing EDA, water, and NMEDA, the NMEDA is typically separated from the EDA and water under azeotropic conditions.

[0013] EP 2487151 (DOW) discloses a method for depleting alkylethyleneamines from an ethyleneamine mixture, in which a mixture consisting of ethylenediamine, water, and one or more alkylethylenediamines is subjected to conditions under which an azeotrope between water and the alkylethyleneamine is formed, and the resulting mixture is separated from the remaining composition. The pressure of the rectification column in which the azeotrope of water and alkylethylenediamine is separated is disclosed to be in the range of 1.01 to 2.12 bar, preferably 1.5 to 1.98 bar. In Example 1, the distillation is carried out at an overhead pressure of 1.634 bar, an overhead temperature of 115°C, and a bottom temperature of 176°C. Besides these technical details related to the distillation, the disclosure does not contain any further technical information regarding the measures that a person skilled in the art should take to form the azeotrope of alkylethyleneamines and water.

[0014] A further method for separating NMEDA from EDA and water is disclosed in EP 2507202. This disclosure teaches that removal of NMEDA is carried out in a rectification column at overhead pressures ranging from 0.01 bar to 4 bar, and that the distilled mixture contains at least a sufficient amount of water such that the condition H=a×X / Y is satisfied, where H is the weight fraction of water in the distilled mixture, X is the weight fraction of water, Y is the weight fraction of EDA, and a is a real number having a value of 0.9 or greater, at the azeotropic point of the binary mixture of water and EDA at the column pressure of interest.

[0015] A recent disclosure (WO2019 / 081284) discloses a process for separating NMEDA from EDA and water, in which the NMEDA separation column contains 50 to 140 theoretical plates and is operated at a bottom temperature of 155°C or less. NMEDA is withdrawn overhead, and an EDA / water azeotrope is withdrawn at the bottom.

[0016] After removal of the NMEDA, the EDA / water mixture is separated.

[0017] DE 1258413 discloses the separation of EDA and water in a single dehydration column operated at a pressure at which the azeotrope between water and EDA collapses, so that water can be withdrawn overhead from the distillation column and EDA and other amines are withdrawn via a sump.

[0018] Alternatively, EDA and water can be separated in two columns operated at different pressures (dual pressure distillation or pressure swing distillation) (see Fulgueras, AM, Poudel, J., Kim, DS et al., Korean J. Chem. Eng. (2016) 33:46. https: / / doi.org / 10.1007 / s11814-015-0100-4). [Prior art documents] [Patent documents]

[0019] [Patent Document 1] EP2487151(DOW) [Patent Document 2] EP2507202 [Patent Document 3] WO2019 / 081284 [Patent Document 4] DE1258413 [Non-patent literature]

[0020] [Non-Patent Document 1] Ullmann's Encyclopedia of Industrial Chemistry, "Amines Aliphatic", section 8.1.1., DOI:10.1002 / 1436007.a02_001 [Non-patent document 2] Fulgueras, AM, Poudel, J., Kim, DS, et al., Korean J. Chem. Eng. (2016)33:46. https: / / doi.org / 10.1007 / s11814-015-0100-4 Summary of the Invention [Problem to be solved by the invention]

[0021] It was an object of the present invention to provide a method for purifying a mixture of EDA, NMEDA, and water to achieve on-specification EDA with a low NMEDA content, preferably an NMEDA content of 1000 ppm by weight or less. A further object of the present invention was to reduce the number of columns required for separation of the three components and / or the size of the equipment required in order to reduce investment costs. [Means for solving the problem]

[0022] The object of the present invention is achieved by a process for producing ethylenediamine (EDA) from a mixture comprising water (HO), EDA, and N-methylethylenediamine (NMEDA) by feeding the mixture to a rectification column, wherein the rectification column is operated at an overhead pressure in the range of 5.0 to 7.5 bar.

[0023] Surprisingly, it has been found that NMEDA and water can be efficiently separated from EDA in a single rectification column when the rectification column is operated over a narrow pressure range. Thus, the number of rectification columns required to obtain EDA that meets market-required quality specifications can be reduced compared to the state of the art, and / or the size and cost of the required equipment can be reduced. [Brief explanation of the drawings]

[0024] [Figure 1] 1 is a graph illustrating the concentration of NMEDA at the top of a water separation column and reflux ratio as a function of column pressure. [Figure 2] 1 is a graph illustrating NMEDA concentration in product EDA as a function of overhead pressure for EDA-water separation. DETAILED DESCRIPTION OF THE INVENTION

[0025] The following abbreviations are used below: AEEA: Aminoethylethanolamine AEP: Aminoethylpiperazine DETA: Diethylenetriamine EDA: Ethylenediamine EDC: ethylene dichloride HEP: Hydroxyethylpiperazine HPA: Heavy Polyamine MEA: Monoethanolamine MEG: Monoethylene glycol NMEDA: N-methylethylenediamine PEHA: Pentaethylenehexamine PIP: piperazine TEPA: tetraethylenepentamine TETA: Triethylenetetramine

[0026] Unless otherwise indicated, pressure figures relate to absolute pressure figures.

[0027] mixture According to the present invention, EDA is prepared from a mixture containing NMEDA, EDA, and water.

[0028] Preparation of the mixture Such a mixture can be prepared by first carrying out the EDA preparation process, after which the ammonia and hydrogen are generally removed.

[0029] In a preferred embodiment, the EDA mixture obtained after removal of ammonia and / or hydrogen is used directly in the process of the invention without further work-up steps.

[0030] In a further embodiment, the EDA-mixture obtained after removal of ammonia and / or hydrogen is subjected to complete or partial removal of higher boiling amines (higher boiling amine removal).

[0031] EDA preparation method The first step in the preparation of a mixture that can be used in the method of the present invention is typically the EDA preparation method.

[0032] EDA can be prepared by a variety of methods.

[0033] In one preferred embodiment (MEA method), EDA is prepared by reaction of MEA with NH3.

[0034] In a more preferred embodiment (Method C1), EDA is prepared by the reaction of formaldehyde, hydrogen cyanide, ammonia, and hydrogen.

[0035] In a further preferred embodiment (EDC process), EDA is prepared by reaction of ethylene dichloride with ammonia (EDC process).

[0036] In a more preferred embodiment (MEG method), EDA can be prepared by reaction of MEG with ammonia.

[0037] MEA Method The reaction of MEA with ammonia is described, for example, in US 2,861,995, DE-A-1172268, and US 3,112,318. A summary of various process variants of the reaction of MEA with ammonia can be found, for example, in PERP Report No. 138 "Alkyl Amines", SRI International, 03 / 1981 (especially pages 81-99, 117).

[0038] The reaction of monoethanolamine with ammonia is preferably carried out in a fixed bed reactor over a transition metal catalyst at 150-250 bar and 160-210°C, or over a zeolite catalyst at 1-20 bar and 280-380°C.

[0039] Preferred transition metal catalysts used include Ni, Co, Cu, Ru, Re, Rh, Pd, or Pt, or a mixture of two or more of these metals, on an oxide support (e.g., Al2O3, TiO2, ZrO2, SiO2).

[0040] Preferred zeolite catalysts are mordenite, faujasite, and chabazite.

[0041] To achieve maximum EDA selectivity, a molar ratio of ammonia to monoethanolamine of 6-20, preferably 8-15, for transition metal catalysis and 20-80, preferably 30-50, for zeolite catalysis is generally used.

[0042] The MEA conversion is generally kept between 10% and 80%, preferably between 40-60%.

[0043] In continuous operation, a catalyst space velocity in the range of 0.3 to 0.6 kg / (kg×hr) (kg MEA per kg catalyst per hour) is preferably established.

[0044] To maintain catalytic activity, when a metal catalyst is used, preferably 0.05-0.5 wt % hydrogen (based on the MEA+NH3+H2 reaction input) is further fed to the reactor.

[0045] C1 method The reaction product may also be prepared by the reaction of formaldehyde, hydrogen cyanide, ammonia, and hydrogen.

[0046] For example, US Pat. No. 2,519,803 discloses a method for preparing ethylenediamine by hydrogenation of a partially purified aqueous reaction mixture obtained from the amination of formaldehyde cyanohydrin (FACH) and containing aminoacetonitrile as an intermediate. Formaldehyde cyanohydrin can then be obtained by reacting formaldehyde with hydrogen cyanide. Descriptions of methods for preparing FACH can be found, for example, in application PCT / EP2008 / 052337, page 26, and in application WO-A1-2008 / 104582, page 30 (variant A) and variant B), which are expressly incorporated herein by reference.

[0047] DE-A 1 154 121 further relates to a process for preparing ethylenediamine in a "one-pot" process, in which the reactants hydrogen cyanide, formaldehyde, ammonia and hydrogen are reacted in the presence of a catalyst.

[0048] WO-A1-2008 / 104592 relates to a method for preparing EDA by hydrogenation of aminoacetonitrile, which is typically obtained by reaction of formaldehyde cyanohydrin with ammonia, which is then generally prepared from hydrogen cyanide and ammonia.

[0049] Preferably, the reaction product comprising EDA and NMEDA is prepared by the method described in WO-A1-2008 / 104592, hereby expressly incorporated by reference.

[0050] EDC method EDA can also be prepared by the reaction of ethylene dichloride with ammonia (EDC method). The reaction of EDC with ammonia is described, for example, in EP 2346809, the PERP report mentioned above, and cited in the literature.

[0051] MEG method In another embodiment, EDA can be prepared by the reaction of MEG with ammonia.The reaction of MEG with ammonia can be carried out in liquid phase or gas phase.Gas phase reaction is disclosed in, for example, CN102190588 and CN102233272, and liquid phase reaction is disclosed in, for example, US4,111,840, US3,137,730, DE172268 and WO2007 / 093514.

[0052] Composition of reaction products from EDA preparation process The mixture prepared by the above-described preparation method contains EDA, NMEDA, and water.

[0053] Depending on the preparation method, the mixture is also generally hydrogen ammonia Higher boiling amines Ethylene glycol (MEG), and organic by-products Also includes.

[0054] Higher boiling amines refer hereinafter to acyclic and cyclic compounds containing two or more amine groups (primary, secondary, or tertiary), or one or more amine groups and one or more OH groups, which have a higher boiling point than EDA at the same pressure.

[0055] Examples of higher boiling amines are piperazine (PIP), monoethanolamine (MEA), diethylenetriamine (DETA), aminoethylethanolamine (AEEA), triethylenetetramine (TETA), and higher ethyleneamines (higher ethyleneamines below refer to higher boiling ethyleneamines that have a higher boiling point than TETA, e.g., TEPA).

[0056] Organic by-products, below, refers to all unconverted raw materials and reaction products that are not higher boiling amines, MEG, water, hydrogen, ammonia, or NMEDA.

[0057] Ammonia removal The mixture from the aforementioned preparation methods generally contains ammonia.

[0058] The amount of ammonia in the reaction product is typically in the range of 50% to 90% by weight, more preferably in the range of 60% to 85% by weight, and most preferably in the range of 70% to 80% by weight.

[0059] Before the reaction product is used in the process of the present invention, ammonia and / or hydrogen are preferably separated from the mixture obtained by the preparation process described above.

[0060] The hydrogen and ammonia can be separated from the reaction mixture by methods known to those skilled in the art.

[0061] Preferably, the removal of ammonia and hydrogen is carried out by distillation or rectification, which can be carried out in a still or rectification column.

[0062] In the case of rectification, a column having a rectifying section and a stripping section can be used.

[0063] If a large reduction of secondary components from ammonia, such as methylamine, is required, the use of a rectification section is advantageous.

[0064] To reduce the energy demands of rectification, it is preferable to use a column without a rectifying section, since reflux is not required.

[0065] The removal of hydrogen and ammonia can be done in a single stage at a specific pressure, or staged in a series of setups, varying the pressure to match bottom and overhead temperatures, as practicable.

[0066] Preferably, the pressure and composition at the top and bottom of the column are selected so that the condensation temperature is higher than 20° C., more preferably higher than 30° C., most preferably higher than 35° C. When the condensation temperature is within the ranges mentioned, the condenser can generally be cooled with cooling water at a temperature of 20 to 80° C., preferably 30 to 70° C., more preferably 35 to 50° C.

[0067] The column bottom temperature is preferably 275° C. or lower, more preferably 260° C. or lower, and most preferably 250° C. or lower. The column bottom temperature is preferably in the range of 200 to 275° C., more preferably in the range of 210 to 260° C., and most preferably in the range of 220 to 250° C.

[0068] The pressure setting is important for the temperature setting, but the distillation temperature is also influenced by the specific concentration setting. For example, the overhead condensation temperature can be increased by withdrawing not only ammonia but also other components with a higher boiling point than ammonia, such as water, at the top of the column. In this case, it is advantageous to operate the condenser in back-mix mode (known to those skilled in the art as "closed condensation") so that condensation occurs within a narrow temperature range. Condensers suitable for this type of condensation are condensers in which condensation occurs simultaneously with the outflow of condensate, or direct condensers in which a pumped, circulated cryogenic liquid is brought into contact with the vapor to be condensed.

[0069] Preferably, in the first stage, most of the ammonia is distilled off at high pressure, for example, above 10 bar, preferably above 15 bar, more preferably above 20 bar, while still allowing for a certain ammonia concentration in the bottom of the column and establishing the desired bottom temperature. Hydrogen present in the reaction product is also removed overhead. Preferably, in the first condenser, most of the ammonia is condensed from the vapor at a relatively high temperature. Here, hydrogen is enriched in the gas phase according to the dew point curve of the mixture. Since complete condensation of the mixture is not possible at standard ambient temperatures, this results in a gaseous output in the condenser. Preferably, this output can be introduced into a second condenser, where the temperature can be further reduced by cooling with a lower temperature coolant, thereby further depleting the ammonia from the gas phase and producing a second exit gas with a lower ammonia content. The exit gas from the first or second condenser can also be treated by scrubbing to recover most of the ammonia present therein. This can be achieved by using standard methods known to those skilled in the art, such as a scrubbing column or a Venturi scrubber. This involves contacting the exhaust gas with a cooling liquid, preferably water, preferably having a boiling point higher than that of ammonia. In a particularly preferred variant, the scrubbing water is taken from another stage of the same process. This results in an ammonia-enriched liquid stream, generally containing the removed hydrogen, and an ammonia-depleted exhaust gas. This exhaust gas can be sent to incineration or recycled to the EDA production process. More preferably, the ammonia-enriched stream is recycled to ammonia removal, for example to the stage where the reaction product is introduced.

[0070] More preferably, the ammonia-containing bottoms output from the first stage of ammonia removal is conducted to a second stage operated at a lower pressure than the first stage. The pressure of the second stage is adjusted so that the desired bottoms temperature is established and, if possible, so that ammonia is present only in low concentrations in the bottoms output from the second stage. The condensation temperature at the top of the second stage is adjusted by entrainment of a component having a higher boiling point than ammonia, preferably water, so that the resulting mixture can be condensed with a desired coolant, such as river water or ambient air. In a particularly preferred variant, the ammonia-containing mixture withdrawn from the top is recycled to the first stage.

[0071] The removal of hydrogen and ammonia can also be split into a further (0th) stage preceding the first stage and operating at a lower bottom temperature than the first stage but at the same pressure, so that part of the ammonia can be evaporated at a lower temperature. In this way, cheaper energy at lower temperatures, e.g., waste heat, can be used to save on energy costs. Preferably, the vapor from the 0th stage is condensed in the same condenser as the vapor from the first stage.

[0072] Composition of the output from ammonia removal After removal of ammonia and optionally hydrogen, a mixture is obtained containing not only water, EDA, and NMEDA, but also generally higher boiling amines and organic by-products.

[0073] After removal of NH3 and optionally hydrogen, the output from the hydrogen / ammonia removal can be used directly in the process of the present invention.

[0074] The mixture obtained after removal of ammonia and which can be used in the process of the present invention preferably contains 20% to 75% by weight of EDA, more preferably 30% to 65% by weight of EDA, and most preferably 35% to 60% by weight of EDA.

[0075] The weight ratio of EDA to NMEDA is preferably 1:0.0005 (500 ppm by weight of NMEDA) to 1:0.2 (200,000 ppm by weight of NMEDA), more preferably 1:0.001 (1,000 ppm by weight) to 1:0.05 (50,000 ppm by weight of NMEDA), and most preferably 1:0.005 (5,000 ppm by weight of NMEDA) to 1:0.01 (10,000 ppm by weight of NMEDA).

[0076] The proportion of ammonia is preferably less than 5% by weight of ammonia, more preferably less than 2% by weight of ammonia, more preferably less than 1% by weight of ammonia, especially preferably less than 0.5% by weight.

[0077] The proportion of higher boiling amines and other high boilers, such as MEG, is preferably in the range of 5% to 90% by weight, more preferably in the range of 30% to 85% by weight, and most preferably in the range of 40% to 70% by weight.

[0078] In one preferred embodiment, the weight ratio of the aforementioned components in the mixture used in the method is preferably EDA:NMEDA = 1:0.0005 to 0.2 EDA:ammonia = 1:0-0.05 EDA: higher boiling point amine=1:0 to 2.0, and EDA:Organic byproduct=1:0~0.05 More preferably EDA:NMEDA = 1:0.001 to 0.05 EDA:ammonia = 1:0-0.025 EDA: higher boiling point amine=1:0.05 to 1, and EDA:organic by-products=1:0.0001 to 0.025, and Most preferably EDA:NMEDA = 1:0.005-0.01 EDA:ammonia = 1:0-0.025 EDA: higher boiling point amine=1:0.05 to 1, and EDA:Organic byproduct=1:0.0001~0.025 is.

[0079] In a further preferred embodiment, EDA is prepared by reaction of MEG with NH. In this further particularly preferred embodiment, the weight ratio of the aforementioned components in the mixture used in the process is preferably EDA:NMEDA = 1:0.0005 to 0.2 EDA:ammonia = 1:0-0.05 EDA: higher boiling point amine=1:0 to 2.0, and EDA:MEG=1:0.5~10.0 EDA:Organic byproduct=1:0~0.05 More preferably EDA:NMEDA = 1:0.001 to 0.05 EDA:ammonia = 1:0-0.025 EDA: higher boiling point amine=1:0.05 to 1, and EDA:MEG=1:1.0~8.0 EDA:organic by-products=1:0.0001 to 0.025, and Most preferably EDA:NMEDA = 1:0.005-0.01 EDA:ammonia = 1:0-0.025 EDA: higher boiling point amine=1:0.05 to 1, and EDA:MEG=1:2.0~5.0 EDA:Organic byproduct=1:0.0001~0.025 is.

[0080] The mixture obtained after removal of ammonia can be used directly in the process of the present invention.

[0081] Removal of higher boiling amines As an alternative to direct use of the mixture after removal of ammonia, it is possible to partially or completely remove the higher boiling amines and other high boilers, such as MEG.

[0082] In one preferred embodiment, after removal of ammonia, all higher boiling amines (including PIP) are removed.

[0083] This is preferably carried out in a rectification column operated so that the higher boiling amine is obtained in the lower part of the column, preferably at the bottom, and a mixture comprising water, NMEDA, and EDA is withdrawn in the upper region of the column, preferably at the top.

[0084] The exact operating conditions of the rectification column can be routinely determined by those skilled in the art by conventional calculation methods using the known vapor pressures and evaporation equilibria of the components introduced into the rectification column, depending on the separation performance of the column used.

[0085] At the top of the column, a mixture is obtained which can be used in the process of the invention to remove NMEDA and EDA.

[0086] In a further embodiment, all higher boiling amines and other high boilers, such as MEG, except for PIP, are removed.

[0087] This is preferably carried out in a rectification column operated so that the higher-boiling amines other than PIP are obtained in the lower part of the column, preferably at the bottom, and a mixture comprising water, NMEDA, EDA, and PIP is withdrawn in the upper region of the column, preferably at the top.

[0088] The exact operating conditions of the rectification column can be routinely determined by those skilled in the art by conventional calculation methods using the known vapor pressures and evaporation equilibria of the components introduced into the rectification column, depending on the separation performance of the column used.

[0089] At the top of the column, a mixture is obtained which can be used in the process of the invention to remove NMEDA and EDA.

[0090] Composition of the mixture after removal of higher boiling amines In one embodiment where higher boiling amines and other high boilers, such as MEG, are partially or completely removed, the weight ratios of the aforementioned components of the mixture used in the process are preferably EDA:NMEDA = 1:0.0005 to 0.2 EDA:ammonia = 1:0-0.05 EDA:PIP=1:0~0.05 EDA: higher boiling point amine=1:0 to 0.1, and EDA:MEG=1:0~0.1 EDA:Organic byproduct=1:0~0.05 More preferably EDA:NMEDA = 1:0.001 to 0.05 EDA:PIP=1:0~0.02 EDA:ammonia = 1:0-0.025 EDA: higher boiling point amine = 1:0 to 0.05, and EDA:MEG=1:0-0.05 EDA:organic by-products=1:0.0001 to 0.025, and Most preferably EDA:NMEDA = 1:0.005-0.01 EDA:ammonia = 1:0-0.025 EDA:PIP=1:0~0.01 EDA: higher boiling point amine = 1:0 to 0.02, and EDA:MEG=1:0~0.001 EDA:Organic byproduct=1:0.0001~0.025 is.

[0091] In one embodiment in which higher boiling amines and other high boilers other than PIP, such as MEG, are partially or completely removed, the weight ratios of the aforementioned components of the mixture used in the process are preferably EDA:NMEDA = 1:0.0005 to 0.2 EDA:ammonia = 1:0-0.05 EDA:PIP=1:0.1~2 EDA: higher boiling point amine=1:0 to 0.1, and EDA:MEG=1:0~0.1 EDA:Organic byproduct=1:0~0.05 More preferably EDA:NMEDA = 1:0.001 to 0.05 EDA:PIP=1:0.2~1 EDA:ammonia = 1:0-0.025 EDA: higher boiling point amine = 1:0 to 0.05, and EDA:MEG=1:0-0.05 EDA:organic by-products=1:0.0001 to 0.025, and Most preferably EDA:NMEDA = 1:0.005-0.01 EDA:ammonia = 1:0-0.025 EDA:PIP=1:0.3~0.5 EDA: higher boiling point amine = 1:0 to 0.02, and EDA:MEG=1:0~0.001 EDA:Organic byproduct=1:0.0001~0.025 is.

[0092] Amount of water: The mixture supplied to the method of the present invention also contains water. The water content in the mixture containing EDA, NMEA, and water is preferably in the range of 10 to 80 weight percent, more preferably in the range of 15 to 70 weight percent, even more preferably in the range of 20 to 50 weight percent, and most preferably in the range of 25 to 50 weight percent.

[0093] EDA-dehydration The mixture containing EDA, NMEDA, and water is fed to a rectification column (EDA dehydration column).

[0094] In the EDA dehydration column, separation into a low-boiling fraction containing water and most of the NMEDA, and a high-boiling fraction containing a major proportion of EDA and any higher-boiling amines and any MEG, is generally carried out if these have not already been partially or completely removed from the mixture beforehand.

[0095] The rectification can be carried out in rectification equipment such as tray columns, e.g., bubble-cap tray columns, sieve tray columns, dual-flow tray columns, valve tray columns, baffle tray columns, or columns equipped with random or structured packing. Preferably, low-pressure-drop internals are used, such as, for example, sheet metal packings, e.g., Mellapak 250Y or structured packings in the form of Montz Pak (type B1-250). Packings with lower or higher specific surface areas can also be present, or fabric packings or other forms of packing, e.g., Mellapak 252.Y, can be used. The advantage of using such internals is the lower pressure drop and lower holdup of specific liquid, compared to, for example, valve trays. The internals can be arranged in one or more beds.

[0096] In a preferred embodiment, the rectification of the present invention is carried out in a column equipped with trays (tray column). Tray columns have been found to improve efficiency compared to packed columns for aqueous EDA mixtures. Most preferably, the column is a bubble-cap tray column, a sieve tray column, a dual-flow tray column, a valve tray column, or a baffle tray column. Most preferably, the column is a bubble-cap tray column or a sieve tray column.

[0097] According to the process of the present invention, the pressure of the EDA dehydration column is in the range of 5.0 to 7.5 bar, preferably in the range of 5.1 to 7.0 bar, more preferably in the range of 5.2 to 6.5 bar, even more preferably in the range of 5.3 to 6.3 bar, and most preferably in the range of 5.5 to 6.0 bar.

[0098] In a preferred embodiment, the EDA dehydration column is operated at an overhead pressure where the EDA and water form a non-azeotrope or non-azeotropic mixture, where the EDA and water have different boiling points and can be separated by distillation.

[0099] Surprisingly, it has been found that when rectification is carried out within the pressure range of the present invention, the majority of the NMEDA is separated from the water as a lower boiling fraction, and it has also been found that pressures within the claimed and preferred ranges can reduce overhead EDA losses.

[0100] The theoretical plate number of the EDA dehydration column is generally in the range of 20-120, preferably 30-110, and more preferably 35-100.

[0101] In a preferred embodiment, the number of theoretical plates is in the range of 40 to 90. If the number of theoretical plates is sufficiently high, EDA losses in the overhead fraction withdrawal can be further reduced. At pressures slightly above the pressure at which the azeotrope of EDA with water is formed, the difference in vapor pressure or boiling point between water and EDA can still be low, resulting in improved separation using a column having a number of theoretical plates within the aforementioned range.

[0102] In an EDA dehydration column, the energy required to evaporate the mixture containing EDA, NMEDA, and water is typically introduced by a bottom evaporator, which is typically a natural circulation evaporator or a forced circulation evaporator. Alternatively, evaporators with short residence times, such as falling film evaporators, spiral tube evaporators, wiped film evaporators, or short path evaporators, can be used.

[0103] The feed containing EDA, NMEDA, and water is preferably introduced into the EDA dehydration column at a spatial region between 50% and 100% of the theoretical plates. For example, the feed may be overhead. Preferably, the feed is introduced between 60% and 80% of the theoretical plates, more preferably between 65% and 80% of the theoretical plates. For example, if the column has 50 theoretical plates, the feed is preferably introduced between 33 and 40 (65-80%) of the theoretical plates.

[0104] In a preferred embodiment, the EDA dehydration column generally comprises a condenser operated at a temperature at which a major portion of the water is condensed at a corresponding overhead pressure.

[0105] Generally, the operating temperature of the condenser is in the range of 150 to 230°C, preferably in the range of 160 to 195°C.

[0106] The condensers used may be, for example, condensers with cooling coils or spiral tubes, jacketed tube condensers, and shell-and-tube heat exchangers.

[0107] A condensate containing primarily water and NMEDA is generally obtained in the condenser.

[0108] Preferably, the condensate comprises at least 98 wt.-% water, preferably at least 99 wt.-% water, more preferably at least 99.5 wt.-% water.

[0109] Preferably the condensate contains no more than 2 wt.-% EDA, preferably no more than 1 wt.-% EDA, more preferably no more than 0.5 wt.-% EDA.

[0110] Preferably, the condensate obtained in the condenser is recycled to the top of the EDA dehydration column to an extent of 50% by volume or more, preferably to an extent of more than 65% by volume or more, more preferably to an extent of 70% by volume or more, based on the total condensate volume.

[0111] In a preferred embodiment, the reflux ratio, the ratio of the condensate stream returned to the column to the condensate stream removed from the process, is preferably in the range of 1:1 to 5.0:1, more preferably in the range of 1.25:1 to 4.75:1, even more preferably in the range of 1.5:1 to 4.5:1, still more preferably in the range of 1.75:1 to 4.25:1, and most preferably in the range of 2.0:1 to 4.0:1. In this embodiment, the loss of EDA at the top of the EDA dehydration column can be reduced while the concentration of NMEDA at the bottom of the EDA dehydration column is reduced without sacrificing column energy consumption (reboiler duty) or column throughput.

[0112] The non-recycled condensate can be sent directly to waste, for example, by introduction into a wastewater treatment plant.

[0113] More preferably, the non-recycled condensate from the EDA dehydration column is fed to a wastewater treatment column to separate the remaining organic components, such as NMEDA, from the water.

[0114] The wastewater treatment column is preferably operated at 0.5 to 2 bar, more preferably 0.75 to 1.5 bar, even more preferably 0.9 to 1.1 bar. In a most preferred embodiment, the wastewater treatment column is operated at atmospheric pressure.

[0115] In wastewater treatment columns, the energy required to evaporate the mixture containing NMEDA and water is typically provided by a bottom evaporator, which is typically a natural circulation evaporator or a forced circulation evaporator. Alternatively, evaporators with short residence times, such as falling film evaporators, spiral tube evaporators, wiped film evaporators, or short path evaporators, can be used.

[0116] The number of theoretical plates in the wastewater treatment column is generally in the range of 5 to 50, preferably 10 to 40, more preferably 15 to 30, and most preferably 18 to 25.

[0117] The feed to the wastewater treatment column containing NMEDA and water is preferably introduced into the spatial region between 40% and 60% of the theoretical plates of the rectification column.

[0118] In a preferred embodiment, the wastewater treatment column is generally equipped with a condenser operated at a temperature at which the majority of the water is condensed at the corresponding overhead pressure. Generally, the operating temperature of the condenser is in the range of 15 to 50°C, preferably 20 to 40°C.

[0119] The condensers used may be, for example, condensers with cooling coils or spiral tubes, jacketed tube condensers, and shell-and-tube heat exchangers.

[0120] In the condenser, a condensate containing mainly water is generally obtained.

[0121] Preferably, the condensate obtained in the condenser is recycled to the top of the wastewater treatment column, preferably to an extent of 50% by volume or more, preferably to an extent of more than 65% by volume or more, more preferably to an extent of 70% by volume or more, based on the total condensate volume.

[0122] The high boiling output from the wastewater treatment column obtained at the bottom of the wastewater treatment column essentially comprises amines, e.g., NMEDA, and water. The sump product comprising water and NMEDA is preferably sent to a furnace for incineration.

[0123] The high boiling output from the EDA dehydration column contains essentially EDA and any higher boiling amines and any MEG.

[0124] Preferably, the high boiling output from the EDA dehydration column contains less than 1.0 wt% water, preferably less than 0.6 wt% water, more preferably less than 0.5 wt% water.

[0125] Preferably, the high boiling output from the EDA dehydration column contains less than 0.5 wt% NMEDA, more preferably less than 0.3 wt% NMEDA, and most preferably less than 0.1 wt% NMEDA.

[0126] For example, to obtain on-specification EDA, the product can be separated into its individual components or suitable fractions, as described below.

[0127] EDA-PIP removal When the high-boiling output from the EDA dehydration column contains both EDA and higher-boiling amines, with or without MEG, it is generally first separated into a lower-boiling fraction containing PIP and EDA, and a higher-boiling fraction generally containing PIP and any amines with higher boiling points than MEG. This separation can also be carried out in a rectification column (EDA-PIP removal). The exact operating conditions of the rectification column can be routinely determined by those skilled in the art by conventional calculations using the known vapor pressures and evaporation equilibria of the components introduced into the rectification column, depending on the separation performance of the column used. For example, EDA-PIP removal can be carried out as described in EP2507202 or the aforementioned PRP report, pages 89 et seq., related to Figure 6.1, and are expressly incorporated herein by reference.

[0128] The higher boiling fraction is preferably withdrawn at the bottom of the rectification column and generally contains higher boiling amines.

[0129] The higher-boiling amines can be separated into pure substances or suitable fractions by conventional methods, in particular by rectification. The work-up of higher-boiling amines is also described in the aforementioned PRP report, from page 89 onwards in relation to Figure 6.1, or in EP 2487151, EP 2507202 or EP 2346809.

[0130] Preferably, the lower-boiling fraction withdrawn in the upper region of the column typically contains EDA and PIP and is generally primarily free of other higher-boiling amines. The proportion of higher-boiling amines (excluding piperazine) is generally less than 0.2% by weight, preferably less than 0.1% by weight, more preferably less than 0.05% by weight. To obtain EDA on specification, the lower-boiling EDA-PIP fraction is generally sent to a further purification stage (a step for purifying the EDA distillate).

[0131] Purifying the EDA distillate The low-boiling fraction from the EDA / PIP removal is typically introduced into a further rectification column (a step for purifying the EDA distillate), preferably operated so that EDA is obtained overhead and piperazine can be withdrawn at the bottom. The exact operating conditions of the rectification column can be routinely determined by those skilled in the art by conventional calculation methods using the known vapor pressures and evaporation equilibria of the components introduced into the rectification column, depending on the separation performance of the column used. For example, EDA-PIP removal can be carried out as described in EP2507202 or the aforementioned PRP report, pages 89 et seq. and Figure 6.1, which are expressly incorporated herein by reference.

[0132] In the condenser, a condensate is generally obtained which contains mainly EDA but also very small amounts of NMEDA.

[0133] The low-boiling EDA-containing fractions thus obtained are generally primarily free of higher-boiling amines such as piperazine, the proportion of which is generally less than 0.5% by weight, preferably less than 0.3% by weight, more preferably less than 0.2% by weight.

[0134] In addition, the low-boiling EDA-containing fraction preferably contains 99.5% by weight or more of EDA.

[0135] The concentration of NMEDA in the EDA-containing fraction is preferably in the range of 0.001% by weight to 0.1% by weight, preferably in the range of 0.005% by weight to 0.08% by weight, more preferably in the range of 0.01% by weight to 0.05% by weight.

[0136] Preferred combinations The method steps detailed above and respective embodiments of the individual method steps can be combined with each other as appropriate, and the present invention also encompasses suitable combinations of the method steps detailed above and respective embodiments.

[0137] More specifically, the following combinations are preferred: The EDA process, a method for preparing EDA, in combination with ammonia removal, rectification according to the present invention, EDA-PIP removal, and purifying the EDA distillate. The combination of the MEG process for preparing EDA with ammonia removal, the inventive rectification, EDA-PIP removal, and purification of the EDA distillate. The combination of the C1 process for preparing EDA with ammonia removal, the inventive rectification, EDA-PIP removal, and the purification of the EDA distillate. The combination of the EDC process for preparing EDA with ammonia removal, the inventive rectification, EDA-PIP removal, and the step of purifying the EDA distillate.

[0138] Benefits and Uses The EDA obtained after the step of purifying the EDA distillate is advantageously suitable for applications where extremely high purity of the EDA is important.

[0139] Since the functionality of EDA is not reduced by the formation of NMEDA, the EDA thus obtained can be used, for example, in the preparation of high molecular weight polymers, such as polyamides. For example, the EDA thus obtained can be used as a high-purity chemical for use in electronic chemicals, crop protection agents, pesticides, epoxy resins, complexing agents, or in the leather industry (leather chemicals), paper industry (paper chemicals), automotive and fuel industries (fuel additives, gasoline additives, lubricants), textile industry (textile resins and polymers), or detergent industry (detergents, bleaching additives). The use of high-purity chemicals can increase the yield of the final product, reduce the concentration of unwanted by-products, and also improve the use and processing properties in the intended field of use. For example, in polycondensation reactions, such as the preparation of epoxy resins or polyamides, NMEDA can cause unwanted chain termination reactions, which can reduce the degree of polymerization or density at network points. Therefore, the present application is also directed to processes comprising the steps of producing the EDA of the present invention and further converting the EDA into polyamides, electronic chemicals, crop protection agents, pesticides, epoxy resins, complexing agents, leather chemicals, paper chemicals, textile resins, fuel and gasoline additives, lubricants, bleaching additives, or detergents.

[0140] By removing NMEDA from the mixture containing EDA, NMEDA, and water obtained in the preparation of EDA, the method of the present invention makes it possible to obtain EDA according to specifications, with an EDA content of at least 99.5% by weight and an NMEDA content of 1000 ppm by weight or less, even when a larger amount of NMEDA is formed in the preparation of EDA.This may be the case, for example, when EDA is prepared from C1 units, such as formaldehyde and hydrogen cyanide, or when the catalyst shows partial activity as the operation time increases, and the reaction temperature must be increased to compensate for deactivation.Increasing the temperature generally leads to a decrease in selectivity, which is associated with the preparation of EDA and the increased formation of NMEDA as a by-product.Therefore, the method of the present invention also makes it possible to extend the use period of the catalyst in the preparation of EDA.

[0141] The method of the present invention also makes it possible to obtain high-purity EDA, which can be used as a raw material in many applications, with high yields and fewer side reactions.

[0142] Furthermore, the process of the present invention has the advantage of reducing separation and / or equipment complexity and energy consumption in rectification, allowing for reduced CAPEX and OPEX in EDA production. [Example]

[0143] The method of the present invention is illustrated by the following examples.

[0144] [Example 1] This example is based on calculations carried out based on thermodynamic modeling using the NRTL model for the description of vapor-liquid equilibria of water, EDA, NMEDA, and other higher boiling amines.

[0145] A 17,800 kg / h feed containing 25 wt.-% water, 33 wt.-% EDA, 1400 wt.-ppm NMEDA, and high-boiling amines such as DETA, AEEA, TETA, and TEPA was fed to the 34th theoretical plate of a column with a total of 47 theoretical plates. The column overhead pressure varied from 4.6 bar to 8.8 bar.

[0146] The concentration of NMEDA at the top of the water separation column as a function of column pressure is shown graphically in Figure 1. As the overhead pressure is decreased, the concentration of NMEDA in the treated water increases until nearly all of the NMEDA is separated from the other amines. Figure 1 also shows the reflux ratio required to maintain an EDA concentration of less than 100 ppm in the distillate removed at the top of the column. As pressure is decreased, separation becomes more difficult, as represented by an increase in the column reflux ratio.

[0147] The concentration of NMEDA in the product EDA as a function of the overhead pressure of the EDA-water separation is shown in Figure 2. As the pressure decreases, the concentration of NMEDA in the EDA decreases.

[0148] It can be seen that above 7.0 bar pressure, the NMEDA concentration rises to values ​​that make it difficult to obtain the EDA specifications required by the market. Below 5.0 bar pressure, it is difficult to separate EDA from the treated water. Surprisingly, separation is most affected in the narrow range of overhead pressures between 5.0 and 7.5 bar.

Claims

1. A process for producing ethylenediamine (EDA) from a mixture comprising water (HO), EDA, and N-methylethylenediamine (NMEDA) by feeding the mixture to a rectification column, wherein the rectification column is operated at an overhead pressure in the range of 5.0 to 7.5 bar.

2. 2. The process of claim 1, wherein the overhead pressure of the rectification column is in the range of 5.1 to 7.0 bar.

3. 3. The process according to claim 1, wherein the rectification column has 40 to 90 theoretical plates.

4. 4. The process according to any one of claims 1 to 3, wherein the reflux ratio of the column is in the range of 2:1 to 4:

1.

5. 5. The process according to any one of claims 1 to 4, wherein the rectification is a tray column.

6. 6. The method according to claim 1, wherein the mixture comprising water, EDA, and NMEDA is introduced into a spatial region between 60% and 80% of the theoretical plates.

7. 7. The method of claim 1, wherein the mixture comprising EDA, water, and NMEDA is obtained from a process for producing ethylenamine.

8. 8. The method according to claim 1, wherein the mixture comprising EDA, water, and NMEDA is obtained by reacting monoethanolamine with ammonia.

9. 9. The process according to claim 1, wherein a mixture comprising EDA and higher-boiling amines is obtained as a higher-boiling fraction at the bottom of a rectification column, the higher-boiling fraction being fed to a rectification column from which EDA and PIP are obtained as a lower-boiling fraction and higher-boiling amines are obtained as a higher-boiling fraction, and a mixture of EDA and PIP is fed to a rectification column from which EDA is obtained as a lower-boiling fraction and PIP is obtained as a higher-boiling fraction.

10. 10. The process of any one of claims 1 to 9, wherein the rectification column is operated at an overhead pressure at which EDA and water form a non-azeotropic mixture.

11. 11. The process according to any one of claims 1 to 10, wherein the mixture of water and NMEDA is obtained as the lower boiling fraction at the top of the rectification column.

12. 12. The method according to claim 11, wherein the mixture obtained at the top of the rectification column is fed to a wastewater treatment column and separated into a high-boiling fraction containing water and NMEDA and a low-boiling fraction containing water.

13. 13. The method of any one of claims 1 to 12, wherein ammonia and / or hydrogen are removed from a mixture comprising water (HO), ethylenediamine (EDA), and N-methylethylenediamine (NMEDA) before the mixture is fed to a rectification column.

14. 14. The method of any one of claims 1 to 13, comprising the steps of producing the EDA of any one of claims 1 to 13 and further converting the EDA into polyamides, electronic chemicals, crop protection agents, pesticides, epoxy resins, complexing agents, leather chemicals, paper chemicals, textile resins, fuel and gasoline additives, lubricants, bleaching additives, or detergents.

15. 15. The method according to claim 1, wherein the weight ratio of EDA to N-methylethylenediamine (NMEDA) in the mixture containing water (HO), ethylenediamine (EDA), and N-methylethylenediamine (NMEDA) fed to the rectification column is 1:0.0005 to 1:0.2.

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