Process for the preparation of diethylenetriamine and / or ethylene glycol

Abstract

A process for manufacturing diethylenetriamine (DETA) and / or monoethyleneglycol (MEG) from a mixture comprising diethylenetriamine (DETA) and monoethyleneglycol (MEG), the process comprising the steps of: (i) providing a feed stream comprising DETA and MEG; (ii) separating the feed stream provided in step (i) in a first distillation column DC1 into: a. a fraction A comprising DETA; and b. a fraction B comprising an azeotropic composition of DETA and MEG; (iii) separating fraction B obtained in step (ii) in a second distillation column DC2 into: c. a fraction C comprising MEG; and d. a fraction D comprising an azeotropic composition of DETA and MEG.

Description

[0001] This invention relates to a method for preparing diethylenetriamine (DETA) and / or monoethylene glycol (MEG) from a mixture comprising DETA and MEG.

[0002] DETA is a product that is typically produced as a coproduct in the industrial-scale preparation of ethylenediamine (EDA).

[0003] Two methods are typically used for the industrial-scale preparation of EDA.

[0004] First, EDA can be prepared by reacting 1,2-dichloroethane with ammonia and eliminating HCl (EDC method).

[0005] Another industrial-scale method for preparing EDA is the reaction of monoethanolamine (MEA) with ammonia in the presence of an amination catalyst (MEA method).

[0006] As an alternative to these two established methods, EDA can also be prepared by reacting monoethylene glycol (MEG) with ammonia. Preparing EDA from MEG offers several advantages. One advantage is the better availability of MEG compared to MEA.

[0007] MEA is produced on an industrial scale by reacting ethylene oxide (EO) with ammonia. Typically, a reaction mixture is formed containing MEA as well as higher ethanolamines such as diethanolamine (DEOA) and triethanolamine (TEOA). These byproducts must be separated from the MEA by a separate distillation step. Ethylene oxide is a highly flammable gas that can form explosive mixtures with air. The handling of EO is correspondingly complex. Therefore, the preparation of MEA requires technically sophisticated EO equipment with downstream post-processing stages.

[0008] In contrast, MEG can be produced based on petrochemical feedstocks or renewable feedstocks.

[0009] MEG is also prepared from EO via petrochemical means through the reaction of EO with water. In the same manner as the reaction of EO with ammonia, it is impossible to prevent the already formed MEG from reacting with EO to produce byproducts such as diethylene glycol and triethylene glycol. However, the selectivity for MEG is approximately 90%, and therefore significantly higher than the typical 70%-80% selectivity for MEA. The Shell omega process increases the selectivity for MEG to approximately 99%. In the omega process, EO is reacted with CO2 to produce ethylene carbonate, which is then selectively hydrolyzed to MEG in a second step.

[0010] MEG can also be produced from syngas, for example, by oxidative carbonylation of methanol to produce dimethyl oxalate and subsequently hydrogenation. Therefore, another possible petrochemical feedstock for MEG production is natural gas or coal.

[0011] Alternatively, MEG can also be prepared from renewable feedstocks such as corn or sugarcane by fermentation into ethanol, followed by dehydration into ethylene, and then reaction with oxygen to produce ethylene oxide.

[0012] Due to the many production variations, MEG availability is generally high, which usually has a positive impact on raw material costs.

[0013] The amination of MEG with ammonia typically leads to the formation of a variety of products. Potential reactions and side reactions during MEG amination include the formation of diethanolamine and triethanolamine, disproportionation, nitrile formation, carbonyl condensation, and fragmentation. Condensation and disproportionation in the case of diols can ultimately lead to the formation of oligomers (such as diethylenetriamine (DETA) and triethylenetetramine (TETA)) and polymers. Another important side reaction is cyclization. For example, diethanolamine or DETA can further react to produce piperazine (PIP). Higher temperatures promote dehydrogenation following cyclization to produce aromatic compounds. Therefore, the reaction of MEG with ammonia yields a broad product spectrum, with some products having greater commercial value than others. For example, there is greater commercial demand for EDA, DETA, and TETA than for PIP or aminoethylethanolamine (AEEA).

[0014] Existing technologies disclose that the reaction of MEG with ammonia to produce EDA can be carried out in the liquid phase or in the gas phase.

[0015] The amination of MEG in the gas phase is disclosed in two Chinese applications, CN 102 190 588 and CN 102 233 272.

[0016] For example, CN 102 190 588 describes a one-stage conversion of MEG and ammonia in the presence of a Cu catalyst. According to the specification, the reaction pressure is in the range of 3 to 30 bar. The reaction temperature is in the range of 150°C to 350°C.

[0017] Application CN 102 233 272 discloses the reaction of MEG with ammonia in the gas phase over a catalyst comprising Cu and Ni as major components and Zr, Zn, Al, Ti, Mn, and Ce as minor components. However, the composition of the resulting reaction mixture is not disclosed.

[0018] As an alternative to gas-phase conversion, the reaction of MEG with ammonia and hydrogen can also be carried out in the liquid phase. However, the reaction characteristics of catalysts in the gas and liquid phases often differ considerably, and therefore, conclusions drawn from the reaction characteristics of MEG in the gas phase are generally not applicable to the reaction characteristics of MEG in the liquid phase.

[0019] Many studies on the reaction of MEG with ammonia aim to find catalysts and reaction conditions that produce favorable product profiles.

[0020] US 4,111,840 discloses the reaction of MEG with ammonia and hydrogen at pressures of 500 to 5000 psig (approximately 34 to 340 bar) on a supported Ni / Re catalyst. It features a 60 m... 2 A supported silica / alumina catalyst with a surface area of ​​ / g produces a ratio with 150 m 2 Supported silica / alumina catalysts with a specific surface area of ​​ / g yield better results.

[0021] US 3,137,730 discloses the reaction of MEG with ammonia in the liquid phase over a Cu / Ni catalyst at temperatures of 200°C–300°C and pressures above 1000 psig (approximately 69 bar).

[0022] DE 1 172 268 discloses the conversion of ethylene glycol on a catalyst containing at least one of the metals Cu, Ag, Mn, Fe, Ni, and Co. In one example, MEG is reacted with ammonia at 180°C and 300 bar in the presence of hydrogen on a Co catalyst.

[0023] Chinese patent application CN 106607060 A discloses a catalyst for the amination of MEG in the liquid phase.

[0024] WO 2007 / 093514 discloses a two-stage method for preparing EDA, wherein in the first stage, amination is carried out on a hydroamication catalyst to a MEA conversion of no more than 40%, and in the second stage, a supported shaped Ru / Co catalyst host with a small geometry is used, and the second stage is carried out at a temperature at least 10°C higher than that of the first stage.

[0025] The product streams obtained by the methods described above are typically separated by distillation to produce individual products in pure form, especially the particularly desired products EDA and DETA.

[0026] WO 2007 / 093555 discloses that the post-distillation treatment of reaction products from MEG conversion is problematic because MEG and DETA form an azeotrope, which should be almost pressure-independent and therefore cannot be separated by pressure swing distillation. According to WO 2007 / 093555, the azeotropic composition is approximately 44% MEG and 56% DETA by weight, and has a boiling point of 154°C at 150 mbar, compared to 144°C for pure MEG and 142°C for pure DETA (in each case at the aforementioned pressure of 150 mbar). Therefore, WO 2007 / 093555 discloses a method for separating the product stream from MEG conversion by distillation, wherein one stage of the separation sequence is performed as an extractive distillation using triethylene glycol (TEG). WO 2007 / 093555 discloses a separation sequence comprising the following steps:

[0027] - The output from the MEG conversion is introduced into the first distillation unit KI, and the introduced output is separated into a top stream (containing ethylenediamine and piperazine components) and a bottom stream (containing components with boiling points greater than piperazine boiling points).

[0028] - The bottom stream from column KI is introduced into the second distillation column K-II, and the supplied bottom stream is separated into a top stream (containing monoethylene glycol, diethylenetriamine and monoethanolamine) and a bottom stream (containing components with higher boiling points than monoethylene glycol and diethylenetriamine).

[0029] - The top stream from column K-II is fed into extractive distillation column K-III, which is fed at the same separation stage or height with triethylene glycol as a selective solvent for diethylenetriamine. The diethylenetriamine-containing stream containing the selective triethylene glycol solvent is removed via the bottom, and the monoethylene glycol-containing stream, which is substantially free of diethylenetriamine, is removed from the top of extractive distillation column K-III.

[0030] - Preferably, the bottom stream containing a selective solvent carrying DETA from extractive distillation column K-III is fed to desorption column K-IV, where it is separated into a top stream containing DETA and a bottom stream containing TEG. Preferably, the bottom stream containing TEG from column K-IV is recycled back to extractive distillation column K-III.

[0031] WO 2019081283 relates to a method for purifying a mixture comprising MEG, MEA, EDA, and DETA, as well as a low-boiling substance having a boiling point not higher than PIP and a high-boiling substance having a boiling point not lower than AEEA, wherein the method comprises the following steps:

[0032] a) Separate a mixture containing MEG, MEA, EDA, and DETA, as well as low-boiling substances with a boiling point not higher than PIP and high-boiling substances with a boiling point not lower than AEEA, into:

[0033] (i) A mixture A comprising EDA and a low-boiling substance having a boiling point not higher than PIP; and

[0034] (ii) Mixture B containing MEA; and

[0035] (iii) A mixture C containing MEG, DETA and high-boiling substances having a boiling point not lower than AEEA;

[0036] b) Separate mixture C from stage a) into:

[0037] (i) a mixture D containing MEG; and

[0038] (ii) A mixture E containing MEG, DETA and a high-boiling substance having a boiling point not lower than AEEA;

[0039] c) Separate mixture E from stage b) into:

[0040] (i) a mixture F containing MEG and DETA; and

[0041] (ii) A mixture G containing high-boiling substances having a boiling point not lower than AEEA;

[0042] or

[0043] (i) a mixture F containing MEG and DETA; and

[0044] (ii) G1 containing AEEA; and

[0045] (iii) A mixture G2 containing high-boiling substances with boiling points higher than AEEA;

[0046] d) The mixture F from stage c) was separated into the following by extractive distillation with triethylene glycol:

[0047] (i) a mixture H containing MEG; and

[0048] (ii) A mixture containing DETA and TEG.

[0049] According to WO 2019081283, the difference between WO 2019081283 and WO 2007 / 093555 is that MEA is additionally removed in stage a), and the method of the invention additionally includes stage b), in which excess MEG is removed. The additional removal of MEA in stage a) allows MEA to be further reacted with ammonia in a separate reactor. It is claimed that the independent conversion of MEA reduces the formation of AEEA, which has a lower commercial value than EDA and DETA. It is further claimed that the additional removal of MEG in stage b) allows the MEG reactants to be introduced into stage b) prior to conversion in stage 1. This should result in additional purification of the MEG before it is introduced into stage 1. It is further claimed that an additional advantage of the additional separation from MEG is that the flow rate introduced into the extractive distillation (stage d) is less than that in the method described in WO 2007093555. The smaller flow rate of the product that must be separated in stage d) results in lower energy requirements and lower thermal stress on the product. Furthermore, due to the lower flow rate, the device size can reportedly be kept small, which could have a positive impact on the overall economic feasibility of the method.

[0050] Within the framework of this invention, it has been found that extractive distillation of mixtures containing MEG / DETA using TEG can result in significant discoloration of individual fractions (such as DETA and / or MEG). Colored products are difficult to market. Therefore, the object of this invention is to provide a method for manufacturing DETA and MEG that are transparent in color and otherwise possess high product quality that meets market demands.

[0051] The object of the present invention is achieved by a method for producing diethylenetriamine (DETA) and / or monoethylene glycol (MEG) from a mixture comprising diethylenetriamine (DETA) and monoethylene glycol (MEG), the method comprising the following steps:

[0052] (i) Provide a feed stream that includes DETA and MEG;

[0053] (ii) The feed stream provided in step (i) is separated in the first distillation column DC1 into:

[0054] a. Fraction A containing DETA; and

[0055] b. Fraction B of an azeotropic composition containing DETA and MEG;

[0056] (iii) The fraction B obtained in step (ii) is separated in the second distillation column DC2 into:

[0057] a. Fraction C containing MEG; and

[0058] b. Fraction D of an azeotropic composition containing DETA and MEG.

[0059] The following abbreviations will be used in the following text:

[0060] AEEA: Aminoethylethanolamine

[0061] AEP: Aminoethylpiperazine

[0062] DETA: Diethylenetriamine

[0063] EDA: Ethylenediamine

[0064] EDC: Dichloroethane

[0065] HEP: Hydroxyethylpiperazine

[0066] HPA: Polyamine

[0067] MEA: Monoethanolamine

[0068] MEG: Monoethylene Glycol

[0069] NMEDA: N-methylethylenediamine

[0070] PEHA: Pentylenehexamine

[0071] PIP: Piperazine

[0072] TEG: Triethylene Glycol

[0073] TEPA: Tetraethylenepentamine

[0074] TETA: Triethylenetetramine

[0075] Unless otherwise specified, pressure values ​​refer to absolute pressure values.

[0076] This invention can be performed as follows:

[0077] The method according to the invention includes a first step (i) of providing a feed stream comprising DETA and MEG.

[0078] The feed stream preferably contains 25 to 75% by weight, more preferably 30 to 60% by weight, and most preferably 35 to 55% by weight of MEG.

[0079] The feed stream preferably contains 25 to 75% by weight, more preferably 30 to 65% by weight, and most preferably 40 to 60% by weight of DETA.

[0080] More preferably, the weight ratio of MEG to DETA is in the range of 0.5:1 to 2:1, more preferably 0.6:1 to 1.5:1, and most preferably 0.7:1 to 1.3:1.

[0081] This feed stream can be obtained by mixing the appropriate amount of MEG / DETA.

[0082] In a preferred embodiment, the feed stream is obtained by separating the DETA / MEG azeotropic mixture from the DETA and MEG mixture at a pressure of 10 mbar to 1 bar, preferably 30 to 500 mbar, more preferably 50 to 200 mbar, and most preferably 60 to 120 mbar.

[0083] In one embodiment of the invention, the feed flow provided in step (i)

[0084] It contains very little or no AEPIP. In a preferred embodiment, the feed stream in step (ii) contains less than 3% by weight of AEPIP, preferably less than 1% by weight of AEPIP, and more preferably less than 0.5% by weight of AEPIP.

[0085] In another preferred embodiment, the feed stream provided in step (i) contains AEPIP at a concentration of 3 to 10% by weight, more preferably 4 to 8% by weight, and most preferably 5 to 7% by weight.

[0086] The feed stream provided in step (i) is preferably obtained by converting MEG and ammonia to produce a mixture of ethylamine and ethanolamine, and separating the components having boiling points lower than the MEG / DETA azeotrope at the corresponding pressure. Separate separation steps are known in the art and described, for example, in WO 2019 / 081283, PCT / EP2023 / 066376, PCT / EP2023 / 066433, WO 2021 / 115907, WO 2019 / 081285, WO2019 / 081286, WO2015 / 0135971, WO 2011 / 067226, WO 2019081283 and WO 2007 / 093555.

[0087] In a preferred embodiment, the feed stream provided in step (i) is prepared by a method including the following steps:

[0088] a. React MEG with ammonia to obtain a primary reaction mixture, and

[0089] b. Separate ammonia and / or hydrogen from the mixture obtained in step a, and

[0090] c. Separate water and / or NMEDA from the mixture obtained in step b.

[0091] d. Separate EDA and PIP together or sequentially from the mixture obtained in step c, and

[0092] e. Separate MEA from the mixture obtained in step d, and

[0093] f. Separate MEG from the mixture obtained in step e, and

[0094] g. Separate the azeotropic mixture containing DETA and MEG from the mixture obtained in step f.

[0095] Step a:

[0096] In a preferred embodiment, step a is performed as described in stage 1) of WO 2019 / 081283.

[0097] In another preferred embodiment, step a is performed as described in step (ia) of PCT / EP2023 / 066376.

[0098] The reaction of MEG with ammonia typically produces a reaction mixture containing unconverted MEG and a mixture of ethylamine and ethanolamine (such as EDA, DETA, TETA, TEPA, PIP, AEPIP, AEEA, HEPIP, diethanolamine (DEOA), and hydroxyethyl diethylenetriamine (HEDETA)).

[0099] Step b:

[0100] In a preferred embodiment, step b is performed as described in stage 2) of WO 2019 / 081283.

[0101] In another preferred embodiment, step b is performed as described in step (ib) of PCT / EP2023 / 066376.

[0102] In step b, ammonia and hydrogen are preferably separated from the mixture obtained in step a.

[0103] Step c: NMEDA / Water Separation

[0104] After separating ammonia and / or hydrogen, the mixture obtained in step b is preferably subjected to an additional separation step c, in which water and alkylation byproducts, particularly N-methylethylenediamine (NMEDA), are separated.

[0105] Typically, water and NMEDA are separated as head products by distillation in one or more columns.

[0106] In a preferred embodiment, step c is performed as described in step (ii) of PCT / EP2023 / 066376.

[0107] Step d: PIP / EDA separation

[0108] After separating water and / or NMEDA, the mixture obtained in step c is preferably subjected to another separation step, in which the lighter boiling components PIP and / or EDA are separated sequentially or together.

[0109] In a preferred embodiment, step d is performed as described in stage 6 of WO 2019 / 081283.

[0110] Step e: MEA separation

[0111] After separating EDA and PIP, the mixture obtained in step d is preferably subjected to another separation step, wherein MEA is separated as described below.

[0112] In separation step e, MEA is separated from the mixture obtained in step d.

[0113] In a preferred embodiment, the separation step e is preferably carried out in a distillation apparatus (such as a tray column, such as a bubble cap tray column, sieve tray column, dual-flow tray column, valve tray column, baffle tray column, or column with random or structured packing). Internals with low pressure drop are preferably used, such as structured packing, for example in the form of sheet-like metal packing, such as Mellapak 250 Y or Montz Pak (Type B1-250). Packing with even lower or higher specific surface areas may also be used, or fabric packing or packing with another geometry, such as Mellapak 252.Y, may be used. The advantages of using such internals are, for example, lower pressure drop and lower specific holdup compared to valve tray columns.

[0114] The interior can be arranged in one or more beds.

[0115] Preferably, the distillation column comprises structured packing, particularly Mellapak 250.

[0116] The design and layout of the tower used for separating MEA are determined by the production capacity. Typically, the tower has a diameter of 0.5 to 2.5 m, preferably 0.8 to 2 m, and most preferably 1 to 1.5 m, and a bed height of 5 to 20 m, preferably 7 to 15 m, and most preferably 8 to 12 m.

[0117] The theoretical number of plates in the column used for separating MEA is typically in the range of 10 to 80, preferably 20 to 60, and more preferably 30 to 50.

[0118] The energy required to separate MEA in the column is typically introduced through an evaporator at the bottom of the column. This evaporator 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, scraped film evaporators, or short-path evaporators, can be used.

[0119] Preferably, the mixture from step d is introduced into the space between 25% and 75% of the theoretical plates of the column. For example, the feed can be introduced into the middle section of the column. Preferably, the feed is introduced between 25% and 75% of the theoretical plates, and more preferably between 30% and 70% of the theoretical plates. For example, if the column has 25 theoretical plates, the feed is preferably introduced between plates 10 and 15.

[0120] Columns used for separating MEA typically have condensers that are usually operated at temperatures that cause a significant portion of fraction C to condense at the corresponding top pressure of the column.

[0121] Generally speaking, the operating temperature of the condenser is in the range of 10°C to 150°C, preferably 50°C to 140°C, and more preferably 80°C to 120°C.

[0122] Suitable condensers are condensers with cooling coils or spiral tubes, jacketed tube condensers, and shell-and-tube heat exchangers.

[0123] The pressure at the top of the column used for separation is preferably lower than the pressure at the top of the column used in step d.

[0124] Preferably, the top pressure of the column used for separating MEA is in the range of 100 to 10,000 mbar, preferably 300 to 800 mbar, and most preferably 400 to 600 mbar.

[0125] The column used for separating MEA can be operated at a column bottom temperature of 120°C to 250°C, more preferably 140°C to 220°C, and even more preferably 160°C to 200°C.

[0126] The energy required for evaporating MEA in the column is typically introduced through a reboiler at the bottom of the column. This reboiler is typically a natural circulation reboiler or a forced circulation reboiler. Alternatively, reboilers with short residence times, such as falling film reboilers, spiral reboilers, scraped film reboilers, or short-path reboilers, can be used.

[0127] The fraction containing MEA is preferably drawn off at the top of the column.

[0128] Preferably, the overhead fraction contains 1% by weight or less, more preferably 0.5% by weight or less, and most preferably 0.3% by weight or less of byproducts such as PIP and / or MEG.

[0129] Preferably, a portion of the overhead fraction is refluxed to the top of the column for MEA separation. The reflux ratio is preferably in the range of 1 to 10, more preferably 2 to 8, and most preferably 3 to 5.

[0130] Preferably, the bottom fraction containing MEG, DETA, and higher-boiling-point components formed during the conversion of MEG and ammonia is drawn from the column as the bottom stream. Preferably, the bottom fraction is introduced into step f.

[0131] Step f: MEG separation

[0132] Preferably, MEG is separated from the mixture obtained as the bottom product in step e in step f.

[0133] In separation step f, MEG is separated from the bottom product obtained in step e.

[0134] In a preferred embodiment, the separation step f is preferably carried out in a distillation apparatus (such as a tray column, like a bubble cap tray column, sieve tray column, dual-flow tray column, valve tray column, baffle tray column, or column with random or structured packing). Internals with low pressure drop are preferably used, such as structured packing, for example in the form of sheet-like metal packing, such as Mellapak 250 Y or Montz Pak (Type B1-250). Packing with even lower or higher specific surface areas may also be used, or fabric packing or packing with another geometry, such as Mellapak 252.Y, may be used. The advantages of using such internals are, for example, lower pressure drop and lower specific holdup compared to valve tray columns.

[0135] The interior can be arranged in one or more beds.

[0136] Preferably, the distillation column comprises structured packing, particularly Mellapak 250.

[0137] The design and layout of the tower used for MEG separation are determined by the production capacity. Typically, the tower has a diameter of 0.5 to 2.5 m, preferably 0.8 to 2 m, and most preferably 1 to 1.5 m, and a bed height of 5 to 20 m, preferably 7 to 15 m, and most preferably 8 to 12 m.

[0138] The theoretical number of plates in a column used for MEG separation is typically in the range of 5 to 50, preferably 7 to 40, and more preferably 10 to 25.

[0139] The energy required to separate MEG in the column is typically introduced through an evaporator at the bottom of the column. This evaporator 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, scraped film evaporators, or short-path evaporators, can be used.

[0140] Preferably, the mixture from step d is introduced into the space between 25% and 75% of the theoretical plates of the column for MEG separation. For example, the feed can be introduced into the middle section of the column. Preferably, the feed is introduced between 25% and 75% of the theoretical plates, and more preferably between 30% and 70% of the theoretical plates. For example, if the column has 25 theoretical plates, the feed is preferably introduced between plates 10 and 15.

[0141] Columns used for separating MEG typically have condensers that are usually operated at temperatures that cause a significant portion of the MEG to condense at the corresponding top pressure of the column.

[0142] Generally speaking, the operating temperature of the condenser is in the range of 10°C to 150°C, preferably 50°C to 140°C, and more preferably 80°C to 120°C.

[0143] Suitable condensers are condensers with cooling coils or spiral tubes, jacketed tube condensers, and shell-and-tube heat exchangers.

[0144] The pressure at the top of the column used for separation is preferably lower than the pressure at the top of the column used in step d.

[0145] Preferably, the top pressure of the column used for separating MEG is in the range of 50 to 800 mbar, preferably 100 to 600 mbar, and most preferably 200 to 400 mbar.

[0146] The column used for separating MEG can be operated at a column bottom temperature of 120°C to 250°C, more preferably 140°C to 220°C, and even more preferably 160°C to 200°C.

[0147] The energy required for MEG evaporation in the column is typically introduced through a reboiler at the bottom of the column. This reboiler is typically a natural circulation reboiler or a forced circulation reboiler. Alternatively, reboilers with short residence times, such as falling film reboilers, spiral reboilers, scraped film reboilers, or short-path reboilers, can be used.

[0148] The fraction containing MEG is preferably drawn off at the top of the column.

[0149] Preferably, the overhead fraction contains 1% by weight or less, more preferably 0.5% by weight or less, and most preferably 0.3% by weight or less, higher boiling point products such as MEA, AEEA, and HEPIP.

[0150] Preferably, a portion of the overhead fraction is refluxed to the top of the column for MEG separation. The reflux ratio is preferably in the range of 1 to 10, more preferably 2 to 8, and most preferably 3 to 5.

[0151] Preferably, the bottom fraction containing MEG, DETA, and higher boiling point components (such as AEPIP, AEEA, HEPIP, DEOA, TETA, and HEDETA) formed during the conversion of MEG with ammonia is drawn from the column as the bottom stream. Preferably, the bottom fraction is introduced into step g.

[0152] Step g: MEG / DETA separation

[0153] Preferably, in step g, the MEG / DETA fraction is separated from the mixture obtained as the bottom product in step f.

[0154] In a preferred embodiment, the separation step g is preferably carried out in a distillation apparatus (such as a tray column, like a bubble cap tray column, sieve tray column, dual-flow tray column, valve tray column, baffle tray column, or column with random or structured packing). Internals with low pressure drop are preferably used, such as structured packing, for example in the form of sheet-like metal packing, such as Mellapak 250 Y or Montz Pak (Type B1-250). Packing with even lower or higher specific surface areas may also be used, or fabric packing or packing with another geometry, such as Mellapak 252.Y, may be used. The advantages of using such internals are, for example, lower pressure drop and lower specific holdup compared to valve tray columns.

[0155] The interior can be arranged in one or more beds.

[0156] Preferably, the distillation column comprises structured packing, particularly Mellapak 250.

[0157] The design and layout of the column used for separating MEG / DETA fractions are determined by the production capacity. Typically, the column has a diameter of 0.5 to 2.5 m, preferably 0.8 to 2 m, and most preferably 1 to 1.5 m, and a bed height of 5 to 20 m, preferably 7 to 15 m, and most preferably 8 to 12 m.

[0158] The number of theoretical plates in columns used for separating MEG / DETA fractions is typically in the range of 10 to 80, preferably 20 to 60, and more preferably 30 to 50.

[0159] The energy required to separate the MEG / DETA fraction in the column is typically introduced through an evaporator at the bottom of the column. This evaporator 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, scraped film evaporators, or short-path evaporators, can be used.

[0160] Preferably, the mixture from step d is introduced into the space between 25% and 75% of the theoretical plates of the column. For example, the feed can be introduced into the middle section of the column. Preferably, the feed is introduced between 25% and 75% of the theoretical plates, and more preferably between 30% and 70% of the theoretical plates. For example, if the column has 25 theoretical plates, the feed is preferably introduced between plates 10 and 15.

[0161] Columns used to separate MEG / DETA fractions typically have condensers that are usually operated at temperatures that cause a significant portion of the MEG / DETA fraction to condense at the corresponding top pressure of the column.

[0162] Generally speaking, the operating temperature of the condenser is in the range of 10°C to 150°C, preferably 50°C to 140°C, and more preferably 80°C to 120°C.

[0163] Suitable condensers are condensers with cooling coils or spiral tubes, jacketed tube condensers, and shell-and-tube heat exchangers.

[0164] The pressure at the top of the column used for separation is preferably lower than the pressure at the top of the column used in step d.

[0165] Preferably, the top pressure of the column used to separate MEG / DETA fractions is in the range of 10 to 200 mbar, preferably 25 to 150 mbar, and most preferably 50 to 100 mbar.

[0166] The column used for separating MEG / DETA fractions can be operated at a bottom temperature of 120°C to 250°C, more preferably 140°C to 220°C, and even more preferably 160°C to 200°C.

[0167] The energy required for evaporating the MEG / DETA fraction in the column is typically introduced through a reboiler at the bottom of the column. This reboiler is typically a natural circulation reboiler or a forced circulation reboiler. Alternatively, reboilers with short residence times, such as falling film reboilers, spiral reboilers, scraped film reboilers, or short-path reboilers, can be used.

[0168] Fractions containing MEG and DETA are preferably drawn off at the top of the column.

[0169] Preferably, a portion of the overhead fraction is refluxed to the top of the column for separating the MEG / DETA fraction. The reflux ratio is preferably in the range of 1 to 10, more preferably 2 to 8, and most preferably 3 to 5.

[0170] Preferably, the bottom fraction containing higher boiling point components (such as AEEA, HEPIP, TETA, and HEDETA) formed during the conversion of MEG and ammonia is drawn from the column as the bottom stream.

[0171] Preferably, the azeotrope of MEG and DETA separated as overhead products in step g constitutes the feed stream provided in step (i).

[0172] In a preferred embodiment of the invention, the feed stream obtained in step g contains very little or no AEPIP. In this preferred embodiment, the feed stream in step (ii) preferably contains less than 3% by weight of AEPIP, more preferably less than 1% by weight of AEPIP, and even more preferably less than 0.5% by weight of AEPIP.

[0173] In another preferred embodiment, the feed stream obtained in step g contains AEPIP at a concentration of 3 to 10% by weight, more preferably 4 to 8% by weight, and most preferably 5 to 7% by weight.

[0174] The amount of AEPIP can be changed by altering the ratio of NH3 to MEG and by changing the degree of MEG conversion in step a.

[0175] According to the present invention, the feed stream containing DETA and MEG provided in step (i) is subjected to the following steps:

[0176] (ii) The feed stream provided in step (i) is separated in the first distillation column DC1 into:

[0177] a. Fraction A containing DETA; and

[0178] b. Fraction B of an azeotropic composition containing DETA and MEG.

[0179] In a preferred embodiment, the feed stream provided in step (i) is separated in the first distillation column DC1.

[0180] In separation step (ii), the distillation column DC1 is preferably a distillation apparatus (such as a tray column, like a bubble cap tray column, sieve tray column, dual-flow tray column, valve tray column, baffle tray column, or a column with random or structured packing). Internals with low pressure drop are preferred, such as structured packing, for example in the form of sheet-like metal packing, such as Mellapak 250 Y or Montz Pak (type B1-250). Packing with even lower or higher specific surface areas may also be used, or fabric packing or packing with another geometry, such as Mellapak 252.Y, may be used. The advantages of using such internals are, for example, lower pressure drop and lower specific holdup compared to valve tray columns.

[0181] The interior can be arranged in one or more beds.

[0182] Preferably, the distillation column comprises structured packing, particularly Mellapak 250.

[0183] The design and layout of tower DC1 are determined by production capacity. Typically, tower DC1 has a diameter of 0.5 to 2.5 m, preferably 0.8 to 2 m and most preferably 1 to 1.5 m, and a bed height of 5 to 20 m, preferably 7 to 15 m and most preferably 8 to 12 m.

[0184] The theoretical number of plates in column DC1 is typically in the range of 5 to 50, preferably 10 to 40, and more preferably 20 to 30.

[0185] The energy required to separate the feed supplied in step (i) in column DC1 is typically introduced via an evaporator at the bottom of the column. This evaporator is typically a natural circulation evaporator or a forced circulation evaporator. Alternatively, an evaporator with a short residence time, such as a falling film evaporator, a spiral tube evaporator, a scraped film evaporator, or a short-path evaporator, can be used.

[0186] Preferably, the feed containing MEG and DETA provided in step (i) is introduced into the space between 25% and 75% of the theoretical plates of column DC1. For example, the feed can be introduced into the middle section of the column. Preferably, the feed is introduced between 25% and 75% of the theoretical plates, and more preferably between 30% and 70% of the theoretical plates. For example, if the column has 25 theoretical plates, the feed is preferably introduced between plates 10 and 15.

[0187] Column DC1 typically has a condenser that is usually operated at a temperature that causes a significant portion of fraction A to condense at the corresponding top pressure of the column.

[0188] Generally speaking, the operating temperature of the condenser is in the range of 10°C to 150°C, preferably 50°C to 140°C, and more preferably 80°C to 120°C.

[0189] Suitable condensers are condensers with cooling coils or spiral tubes, jacketed tube condensers, and shell-and-tube heat exchangers.

[0190] The pressure at the top of tower DC1 is preferably less than the pressure in step f.

[0191] Preferably, the pressure at the top of column DC1 is 1 bar or less, more preferably 500 mbar or less, even more preferably 200 mbar or less, and most preferably 100 mbar or less. The preferred range of the pressure at the top of column DC1 is 10 to 100 mbar lower than the pressure in step f, more preferably 20 to 90 mbar lower, and most preferably 40 to 80 mbar lower.

[0192] Therefore, the pressure at the top of column DC1 is preferably in the range of 1 to 50 mbar, more preferably 5 to 40 mbar, and most preferably 10 to 30 mbar. Within this preferred pressure range, the pressure at the top of the column can maintain a reasonable pressure drop along the internal components of the column and result in adequate separation.

[0193] The column DC1 can be operated at a column bottom temperature of 50°C to 200°C, more preferably 70°C to 180°C, and even more preferably 100°C to 150°C.

[0194] The energy required for the feed supplied in step (i) for evaporation in column DC1 is typically introduced through a reboiler at the bottom of the column. This reboiler is typically a natural circulation reboiler or a forced circulation reboiler. Alternatively, a reboiler with a short residence time, such as a falling film reboiler, a spiral reboiler, a scraped film reboiler, or a short-path reboiler, can be used.

[0195] Fraction A containing DETA is preferably drawn off at the top of column DC1.

[0196] Preferably, fraction A contains 1% or less AEPIP, more preferably 0.7% or less, and most preferably 0.5% or less AEPIP.

[0197] Preferably, fraction B, which contains a mixture of DETA and MEG, is drawn from column DC1 as the bottom stream. The composition of fraction B typically corresponds to the composition of the DETA / MEG azeotrope at the corresponding pressure in column DC1.

[0198] If the feed provided in step (i) also contains AEPIP, then fraction B will preferably contain a significant portion of AEPIP in addition to the small amount of AEPIP separated from the top fraction as stated above.

[0199] According to the present invention, after step (ii) is:

[0200] (iii) The fraction B obtained in step (ii) is separated in the second distillation column DC2 into:

[0201] a. Fraction C containing MEG; and

[0202] b. Fraction D of an azeotropic composition containing DETA and MEG.

[0203] If fraction B contains very little or no AEPIP, for example, less than 3% by weight of AEPIP, preferably less than 1% by weight of AEPIP, and more preferably less than 0.5% by weight of AEPIP, then the following embodiment of step (iii) is preferred (where variations of step (iii) in which fraction B contains very little or no AEPIP will be referred to as step (iii)-a):

[0204] In Examples (iii)-a), fraction B is separated in the second distillation column DC2.

[0205] In separation step (iii)-a), the distillation column DC2 is preferably a distillation apparatus (such as a tray column, like a bubble cap tray column, sieve tray column, dual-flow tray column, valve tray column, baffle tray column, or a column with random or structured packing). Internals with low pressure drop are preferred, such as structured packing, for example in the form of sheet-like metal packing, such as Mellapak 250 Y or Montz Pak (type B1-250). Packing with even lower or higher specific surface areas may also be used, or fabric packing or packing with another geometry, such as Mellapak 252.Y, may be used. The advantages of using such internals are, for example, lower pressure drop and lower specific holdup compared to valve tray columns.

[0206] The interior can be arranged in one or more beds.

[0207] Preferably, the distillation column comprises structured packing, particularly Mellapak 250.

[0208] The design and layout of tower DC2 are determined by production capacity. Typically, tower DC1 has a diameter of 0.5 to 2.5 m, preferably 0.8 to 2 m and most preferably 1 to 1.5 m, and a bed height of 5 to 20 m, preferably 7 to 15 m and most preferably 8 to 12 m.

[0209] The theoretical number of plates in column DC2 is typically in the range of 5 to 80, preferably 10 to 50, and more preferably 20 to 40.

[0210] The energy required to separate fraction B in column DC2 is typically introduced through an evaporator at the bottom of the column. This evaporator 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, scraped film evaporators, or short-path evaporators, can be used.

[0211] In a preferred embodiment, the reboiler is a forced recirculation reboiler. This reboiler has the advantage that, unlike falling film evaporators, the temperature difference does not cause violent boiling that would rupture the falling film.

[0212] Preferably, fraction B is introduced into the space between 25% and 75% of the theoretical trays of column DC2. For example, the feed can be introduced into the middle section of the column. Preferably, the feed is introduced between 25% and 75% of the theoretical trays, and more preferably between 30% and 70% of the theoretical trays. For example, if the column has 25 theoretical trays, the feed is preferably introduced between trays 10 and 15.

[0213] Column DC2 typically has a condenser that is usually operated at a temperature that causes a significant portion of fraction C to condense at the corresponding top pressure of the column.

[0214] Generally speaking, the operating temperature of the condenser is in the range of 10°C to 150°C, preferably 50°C to 140°C, and more preferably 80°C to 120°C.

[0215] Suitable condensers are condensers with cooling coils or spiral tubes, jacketed tube condensers, and shell-and-tube heat exchangers.

[0216] The pressure at the top of tower DC2 is preferably higher than that at the top of tower DC1.

[0217] Preferably, the top pressure of column DC2 is in the range of 0.5 to 5 bar, preferably 1 to 3 bar, and most preferably 1.2 to 2 bar. Within the preferred pressure range, the products in the column (especially at the bottom) remain thermally stable, and these products have a low tendency to discolor. Also within this pressure range, the temperature is within a certain range, allowing thermal energy to be provided via pressurized steam that is typically readily available at chemical production sites.

[0218] Tower DC2 can be operated at a bottom temperature of 150°C to 300°C, more preferably 180°C to 250°C, and even more preferably 200°C to 250°C.

[0219] The energy required to evaporate fraction B in column DC1 is typically introduced through a reboiler at the bottom of the column. This reboiler is typically a natural circulation reboiler or a forced circulation reboiler. Alternatively, a reboiler with a short residence time, such as a falling film reboiler, a spiral reboiler, a scraped film reboiler, or a short-path reboiler, can be used.

[0220] The fraction C containing MEG is preferably drawn off at the top of column DC2.

[0221] Preferably, fraction C contains 1% by weight or less, more preferably 0.7% by weight or less, and most preferably 0.5% by weight or less of DETA and / or AEPIP.

[0222] Preferably, a portion of fraction C is refluxed to the top of column DC2. The reflux ratio is preferably in the range of 1 to 10, more preferably 2 to 8, and most preferably 3 to 5.

[0223] Preferably, fraction D, containing DETA and MEG, is drawn from column DC2 as a liquid bottoms stream. The composition of fraction D typically corresponds to the composition of the DETA / MEG azeotrope at the corresponding pressure in column DC2. Preferably, fraction D is recycled to the feed inlet point of column DC1.

[0224] In a preferred embodiment of steps (iii)-a), column DC2 does not include a condenser, and the vapor obtained at the top of column DC2 is used to heat the reboiler of column DC1, where the vapor is partially or completely condensed. A portion of the condensate stream, in the amount stated above, is recycled back to column DC2 as reflux. Preferably, a portion of the condensate stream condensed in the reboiler of column DC1 is recycled to the stage where MEG is converted with ammonia.

[0225] If fraction B contains AEPIP, for example, 3% by weight or more, preferably 4% by weight or more, and more preferably 5% by weight or more, then the following embodiment of step (iii) is preferred (where a variant of step (iii) in which fraction B contains AEPIP will be referred to as step (iii)-b):

[0226] In step (iii)-b, fraction B is separated in the second distillation column DC2.

[0227] In separation step (iii)-a), the distillation column DC2 is preferably a distillation apparatus (such as a tray column, like a bubble cap tray column, sieve tray column, dual-flow tray column, valve tray column, baffle tray column, or a column with random or structured packing). Internals with low pressure drop are preferred, such as structured packing, for example in the form of sheet-like metal packing, such as Mellapak 250 Y or Montz Pak (type B1-250). Packing with even lower or higher specific surface areas may also be used, or fabric packing or packing with another geometry, such as Mellapak 252.Y, may be used. The advantages of using such internals are, for example, lower pressure drop and lower specific holdup compared to valve tray columns.

[0228] The interior can be arranged in one or more beds.

[0229] Preferably, the distillation column comprises structured packing, particularly Mellapak 250.

[0230] The design and layout of tower DC2 are determined by production capacity. Typically, tower DC1 has a diameter of 0.5 to 2.5 m, preferably 0.8 to 2 m and most preferably 1 to 1.5 m, and a bed height of 5 to 20 m, preferably 7 to 15 m and most preferably 8 to 12 m.

[0231] The theoretical number of plates in column DC2 is typically in the range of 5 to 80, preferably 10 to 50, and more preferably 20 to 40.

[0232] The energy required to separate fraction B in column DC2 is typically introduced through an evaporator at the bottom of the column. This evaporator 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, scraped film evaporators, or short-path evaporators, can be used.

[0233] Preferably, fraction B is introduced into the space between 25% and 75% of the theoretical trays of column DC2. For example, the feed can be introduced into the middle section of the column. Preferably, the feed is introduced between 25% and 75% of the theoretical trays, and more preferably between 30% and 70% of the theoretical trays. For example, if the column has 25 theoretical trays, the feed is preferably introduced between trays 10 and 15.

[0234] Column DC2 typically has a condenser that is usually operated at a temperature that causes a significant portion of fraction C to condense at the corresponding top pressure of the column.

[0235] Generally speaking, the operating temperature of the condenser is in the range of 10°C to 150°C, preferably 50°C to 140°C, and more preferably 80°C to 120°C.

[0236] Suitable condensers are condensers with cooling coils or spiral tubes, jacketed tube condensers, and shell-and-tube heat exchangers.

[0237] The pressure at the top of tower DC2 is preferably higher than that at the top of tower DC1.

[0238] Preferably, the top pressure of column DC2 is in the range of 1 to 5 bar, preferably 1.2 to 3 bar, and most preferably 1.3 to 2 bar. Within the preferred pressure range, the products in the column (especially at the bottom) remain thermally stable, and these products have a low tendency to discolor. Also within this pressure range, the temperature is within a certain range, allowing thermal energy to be provided via pressurized steam that is typically readily available at chemical production sites.

[0239] Tower DC2 can be operated at a bottom temperature of 150°C to 300°C, more preferably 180°C to 250°C, and even more preferably 200°C to 250°C.

[0240] The fraction C containing MEG is preferably drawn off at the top of column DC2.

[0241] Preferably, fraction C contains 1% by weight or less, more preferably 0.7% by weight or less, and most preferably 0.5% by weight or less of DETA and / or AEPIP.

[0242] In a preferred embodiment, the vapor containing fraction C exiting the top of column DC2 does not condense at the top of column DC2, and the uncondensed vapor containing fraction C is used to heat the reboiler of column DC1, where fraction C is at least partially condensed to form at least partially condensed fraction C. This preferred embodiment is particularly energy-efficient because a portion of the energy of the hot vapor exiting column DC2 can be used to heat the bottom of column DC1. Preferably, a portion of the condensed fraction C is recycled as reflux to the head of column DC2, with the reflux ratio preferably in the range of 1 to 10, preferably 2 to 8, and most preferably 3 to 5. Preferably, another portion of the condensed fraction C is recycled to stage 1, i.e., MEG conversion with ammonia.

[0243] Preferably, a portion of fraction C is refluxed to the top of column DC2. The reflux ratio is preferably in the range of 1 to 10, more preferably 2 to 8, and most preferably 3 to 5.

[0244] Preferably, fraction D, containing DETA and MEG, is drawn from column DC2 as a side stream. The composition of fraction D typically corresponds to the composition of the DETA / MEG azeotrope at the corresponding pressure in column DC2. Preferably, fraction D is fed or recycled to the feed inlet point of column DC1.

[0245] In a preferred embodiment, fraction D is used to heat fraction B in a cross-flow heat exchanger before fraction B is fed into column DC2. This embodiment is particularly energy-efficient.

[0246] Preferably, fraction E containing DETA is removed from the bottom of column DC2. Fraction E preferably contains AEPIP. Typically, fraction E contains up to 60% by weight, preferably up to 55% by weight, and more preferably up to 50% by weight of AEPIP.

[0247] Because of the separate side-stream extraction, it is preferable that the distillation column DC2 includes two rectification sections and one stripping section, wherein the first rectification section RS1 is located between the feed of fraction B and the extraction of fraction D, and the second rectification section RS2 is located between the extraction of fraction D and the extraction of fraction C, and the stripping section is located between the feed of fraction B and the extraction of fraction E.

[0248] The method of the present invention for separating MEG / DETA mixtures (preferably obtainable from the conversion of MEG) provides a method that enables the desired process products of MEG and / or DETA to be obtained in high yield and purity, particularly products with low discoloration. Furthermore, the energy requirements for separating DETA / MEG azeotropes can be more advantageous compared to extractive distillation with TEG described in the prior art.

[0249] DETA produced by the method of this invention can be converted into chemicals, products or materials in one or more steps, such as chelating agents, epoxy curing agents, epoxy resins, polyurethane catalysts, polyurethanes, fuel additives, corrosion inhibitors, surfactants, lubricant additives, pharmaceuticals, agrochemicals, ion exchange resins and adhesives.

[0250] MEG produced by the method of the present invention can be converted into chemicals, products or materials, such as polymers, such as polyethylene terephthalate (PET) or polyethylene glycol, glycol ethers, resins, solvents, antifreeze, coolants, heat transfer fluids, plasticizers, hydraulic fluids and wetting agents in one or more steps.

[0251] The method of the present invention will be illustrated by the following examples.

[0252] Comparison Example 1:

[0253] (Concentration is mass fraction, pressure is absolute value)

[0254] A mixture containing 20.11% MEG, 16.48% DETA, 2.99% AEPIP, and 59.94% TEG was subjected to fractional distillation. This starting mixture was obtained by distilling a fraction containing MEG, DETA, and AEPIP obtained from the conversion of MEG with NH3 after separating the lower-boiling components with boiling points less than or equal to MEG. The recovered colorless MEG, DETA, and AEPIP fraction was mixed with the original colorless TEG.

[0255] A column containing 1000 mm Sulzer BX packing (approximately 30 theoretical plates) was used to fractionate a mixture of MEG, DETA, AEPIP, and TEG. A head pressure of 30 mbar and a reflux rate of 60:3 (= 20) were set, and 11 fractions were collected from the top of the column. Fractions 1 through 7 consisted primarily of MEG and / or DETA, while fractions 8 through 11 consisted primarily of TEG.

[0256] The bottom temperature of the fractionation column started at 132.5°C and rose to 177.7°C after the 11th fraction was taken out. The top temperature started at 101.8°C and rose to 173.9°C at the end.

[0257] The first fraction produces a light rose color, the second fraction is almost colorless, and fraction 3 is completely colorless. Fraction 4 is light rose, fractions 5 and 6 are colorless, and fraction 7 is light yellow. All these fractions consist primarily of MEG and / or DETA. Subsequent fractions (mainly composed of TEG) are deep yellow, and the residue remaining in the still is a very dark brown.

[0258] This example shows that although the original mixture of DETA, AEPIP, MEG, and TEG is colorless, significant discoloration occurs due to unknown products with partial volatility and contaminated recycled MEG and DETA.

[0259] Comparison Example 2

[0260] (Concentration is mass fraction, pressure is absolute value)

[0261] A colorless synthetic mixture of 36% MEG and 64% DETA was heat-treated at 213°C under atmospheric pressure and absolute reflux for 19 hours. No significant discoloration was observed in the heat-treated mixture. The mixture was then distilled into three fractions until 60% of the mixture had evaporated. All three distillate fractions were colorless.

[0262] This experiment demonstrates that no discoloration occurs when a MEG / DETA mixture without TEG is heat-treated.

[0263] Example 3

[0264] (Concentration is mass fraction, pressure is absolute value)

[0265] A mixture containing approximately 41.6% MEG, 5.3% DETA, and 5.7% AEPIP was fed into the first column, DC1, which operated at a head pressure of 15 mbar and consisted of a stripping section with 15 theoretical plates and a rectification section with 11 theoretical plates (using Sulzer BX packing). The feed rate was set at 635 kg / h, and the reflux rate at 4000 kg / h. The head temperature was 94°C, and the bottom temperature was 121°C. 316 kg / h of headstock containing DETA was withdrawn, which contained 5000 ppm AEPIP and no detectable MEG.

[0266] At the top of the stripping section, 1926 kg / h of recycle stream REC from tower DC2 is fed into tower DC1. 2245 kg / h is extracted as bottom product of tower DC1 and fed to the top of the stripping section of tower DC2.

[0267] Column DC2 comprises a stripping section with 17 theoretical plates, an intermediate section with 3 theoretical plates, and a rectification section with 13 theoretical plates (using Sulzer Mellapak packing). Column DC2 operates at a pressure of 1.5 bar and a reflux rate of 2.4 t / h. The top temperature is 211°C, and the bottom temperature is 233°C. As described above, the REC stream is drawn as a liquid sidestream from between the intermediate and rectification sections and recycled back to column DC1.

[0268] The headstock of column DC2 is drawn at a rate of 250 kg / h, consisting of MEG with 983 ppm DETA and 17 ppm AEPIP. The bottomstock of column DC2 is drawn at a rate of 68 kg / h, consisting of a mixture of 19.5% MEG, 30.5% DETA, and 50% AEPIP.

[0269] The headstock of tower DC1 (DETA) and the headstock of tower DC2 (MEG) are both colorless.

Claims

1. A method for producing diethylenetriamine (DETA) and / or monoethylene glycol (MEG) from a mixture comprising diethylenetriamine (DETA) and monoethylene glycol (MEG), the method comprising the steps of: (i) Provide a feed stream that includes DETA and MEG; (ii) The feed stream provided in step (i) is separated in the first distillation column DC1 into: a. Fraction A containing DETA; and b. Fraction B of an azeotropic composition containing DETA and MEG; (iii) The fraction B obtained in step (ii) is separated in the second distillation column DC2 into: a. Fraction C containing MEG; and b. Fraction D of an azeotropic composition containing DETA and MEG.

2. The method according to claim 1, wherein, Distillation column DC2 includes one or more stripping sections and one or more rectification sections.

3. The method according to at least one of claims 1 or 2, wherein, Distillation column DC1 operates at a lower pressure than distillation column DC2.

4. The method according to claim 3, wherein, Distillation column DC1 operates at a head pressure ranging from 1 to 50 mbar, and distillation column DC2 operates at a head pressure ranging from 0.5 bar to 5 bar.

5. The method according to at least one of claims 1 to 4, wherein, Fraction A is separated at the top of column DC1, and fraction B is separated at the bottom of column DC1.

6. The method according to at least one of claims 1 to 5, wherein, Fraction C is separated at the top of column DC2, and fraction D is separated at the bottom of column DC2.

7. The method according to at least one of claims 1 to 7, wherein, Mixture D is fed into tower DC1.

8. The method according to at least one of claims 1 to 7, wherein, The feed provided in step (i) and the fraction B obtained in step (ii) additionally contain aminoethylpiperazine (AEPIP), and wherein the fraction B obtained in step (ii) is separated in distillation column DC2 into an additional fraction E containing AEPIP.

9. The method according to claim 8, wherein, Fraction C is separated at the head of column DC2, fraction E is separated at the bottom of column DC2, and fraction D is separated as a side-take fraction between the feed of fraction B and the take-out of fraction C.

10. The method according to claim 9, wherein, Distillation column DC2 includes two rectification sections and one stripping section, wherein the first rectification section RS1 is located between the feed of fraction B and the output of fraction D, the second rectification section RS2 is located between the output of fraction D and the output of fraction C, and the stripping section is located between the feed of fraction B and the output of fraction E.

11. The method according to claim 10, wherein, The distillate D was taken from the side and was in liquid form.

12. The method according to at least one of claims 9 to 11, wherein, Fraction D is fed into column DC1.

13. The method according to at least one of claims 9 to 12, wherein, The steam exiting the head of tower DC2 is used to heat the reboiler of tower DC1.

14. The method according to at least one of claims 9 to 13, wherein, Fraction D is used to heat fraction B before feeding fraction B into distillation column DC2.

15. The method according to at least one of claims 1 to 14, wherein, Fraction C is recycled to the reactor, where MEG is converted into ethylenediamine (EDA).

16. The method according to at least one of claims 1 to 15, wherein, Step (i) includes the following steps: a. React MEG with ammonia to obtain a primary reaction mixture, and b. Separate ammonia and / or hydrogen from the mixture obtained in step a, and c. Separate water and / or NMEDA from the mixture obtained in step b. d. Separate EDA and PIP together or sequentially from the mixture obtained in step c, and e. Separate MEOA from the mixture obtained in step d, and f. Separate MEG from the mixture obtained in step e, and g. Separate the azeotropic mixture containing DETA and MEG from the mixture obtained in step f.

17. The method according to at least one of claims 1 to 16, comprising: Additional steps in one or more steps to convert DETA or MEG into chemicals, products, or materials.