Process for preparing diethylenetriamine and / or ethylene glycol

Abstract

A method for the manufacture of diethylenetriamine (DETA) and / or monoethylene glycol (MEG) from a mixture comprising diethylenetriamine (DETA) and monoethyleneglycol (MEG), 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] Process for preparing diethylenetriamine and / or ethylene glycol

[0002] Description

[0003] The present invention relates to a process for preparing diethylenetriamine (DETA) and / or monoethylene glycol (MEG) proceeding from mixtures comprising DETA and MEG.

[0004] DETA is a product which is usually produced as a co-product in the industrial scale preparation of ethylenediamine (EDA).

[0005] Two processes are usually employed for industrial scale preparation of EDA.

[0006] Firstly, EDA can be prepared by reaction of 1 ,2-dichloroethane with ammonia with elimination of HCI (EDC process).

[0007] A further industrial scale process for preparation of EDA is the reaction of monoethanolamine (MEA) with ammonia in the presence of amination catalysts (MEA process).

[0008] As an alternative to these two established processes, EDA can also be prepared by reaction of monoethylene glycol (MEG) with ammonia. The preparation of EDA ex MEG would have various advantages. One advantage is the good availability of MEG compared to MEA.

[0009] MEA is prepared on the industrial scale by reaction of ethylene oxide (EO) and ammonia. What is generally formed is a reaction mixture comprising MEA, as well higher ethanolamines such as diethanolamine (DEOA) and triethanolamine (TEOA). These by-products have to be separated from 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. The preparation of MEA thus requires a technically complex EO plant with downstream workup sections.

[0010] By contrast, MEG can be produced either on the basis of petrochemical raw materials or on the basis of renewable raw materials.

[0011] By petrochemical means, MEG is likewise prepared from EO by reaction with water. In the same way as in the reaction of EO with ammonia, it is not possible in the reaction of EO with water to prevent MEG that has already formed from reacting with EO to give by-products such as di- and triethylene glycol. The selectivity for MEG is about 90% and is thus, however, distinctly higher than the selectivity for MEA, which is generally 70-80%. The Shell omega process increases the selectivity for MEG - to about 99%. In the omega process, EO is reacted with CO2 to give ethylene carbonate which, in the second step, is selectively hydrolyzed to MEG.

[0012] MEG can also be prepared from synthesis gas, for example by oxidative carbonylation of methanol to give dimethyl oxalate and subsequent hydrogenation thereof. Thus, a further possible petrochemical raw material for the preparation of MEG is also natural gas or coal.

[0013] Alternatively, MEG can also be prepared from renewable raw materials, such as corn or sugarcane, by fermentation to ethanol, followed by dehydration to ethene and subsequent reaction with oxygen to give ethylene oxide.

[0014] Owing to the many production variants, the availability of MEG is generally high, which generally has a positive effect on raw material costs. The amination of MEG with ammonia usually results in the formation of multiple products. Reactions and side reactions that can occur in the amination of MEG are the formation of di- and triethanolamine, disproportionation, nitrile formation, carbonyl condensation and fragmentation reactions. Condensation and disproportionation in the case of dihydric alcohols can ultimately also lead to the formation of oligomers, such as diethylenetriamine (DETA), triethylenetetramine (TETA) and polymers. An important further side reaction is cyclization. For instance, diethanolamine or DETA can react further to give piperazine (PIP). Higher temperatures promote dehydrogenation, which follows on from the cyclization, to give aromatics. Thus, the reaction of MEG with ammonia gives a broad product spectrum, some products in the product spectrum being of greater commercial interest than others. For instance, the commercial demand for EDA, DETA and TETA is higher than that for PIP or aminoethyl ethanolamine (AEEA). The prior art discloses that the reaction of MEG with ammonia to give EDA can be affected either in the liquid phase or in the gas phase.

[0015] The amination of MEG in the gas phase is disclosed in the two Chinese applications CN 102 190 588 and CN 102 233272.

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

[0017] Application CN 102 233 272 discloses the reaction of MEG with ammonia in the gas phase over catalysts that include Cu and Ni as main constituents and Zr, Zn, Al, Ti, Mn and Ce as secondary component. However, the composition of the reaction mixtures obtained was not disclosed.

[0018] As an alternative to conversion in the gas phase, the reaction of MEG with ammonia and hydrogen can also be carried out in the liquid phase. However, there is generally a considerable difference in the reaction characteristics of catalysts in the gas phase and liquid phase, and so it is generally impermissible to apply conclusions from the reaction characteristics of MEG in the gas phase to the reaction characteristics of MEG in the liquid phase.

[0019] The object of many studies in the reaction of MEG with ammonia was to find catalysts and reaction conditions that lead to an advantageous product spectrum.

[0020] US 4,111,840 discloses the reaction of MEG with ammonia and hydrogen at pressures of 500 to 5000 psig (about 34 to 340 bar) over supported Ni / Re catalysts. Supported silica / alumina catalysts having a surface area of 60 m2 / g led to better results here than supported silica / alumina catalysts having a specific surface area of 150 m2 / g.

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

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

[0023] Chinese application CN 106607060 A discloses catalysts for amination of MEG in the liquid phase. WO 2007 / 093514 discloses a two-stage process for preparing EDA, wherein, in the first process stage, the amination is conducted over a hydroamination catalyst up to an MEA conversion of not more than 40% and, in the second process stage, a supported shaped Ru / Co catalyst body having small geometry is used and the second stage is conducted at a temperature at least 10°C higher than the first process stage. The product streams obtained in the above-described processes are generally separated by distillation to produce individual products in pure form, especially the particularly desired products EDA and DETA. WO 2007 / 093555 discloses that the distillative workup of the reaction products from the MEG conversion is problematic since MEG and DETA form an azeotrope which is supposed to be virtually independent of pressure and therefore cannot be separated by pressure swing distillation. According to WO 2007 / 093555, the azeotropic composition is about 44% by weight of MEG and 56% by weight of DETA and has a boiling point of 154°C at 150 mbar, compared to the boiling point of pure MEG of 144°C and of pure DETA of 142°C, in each case at the above-stated pressure of 150 mbar. WO 2007 / 093555 therefore discloses a process for distillatively separating a product stream from the MEG conversion, in which one stage of the separation sequence is conducted as an extractive distillation with triethylene glycol (TEG). WO 2007 / 093555 discloses a separation sequence including the following steps:

[0024] Introducing the output from the MEG conversion into a first distillation unit K-l and separating the output introduced into a top stream comprising the ethylenediamine and piperazine components, and a bottom stream comprising the components having a boiling point greater than the boiling point of piperazine.

[0025] Introducing the bottom stream from column K-l into a second distillation column K-ll and separating the bottom stream supplied into a top stream comprising monoethylene glycol, diethylenetriamine and monoethanolamine, and a bottom stream comprising components having a higher boiling point than monoethylene glycol and diethylenetriamine.

[0026] Feeding the top stream from column K-ll into an extractive distillation column K-ll I which is fed, at the same separation stage or height, with triethylene glycol as selective solvent for diethylenetriamine, wherein a diethylenetriamine-laden stream comprising the selective triethylene glycol solvent is removed via the bottom, and a monoethylene glycol-comprising stream substantially free of diethylenetriamine is removed overhead in the extractive distillation column K-ll I.

[0027] The bottom stream from the extractive distillation column K-l II, comprising DETA-laden selective solvent, is preferably fed to a desorption column K-IV, and separated therein into a DETA-comprising top stream and a TEG-comprising bottom stream. The TEG-comprising bottom stream from column K-IV is preferably recycled into the extractive distillation column K-ll I.

[0028] WO2019081283 relates to a method of purifying a mixture comprising MEG, MEA, EDA and DETA, and low boilers having a boiling point not higher than PIP and high boilers having a boiling point not lower than AEEA, wherein the process comprises the following steps: a) separating a mixture comprising MEG, MEA, EDA and DETA, and low boilers having a boiling point not higher than PIP and high boilers having a boiling point not lower than AEEA, into

[0029] (I) a mixture A comprising EDA and the low boilers having a boiling point not higher than PIP; and

[0030] (II) a mixture B comprising MEA; and (iii) a mixture C comprising MEG, DETA and the high boilers having a boiling point not lower than AEEA; b) separating mixture C from stage a) into

[0031] (I) a mixture D comprising MEG; and

[0032] (ii) a mixture E comprising MEG, DETA and the high boilers having a boiling point not lower than AEEA; c) separating mixture E from stage b) either into

[0033] (I) a mixture F comprising MEG and DETA; and

[0034] (ii) a mixture G comprising the high boilers having a boiling point not lower than AEEA; or

[0035] (I) a mixture F comprising MEG and DETA; and

[0036] (ii) a mixture G1 comprising AEEA; and

[0037] (iii) a mixture G2 comprising the high boilers having a boiling point higher than AEEA; d) separating mixture F from stage c) by extractive distillation with triethylene glycol into

[0038] (I) a mixture H comprising MEG; and

[0039] (ii) a mixture I comprising DETA and TEG.

[0040] According to WO2019081283, WO2019081283 differs from W02007 / 093555 in that MEA is additionally removed in stage a) and the process of the invention additionally comprises a stage b) in which excess MEG is removed. The additional removal of MEA in stage a) enables the further reaction of MEA with ammonia in a separate reactor. Separate conversion of MEA is claimed to reduce the formation of AEEA, which is of lower commercial value than EDA and DETA. The additional removal of MEG in stage b) is further claimed to enable introduction of the MEG reactant into stage b) before it is converted in stage 1. This is supposed to 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 stream introduced into the extractive distillation (stage d)) is smaller than in the process which is described in WO 2007093555. The smaller flow rate of products that have to be separated in stage d) results in a smaller energy demand and lower thermal stress on the products. Moreover, owing to the smaller flow rate, it is claimed that the apparatus dimensions may be kept smaller, which can have a positive effect on the overall economic viability of the process.

[0041] Within the frame of the present invention, it was found that extractive distillation of MEG / DETA-comprising mixture with TEG can result in a significant discoloration of the individual fractions, such as DETA and / or MEG. Products with coloration are difficult to sell on the market. Accordingly, it was the object of the present invention to provide a method for the manufacture of DETA and MEG being clear in colour and otherwise possessing a high product quality meeting market demand. The object of the present invention was solved by a method for the manufacture of diethylenetriamine (DETA) and / or monoethylene glycol (MEG) from a mixture comprising diethylenetriamine (DETA) and monoethyleneglycol (MEG), comprising the steps of:

[0042] (I) providing a feed stream comprising DETA and MEG;

[0043] (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;

[0044] (ill) separating fraction B obtained in step (ii) in a second distillation column DC2 into a. a fraction C comprising MEG; and b. a fraction D comprising an azeotropic composition of DETA and MEG.

[0045] The following abbreviations are used hereinafter:

[0046] AEEA: aminoethylethanolamine

[0047] AEP: aminoethylpiperazine

[0048] DETA: diethylenetriamine

[0049] EDA: ethylenediamine

[0050] EDC: ethylene dichloride

[0051] HEP: hydroxyethylpiperazine

[0052] HPA: heavy polyamine

[0053] MEA: monoethanolamine

[0054] MEG: monoethylene glycol

[0055] NMEDA: N-methylethylenediamine

[0056] PEHA: pentaethylenehexamines

[0057] PIP: piperazine

[0058] TEG: triethylene glycol

[0059] TEPA: tetraethylenepentamine

[0060] TETA: triethylenetetramine

[0061] Unless specified otherwise, pressure figures relate to the absolute pressure figure.

[0062] The invention can be executed as follows:

[0063] The method according to the invention comprises a first step (I) of providing a feed stream comprising DETA and MEG.

[0064] The feed stream preferably comprises 25 to 75 weight percent of MEG, more preferably 30 to 60 weight percent and most preferably 35 to 55 weight percent.

[0065] The feed stream preferably comprises 25 to 75 weight percent of DETA, more preferably 30 to 65 weight percent and most preferably 40 to 60 weight percent. More preferably, the weight ratio of MEG: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.

[0066] The feed stream may be obtained by mixing MEG / DETA in the respective amounts.

[0067] In a preferred embodiment, the feed stream is obtained by separating an azeotropic mixture of DETA / MEG from a mixture of DETA and MEG 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.

[0068] In one embodiment of the present invention, the feed stream provided in step (i) comprises little or no AEPIP. In the preferred embodiment, the feed stream to step (ii) comprises less than 3 percent by weight of AEPIP, preferably less than 1 weight percent of AEPIP and more preferably less than 0.5 weight percent of AEPIP.

[0069] In another preferred embodiment, the feed stream provided in step (i) comprises AEPIP in a concentration of 3 to 10 weight percent, more preferably 4 to 8 weight percent and most preferably 5 to 7 weight percent.

[0070] The feed stream provided in step (i) is preferably obtained by the conversion of MEG and ammonia to produce a mixture of ethyleneamines and ethanolamines and separating components with a boiling point lower than the MEG / DETA azeotrope at the respective pressure. The individual separation steps are known in the arts and described for example in WO2019 / 081283), PCT / EP2023 / 066376, PCT / EP2023 / 066433, WO2021 / 115907, WO2019 / 081285, WO2019 / 081286, WO2015 / 0135971, WO2011 / 067226, WO2019081283 and W02007 / 093555.

[0071] In a preferred embodiment, the feed stream provided in step (i) is prepared by a by a method comprising the following steps: a. reaction of MEG with ammonia to obtain a primary reaction mixture, and b. separation of ammonia and / or hydrogen from the mixture obtained in step a, and c. separation of water and / or NMEDA from the mixture obtained in step b, d. separation of EDA and PIP, together or sequentially from the mixture obtained in step c, and e. separation of MEA from the mixture obtained in step d, and f. separation of MEG from the mixture obtained in step e, and g. separation of an azeotropic mixture comprising DETA and MEG from the mixture obtained in step f.

[0072] Step a:

[0073] In a preferred embodiment, step a is conducted as described under stage 1) in WO2019 / 081283.

[0074] In another preferred embodiment, step a is conducted as described under step (i-a) of PCT / EP2023 / 066376.

[0075] The reaction of MEG with ammonia usually yields a reaction mixture comprising unconverted MEG and a mixture of ethylene amines and ethanolamines, such as EDA, DETA, TETA, TEPA, PIP, AEPIP, AEEA, HEPIP, diethanolamine (DEOA), and hydroxyethyl diethylenetriamine (HEDETA).

[0076] Step b: In a preferred embodiment, step b is conducted as described under stage 2) in WO2019 / 081283.

[0077] In still another preferred embodiment, step b is conducted as described under step (i-b) of PCT / EP2023 / 066376.

[0078] In step b, ammonia and hydrogen are preferably separated from the mixture obtained in step a.

[0079] Step c: NMEDA / Water separation

[0080] The mixture obtained in step b, after separation of ammonia and / or hydrogen, is preferably subjected to a further separation step c, where water and alkylated side products, in particularly N-methyl ethylenediamine (NMEDA), are separated.

[0081] Usually, water and NMEDA are separated as head products by distillation in one or more columns. In a preferred embodiment, step c is conducted as described under step (ii) of PCT / EP2023 / 066376.

[0082] Step d: PIP / EDA separation

[0083] The mixture obtained in step c after separation of water and / or NMEDA is preferably subjected to yet another separation step in which the lighter boiling components PIP and / or EDA are separated sequentially or together.

[0084] In a preferred embodiment, step d is conducted as described under stage 6 in WO2019 / 081283.

[0085] Step e: MEA separation

[0086] The mixture obtained in step d after separation of EDA and PIP is preferably subjected to another separation step in which MEA is separated as described below.

[0087] In the separation step e, MEA is separated from the mixture obtained in step d.

[0088] In a preferred embodiment, the separation step e is preferably conducted in a rectification 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 a column having random packings or structured packings. Preference is given to using internals with a low pressure drop, such as structured packings, for example in the form of sheet metal packing such as Mellapak 250 Y or Montz Pak (B1-250 type). It is also possible for a packing with lower or elevated specific surface area to be present, or it is possible to use a fabric packing or a packing with another geometry such as Mellapak 252. Y. The advantages for the use of such internals are the low pressure drop and low specific liquid holdup compared to valve trays, for example.

[0089] The internals may be disposed in one or more beds.

[0090] Preferably, the rectification column comprises a structured packing, in particular Mellapak 250.

[0091] The design and layout of the column for the separation of MEA is determined by the capacity which is to be produced. 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. The number of theoretical stages in the column for the separation of MEA is generally in the range from 10 to 80, preferably 20 to 60 and more preferably 30 to 50.

[0092] The energy required for the separation of MEA in the column is typically introduced by an evaporator in the bottom of the column. This evaporator is typically a natural circulation evaporator or forced circulation evaporator. Alternatively, it is possible to use evaporators with a short residence time, such as falling-film evaporators, helical tube evaporators, wiped-film evaporators, or a short-path evaporator.

[0093] The mixture from step d is preferably introduced in a spatial region between 25% and 75% of the theoretical plates of the column. For example, the feed may be introduced to the middle section of the column. Preferably, the feed is preferably introduced between 25 to 75% of the theoretical plates and more preferably between 30 to 70% of the theoretical plates. For examples, if the column has 25 theoretical stages, the feed is preferably introduced between stage 10 and 15.

[0094] The column for the separation of MEA generally has a condenser which is generally operated at a temperature at which the predominant portion of fraction C is condensed at the corresponding top pressure.

[0095] In general, the operating temperature of the condenser is in the range from 10 to 150°C, preferably 50 to 140°C and more preferably 80 to 120°C.

[0096] Suitable condensers are condensers having cooling coils or helical tubes, jacketed tube condensers and shell and tube heat exchangers.

[0097] The top pressure of the column for the separation is preferably lower than the top pressure in the column used in step d.

[0098] Preferably, the top pressure of the column for the separation of MEA in the range of 100 to 10000 mbar, preferably 300 to 800 mbar and most preferably 400 to 600 mbar.

[0099] The column for the separation of MEA can be operated at a bottom temperature of 120 to 250°C, more preferably 140 to 220°C and mor preferably 160 to 200°C.

[0100] The energy required for the evaporation of MEA in the column is typically introduced by a reboiler in the bottom of the column. This reboiler is typically a natural circulation reboiler or forced circulation reboiler. Alternatively, it is possible to use reboilers with a short residence time, such as falling-film reboilers, helical tube reboilers, wiped-film reboilers, or short-path reboilers.

[0101] A fraction, comprising MEA, is preferably drawn-off at the top of column.

[0102] Preferably, the top fraction comprises 1 percent or less by weight of by products, such as PIP and / or MEG, more preferably 0.5 percent by weight or less and most preferably 0.3 percent by weight or less.

[0103] Preferably, a part of the top fraction is refluxed to the top of column for the separation of MEA. The reflux ratio is preferably in the range of 1 to 10, preferably 2 to 8 and most preferably 3 to 5.

[0104] A bottom fraction, comprising MEG, DETA and higher boiling components formed during the conversion of MEG with ammonia is preferably drawn-off as a bottom stream from the column. The bottom fraction is preferably introduced to step f.

[0105] Step f: MEG separation

[0106] From the mixture obtained as bottom product in step e, MEG is preferably separated in step f.

[0107] In the separation step f, MEG is separated from the bottom product obtained in step e.

[0108] In a preferred embodiment, the separation step f is preferably conducted in a rectification 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 a column having random packings or structured packings. Preference is given to using internals with a low pressure drop, such as structured packings, for example in the form of sheet metal packing such as Mellapak 250 Y or Montz Pak (B1-250 type). It is also possible for a packing with lower or elevated specific surface area to be present, or it is possible to use a fabric packing or a packing with another geometry such as Mellapak 252. Y. The advantages for the use of such internals are the low pressure drop and low specific liquid holdup compared to valve trays, for example.

[0109] The internals may be disposed in one or more beds.

[0110] Preferably, the rectification column comprises a structured packing, in particular Mellapak 250.

[0111] The design and layout of the column for the separation of MEG is determined by the capacity which is to be produced. 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. The number of theoretical stages in the column for the separation of MEG is generally in the range from 5 to 50, preferably 7 to 40 and more preferably 10 to 25.

[0112] The energy required for the separation of MEG in the column is typically introduced by an evaporator in the bottom of the column. This evaporator is typically a natural circulation evaporator or forced circulation evaporator. Alternatively, it is possible to use evaporators with a short residence time, such as falling-film evaporators, helical tube evaporators, wiped-film evaporators, or a short-path evaporator.

[0113] The mixture from step d is preferably introduced in a spatial region between 25% and 75% of the theoretical plates of the column for MEG separation. For example, the feed may be introduced to the middle section of the column. Preferably, the feed is preferably introduced between 25 to 75% of the theoretical plates and more preferably between 30 to 70% of the theoretical plates. For examples, if the column has 25 theoretical stages, the feed is preferably introduced between stage 10 and 15.

[0114] The column for the separation of MEG generally has a condenser which is generally operated at a temperature at which the predominant portion of MEG is condensed at the corresponding top pressure. In general, the operating temperature of the condenser is in the range from 10 to 150°C, preferably 50 to 140°C and more preferably 80 to 120°C.

[0115] Suitable condensers are condensers having cooling coils or helical tubes, jacketed tube condensers and shell and tube heat exchangers.

[0116] The top pressure of the column for the separation is preferably lower than the top pressure in the column used in step d.

[0117] Preferably, the top pressure of the column for the separation of MEG in the range of 50 to 800 mbar, preferably 100 to 600 mbar and most preferably 200 to 400 mbar.

[0118] The column for the separation of MEG can be operated at a bottom temperature of 120 to 250°C, more preferably 140 to 220°C and mor preferably 160 to 200°C.

[0119] The energy required for the evaporation of MEG in the column is typically introduced by a reboiler in the bottom of the column. This reboiler is typically a natural circulation reboiler or forced circulation reboiler. Alternatively, it is possible to use reboilers with a short residence time, such as falling-film reboilers, helical tube reboilers, wiped-film reboilers, or short-path reboilers.

[0120] A fraction, comprising MEG is preferably drawn-off at the top of column. Preferably, the top fraction comprises 1 percent or less by weight of by higher boiling products, such as MEA, AEEA and HEPIP, more preferably 0.5 percent by weight or less and most preferably 0.3 percent by weight or less.

[0121] Preferably, a part of the top fraction is refluxed to the top of column for the separation of MEG. The reflux ratio is preferably in the range of 1 to 10, preferably 2 to 8 and most preferably 3 to 5.

[0122] A bottom fraction, comprising MEG, DETA and higher boiling components formed during the conversion of MEG with ammonia, such as AEPIP, AEEA, HEPIP, DEOA, TETA and HEDETA is preferably drawn-off as a bottom stream from the column. The bottom fraction is preferably introduced to step g.

[0123] Step g: MEG / DETA separation

[0124] From the mixture obtained as bottom product in step f, a MEG / DETA fraction is preferably separated in step g.

[0125] In a preferred embodiment, the separation step g is preferably conducted in a rectification 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 a column having random packings or structured packings. Preference is given to using internals with a low pressure drop, such as structured packings, for example in the form of sheet metal packing such as Mellapak 250 Y or Montz Pak (B1-250 type). It is also possible for a packing with lower or elevated specific surface area to be present, or it is possible to use a fabric packing or a packing with another geometry such as Mellapak 252. Y. The advantages for the use of such internals are the low pressure drop and low specific liquid holdup compared to valve trays, for example.

[0126] The internals may be disposed in one or more beds.

[0127] Preferably, the rectification column comprises a structured packing, in particular Mellapak 250.

[0128] The design and layout of the column for the separation of the MEG / DETA fraction is determined by the capacity which is to be produced. 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.

[0129] The number of theoretical stages in the column for the separation of the MEG / DETA fraction is generally in the range from 10 to 80, preferably 20 to 60 and more preferably 30 to 50.

[0130] The energy required for the separation of the MEG / DETA fraction in the column is typically introduced by an evaporator in the bottom of the column. This evaporator is typically a natural circulation evaporator or forced circulation evaporator. Alternatively, it is possible to use evaporators with a short residence time, such as falling-film evaporators, helical tube evaporators, wiped-film evaporators, or a short-path evaporator.

[0131] The mixture from step d is preferably introduced in a spatial region between 25% and 75% of the theoretical plates of the column. For example, the feed may be introduced to the middle section of the column. Preferably, the feed is preferably introduced between 25 to 75% of the theoretical plates and more preferably between 30 to 70% of the theoretical plates. For examples, if the column has 25 theoretical stages, the feed is preferably introduced between stage 10 and 15. The column for the separation of the MEG / DETA fraction generally has a condenser which is generally operated at a temperature at which the predominant portion of the MEG / DETA fraction is condensed at the corresponding top pressure.

[0132] In general, the operating temperature of the condenser is in the range from 10 to 150°C, preferably 50 to 140°C and more preferably 80 to 120°C.

[0133] Suitable condensers are condensers having cooling coils or helical tubes, jacketed tube condensers and shell and tube heat exchangers.

[0134] The top pressure of the column for the separation is preferably lower than the top pressure in the column used in step d.

[0135] Preferably, the top pressure of the column for the separation of the MEG / DETA fraction in the range of 10 to 200 mbar, preferably 25 to 150 mbar and most preferably 50 to 100 mbar.

[0136] The column for the separation of the MEG / DETA fraction can be operated at a bottom temperature of 120 to 250°C, more preferably 140 to 220°C and mor preferably 160 to 200°C.

[0137] The energy required for the evaporation of the MEG / DETA fraction in the column is typically introduced by a reboiler in the bottom of the column. This reboiler is typically a natural circulation reboiler or forced circulation reboiler. Alternatively, it is possible to use reboilers with a short residence time, such as fallingfilm reboilers, helical tube reboilers, wiped-film reboilers, or short-path reboilers.

[0138] A fraction, comprising MEG and DETA, is preferably drawn-off at the top of column.

[0139] Preferably, a part of the top fraction is refluxed to the top of column for the separation of the MEG / DETA fraction. The reflux ratio is preferably in the range of 1 to 10, preferably 2 to 8 and most preferably 3 to 5. A bottom fraction, comprising higher boiling components formed during the conversion of MEG with ammonia, such as AEEA, HEPIP, TETA and HEDETA, is preferably drawn-off as a bottom stream from the column.

[0140] Preferably, the azeotrope of MEG and DETA separated as a top product in step g constitutes the feed stream provided in step (i).

[0141] In a preferred embodiment of the present invention, the feed stream obtained in step g comprises little or no AEPIP. In this preferred embodiment, the feed stream to step (ii) preferably comprises less than 3 percent by weight of AEPIP, more preferably less than 1 weight percent of AEPIP and even more preferably less than 0.5 weight percent of AEPIP.

[0142] In a further preferred embodiment, the feed stream obtained in step g comprises AEPIP in a concentration of 3 to 10 weight percent, more preferably 4 to 8 weight percent and most preferably 5 to 7 weight percent. The amount of AEPIP may be varied by the ratio of NH3 to MEG and by varying the degree of conversion of MEG in step a.

[0143] According to the invention the feed stream comprising DETA and MEG provided in step (i) is subjected to the step of:

[0144] (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.

[0145] In the preferred embodiment the feed stream provided in step (i) is separated in a first distillation column DC1.

[0146] In the separation step (ii), distillation column DC1 is preferably a rectification 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 a column having random packings or structured packings. Preference is given to using internals with a low pressure drop, such as structured packings, for example in the form of sheet metal packing such as Mellapak 250 Y or Montz Pak (B1-250 type). It is also possible for a packing with lower or elevated specific surface area to be present, or it is possible to use a fabric packing or a packing with another geometry such as Mellapak 252. Y. The advantages for the use of such internals are the low pressure drop and low specific liquid holdup compared to valve trays, for example.

[0147] The internals may be disposed in one or more beds.

[0148] Preferably, the rectification column comprises a structured packing, in particular Mellapak 250.

[0149] The design and layout of the column DC1 is determined by the capacity which is to be produced. Typically, the column 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.

[0150] The number of theoretical stages in column DC1 is generally in the range from 5 to 50, preferably 10 to 40 and more preferably 20 to 30.

[0151] The energy required for the separation of the feed provided in step (I) in column DC1 is typically introduced by an evaporator in the bottom of the column. This evaporator is typically a natural circulation evaporator or forced circulation evaporator. Alternatively, it is possible to use evaporators with a short residence time, such as falling-film evaporators, helical tube evaporators, wiped-film evaporators, or a short-path evaporator.

[0152] The feed provided in step (I) comprising MEG and DETA is preferably introduced in a spatial region between 25% and 75% of the theoretical plates of the column DC1 . For example, the feed may be introduced to the middle section of the column. Preferably, the feed is preferably introduced between 25 to 75% of the theoretical plates and more preferably between 30 to 70% of the theoretical plates. For examples, if the column has 25 theoretical stages, the feed is preferably introduced between stage 10 and 15.

[0153] The column DC1 generally has a condenser which is generally operated at a temperature at which the predominant portion of fraction A is condensed at the corresponding top pressure.

[0154] In general, the operating temperature of the condenser is in the range from 10 to 150°C, preferably 50 to 140°C and more preferably 80 to 120°C.

[0155] Suitable condensers are condensers having cooling coils or helical tubes, jacketed tube condensers and shell and tube heat exchangers.

[0156] The top pressure of the column DC1 is preferably less than the pressure in step f.

[0157] Preferably, the top pressure 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 top pressure in the column DC1 is 10 to 100 mbar lower, more preferably 20 to 90 mbar lower and most preferably 40 to 80 mbar lower than the pressure in step f.

[0158] Accordingly, the top pressure in column DC1 is preferably in the range of 1 to 50 mbar, preferably 5 to 40 mbar and most preferably 10 to 30 mbar. In the preferred pressure ranges, the head pressure can sustain reasonable pressure drop along column internals and result in sufficient separation.

[0159] The column DC1 can be operated at a bottom temperature of 50 to 200°C, more preferably 70 to 180°C and mor preferably 100 to 150°C.

[0160] The energy required for the evaporation of the feed provided in step (i) in the column DC1 is typically introduced by a reboiler in the bottom of the column. This reboiler is typically a natural circulation reboiler or forced circulation reboiler. Alternatively, it is possible to use reboilers with a short residence time, such as falling-film reboilers, helical tube reboilers, wiped-film reboilers, or short-path reboilers.

[0161] Fraction A, comprising DETA, is preferably drawn-off at the top of column DC1 .

[0162] Preferably, fraction A comprises 1 percent or less by weight of AEPIP, more preferably 0.7 percent by weight or less and most preferably 0.5 percent by weight or less of AEPIP.

[0163] Fraction B, comprising a mixture of DETA and MEG is preferably drawn-off as a bottom stream from column DC1 . The composition of fraction B usually corresponds to the composition of the DETA / MEG azeotrope at the respective pressure of column DC1 .

[0164] If the feed provided in step (I) also comprises AEPIP, fraction B will preferably also comprise the predominant part of AEPIP, save for the small amount of AEPIP which is separated with the top fraction, as set out above.

[0165] According to the invention, the step (II) is followed by:

[0166] (ill) separating fraction B obtained in step (II) in a second distillation column DC2 into a. a fraction C comprising MEG; and b. a fraction D comprising an azeotropic composition of DETA and MEG.

[0167] The following embodiment of step (ill) is preferred if fraction B comprises little or no AEPIP, e.g., less than 3 percent by weight of AEPIP, preferably less than 1 weight percent of AEPIP and more preferably less than 0.5 weight percent of AEPIP (the variant of step (ill) in which fraction B comprises little or no AEPIP shall be referred to as step (iii)-a):

[0168] In embodiment (iii)-a), fraction B is separated in a second distillation column DC2.

[0169] In the separation step (iii)-a), distillation column DC2 is preferably a rectification 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 a column having random packings or structured packings. Preference is given to using internals with a low pressure drop, such as structured packings, for example in the form of sheet metal packing such as Mellapak 250 Y or Montz Pak (B1-250 type). It is also possible for a packing with lower or elevated specific surface area to be present, or it is possible to use a fabric packing or a packing with another geometry such as Mell apak 252. Y. The advantages for the use of such internals are the low pressure drop and low specific liquid holdup compared to valve trays, for example.

[0170] The internals may be disposed in one or more beds.

[0171] Preferably, the rectification column comprises a structured packing, in particular Mellapak 250.

[0172] The design and layout of the column DC2 is determined by the capacity which is to be produced. Typically, the column 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.

[0173] The number of theoretical stages in column DC2 is generally in the range from 5 to 80, preferably 10 to 50 and more preferably 20 to 40.

[0174] The energy required for the separation of fraction B in column DC2 is typically introduced by an evaporator in the bottom of the column. This evaporator is typically a natural circulation evaporator or forced circulation evaporator. Alternatively, it is possible to use evaporators with a short residence time, such as falling-film evaporators, helical tube evaporators, wiped-film evaporators, or a short-path evaporator. In a preferred embodiment, the reboiler is a forced recirculation reboiler. This reboiler has the advantage that unlike a falling-film type evaporator, the high temperature differential will not result in severe boiling with rupture of the falling film.

[0175] Fraction B is preferably introduced in a spatial region between 25% and 75% of the theoretical plates of the column DC2. For example, the feed may be introduced to the middle section of the column. Preferably, the feed is preferably introduced between 25 to 75% of the theoretical plates and more preferably between 30 to 70% of the theoretical plates. For examples, if the column has 25 theoretical stages, the feed is preferably introduced between stage 10 and 15.

[0176] The column DC2 generally has a condenser which is generally operated at a temperature at which the predominant portion of fraction C is condensed at the corresponding top pressure.

[0177] In general, the operating temperature of the condenser is in the range from 10 to 150°C, preferably 50 to 140°C and more preferably 80 to 120°C.

[0178] Suitable condensers are condensers having cooling coils or helical tubes, jacketed tube condensers and shell and tube heat exchangers.

[0179] The top pressure of the column DC2 is preferably higher than the top pressure in column DC1 . Preferably, the top pressure of column DC2 in the range of 0.5 to 5 bar, preferably 1 to 3 bar and most preferably 1.2 to 2 bar. In the preferred pressure ranges, the products in the column, especially the bottoms, are still thermally stable and discoloration tendency of the products is low. Also in this pressure range, the temperatures are in a range so that the thermal energy can be provided via a pressurized steam being normally readily available at a chemical production site.

[0180] The column DC2 can be operated at a bottom temperature of 150 to 300°C, more preferably 180 to 250°C and mor preferably 200 to 250°C.

[0181] The energy required for the evaporation fraction B in column DC1 is typically introduced by a reboiler in the bottom of the column. This reboiler is typically a natural circulation reboiler or forced circulation reboiler. Alternatively, it is possible to use reboilers with a short residence time, such as falling-film reboilers, helical tube reboilers, wiped-film reboilers, or short-path reboilers. A fraction C, comprising MEG, is preferably drawn-off at the top of column DC2.

[0182] Preferably, fraction C comprises 1 percent or less by weight of DETA and / or AEPIP, more preferably 0.7 percent by weight or less and most preferably 0.5 percent by weight or less.

[0183] Preferably, a part of fraction C Is refluxed to the top of column DC2. The reflux ratio is preferably in the range of 1 to 10, preferably 2 to 8 and most preferably 3 to 5.

[0184] Fraction D, comprising DETA and MEG is preferably drawn-off as a liquid bottom stream from column DC2. The composition of fraction D usually corresponds to the composition of the DETA / MEG azeotrope at the respective pressure of column DC2. Fraction D is preferably recycled to the feed entry point of column DC1.

[0185] In a preferred embodiment of step (iii)-a), column DC2 does not comprises a condenser and the vapors obtained at the top of column DC2 are used to heat the reboiler of column DC1 where it is partially or fully condensed. A part of the condensed stream is recycled to column DC2 as reflux in an amount set out above. A part of the condensed stream condensed in the reboiler of column DC1 is preferably recycled to the stage, where MEG is converted with ammonia.

[0186] The following embodiment of step (ill) is preferred if fraction B comprises AEPIP, e.g. 3 or more percent by weight of AEPIP, preferably 4 or more weight percent of AEPIP and more preferably 5 or more weight percent of AEPIP (the variant of step (ill) in which fraction B comprises AEPIP shall be referred to as step (iii)-b):

[0187] In step (iii)-b fraction B is separated in a second distillation column DC2.

[0188] In the separation step (iii)-a), distillation column DC2 is preferably a rectification 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 a column having random packings or structured packings. Preference is given to using internals with a low pressure drop, such as structured packings, for example in the form of sheet metal packing such as Mellapak 250 Y or Montz Pak (B1-250 type). It is also possible for a packing with lower or elevated specific surface area to be present, or it is possible to use a fabric packing or a packing with another geometry such as Mellapak 252. Y. The advantages for the use of such internals are the low pressure drop and low specific liquid holdup compared to valve trays, for example.

[0189] The internals may be disposed in one or more beds.

[0190] Preferably, the rectification column comprises a structured packing, in particular Mellapak 250.

[0191] The design and layout of the column DC2 is determined by the capacity which is to be produced. Typically, the column 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.

[0192] The number of theoretical stages in column DC2 is generally in the range from 5 to 80, preferably 10 to 50 and more preferably 20 to 40.

[0193] The energy required for the separation of fraction B in column DC2 is typically introduced by an evaporator in the bottom of the column. This evaporator is typically a natural circulation evaporator or forced circulation evaporator. Alternatively, it is possible to use evaporators with a short residence time, such as falling-film evaporators, helical tube evaporators, wiped-film evaporators, or a short-path evaporator. Fraction B is preferably introduced in a spatial region between 25% and 75% of the theoretical plates of the column DC2. For example, the feed may be introduced to the middle section of the column. Preferably, the feed is preferably introduced between 25 to 75% of the theoretical plates and more preferably between 30 to 70% of the theoretical plates. For examples, if the column has 25 theoretical stages, the feed is preferably introduced between stage 10 and 15.

[0194] The column DC2 generally has a condenser which is generally operated at a temperature at which the predominant portion of fraction C is condensed at the corresponding top pressure.

[0195] In general, the operating temperature of the condenser is in the range from 10 to 150°C, preferably 50 to 140°C and more preferably 80 to 120°C.

[0196] Suitable condensers are condensers having cooling coils or helical tubes, jacketed tube condensers and shell and tube heat exchangers.

[0197] The top pressure of the column DC2 is preferably higher than the top pressure in column DC1 . Preferably, the top pressure of column DC2 in the range of 1 to 5 bar, preferably 1 .2 to 3 bar and most preferably 1.3 to 2 bar. In the preferred pressure ranges, the products in the column, especially the bottoms, are still thermally stable and discoloration tendency of the products is low. Also in this pressure range, the temperatures are in a range so that the thermal energy can be provided via a pressurized steam being normally readily available at a chemical production site.

[0198] The column DC2 can be operated at a bottom temperature of 150 to 300°C, more preferably 180 to 250°C and mor preferably 200 to 250°C.

[0199] A fraction C, comprising MEG, is preferably drawn-off at the top of column DC2.

[0200] Preferably, fraction C comprises 1 percent or less by weight of DETA and / or AEPIP, more preferably 0.7 percent by weight or less and most preferably 0.5 percent by weight or less.

[0201] In a preferred embodiment, the vapor exiting the top of column DC2 comprising fraction C is not condensed at the top of column DC2 and the uncondensed vapor comprising fraction C is used to heat the reboiler of column DC1, where fraction C at least partially condenses to form an at least partially condensed fraction C. This preferred embodiment is particularly energy efficient as part of the energy of the hot vapors exiting column DC2 can be exploited to heat the sump of column DC1 . A part of the condensed fraction C is preferably recycled to the head of column DC2 as reflux, the reflux ratio being preferably in the range of 1 to 10, preferably 2 to 8 and most preferably 3 to 5. The other part of the condensed fraction C is preferably recycled to stage 1, i.e., the conversion of MEG with ammonia. Preferably, a part of fraction C Is refluxed to the top of column DC2. The reflux ratio is preferably in the range of 1 to 10, preferably 2 to 8 and most preferably 3 to 5.

[0202] A fraction D, comprising DETA and MEG is preferably drawn-off as a side stream from column DC2. The composition of fraction D usually corresponds to the composition of the DETA / MEG azeotrope at the respective pressure of column DC2. Fraction D is preferably fed or recycled to the feed entry point of column DC1.

[0203] In a preferred embodiment, fraction D is used to heat fraction B in a crossflow heat exchanger prior to feeding fraction B to column DC2. This embodiment is particularly energy efficient. A fraction E comprising DETA is preferably removed from the bottom of column DC2. Fraction E preferably comprise AEPIP. Usually, the fraction E comprises up to 60 percent by weight, preferably up to 55 percent by weight and more preferably up to 50 percent by weight of AEPIP.

[0204] Due to the withdrawal of a separate side stream, it is preferred that distillation column DC2 comprises two rectifying sections and one stripping section, wherein the first rectifying section RS1 is located between the feed of fraction B and the withdrawal of fraction D, and the second rectifying section RS2 is located between the withdrawal of fraction D and the withdrawal of fraction C and the stripping section is located between the feed of fraction B and the withdrawal of fraction E

[0205] The process of the invention for separation of a MEG / DETA mixture, which is preferably obtainable from the conversion of MEG, has provided a process which enables the desired process products of MEG and / or DETA to be obtained in high yield and purity, in particularly a products with a low degree of discoloration. In addition, the energy requirement for the separation of the DETA / MEG azeotrope can be more favourable compared to an extractive distillation with TEG described in prior art.

[0206] DETA produced by the process of the present invention may converted in one or more steps to chemicals, products or materials, such as chelating agents, epoxy resin curing agents, epoxy resins, polyurethane catalysts, polyurethanes, fuel additives, corrosion inhibitors, surfactants, lubricant additives, pharmaceuticals, agrochemicals, ion exchange resins, and adhesives.

[0207] MEG produced by the process of the present invention may converted in one or more steps to chemicals, products or materials, such as polymers, such as polyethylene terephthalate (PET) or polyethylene glycols, ethylene glycol ethers, resins, solvents, antifreeze, coolants, heat transfer fluids, plasticizers, hydraulic fluids, and humectants.

[0208] The process of the invention is elucidated by examples which follow.

[0209] Comparative Example 1 :

[0210] (Concentrations are mass fractions, pressures absolute values)

[0211] A mixture comprising 20.11 % MEG, 16.48 % DETA, 2.99 % AEPIP and 59.94 % TEG was submitted to a batch fractionation. This starting mixture was obtained by distilling a fraction comprising MEG, DETA and AEPIP obtained from the conversion of MEG with NH3 after separation of lower boiling components having a boiling point less or equal than MEG. The recovered and colourless MEG, DETA and AEPIP fractions were mixed with virgin, colourless TEG.

[0212] A column comprising 1000 mm of Sulzer BX packing (about 30 theoretical stages) was used to fractionate the mixture comprising MEG, DETA, AEPIP and TEG. A head pressure of 30 mbar and a reflux rate of 60:3 (= 20) was set, and 11 fractions taken overhead. Fractions 1 to 7 mainly consisted of MEG and / or DETA, while fractions 8 to 11 mainly consisted of TEG. The base temperature of the fractionation column was at the beginning 132.5 °C and increased up to 177.7 °C after completing the withdrawal of the 11thfraction. The head temperature was 101.8 °C at the beginning and increased up to 173.9 °C at the end.

[0213] The first fraction resulted in a pale rose colour, the second was almost colourless, fraction 3 completely colourless. Fraction 4 was pale rose, fractions 5 and 6 colourless, fraction 7 pale yellow. All of these fractions consisted mostly of MEG and / or DETA. The subsequent fractions, consisting mainly of TEG, were deep yellow, the remaining residue in the still was heavily dark brown.

[0214] This example shows that while the original mixture of DETA, AEPIP, MEG and TEG was colourless, a significant discoloration resulted with unknown products that were partly volatile and contaminated recovered MEG and DETA.

[0215] Comparative Example 2

[0216] (Concentrations are mass fractions, pressures absolute values)

[0217] A synthetic mixture of colourless 36 % MEG and 64 % DETA was thermally treated at 213 °C under atmospheric pressure and absolute reflux for 19 hours. No significant discoloration of the thermally treated mixture was observed. Then three fractions of the mixture were distilled, until 60 % of the mixture had evaporated. All three distilled fractions were colourless.

[0218] This experiment demonstrates that no discoloration takes place if TEG-free mixtures of MEG / DETA are thermally treated.

[0219] Example 3

[0220] (Concentrations are mass fractions, pressures absolute values)

[0221] A mixture containing approximately 41 .6 % MEG, 5.3 % DETA and 5.7 % AEPIP was fed into a first column DC1 operated at a head pressure of 15 mbar and consisting of a stripping section with 15 theoretical stages and a rectifying section of 11 theoretical stages (BX-type packing from Sulzer). The feed rate was set to 635 kg / h, the reflux rate was set to 4000 kg / h. Top temperature was 94 °C, base temperature was 121 °C. 316 kg / h were drawn as heads comprising DETA with 5000 ppm AEPIP and no detectable MEG.

[0222] Column DC1 was also fed on top of the stripping section with 1926 kg / h of a recycled stream REC from column DC2. 2245 kg / h were drawn as bottoms of column DC1 and fed onto the top of the stripping section of column DC2.

[0223] Column DC2 comprised of a stripping section with 17 theoretical stages, an intermediate section with 3 theoretical stages and a rectifying section with 13 theoretical stages (Mellapak-type packing by Sulzer). Column DC2 was operated at a pressure of 1 .5 bar with a reflux rate of 2.4 t / h. Top temperature was 211 °C, base temperature was 233 °C. Stream REC was drawn as a liquid side stream from between the intermediate section and the rectifying section and recycled to column DC1 as noted before.

[0224] 250 kg / h were drawn as heads of column DC2 consisting of MEG with 983 ppm DETA and 17 ppm AEPIP. 68 kg / h were drawn as bottoms of column DC2 comprising of a mixture with 19.5 % MEG, 30.5 % DETA and 50 % AEPIP. Both heads of column DC1 (DETA) and column DC2 (MEG) were colourless.

Claims

Claims1 . A method for the manufacture of diethylenetriamine (DETA) and / or monoethylene glycol (MEG) from a mixture comprising diethylenetriamine (DETA) and monoethyleneglycol (MEG), 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;(ill) separating fraction B obtained in step (ii) in a second distillation column DC2 into a. a fraction C comprising MEG; and b. a fraction D comprising an azeotropic composition of DETA and MEG.

2. A method according to claim 1, wherein distillation column DC2 comprises one or more stripping sections and one or more rectifying sections.

3. A method according to at least one of claims 1 or 2, wherein distillation column DC1 is operated at a lower pressure than distillation column DC2.

4. A method according to claim 3, wherein the distillation column DC1 is operated at a head pressure in the range of 1 to 50 mbar and distillation column DC2 is operated at a head pressure in the range of 0.5 bar to 5 bar.

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

6. A 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. A method according to at least one of claims 1 to 7, wherein mixture D is fed to column DC1.

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

9. A 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 draw between the feed of fraction B and the withdrawal of fraction C.

10. A method according to claim 9, wherein distillation column DC2 comprises two rectifying sections and one stripping section, wherein the first rectifying section RS1 is located between the feed of fraction B and the withdrawal of fraction D, and the second rectifying section RS2 is located between the withdrawal of fraction D and the withdrawal of fraction C and the stripping section is located between the feed of fraction B and the withdrawal of fraction E.

11. A method according to claim 10, wherein side draw D is in liquid form.

12. A method according to at least one claims 9 to 11, wherein fraction D is fed to column DC1.

13. A method according to at least one of claims 9 to 12, wherein the vapor exiting the head of column DC2 is used to heat the reboiler of column DC1 .

14. A method according to at least one claims 9 to 13, wherein fraction D is used to heat fraction B prior to feeding fraction B to distillation column DC2.

15. A method according to at least one claims 1 to 14, wherein fraction C is recycled to a reactor in which MEG is converted to ethylenediamine (EDA).

16. A method according to at least one of claims 1 to 15, wherein step (I) comprises the steps of: a. reacting MEG with ammonia to obtain a primary reaction mixture, and b. separation of ammonia and / or hydrogen from the mixture obtained in step a, and c. separation of water and / or NMEDA from the mixture obtained in step b, d. separation of EDA and PIP, together or sequentially from the mixture obtained in step c, and e. separation of MEOA from the mixture obtained in step d, and f. separation of MEG from the mixture obtained in step e, and g. separation of an azeotropic mixture comprising DETA and MEG from the mixture obtained in step f.

17. A method according to at least one of claims 1 to 16, comprising the additional steps of converting DETA or MEG in on or more steps into a chemical, product or a material.