Process for isolation of amines

Abstract

A method for the isolation of amines from their aqueous solutions is provided, comprising the steps of: a) contacting an aqueous solution of the amine with a carboxyl-functionalized adsorbent; b) removing water from the adsorbent; and c) thermally desorbing the amine. The method is particularly suitable for the isolation of ethanolamines.

Description

[Technical Field]

[0001] Technical Field The present invention relates generally to a method for purifying amines from aqueous solutions, particularly dilute aqueous solutions thereof. The present invention also relates to products of the purification method and various uses of these products. [Background technology]

[0002] background Amines are compounds that are formally derived from ammonia, and one, two, or three hydrogen atoms are replaced by substituents, resulting in primary, secondary, or tertiary amines.Typically, the substituents are alkyl or aryl groups, which can optionally have additional functional groups, such as hydroxyl groups, halogen atoms, etc.Amines are widely used in various fields.

[0003] Hydroxylamines, also called amino alcohols, contain a hydroxyl group in addition to an amino group. They are widely used in industrial applications, for example, as solvents, synthetic intermediates, and high-boiling bases.

[0004] A specific hydroxylamine is ethanolamine (HO-CH2-CH2-NH2), which is used in a wide variety of applications, including as a raw material precursor for flavor products. Ethanolamine can also be used for the recovery and removal of acid gases from natural gas, fuel gas, and process gases, the production of monoalkanolamides for nonionic detergents, emulsifiers, and soaps, and the synthesis of acylethanolamines, phenylethanolamines, and 2-mercaptothiazoles in the manufacture of various products.

[0005] Ethanolamine is currently produced on an industrial scale by reacting ethylene oxide with excess ammonia.However, this is not a natural process, and therefore cannot be used to produce natural flavor components.WO 2007 / 144346, the contents of which are incorporated herein by reference, discloses a natural process for producing ethanolamine, involving the fermentation of ethanolamine-producing bacteria.WO 2020 / 011725 refers to the isolation of ethanolamine from fermented compositions by distillation to obtain naturally produced ethanolamine of food grade.

[0006] It would therefore be desirable to provide new and / or improved methods for purifying amines, particularly hydroxylamines, from aqueous compositions, such as wastewater or fermentation compositions. Summary of the Invention

[0007] overview According to a first aspect of the present invention there is provided a process for the isolation of an amine from its aqueous solution, comprising the steps of: a) contacting an aqueous solution of an amine with an adsorbent functionalized with carboxyl groups; b) removing water from the adsorbent; and c) thermally desorbing the amine A method is provided, comprising:

[0008] According to a second aspect of the present invention, there is provided, inter alia, a method for the isolation of ethanolamine from its aqueous solution.

[0009] Certain embodiments of any aspect of the present invention may provide one or more of the following advantages: Economical access to amines provided in dilute solutions; especially · Lower energy demand for the separation process; · Reduced solvent requirements; High purity of the desired amine; Higher yields of the desired amine; and Easy scale-up for increased throughput.

[0010] The details, examples, and preferences provided with respect to any particular one or more of the described aspects of the invention are further explained herein and apply equally to all aspects of the invention. Any combination of the embodiments, examples, and preferences described herein in all possible variations thereof is encompassed by the present invention unless otherwise indicated herein or clearly contradicted by context. [Brief explanation of the drawings]

[0011] [Figure 1a] FIG. 1a shows the chemical structure of a porous methacrylate-based adsorbent. [Figure 1b] FIG. 1b shows the chemical structure of the non-functionalized porous methacrylate-based adsorbent. [Figure 2] FIG. 2 shows the FT-IR spectrum.

[0012] Detailed Description The present invention is based on the surprising discovery that amines can be efficiently isolated from aqueous solutions by an adsorption / desorption sequence using functionalized adsorbents.

[0013] Accordingly, there is provided a method for the isolation of an amine from its aqueous solution, comprising the steps of: a) contacting an aqueous solution of an amine with an adsorbent functionalized with carboxyl groups; b) removing water from the adsorbent; and c) thermally desorbing the amine A method is provided herein, comprising:

[0014] By this method, the amine can be obtained in pure form and no further steps of solvent separation or elimination are required.

[0015] Adsorption is an affinity separation method suitable for separating substances from dilute solutions. After adsorption, the adsorbate must be desorbed from the adsorbent to complete the isolation process and regenerate the adsorbent.

[0016] As used herein, the term "aqueous solution" refers to an aqueous solution containing one or more amines in any possible amount or concentration, which is determined by the solubility of the particular amine in water.

[0017] The term "dilute aqueous solution" refers to an aqueous solution containing an amine in a concentration range of up to 5% by weight or less, e.g., up to 4% by weight, or up to 3% by weight. For example, the concentration of the amine can be as high as possible, but is limited by the solubility of the amine. Another upper limit may be the concentration of the amine that is harmful to microorganisms involved in the formation process.

[0018] As used herein, the term "adsorption" refers to the process of attachment of an amine to an adsorbent by the formation of a complex between the amine and the carboxyl groups of the adsorbent, which complexation causes the amine to be retained on the adsorbent.

[0019] As used herein, the term "adsorbent" refers to a suitable medium capable of adsorbing a particular substance with which it is brought into contact. In other words, an adsorbent can retain or accumulate an adsorbate on its surface. In the present invention, an adsorbent is a matrix or support functionalized with carboxyl groups capable of complexing with the amine groups of the adsorbate. The adsorbent matrix or support can be a porous material such as silica gel, zeolite, or a polymeric adsorbent based on, for example, poly(meth)acrylate or polystyrene.

[0020] As used herein, the term "adsorbate" refers to the substance that is adsorbed, i.e., the amine.

[0021] As used herein, the term "desorption" refers to the opposite of adsorption and means that an adsorbate is released from an adsorbent.

[0022] In step a) of the method of the present invention, an aqueous solution of an amine is contacted with an adsorbent functionalized with a carboxyl group. This contact allows the formation of a complex between the amine and the carboxyl group of the adsorbent. The majority of the aqueous solution is water, which does not further interact with the adsorbent and can be removed. As used herein, the term "contact" refers to any possible technique for combining the aqueous solution with the adsorbent, such as mixing, pumping, charging, etc.

[0023] If the aqueous solution contains additional chemical compounds, selectivity of the adsorbent for the main compound of interest is required, but selectivity of the adsorbent for the additional chemical compounds is not required. However, if such selectivity is not provided, additional separation or purification steps may be applied after isolation of the main compound mixed with one or more additional chemical compounds from the aqueous solution. For example, if the aqueous solution contains different amines, the method allows for isolation of a mixture of amines, not necessarily individual amines. Their separation can then be achieved by other techniques.

[0024] The pH of the aqueous solution needs to be controlled because the amine functionality should not be protonated to allow complexation with the carboxyl groups of the adsorbent. The amine-containing aqueous solution should be adjusted to a pH below the pK of the amine to ensure that at least 50% of the amine is available for adsorption. a The pH should be above 1.

[0025] The amount of amine that can be removed from an aqueous solution depends on the capacity of the adsorbent. As used herein, the term "capacity" refers to the effectiveness of adsorption. It is often defined as the mass of adsorbate per kilogram of adsorbent. When the capacity limit of the adsorbent is reached, in other words, when all carboxyl groups are occupied, the adsorbent cannot take up any more adsorbate. This total loading can be continuously monitored, for example, by measuring the conductivity at the outlet of the column or by gas chromatography of individual samples of the eluent. At the point of total loading, also known as the breakthrough point, the amine concentration at the outlet rapidly increases to the inlet amine concentration.

[0026] Optionally, after contacting the aqueous solution of amine with the carboxyl-functionalized adsorbent, a washing step is added. For example, the loaded adsorbent is washed with water to remove residues, such as salts, present in the aqueous solution. This optional step removes the salts, which are not present in the final product obtained after completion of the proposed method.

[0027] In step b) of the method of the present invention, water is removed from the adsorbent. In a first step, water can be removed by draining, decanting, or flushing with air or nitrogen, preferably compressed air or nitrogen. In a further step, the remaining water is removed by flushing with compressed, preheated nitrogen. Once the nitrogen stream flowing through the cooled, efficient condenser no longer carries water, water removal is complete and condensation no longer occurs.

[0028] In step c) of the method of the present invention, the adsorbed amine is thermally desorbed from the adsorbent, so that once the water is removed, the temperature of the system is increased to reverse the amine-carboxyl complex, resulting in the amine, which can be collected, for example, by condensation in pure form.

[0029] The advantage of this method is that the amine can be obtained in pure form by thermal desorption. No further steps of solvent separation or removal are required. An alternative to direct desorption of the amine is washing with a suitable solvent. However, the amine is provided in solution, requiring an additional separation step.

[0030] In one specific embodiment, the amine is an alkanolamine, also known as an aminoalcohol. Alkanolamines contain hydroxyl and amino functional groups and are useful in many industrial applications, particularly 2-aminoalcohols.

[0031] In one specific embodiment, the alkanolamine is ethanolamine.

[0032] In a further embodiment, the adsorbent is thermally stable to at least 150° C., preferably at least 160° C., or even at least 170° C. This allows for handling of the adsorbent at elevated temperatures, particularly during water removal (step b) and amine desorption (step c).

[0033] In a further embodiment, step b), removing water, comprises flushing the vessel containing the adsorbent with a compressed nitrogen stream, while either the nitrogen stream or the vessel containing the adsorbent is heated to an elevated temperature.

[0034] For example, the nitrogen stream for removing water is heated to at least 70°C, or to 80°C, or to 90°C, or to 100°C.

[0035] For example, to remove water, the vessel containing the adsorbent is heated to at least 80°C, preferably to 90°C, or to 100°C, or to 110°C.

[0036] In a further embodiment, step b), removing water, comprises flushing the adsorbent-containing vessel with a compressed nitrogen stream, while the nitrogen stream and the adsorbent-containing vessel are independently heated to elevated temperatures, for example, the nitrogen stream to at least 70°C, or to 80°C, or to 90°C, or to 100°C, and the adsorbent-containing vessel to at least 80°C, preferably to 90°C, or to 100°C, or to 110°C.

[0037] In a further embodiment, step b) comprises flushing the vessel containing the adsorbent with a compressed nitrogen stream, while the nitrogen stream is heated to about 70°C and the vessel containing the adsorbent is heated to about 110°C.

[0038] When the nitrogen stream flowing through the cooled, efficient condenser is no longer carrying water, water removal is complete and condensation no longer occurs.

[0039] In a further embodiment of the present invention, the thermal desorption of the amine in step c) occurs at an elevated temperature. This temperature must be higher than the boiling point of water and sufficient to provide the activation / binding energy of the amine-carboxyl complex. Meanwhile, the upper limit should be below the temperature required for the formation of a covalent amide bond. The amide bond is not reversible and therefore deactivates the carboxyl functionality of the adsorbent. Amide formation must be minimized to allow the adsorbent to be reused in multiple adsorption-desorption cycles. The optimum temperature may vary slightly for a given amine and alkanolamine, but all are in a similar range.

[0040] Finally, any operation should be carried out below the maximum operating temperature of the adsorbent.

[0041] For example, the desorption step c) should be carried out at a temperature in the range of 100°C to 150°C, preferably 105°C to 145°C, more preferably 110°C to 140°C.

[0042] To ensure the temperature during the thermal desorption step c), the nitrogen stream or the vessel containing the adsorbent is heated to an elevated temperature.

[0043] For example, the nitrogen stream for desorption of amines is heated to at least 100°C, or to 110°C, or to 120°C, or to 130°C, or to 140°C, or to 150°C.

[0044] For example, for desorption of amines, the vessel containing the adsorbent is heated to at least 120°C, or to 130°C, or to 140°C, or to 150°C, or to 160°C, or to 170°C.

[0045] In a further embodiment, step c) is carried out while the nitrogen stream and the vessel containing the adsorbent are independently heated to elevated temperatures, for example, the nitrogen stream to at least 100°C, or to 110°C, or to 120°C, or to 130°C, or to 140°C, or to 150°C, and the vessel containing the adsorbent to at least 120°C, or to 130°C, or to 140°C, or to 150°C, or to 160°C, or to 170°C.

[0046] In a further embodiment, step c) is carried out while the nitrogen stream is heated to about 110°C and the vessel containing the adsorbent is heated to about 170°C.

[0047] For example, the desorbed amine is collected in a cooled condenser, the temperature of which can be adjusted to a temperature below 10°C, preferably below 5°C or lower, for example, to the amine to be isolated.

[0048] In a further embodiment, the adsorbent has a porous polymethacrylate matrix, which is robust and can withstand handling at higher temperatures, under pressure, and at different pH conditions. Alternatively, the adsorbent matrix can be selected from the group consisting of silica gel, zeolite, or polymeric adsorbents such as polyacrylate or polystyrene.

[0049] In a further embodiment of the invention, the adsorbent is provided in a container selected according to the mode of the method, for example the container can be a column, vessel, beaker, etc.

[0050] For example, if the vessel is a column, the method can be carried out by pumping the aqueous solution through the column during steps b) and c), during which a nitrogen stream, e.g., a compressed nitrogen stream, can be applied. Alternatively, the method can be carried out with the adsorbent provided in a beaker. The aqueous solution can be simply mixed first and drained in step b, followed by heating in step c). The choice of vessel and operating mode contributes to the efficiency of the method.

[0051] Adsorbents can exhibit significant volume expansion upon adsorbing amines. The potential volume expansion can be determined in advance using the adsorbent in a vessel with sufficient free volume above the adsorbent bed. For example, the volume expansion can be measured as the increase in the height of the adsorbent bed when fully saturated with amine. For example, Diaion™ WK11 adsorbent expands to ~60% of its initial height upon adsorbing ethanolamine. From this measurement, the relative volume expansion can be calculated for any volume used, and therefore the appropriate amount of adsorbent can be calculated. By taking the volume expansion of the adsorbent into account, the experimental setup can be optimized, for example, by optimizing the loading of the column with the adsorbent. This is particularly important when the method is used on an industrial scale.

[0052] In a further embodiment of the present invention, the adsorbent can be used in multiple adsorption-desorption sequences, thereby further enhancing the economic benefits of the process.

[0053] In a further embodiment, the aqueous solution is a fermentation composition. Alternatively, the aqueous solution is wastewater from any industrial process. It may be of interest to obtain purified amines, to provide purified water, or both.

[0054] In further embodiments, the provided methods result in amines having a purity of about 60% or greater, or greater than about 70%, preferably greater than about 80%, even more preferably greater than about 90%, or even more preferably greater than about 95%. For example, the amine contains only water, especially if the optional washing step is performed after completion of step a) of the method.

[0055] In further embodiments, the methods provided provide access to purified amines in yields of about 80% or greater, such as about 85% or greater, or even 90%.

[0056] The purity of the amine and its yield depend largely on the efficiency of the process and can be influenced by process parameters. For example, when the process is carried out in a column, column design plays a key role. Because the adsorption step (a) is highly efficient and much less sensitive than the desorption step (c), column design parameters are mostly defined by and optimized for the desorption step. The three primary design parameters are i) column diameter to maximize heat transfer from the jacket and nitrogen stream, ii) jacket temperature, and iii) nitrogen stream temperature to optimize heat transfer. The cumulative effect of optimizing these three design parameters is maximized amine desorption and minimized amide formation. Example 3 introduces techniques for measuring the impact of any adjustments to these three design parameters, as demonstrated for ethanolamine.

[0057] The process, including the described method, can be easily scaled up from pilot scale to commercial scale, for example, by adding several identical columns in parallel to form a bundle of identical columns, all of which contain the appropriate adsorbent. Such a bundle can be housed in a structure that acts as a heating jacket around the entire bundle. The heating medium required during steps (b) and (c) is then circulated through this housing structure. A similar design is available for the heat exchanger, called a shell-and-tube heat exchanger. By analogy, the adsorbent-containing columns can be compared to the tubes of a shell-and-tube heat exchanger, and the housing structure can be compared to the shell of the shell-and-tube heat exchanger. The amine-containing solution can be distributed among the bundle of adsorbent-containing columns using a fluid distributor, the design of which is also familiar to the manufacture of shell-and-tube heat exchangers.

[0058] In a further embodiment, the method for isolation of ethanolamine further comprises synthesis of ethanolamine by fermenting a carbon source in the presence of an ethanolamine-producing microorganism to provide a fermentation composition comprising ethanolamine. The described method, when starting from natural materials derived from natural sources, provides a completely natural process for providing ethanolamine.

[0059] Example General: Ethanolamine (≥99%) and HCl (1 M) were supplied by Merck KGaA. Demineralized water was produced by a Milli-Q® laboratory water purification system with a resistivity of 18.2 MΩ.cm. The adsorbents, Diaion™ WK11 and Diaion™ HP2MGL, were purchased from Alfa Aesar. For these experiments, an aqueous solution of ethanolamine was prepared at a concentration of 5 wt.%.

[0060] Example 1: Isolation of ethanolamine using the functionalized adsorbent Diaion WK11 Diaion™ WK11 (WK11) is a porous methacrylate-based adsorbent functionalized with carboxyl groups. Its chemical structure is shown in Figure 1a. It is thermally stable up to 150 °C. When fully saturated with ethanolamine, WK11 theoretically demonstrates an adsorption capacity of ∼550 g of ethanolamine per kg of adsorbent.

[0061] Theoretical adsorption capacity QT(Q 理論 ) can be calculated as follows:

number

[0062] An aqueous solution of ethanolamine (5 wt%) was pumped through a column containing 20 g of Diaion™ WK11 (used as received) at a flow rate of 2.5 mL / min, and samples were taken from the eluate over time to identify the breakthrough point. Liquid remaining in the column after pumping was stopped was flushed from the column with a compressed nitrogen stream. Residual water was then removed from the column using a heating bath, preheating the compressed nitrogen stream to ~70 °C using silicone oil and heating the jacket to ~110 °C. The nitrogen stream, now carrying water vapor and a small amount of ethanolamine vapor, was then directed to a cooled condenser at 2 °C to condense the vapors and determine their ethanolamine content. Residual water was removed from the column in ~90 min. The heating bath then preheated the compressed nitrogen stream to ~110 °C and heated the column jacket to ~170 °C for the desorption step, which reversed the carboxyethanolamine complex and desorbed molecular ethanolamine. Here, molecular ethanolamine was collected by directing the nitrogen stream carrying the ethanolamine vapor into a cooled condenser at 2° C. The desorption step lasted for ∼90 min.

[0063] The adsorption / water removal / desorption sequence according to the procedure described above was carried out in multiple cycles. The observed ethanolamine capacity (g エタノールアミン / kg WK11 The yield (in wt%), purity (in wt%), and desorption yield (in wt%) are shown in Table 1: [Table 1]

[0064] As can be seen in Table 1, after the first adsorption step, an adsorption capacity close to the theoretical adsorption capacity of WK11 (~550 g エタノールアミン / kg WK11 This value decreased to ~150g over the following five cycles. エタノールアミン / kg WK11 The operating adsorption capacity was stable. High ethanolamine purity of >95 wt% was delivered throughout all cycles. The ethanolamine collected in these high-purity fractions accounted for ~85 wt% of the adsorbed ethanolamine, thus demonstrating a high yield. The lost wt% ethanolamine was collected in the water fraction obtained during the water removal step between the adsorption and desorption steps.

[0065] Example 2: Isolation of ethanolamine using the non-functionalized adsorbent Diaion™ HP2MGL (comparison example) Diaion™ HP2MGL (HP2MGL) is a non-functionalized porous methacrylate-based adsorbent. Its matrix is ​​nearly identical to that of WK11. Its chemical structure is shown in Figure 1b. The carboxyl groups of WK11 are esterified with HP2MGL, and different crosslinkers are used: divinylbenzene for WK11 and ethylene glycol for HP2MGL.

[0066] Adsorption experiments were performed with HP2MGL under the same conditions as in Example 1, revealing that ethanolamine could not be adsorbed in the absence of carboxyl groups. No adsorption occurred, as the feed and eluent collected after exiting the column or after being in the column when the feed stream was stopped had identical concentrations of ethanolamine. Table 2 shows the adsorption capacities (g) of WK11 and HP2MGL for ethanolamine. エタノールアミン / kg WK11 ) are compared. [Table 2]

[0067] HP2MGL is classified by the manufacturer as a strongly hydrophilic adsorbent, but ethanolamine is so hydrophilic that water is the preferred adsorbent, demonstrating the importance of carboxyl groups in the adsorbent for the isolation of amines by the method of the present invention.

[0068] Example 3: Capacity reduction study A sample of the adsorbent was collected after the third adsorption-desorption cycle for FT-IR analysis to determine the reason for the loss of capacity after the first cycle. The collected sample was divided into two halves, one of which was washed with 1 M HCl solution to chemically desorb any ethanolamine that had not been thermally desorbed. The sample was then rinsed with Milli-Q® water and acetone and dried prior to FT-IR analysis. A fresh adsorbent sample was also rinsed with Milli-Q® water and acetone and dried for FT-IR analysis to serve as a reference. Infrared spectra were recorded using a Tensor II FT-IR spectrometer (Bruker, Ettlingen, Germany) equipped with a globe source and a DTGS detector. An attenuated total reflectance unit (ATR, Specac, Riverhouse, Kent, UK) was positioned in the spectrometer's optical path. The ATR unit had a horizontally oriented 1.4 mm × 1.4 mm planar diamond shape. For solid measurements, the sample was brought into intimate contact with the diamond surface by applying some additional pressure with a sapphire-tipped screw. Eighty scans were accumulated for both the sample spectrum and the background spectrum (empty diamond). The resulting absorbance infrared spectrum was calculated using these two measurements.

[0069] Figure 2 shows the FT-IR spectra of the fresh adsorbent (bottom), the adsorbent after three cycles (middle), and the adsorbent after three cycles that had been washed with HCl, Milli-Q® water, and acetone and then dried (top). The spectrum of the fresh adsorbent (Figure 2, bottom) shows a predominant peak at 1695 cm-1 The C=O stretching band of the carboxyl group at 1069 cm can be observed. In the spectrum of the adsorbent after the third cycle (Figure 2, center), several prominent features of ethanolamine are observed, especially the C-N (1069 cm) band. -1 ) and CO(1016cm -1 ) stretching bands can be observed. -1 There is NH2 that bends at 2941 cm. The CH stretching vibration of the CH2 group is -1 But I can see it. 3200cm -1 The broad band with a maximum at 1631 cm can be assigned to the OH and NH stretching vibrations. -1 In the IR spectrum of the washed adsorbent after the third cycle (Figure 2, top), a small band corresponding to the amide C=O stretching vibration is visible at 1695 cm -1 Several signals at 1627 cm are visible, most likely due to small residual amounts of undesorbed ethanolamine. -1 The amide band at 0.05 is still visible, indicating that some ethanolamine is covalently linked to the adsorbent via an amide bond.

[0070] We conclude that both undesorbed ethanolamine and amide formation contributed to the loss of adsorption capacity after the first cycle. It is assumed that the adsorbent particles adjacent to the jacket suffered permanent capacity loss due to amide formation. However, because the porous methacrylate-based matrix is ​​a poor heat transfer medium, the same adsorbent particles adjacent to the jacket acted as a heat shield to protect the rest of the adsorbent bed from permanent capacity loss. Therefore, improved heat transfer is necessary to desorb undesorbed ethanolamine from the intact carboxylethanolamine complex.

[0071] This analytical procedure using FT-IR is a simple technique for designing and optimizing columns for any amine of interest. Column diameter, jacket temperature, and nitrogen temperature can be adjusted accordingly to optimize heat transfer and thus maximize amine desorption and minimize amide formation.

Claims

1. 1. A process for the isolation of an amine from its aqueous solution, comprising the steps of: a) contacting an aqueous solution of an amine with an adsorbent functionalized with a carboxyl group; b) removing water from the adsorbent; and c) thermally desorbing the amine The method comprising:

2. 2. The method of claim 1, wherein the amine is an alkanolamine.

3. 3. The method of claim 2, wherein the alkanolamine is ethanolamine.

4. The method according to any one of claims 1 to 3, wherein an additional washing step is added after contacting the aqueous solution of the amine with the carboxyl-functionalized adsorbent.

5. 3. The method of claim 1 or 2, wherein the aqueous solution is a fermentation composition.

6. 10. The process of claim 1, wherein the desorbed amine is collected in a cooled condenser.

7. 10. The method of claim 1, wherein the method results in an amine having a purity of about 60% or more, or greater than about 70%, preferably greater than about 80%, even more preferably greater than about 90%, or even more preferably greater than about 95%.

8. 2. The method of claim 1, wherein the yield of purified amine is about 80% or more, such as about 85% or more, or even 90%.

9. 4. The method of claim 3 for the isolation of ethanolamine, the method comprising synthesizing ethanolamine by fermenting a carbon source in the presence of an ethanolamine producing microorganism to provide a fermentation composition comprising ethanolamine.

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