Purification of amines by adsorption using superadsorbents

Abstract

The present invention describes a method for removing metals present in a mixture containing one or more organic amines, comprising the step of contacting the mixture with a silica-polyethylenimine adsorbent.

Description

[[Technical Field]]

[0001] High-purity amines are desired in many applications, for example, electronic engineering processes and pharmaceutical manufacturing processes. In some applications, it is desirable for the metal ion impurity content to be less than 10 ppb. However, few processes for removing metal ions from organic solutions such as amines have been reported. Rather, most available literature typically focuses on removing metal ions from aqueous solutions. The use of ion exchange resins is the most commonly studied process for removing metal ions, and includes the use of chelating resins with different functional groups. However, the use of such techniques to remove metal ions from amine solutions is challenging due to issues of strong binding affinity between metal ions and amines or incompatibility between such resins and amines.

[0002] The present invention discloses the use of a special class of superadsorbents for removing trace metal impurities from amines. The adsorbent is based on silica particles modified with branched polyethyleneimine. The method described provides a high adsorption capacity for most metal impurities present in organic amines. [[Mode for Carrying Out the Invention]]

[0003] The present invention describes a method for removing metal present in a mixture containing one or more organic amines, the method comprising the step of contacting the mixture with a silica-polyethyleneimine adsorbent.

[0004] Theoretically, any solution of an amine containing metal ion impurities can benefit from the present invention, as all have amine functional groups that are subject to metal removal in most techniques commonly used for the removal of metal impurities. The amine(s) may be alkylamines and / or aromatic amines. The amine(s) may be primary amines, secondary amines, tertiary amines, cyclic amines, or combinations thereof. These include monoethanolamine (MEA), diethanolamine (DEA), triethanolamine (TEA), monoisopropanolamine (MIPA), diisopropanolamine (DIPA), triisopropanolamine (TIPA), n-methyldiethanolamine (MDEA), n-methylethanolamine (NMEA), ethylenediamine (et It contains a mixture of hylenediamine (EDA), piperazine (PIP), diethylenetriamine (DETA), aminoethylethanolamine (AEEA), aminoethylpiperazine (AEP), triethylenetetramine (TETA), tetraethylenepentamine (TEPA), dimethylethanolamine (DMEA), polyethylene polyamine, and pentaethylenehexamine.

[0005] These amine materials may be neat, or contained individually or in a solvent in a mixture of two or more of these materials. The solvent may be water or any organic solvent (and combinations thereof) that is compatible with the amine. The organic solvent may be an alcohol, benzene, or ether.

[0006] This method includes the step of contacting a pure amine or amine mixture with a silica-polyethyleneimine adsorbent. Suitable silica-polyethyleneimine adsorbents are described in the following publications: U.S. Patent No. 2021 / 0016246 A1, U.S. Patent No. 2021 / 0017047, "Novel Polyethylenmeimine-Acrylamide / SiO2 Hybrid Hydrogel Sorbent for Rare-Earth-Element Recycling from Aqueous Sources" by Qiuming Wang, Walter C. Wilfong, Brian W. Kail, Yang Yu, and McMahan L. Gray, "ACS Sustainable Chemistry & Engineering," September 14, 2017; "Recovering Rare Earth Elements from Aqueous Solution with Porous Amine-Epoxy Networks" by Walter Christopher Wilfong, Brian W. Kail, Tracy L. Bank, Bret H. Howard, and McMahan L. Gray, "ACS Applied Materials & Interfaces," May 12, 2017, Qiuming Wang, Brian "Amine Sorbents for Selective Recovery of Heavy Rare-Earth Elements (Dysprosium,Ytterbium) from Aqueous Solution" by W. Kail, Walter C. Wilfong, Fan Shi, Thomas J. Tarka, and McMahan L. Gray, Walter Christopher Wilfong, Brian w. Kail, Qiuming Wang, Fan Shi, Greg Shipley, Thomas J. Tarka, and McMahan L.This is described by Gray in "ChemPlusChem," 2020, 85 130-136, and in "Stable Immobilized Amine Sorbents for Heavy Metal and REE Removal from Industrial Wastewaters," "Environ.Sci:Water Res.Technol.," 2020, 6, 1286.

[0007] Silica-polyethyleneimine adsorbents are polyethyleneimine-modified silica particles, which include a silica support, a crosslinking agent bound to the silica support, and polyethyleneimine bound to the crosslinking agent. Polyethyleneimine can be in linear, branched, or dendrimeric form. Preferably, polyethyleneimine is in branched or dendrimeric form. It is theorized that imine functional groups have a higher affinity for metal ions than amines, and highly branched materials have potentially more functional groups of different kinds and therefore have an even higher affinity for metal ions. Linear polyethyleneimines all contain secondary amines. Branched polyethyleneimines may contain primary, secondary, and tertiary amino groups. Dendrimeric polyethyleneimines contain primary and tertiary amino groups. The weight molecular weight of polyethyleneimine ranges from 500 Da, preferably 800 Da, 5,000 Da, or 10,000 Da, to 50,000 Da, 75,000 Da, 90,000 Da, or 1,000,000 Da.

[0008] Silica-polyethyleneimine-modified silica supports can preferably be prepared using crosslinking agents that are generally known in the art. The crosslinking agents may include epoxysilane linkers, triepoxyd linkers, or acrylamide-based linkers. Preferred crosslinking agents include 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane (ECTMS), bisphenyl A diglycidyl ether, N,N-diglycidyl-4-glycidyloxyanaline (E3), or 4,4'-methylenebis (N,N-diglycidylaniline), acrylamide, N,N'-methylenebisacrylamide, or mixtures thereof.

[0009] Silica-polyethyleneimine adsorbents can be brought into contact with amine-containing mixtures in any preferred manner. For example, this can be done in a batch process in which the silica-polyethyleneimine adsorbent is added to the amine-containing mixture, preferably involving stirring, shaking, or some other process to increase contact between the adsorbent and the metal impurities in the amine. Generally, the rate of impurity removal in such a batch process and the resulting level of impurities remaining in the amine-containing mixture are functions of the effectiveness of the particular adsorbent, the amount of adsorbent relative to the amount of amine-containing mixture, the stirring rate, and the duration of contact, as understood by those skilled in the art.

[0010] It is also possible to have a continuous process of contacting an amine or amine-containing mixture with an adsorbent. This can be conveniently done by passing the amine-containing mixture through a fixed bed of silica-polyethyleneimine adsorbent. The bed volume (or bed volume (BV)) can be configured according to the level of contaminants present in the starting material and the desired purity level of the final product, with larger bed volumes generally allowing for larger amounts of removal in a shorter time.

[0011] The efficiency of impurity removal from a fixed bed is also a function of the flow rate of the mixture through the fixed bed. The flow rate of the mixture through the bed can be advantageously adjusted to a range of 1 to 30 BV per hour, more preferably 1 to 10 BV per hour, where BV is the volume of the bed. For example, if the bed volume of the adsorbent is 1 liter, the flow rate can be advantageously set to a rate in the range of 1 to 30 liters per hour, more preferably 1 to 10 liters per hour. As will be understood by those skilled in the art, a slower flow rate results in the removal of more impurities for a given system, but adds time to the process.

[0012] In some embodiments, the mixture may pass through two or more fixed beds of silica-polyethyleneimine adsorbent. These additional beds may be arranged in parallel or in series, or, if at least three beds are used, a combination of parallel and series configurations may be used.

[0013] The process of contacting an amine-containing mixture with a silica-polyethyleneimine adsorbent (whether a batch or continuous process) can be carried out at any temperature in the range from the freezing point of the mixture to just below its boiling point.

[0014] The silica-polyethyleneimine adsorbent can be advantageously washed with water or other solvents before contact with the mixture to remove potential contaminating impurities from the adsorbent material, thus extending the adsorbent's lifespan and improving its metal removal efficiency. Preferably, this washing can be performed two or more times to remove even more contaminating impurities from the fresh adsorbent.

[0015] During use, metal impurities removed from the amine accumulate on the adsorbent over time. Therefore, it may be desirable to periodically regenerate the adsorbent. This can be conveniently achieved by contacting the adsorbent with a weak acid liquid or weak acid aqueous solution at any temperature ranging from the freezing point of the liquid to just below the boiling point. A weak acid is an acid that partially dissociates into its ions in aqueous solution or water. Examples of weak acids include acetic acid, formic acid, hydrocyanic acid, hydrofluoric acid, hydrogen sulfide, trichloroacetic acid, or mixtures thereof. The pH of such a weak acid liquid or weak acid aqueous solution is in the range of 2 to 7. It may also be possible to regenerate the adsorbent using other materials with which metal ions have a higher affinity, such as ammonia, which is a stronger amine (compared to the adsorbent).

[0016] Using the method of the present invention, the level of metal impurities in an amine-containing mixture can be reduced to less than 10 ppb, or to a level of metal contaminants less than 5 ppb.

[0017] experiment Materials: Unwashed branched polyethyleneimine-modified silica adsorbent was used as the adsorbent in each of the following examples. The adsorbent is described in the following references: U.S. Patent No. 2021 / 0016246 A1, U.S. Patent No. 2021 / 0017047, "Novel Polyethylenmeimine-Acrylamide / SiO2 Hybrid Hydrogel Sorbent for Rare-Earth-Element Recycling from Aqueous Sources" by Qiuming Wang, Walter C. Wilfong, Brian W. Kail, Yang Yu, and McMahan L. Gray, "ACS Sustainable Chemistry & Engineering," September 14, 2017, Walter Christopher Wilfong, Brian W. Kail, Tracy L. Bank, Bret H. Howard, and McMahan L. Gray, "Recovering Rare Earth Elements from Aqueous Solution with Porous Amine-Epoxy Networks" in "ACS Applied Materials & Interfaces," May 12, 2017, Qiuming Wang, Brian W. Kail, Walter "Amine Sorbents for Selective Recovery of Heavy Rare-Earth Elements (Dysprosium, Ytterbium) from Aqueous Solution" by C. Wilfong, Fan Shi, Thomas J. Tarka, and McMahan L. Gray.These are of the type described by Gray in "ChemPlusChem," 2020, 85 130-136, and "Stable Immobilized Amine Sorbents for Heavy Metal and REE Removal from Industrial Wastewaters," "Environ.Sci:Water Res.Technol.," 2020, 6, 1286. A sample of n-methylethanolamine (NMEA) (a commercially available >99% NMEA pure amine liquid from Dow Chemical Company) is used as the purified target amine liquid for each of these examples.

[0018] Metal concentration analysis is performed by ICP-MS. The Agilent 7900x ICP-MS instrument is equipped with an inert polytetrafluoroethylene (PFA) microflow nebulizer, PFA spray chamber, and quartz sample introduction system to eliminate interference from organic matrix, carrier gas, etc. The 7900 ICP-MS instrument is equipped with an octopole reaction cell (ORC), He and H2 cell gas lines. This system can eliminate polyatomic interference using collision / reaction cell (CRC) technology. The ICP-MS instrument is housed in an ISO Class 100 cleanroom equipped with an ISO Class 100 clean hood. Sample preparation, including weighing, immersion, and analysis, is performed according to clean chemical procedures. Analysis is performed using the Agilent 7900x ICP-MS. The apparatus is equipped with a 200 μL self-aspiration PFA Micro Flow nebulizer, a 1.5 mm inner diameter injector, and a PFA spray chamber with a platinum interface (sampler cone and skimmer cone). To achieve high sensitivity and low background and reduce any polyatomic interference, the ICP-MS instrument is prepared using a 1 ppb preparation solution under gas-free, H2 reaction, and helium collision conditions.

[0019] The chemicals and reagents used in ICP-MS analysis include nitric acid, multi-element standard solutions, and ICP-MS preparation solutions. The nitric acid is Ultra-Trace Metal grade or Optima grade. They are used for sample immersion and for preparing calibration standard solutions and preparation solutions. The instrument is prepared and calibrated under N2 gas, H2 gas, and He gas. The instrument is calibrated over a range of 0–10 ng / mL using calibration standard solutions (SPEX CertiPrep, Multi-element Standards) of 0, 0.25, 1, 5, and 10 ng / mL prepared in 5% nitric acid.

[0020] To analyze metals by ICP-MS, organic matter in amine samples must be removed. This can usually be done by evaporating to dryness at a temperature below the boiling point in a high-temperature block while purging with nitrogen. The residue is then redissolved in nitric acid and diluted with water. The prepared solution is analyzed using inductively coupled plasma-mass spectrometry (ICP-MS) with an Agilent 7900 ICP-MS, as described above.

[0021] Example 1: Batch method As shown in Table 1, five different amounts of the same adsorbent were added to five plastic bottles, respectively. Approximately the same amount of NMEA was added to each bottle. After adding the NMEA solution, the five bottles were placed on a mechanical shaker to shake overnight to promote adsorption equilibrium. After shaking, the adsorbent was allowed to settle in the bottles, and the liquid samples were taken for metal analysis. The original untreated NMEA sample was also analyzed for metal content as a comparative example.

[0022] Table 1 shows the experimental results. As shown in this table, the original NMEA comparative sample had Fe, Cu, and Zn ions at concentrations of 97, 9, and 47 ppb, respectively. For tests 1-5, the amount of NMEA amine liquid was almost the same, and the amount of adsorbent for each test increased from test 1 to test 5. Table 1 shows that the more adsorbent applied, the more metal ions are removed from the liquid NMEA. For example, Fe 3+ Regarding metal ions, in Test 5, after applying 0.816 grams of adsorbent, 4 ppb of Fe was found in NMEA at equilibrium. 3+ Only that remained. In another embodiment, Zn 2+ Regarding this, even after only 0.405 grams of adsorbent were applied in Test 4, only 3 ppb of Zn was present. 2+ It remained in NMEA in equilibrium. In the third embodiment, Cu 2+ Regarding this, in Test 5, after applying 0.816 grams of adsorbent, 2 ppb of Cu was observed. 2+ It remained in NMEA in an equilibrium state.

[0023] As can be understood, when properly designed, adsorbers utilizing this class of adsorbents can provide removal efficiencies exceeding 95% for major metal contaminants such as Fe and Zn, with a good operating life. [Table 1]

[0024] Example 2: Adsorption experiment on a fixed floor The adsorption column is made of polypropylene having a polypropylene frit as a support for an adsorption medium. The amount of superabsorbent packed into the column is 0.985 g, and the volume of the adsorbent bed is 2.85 mL. NMEA is pumped by a liquid chromatography pump (model 626) obtained from Alltech. The pump is constructed from a metal-free PEEK material. A flow rate of 1.0 mL / min (21 bed volumes ("bed volume, BV") per hour) is maintained throughout the entire duration of the adsorption experiment. Comparative samples are collected before and after to ensure that there is no contamination from the pump fittings and tubes. At regular intervals, about 1 to 2 mL samples are collected at the outlet of the column for analytical measurement. The results from the fixed bed adsorption experiment are shown in Table 2. [Table 2]

[0025] The fixed-bed adsorption results indicate that essentially all metallic impurities present in NMEA (comparative example) are adsorbed to some extent by the superadsorbent. Some variation in metal concentration was most likely due to analytical or experimental error. Taking Fe3+ metal ions as an example, when 140 BV NMEA was supplied through the adsorbent column, the Fe3+ concentration in the effluent was 26 ppb, down from 84 ppb in the NMEA feed (comparative example). As another example, taking Cu2+, when 140 BV NMEA was supplied through the adsorbent column, its concentration in the effluent was 2 ppb, down from 16 ppb in the NMEA feed (comparative example). As a third example, taking Zn2+, when 42 BV NMEA was supplied through the adsorbent column, its concentration in the effluent was 3 ppb, down from 158 ppb in the NMEA feed (comparative example). After 42 BV of NMEA is supplied into the column, more Zn2+ begin to slowly pass through the adsorbent bed, as evidenced by the slow increase in Zn2+ concentration as more NMEA is supplied through the column. Superadsorbents have different adsorption capacities for different metals. Therefore, the breakthrough time for each metal in a fixed-bed adsorption column will differ. It should be noted that the results of the examples considered were performed at a supply flow rate of 21 BV per hour. At lower supply flow rates, particularly in the preferred range of 1 to 10 BV per hour, metal removal efficiency will be higher and the metal concentration in the effluent will be lower. The present specification includes the following embodiments. Section 1: A method for removing metal ions present in a mixture containing one or more organic amines, comprising the step of contacting the mixture with a silica-polyethyleneimine adsorbent. Section 2: The method according to claim 1, wherein the polyethyleneimine is linear, branched, or dentrimer-like. Section 3: The method according to claim 1, wherein the metal ions to be removed include at least one of Fe, Zn, Cr, Mn, Co, Ni, Cu, Cd, Li, Na, K, Mg, Ca, Sr, Ba, Al, Pb, and Sb. Section 4: The aforementioned organic amines include monoethanolamine (MEA), diethanolamine (DEA), triethanolamine (TEA), monoisopropanolamine (MIPA), diisopropanolamine (DIPA), triisopropanolamine (TIPA), N-methyldiethanolamine (MDEA), N-methylethanolamine (NMEA), and ethylenediamine. The method according to item 1, selected from the group consisting of e, EDA), piperazine (PIP), diethylenetriamine (DETA), aminoethylethanolamine (AEEA), aminoethylpiperazine (AEP), triethylenetetramine (TETA), tetraethylenepentamine (TEPA), dimethylethanolamine (DMEA), polyethylene polyamine, a mixture of pentaethylenehexamine, and combinations thereof. Section 5: The method according to claim 1, wherein the mixture is passed through a fixed bed of silica-polyethyleneimine adsorbent. Item 6: The method according to item 5, wherein the flow rate of the mixture through the floor is in the range of 1 to 30 BV per hour, where BV is the volume of the floor. Section 7: The method according to claim 6, wherein the flow rate of the mixture through the floor is in the range of 1 to 10 BV per hour. Section 8: The method according to claim 5, wherein the mixture is passed through two or more fixed beds of silica-polyethyleneimine adsorbent, and the two or more beds are arranged in a parallel circuit, a series circuit, or a combination of a parallel circuit and a series circuit. Section 9: The method according to item 8, wherein the two or more floors are arranged in a parallel circuit. Section 10: The method according to claim 1, wherein the silica-polyethyleneimine adsorbent is added to the mixture and mixed. Section 11: The method according to claim 1, wherein the mixture is brought into contact with the silica-polyethyleneimine adsorbent at a temperature ranging from the freezing point of the mixture to just below the boiling point of the mixture. Section 12: The method according to claim 1, wherein the silica-polyethyleneimine adsorbent is washed with water or other solvent(s) before contacting the mixture. Section 13: The method according to claim 12, wherein the silica-polyethyleneimine adsorbent is washed two or more times with water or other solvents. Section 14: The method according to claim 1, wherein the silica-polyethyleneimine adsorbent is periodically regenerated by contacting the adsorbent with a material in which the metal ions have a higher affinity (for example, a weak acid or a weak acid aqueous solution, or a relatively strong amine). Section 15: The method according to claim 14, wherein the contact material is a weak acid and comprises acetic acid, formic acid, hydrocyanic acid, hydrofluoric acid, hydrogen sulfide, trichloroacetic acid, or a mixture thereof. Section 16: The method according to item 14, wherein the contact material is ammonia. Section 17: The method according to claim 7, wherein the volume of the floor is configured to reduce the amount of a specific metal contaminant to a desired level given a desired flow rate. Section 18: The method according to claim 17, wherein the desired level of metal contaminants is less than 10 ppb.

Claims

1. A method for removing metal ions present in a mixture containing one or more organic amines, comprising the step of contacting the mixture with a silica-polyethyleneimine adsorbent.

2. The method according to claim 1, wherein the polyethyleneimine is linear, branched, or dentrimer-like.

3. The method according to claim 1, wherein the metal ions to be removed include at least one of Fe, Zn, Cr, Mn, Co, Ni, Cu, Cd, Li, Na, K, Mg, Ca, Sr, Ba, Al, Pb, and Sb.

4. The organic amines include monoethanolamine (MEA), diethanolamine (DEA), triethanolamine (TEA), monoisopropanolamine (MIPA), diisopropanolamine (DIPA), triisopropanolamine (TIPA), N-methyldiethanolamine (MDEA), N-methylethanolamine (NMEA), and ethylenediamine. The method according to claim 1, wherein a selection is made from the group consisting of , EDA), piperazine (PIP), diethylenetriamine (DETA), aminoethylethanolamine (AEEA), aminoethylpiperazine (AEP), triethylenetetramine (TETA), tetraethylenepentamine (TEPA), dimethylethanolamine (DMEA), polyethylene polyamine, a mixture of pentaethylenehexamine, and combinations thereof.

5. The method according to claim 1, wherein the mixture is passed through a fixed bed of silica-polyethyleneimine adsorbent.

6. The method according to claim 5, wherein the flow rate of the mixture through the fixed bed is in the range of 1 to 30 BV per hour, and BV is the volume of the fixed bed.

7. The method according to claim 6, wherein the flow rate of the mixture passing through the fixed bed is in the range of 1 to 10 BV per hour.

8. The method according to claim 5, wherein the mixture is passed through two or more fixed beds of silica-polyethyleneimine adsorbent, and the two or more fixed beds are arranged in a parallel circuit, a series circuit, or a combination of a parallel circuit and a series circuit.

9. The method according to claim 8, wherein the two or more fixed floors are arranged in a parallel circuit.

10. The method according to claim 1, wherein the silica-polyethyleneimine adsorbent is added to the mixture and mixed.

11. The method according to claim 1, wherein the mixture is brought into contact with the silica-polyethyleneimine adsorbent at a temperature ranging from the freezing point of the mixture to just below the boiling point of the mixture.

12. The method according to claim 1, wherein the silica-polyethyleneimine adsorbent is washed with water or other solvents before contacting the mixture.

13. The method according to claim 12, wherein the silica-polyethyleneimine adsorbent is washed two or more times with water or other solvents (multiple solvents are permitted).

14. The method according to claim 1, wherein the silica-polyethyleneimine adsorbent is periodically regenerated by contacting the silica-polyethyleneimine adsorbent with a material in which the metal ions have a higher affinity.

15. The method according to claim 14, wherein the contact material is a weak acid and comprises acetic acid, formic acid, hydrocyanic acid, hydrofluoric acid, hydrogen sulfide, trichloroacetic acid, or a mixture thereof.

16. The method according to claim 14, wherein the contact material is ammonia.

17. The method according to claim 7, wherein the volume of the fixed bed is configured to reduce the amount of a specific metal ion to a desired level at which a desired flow rate is given.

18. The method according to claim 17, wherein the desired level of the metal ion is less than 10 ppb.

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