Amine triols and process to make them

Abstract

An amine triol is represented by Formula 2: wherein R1 is a lower alkyl group containing from 1 to 4 carbon atoms; R2, R3 and R4 are each independently hydrogen or a lower alkyl moiety; and "n" is a number of repeating –(CR3R4)- units that is at least 1.

Description

[0001] AMINE TRIOLS AND PROCESS TO MAKE THEM FIELD This application relates to alkanolamines and processes to make them. INTRODUCTION Alkanolamines are known and used in many applications. Examples of known alkanolamines include monoethanolamine (MEA), diethanolamine (DEA), triethanolamine (TEA), n-methyl ethanolamine, and many others. They are widely used as chemical reagents and for treating gas streams that contain acid gases. In some processes to remove carbon dioxide from gas streams, the gas stream is contacted with an aqueous stream that contains a primary or secondary alkanolamine. Carbon dioxide dissolves in the aqueous stream and reacts with the alkanolamine to form a carbamate, which stabilizes the carbon dioxide in the aqueous stream. Later, the aqueous stream is subjected to conditions, such as high temperature and low pressure, that decompose the carbamate and desorb the carbon dioxide from the aqueous stream for recovery. Alkanolamines that are used in the process are selected so that they readily form carbamate under the conditions at which carbon dioxide is absorbed, and the carbamate readily decomposes under the conditions at which carbon dioxide is desorbed. A class of 3-amino-1,2-propanediols have been studied for carbon dioxide treatment. They are represented by Formula 1: organic moieties. They are made by reaction of glycidol epoxide with an amine of Formula RR’NH. It is desirable to identify new alkanolamines and processes to make them. SUMMARY One aspect of this invention is an amine triol that is represented by Formula 2: • R1is a lower alkyl group containing from 1 to 4 carbon atoms; • R2, R3and R4are each independently hydrogen or a lower alkyl moiety; and • “n” is a number of independently selected repeating –(CR3R4)- units that is at least 1, or an acid salt of the amine triol. A second aspect of this invention is a process to make an amine triol comprising the step of reacting glycidol with a primary alkanolamine that meets Formula 3 • R1is a lower alkyl group containing from 1 to 4 carbon atoms; • R2, R3and R4are each independently hydrogen or a lower alkyl moiety; and • “n” is a number of independently selected repeating –(CR3R4)- units that is at least 1, under conditions suitable to produce a propanediol moiety bonded to the amine nitrogen of the alkanolamine. The amino triols of this invention are novel compounds that can be used in ordinary uses for alkanolamines; for example, as reagents or as amines in acid-gas recovery. They may be especially useful in carbon dioxide recovery. BRIEF DESCRIPTION OF THE FIGURES Figure 1 shows the results of1H (a) and13C (b) nuclear magnetic resonance (NMR) analysis of products made in Example 2. DETAILED DESCRIPTION This invention begins with a primary alkanolamine, which comprises an alkyl group bonded to both a primary amine group (-NH2) and a hydroxyl group (-OH). The alkanolamine is represented by Formula 3: containing from 1 to 4 carbon atoms; R2, R3and R4are each independently hydrogen or a lower alkyl moiety; and “n” is a number of independently selected repeating –(CR3R4)- units that is at least 1. In some embodiments, R1is lower alkyl and R2is hydrogen. In some embodiments, both R1and R2are lower alkyl. In some embodiments, R1and R2collectively comprise at least 2 carbon atoms or at least 3 carbon atoms or at least 4 carbon atoms or at least 5 carbon atoms or at least 6 carbon atoms. In some embodiments, R1and R2collectively comprise at most 8 carbon atoms or at most 7 carbon atoms or at most 6 carbon atoms or at most 5 carbon atoms or at most 4 carbon atoms. The R3and R4moieties in each repeating –(CR3R4)-unit may be selected independently. In some embodiments, no more than two of the R3and R4moieties are lower alkyl. In some embodiments, no more than one of the R3and R4moieties is lower alkyl. In some embodiments, none of the R3and R4moieties are lower alkyl. In some embodiments, the R3and R4moieties collectively comprise no more than 8 carbon atoms or no more than 7 carbon atoms or no more than 6 carbon atoms or no more than 5 carbon atoms or no more than 4 carbon atoms or no more than 3 carbon atoms or no more than 6 carbon atoms or no more than 1 carbon atom. In some embodiments, the R3and R4moieties collectively comprise 0 carbon atoms. Alkyl groups in R1, R2, R3and R4are each selected from methyl, ethyl, n-propyl, isopropyl, n- butyl, isobutyl or t-butyl groups. In some embodiments, alkyl groups in R1, R2, R3and R4are methyl groups. In some embodiments, alkyl groups in R1, R2, R3and R4are ethyl groups. In some embodiments, alkyl groups in R1, R2, R3and R4are n-propyl groups. In some embodiments, alkyl groups in R1, R2, R3and R4are isopropyl groups. In some embodiments, one or both of R1and R2are isopropyl groups. In some embodiments, one or both of R1and R2are isobutyl groups. “n” is at least 1. In some embodiments, n is on average at most 6 or at most 5 or at most 4 or at most 3 or at most 2 or at most 1. In some embodiments, n is from 1 to 2. High values of n may reduce the solubility of the amine triol product in water, which may reduce its effectiveness in carbon dioxide treatment. The moiety –(CR3R4)n-CR1R2- (called a linking alkylene group) links the amine group to the hydroxyl group and contains at least 3 carbon atoms. In some embodiments, the linking alkylene group contains at least 4 carbon atom or at least 5 carbon atoms. In some embodiments, the linking alkylene group contains at most 10 carbon atoms or at most 9 carbon atoms or at most 8 carbon atoms or at most 7 carbon atoms or most 6 carbon atoms or most 5 carbon atoms or most 4 carbon atoms. For example, the linking alkylene group may contain 3 to 8 carbon atoms or 4 to 6 carbon atoms or 4 carbon atoms. In some embodiments, the primary amine group and the hydroxyl group are bonded to adjacent carbon atoms (n = 1). Examples include 2-amino-1-propanol, 2-amino-1-butananol, 2-amino-2-methyl-1- propanol and 3-amino-3-methyl-2-butanol. In some embodiments, a chain of three carbon atoms lies between the primary amine group and the hydroxyl group (n = 2). Examples include 3-amino-1-butananol and 3-amino-3-methyl-1-butanol. In some embodiments, a chain of four carbon atoms lies between the primary amine group and the hydroxyl group (n = 3). Examples include 4-amino-1-pentanol, 4-amino-1-hexanol and 4-amino-4- methyl-1-pentanol. Suitable alkanolamines are commercially available. Others can be made by known processes such as by reaction of ammonia with an alkylene oxide such as propylene oxide, butylene oxide and substituted variations thereof. The alkanolamine is reacted with glycidol. The reaction proceeds as shown in Formula 4: In some embodiments, an excess of alkanolamine is used in the reaction. The excess of alkanolamine can ensure that glycidol is fully consumed and can reduce potential polymerization of glycidol as a side reaction. In some embodiments, the molar ratio of alkanolamine to glycidol is at least 100% or at least 110% or at least 120% or at least 130% or at least 140% or at least 150% or at least 160% or at least 170% or at least 180% or at least 190% or at least 200%. In some embodiments, the molar ratio of alkanolamine to glycidol is at most 400% or at most 350% or at most 300% or at most 280% or at most 260% or at most 240% or at most 220% or at most 200% or at most 180% or at most 160% or at most 150% or at most 140% or at most 130% or at most 120%. In some embodiments, the alkanolamine is liquid at reaction temperatures and can be used in the reaction without a solvent. In some embodiments, the alkanolamine is solid at reaction temperatures and so it may contain solvent to maintain it as a liquid during the reaction. In some embodiments, the solvent is aqueous, and in some embodiments, the solvent is organic. Examples of organic solvents include ethanol, isopropanol or paraffin that is liquid at reaction temperatures. In some embodiments, the alkanolamine contains at least 1 weight percent solvent or at least 2 weight percent or at least 3 weight percent or at least 4 weight percent or at least 5 weight percent. In some embodiments, the alkanolamine contains at most 10 weight percent solvent or at most 8 weight percent or at most 6 weight percent or at most 5 weight percent. In some embodiments, excess alkanolamine (with solvent to keep it liquid) serves as a solvent for the reaction and no other solvent is needed, In some embodiments, the reaction takes place in a solvent. In some embodiments, the solvent comprises an organic solvent as previously described. In some embodiments, the solvent comprises an aqueous solvent, such as water or a mixture of water and a water miscible organic solvent. In some embodiments, the solvent is water. In some embodiments, the solvent is deionized water. In some embodiments, the reaction is carried out at a temperature of at least 50℃ or at least 60℃ or at least 65℃ or at least 70℃ or at least 75℃ or at least 80℃ or at least 85℃. In some embodiments, the reaction is carried out at a temperature of at most 120℃ or at most 110℃ or at most 100℃ or at most 95℃ or at most 90℃. Pressure is not critical as long as the reaction mixture remains stable and liquid. In some embodiments, the pressure is atmospheric pressure. In some embodiments, pressure above atmospheric pressure may permit higher reaction temperatures. In some embodiments, the reaction is complete when all glycidol has been reacted. After the reaction is complete, solvent and excess reagents may be distilled to recover the amine triol product. The resulting product is an amine triol that meets Formula 2. “n” are as already described. The description and embodiments of the linking alkylene group [–(CR3R4)n-CR1R2-] are as already described. The amine triol has a molecular weight of at least 148 g / mol. In some embodiments, the amine triol has a molecular weight of at least 160 g / mol or at least 170 g / mol or at least 180 g / mol or at least 190 g / mol or at least 200 g / mol. In some embodiments, the amine triol has a molecular weight of at most 305 g / mol or at most 280 g / mol or at most 250 g / mol or at most 235 g / mol or at most 220 g / mol or at most 200 g / mol or at most 180 g / mol or at most 165 g / mol. In some embodiments, the amine triol has a pKa at 25℃ of at least 8.5 or at least 8.7 or at least 8.9 or at least 9.0 or at least 9.2 or at least 9.4 or at least 9.5 or at least 9.6 or at least 9.7. In some embodiments, the amine triol has a pKa at 25℃ of at most 11 or at most 10.8 or at most 10.6 or at most 10.5 or at most 10.4 or at most 10.2 or at most 10.0 or at most 9.8. In some embodiments, the amine triol has a vapor pressure at 175℃ and atmospheric pressure of at least 1.0 mm Hg or at least 1.5 mm Hg or at least 2.0 mm Hg or at least 2.2 mm Hg or at least 2.4 mm Hg. In some embodiments, the amine triol has a vapor pressure at 175℃ and atmospheric pressure of at most 5.0 mm Hg or at most 4.0 mm Hg or at most 3.0 mm Hg or at most 2.8 mm Hg or at most 2.6 mm Hg. In some embodiments, the amine triol has a vapor pressure at 198℃ and atmospheric pressure of at least 5 mm Hg or at least 6 mm Hg or at least 7 mm Hg or at least 8 mm Hg or at least 9 mm Hg or at least 10 mm Hg. In some embodiments, the amine triol has a vapor pressure at 198℃ and atmospheric pressure of at most 20 mm Hg or at most 18 mm Hg or at most 16 mm Hg or at most 14 mm Hg or at most 12 mm Hg or at most 10 mm Hg. In some embodiments, the amine triol has a melting point of at least 50℃ or at least 55℃ or at least 60℃ or at least 65℃ or at least 70℃ or at least 75℃. In some embodiments, the amine triol has a melting point of at most 100℃ or at most 95℃ or at most 90℃ or at most 85℃ or at most 80℃. In some embodiments, the amine triol has a boiling point of at least 250℃ or at least 260℃ or at least 270℃ or at least 280℃ or at least 290℃ or at least 295℃. In some embodiments, the amine triol has a boiling point of at most 350℃ or at most 340℃ or at most 330℃ or at most 320℃ or at most 310℃ or at most 300℃. Examples of compounds within this invention include: • 3-[(2-hydroxy-1,1-dimethyl-ethyl)amino]-1,2-propanediol; • 3-[(3-hydroxy-1,1-dimethyl-n-propyl)amino]-1,2-propanediol; • 3-[(2-hydroxy-1,1-diethylethyl)amino]-1,2-propanediol; • 3-[(2-hydroxy-1-ethylethyl)amino]-1,2-propanediol; • 3-[(2-hydroxy-1-isopropylethyl)amino]-1,2-propanediol; • 3-[(2-hydroxy-1,1-diethylpropyl)amino]-1,2-propanediol; • 3-[(2-hydroxy-1-ethylpropyl)amino]-1,2-propanediol; and • 3-[(2-hydroxy-1-isoproylpropyl)amino]-1,2-propanediol The amine triols can be used for ordinary purposes that alkanolamines are used, as previously described. In some embodiments, the amine triol may be reacted with an organic or inorganic acid to make an acid salt. Examples of inorganic acids include hydrochloric acid, sulfuric acid, sulfonic acid and nitric acid. Examples of organic acids include acetic acid, propionic acid, butanoic acid, formic acid, lactic acid, glycolic acid, oxalic acid and citric acid. Acids salts of the amine triol are within the scope of this invention.

[0002] Test Methods Unless stated otherwise, measurements listed in this application are made using the following test methods: Parameter Test Vapor Pressure ASTM E1719 o s n Examples The following examples illustrate specific embodiments of the invention, but do not limit the broadest scope of the invention. The materials in Table 1 are used for the Examples: Table 1 Name Ingredient AMP (99%) 99% purity 2-amino-2-methyl-1-propanol (AMP, CAS 124-68-5). ac uired from Thermo Fisher . . A 2-necked round-bottom flask is mounted in a water bath on a hot plate with a magnetic stirrer. One neck of the flask is connected to a nitrogen source. One neck is capped with a rubber septum that admits a temperature probe connected to a temperature controller for the hot plate. A second temperature probe measures the temperature of the water bath. A mixture of 8.58 mL of AMP (99%) in 32 mL of DI water is heated to 70°C in the flask while stirring under nitrogen atmosphere. Maintaining the temperature at 70 °C, 3.00 mL of glycidol is added in increments over a ~60-min period. The temperature, nitrogen atmosphere and stirring are maintained until GC analysis of samples shows that all the glycidol had been reacted. The excess starting material (i.e., AMP) and water is removed in batches using a simple distillation. The crude mixture is heated between 150-160 °C, while nitrogen is bubbled into the round bottom flask to help remove the AMP starting material. The batch distillation is considered complete once ≤0.5 wt% AMP (by GC-FID area count) is present in the purified AMPPD. The AMPPD that is recovered has the following properties: • pKa: 9.77 at 25℃, • Melting Point: 77℃; • Boiling point: > 250℃ Preparation of 3-[(2-hydroxy-1,1-dimethylethyl)amino]-1,2-propanediol A 40.49 mol sample of AMP (95%) is charged to a 5-gallon reactor and heated to 100 °C. A 19.68 mol sample of glycidol is fed into the reactor at a rate of ~5 g / min for 2 h. Once fed, the mixture is digested for 3.5 h. An aliquot of the reaction mixture is taken for GC analysis to ensure all the glycidol had been reacted. The excess starting material (i.e., AMP) and water is removed by distillation as described in the previous example. Approximately 4825 g of the AMPPD mixture is recovered (i.e., 95.2% recovery, based on the amount a glycidol added). The identity of the product is confirmed by1H and13C NMR analysis, shown in Figure 1.

Claims

CLAIMS: We claim:

1. An amine triol that is represented by Formula 2:atoms; R2, R3and R4are each independently hydrogen or a lower alkyl moiety; and “n” is a number of independently selected repeating –(CR3R4)- units that is at least 1, or an acid salt of the amine triol.

2. The amine triol or acid salt of Claim 1 wherein R1and R2collectively comprise from 3 to 6 carbon atoms.

3. The amine triol or acid salt of Claim 1 wherein the R3and R4moieties collectively comprise from 0 to 6 carbon atoms.

4. The amine triol or acid salt of Claim 1 wherein all R3and R4moieties are hydrogen.

5. The amine triol or acid salt of Claim 1 wherein the molecular weight of the amine triol is from 148 g / mol to 305 g / mol.

6. The amine triol or acid salt of Claim 1 wherein the molecular weight of the amine triol is at least 160 g / mol.

7. The amine triol or acid salt of Claim 6 wherein the molecular weight of the amine triol is at most 250 g / mol.

8. The amine triol or acid salt of Claim 7 wherein both of R1and R2are alkyl groups.

9. The amine triol or acid salt of any one of Claims 1 through 8 wherein n is from 1 to 3.

10. The amine triol or acid salt of Claim 9 wherein n is 1.

11. The amine trio or acid salt of Claim 9 wherein the amine triol has a pKa at 25℃ from 8.5 to 10.

5.

12. The amine trio or acid salt of Claim 9 wherein the amine triol has a vapor pressure at 175℃ and atmospheric pressure from 1.0 mm Hg to 4.0 mm Hg.

13. The amine trio or acid salt of Claim 9 wherein the amine triol has a vapor pressure at 198℃ and atmospheric pressure from 5 mm Hg to 15 mm Hg.

14. The amine triol or acid salt of Claim 1 wherein the amine triol is any one of: 3-[(2-hydroxy-1,1- dimethylethyl)amino]-1,2-propanediol; 3-[(3-hydroxy-1,1-dimethyl-n-propyl)amino]-1,2- propanediol; 3-[(2-hydroxy-1,1-diethylethyl)amino]-1,2-propanediol; 3-[(2-hydroxy-1- ethylethyl)amino]-1,2-propanediol; 3-[(2-hydroxy-1-isopropylethyl)amino]-1,2-propanediol; 3-[(2-hydroxy-1,1-diethylpropyl)amino]-1,2-propanediol; 3-[(2-hydroxy-1-ethylpropyl)amino]- 1,2-propanediol; and 3-[(2-hydroxy-1-isoproylpropyl)amino]-1,2-propanediol.

5. A process to make an amine triol comprising the step of reacting glycidol with a primary alkanolamine that meets Formula 3:containing from 1 to 4 carbon atoms; R2, R3and R4are each independently hydrogen or a lower alkyl moiety; and “n” is a number of independently selected repeating –(CR3R4)- units that is at least 1, under conditions suitable to produce a propanediol moiety bonded to the amine nitrogen of the alkanolamine.

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