Method for removing acid gases from fluid streams - Patents.com

Abstract

1. A method for removing acid gases from a fluid stream, comprising contacting the fluid stream with an absorbent to obtain a treated fluid stream and an absorbed absorbent, the absorbent comprising at least one diluent and a compound of general formula (I): wherein R1 is C1-C3-alkyl, R2 is C1-C3-alkyl, R3 is selected from hydrogen and C1-C3-alkyl, R4 is selected from hydrogen and C1-C3-alkyl, and n is an integer ranging from 1 to 4. TIFF2022547299000012.tif37161

Description

[Technical Field]

[0001] FIELD OF THE INVENTION The present invention relates to the use of absorbents and methods for removing acid gases from fluid streams. In one embodiment, the present invention relates to the selective removal of hydrogen sulfide from a fluid stream containing carbon dioxide and hydrogen sulfide. [Background technology]

[0002] The removal of acid gases, such as CO2, H2S, SO2, CS2, HCN, COS, or mercaptans, from fluid streams, such as natural gas, refinery gas, or synthesis gas, is desirable for various reasons. Sulfur compounds in natural gas tend to form corrosive acids, especially with the water that often accompanies natural gas. During the transportation of natural gas in pipelines or its further processing in natural gas liquefaction plants (LNG = liquefied natural gas), certain restrictions on sulfur-containing impurities must therefore be observed. Furthermore, many sulfur compounds are odorous and toxic even at low concentrations.

[0003] Carbon dioxide must be removed from natural gas because high concentrations of CO2 reduce the heating value of the gas. Additionally, CO2, along with humidity, can cause corrosion of pipes and valves.

[0004] Known methods for removing acid gases include scrubbing with an aqueous absorbent solution of an inorganic or organic base. When acid gases are dissolved in the absorbent, ions are generated along with the base. The absorbent can be regenerated by depressurization to a lower pressure and / or stripping, whereby the ionic species react back and the acid gases are released, and / or stripped with an inert fluid, e.g., steam. After the regeneration process, the absorbent can be reused.

[0005] A process in which CO2 and H2S are substantially removed is called "total absorption." While CO2 removal can be essential to avoid corrosion problems and provide the necessary heating value for consumers, it is sometimes necessary or desirable to treat acid gas mixtures containing both CO2 and H2S in a manner that selectively removes H2S from the mixture while minimizing CO2 removal. Natural gas pipeline specifications, for example, impose stricter constraints on H2S levels than CO2 because H2S is more toxic and corrosive than CO2. Conventional natural carrier gas pipeline specifications typically limit H2S content to 4 ppmv, with a more relaxed constraint on CO2 at 2 vol%. Selective H2S removal is often desirable for sulfur recovery, e.g., to increase H2S levels in the feedstream to a downstream Claus plant.

[0006] Highly sterically hindered secondary amines, such as 2-(2-tertbutylaminoethoxy)ethanol (TBAEE) and tertiary amines, such as methyldiethanolamine (MDEA), exhibit kinetic selectivity for HS over CO. Such amines are therefore suitable for selective removal of HS over CO from gas mixtures containing CO and HS, typically utilized as aqueous mixtures. These amines do not react directly with CO; instead, CO reacts with the amine and water in a slow reaction to yield bicarbonate ions. Depending on the reaction kinetics, HS can react more rapidly directly with the amine groups on the sorbent to form hydrosulfide ions in aqueous solution.

[0007] The use of hydroxyl-substituted amines (alkanolamines), such as those mentioned above, has become common because the presence of the hydroxyl group tends to improve the solubility of the absorbent and its acid gas reaction products in widely used aqueous solvent systems, thereby facilitating solvent circulation through conventional absorber / regenerator units by suppressing phase separation. The presence of the hydroxyl group can also reduce the volatility of the amine, thereby reducing amine losses during operation.

[0008] However, this preference can present its own problems in certain situations. Although alkanolamines efficiently remove acid gases at high pressures, selectivity for HS removal can be expected to decrease significantly due to both direct physical absorption of CO in the liquid solvent and reaction with the hydroxyl groups of the amine compounds. CO preferentially reacts with the amino nitrogen, but high pressure forces it to react with oxygen. At high pressures, the bicarbonate / hemicarbonate / carbonate reaction products formed by reaction at the hydroxyl sites stabilize and progressively lose HS selectivity with increasing pressure.

[0009] Furthermore, although the presence of hydroxyl groups improves the water solubility of the amine, the hydroxyl groups tend to impart surfactant properties to the absorbent / acid gas reaction products, thereby potentially causing troublesome foaming during operation of the gas processing unit.

[0010] Another known problem with using aqueous amine mixtures in the absorption treatment of gas mixtures is that separation into several phases can occur at temperatures that are within the range of regeneration temperatures for aqueous amine mixtures, typically in the range of 50°C to 170°C.

[0011] US 4,487,967, US 4,665,195 and US 4,894,178 relate to a process for preparing sterically hindered aminoether alcohols or diaminopolyalkylene ethers in the presence of a hydrogenation catalyst.

[0012] US2015 / 0027055 describes a method for selectively removing H2S from CO2-containing gas mixtures using an absorbent containing a sterically hindered, terminally etherified alkanolamine. It was found that terminal etherification of the alkanolamine and elimination of water can result in higher H2S selectivity.

[0013] US2010 / 0037775 describes an acid gas absorbent comprising an alkylaminoalkyloxy(alcohol) monoalkyl ether, and a method for selectively removing H2S from a gaseous mixture containing H2S and CO2 using an absorbent solution comprising said monoalkyl ether.

[0014] WO2013 / 181245 describes an absorbent composition useful for the selective removal of H2S, the absorbent composition comprising an aqueous amine mixture of an aminated reaction product of tert-butylamine and a polyethylene glycol mixture, and an organic co-solvent selected from sulfones, sulfone derivatives and sulfoxides, and a strong acid that inhibits phase separation.

[0015] WO 2014 / 001664 discloses absorbent solutions made of tertiary diamines belonging to the hindered aminoethylmorpholine family, which contain only tertiary amino groups, each of which is characterized by a basic nitrogen atom.

[0016] US2013 / 011314 describes compounds containing one or more diamines in which the two amine functions are not connected to each other by a ring, the amine function at the α-position is always tertiary, and the amine function at the ω-position is always primary or secondary, and the use of such compounds in the selective removal of HS from a gas containing HS and CO. The compounds described therein are characterized by secondary and tertiary amino groups, both of which are characterized by a basic nitrogen atom.

[0017] WO2017 / 186466 discloses a method for removing acid gases from fluid streams using morpholine-based hindered amine compounds.

[0018] WO2018 / 146233 describes a method for removing acid gases from a fluid stream obtained from the reaction of a glycidol derivative with a sterically hindered amine, such as tert-butylamine.

[0019] WO2019 / 043099 is directed to absorbent solutions derived from the reaction of tert-butylamine with hydroxyethylpyrrolidone, and structurally related compounds, and their use in gas treatment.

[0020] US2017 / 0320008 describes a mixture of an amine, water and at least one C 1~4 -thioalcohol-containing absorbent. 2 A method for selectively removing H2S from a gaseous mixture containing both S and CO2 is disclosed. The disclosed method has high selectivity for H2S removal and also allows for improved removal of other sulfur components, particularly mercaptans. Summary of the Invention [Problem to be solved by the invention]

[0021] It is an object of the present invention to provide a further method suitable for removing acid gases from fluid streams. The method is useful for total absorption applications in which CO2 and H2S are substantially removed, as well as for selectively removing hydrogen sulfide from fluid streams. The absorbent used in the method has high cycleability and low volatility. A further object of the present invention was to provide a gas treatment method based on a solvent with improved thermal stability, which allows it to operate at high temperatures for longer periods of time. A further object of the present invention was to provide a gas treatment method having high selectivity for the removal of H2S from a gaseous mixture containing both H2S and CO2, which also allows the removal of other sulfur components that may additionally be contained in the gaseous mixture containing both H2S and CO2. In particular, the method of the present invention should also allow the removal of mercaptans in such a selective gas treatment process. [Means for solving the problem]

[0022] The purpose is A method for removing acid gases from a fluid stream, comprising contacting the fluid stream with an absorbent to obtain a treated fluid stream and an absorbed absorbent, the absorbent comprising at least one diluent and a compound represented by general formula (I):

[0023] [ka] wherein R1 is C1-C3-alkyl, R2 is C1-C3-alkyl, R3 is selected from hydrogen and C1-C3-alkyl, R4 is selected from hydrogen and C1-C3-alkyl, and n is an integer ranging from 1 to 4.

[0024] The compounds of general formula (I) are based on thiodiglycol and its derivatives and contain a thioether functionality. It has been surprisingly found that, compared to prior art gassing solvents containing oxy-ether functionality, gassing methods using solvents containing compounds of formula (I) exhibit higher thermal stability while maintaining favorable absorption properties. [Brief explanation of the drawings]

[0025] [Figure 1] The pKa values ​​of TBAESE and TBAEE are shown below. DETAILED DESCRIPTION OF THE INVENTION

[0026] Absorbent: The process according to the invention is carried out in the presence of an absorbent, which comprises a compound of formula (I) and at least one diluent.

[0027] Compounds of formula (I): The absorbent comprises a compound of formula (I).

[0028] In formula (I), R1 is C1-C3-alkyl, preferably methyl, ethyl, propyl and isopropyl, most preferably methyl; R2 is C1-C3-alkyl, preferably methyl, ethyl, propyl and isopropyl, most preferably methyl; R3 is selected from hydrogen and C1-C3-alkyl, preferably methyl, ethyl, propyl and isopropyl, most preferably methyl; R4 is selected from hydrogen and C1-C3-alkyl, preferably methyl, ethyl, propyl and isopropyl, most preferably methyl; n is an integer ranging from 1 to 4, preferably 1 or 2, most preferably 1.

[0029] In a preferred embodiment, R1 and R2 are methyl and R3 is hydrogen, or R1, R2 and R3 are methyl, or R1 and R2 are methyl and R3 is ethyl. In a particularly preferred embodiment, R1, R2 and R3 are methyl.

[0030] In a preferred embodiment, the compound of general formula (I) is 2-[2-(tert-butylamino)ethylsulfanyl]ethanol, or N-[2-(2-methoxyethylsulfanyl)ethyl]-2-methyl-propan-2-amine, or N-[2-(2-ethoxyethylsulfanyl)ethyl]-2-methyl-propan-2-amine, or 2-[2-(isopropylamino)ethylsulfanyl]ethanol, or N-[2-(2-methoxyethylsulfanyl)ethyl]propan-2-amine, or N-[2-(2-ethoxyethylsulfanyl)ethyl]propan-2-amine.

[0031] In a most preferred embodiment, the compound of general formula (I) is 2-[2-(tert-butylamino)ethylsulfanyl]ethanol.

[0032] The absorbent preferably comprises from 10% to 70% by weight, more preferably from 15% to 65% by weight, most preferably from 20% to 60% by weight of a compound of general formula (I) relative to the total weight of the absorbent.

[0033] Synthesis of compounds of formula (I): Compounds of formula (I) are commercially available or can be prepared by a variety of means.

[0034] In a preferred embodiment, the compound of formula (I) is of formula (II)

[0035] [ka] in which R1 is C1-C3-alkyl, R2 is C1-C3-alkyl, and R3 is selected from hydrogen and C1-C3-alkyl Formula (III)

[0036] [ka] wherein R4 is selected from hydrogen and C1-C3-alkyl, and n is an integer ranging from 1 to 4, with an alcohol of the formula (I), in the liquid phase and in the presence of a catalyst.

[0037] Preferably, the amine of formula (II) is tert-butylamine or isopropylamine. Most preferably, the amine of formula (II) is tert-butylamine.

[0038] The alcohol of formula (III) is preferably 2-(2-hydroxyethylsulfanyl)ethanol (thiodiglycol), or 2-(2-methoxyethylsulfanyl)ethanol, or 2-(2-ethoxyethylsulfanyl)ethanol.

[0039] In a most preferred embodiment, the amine of formula (II) is tert-butylamine and the alcohol of formula (III) is thiodiglycol.

[0040] In a further embodiment, n is equal to 3 or 4 and R4 is methyl.

[0041] Preferably, the molar ratio of the amine of formula (II) to the alcohol of formula (III) ranges from 0.8:1 to 1.2:1, more preferably from 0.9:1 to 1.1:1, most preferably 1:1.

[0042] Preferably, the reaction is carried out in the presence of a hydrogenation / dehydrogenation catalyst.

[0043] The catalyst may in principle comprise nickel, cobalt, iron, copper, chromium, manganese, copper, molybdenum, tungsten and / or other metals of groups 8 and / or 9 and / or 10 and / or 11 of the periodic table of the elements.

[0044] It is preferred to use a catalyst comprising at least one metal selected from the group consisting of Cu, Co, Ni, Pd, Pt, Ru, Rh, Ag, Au, Re and Ir.

[0045] It is more preferable to use a catalyst containing at least one metal selected from the group consisting of Cu, Co, Ni, Pd, Pt and Ru.

[0046] The catalysts mentioned above may be doped in the usual way with promoters, for example with chromium, iron, cobalt, manganese, molybdenum, titanium, tin, metals of the alkali metal group, metals of the alkaline earth metal group and / or phosphorus.

[0047] The catalyst may be a supported or unsupported catalyst.

[0048] Suitable support materials are carbon compounds, such as graphite, carbon black and / or activated carbon, aluminum oxide (gamma, delta, theta, alpha, kappa, chi or mixtures thereof), silicon dioxide, zirconium dioxide, zeolites, aluminosilicates or mixtures thereof.

[0049] In a preferred embodiment of the present invention, a Raney-type catalyst is used.

[0050] As Raney catalysts, Raney cobalt catalysts, Raney nickel catalysts and / or Raney copper catalysts are preferably used, with Raney cobalt catalysts being particularly preferred.

[0051] In a further preferred embodiment of the present invention, the catalyst is prepared by reduction of a catalyst precursor in which the aforementioned metals are present in the form of oxygen-containing compounds, such as their oxides, carbonates or bicarbonates.

[0052] The catalyst precursors can be prepared by known methods, for example by precipitation, precipitative application or impregnation.

[0053] In a particularly preferred embodiment, a supported copper, nickel and cobalt-containing hydrogenation / dehydrogenation catalyst is used, the catalytically active material of which, prior to its reduction with hydrogen, comprises oxygen compounds of aluminum, copper, nickel and cobalt, and oxygen compounds of tin in the range of 0.2 to 5.0 wt. %, calculated as SnO. In a preferred embodiment, a catalyst according to the catalyst claimed in WO 2011 / 067199 is used.

[0054] In a preferred embodiment, the reaction is carried out at a temperature of 150 to 260° C. In an especially preferred embodiment, the reaction is carried out at a temperature of 170 to 240° C. In a most preferred embodiment, the reaction is carried out at a temperature of 180 to 220° C.

[0055] The reaction may be carried out at a pressure of 5 to 300 bar. In a preferred embodiment, the reaction is carried out at a pressure of 50 to 200 bar (absolute). In a particularly preferred embodiment, the reaction is carried out at a pressure of 60 to 130 bar (absolute).

[0056] The conversion of the amine of formula (II) and the alcohol of formula (III) is preferably carried out in the liquid phase. Within the meaning of the present invention, the conversion is carried out in the liquid phase if the amine of formula (II), the alcohol of formula (III) or the solvent is in the liquid phase under the conditions of the reaction.

[0057] The conversion is preferably carried out in the presence of hydrogen. Hydrogen is not consumed during the reaction, but has a beneficial effect on maintaining the activity of the catalyst. The partial pressure of hydrogen is preferably in the range of 2.5 to 200 bar, more preferably in the range of 5 to 150 bar, even more preferably in the range of 10 to 100 bar, and most preferably in the range of 20 to 50 bar.

[0058] The conversion can be carried out in the presence of a solvent. The solvent used can be any solvent that is inert under the reaction conditions and has sufficient solubility for the reactants and reaction products. Useful solvents do not contain functional groups, such as hydroxyl groups, that can react with the amine of formula (II) under the conditions of the amination reaction. Preferably, the one or more solvents are water, ethers, preferably methyl tert-butyl ether, ethyl tert-butyl ether, dioxane, tetrahydrofuran (THF), proglyme, diglyme, polyglymes, generally diethers of oligo- and polypropylene oxides, and oligo- and polyethylene oxides, or mixed oligo- or polyalkylene oxides.

[0059] Useful solvents also include suitable mixtures of the solvents listed above.

[0060] Particularly preferred solvents are glyme, THF and water.

[0061] The amount of solvent present in the reaction mixture is typically in the range of 1 to 95% by weight, preferably 2.5 to 70%, more preferably 5 to 40%, based on the total weight of the reaction mixture, the total weight of the reaction mixture being composed of the sum of the masses of all components added to the conversion of the amine of formula (II), i.e., the amine of formula (II), and the alcohol of formula (III), and the solvent.

[0062] The reaction can be carried out using stirred tank reactors, fixed bed tubular reactors, and multi-tubular reactors. It can be carried out in batch, semi-batch, and continuous modes, with or without recycle of the crude reaction mixture. In a preferred embodiment, the reaction is carried out in a continuous mode in a fixed bed tubular reactor.

[0063] The catalyst loading may vary from 0.01 to 2 kg / (L·h) of ether of formula (II), preferably from 0.1 to 1.0 kg / (L·h), and in a particularly preferred embodiment from 0.2 to 0.8 kg / (L·h).

[0064] The reaction product comprises unreacted amine of formula (II), alcohol of formula (III), and compound of formula (III).

[0065] The reaction product is preferably purified by carrying out one or more distillation steps.

[0066] On a laboratory scale, the compound of formula (I) can be converted to the compound of formula (IV)

[0067] [ka] wherein R4 is selected from hydrogen and C1-C3-alkyl; n is an integer ranging from 1 to 4 and 2-chloro-N-tert-butylethylamine hydrochloride in the presence of sodium ethanolate.

[0068] In a typical laboratory synthesis, the compound of formula (IV) is dissolved in a 10 wt.-% solution of sodium methylate in ethanol. 2-Chloro-N-tert-butylethylamine is usually added as a 5 to 10 wt.-% solution in ethanol. Mixing is usually carried out in such a way that the temperature of the resulting mixture is maintained in the range of 35 to 40°C. To complete the reaction, the resulting reaction mixture is typically stirred at 75°C for 90 minutes and at room temperature for an additional 6 to 12 hours.

[0069] Preferably, the reaction is carried out under inert conditions, such as under a nitrogen atmosphere, using a dry solvent. The resulting suspension is typically filtered through a laboratory filter, and the filtrate is evaporated on a rotary evaporator to remove the ethanol and yield the desired product.

[0070] Diluent: The compound of general formula (I) is diluted with a diluent, preferably a low-cost diluent. The diluent can be one that only has physical absorption capacity for carbon dioxide and other components of the gas, such as H2S. Preferably, however, the diluent interacts with the acid-base chemistry of the process. In particular, the diluent is an aqueous diluent. Due to its steric hindrance, the compound of general formula (I) does not have an amine site sufficiently nucleophilic for direct nucleophilic attack on the CO2 molecule. Thus, the oxygen of water acts as a nucleophile to form a Brønsted acid, H2CO3, which is neutralized by the compound of general formula (I) acting as a Brønsted base to form ammonium bicarbonate.

[0071] In the most preferred embodiment, the diluent is water.

[0072] Activator: In a preferred embodiment, the absorbent comprises at least one activator selected from sterically unhindered primary amines and / or sterically unhindered secondary amines. A sterically unhindered primary amine is understood to mean a compound having primary amino groups bound only to primary or secondary carbon atoms. A sterically unhindered secondary amine is understood to mean a compound having secondary amino groups bound only to primary carbon atoms. A sterically unhindered primary amine or a sterically unhindered secondary amine acts as a strong activator for CO2 absorption. The presence of an activator may therefore be desirable in applications aimed at the non-selective removal of acid gases or in applications where CO2 removal is particularly important.

[0073] The activator preferably does not contain acidic groups, such as in particular phosphonic acid, sulfonic acid and / or carboxylic acid groups.

[0074] Activators include, for example: Alkanolamines, such as monoethanolamine (MEA), diethanolamine (DEA), ethylaminoethanol, 1-amino-2-methylpropan-2-ol, 2-amino-1-butanol, 2-(2-aminoethoxy)ethanol and 2-(2-aminoethoxy)ethanamine, Polyamines, such as hexamethylenediamine, 1,4-diaminobutane, 1,3-diaminopropane, 3-(methylamino)propylamine (MAPA), N-(2-hydroxyethyl)ethylenediamine, 3-(dimethylamino)propylamine (DMAPA), 3-(diethylamino)propylamine, N,N'-bis(2-hydroxyethyl)ethylenediamine, 5-, 6- or 7-membered saturated heterocycles having at least one NH group in the ring and which may contain one or two further heteroatoms selected from nitrogen and oxygen in the ring, such as piperazine, 2-methylpiperazine, N-methylpiperazine, N-ethylpiperazine, N-(2-hydroxyethyl)piperazine, N-(2-aminoethyl)piperazine, homopiperazine, piperidine and morpholine.

[0075] Particularly preferred are 5-, 6- or 7-membered saturated heterocycles which contain at least one NH group in the ring and which may contain one or two further heteroatoms selected from nitrogen and oxygen in the ring. Piperazine is very particularly preferred.

[0076] In this preferred embodiment in which the absorbent comprises an activator, the absorbent preferably comprises from 10% to 70% by weight of the activator, more preferably from 15% to 65% by weight, and most preferably from 20% to 60% by weight.

[0077] Lack of sterically unhindered amines In another preferred embodiment, the absorbent is free of any sterically unhindered primary amines or sterically unhindered secondary amines. Because sterically unhindered primary amines or sterically unhindered secondary amines act as strong activators of CO absorption, their presence in the absorbent can cause the absorbent to lose its HS selectivity. Therefore, in applications where high HS selectivity is desired, an absorbent essentially free of such compounds is preferred.

[0078] Additional sterically hindered amines In one embodiment, the absorbent comprises, in addition to the compound of general formula (I), a tertiary amine or a highly sterically hindered primary amine and / or a highly sterically hindered secondary amine. Highly sterically hindered is understood to mean a tertiary carbon atom directly adjacent to a primary or secondary nitrogen atom. In this embodiment, the absorbent comprises the tertiary amine or the highly sterically hindered amine, in addition to the compound of general formula (I), in an amount generally of 5 to 50% by weight, preferably 10 to 40% by weight, more preferably 20 to 40% by weight, relative to the total weight of the absorbent.

[0079] 1. Tertiary alkanolamines, e.g. Bis(2-hydroxyethyl)methylamine (methyldiethanolamine, MDEA), tris(2-hydroxyethyl)amine (triethanolamine, TEA), tributanolamine, 2-diethylaminoethanol (diethylethanolamine, DEEA), 2-dimethylaminoethanol (dimethylethanolamine, DMEA), 3-dimethylamino-1-propanol (N,N-dimethylpropanolamine), 3-diethylamino-1-propanol, 2-diisopropylaminoethanol (DIEA), N,N-bis(2-hydroxypropyl)methylamine (methyldiisopropanolamine, MDIPA), 2. Tertiary amino ethers, e.g. 3-methoxypropyldimethylamine, 3. Tertiary polyamines, such as bis-tertiary diamines, e.g. N,N,N',N'-Tetramethylethylenediamine, N,N-Diethyl-N',N'-dimethylethylenediamine, N,N,N',N'-Tetraethylethylenediamine, N,N,N',N'-Tetramethyl-1,3-propanediamine (TMPDA), N,N,N',N'-Tetraethyl-1,3-propanediamine (TEPDA), N,N,N',N'-Tetramethyl-1,6-hexanediamine, N,N-Dimethyl-N',N'-diethylethylenediamine (DMDEEDA), 1-Dimethylamino-2-dimethylaminoethoxyethane (bis[2-(dimethylamino)ethyl]ether), 1,4-Diazabicyclo[2.2.2]octane (TEDA), Tetramethyl-1,6-hexanediamine and mixtures thereof.

[0080] Tertiary alkanolamines, i.e., amines having at least one hydroxyalkyl group attached to a nitrogen atom, are generally preferred, with methyldiethanolamine (MDEA) being especially preferred.

[0081] Besides the compounds of general formula (I), suitable highly sterically hindered amines (i.e. amines having a tertiary carbon atom directly adjacent to a primary or secondary nitrogen atom) are, inter alia, 1. Highly sterically hindered secondary alkanolamines, e.g. 2-(2-tert-butylaminoethoxy)ethanol (TBAEE), 2-(2-tert-butylamino)propoxyethanol, 2-(2-tert-amylaminoethoxy)ethanol, 2-(2-(1-methyl-1-ethylpropylamino)ethoxy)ethanol, 2-(tert-butylamino)ethanol, 2-tert-butylamino-1-propanol, 3-tert-butylamino-1-propanol, 3-tert-butylamino-1-butanol, and 3-aza-2,2-dimethylhexane-1,6-diol, 2. Highly sterically hindered primary alkanolamines, e.g. 2-amino-2-methylpropanol (2-AMP), 2-amino-2-ethylpropanol and 2-amino-2-propylpropanol, 3. Highly sterically hindered amino ethers, e.g. 1,2-bis(tert-butylaminoethoxy)ethane, bis(tert-butylaminoethyl) ether, and mixtures thereof.

[0082] Highly sterically hindered secondary alkanolamines are generally preferred.

[0083] 2-(2-tert-butylaminoethoxy)ethanol and 2-N-methylamino-2-methylpropan-1-ol are particularly preferred.

[0084] acid: In another preferred embodiment, the absorbent is an aqueous absorbent (meaning that the diluent comprises water), and the absorbent additionally comprises an acid.

[0085] The acid helps regenerate the absorbent, reducing loading and improving process efficiency. A protonation equilibrium occurs between the acid and the compound of general formula (I). The position of the equilibrium is temperature dependent, with the equilibrium shifting toward free oxonium ions and / or amine salts with lower protonation enthalpies at higher temperatures. At the relatively low temperatures encountered in the absorption step, a higher pH favors acid gas absorption, whereas at the relatively high temperatures encountered in the desorption step, a lower pH favors the release of absorbed acid gases.

[0086] The acid preferably has a pK of less than 6, especially less than 5, measured at atmospheric pressure and 25°C. a It has more than one dissociation step and therefore more than one pK a In the case of acids with pK a The condition is met if one of the values ​​is within the specified range. The acid is preferably selected from protic acids (Bronsted acids).

[0087] The acid is preferably added in an amount such that the pH of the aqueous solution, measured at 120°C, is from 7.9 to less than 9.5, preferably from 8.0 to less than 8.8, more preferably from 8.0 to less than 8.5, and most preferably from 8.0 to less than 8.2.

[0088] The amount of acid is, in one embodiment, from 0.1 to 5.0% by weight, preferably from 0.2 to 15-4.5% by weight, more preferably from 0.5 to 4.0% by weight, and most preferably from 1.0 to 2.5% by weight, based on the total weight of the absorbent.

[0089] The acid is selected from organic and inorganic acids. Suitable organic acids include, for example, phosphonic acids, sulfonic acids, carboxylic acids, and amino acids. In certain embodiments, the acid is a polybasic acid.

[0090] Suitable acids are, for example: Mineral acids, such as hydrochloric acid, sulfuric acid, amidosulfuric acid, phosphoric acid, partial esters of phosphoric acid, such as mono- and di-alkyl phosphates and mono- and diaryl phosphates, e.g., tridecyl phosphate, dibutyl phosphate, diphenyl phosphate and bis(2-ethylhexyl) phosphate, boric acid, carboxylic acids, such as saturated aliphatic monocarboxylic acids, e.g., formic acid, acetic acid, propionic acid, butyric acid, isobutyric acid, valeric acid, isovaleric acid, pivalic acid, caproic acid, n-heptanoic acid, caprylic acid, 2-ethylhexanoic acid, pelargonic acid, caproic acid, neodecanoic acid, undecanoic acid, lauric acid, tridecanoic acid, myristic acid, pentadecanoic acid, palmitic acid, margaric acid, stearic acid, isostearic acid, arachidic acid, behenic acid; saturated aliphatic polycarboxylic acids, such as oxalic acid, malonic acid, succinic acid cycloaliphatic mono- and polycarboxylic acids, such as cyclohexanecarboxylic acid, hexahydrophthalic acid, tetrahydrophthalic acid, resin acids, naphthenic acid; aliphatic hydroxycarboxylic acids, such as glycolic acid, lactic acid, mandelic acid, hydroxybutyric acid, tartaric acid, malic acid, citric acid; halogenated aliphatic carboxylic acids, such as trichloroacetic acid or 2-chloropropionic acid; aromatic mono- and polycarboxylic acids, such as benzoic acid, salicylic acid, gallic acid, positional isomers of toluic acid, methoxybenzoic acid, chlorobenzoic acid, nitrobenzoic acid, phthalic acid, terephthalic acid, isophthalic acid; technical carboxylic acid mixtures, such as versatic acid, sulfonic acids, such as methylsulfonic acid, butylsulfonic acid, 3-hydroxypropylsulfonic acid, sulfoacetic acid, benzenesulfonic acid, p-toluenesulfonic acid, p-xylenesulfonic acid, 4-dodecylbenzenesulfonic acid, 1-naphthalenesulfonic acid, dinonylnaphthalenesulfonic acid and dinonylnaphthalenedisulfonic acid, trifluoromethyl- or nonafluoro-n-butylsulfonic acid, camphorsulfonic acid, 2-(4-(2-hydroxyethyl)-1-piperazinyl)ethanesulfonic acid (HEPES), Organic phosphonic acids, such as those of formula (IV) R4-PO3H (IV) wherein R4 is a C1-C6 optionally substituted with up to four substituents independently selected from carboxyl, carboxamido, hydroxyl, and amino. 1~18 It is a phosphonic acid of (alkyl).

[0091] These include alkylphosphonic acids, such as methylphosphonic acid, propylphosphonic acid, 2-methylpropylphosphonic acid, t-butylphosphonic acid, n-butylphosphonic acid, 2,3-dimethylbutylphosphonic acid, octylphosphonic acid; hydroxyalkylphosphonic acids, such as hydroxymethylphosphonic acid, 1-hydroxyethylphosphonic acid, 2-hydroxyethylphosphonic acid; arylphosphonic acids, such as phenylphosphonic acid, tolylphosphonic acid, xylylphosphonic acid, aminoalkylphosphonic acids, such as aminomethylphosphonic acid, 1-aminoethylphosphonic acid, 1-dimethylaminoethylphosphonic acid, 2-aminoethylphosphonic acid, 2-(N-methylamino)ethylphosphonic acid, 3-aminopropylphosphonic acid, 2-Aminopropylphosphonic acid, 1-aminopropylphosphonic acid, 1-aminopropyl-2-chloropropylphosphonic acid, 2-aminobutylphosphonic acid, 3-aminobutylphosphonic acid, 1-aminobutylphosphonic acid, 4-aminobutylphosphonic acid, 2-aminopentylphosphonic acid, 5-aminopentylphosphonic acid, 2-aminohexylphosphonic acid, 5-aminohexylphosphonic acid, 2-aminooctylphosphonic acid, 1-aminooctylphosphonic acid, 1-aminobutylphosphonic acid; amidoalkylphosphonic acids, such as 3-hydroxymethylamino-3-oxopropylphosphonic acid; and phosphonocarboxylic acids, such as 2-hydroxyphosphonoacetic acid and 2-phosphonobutane-1,2,4-tricarboxylic acid; Formula (V)

[0092] [ka] (Wherein R5 is H or C 1~5 alkyl, Q is H, OH or NR62 and R6 is H or CH2PO3H2), such as 1-hydroxyethane-1,1-diphosphonic acid; Formula (VI)

[0093] [ka] (Wherein Z is C 2~5 - alkylene, cycloalkanediyl, phenylene or C interrupted by cycloalkanediyl or phenylene 2~5 -alkylene, Y is CH2PO3H2, and m is 0 to 4), such as ethylenediaminetetra(methylenephosphonic acid), diethylenetriaminepenta(methylenephosphonic acid), and bis(hexamethylene)triaminepenta(methylenephosphonic acid); Formula (VII) R7-NY2(VII) (Wherein R7 is C 1~5 Alkyl, C 2~5 -hydroxyalkyl or R8, where R8 is CH2PO3H2) phosphonic acids, such as nitrilotris(methylenephosphonic acid) and 2-hydroxyethyliminobis(methylenephosphonic acid); aminocarboxylic acids having a tertiary amino group or an amino group having at least one secondary or tertiary carbon atom directly adjacent to the amino group; for example α-amino acids having a tertiary amino group or an amino group having at least one secondary or tertiary carbon atom directly adjacent to the amino group, such as N,N-dimethylglycine (dimethylaminoacetic acid), N,N-diethylglycine, alanine (2-aminopropionic acid), N-methylalanine (2-(methylamino)propionic acid), N-dimethylalanine, N-ethylalanine, 2-methylalanine (2-aminoisobutyric acid), leucine (2-amino-4-methylpentan-1-oic acid), N-methylleucine, N,N-dimethyl Chileucine, Isoleucine (1-amino-2-methylpentanoic acid), N-methylisoleucine, N,N-dimethylisoleucine, Valine (2-aminoisovaleric acid), α-methylvaline (2-amino-2-methylisovaleric acid), N-methylvaline (2-methylaminoisovaleric acid), N,N-dimethylvaline, Proline (pyrrolidine-2-carboxylic acid), N-methylproline, N-methylserine, N,N-dimethylserine, 2-(methylamino)isobutyric acid, Piperidine-2-carboxylic acid, N-methylpiperidine-2-carboxylic acid, β-amino acids having a tertiary amino group or an amino group having at least one secondary or tertiary carbon atom directly adjacent to the amino group, such as 3-dimethylaminopropionic acid, N-methyliminodipropionic acid, N-methylpiperidine-3-carboxylic acid, γ-amino acids having a tertiary amino group or an amino group having at least one secondary or tertiary carbon atom directly adjacent to the amino group, such as 4-dimethylaminobutyric acid; Alternatively, it includes an aminocarboxylic acid having a tertiary amino group or an amino group having at least one secondary or tertiary carbon atom immediately adjacent to the amino group, such as N-methylpiperidine-4-carboxylic acid.

[0094] Of the inorganic acids, phosphoric acid and sulfuric acid are preferred, especially sulfuric acid.

[0095] Of the carboxylic acids, formic acid, acetic acid, benzoic acid, succinic acid and adipic acid are preferred.

[0096] Of the sulfonic acids, methanesulfonic acid, p-toluenesulfonic acid and 2-(4-(2-hydroxyethyl)-1-piperazinyl)ethanesulfonic acid (HEPES) are preferred.

[0097] Of the phosphonic acids, 2-hydroxyphosphonoacetic acid, 2-phosphonobutane-1,2,4-tricarboxylic acid, 1-hydroxyethane-1,1-diphosphonic acid, ethylenediaminetetra(methylenephosphonic acid), diethylenetriaminepenta(methylenephosphonic acid), bis(hexamethylene)triaminepenta(methylenephosphonic acid) (HDTMP), and nitrilotris(methylenephosphonic acid) are preferred, of which 1-hydroxyethane-1,1-diphosphonic acid is particularly preferred.

[0098] Of the aminocarboxylic acids having a tertiary amino group or an amino group having at least one secondary or tertiary carbon atom directly adjacent to the amino group, N,N-dimethylglycine and N-methylalanine are preferred.

[0099] More preferably, the acid is an inorganic acid.

[0100] Non-aqueous organic solvents: In one embodiment, the diluent of the absorbent comprises at least one non-aqueous organic solvent. In certain cases, the diluent contains only limited amounts of water, or essentially no water, in addition to the non-aqueous organic solvent. It is desirable to limit the water content of the absorbent to, for example, at most 20% by weight, or at most 10% by weight, preferably at most 5% by weight, or at most 2% by weight.

[0101] The non-aqueous organic solvent is preferably: C4~C 10 alcohols, such as n-butanol, n-pentanol and n-hexanol, ketones, such as cyclohexanone, esters such as ethyl acetate and butyl acetate, Lactones, such as y-butyrolactone, o-valerolactone and E-caprolactone, Amides, such as tertiary carboxamides, such as N,N-dimethylformamide, or N-formylmorpholine and N-acetylmorpholine, Lactams such as y-butyrolactam, o-valerolactam, and E-caprolactam, and N-methyl-2-pyrrolidone (NMP), sulfones, such as sulfolane; sulfoxides, such as dimethyl sulfoxide (DMSO); glycols, such as ethylene glycol (EG) and propylene glycol, polyalkylene glycols, such as diethylene glycol (DEG) and triethylene glycol (TEG); Di or Mono (C 1~4 -alkyl ether) glycols, for example ethylene glycol dimethyl ether, Di or Mono (C 1~4 -alkyl ether) polyalkylene glycols, such as diethylene glycol dimethyl ether, dipropylene glycol monomethyl ether and triethylene glycol dimethyl ether, cyclic ureas, such as N,N-dimethylimidazolidin-2-one and dimethylpropyleneurea (DMPU); Thioalkanols, such as ethylenedithioethanol, thiodiethylene glycol (thiodiglycol, TDG) and methylthioethanol, and mixtures thereof.

[0102] More preferably, the non-aqueous solvent is selected from sulfones, glycols and polyalkylene glycols. Most preferably, the non-aqueous solvent is selected from sulfones. A preferred non-aqueous solvent is sulfolane.

[0103] Other additives: The absorbent may also contain additives such as corrosion inhibitors, enzymes, antifoaming agents, etc. Generally, the amount of such additives ranges from about 0.005% to 3% based on the total weight of the absorbent.

[0104] Use of absorbent: The present invention also relates to the use of the absorbents described herein to remove acid gases from fluid streams.

[0105] In one embodiment, the present invention relates to the use of an absorbent as described herein for the non-selective removal of acid gases from a fluid stream, in which case the absorbent preferably comprises at least one activator selected from sterically unhindered primary amines and / or sterically unhindered secondary amines, as described above.

[0106] In another embodiment, the present invention relates to the use of the absorbent described herein for the selective removal of hydrogen sulfide from a fluid stream comprising carbon dioxide and hydrogen sulfide, in which case the absorbent preferably does not contain any sterically unhindered primary amines or sterically unhindered secondary amines.

[0107] In one embodiment, the method is a method for non-selective removal of acid gases from a fluid stream, in which case the absorbent preferably comprises at least one activator selected from sterically unhindered primary amines and / or sterically unhindered secondary amines, as described above.

[0108] In another embodiment, the method is for selectively removing hydrogen sulfide from a fluid stream comprising carbon dioxide and hydrogen sulfide, in which case the absorbent preferably does not contain any sterically unhindered primary amines or sterically unhindered secondary amines.

[0109] In this context, "selectivity towards hydrogen sulfide" means: [mol(H2S) / mol(CO2)] 液相 / [mol(H2S) / mol(CO2)] ガス相 (In the formula, [mol(H2S) / mol(CO2)] 液相 is the molar H2S / CO2 ratio in the liquid phase in contact with the gas phase, [mol(H2S) / mol(CO2)] ガス相is understood to mean the value of the exponent of (where H2S / CO2 is the molar H2S / CO2 ratio in the gas phase).

[0110] In a standard gas scrubbing process, the liquid phase is the absorbent in the bottom of the absorber and the gas phase is the fluid stream being treated.

[0111] A process is understood to be HS selective if the value of the index is greater than 1. Where the process is for the selective removal of hydrogen sulfide from a fluid stream comprising carbon dioxide and hydrogen sulfide, the selectivity for hydrogen sulfide is preferably at least 1.1, even more preferably at least 2, and most preferably at least 4.

[0112] The absorbents described herein are suitable for treating any type of fluid. The fluids are first gases, such as natural gas, synthesis gas, coke oven gas, cracking gas, coal gasification gas, cycle gas, landfill gas, and combustion gas, and then liquids that are essentially immiscible with the absorbent, such as LPG (liquefied petroleum gas) or NGL (natural gas liquids). The method of the present invention is particularly suitable for treating hydrocarbon-based fluid streams. The hydrocarbons present are, for example, aliphatic hydrocarbons, such as C1-C4 hydrocarbons, for example methane, unsaturated hydrocarbons, for example ethylene or propylene, or aromatic hydrocarbons, for example benzene, toluene, or xylene.

[0113] The absorbents of the present invention are suitable for the removal of acid gases such as CO, H, S, SO, SO, CS, HCN, COS, and mercaptans, as well as other acid gases present in fluid streams, such as COS and mercaptans.

[0114] The absorbent is suitable for the selective removal of hydrogen sulfide from fluid streams containing carbon dioxide and hydrogen sulfide, and allows for high H2S selective purification at low solvent circulation rates. The absorbent is useful in sulfur plant tail gas treatment unit (TGTU) applications, acid gas enrichment (AGE) processes that upgrade dilute acid off-gas from the treatment unit to a higher quality Claus plant feed stream, or in the treatment of associated gas and refinery gas.

[0115] In the method of the present invention, the fluid stream is contacted with an absorbent in an absorber in an absorption step, resulting in at least partial scrubbing of carbon dioxide and hydrogen sulfide, thereby obtaining a CO2- and H2S-depleted fluid stream and a CO2- and H2S-loaded absorbent.

[0116] The absorber used is a scrubbing device used in conventional gas scrubbing processes. Suitable scrubbing devices include, for example, random packing, structured packing, and trayed columns, membrane contactors, radial flow scrubbers, jet scrubbers, Venturi scrubbers, and rotary spray scrubbers. Preferably, structured packing, random packing, and trayed columns are used, and more preferably, trayed and random packing columns are used. The fluid stream is preferably treated with the absorbent in a countercurrent manner in the column. The fluid is generally fed to the lower region of the column, and the absorbent is fed to the upper region of the column. Sieve trays, bubble cap trays, or valve trays are installed in the tray column, over which the liquid flows. Columns with random packing may be filled with different shaped bodies. Heat and mass transfer are improved by the increased surface area provided by the shaped bodies, which usually have a size of about 25 to 80 mm. Known examples include Raschig rings (hollow cylinders), Pali rings, Hiflow rings, and Intalox saddles. Random packings can be introduced into the column in an ordered or random manner (as beds). Possible materials include glass, ceramic, metal, and plastic. Structured packings are a further development of ordered random packings. They have an ordered structure. As a result, in the case of packings, it is possible to suppress the pressure drop in the gas flow. There are various designs of structured packings, such as woven fabric packings or sheet metal packings. The materials used can be metal, plastic, glass, and ceramic.

[0117] The temperature of the absorbent in the absorption step is generally about 30 to 100°C, for example 30 to 70°C at the top of the column and 50 to 100°C at the bottom of the column if a column is used.

[0118] The method of the present invention may comprise one or more, in particular two, successive absorption steps. Absorption may be carried out in a number of successive constituent steps, in which case the crude gas containing the acid gas components is contacted with a substream of absorbent in each constituent step. The absorbent with which the crude gas is contacted may already partially contain acid gases, meaning that it may be, for example, an absorbent that has been recycled from a downstream absorption step to the first absorption step, or a partially regenerated absorbent. For the implementation of two-stage absorption, reference is made to publications EP 0 159 495, EP 0 190 434, EP 0 359 991 and WO 00100271.

[0119] Those skilled in the art will appreciate that high levels of hydrogen sulfide removal at defined selectivity can be achieved by varying the conditions in the absorption step, for example, more specifically, the absorbent / fluid stream ratio, the height of the absorber tower, the type of internal structure promoting contact in the absorber (e.g., random packing, trays, or structured packing), and / or the residual loading of the regenerated absorbent. Because CO2 is absorbed more slowly than HS, longer residence times result in greater CO2 absorption than shorter residence times. Conversely, longer residence times result in lower HS selectivity. Higher towers therefore result in less selective absorption. Trays or structured packing with a relatively high liquid holdup also result in less selective absorption. The heating energy introduced during regeneration can be used to adjust the residual loading of the regenerated absorbent. A lower residual loading of the regenerated absorbent leads to improved absorption.

[0120] The method preferably includes a regeneration step in which the absorbent having absorbed CO and H S is regenerated. In the regeneration step, CO and H S, and optionally further acid gas components, are released from the absorbent having absorbed CO and H S to obtain a regenerated absorbent. Preferably, the regenerated absorbent is subsequently recycled to the absorption step. Generally, the regeneration step includes at least one of the following means: heating, reducing pressure, and stripping with an inert fluid.

[0121] The regeneration step preferably comprises heating the absorbed absorbent with the acid gas components, for example by means of a boiler, natural circulation evaporator, forced circulation evaporator or forced circulation flash evaporator. The absorbed acid gases are stripped with steam obtained by heating the solution. It is also possible to use an inert fluid, for example nitrogen, instead of steam. The absolute pressure in the desorber is usually 0.1 to 3.5 bar, preferably 1.0 to 2.5 bar. The temperature is usually 50 to 170°C, preferably 80 to 130°C, the temperature of course depending on the pressure. In some cases, an additional regeneration step of a slipstream of regenerated absorption solvent is required. SO in the fluid stream x , NO x In the presence of CO, heat-stable salts such as sulfates, nitrates, and formates can be formed. To achieve lower concentrations of these undesirable components, an additional distillation step at elevated temperatures can be applied, or the heat-stable salts can be removed by an ion exchange process.

[0122] The regeneration step may alternatively or additionally comprise a depressurization, which involves at least one depressurization of the absorbed absorbent from the high pressure present at the initiation of the absorption step to a lower pressure. The depressurization can be achieved, for example, by a throttle valve and / or a depressurization turbine. Regeneration with a depressurization step is described, for example, in publications US 4,537,753 and US 4,553,984.

[0123] The acid gas components may be released in the regeneration step, for example, in a vacuum tower, such as a vertically or horizontally mounted flash vessel, or a countercurrent tower with internals.

[0124] The regeneration column can also be a column with random packing, structured packing, or trays. The regeneration column has a heater at the bottom, such as a forced circulation evaporator with a circulation pump. At the top, the regeneration column has an outlet for the released acid gases. The entrained absorption medium vapor is condensed in a condenser and recycled to the column.

[0125] It is possible to connect multiple vacuum towers in series, where regeneration is carried out at different pressures. For example, regeneration can be carried out in a pre-vacuum tower at a high pressure, typically above about 1.5 bar partial pressure of the acid gas components in the absorption step, and in a main vacuum tower at a lower pressure, for example, 1 to 2 bar absolute. Regeneration using two or more vacuum stages is described in publications U.S. Pat. No. 4,537,753, U.S. Pat. No. 4,553,984, EP 0 159 495, EP 0 202 600, EP 0 190 434, and EP 0 121 109.

[0126] The process of the present invention using compounds of formula (I) exhibits high selectivity in the treatment of gaseous streams containing both H2S and CO2. The process of the present invention also provides high rates of removal of mercaptans or other sulfur compounds that may be present in such gaseous streams. Compounds of formula (I) exhibit high thermal stability, which allows for high temperature regeneration and more complete regeneration of absorbent solutions with decreasing loading.

[0127] The present invention is illustrated in more detail in the examples that follow.

[0128] [Example 1] Preparation of 2-[2-(tert-butylamino)ethylsulfanyl]ethanol. 1,7 Sodium methylate was dissolved in 15 ml dry ethanol. Mercaptoethanol was added to the solution while stirring. After mixing was completed, the mixture was stirred for an additional 15 minutes, and a solution of 2.5 g of 2-chloro-N-tert-butylethylamine hydrochloride dissolved in 50 ml dry ethanol was added dropwise, maintaining the temperature in the range of 35 to 40°C. After the mixing process was completed, the resulting suspension was heated to 75°C and stirred for an additional 90 minutes. After stirring overnight at room temperature, the suspension was filtered, and the filtrate was evaporated in a rotary evaporator at 90°C and 60 mbar.

[0129] 2.5 g of 2-[2-(tert-butylamino)ethylsulfanyl]ethanol was obtained, with a calculated yield of 97%. The structure of the compound is: 1 This was confirmed by H-NMR.

[0130] [Example 2] Comparison of the properties of 2-[2-(tert-butylamino)ethylsulfanyl]ethanol (TBAESE) and 2-[2-(tert-butylamino)ethoxy]ethanol (TBAEE) a) Thermal stability The thermal stability of TBAESE was compared with that of TBAEE and MDEA with and without acid gas loading.

[0131] Each solution (8 mL) was initially placed in a cylinder (10 mL) and the cylinder was closed. The cylinder was heated to 150 °C for 125 h. In the experiments carried out under acid gas loading, the acid gas loading of the solution was 20 Nm CO2. 3 / t 溶媒 and H2S 20Nm 3 / t 溶媒 The decomposition level of the amine was calculated from the amine concentration measured by gas chromatography before and after the experiment. The results are shown in Table 1.

[0132] [Table 1]

[0133] It is clear that TBAESE has higher thermal stability than MDEA and TBAEE in aqueous solution in the presence of an acid gas carrier.

[0134] b) Acid gas support and regeneration pK of TBAESE and TBAEE aThe pH values ​​were measured in the temperature range from 20°C to 120°C. The results are shown in Figure 1. Aqueous amine solutions with a concentration of 0.01 mol / l were neutralized to 50% with 0.005 mol / l HCl solution. As a result, the measured pH of the 50% neutralized amine solution is equal to the pKa value of the amine. The measurements were carried out in a glass vessel pressurized with nitrogen to avoid any loss of water and solvent.

[0135] pK of TBAESE and TBAEE a The pK values ​​of MDEA were comparable across the entire range measured. a From these measurements, it can be concluded that the acid gas loading and regeneration of TBAESE is comparable to that of TBAEE.

[0136] In summary, TBAESE and TBAEE have similar absorption properties, but TBAESE exhibits slightly improved thermal stability. This allows TBAESE to be operated at slightly higher regeneration temperatures, allowing for more complete regeneration of the absorbent. Furthermore, TBAESE combines, in a single molecule, the advantages of sterically hindered amines, such as high selectivity for HS, and the advantages of thioalcohols, such as high removal rates of other sulfur compounds, especially mercaptans, that may be present in the feed gas. The following is one embodiment of the present invention. (1) A method for removing acid gases from a fluid stream, comprising contacting the fluid stream with an absorbent to obtain a treated fluid stream and an absorbed absorbent, the absorbent comprising at least one diluent and a compound represented by the general formula (I). [ka] (Wherein R1 is C 1 ~C 3 -alkyl and R2 is C 1 ~C 3 -alkyl, and R3 is hydrogen and C 1 ~C 3 -alkyl, and R4 is selected from hydrogen and C 1 ~C 3 -alkyl, and n is an integer ranging from 1 to 4. (2) Each of R1, R2, and R3 is C 1 The method according to (1), wherein the alkyl is -alkyl. (3) The method according to (1) or (2), wherein the compound of general formula (I) is 2-[2-(tert-butylamino)ethylsulfanyl]ethanol. (4) The method according to any one of (1) to (3), wherein the diluent comprises water. (5) The method according to (4), wherein the absorbent additionally contains an acid. (6) The method according to any one of (1) to (5), wherein the diluent comprises a non-aqueous organic solvent. (7) The organic solvent is C 4~10 Alcohols, ketones, esters, lactones, amides, lactams, sulfones, sulfoxides, glycols, polyalkylene glycols, di- or mono-(C 1 ~C 4 Alkyl ether) glycol, di or mono (C 1~4 (6) The method according to (6), wherein the alkyl ether is selected from polyalkylene glycols, cyclic ureas, thioalkanols, and mixtures thereof. (8) The method according to any one of (1) to (7), wherein the absorbent comprises at least one activator selected from sterically unhindered primary amines and / or sterically unhindered secondary amines. (9) The method according to (8), wherein the activating substance is piperazine. (10) The method according to any one of (1) to (7), for selectively removing hydrogen sulfide from a fluid stream containing carbon dioxide and hydrogen sulfide. (11) The method according to any one of (1) to (10), wherein the absorbed absorbent is regenerated by at least one of the means of heating, reducing pressure, and stripping with an inert fluid. (12) Use of the absorbent according to any one of (1) to (9) for removing acid gases from a fluid stream, or use of the absorbent according to any one of (1) to (7) for selectively removing hydrogen sulfide from a fluid stream containing carbon dioxide and hydrogen sulfide. (13) Formula (II)

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Claims

1. A method for removing acid gases from a fluid stream, comprising contacting the fluid stream with an absorbent to obtain a treated fluid stream and an absorbed absorbent, the absorbent comprising at least one diluent and a compound represented by general formula (I): 【Chemical 1】 (Wherein R1 is C 1 ~C 3 -alkyl and R2 is C 1 ~C 3 -alkyl, and R3 is hydrogen and C 1 ~C 3 -alkyl, and R4 is selected from hydrogen and C 1 ~C 3 -alkyl, and n is an integer ranging from 1 to 4.

2. Each of R1, R2 and R3 is C 1 The method of claim 1, wherein the alkyl is -alkyl.

3. 3. The method according to claim 1 or 2, wherein the compound of general formula (I) is 2-[2-(tert-butylamino)ethylsulfanyl]ethanol.

4. 4. The method of claim 1, wherein the diluent comprises water.

5. The method of claim 4 wherein the absorbent additionally comprises an acid.

6. 6. The method of claim 1, wherein the diluent comprises a non-aqueous organic solvent.

7. The organic solvent is C 4～10 Alcohols, ketones, esters, lactones, amides, lactams, sulfones, sulfoxides, glycols, polyalkylene glycols, di- or mono-(C 1 ~C 4 Alkyl ether) glycol, di or mono (C 1～4 7. The method of claim 6, wherein the alkyl ether is selected from polyalkylene glycols, cyclic ureas, thioalkanols, and mixtures thereof.

8. 8. The method of claim 1, wherein the absorbent comprises at least one activator selected from sterically unhindered primary amines and / or sterically unhindered secondary amines.

9. 9. The method of claim 8, wherein the activating agent is piperazine.

10. 8. The method of any one of claims 1 to 7, wherein hydrogen sulfide is selectively removed from a fluid stream comprising carbon dioxide and hydrogen sulfide.

11. 11. The method according to any one of claims 1 to 10, wherein the absorbed absorbent is regenerated by at least one of the following means: heating, vacuum and stripping with an inert fluid.

12. 10. Use of an absorbent as claimed in any one of claims 1 to 9 for the removal of acid gases from a fluid stream, or use of an absorbent as claimed in any one of claims 1 to 7 for the selective removal of hydrogen sulfide from a fluid stream comprising carbon dioxide and hydrogen sulfide.

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