Process for removing acid gases from fluid streams

Abstract

The present invention relates to a method for removing acidic gases from a fluid stream, wherein the fluid stream is contacted with an absorbent to obtain a treated fluid stream and a loaded absorbent, the absorbent comprising at least one diluent and a compound of general formula (I), wherein R1 is a C1-C3 alkyl group; R2 is a C1-C3 alkyl group; R3 is selected from hydrogen and a C1-C3 alkyl group; R4 is selected from hydrogen and a C1-C3 alkyl group and n is an integer of 1-4. #imgabs0#

Description

[0001] illustrate

[0002] The present invention relates to the use of absorbents and methods for removing acid gases from fluid streams. In certain embodiments, the present invention relates to the selective removal of hydrogen sulfide from a fluid stream comprising carbon dioxide and hydrogen sulfide.

[0003] For various reasons, it is desirable to remove acid gases such as CO from fluid streams such as natural gas, refinery gas, or synthesis gas. 2 , H 2 S. SO 2 , CS 2 , HCN, COS or mercaptans. The sulfur compounds in natural gas tend to form corrosive acids, especially together with the water that is often entrained in the natural gas. For the transportation of natural gas in pipelines or for further processing in natural gas liquefaction plants (LNG = liquefied natural gas), given limits with regard to sulfur-containing impurities must be observed. In addition, large amounts of sulfur compounds are foul-smelling and toxic even in low concentrations.

[0004] Carbon dioxide must be removed from natural gas because high concentrations of CO 2 Reduce the calorific value of the gas. In addition, CO 2 Together with moisture it can cause corrosion in pipes and valves.

[0005] Known methods for removing acid gases include washing operations with aqueous absorbent solutions of inorganic or organic bases. When the acid gases dissolve in the absorbent, ions are formed with the base. The absorbent can be regenerated by decompression to a lower pressure and / or by stripping, whereby the ionic species react in reverse and release the acid gases and / or stripped out with the aid of an inert fluid such as steam. After the regeneration process, the absorbent can be reused.

[0006] The substantial removal of CO 2 and H 2 The method of S is called "total absorption". Although CO 2 The removal of CO may be necessary to avoid corrosion problems and provide the desired calorific value to the consumer, but occasionally it is necessary or desirable to treat the 2 and H 2 S acid gas mixture to selectively remove H from the mixture 2 S, while CO 2 For example, the gas pipeline code sets the H 2 The S content limit is about CO 2 is more stringent, because H 2 S to CO 2 More toxic and corrosive. The usual natural gas pipeline specifications usually include H 2The sulfur content is limited to 4 ppmv. 2 The wider limit is 2 vol% when the selectivity H 2 S removal is usually ideal for H2O in feeds that allow sulfur recovery (such as downstream Claus units). 2 S content is enriched.

[0007] Selectively hindered secondary amines such as 2-(2-tert-butylaminoethoxy)ethanol (TBAEE) and tertiary amines such as methyldiethanolamine (MDEA) show H 2 S relative to CO 2 These amines are therefore suitable for the production of CO 2 and H 2 S in the gas mixture relative to CO 2 Selective removal of H 2 S and are usually used as aqueous mixtures. These amines do not react directly with CO 2 reaction; instead, CO 2 Reacts with amines and water in a slow reaction to give bicarbonate ions. The reaction kinetics allow H 2 S reacts more quickly directly with the amine groups of the sorbent in aqueous solution to form hydrosulfide ions.

[0008] The use of hydroxyl-substituted amines (alkanolamines) such as those described above has become popular because the presence of hydroxyl groups tends to improve the solubility of the absorbent and its acid gas reaction products in widely used aqueous solvent systems, thus facilitating solvent circulation through conventional absorber / regenerator units by inhibiting phase separation. The presence of hydroxyl groups may also reduce the volatility of the amine and, therefore, reduce amine losses during operation.

[0009] However, this preferred approach may present its own problems in certain environments. Although alkanolamines will effectively remove acid gases at higher pressures, H 2 The selectivity of S removal can be expected due to the 2 Direct physical absorption in liquid solvents and reaction with hydroxyl groups on amine compounds significantly reduce the 2 The reaction preferentially reacts with amino nitrogen, higher pressures force the reaction with oxygen, and at higher pressures, the bicarbonate / hemicarbonate / carbonate reaction products formed by reactions at hydroxyl sites increase with increasing pressure. 2 The S selectivity is stabilized by the gradual loss of S.

[0010] Furthermore, while the presence of hydroxyl groups improves the aqueous solubility of the amine, the hydroxyl groups tend to impart surfactant properties to the absorbent / acid gas reaction product, thereby potentially leading to troublesome foaming phenomena during gas processing unit operations.

[0011] Another known problem with the use of aqueous amine mixtures in the absorption treatment of gas mixtures is that at temperatures falling within the regeneration temperature range of the aqueous amine mixtures (typically 50-170° C.), separation into several phases may occur.

[0012] US Pat. No. 4,487,967, US Pat. No. 4,665,195 and US Pat. No. 4,894,178 relate to processes for preparing sterically hindered aminoether alcohols or diaminopolyalkylene ethers in the presence of a hydrogenation catalyst.

[0013] US 2015 / 0027055 describes a method for extracting CO from a CO 2 A method for selectively removing H2S from a gas mixture of 2,4-dimethyl-1-nitropropene, wherein the absorbent comprises a sterically hindered terminally etherified alkanolamine. The study found that the terminal etherification of the alkanolamine and the rejection of water make the H2S selectivity higher.

[0014] US 2010 / 0037775 describes an acid gas absorbent comprising an alkylaminoalkoxy (alcohol) monoalkyl ether and a method for extracting an acid gas containing H from an aqueous solution using an absorbent solution comprising the monoalkyl ether. 2 S and CO 2 Selectively remove H from a gas mixture 2 S's method.

[0015] WO 2013 / 181245 describes an absorbent composition for selective removal of H2S, wherein the absorbent composition comprises an aqueous amine mixture of an amination reaction product of tert-butylamine and a polyethylene glycol mixture and an organic cosolvent selected from sulfones, sulfone derivatives and sulfoxides, and a strong acid to inhibit phase separation.

[0016] WO 2014 / 001664 discloses absorbent solutions made from tertiary diamines belonging to the family of hindered aminoethylmorpholines. These compounds contain only tertiary amino groups, each of which features a basic nitrogen atom.

[0017] US 2013 / 011314 describes compounds containing one or more diamines, the two amine functional groups of which are not connected to each other through a ring, the amine functional group in the α position is always a tertiary group, and the amine functional group in the ω position is always a primary or secondary group, and describes the compounds in the presence of H 2 S and CO 2 Selective removal of H from gases 2 The use in S. The compounds described therein are characterized by secondary and tertiary amino groups, both of which are characterized by a basic nitrogen atom.

[0018] WO 2017 / 186466 discloses a method for removing acid gases from a fluid stream using a morpholino hindered amine compound.

[0019] WO 2018 / 146233 describes a process for removing acid gases from a fluid stream obtained by the reaction of a glycidol derivative with a hindered amine such as tert-butylamine.

[0020] WO 2019 / 043099 relates to absorbent solutions obtained by the reaction of tert-butylamine with hydroxyethylpyrrolidone and structurally related compounds and their use in gas treatment.

[0021] US 2017 / 0320008 discloses a method of 2 S and CO 2 A gaseous mixture of the two and a mixture containing an amine, water and at least one C 1-4 The H is selectively removed from the mixture by contacting the absorbent for mercaptans. 2 The disclosed method is effective for removing H 2 S has a high selectivity and also allows for improved removal of other sulfur components, especially mercaptans.

[0022] It is an object of the present invention to provide a further method suitable for removing acid gases from a fluid stream. The method is intended to be used in which substantial removal of CO 2 and H 2 The invention relates to an application of the present invention in the total absorption of sulfur and for the selective removal of hydrogen sulfide from a fluid stream. The absorbent used in the process has a high recycle capacity and a low volatility. Another object of the invention is to provide a gas treatment process based on a solvent with enhanced thermal stability, which can be operated at a higher temperature for a long time. Another object of the invention is to provide a method for treating a gas containing H 2 S and CO 2 Remove H from the gas mixture 2 A highly selective gas treatment method for S, which also allows the removal of additional gas that may be contained in H 2 S and CO 2 In particular, the process according to the invention should also allow the removal of mercaptans in this selective gas treatment process.

[0023] This object is achieved by a method for removing acid gases from a fluid stream, wherein the fluid stream is contacted with an absorbent to obtain a treated fluid stream and a loaded absorbent, the absorbent comprising at least one diluent and a compound of formula (I):

[0024]

[0025] Where R1 is C 1 -C 3 Alkyl; R2 is C 1 -C 3 Alkyl; R3 is selected from hydrogen and C 1-C 3 Alkyl; R4 is selected from hydrogen and C 1 -C 3 An alkyl group, wherein n is an integer of 1-4.

[0026] The compounds of general formula (I) are based on thiodiglycol and its derivatives and contain thioether functional groups. Compared to prior art gas treatment solvents containing oxy-ether functional groups, it was surprisingly found that the gas treatment process using solvents containing compounds of formula (I) exhibited higher thermal stability while maintaining favorable absorption properties.

[0027] Absorbent:

[0028] The process according to the invention is carried out in the presence of an absorbent.

[0029] The absorbent comprises a compound of formula (I) and at least one diluent.

[0030] Compound of formula (I):

[0031] The absorbent comprises a compound of formula (I).

[0032] In formula (I),

[0033] R1 is C 1 -C 3 Alkyl, preferably methyl, ethyl, propyl and isopropyl, most preferably methyl; R2 is C 1 -C 3 Alkyl; preferably methyl, ethyl, propyl and isopropyl, most preferably methyl;

[0034] R3 is selected from hydrogen and C 1 -C 3 Alkyl, preferably methyl, ethyl, propyl and isopropyl, most preferably methyl;

[0035] R4 is selected from hydrogen and C 1 -C 3 Alkyl, preferably methyl, ethyl, propyl and isopropyl, most preferably methyl; and

[0036] It is an integer of 1-4, preferably 1 or 2, and most preferably 1.

[0037] 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.

[0038] In a preferred embodiment, the compound of formula (I) is selected from

[0039] 2-[2-(tert-Butylamino)ethylthio]ethanol; or

[0040] N-[2-(2-methoxyethylthio)ethyl]-2-methyl-propan-2-amine; or

[0041] N-[2-(2-ethoxyethylthio)ethyl]-2-methyl-propan-2-amine; or

[0042] 2-[2-(Isopropylamino)ethylthio]ethanol; or

[0043] N-[2-(2-methoxyethylthio)ethyl]propan-2-amine; or

[0044] N-[2-(2-Ethoxyethylthio)ethyl]propan-2-amine.

[0045] In a most preferred embodiment, the compound of formula (I) is 2-[2-(tert-butylamino)ethylthio]ethanol.

[0046] The absorbent comprises preferably 10 to 70% by weight, more preferably 15 to 65% by weight, most preferably 20 to 60% by weight of the compound of the general formula (I), based on the total weight of the absorbent.

[0047] Synthesis of compounds of formula (I):

[0048] Compounds of formula (I) are commercially available or can be prepared by various methods.

[0049] In a preferred embodiment, the compound of formula (I) is prepared by converting an amine of formula (II) with an alcohol of formula (III) in the liquid phase in the presence of a catalyst:

[0050]

[0051] Where R1 is C 1 -C 3 Alkyl; R2 is C 1 -C 3 Alkyl; R3 is selected from hydrogen and C 1 -C 3 alkyl;

[0052]

[0053] Wherein R4 is selected from hydrogen and C 1 -C 3 Alkyl; and

[0054] n is an integer from 1 to 4.

[0055] Preferably, the amine of formula (II) is tert-butylamine or isopropylamine.Most preferably, the amine of formula (II) is tert-butylamine.

[0056] The alcohol of formula (III) is preferably

[0057] 2-(2-Hydroxyethylthio)ethanol (thiodiglycol), or

[0058] 2-(2-methoxyethylthio)ethanol, or

[0059] 2-(2-Ethoxyethylthio)ethanol.

[0060] In a most preferred embodiment, the amine of formula (II) is tert-butylamine and the alcohol of formula (III) is thiodiglycol.

[0061] In another embodiment, n is equal to 3 or 4 and R4 is methyl.

[0062] Preferably, the molar ratio of the amine of formula (II) to the alcohol of formula (III) is 0.8:1-1.2:1, more preferably 0.9:1-1.1:1, most preferably 1:1.

[0063] Preferably, the reaction is carried out in the presence of a hydrogenation / dehydrogenation catalyst.

[0064] 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.

[0065] Preference is given to using 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.

[0066] More preferably, a catalyst comprising at least one metal selected from the group consisting of Cu, Co, Ni, Pd, Pt and Ru is used.

[0067] The abovementioned catalysts may be doped in a conventional manner with promoters, for example chromium, iron, cobalt, manganese, molybdenum, titanium, tin, metals of the alkali group, metals of the alkaline earth group and / or phosphorus.

[0068] The catalyst may be a supported or unsupported catalyst.

[0069] 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.

[0070] In a preferred embodiment of the present invention, catalysts of the Raney type are used.

[0071] As the Raney catalyst, it is preferred to use a Raney cobalt catalyst, a Raney nickel catalyst and / or a Raney copper catalyst. A Raney cobalt catalyst is particularly preferred.

[0072] In another preferred embodiment of the present invention, the catalyst is prepared by reducing a catalyst precursor in which the above-mentioned metals are present in the form of oxygen-containing compounds such as their oxides, carbonates or bicarbonates.

[0073] The catalyst precursor can be prepared by known methods, for example by precipitation, application by precipitation or impregnation.

[0074] In a particularly preferred embodiment, a supported hydrogenation / dehydrogenation catalyst containing copper, nickel and cobalt is used, wherein the catalytically active material of the catalyst before its reduction with hydrogen comprises oxide compounds of aluminum, copper, nickel and cobalt and 0.2 to 5.0% by weight of oxide compounds of tin, calculated as SnO. In a preferred embodiment, a catalyst according to the catalyst claimed in WO 2011 / 067199 is used.

[0075] In a preferred embodiment, the reaction is carried out at a temperature of 150-260°C. In a particularly preferred embodiment, the reaction is carried out at a temperature of 170-240°C. In a most preferred embodiment, the reaction is carried out at a temperature of 180-220°C.

[0076] The reaction can be carried out at a pressure of 5-300 bar. In a preferred embodiment, the reaction is carried out at a pressure of 50-200 bar (absolute). In a particularly preferred embodiment, the reaction is carried out at a pressure of 60-130 bar (absolute).

[0077] 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, under the reaction conditions, the amine of formula (II), the alcohol of formula (III) or the solvent is in the liquid phase.

[0078] The conversion is preferably carried out in the presence of hydrogen. During the reaction, hydrogen is not consumed, but has a beneficial effect on maintaining the activity of the catalyst. The partial pressure of hydrogen is preferably 2.5-200 bar, more preferably 5-150 bar, even more preferably 10-100 bar, most preferably 20-50 bar.

[0079] 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, dibutyl ether, alkanes, tetrahydrofuran (THF), glyme, diglyme, polyglyme, and generally diethers of oligo- and poly-propylene oxides and oligo- and poly-ethylene oxides or mixed oligo- or poly-alkylene oxides.

[0080] Useful solvents also include appropriate mixtures of the above-mentioned solvents.

[0081] Particularly preferred solvents are glyme, THF and water.

[0082] The amount of solvent present in the reaction mixture is generally 1-95% by weight, preferably 2.5-70%, more preferably 5-40%, based on the total weight of the reaction mixture, wherein the total weight of the reaction mixture includes all components added to the conversion of the amine of formula (II), i.e. the sum of the masses of the amine of formula (II) and the alcohol of formula (III) and the solvent.

[0083] The reaction can be carried out using a stirred tank reactor, a fixed bed tubular reactor and a multi-tubular reactor. It can be carried out in batch, semi-batch and continuous modes and with or without the circulation of the crude reaction mixture. In a preferred embodiment, the reaction is carried out in a fixed bed tubular reactor in a continuous mode.

[0084] The catalyst loading may be 0.01-2 kg / (L·h), preferably 0.1-1.0 kg / (L·h), and in a particularly preferred embodiment, 0.2-0.8 kg / (L·h) of the ether of formula (II).

[0085] The reaction product comprises unreacted amine of formula (II), alcohol of formula (III) and compound of formula (III).

[0086] The reaction product is preferably purified by carrying out one or more distillation steps.

[0087] In laboratory scale, the compound of formula (I) can also be obtained by reacting the compound of formula (IV) with 2-chloro-N-tert-butylethylamine hydrochloride in the presence of sodium ethoxide.

[0088]

[0089] Wherein R4 is selected from hydrogen and C 1 -C 3 Alkyl; and

[0090] n is an integer from 1 to 4.

[0091] 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 5-10 wt% solution in ethanol. Mixing is usually carried out in a manner such that the temperature of the resulting mixture remains within the range of 35-40°C. To complete the reaction, the resulting reaction mixture is usually stirred at 75°C for 90 minutes and at room temperature for another 6-12 hours.

[0092] Preferably, the reaction is carried out under inert conditions such as nitrogen atmosphere and using dry solvents. The resulting suspension is usually filtered through a laboratory filter and the filtrate is evaporated in a rotary evaporator to remove ethanol to obtain the desired product.

[0093] Thinner:

[0094] The compound of formula (I) is diluted with a diluent (preferably a low-cost diluent). The diluent may be a diluent that is resistant to carbon dioxide and other components of the gas such as H 2 S is a diluent having only physical absorption properties. However, it is preferred that the diluent interacts with the acid-base chemistry of the process. In particular, the diluent is an aqueous diluent. Due to their steric hindrance, the compounds of formula (I) do not have sufficient 2 The nucleophilic amine site on the molecule is directly attacked nucleophilically. Therefore, the water oxygen acts as a nucleophile to form a Brønsted acid H 2 CO 3 , which is neutralized by the compound of formula (I) acting as a Bronsted base to form ammonium bicarbonate.

[0095] In the most preferred embodiment, the diluent is water.

[0096] Activator:

[0097] In a preferred embodiment, the absorbent comprises at least one activator selected from the group consisting of non-hindered primary amines and / or non-hindered secondary amines. Non-hindered primary amines are understood to mean compounds having primary amino groups which are bonded to only one primary or secondary carbon atom. Non-hindered secondary amines are understood to mean compounds having secondary amino groups which are bonded to only primary carbon atoms. Non-hindered primary amines or non-hindered secondary amines act as CO 2 Therefore, the presence of an activator may be useful in applications involving non-selective removal of acid gases or where CO 2 Removal of is particularly desirable in applications where it is critical.

[0098] The activators preferably contain no acidic groups, such as in particular phosphonic acid, sulfonic acid and / or carboxylic acid groups.

[0099] The activator is, for example, selected from:

[0100] Alkanolamines, for example monoethanolamine (MEA), diethanolamine (DEA), ethylaminoethanol, 1-amino-2-methylpropan-2-ol, 2-amino-1-butanol, 2-(2-aminoethoxy)ethanol and 2-(2-aminoethoxy)ethylamine,

[0101] Polyamines, for example 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,

[0102] 5-, 6- or 7-membered saturated heterocyclic rings 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, for example piperazine, 2-methylpiperazine, N-methylpiperazine, N-ethylpiperazine, N-(2-hydroxyethyl)piperazine, N-(2-aminoethyl)piperazine, homopiperazine, piperidine and morpholine.

[0103] Particular preference is given to 5-, 6- or 7-membered saturated heterocycles which have 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. Very particular preference is given to piperazine.

[0104] In this preferred embodiment, wherein the absorbent comprises an activator, the absorbent preferably comprises 10-70 wt. %, more preferably 15-65 wt. %, most preferably 20-60 wt. % of the activator.

[0105] No unhindered amines

[0106] In another preferred embodiment, the absorbent does not contain any unhindered primary amine or unhindered secondary amine. 2 Strong activators of absorption, their presence in the absorbent can lead to H 2 S selective loss. Therefore, in which high H 2 In applications where S selectivity is desired, absorbents substantially free of such compounds are preferred.

[0107] Additional Hindered Amines

[0108] In one embodiment, the absorbent comprises a tertiary amine or a severely sterically hindered primary amine and / or a severely sterically hindered secondary amine which is different from the compound of the general formula (I). Severe steric hindrance is understood to be a tertiary carbon atom directly adjacent to a primary or secondary nitrogen atom. In this embodiment, the absorbent comprises a tertiary amine or a severely sterically hindered amine which is different from the compound of the general formula (I) in an amount of generally 5 to 50% by weight, preferably 10 to 40% by weight, more preferably 20 to 40% by weight, based on the total weight of the absorbent.

[0109] 1. Tertiary alkanolamines, for example: 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);

[0110] 2. Tertiary amino ethers, for example: 3-methoxypropyldimethylamine;

[0111] 3. Tertiary polyamines, for example bis-tertiary diamines, for example: N,N,N′,N′-tetramethylethylenediamine, N,N-diethyl-N′,N′-dimethylethylenediamine, N,N,N′,N′-tetraethylethylenediamine, N,N,N′,N′-tetramethyl-1,3-propylenediamine (TMPDA), N,N,N′,N′-tetraethyl-1,3-propylenediamine (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;

[0112] and mixtures thereof.

[0113] Tertiary alkanolamines, ie amines having at least one hydroxyalkyl group bonded to the nitrogen atom, are generally preferred. Methyldiethanolamine (MDEA) is particularly preferred.

[0114] Suitable severely hindered amines (ie amines having a tertiary carbon atom directly adjacent to a primary or secondary nitrogen atom) which are different from the compounds of the general formula (I) include in particular:

[0115] 1. Severely hindered secondary alkanolamines, such as 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;

[0116] 2. Severely hindered primary alkanolamines, such as 2-amino-2-methylpropanol (2-AMP); 2-amino-2-ethylpropanol; and 2-amino-2-propylpropanol;

[0117] 3. Severely hindered amino ethers, such as 1,2-bis(tert-butylaminoethoxy)ethane, bis(tert-butylaminoethyl)ether;

[0118] and mixtures thereof.

[0119] Severely hindered secondary alkanolamines are generally preferred.

[0120] Particular preference is given to 2-(2-tert-butylaminoethoxy)ethanol and 2-N-methylamino-2-methylpropan-1-ol.

[0121] acid:

[0122] In a further preferred embodiment, the absorbent is an aqueous absorbent (this means that the diluent comprises water) and the absorbent additionally comprises an acid.

[0123] The acid helps to regenerate the absorbent to a low loading and enhances the efficiency of the process. A protonation equilibrium is formed between the acid and the compound of formula (I). The position of the equilibrium is temperature dependent and the equilibrium shifts towards free oxygen at higher temperatures. ions and / or amine salts with lower protonation enthalpy displacement. At relatively low temperatures prevailing in the absorption step, higher pH promotes acid gas absorption, while at relatively high temperatures prevailing in the desorption step, lower pH supports release of absorbed acid gases.

[0124] The acid preferably has a pK measured at 25° C. at atmospheric pressure of less than 6, especially less than 5. a In the case of a system with more than one dissociation stage and thus a pK greater than 1 a In the case of acids, where pK a This requirement is met if one of the values ​​is within the stated range. The acid is suitably selected from protic acids (Brønsted acids).

[0125] 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, most preferably from 8.0 to less than 8.2.

[0126] In one embodiment, the amount of acid is 0.1-5.0 wt%, preferably 0.2-4.5 wt%, more preferably 0.5-4.0 wt%, most preferably 1.0-2.5 wt%, based on the total weight of the absorbent.

[0127] The acid is selected from organic and inorganic acids. Suitable organic acids include, for example, phosphonic acid, sulfonic acid, carboxylic acid and amino acid. In a particular embodiment, the acid is a polyacid.

[0128] Suitable acids are, for example:

[0129] Inorganic acids, for example hydrochloric acid, sulfuric acid, amidosulfuric acid, phosphoric acid, partial esters of phosphoric acid, for example mono- and dialkyl phosphates and mono- and diaryl phosphates, for example tridecyl phosphate, dibutyl phosphate, diphenyl phosphate and bis(2-ethylhexyl) phosphate; boric acid;

[0130] Carboxylic acids, for example saturated aliphatic monocarboxylic acids, for example formic acid, acetic acid, propionic acid, butyric acid, isobutyric acid, valeric acid, isovaleric acid, neopentanoic acid, hexanoic acid, n-heptanoic acid, octanoic acid, 2-ethylhexanoic acid, nonanoic acid, hexanoic acid, neodecanoic acid, undecanoic acid, lauric acid, tridecanoic acid, myristic acid, pentadecanoic acid, palmitic acid, heptadecanoic acid, stearic acid, isostearic acid, arachidic acid, behenic acid aliphatic carboxylic acids, such as oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, dodecanedioic acid; alicyclic mono- and polycarboxylic acids, such as cyclohexanecarboxylic acid, hexahydrophthalic acid, tetrahydrophthalic acid, resin acids, cycloalkane acids; aliphatic hydroxycarboxylic acids, such as glycolic acid, lactic acid, mandelic acid, hydroxybutyric acid, tartaric acid, malic acid, citric acid; hydrogenated aliphatic carboxylic acids, such as trichloroacetic acid or 2-chloropropionic acid; aromatic mono- and polycarboxylic acids, such as benzoic acid, salicylic acid, gallic acid, positionally isomeric methylbenzoate; acid, methoxybenzoic acid, chlorobenzoic acid, nitrobenzoic acid, phthalic acid, terephthalic acid, isophthalic acid; technical carboxylic acid mixtures, for example Versatic acid; sulfonic acids, for example methanesulfonic 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);

[0131] An organic phosphonic acid, for example a phosphonic acid of formula (IV):

[0132] R4-PO 3 H (IV)

[0133] Where R 4 is C optionally substituted with up to 4 substituents independently selected from carboxyl, amido, hydroxyl and amino 1-18 alkyl.

[0134] These include alkylphosphonic acids, for example methylphosphonic acid, propylphosphonic acid, 2-methylpropylphosphonic acid, tert-butylphosphonic acid, n-butylphosphonic acid, 2,3-dimethylbutylphosphonic acid, octylphosphonic acid; hydroxyalkylphosphonic acids, for example hydroxymethylphosphonic acid, 1-hydroxyethylphosphonic acid, 2-hydroxyethylphosphonic acid; arylphosphonic acids, for example phenylphosphonic acid, tolylphosphonic acid, xylylphosphonic acid; aminoalkylphosphonic acids, for example aminomethylphosphonic acid, 1-aminoethylphosphonic acid, 1-dimethylaminoethylphosphonic acid, 2-aminoethylphosphonic acid, 2-(N-methylamino)ethylphosphonic acid, 3-aminopropylphosphonic acid, 2-amino propylphosphonic 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; acylaminoalkylphosphonic acids, such as 3-hydroxymethylamino-3-oxopropylphosphonic acid; and phosphinocarboxylic acids, such as 2-hydroxyphosphinoacetic acid and 2-phosphinobutane-1,2,4-tricarboxylic acid;

[0135] Phosphonic acid of formula (V):

[0136]

[0137] Where R 5 H or C 1-5 Alkyl, Q is H, OH or NR 6 2 And R 6 H or CH 2 PO 3 H 2 , such as 1-hydroxyethane-1,1-diphosphonic acid;

[0138] Phosphonic acid of formula (VI):

[0139]

[0140] Where Z is C 2-5 Alkylene, cycloalkylene, phenylene, or C 2-5 Alkylene, Y is CH 2 PO 3 H 2 , and m is 0-4, such as ethylenediaminetetrakis(methylenephosphonic acid), diethylenetriaminepenta(methylenephosphonic acid) and bis(hexamethylene)triaminepenta(methylenephosphonic acid);

[0141] Phosphonic acid of formula (VII):

[0142] R7-NY 2 (VII)

[0143] Where R 7 C 1-5 Alkyl, C 2-5 Hydroxyalkyl or R 8 , and R 8 CH 2 PO 3 H 2 , such as nitrilotri(methylenephosphonic acid) and 2-hydroxyethyliminobis(methylenephosphonic acid);

[0144] Aminocarboxylic acids having a tertiary amino group or an amino group having at least one secondary or tertiary carbon atom adjacent to the amino group, for example:

[0145] α-amino acids having a tertiary amino group or an amino group having at least one secondary or tertiary carbon atom adjacent to the amino group, for example N,N-dimethylglycine (dimethylaminoacetic acid), N,N-diethylglycine, alanine (2-aminopropionic acid), N-methylalanine (2-(methylamino)propionic acid), N,N-dimethylalanine, N-ethylalanine, 2-methylalanine (2-aminoisobutyric acid), leucine (2-amino-4-methylpentane-1-oic acid), N-methylleucine, N,N-dimethylleucine, isoleucine (1-amino-2-methylpentaneic acid), N-methylisoleucine, N,N-dimethylisoleucine, valine (2-aminoisovaleric acid), α-methylvaline (2-amino-2-methylisovaleric acid), N-methylvaline ... 4-dimethylaminobutyric acid, N-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, a β-amino acid having a tertiary amino group or an amino group having at least one secondary or tertiary carbon atom adjacent to the amino group, for example 3-dimethylaminopropionic acid, N-methyliminodipropionic acid, N-methylpiperidine-3-carboxylic acid, a γ-amino acid having a tertiary amino group or an amino group having at least one secondary or tertiary carbon atom adjacent to the amino group, for example 4-dimethylaminobutyric acid, or an aminocarboxylic acid having a tertiary amino group or an amino group having at least one secondary or tertiary carbon atom adjacent to the amino group, for example N-methylpiperidine-4-carboxylic acid.

[0146] Among the inorganic acids, phosphoric acid and sulfuric acid are preferred, especially sulfuric acid.

[0147] Among the carboxylic acids, formic acid, acetic acid, benzoic acid, succinic acid and adipic acid are preferred.

[0148] Among the sulfonic acids, methanesulfonic acid, p-toluenesulfonic acid and 2-(4-(2-hydroxyethyl)-1-piperazinyl)ethanesulfonic acid (HEPES) are preferred.

[0149] Among the phosphonic acids, preference is given to 2-hydroxyphosphinoacetic acid, 2-phosphinobutane-1,2,4-tricarboxylic acid, 1-hydroxyethane-1,1-diphosphonic acid, ethylenediaminetetrakis(methylenephosphonic acid), diethylenetriaminepenta(methylenephosphonic acid), bis(hexamethylene)triaminepenta(methylenephosphonic acid) (HDTMP) and nitrilotris(methylenephosphonic acid), with 1-hydroxyethane-1,1-diphosphonic acid being particularly preferred.

[0150] Among the aminocarboxylic acids having a tertiary amino group or an amino group having at least one secondary or tertiary carbon atom adjacent to the amino group, N,N-dimethylglycine and N-methylalanine are preferred.

[0151] More preferably, the acid is an inorganic acid.

[0152] Non-aqueous organic solvents:

[0153] In one embodiment, the diluent of the absorbent comprises at least one non-aqueous organic solvent. In certain cases, the diluent comprises only a limited amount of water or is substantially free of water in addition to the non-aqueous organic solvent. It may be desirable to limit the water content of the absorbent to, for example, a maximum of 20 wt %, or a maximum of 10 wt %, preferably a maximum of 5 wt %, or a maximum of 2 wt %.

[0154] The non-aqueous organic solvent is preferably selected from:

[0155] C 4 -C 10 alcohols, such as n-butanol, n-pentanol, and n-hexanol;

[0156] Ketones, such as cyclohexanone;

[0157] Esters, such as ethyl acetate and butyl acetate;

[0158] lactones, such as γ-butyrolactone, δ-valerolactone, and ε-caprolactone;

[0159] Amides, for example tertiary amides, such as N,N-dimethylformamide; or N-formylmorpholine and N-acetylmorpholine;

[0160] lactams, such as γ-butyrolactam, δ-valerolactam and ε-caprolactam and N-methyl-2-pyrrolidone (NMP);

[0161] Sulfones, such as sulfolane;

[0162] Sulfoxides, such as dimethyl sulfoxide (DMSO);

[0163] glycols, such as ethylene glycol (EG) and propylene glycol;

[0164] Polyalkylene glycols, such as diethylene glycol (DEG) and triethylene glycol (TEG);

[0165] Two- or Single (C 1-4 alkyl ether) glycols, for example ethylene glycol dimethyl ether;

[0166] Two- or Single (C 1-4 alkyl ethers) polyalkylene glycols such as diethylene glycol dimethyl ether, dipropylene glycol monomethyl ether and triethylene glycol dimethyl ether;

[0167] Cyclic ureas, such as N,N-dimethylimidazolidin-2-one and dimethylpropylene urea (DMPU);

[0168] Thioalkanols, for example ethylenedithioethanol, thiodiethylene glycol (thiodiglycol, TDG) and methylthioethanol;

[0169] and mixtures thereof.

[0170] More preferably, the non-aqueous solvent is selected from sulfones, glycols and polyalkylene glycols. Most preferably, the non-aqueous solvent is selected from sulfones. The preferred non-aqueous solvent is sulfolane.

[0171] Other additives:

[0172] The absorbent may also contain additives such as corrosion inhibitors, enzymes, defoamers, etc. Generally, the amount of such additives is about 0.005% to 3% based on the total weight of the absorbent.

[0173] Purpose of absorbent:

[0174] The present invention also relates to the use of the absorbent described herein for removing acid gases from a fluid stream.

[0175] In one embodiment, the present invention relates to the use of the absorbent described herein for non-selective removal of acid gases from a fluid stream. In this case, it is preferred that the absorbent comprises at least one activator selected from non-hindered primary amines and / or non-hindered secondary amines as described above.

[0176] In another embodiment, the present invention relates to the use of an absorbent as described herein for selectively removing hydrogen sulfide from a fluid stream comprising carbon dioxide and hydrogen sulfide. In this case, it is preferred that the absorbent does not comprise any non-hindered primary or non-hindered secondary amines.

[0177] In one embodiment, the process is a process for the non-selective removal of acid gases from a fluid stream. In this case, it is preferred that the absorbent comprises at least one activator selected from non-hindered primary amines and / or non-hindered secondary amines as described above.

[0178] In another embodiment, the process is a process for selectively removing hydrogen sulfide from a fluid stream comprising carbon dioxide and hydrogen sulfide. In this case, it is preferred that the absorbent does not comprise any non-hindered primary amine or non-hindered secondary amine.

[0179] In the context of the present invention, "hydrogen sulfide selectivity" is understood to mean the value of the following quotient:

[0180] [mol(H 2 S) / mol(CO 2 )] 液相 / [mol(H 2 S) / mol(CO 2 )] 气相 Where [mol(H 2 S) / mol(CO 2 )] 液相 is the H in the liquid phase in contact with the gas phase 2 S / CO 2 molar ratio, and [mol(H 2 S) / mol(CO 2 )] 气相 is H in the gas phase 2 S / CO 2 Molar ratio.

[0181] In a standard gas scrubbing process, the liquid phase is the loaded absorbent in the bottom of the absorber and the gas phase is the fluid stream to be treated.

[0182] When the value of the above quotient is greater than 1, the method is understood as H 2 When the process is a process for the selective removal of hydrogen sulfide from a fluid stream comprising carbon dioxide and hydrogen sulfide, the hydrogen sulfide selectivity is preferably at least 1.1, even more preferably at least 2, most preferably at least 4.

[0183] The absorbents described herein are suitable for treating all kinds of fluids. The fluids are firstly gases, such as natural gas, synthesis gas, coke oven gas, cracked gas, coal gasification gas, recycle gas, landfill gas and combustion gas, and secondly liquids which are substantially immiscible with the absorbent, such as LPG (liquefied petroleum gas) or NGL (liquefied natural gas). The process according to the invention is particularly suitable for treating hydrocarbon-containing fluid streams. The hydrocarbons present are aliphatic hydrocarbons, such as C 1 -C 4 Hydrocarbons, such as methane, unsaturated hydrocarbons, such as ethylene or propylene, or aromatic hydrocarbons, such as benzene, toluene or xylene.

[0184] The absorbent of the present invention is suitable for removing acid gases, such as CO 2 , H 2 S. SO 3 、SO 2 , CS 2 , HCN, COS and mercaptans. Other acid gases may also be present in the fluid stream, such as COS and mercaptans.

[0185] The absorbent is suitable for selectively removing hydrogen sulfide from a fluid stream comprising carbon dioxide and hydrogen sulfide and allows high H 2 S removal selectivity. The absorbent is used in sulfur plant tail gas treatment unit (TGTU) applications, acid gas enrichment (AGE) processes to upgrade acid-depleted offgas from a processing unit to a higher quality Claus unit feed, or to treat associated and refinery gases.

[0186] In the process according to the invention, the fluid stream is brought into contact with an absorbent in an absorber in the absorption step, whereby carbon dioxide and hydrogen sulfide are at least partially scrubbed out. This results in a CO2-depleted 2 - and H 2 Fluid Flow and Loading CO 2 - and H 2 Absorbent of S.

[0187] The absorber used is a washing device used in conventional gas washing methods. Suitable washing devices are, for example, random packing, a tower with structured packing and a tower plate, a membrane contactor, a radial scrubber, a jet scrubber, a venturi scrubber and a rotary spray scrubber, preferably a tower with structured packing, a tower with random packing and a tower plate, more preferably a tower with a tower plate and a tower with random packing. The fluid stream is preferably treated with an absorbent in a countercurrent in the tower. The fluid is usually fed into the lower region, and the absorbent is fed into the upper region of the tower. Sieve plates, bubble plates or valve plates through which liquid flows are installed in the plate tower. The tower with random packing can be filled with different shaped bodies. Heat transfer and mass transfer are improved by increasing the surface area caused by the shaped body having a size of usually about 25-80 mm. Known examples are Raschig rings (hollow cylinders), ball rings, hallo rings, square saddle packings, etc. Random packing can be introduced into the tower in an orderly manner or randomly (as a bed). Possible materials include glass, ceramics, metals and plastics. Structured packings are a further development of ordered random packings. They have a regular structure. Therefore, the pressure drop in the gas flow can be reduced in the case of packings. There are various designs of structured packings, such as woven packings or sheet metal packings. The materials used can be metals, plastics, glass and ceramics.

[0188] The temperature of the absorbent in the absorption step is usually about 30-100°C, and when a column is used, for example, 30-70°C at the top of the column and 50-100°C at the bottom of the column.

[0189] The process according to the invention may comprise one or more, in particular two, consecutive absorption steps. The absorption may be carried out in a plurality of consecutive sub-steps, in which case the crude gas comprising the acid gas component is contacted with a substream of the absorbent in each sub-step. The absorbent contacted with the crude gas may already be partially loaded with acid gas, meaning that it may be, for example, absorbent recycled from a downstream absorption step to the first absorption step or partially regenerated absorbent. With regard to the performance of the two-stage absorption, reference is made to the publications EP 0 159 495, EP 0 190 434, EP 0 359 991 and WO 00100271.

[0190] One skilled in the art can achieve high levels of hydrogen sulfide removal at a given selectivity by varying the conditions in the absorption step, such as, more particularly, the absorbent / fluid stream ratio, the column height of the absorbent, the type of contact-promoting internals in the absorber, such as random packing, trays, or structured packing, and / or the residual loading of the regenerated absorbent.

[0191] Due to CO 2 H 2 S is absorbed more slowly, absorbing more CO at longer residence times than at shorter residence times 2 In contrast, at longer residence times, H 2 S selectivity decreases. Therefore, taller towers produce less selective absorption. Plates and structured packings with relatively high liquid retention also lead to less selective absorption. The heat 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.

[0192] The method preferably includes a regeneration step, wherein the CO 2 and H 2 S absorbent regeneration. In the regeneration step, CO 2 and H 2 S and optionally other acid gas components from the loaded CO 2 and H 2 S is released from the absorbent to obtain a regenerated absorbent. Preferably, the regenerated absorbent is then recycled to the absorption step. Generally speaking, the regeneration step includes at least one of heating, reducing pressure and stripping with an inert fluid.

[0193] The regeneration step preferably comprises heating the absorbent loaded with acid gas components, for example by means of a boiler, a natural circulation evaporator, a forced circulation evaporator or a forced circulation flash evaporator. The absorbed acid gas is stripped out by means of steam obtained by heating the solution. Instead of steam, an inert fluid, for example nitrogen, can also be used. The absolute pressure in the stripper is generally 0.1 to 3.5 bar, preferably 1.0 to 2.5 bar. The temperature is generally 50 to 170° C., preferably 80 to 130° C., the temperature of course depending on the pressure. In some cases, a further regeneration step of regenerating a slipstream of the absorption solvent is required. SO in the fluid stream x 、NO x In the presence of CO and CO, heat-stable salts such as sulfates, nitrates and formates may be formed. To reduce the concentration of these undesirable components, a further distillation step at elevated temperature may be applied, or alternatively the heat-stable salts may be removed by ion exchange methods.

[0194] Alternatively or additionally, the regeneration step may include a decompression. This includes at least one decompression of the loaded absorbent from the high pressure present during the absorption step to a lower pressure. The decompression may be achieved, for example, by means of a throttle valve and / or a decompression turbine. Regeneration with a decompression stage is described, for example, in publications US 4,537,753 and US 4,553,984.

[0195] The acid gas components may be released in a regeneration step, for example in a vacuum column, such as a vertically or horizontally mounted flash vessel, or a countercurrent column with internals.

[0196] The regeneration column can also be a column with random packing, with structured packing or with trays. At the bottom, the regeneration column has a heater, for example 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 recirculated to the column.

[0197] A plurality of vacuum towers can be connected in series, wherein the regeneration is carried out at different pressures. For example, the regeneration can be carried out at high pressure (usually about 1.5 bar above the partial pressure of the acid gas components in the absorption step) in the preliminary vacuum tower, and at low pressure (e.g. 1-2 bar absolute) in the main vacuum tower. Regeneration with two or more vacuum stages is described in publications US 4,537,753, US 4,553,984, EP 0 159 495, EP 0 202 600, EP 0 190 434 and EP 0 121 109.

[0198] The method of the present invention using the compound of formula (I) is used to treat a substance containing H 2 S and CO 2The process of the invention additionally allows high removal rates of mercaptans or other sulfur compounds that may be present in such gaseous streams. The compounds of formula (i) show high thermal stability, allowing regeneration at higher temperatures and more complete regeneration of the absorbent solution at lower loading factors.

[0199] The present invention is described in detail by the following examples.

[0200] Example 1: Preparation of 2-[2-(tert-butylamino)ethylthio]ethanol.

[0201] 1,7 sodium methylate was dissolved in 15 ml of anhydrous ethanol. Mercaptoethanol was added to the solution under stirring. After the mixing was completed, the mixture was stirred for another 15 minutes, and a solution of 2.5 g of 2-chloro-N-tert-butylethylamine hydrochloride dissolved in 50 ml of anhydrous ethanol was added dropwise to maintain the temperature in the range of 35-40°C. After the mixing process was completed, the resulting suspension was heated to 75°C and stirred for another 90 minutes. After stirring at room temperature overnight, the suspension was filtered and the filtrate was evaporated in a rotary evaporator at 90°C and 60 mbar.

[0202] 2.5 g of 2-[2-(tert-butylamino)ethylthio]ethanol was obtained with a yield of 97%. The structure of the compound is given by 1 H-NMR confirmed.

[0203] Example 2: Performance comparison of 2-[2-(tert-butylamino)ethylthio]ethanol (TBAESE) and 2-[2-(tert-butylamino)ethoxy]ethanol (TBAEE)

[0204] a) Thermal stability

[0205] The thermal stability of TBAESE was compared with that of TBAEE and MDEA with and without acid gas loading.

[0206] Initially, the corresponding solution (8 mL) was added to a cylinder (10 mL) and the cylinder was sealed. The cylinder was heated to 150 °C and maintained for 125 h. In the experiments conducted under acid gas loading, the acid gas loading of the solution was 20 Nm 3 / ton 溶剂 CO 2 and 20Nm 3 / ton 溶剂 H 2 The decomposition level of S. amine was calculated from the amine concentration measured by gas chromatography before and after the experiment. The results are shown in Table 1.

[0207] Table 1:

[0208]

[0209] *Comparative ratio

[0210] It is clear that TBAESE has a higher thermal stability in aqueous solution than MDEA and TBAEE in the presence of acid gas loading.

[0211] b) Acid gas loading and regeneration

[0212] The pKa values ​​of TBAESE and TBAEE were measured in the temperature range of 20-120°C. The results are shown in Figure 1 For this purpose, an aqueous amine solution with a concentration of 0.01 mol / l is neutralized by 50% with a 0.005 mol / l HCl solution. The measured pH value of the neutralized 50% amine solution is therefore equal to the pKa value of the amine.

[0213] The measurements were performed in a glass vessel pressurized with nitrogen to avoid any loss of water and solvent.

[0214] It can be seen that the pKa values ​​of TBAESE and TBAEE are comparable within the measured range and are significantly higher than the pKa value of MDEA. From these measurements, it can be concluded that the acid gas loading and regeneration of TBAESE is comparable to that of TBAEE.

[0215] In summary, although TBAESE and TBAEE have similar absorption performance, TBAESE shows slightly improved thermal stability. This allows TBAESE to be processed at slightly higher regeneration temperatures, resulting in more complete regeneration of the absorbent.

[0216] Furthermore, TBAESE combines in one molecule the benefits of hindered amines such as high selectivity for H2S and high removal of mercaptans, other sulfur compounds that may be present in the feed gas, especially mercaptans.

Claims

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

2. The method according to claim 1, wherein R1, R2 and R3 are each C1 alkyl.

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

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

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

6. The method of claim 2, wherein the diluent comprises water.

7. The method of claim 3, wherein the diluent comprises water.

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

9. The process according to claim 5, wherein the absorbent additionally comprises an acid.

10. The process according to claim 6, wherein the absorbent additionally comprises an acid.

11. The process according to claim 7, wherein the absorbent additionally comprises an acid.

12. The process according to claim 8, wherein the absorbent additionally comprises an acid.

13. A method according to any one of claims 1 to 12, wherein the diluent comprises a non-aqueous organic solvent.

14. The method according to claim 13, wherein the organic solvent is selected from C 4-10 Alcohols, ketones, esters, amides, sulfones, sulfoxides, glycols, cyclic ureas, thioalkanols and mixtures thereof.

15. The process according to claim 13, wherein the organic solvent is selected from lactones.

16. The process according to claim 13, wherein the organic solvent is selected from lactams.

17. The method according to claim 13, wherein the organic solvent is selected from polyalkylene glycols.

18. The process according to claim 13, wherein the organic solvent is selected from di- or mono-(C1-C4 alkyl ether) glycols.

19. The method according to claim 13, wherein the organic solvent is selected from di- or mono-(C 1-4 Alkyl ether) polyalkylene glycol.

20. The process according to any one of claims 1 to 12, wherein the absorbent comprises at least one activator selected from non-hindered primary amines and / or non-hindered secondary amines.

21. The process according to any one of claims 14 to 19, wherein the absorbent comprises at least one activator selected from non-hindered primary amines and / or non-hindered secondary amines.

22. The method of claim 20, wherein the activator is piperazine.

23. The method of claim 21, wherein the activator is piperazine.

24. The process according to any one of claims 1 to 12 for selectively removing hydrogen sulfide from a fluid stream comprising carbon dioxide and hydrogen sulfide.

25. A process according to any one of claims 14 to 19 for selectively removing hydrogen sulfide from a fluid stream comprising carbon dioxide and hydrogen sulfide.

26. The process according to any one of claims 1 to 12, wherein the loaded absorbent is regenerated by at least one of heating, reducing pressure and stripping with an inert fluid.

27. The process according to claim 22 or 23, wherein the loaded absorbent is regenerated by at least one of heating, reducing pressure and stripping with an inert fluid.

28. The process of claim 25, wherein the loaded absorbent is regenerated by at least one of heating, reducing pressure, and stripping with an inert fluid.

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