FR3014328A1 - ABSORBENT SOLUTION BASED ON N, N, N ', N'-TETRAMETHYL-1,6-HEXANEDIAMINE AND A SECONDARY DIAMINE OF THE ALKYLPIPERAZINE FAMILY AND METHOD FOR REMOVING ACIDIC COMPOUNDS FROM A GASEOUS EFFLUENT - Google Patents

Abstract

The invention relates to the removal of acidic compounds in a gaseous effluent in an absorption process using an aqueous solution of N, N, N ', N'-Tetramethyl-1,6-hexanediamine formulated with a particular secondary diamine of the family of alkylpiperazines, for obtaining a monophasic absorbent solution under the acid gas absorption conditions such as CO2. The invention is advantageously applicable to the treatment of natural gas and gas of industrial origin.

Description

Field of the Invention The present invention relates to the absorption of acidic compounds (H2S, 002, COS, CS2, mercaptans, ...) contained in a gas by means of an aqueous absorbing solution comprising the combination of a diamine tertiary, N, N, N ', N'-tetramethyl-1, 6-hexanediamine, and a particular secondary diamine, to obtain a monophasic absorbent solution under the acid gas absorption conditions such as the 002. The invention is advantageously applicable to the treatment of natural gas and gas of industrial origin.

PRIOR ART Treatment of gases of industrial origin The nature of the gaseous effluents that can be treated is diverse. Non-limiting examples include synthesis gases, combustion fumes, refinery gases, bottoms gases from the Claus process, biomass fermentation gases, cement gases and blast furnace gases. . All these gases contain acidic compounds such as carbon dioxide (002), hydrogen sulphide (H2S), carbon oxysulphide (COS), carbon disulfide (CS2) and mercaptans (RSH), mainly carbon dioxide. methyl mercaptan (CH3SH), ethyl mercaptan (CH3CH2SH) and propyl mercaptans (CH3CH2CH2SH). For example, in the case of combustion fumes, CO2 is the acid compound that is to be removed. Indeed, CO2 is one of the greenhouse gases largely produced by different human activities and has a direct impact on air pollution. In order to reduce the amount of CO2 emitted into the atmosphere, it is possible to capture the CO2 contained in a gaseous effluent. Natural gas processing In the case of natural gas, three main treatment operations are considered: deacidification, dehydration and degassing. The first step, which is deacidification, is aimed at the removal of acidic compounds such as 002, but also H2S, COS, CS2 and mercaptans (RSH), mainly methyl mercaptan (CH3SH). ethyl mercaptan (CH3CH2SH) and propyl mercaptans (CH3CH2CH2SH and CH3CH (CH3) SH). The generally accepted specifications for the deacidified gas are 2% of 002, or even 50 ppm of CO2, to then liquefy the natural gas; 4 ppm H2S, and 10 ppm to 50 ppm total sulfur. The dehydration step then controls the water content of the deacidified gas against transport specifications. Finally, the degassing stage of natural gas ensures the dew point of hydrocarbons in natural gas, again depending on transport specifications.

Deacidification is therefore often carried out first, in particular in order to eliminate toxic acid gases such as H 2 S in the first stage of the process chain and to avoid the pollution of the different unit operations by these acidic compounds, in particular the dehydration section and the heavier hydrocarbons condensation and separation section. Elimination of acidic compounds by absorption The deacidification of gaseous effluents, such as for example natural gas and combustion fumes, as well as synthesis gases, refinery gases, gases obtained at the bottom of the Claus process, fermentation gases Biomass, cement and high blast furnace gases are generally carried out by washing with an absorbent solution. The absorbent solution makes it possible to absorb the acid compounds present in the gaseous effluent (in particular H 2 S, mercaptans, O 2, COS, CS 2). The solvents commonly used today are aqueous solutions of primary, secondary or tertiary alkanolamine, in combination with a possible physical solvent. For example, document FR 2 820 430 can be cited which proposes processes for deacidification of gaseous effluents. For example, US Pat. No. 6,852,144 describes a method for removing acidic compounds from hydrocarbons. The method uses a water-methyldiethanolamine or water-triethanolamine absorbent solution containing a high proportion of a compound belonging to the following group: piperazine and / or methylpiperazine and / or morpholine. For example, in the case of the capture of 002, the absorbed CO2 reacts with the amine present in solution according to a reversible exothermic reaction, well known to those skilled in the art and leading to the formation of hydrogenocarbonates, carbonates and / or carbamates, allowing removal of CO2 in the gas to be treated. Similarly, for the removal of H2S in the gas to be treated, the absorbed H2S reacts with the amine present in solution according to a reversible exothermic reaction, well known to those skilled in the art and leading to the formation of hydrosulfide. Another essential aspect of industrial solvent gas or flue gas treatment operations is the regeneration step of the separating agent. Depending on the type of absorption (physical and / or chemical), regeneration by expansion, and / or distillation and / or entrainment by a vaporized gas called "stripping gas" is generally envisaged. One of the main limitations of the solvents commonly used today is the need to implement large absorbent solution flow rates, which results in significant energy consumption for the regeneration of the solvent, but also important equipment sizes (columns, pumps, etc.). This is particularly true in the case where the partial pressure of acid gases is low. For example, for an aqueous solution of MonoEthanolAmine at 30% by weight used for the capture of CO2 in post-combustion in a thermal power station smoke, where the partial pressure of CO2 is of the order of 0.1 bar, the energy of regeneration represents about 3.9 GJ per tonne of CO2 captured (reference case, CASTOR project, post-combustion capture pilot of the Esbjerg thermal power plant). Such energy consumption represents a considerable operating cost for the capture process of 002. In general, for the treatment of acid effluents comprising acidic compounds such as, for example, H 2 S, mercaptans, O 2, COS, SO 2, CS 2, The use of amine-based compounds is interesting because of their ease of use in aqueous solution. However, during the deacidification of these effluents, the absorbent solution can degrade, either by thermal degradation or by secondary reaction with the acid gases to be captured, but also with other compounds contained in the effluent, such as, for example, oxygen, SOx and NOx, contained in industrial fumes.

These degradation reactions are detrimental to the proper functioning of the process: decreased solvent efficiency, corrosion, foaming, etc. Due to these degradations, it is necessary to carry out a purification of the solvent by distillation and / or ion exchange, and to make amine bonds. By way of example, amine bonds in a post-combustion CO 2 capture process, using a 30% by weight absorbing solution of MonoEthanolAmine, represent 1.4 kg of amine per tonne of CO2 captured, which increases considerably the operating costs of a catchment unit. It is difficult to find a stable absorbent compound to remove acidic compounds in any type of effluent, and allow the deacidification process to operate at a lower cost. FR 2 934 172 discloses that N, N, U, N, N-tetramethyl-1,6-hexanediamine (TMHDA), alone or in mixture with a few weight percentages of primary or secondary amines, is of great interest in all processes for treating gaseous effluents for the removal of acidic compounds.

Nevertheless, most of the aqueous absorbent solutions comprising TMHDA, alone or mixed with a few weight percentages of primary or secondary amines, exhibit a liquid-liquid phase separation during the absorption of CO2 under the conditions of the absorber, also called demixing phenomenon in the present description. In the form of two separate phases, the flow of acidic compounds transferred from the gas to the absorbent solution is strongly impacted and the column height must be adapted accordingly. This phenomenon therefore poses implementation difficulties, and given the complexity of the system, is difficult to model. Surprisingly, the Applicant has demonstrated that the addition of a few percentages by weight of particular secondary diamines to an aqueous solution of TMHDA makes it possible to obtain a monophasic absorbent solution under the acid gas absorption conditions such as 002. DESCRIPTION OF THE INVENTION The object of the present invention is to overcome one or more of the disadvantages of the prior art by proposing a method for eliminating acid compounds, such as 002, H2S, COS, CS2 and mercaptans. of a gas employing an aqueous absorbent solution comprising the combination of two specific amines whose properties make it possible, while maintaining a monophasic absorbent solution under the acid gas absorption conditions, to limit the flow of absorbent solution to be used , in particular at low partial pressure of acid gas, and which have a very high stability. A first subject of the invention is an aqueous absorbent solution comprising the combination of N, N, N ', N'-tetramethyl-1,6-hexanediamine (TMHDA) of formula (I) and an activator of general formula (II) or (III). The present invention also relates to a process for the removal of acidic compounds contained in a gaseous effluent, such as natural gas and gases of industrial origin, comprising: a step of absorption of the acidic compounds by contacting the effluent with an aqueous solution comprising TMHDA and an activator of general formula (II) or (III). optionally at least one liquid-liquid separation step of the solution charged with acid gas after heating, allowing a fractional regeneration of the absorbent solution. at least one regeneration step of the absorbent solution loaded with acidic compounds. The invention also relates to the application of said process for the elimination of acidic compounds to the treatment of natural gas or to the treatment of gas of industrial origin, in particular to the capture of 002 after combustion. SUMMARY OF THE INVENTION The invention relates to an absorbent solution for absorbing acidic compounds from a gaseous effluent, comprising: - water; - N, N, N ', N'-tetramethyl-1, 6-hexanediamine of formula (I) \ NN \ (I) at least one activator compound selected from secondary diamines corresponding to one of the general formulas ( II) or (III).

By secondary diamine is meant an amine comprising two amine functions and at least one of the two amine functions is a secondary amine function. The diamines according to the general formulas (II) and (III) have two secondary amine functions. According to the invention, the general formula (II) is of the form: ## STR2 ## in which: the group R 1 is chosen from one of the elements of the group consisting of: a hydrogen atom and an alkyl group of 1 at 12 carbon atoms, the group R2 is chosen from one of the group consisting of: an alkyl group of 4 to 16 carbon atoms and a phenyl group. According to the invention, the general formula (III) is of the form: H \ / R4 / N / H in which: the group R3 is chosen from one of the elements of the group consisting of: a hydrogen atom and an alkyl group of 1 to 12 carbon atoms, the group R4 is chosen from one of the group consisting of: an alkyl group of 4 to 16 carbon atoms and a phenyl group.

The absorbent solution advantageously comprises: from 10% to 90% by weight, preferably from 20% to 60% by weight, of TMHDA, a non-zero quantity and less than 50% by weight, preferably less than 30% by weight, of less an activator compound according to the general formula (II) or (III), and - from 10% to 90% by weight, preferably from 50% to 70% by weight, of water According to one embodiment, the absorbent solution comprises at least at least one mixture of at least one activator according to general formula (II) and at least one activator according to general formula (III). According to one embodiment of the absorbent solution, the activator compound corresponds to the general formula (III) and the group R 3 is either an alkyl group of 1 to 12 carbon atoms or a hydrogen atom provided that the group R 4 is an alkyl group of 8 to 16 carbon atoms or a phenyl group. According to one embodiment of the absorbent solution, the activator compound is of general formula (II) and the group R 1 is either an alkyl group of 1 to 12 carbon atoms or a hydrogen atom, provided that the group R2 either an alkyl group of 8 to 16 carbon atoms or a phenyl group. According to a preferred embodiment, the absorbent solution contains at least one activator corresponding to the general formula (II) and chosen from the group formed by: 2-butylpiperazine of the following formula H H; and 2-Hexylpiperazine of the following formula: According to another preferred embodiment, the absorbent solution contains at least one activator corresponding to the general formula (II) and chosen from the group formed by: 2-Phenylpiperazine of the following formula: HN 7 NH - 2-Octylpiperazine of the following formula: H / NN / H; and 2-Decylpiperazine of the following formula: According to another preferred embodiment, the absorbent solution comprises a mixture of a first activator according to general formula (II) and d). a second activator corresponding to the general formula (III), the mixture being selected from the group of mixtures consisting of: 2-methyl-5-n-butylpiperazine (corresponding to the general formula III) and 2-methyl- 6-nbutylpiperazine (having the general formula II) of the respective formulas: HHNNNNHH; and 2-methyl-5-n-octyl-piperazine (corresponding to the general formula III) and 2-methyl-6-n-octyl-piperazine (corresponding to the general formula II) of the respective formulas: HN / NH According to one embodiment, the absorbent solution comprises, in addition to at least one additional activator compound comprising a primary or secondary amine function, preferably in an amount of less than 15% by weight of the absorbent solution, selected from the group consisting of: monoethanolamine; diethanolamine; N-butylethanolamine; aminoethylethanolamine; diglycolamine; piperazine; 1-methyl-piperazine; 2-methylpiperazine; homopiperazine; N- (2-hydroxyethyl) piperazine; N- (2-aminoethyl) piperazine; morpholine; 3- (methylamino) propylamine; 1,6-hexanediamine; N, N'-dimethyl-1,6-hexanediamine; N-methyl-1,6-hexanediamine; N, N ', N'-trimethyl-1,6-hexanediamine. The invention also relates to a process for eliminating the acidic compounds contained in a gaseous effluent, in which is carried out: a step of absorption of the acidic compounds by contacting the effluent with an absorbent solution according to the invention of in order to obtain a gaseous effluent depleted in acidic compounds and an absorbent solution loaded with acid compounds, - then a regeneration step in which at least a portion of the solution charged with acidic compounds is sent to a distillation column to release the acidic compounds. in the form of a gaseous effluent and obtain a regenerated absorbent solution The absorption step is advantageously carried out so as to obtain a gaseous effluent depleted of acidic compounds and an absorbent solution loaded with monophasic acidic compounds.

In general, the absorption step of the acidic compounds is carried out at a pressure of between 1 bar and 120 bar, and at a temperature of between 20 ° C. and 100 ° C., preferably between 30 ° C. and 95 ° C. C, and the thermal regeneration step is carried out at a pressure between 1 bar and 10 bar and at a temperature between 100 ° C and 180 ° C.

In one embodiment of the process according to the invention, the absorption step is followed by at least one liquid-liquid separation step of the absorbent solution loaded with two-phase acidic compounds obtained after heating the absorbent solution, followed by at least one step of fractional regeneration of the absorbent solution loaded with acidic compounds. The invention also relates to a process according to the invention for the treatment of natural gas. The invention also relates to a process according to the invention for the treatment of gases of industrial origin, preferably for the capture of 002. Other features and advantages of the invention will be better understood and will be clearly apparent on reading. DETAILED DESCRIPTION BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 represents a schematic diagram of a process for treating acid gas effluents. FIG. 2 represents a schematic diagram of a process for treating acid gas effluents with fractional regeneration by heating. DETAILED DESCRIPTION OF THE INVENTION The present invention proposes to remove acidic compounds from a gaseous effluent by using the combination of at least two types of amine compounds in aqueous solution. The absorbent solution is an aqueous solution based on TMHDA, which has the property of reacting reversibly with acid compounds, such as H2S and 002. The TMHDA in aqueous phase, has the property of forming two liquid phases separable when it has absorbed a certain quantity of acidic compounds (demixing phenomenon), such as 002. In other words, the aqueous solution of TMHDA forms two liquid phases when its charge rate (number of moles of acidic compounds) absorbed by one mole of amine of the absorbent solution) exceeds a demixing critical load rate, i.e., a loading rate threshold. When placed in contact in the absorption column, the loading rate of the absorbent solution increases as the acid compounds contained in the gas are absorbed. When introducing the aqueous solution of TMHDA into the absorption column, the solution is monophasic. In the absorption column, the loading rate of the absorbent solution may exceed the critical demixing loading rate and the absorbing solution may separate into two phases. In the form of two separate phases, the flow of acidic compounds transferred from the gas to the solution would be strongly impacted and the column height should be adapted accordingly. This phenomenon therefore poses significant problems of implementation, and given the complexity of the system, is difficult to model. In order to maintain the monophasic absorbent solution in the absorption column, the present invention proposes mixing the TMHDA with specific activators which have the property of eliminating the demixing phenomenon by raising the loading rate to 002.

By activator compound is meant a compound that accelerates the absorption kinetics of the CO2 contained in the gas to be treated. The composition of the absorbent solution according to the invention is detailed later in the description. The aqueous compositions based on TMHDA activated by a secondary diamine of general formula (II) or (III) are of interest as an absorbent solution in all acid gas treatment processes (natural gas, combustion fumes, etc. .).

TMHDA has a greater absorption capacity with acid gases (002, H2S, COS, SO2, CS2 and mercaptans) than the alkanolamines conventionally used. Indeed, the TMHDA has the particularity of having very high feed rates (a = ngaz acid / namine) at low partial pressures of acid gas, compared with the alkanolamines conventionally used.

The addition of a few weight percentages of a secondary diamine of formula (II) to an aqueous solution of TMHDA only slightly modifies the filler levels obtained, particularly at a low partial pressure of acid gas. The use of an aqueous absorbent solution according to the invention therefore saves on the investment cost and the operating costs of a deacidification unit (gas treatment and capture of 002).

In addition, the TMHDA molecule is interesting for its resistance to degradation, especially thermal and in the presence of oxygen. Therefore, it is possible to regenerate the solvent at a higher temperature and thus to obtain an acid gas at higher pressure if this is of interest in the case of reinjection of acid gas. This is particularly interesting in the case of post-combustion CO2 capture where the gas to be treated contains oxygen and where acid gas must be compressed before reinjection and sequestration. The addition of a few weight percent of a secondary diamine of general formula (II) does not change this conclusion because, given its low concentration, the rate of degradation of this molecule is slow. Furthermore, the secondary diamines of general formula (II) and (III) are also interesting for their resistance to degradation, especially in the presence of oxygen. The use of an aqueous absorbent solution according to the invention makes it possible to save on the operating costs of the deacidification unit, and on the investment cost and the operating costs associated with the compression of the acid gas.

Furthermore, the aqueous solutions of TMHDA activated by a secondary diamine of general formula (II) or (III) have the particularity of being able to be implemented in a deacidification process, with fractional regeneration by heating as described in the document The addition of a small amount of secondary diamines of general formula (II) or (III) to an aqueous solution of TMHDA makes it possible to control the phenomenon of demixing of the solution during the process. This makes it possible to obtain a monophasic absorbent solution under the acid gas absorption conditions such as CO2, and to obtain a phase separation at the outlet of the charge-effluent exchanger if this is desired. Synthesis of N, N, 1 ', N-tetramethyl-1,6-hexanediamine TMHDA can be prepared according to various synthetic routes known to those skilled in the art, described for example in JP 1998- 341556, EP 1998-105636, JP 1994-286224, JP 1993-25241, EP 1993-118476, EP 1988-309343, JP 1986-124298, JP 1985-147734, DE 19853523074, JP 1983-238221, and JP 1983-234589. . The reactions described in these documents are generally catalytic, with various catalyst compositions, for example platinum, palladium, rhodium, ruthenium, copper, nickel or cobalt derivatives. Some of these pathways identified from basic chemicals are shown below, noting generically [Cat.] The use of a catalyst.

HOOH ^ NH + NH + H2O N + H + H2O 100-250 ° C H2 1-5 bar I 12 [Cat.] 100-200 ° C [Cat.] H [Cat.] H2N NH2 H 60-200 ° C H2 3-50 bar I H2 ° [Cat.] + -OH H2N 130 ° C H2 50 bar + H2O ^ NH [Cat.] -I- NH3 50-250 ° C H2 5-350 bar Synthesis of alkylpiperazines of the general formula (II) or (III) The secondary diamines of the general formulas (II) and (III) are 2-alkylpiperazines or 2-phenylpiperazines or 2,5-dialkylpiperazines or 2-alkyl-5-phenylpiperazines or 2-alkylpiperazines , 6-dialkylpiperazines or 2-alkyl-6-phenylpiperazines. They can be synthesized by any means allowed by organic chemistry.

By way of example, mention may be made of the reduction by hydrogenation of the corresponding pyrazines. A preferred method is the addition of an epoxide and a 1,2-diaminoalkyl, both amine functional groups are primary, usually in excess, both judiciously selected. This addition reaction leads to variously substituted N- (aminoethyl) ethanolamine structures. In a second step, the addition products thus obtained are cyclized to piperazines. These cyclizations are generally carried out in the presence of hydrogen and a catalyst. The cyclization reaction generates a molecule of water. There are many catalysts well known to those skilled in the art for performing this reaction. Among these, without being exhaustive, mention will be made of derivatives of platinum, palladium, copper, nickel such as Raney nickel.

The general scheme shown below illustrates this synthetic route applied to the molecules of the invention with either R being selected from an alkyl group of 4 to 16 carbon atoms or a phenyl group and R 'being selected from a hydrogen atom or an alkyl group of 1 to 12 carbon atoms, wherein R 'is selected from an alkyl group of 4 to 16 carbon atoms or a phenyl group and R is selected from a hydrogen atom or an alkyl group of 1 to 12 carbon atoms. Depending on the amine function and the epoxide site that will react, it is possible to obtain up to 4 different adducts. In general, the steric effect is predominant and the amine function will mainly react on the less congested carbon atom of the epoxide. The cyclization reactions of the 4 products of possible additions lead to piperazines which can respond to the two general formulas (II) and (III). ## STR2 ## wherein R 2 is NH 2 OH 2 NH 2 + NH 2 + NH 2 + NH 2 R 'eN 2 OH 2 chia% HD, RH Nature of gaseous effluents The absorbent solutions according to the invention can be used to deacidify the following gaseous effluents: natural gas, synthesis gases, combustion fumes, refinery gases, gases obtained at the bottom of the Claus process, biomass fermentation gases, cement gases, incinerator fumes. These gaseous effluents contain one or more of the following acidic compounds: 002, I.H2S, mercaptans, COS, CS2.

The combustion fumes are produced in particular by the combustion of hydrocarbons, biogas, coal in a boiler or for a combustion gas turbine, for example for the purpose of producing electricity. These fumes have a temperature of between 20 ° C. and 60 ° C., a pressure of between 1 bar and 5 bar and may comprise between 50% and 80% of nitrogen, between 5% and 40% of carbon dioxide, between 1 and 5 bar. % and 20% oxygen, and some impurities such as SOx and NOx, if they have not been removed downstream of the deacidification process.

Natural gas consists mainly of gaseous hydrocarbons, but can contain several of the following acidic compounds: CO2, H2S, mercaptans, COS, CS2. The content of these acidic compounds is very variable and can be up to 40% for CO2 and H2S. The temperature of the natural gas can be between 20 ° C and 100 ° C. The pressure of the natural gas to be treated may be between 10 bar and 120 bar. Composition of the absorbent aqueous solution The TMHDA may be in variable concentration, for example between 10% and 90% by weight, preferably between 20% and 60% by weight, very preferably between 30% and 50% by weight, in the aqueous solution. , terminals included. The activator compounds of general formula (II) or (III) have a non-zero concentration, for example less than 50% by weight, or even less than 30% by weight, preferably less than 20% by weight, very preferably less than 10% by weight, in the aqueous solution, limits included.

Preferably, the absorbent solution comprises at least 0.5% by weight of the activator compound (s) of general formula (II) or (III), preferably at least 1%. The sum of the mass fractions expressed in% by weight of the various compounds of the absorbent solution is equal to 100% by weight of the absorbent solution.

A non-exhaustive list of activator compounds of the general formula (II) is given below: 2-n-butylpiperazine; 2-n-hexyl-piperazine; 2-phenylpiperazine; 2-n-octyl-piperazine; 2-n-decyl-piperazine; 2-methyl-6-n-butylpiperazine; 2-méthy1-6-n-octylpipérazine.

Preferably, the absorbent solution comprises an activator compound corresponding to the general formula (II) which is chosen such that the R 1 group is: an alkyl group of 1 to 12 carbon atoms, or - a hydrogen atom provided that the R2 group is an alkyl group of 8 to 16 carbon atoms or a phenyl group. This is the case, for example, with 2-phenylpiperazine, 2-n-octylpiperazine and 2-n-decylpiperazine compounds.

Preferably, the absorbent solution comprises an activator compound corresponding to the general formula (III) which is chosen such that the R 3 group is: an alkyl group of 1 to 12 carbon atoms, or a hydrogen atom provided that the group R4 is an alkyl group of 8 to 16 carbon atoms or a phenyl group. A non-exhaustive list of activator compounds of general formula (III) is given below: 2-methyl-5-n-butylpiperazine; 10 - 2-methyl-5-n-octylpiperazine. The absorbent solution may comprise at least one mixture of one or more diamines corresponding to the general formula (II) and one or more diamines corresponding to the general formula (III). Among these mixtures, the compounds of the following compounds may be non-exhaustively mentioned: 2-methyl-5-n-butylpiperazine, corresponding to the general formula (III), with 2-methyl-6-n-butylpiperazine, in the general formula (II). 2-methyl-5-n-octylpiperazine, corresponding to the general formula (III), with 2-methyl-6-noctylpiperazine, corresponding to the general formula (II). The absorbent solution may contain at least 10% by weight of water, in general between 10% and 90% by weight of water, very preferably between 50% by weight and 70% by weight of water, for example between 55% to 50% by weight. 69% weight of water. In a very preferred mode, the absorbent solution according to the invention contains from 55% to 69% by weight of water, from 31% to 45% by weight of amines comprising TMHDA in admixture with at least one secondary diamine of formula general (II) or (III) as an activator, the activator representing between 1% and 10% by weight of the final absorbent solution. In one embodiment, the absorbent solution according to the invention may contain, in addition to TMHDA and at least one diamine of general formula (II) or (III), an activator compound containing at least one primary amine function. or secondary, selected from the group consisting of: monoethanolamine; Diethanolamine; N-butylethanolamine; aminoethylethanolamine; diglycolamine; piperazine; 1-methyl-piperazine; 2-methylpiperazine; homopiperazine; N- (2-hydroxyethyl) piperazine; N- (2-aminoethyl) piperazine; morpholine; 3- (methylamino) propylamine; 1,6-hexanediamine; N, N'-dimethyl-1,6-hexanediamine; N-methyl-1,6-hexanediamine; N, N ', N'-trimethyl-1,6-hexanediamine. For example, the absorbent solution comprises between 0.5% and up to a concentration of 15% by weight, preferably less than 10% by weight, preferably less than 5% by weight of said activator compound chosen from the list above, included. Absorbent solutions according to the invention are particularly interesting in the case of the capture of CO2 in industrial fumes, or the treatment of natural gas containing CO2 above the desired specification. Indeed, for this type of application, it is sought to increase the kinetics of 002 capture, in order to reduce the height of the absorption columns. In one embodiment, the absorbent solution based on TMHDA activated by a secondary diamine of general formula (II) or (III) may also comprise other organic compounds, non-reactive with respect to acidic compounds (commonly referred to as "solvents"). 25), which make it possible to increase the solubility of at least one or more acidic compounds of the gaseous effluent. For example, the absorbent solution may comprise between 5% and 50% by weight of physical solvent such as alcohols, glycol ethers, lactams, N-alkylated pyrrolidones, N-alkylated piperidones, cyclotetramethylenesulfone, N-alkylformamides, N-alkylacetamides, ethers-ketones or alkyl phosphates and their derivatives. By way of example and without limitation, it may be methanol, tetraethyleneglycoldimethylether, sulfolane or N-formyl morpholine. Process for removing acidic compounds in a gaseous effluent (FIG 1) The implementation of an absorbent solution for deacidifying a gaseous effluent is carried out schematically by performing an absorption step followed by a regeneration step . The absorption step consists of contacting the gaseous effluent containing the acidic compounds to be removed with the absorbing solution in a Cl absorption column. The gaseous effluent to be treated (1) and the absorbing solution (4) feed Column Cl. Upon contact, the organic compounds provided with an amine function of the absorbent solution (4) react with the acidic compounds contained in the effluent (1) so as to obtain a gaseous effluent depleted in acidic compounds (2). ) which leaves at the top of column C1 and an acid-enriched absorbent solution (3) which leaves at the bottom of column C1. The absorbent solution enriched in acidic compounds (3) is sent to an exchanger E1, where it is heated by the stream (6) from the regeneration column C2. The absorbent solution charged and heated at the outlet of the exchanger E1 (5) feeds the distillation column (or regeneration column) C2 in which the regeneration of the absorbent solution loaded with acidic compounds takes place. The regeneration step therefore consists in particular in heating and, optionally, expanding, the absorbent solution enriched in acidic compounds in order to release the acidic compounds which come out at the top of column C2 in gaseous form (7). The regenerated absorbent solution, that is to say depleted in acidic compounds (6), leaves at the bottom of the column C2, then passes into the exchanger E1, in which it gives heat to the flow (3) as previously described. . The regenerated and cooled absorbent solution (4) is then recycled to the absorption column C1.

The absorption step of the acidic compounds can be carried out at a pressure of between 1 bar and 120 bar, preferably between 20 bar and 100 bar for the treatment of a natural gas, preferably between 1 bar and 3 bar for treatment of industrial fumes, and at a temperature between 20 ° C and 100 ° C, preferably between 30 ° C and 95 ° C, more preferably between 30 ° C and 90 ° C, more preferably between 30 ° C C and 80 ° C, even more preferably between 30 ° C and 70 ° C, or even between 30 ° C and 60 ° C. Indeed, the process according to the invention has an excellent capacity of absorption of acidic compounds when the temperature in the absorption column Cl is between 30 ° C and 60 ° C. Generally, the temperature varies in the absorber as a function of the temperature of the introduced fluids and the exothermicity of the reactions. The temperature of the absorbent solution supplying the absorber is such that the solution is monophasic on arrival at the absorber head. It is preferably strictly less than 60 ° C, and still more preferably less than 55 ° C.

The regeneration step of the process according to the invention can be carried out by thermal regeneration, optionally supplemented by one or more expansion steps. It is possible to carry out, before the regeneration step, a first step of relaxing the absorbent solution loaded with acidic compounds. It is also possible to perform a second expansion step of the absorbent solution loaded with acid compounds, the second expansion step being carried out after the first expansion step and before the regeneration step, the absorbent solution being heated before undergoing the second step of relaxation.

Given the high stability of the TMHDA, it is possible to regenerate the absorbent solution according to the invention at high temperature in a distillation column. In general, the thermal regeneration step is carried out at a temperature of between 100 ° C. and 180 ° C., preferably between 130 ° C. and 170 ° C., and at a pressure of between 1 bar and 10 bar. Preferably, the regeneration in the distillation column is carried out at a temperature of between 155 ° C. and 165 ° C. and at a pressure of between 6 bar and 8.5 bar in the case where it is desired to reinject the acid gases. . Preferably, the regeneration in the distillation column is carried out at a temperature of 115 ° C. and 130 ° C. and at a pressure of between 1.7 bar and 3 bar in the case where the acid gas is sent to the atmosphere. or in a downstream treatment process, such as a Claus process or a tail gas treatment process. Moreover, a demixing phenomenon for a given absorbent solution (separation of liquid-liquid phases within the absorbing solution) can be induced by a rise in temperature. Said demixing phenomenon can be controlled by the choice of the operating conditions of the process and / or the composition of the absorbent solution. In this case, variants (FIG 2) of the process according to the invention can be implemented, in particular a fractional regeneration by heating the absorbent solution. Process for removing acidic compounds in a gaseous effluent with fractional regeneration by heating (FIG 2) The implementation of an absorbent solution for deacidifying a gaseous effluent is carried out schematically by carrying out an absorption step, followed by a step of heating the absorbent solution, followed by a liquid-liquid separation step of the absorbent solution, followed by a regeneration step. The absorption step comprises contacting the gaseous effluent containing the acidic compounds to be removed with the absorbing solution in a C1 absorption column. The gaseous effluent to be treated (1) and the absorbent solution (4) feed the column C1. During contact, the organic compounds provided with an amine function of the absorbent solution (4) react with the acidic compounds contained in the effluent (1) so as to obtain a gaseous effluent depleted in acidic compounds (2) which comes out in column head C1 and an absorbent solution enriched in acidic compounds (3) which leaves at the bottom of column C1. The heating step consists in raising the temperature of the absorbent solution (3), for example in a heat exchanger E1, to obtain a two-phase solution (5). The two-phase solution (5) is sent to a decanter BS1, in which the liquid-liquid separation step consists of separating the two phases obtained in the heating step by sending the phase rich in acid gas ( 12) to the regeneration column C2, and returning the lean phase acid gas (14), after possible passage in an exchanger E3, to the absorption column C1. The gas phase released by heating the absorbent solution (3) in the exchanger E1 is separated from the liquid phases in BS1 and discharged through the pipe (13).

The regeneration step therefore consists in particular in heating in the distillation column C2 and, optionally, in expanding, the acid-enriched absorbent solution (12) in order to release the acidic compounds which come out at the top of column C2 in gaseous form (7). ). The regenerated absorbent solution, that is to say depleted in acidic compounds (6), leaves at the bottom of the column C2, then passes into the exchanger E1, in which it gives heat to the flow (3) as previously described. . The regenerated and cooled absorbent solution (4), after optional passage in a new exchanger E2, is then recycled to the absorption column C1. At the bottom of the distillation column C2, a portion of the absorbent solution is withdrawn through the conduit (10), heated in the reboiler R1, and then reintroduced into the bottom of the column C2 via the conduit (11).

The absorption step of the acidic compounds can be carried out at a pressure of between 1 bar and 120 bar, preferably between 20 bar and 100 bar for the treatment of a natural gas, preferably between 1 bar and 3 bar for treatment of industrial fumes, and at a temperature between 20 ° C and 100 ° C, preferably between 30 ° C and 95 ° C, more preferably between 30 ° C and 90 ° C, more preferably between 30 ° C C and 80 ° C, even more preferably between 30 ° C and 70 ° C, or even between 30 ° C and 60 ° C. Indeed, the process according to the invention has an excellent capacity of absorption of acidic compounds when the temperature in the absorption column Cl is between 30 ° C and 60 ° C. Generally, the temperature varies in the absorber as a function of the temperature of the introduced fluids and the exothermicity of the reactions. The temperature of the absorbent solution supplying the absorber is such that the solution is monophasic on arrival at the absorber head. It is preferably strictly less than 60 ° C, and still more preferably less than 55 ° C.

The regeneration step of the process according to the invention can be carried out by thermal regeneration, optionally supplemented by one or more expansion steps. It is possible to carry out, before the regeneration step, a first step of relaxing the absorbent solution loaded with acidic compounds. It is also possible to perform a second expansion step of the absorbent solution loaded with acid compounds, the second expansion step being carried out after the first expansion step and before the regeneration step, the absorbent solution being heated before undergoing the second step of relaxation. Given the high stability of the TMHDA, it is possible to regenerate the absorbent solution according to the invention at high temperature in a distillation column. In general, the thermal regeneration step is carried out at a temperature of between 100 ° C. and 180 ° C. and at a pressure of between 1 bar and 10 bar. Preferably, the regeneration in the distillation column is carried out at a temperature of between 155 ° C. and 165 ° C. and at a pressure of between 6 bar and 8.5 bar in the case where it is desired to reinject the acid gases. . Preferably, the regeneration in the distillation column is carried out at a temperature of 115 ° C. and 130 ° C. and at a pressure of between 1.7 bar and 3 bar in the case where the acid gas is sent to the atmosphere. or in a downstream treatment process, such as a Claus process or a tail gas treatment process.

Examples Absorbent solutions used in these examples are aqueous solutions of TMHDA in combination with a compound of the general formula (II) or a mixture of a compound of the general formula (II) with a compound of the general formula (III). The compounds of general formula (II) used as examples are: 2-n-butylpiperazine (2-BuPz), 2-phenylpiperazine (2-PhPz), 2-n-hexylpiperazine (2 -HPz), 2-n-octylpiperazine (2-OPz), 2-n-decylpiperazine (2-DPz). The mixtures of a compound of general formula (II) with a compound of general formula (III) used by way of example are mixtures of 2-methyl-5-n-butylpiperazine and 2-methyl-6-n- butylpiperazine on the one hand (2-Me-5/6-BuPz) and 2-methyl-5-n-octylpiperazine and 2-methyl-6-n-octylpiperazine on the other hand (2-Me-5 / 6- OPz) on the other hand. Table 1 below details the compositions of these examples. Formulation A TMHDA (30% wt) + 2-BuPz (10% wt) + H2O Formulation B TMHDA (30% wt) + 2-PhPz (10% wt) + H2O Formulation C TMHDA (30% wt) + 2-HPz (10% wt) + H2O Formulation D TMHDA (30% wt) + 2-OPz (10% wt) + H2O Formulation E TMHDA (30% wt) + 2-DPz (10% wt) + H2O Formulation F TMHDA (30% wt) % wt) + 2-Me-5/6-BuPz (10% wt) + H2O Formulation G TMHDA (30% wt) + 2-Me-5/6-OPz (10% wt) + H2O Table 1 Also used Absorbent solution in these examples of aqueous solutions of TMHDA in combination with a compound of general formula (II) and with piperazine (Pz). These formulations are detailed in Table 2 below: Formulation H TMHDA (30% wt) + 2-HPz (5% wt) + Pz (5% wt) + H2O Formulation I TMHDA (30% wt) + 2-OPz (5% wt) + Pz (5% wt) + H2O Formulation J TMHDA (30% wt) + 2-OPz (7% wt) + Pz (3% wt) + H2O Formulation K TMHDA (30% wt) + 2 -DPz (7% wt) + Pz (3% wt) + H2O Table 2 In the first example described below, the synthesis protocol of the compounds of general formula (II) used in the composition of formulations A to E is presented. and H to K, as well as the 2-Me-5/6-BuPz and 2-Me-5/6-OPz activator mixtures of the F and G formulations. In the second example described below, it is shown that the The physicochemical properties of the formulations A to G (ie demixing temperature) at different CO.sub.2 loading rates are very different from those of aqueous solutions of TMHDA in combination with a primary or secondary amine which does not correspond to the general formula (II). ) or (III). The aqueous solution chosen for illustration is a solution of TMHDA in combination with piperazine, the composition of which is detailed in Table 3 below. Reference 1 TMHDA (30% wt) + Pz (10% wt) + H2O Table 3 Finally, in the third example described below, the performances of formulations A, D, E and I (ie capture capacity) are compared. to that of an aqueous solution of MonoEthanolAmine (MEA) at 30% by weight, which constitutes the reference solvent for post-combustion fume extraction application, as well as that of an aqueous solution consisting of 30% by weight of TMHDA in combination with 10% by weight of N-MetBzA, as described in FR 2934172. This amine N-methyl-benzylamine (N-MetBzA) does not meet the general formula (II) or (III). The CO2 capture capacity of the formulations according to the invention is also compared with that of an aqueous solution of methyl dIethanolamine (MDEA) at 39% by weight in combination with piperazine at 6.7% by weight, which constitutes a reference solvent. for a natural gas processing application. Finally, in the fourth example, the stability of the formulations J and K is compared with that of an aqueous solution of TMHDA at 35% by weight and that of an aqueous solution of MEA at 30% by weight.

In the formulations given in the various tables, the sum of the mass fractions expressed in% by weight of the various compounds and water is equal to 100% by weight of the absorbent solution.

The various absorbent solutions containing amines and water are hereinafter referred to indifferently as formulations or solvents. Example 1 Synthesis Protocols Synthesis of 2-Butylpiperazine To a solution of 420 g (7.0 moles) of ethylenediamine in 330 ml of ethanol is added at 60 ° C in 20 minutes 100 g (1.0 mole) 1,2-epoxyhexane in 50 ml of methanol. The medium is maintained at this temperature for 2 hours, then the methanol and the excess of ethylenediamine are removed by distillation. 50 g of the product obtained are transferred to a Grignard reactor containing 50 ml of 1,4-dioxane and 3 g of Raney nickel. The medium is brought to the temperature of 180 ° C. for 4 hours under a hydrogen pressure maintained at 10 bar. After degassing and return to ambient temperature, the medium is filtered to remove the catalyst and the solvent is evaporated, and after distillation under reduced pressure, 52.0 g of a product whose 13C-NMR spectrum (CDCl3), given below, is consistent with that of 2-butylpiperazine. 46.8 ppm: -HNICH2-CH2] -N1-1- [CH2-CH (CH2-CH2-CH2-CH3)] - 47.4 ppm: -HNICH2-CH2] -N1-1- [CH2-CH ( CH2-CH2-CH2-CH3)] - 52.7 ppm: -HNICH2-CH2] -N1-1- [CH2-CH (CH2-CH2-CH2-CH3)] - 56.3 ppm: -HNICH2-CH2] -N-1- [CH2-CH (CH2-CH2-CH2-CH3)] - 34.2 ppm: -HNICH2-CH2] -N1-1- [CH2-CH (CH2-CH2-CH2-CH3)] - 27.8 ppm: -HNICH2-CH2] -N1-1- [CH2-CH (CH2-CH2-CH2-CH3)] -22.7 ppm: -HNICH2-CH2] -N1-1- [CH2-CH ( CH2-CH2-CH2-CH3)] - 13.8 ppm: -HNICH2-CH2] -N1-1- [CH2-CH (CH2-CH2-CH2-CH3)] - Synthesis of 2-phenylpiperazine to a solution of 410 g (6.8 moles) of ethylenediamine in 350 ml of ethanol is added at 60 ° C in 20 minutes 100 g (0.83 mole) of epoxystyrene in 50 ml of ethanol. The medium is maintained at this temperature for 2 hours, then the ethanol and the excess of ethylenediamine are removed by distillation. The product obtained is transferred to a Grignard reactor containing 150 ml of n-heptane and 3 g of Raney nickel. The medium is brought to the temperature of 180 ° C. for 4 hours under a hydrogen pressure maintained at 10 bar. After degassing and return to ambient temperature, the medium is filtered to remove the catalyst and the solvent is evaporated and after distillation under reduced pressure 81.1 g of a product whose 13C-NMR spectrum (CDCl3), given below, is obtained. below, is consistent with that of 2-phenylpiperazine. 47.4 ppm: -HNICH2-CH2] -N1-1- [CH2-CH (C6H5)] - 45.6 ppm: -HNICH2-CH2] -N- 1- [CH2-CH (C6H5)] - 54.0 ppm: -HNICH2-CH2] -N1-1- [CH2-CH (C6H5)] - 61.6 ppm: -HNICH2-CH2] -N1-1 [CH2-CH (C6H5)] - 126.5 ppm, 128.0 ppm, 127.0 ppm and 142.5 ppm: -HNICH2-CH2] -N1-1- [CH2-CH (C6H5)] - Synthesis of 2-hexylpiperazine To a solution of 328 g (5.5 moles) of ethylenediamine in 300 ml of methanol is added at 60 ° C in 20 minutes 100 g (0.78 mole) of 1,2-epoxyoctane in 50 ml. of methanol. The medium is maintained at this temperature for 2 hours, then the methanol and the excess of ethylenediamine are removed by distillation. 50 g of the product obtained are transferred to a Grignard reactor containing 50 ml of n-heptane and 3 g of Raney nickel. The medium is brought to the temperature of 180 ° C. for 4 hours under a hydrogen pressure maintained at 10 bar. After degassing and return to ambient temperature, the medium is filtered to remove the catalyst and the solvent is evaporated and after distillation under reduced pressure is obtained 41.4 g of a product whose 13C-NMR spectrum (CDCI3), given below. below, is consistent with that of 2-hexylpiperazine. 46.4 ppm: -HNICH2-CH2] -N1-1- [CH2-CH (CH2-CH2-CH2-CH2-CH2-CH3)] - 47.0 ppm: -HNICH2-CH2] -N1-1- [ CH2-CH (CH2-CH2-CH2-CH2-CH2-CH3) - 52.3 ppm: -HNICH2-CH2] -N1-1- [CH2-CH (CH2-CH2-CH2-CH2-CH2-CH3) ] - 55.9 ppm: -HNICH2-CH2] -N1-1- [CH2-CH (CH2-CH2-CH2-CH2-CH2-CH3)] - 34.3 ppm: -HNICH2-CH2] -N1-1 - [CH2-CH (CH2-CH2-CH2-CH2-CH2-CH3)] - 31.3 ppm: -HNICH2-CH2] -N1-1- [CH2-CH (CH2-CH2-CH2-CH2-CH2) CH3)] - 29.0 ppm: -HNICH2-CH2] -N1-1- [CH2-CH (CH2-CH2-CH2-CH2-CH2-CH3)] - 25.2 ppm: -HNICH2-CH2] -N1 -1- [CH2-CH (CH2-CH2-CH2-CH2-CH2-CH3)] 22.2 ppm: -HNICH2-CH2] -N1-1- [CH2-CH (CH2-CH2-CH2-CH2) CH2-CH3)] - 13.7 ppm: -HNICH2-CH2] -N1-1- [CH2-CH (CH2-CH2-CH2-CH2-CH2-CH3)] - Synthesis of 2-octylpiperazine A solution of 672 g (11.2 moles) of ethylenediamine in 710 ml of methanol is added at 60 ° C in 20 minutes 250 g (1.6 moles) of 1,2-epoxydecane in 150 ml of methanol. The medium is maintained at this temperature for 2 hours, then the methanol and the excess of ethylenediamine are removed by distillation. 173.0 g of the product obtained are transferred to a Grignard reactor containing 150 ml of n-heptane and 5 g of Raney nickel. The medium is brought to the temperature of 160 ° C. for 4 hours under a hydrogen pressure maintained at 10 bar. After degassing and return to ambient temperature, the medium is filtered to remove the catalyst and the solvent is evaporated and after distillation under reduced pressure is obtained 149.0 g of a product whose 13C-NMR spectrum (CDCl3), given below. below, is consistent with that of 2-octylpiperazine. 46.5 ppm: -HNICH2-CH2] -N1-1- [CH2-CH (CH2-CH2-CH2-CH2-CH2-CH2-CH2-CH3) ] - 47.1 ppm: -HNICH2-CH2] -N1-1- [CH2-CH (CH2-CH2-CH2-CH2-CH2-CH2-CH2-CH3)] - 52.6 ppm: -HNICH2-CH2] -N1-1- [CH2-CH (CH2-CH2-CH2-CH2-CH2-CH2-CH2-CH3)] -56.2 ppm: -HNICH2-CH2] -N1-1- [CH2-CH (CH2) CH2-CH2-CH2-CH2-CH2-CH2-CH3)] - 34.4 ppm: -HNICH2-CH2] -N1-1- [CH2-CH (CH2-CH2-CH2-CH2-CH2-CH2-CH2- CH3)] - 31.5 ppm: -HNICH2-CH2] -N1-1- [CH2-CH (CH2-CH2-CH2-CH2-CH2-CH2-CH2-CH3)] - 29.5 ppm: -HNICH2- CH2] -N1-1- [CH2-CH (CH2-CH2-CH2-CH2-CH2-CH2-CH2-CH3)] - 29.2 ppm: -HNICH2-CH2] -N1-1- [CH2-CH ( CH2-CH2-CH2-CH2-CH2-CH2-CH2-CH3)] 29.0 ppm: -HNICH2-CH2] -N1-1- [CH2-CH (CH2-CH2-CH2-CH2-CH2-CH2) CH2-CH3)] - 25.4 ppm: -HNICH2-CH2] -N1-1- [CH2-C H (CH2-CH2-CH2-CH2-CH2-CH2-CH2-CH3)] 22.3 ppm: -HNICH2-CH2] -N1-1- [CH2-CH (CH2-CH2-CH2-CH2-CH2- CH2-CH2-CH3)] - 13.8 ppm: -HNICH2-CH2] -N1-1- [CH2-CH (CH2-CH2-CH2-CH2-CH2-CH2-CH2-CH3)] - Synthesis of the 2 To a solution of 228 g (3.8 moles) of ethylenediamine in 240 ml of methanol is added at 60 ° C in 20 minutes 100 g (0.54 mole) of 1,2-epoxydodecane in 60 ml of methanol. . The medium is maintained at this temperature for 2 hours, then the methanol and the excess of ethylenediamine are removed by distillation. 138.0 g of the product obtained are transferred to a Grignard reactor containing 200 ml of n-heptane and 3 g of Raney nickel. The medium is brought to the temperature of 160 ° C. for 4 hours under a hydrogen pressure maintained at 10 bar. After degassing and return to ambient temperature, the medium is filtered to remove the catalyst and the solvent is evaporated and after distillation under reduced pressure is obtained 97.0 g of a product whose 13C-NMR spectrum (CDCl3), given below. below, is consistent with that of 2-decylpiperazine. 46.5 ppm: -HNICH2-CH2] -N1-1- [CH2-CH (CH2-CH2-CH2-CH2-CH2-CH2-CH2-CH2-CH2-CH3)] - 47.0 ppm: -HNICH2- CH2] -N1-1- [CH2-CH (CH2-CH2-CH2-CH2-CH2-CH2-CH2-CH2-CH2-CH3)] - 52.4 ppm: -HNICH2-CH2] -N1-1- [ CH2-CH (CH2-CH2-CH2-CH2-CH2-CH2-CH2-CH2-CH2-CH3)] - 56.1 ppm: -HNICH2-CH2] -N1-1- [CH2-CH (CH2-CH2) CH2-CH2-CH2-CH2-CH2-CH2-CH2-CH3)] - 34.3 ppm: -HNICH2-CH2] -N1-1- [CH2-CH (CH2-CH2-CH2-CH2-CH2-CH2) CH2-CH2-CH2-CH3)] 31.6 ppm: -HNICH2-CH2] -N1-1- [CH2-CH (CH2-CH2-CH2-CH2-CH2-CH2-CH2-CH2-CH2-CH3) ] - 29.5 ppm: -HNICH2-CH2] -N1-1- [CH2-CH (CH2-CH2-CH2-CH2-CH2-CH2-CH2-CH2-CH2-CH3)] - 29.3 ppm: HNICH2-CH2] -N1-1- [CH2-CH (CH2-CH2-CH2-CH2-CH2-CH2-CH2-CH2-CH2-CH3)] - 29.3 ppm: -HNICH2-CH2] -N1-1 - [CH2-CH (CH2-CH2-CH2-CH2-CH2-CH2-CH2-CH2-CH2-CH3)] - 29.3 ppm: -HNICH2-CH2] -N1-1- [CH2-CH (CH2) CH2-CH2-CH2-CH2-CH2-CH2-CH2-CH2-CH3)] 29.0 ppm: -HNICH2-CH2] -N1-1- [CH2-CH (CH2-CH2-CH2-CH2-CH2) CH2-CH2-CH2-CH2-CH3)] 25.4 ppm: -HNICH2-CH2] -N1-1- [CH2-CH (CH2-CH2-CH2-CH2-CH2-CH2-CH2-CH2-CH2- CH3)] - 22.4 ppm: -HNICH2-CH2] -N1-1- [CH2-CH (CH2) -CH2-CH2-CH2-CH2-CH2-CH2-CH2-CH2-CH3)] 13.8 ppm: -HNICH2-CH2] -N1-1- [CH2-CH (CH2-CH2-CH2-CH2-CH2) -CH2-CH2-CH2-CH2-CH3)] - Synthesis of 2-methyl-5-butylpiperazine and 2-methyl-6-butylpiperazine to a solution of 518 g (7.0 moles) of propanediamine in 350 ml of ethanol is added at 60 ° C in 60 minutes 100 g (1.0 mole) of 1,2-epoxyhexane in 50 ml of ethanol. The medium is maintained at this temperature for 2 hours, then the ethanol and the excess of 1,2-propanediamine are removed by distillation. 100.0 g of the product obtained are transferred to a Grignard reactor containing 100 ml of heptane and 5 g of Raney nickel. The medium is brought to the temperature of 160 ° C. for 4 hours under a hydrogen pressure maintained at 20 bar. After degassing and return to ambient temperature, the medium is filtered to remove the catalyst and the solvent is evaporated and after distillation under reduced pressure is obtained 55.0 g of a product whose 13C-NMR spectrum (CDCI3) is consistent with that of a mixture of 2-methyl-5-butylpiperazine and 2-methyl-6-butylpiperazine. Synthesis of 2-methyl-5-octylpiperazine and 2-methyl-6-octylpiperazine To a solution of 259 g (3.5 moles) of 1,2-propanediamine in 300 ml of ethanol is added at 60 °. C in 60 minutes 78 g (0.5 mole) of 1,2-epoxydecane in 100 ml of ethanol. The medium is maintained at this temperature for 2 hours, then the ethanol and the excess of 1,2-propanediamine are removed by distillation. 50.0 g of the product obtained are transferred to a Grignard reactor containing 100 ml of 1,4-dioxane and 2.5 g of Raney nickel. The medium is brought to the temperature of 160 ° C. for 4 hours under a hydrogen pressure maintained at 20 bar. After degassing and return to ambient temperature, the medium is filtered to remove the catalyst and the solvent is evaporated and after distillation under reduced pressure is obtained 45.2 g of a product whose 13C-NMR spectrum (CDCI3) is consistent with that of a mixture of 2-methyl-5-octylpiperazine and 2-methyl-6-octylpiperazine.

Example 2: Demixing temperatures. Effect of CO2 charge rate. The demixing phenomenon can be controlled by the nature of the activator that is added to an aqueous solution of TMHDA.

Depending on the composition of the absorbent solution based on TMHDA, the possible presence of a primary or secondary amine, the composition of the gas to be treated (ie the partial pressure of CO2) and the temperature of the absorbent solution, a liquid phase separation -liquid can occur (demixing phenomenon). In the laboratory, the temperature at which demixing occurs for a given formulation (ie concentrations of amines and given water) is determined at a given loading rate (expressed in moles of CO2 per kg of formulation before loading) by increasing gradually the temperature. Each formulation is first charged with CO2 at room temperature by sweeping about 30 g of a virgin formulation sample with a flow rate of 2ONL / h of CO2 until a loading rate of 2 moles of CO2 per kg is reached. virgin solution, the rate of charge being controlled by weighing. About 15 g of the resulting charged solution is mixed with the corresponding amount of virgin solution to obtain a solution having a feed rate of 1 mole of CO2 per mole of virgin solution. For each formulation, three samples corresponding to the virgin solution, the solution charged with CO2 at 1 mol / kg and at 2 mol / kg are immersed in a thermostatically controlled oil bath whose temperature is regulated to within one degree Celsius. . For each solution, the temperature at which a phase separation is observed, in successive temperature increments, from 40 ° C to 55 ° C, in increments of 5 ° C, from 55 ° C to 65 ° C in increments of 1 ° C, and 65 ° C to 95 ° C, in increments of 5 ° C.

According to the results of these laboratory tests, the absorbing solution can be implemented in a deacidification process as described in FIG. 1, or in a deacidification process with split regeneration by heating, as described in FIG. An absorbent solution based on TMHDA activated with a compound of general formula (II) or (III) is particularly suitable for this type of process, since it allows the absorbent solution to be monophasic under the operating conditions corresponding to that of the absorber (for example at 40 ° C), and two-phase beyond the charge / effluent exchanger (ie generally at 90 ° C), allowing fast liquid-liquid phase separation. The examples below make it possible to demonstrate the importance of the structure of the activator, of the respective concentration of the activator according to the invention and of another activator according to the prior art. 2-N Structure of the activator The tests in the laboratory are carried out for formulations having a total concentration of 40 ° A> weight of amines: - 30% by weight of TMHDA and 10% of a secondary diamine corresponding to the general formula (II) or (III) in the case of formulations A to G, and - 30% by weight of TMHDA and 10% by weight of piperazine in the case of reference formulation 1. Table 4 below summarizes the results obtained for different formulations. Temperature at which a phase separation is observed (° C) Virgin solution Charge rate: 1 mole CO2 / kg Charge rate: 2 mole CO2 / kg Reference 1 55 25 25 Formulation A 85 75 63 Formulation B 75 70 55 Formulation C 70 75 60 Formulation D 70 90 85 Formulation E 65 95 Single phase at 95 ° C Formulation F 60 85 90 Formulation G 55 75 75 Table 4 It can be seen from Table 4 above that an amount equal to 10% by weight of an activator of general formula (II) or (III) makes it possible to totally eliminate the demixing phenomenon under the operating conditions of the absorber, this being observed in the case of the formulation reference compound containing an activator not satisfying the general formula (II) or (III) (piperazine). Indeed, the temperature in the absorber generally varies between the temperature of the virgin amine feeding the absorber, preferably strictly less than 60 ° C, and even more preferably strictly less than 55 ° C and a maximum temperature generally not exceeding 95 ° C, and preferably between 30 ° C and 60 ° C. Formulations A to G are therefore of interest since they make it possible to have a monophasic absorbent solution under the operating conditions corresponding to the absorber. Formulations A to D, F and G, charged to 2 mol / kg, under conditions characteristic of the outlet of the charge / effluent exchanger, are two-phase at 95 ° C., and are therefore particularly advantageous for in a deacidification process with fractional regeneration by heating as described in relation with FIG. 2. Formulation E charged at 2 moles / kg, ie under conditions characteristic of the outlet of the charge / effluent exchanger, is monophasic at 95 ° C and it can thus be particularly advantageous to implement it in a deacidification process as described in Figure 2-B / Composition of the solution of activator compounds (mixture of piperazine and an activator of general formula (II)) The tests in the laboratory are carried out for formulations having a total concentration of 40% by weight of amines: 30% by weight of TMHDA and 10% by weight of a mixture of a secondary diamine. ire corresponding to the general formula (II) and piperazine. These formulations H to K are compared to reference 1 containing 30% by weight of TMHDA and 10% by weight of piperazine (Pz), and to the formulations D to F containing 30% by weight of TMHDA and 10% by weight of secondary amine according to formula (II). Composition of the activators (in Temperature at which a% weight of the solution is observed phase separation (° C) absorbent) According to the formula Other Blank solution Rate rate of general (II) charge: 1 charge: 2 mole CO2 / kg moles CO2 / kg Reference 1 o Pz 10% 55 25 25 Formulation D 2-HPz 10% 0 70 90 85 Formulation H 2-HPz 5% Pz 5% 63 62 60 Formulation E 2-0Pz 10% 0 65 95 Single phase at 95 ° C Formulation J 2-OPz 7% Pz 3% 60 64 90 Formulation I 2-OPz 5% Pz 5% 59 57 70 Formulation F 2-DPz 10% 0 60 85 90 Formulation K 2-DPz 7% Pz 3% Table 5 It can be observed from Table 5 above that between 5% and 10% of the activators of general formula (II) in combination with piperazine to reach a total concentration of 10% by weight (formulations H, J, I and K) makes it possible to completely eliminate the demixing phenomenon under the operating conditions of the absorber which is observed in the case of reference formulation 1 containing as sole activator piperazine at a concentration of 10% by weight. Formulations H, I, J and K are therefore interesting because they make it possible to have a monophasic absorbent solution under the operating conditions corresponding to the absorber. Formulations H, I, J and K loaded at 2 mol / kg, that is to say under conditions characteristic of the outlet of the charge / effluent exchanger, are diphasic at a temperature greater than or equal to 90 ° C. , typically encountered after passing through the charge / effluent exchanger in a deacidification process, and are therefore particularly advantageous for use in a deacidification process with fractional regeneration by heating, as described in FIG. for example, it can be seen that the combination of piperazine with an activator corresponding to the general formula (II) (formulations H, I, J and K) lowers the demixing temperature for a given loading rate, while maintaining the monophasic solution in the conditions of the absorber whatever the charge rate.

A liquid-liquid phase separation occurs at 90 ° C in the case of the formulation J containing 3% by weight of piperazine and 7% by weight of 2-OPz charged to 2 mole / kg, while the formulation E containing 10% of 2-OPz is monophasic at 95 ° C for the same charge rate. While formulation E is monophasic at 95 ° C, the proportion of higher liquid phase (lean phase) is 38% by volume for formulation J at the same temperature. The formulation J is therefore particularly advantageous for being used in a deacidification process with fractional regeneration by heating as described in FIG. 2, in which a decantation step after passing through the charge-effluent exchanger operating at 95 ° C. would reduce the solvent flow rate in the regenerator by 38% compared to the formulation E used in a deacidification process as described in FIG.

Example 3: CO2 capture capacity The performance of the CO2 capture capacity of the absorbent solutions according to the invention (formulations C to E) are compared in particular with those of an aqueous solution of MEA at 30% by weight, which constitutes the solvent reference for an application for capturing CO2 contained in post-combustion fumes. They are also in a formulation containing 30% by weight of TMHDA and 10% by weight of N-MetBzA according to document FR 2 934 172.

The performances in terms of the CO2 absorption capacity of the formulations are also compared with that of an aqueous solution of MethylDiethanolamine at 39% by weight containing 6.7% by weight of piperazine, which constitutes a reference solvent for the deacidification of natural gas. .

An absorption test is carried out on aqueous amine solutions in a perfectly stirred closed reactor whose temperature is controlled by a control system. For each solution, the absorption is carried out in a liquid volume of 50 cm3 by pure CO2 injections from a reserve. The solvent solution is previously drawn under vacuum before any 002 injections. The pressure of the gas phase in the reactor is measured and an overall material balance on the gas phase makes it possible to measure the solvent loading rate a = nb of mole gas acid / nb of mole amine. By way of example, the feed rates (a = number of moles of acid gas / number of moles of amine) obtained at 40 ° C. for different partial pressures of CO 2 between absorbent solutions A are compared in Table 6. D, E and H according to the invention, an absorbent solution of MonoEthanolAmine, and the formulation containing 30 '' / 0 weight of TMHDA and 10% by weight of N-MetBzA according to document FR 2 934 172, for a capture application of CO2 in post-combustion. To go from a quantity of the charge rate obtained in the laboratory to a characteristic quantity of the process, some calculations are necessary, and are explained below for the intended application: In the case of a CO2 capture application in post -ombustion, the partial pressures of CO2 in the effluent to be treated are typically 0.1 bar with a temperature of 40 ° C, and it is desired to cut down 90 ') / 0 of the acid gas. The AaPC cyclic capacity expressed in moles of CO 2 per kg of solvent is calculated, considering that the solvent reaches a loading level at the bottom of the absorption column corresponding to an equilibrium partial pressure at 40 ° C equal to 50% of the partial pressure in the effluent to be treated, namely AaPPCO2 = 0.05 bar, and must at least be regenerated at a load ratio corresponding to an equilibrium partial pressure at 40 ° C equal to 50% of the pressure in the column head conditions, ie AaPPCO2 = 0.005 bar, to achieve 90% CO2 reduction. AaPC = PPCO2 = 0.05bar - aPPCO 2 = 0.005bar). [?] -10 / M where [A] is the total concentration of amine expressed as% by weight, M is the molar mass of the amine or, in the case of a mixture of amines, the average molar mass of the mixture of amines in g / mol: M = [A] / ([TMHDA] / MTMHDA + [Act] / MAct + [Pz] / Mpz) where [TMHDA], [Act] and [Pz] are respectively the concentrations of TMHDA, activator according to the invention or the prior art distinct from piperazine, and piperazine, MTMHDA, MAct and MpZ are the corresponding molar masses expressed in g / mol.

AaPPCO2 = 0.05 bar and AaPPCO2 = 0.005 bar are the loading rates (mole CO2 / mole of amine) of the solvent in equilibrium respectively with a partial pressure of 0.05 bar and 0.005 bar of 002. Charge rate a = nCO2 / namine Formulation T (° C) PPCO2 = PPCO2 = AaPC 0.05 bar 0.005 bar (molCO2 / kg Solvent) MEA 30% 40 0.5 0.41 0.47 TMHDA 30% + N-Met-BzA 10% (according to FR 2 934 172) 40 0.74 0.36 0.98 TMHDA 30% + 2-BuPz 10% (formulation A according to the invention) 40 0.84 0.17 1.64 TMHDA 30% + 2- HPz 10% Formulation D (according to the invention) 40 0.8 0.22 1.35 TMHDA 30% + 2-OPz 10% Formulation E (according to the invention) 40 0.8 0.25 1.24 TMHDA 30 % + 2-HPz 5% + Pz 5 ° / 0 Formulation H (according to the invention) 40 0.92 0.43 1.32 Table 6 For a post-combustion fume extraction application where the partial pressure of CO 2 in the effluent to be treated is 0.1 bar, this example illustrates the greater cyclic capacity obtained thanks to an absorbent solution according to the invention, to reach a slaughter rate of 90% e n absorber output. In this application where the energy associated with the regeneration of the solution is critical, it can be observed that the formulations according to the invention make it possible to obtain much better performances than an absorbent solution based on MEA, in terms of cyclic capacity. (by a factor of 2.6 to 3.5). The comparison of the formulations of the invention with the formulation containing 30% by weight of TMHDA and 10% by weight of N-MetBzA according to document FR 2 934 172 also shows an improvement in the cyclic capacity between 26% and 67%. It is concluded that the formulations according to the invention have a marked advantage in terms of regeneration energy with respect to an aqueous solution at 30% by weight of MEA, and with respect to the prior art described in document FR 2934172.

By way of example, the feed ratios expressed in mole / kg (a = number of moles of acid gas / number of moles of amine) obtained at 40 ° C. for various partial pressures are compared in Table 7 below. of CO2 between absorbent solutions A, D and H according to the invention, an absorbent solution of MethylDiethanolamine at 39% by weight containing 6.7% by weight of piperazine, and the formulation containing 30% by weight of TMHDA and 10% by weight of N -MetBzA according to document FR 2 934 172, for a total decarbonation application in natural gas treatment. In the case of a total decarbonation application in natural gas treatment, the partial pressures of CO2 in the effluent to be treated are typically from several hundred millibars to several bars with a temperature of 40 ° C., and it is desired to eliminate almost all of the CO2 for liquefaction of natural gas. To compare the different solvents, the maximum cyclic capacity expressed in moles of CO2 per kg of solvent is calculated. The cyclic capacity AaLNG, expressed in moles of CO 2 per kg of solvent, corresponding to different equilibrium partial pressure at the bottom of the absorption column, is calculated and considering that the solvent is completely regenerated under the column head conditions. AaLNG, PPCO 2 = ppcO 2)> - [A] - 10I M where [A] and M are defined as above aPPCO 2 being the loading ratio (mole CO2 / mole of amine) of the solvent in equilibrium with the partial pressure of CO 2 considered. Cyclic Absorption Capacity of CO2 AOELNG, PPCO2 (molCO2 / kg solvent) Formulation T (° C) PPCO2 = 0.5 bar PPCO2 = 1 bar PPCO2 = 3 bar MDEA 39% + Pz 6.7% 40 2.54 2.96 3.57 TMHDA 30% + N-Met-BzA 10% (according to FR 2 934 172) 40 3.23 3.54 3.8 TMHDA 30% + 2-BuPz 10% (formulation A according to the invention ) 40 3.63 3.83 4.04 TMHDA 30% + 2-HPz 10% Formulation D (according to the invention) 40 3.54 3.76 3.97 TMHDA 30% + 2-HPz 5% + Pz 5 Formulation H (according to the invention) 3.98 4.21 4.51 Table 7 For a total decarbonation application in natural gas treatment, this example illustrates the greater cyclic capacity obtained thanks to the absorbent solutions according to the invention. The invention relates to the reference formulation containing 39% by weight of MDEA and 6.7% by weight of piperazine, irrespective of the equilibrium partial pressure of equilibrium CO2 considered, corresponding to different CO 2 compositions of natural gas to be treated. There is also an unexpected gain in terms of cyclic capacity obtained thanks to the absorbent solutions according to the invention compared to the formulation containing 30% of TMHDA and 10% of N-methyl-benzylamine claimed in the document FR 2 934 172. Example 4: Stability The TMHDA molecule has the particularity of being very resistant to degradation that may occur in a deacidification unit. The activators of general formula (II) and (III) also have the particularity of being very resistant to degradation that may occur in a deacidification unit. By way of example, the formulations J and K according to the invention are compared with an aqueous solution at 30% by weight of monoethanolamine (MEA) and a 35% by weight aqueous solution of TMHDA.

This example shows that the stability of formulations containing activators according to the invention in combination with TMHDA is comparable to the stability of a solution of TMHDA without activator. It also demonstrates that the formulations according to the invention exhibit a markedly improved stability over a 30 wt% MEA solution. The degradation tests of an amine in aqueous solution are carried out according to the following procedure: 100 g of absorbing solution are placed in a glass reactor surmounted by a condenser 10 to avoid the evaporation of water. The reactor is heated to 80 ° C in an electric heating block. The solution is stirred at 1000 rpm by a magnetic bar. The presence of counter blades prevents the formation of a vortex. A gas is brought into contact with the solution by means of a dip tube for 7 days at atmospheric pressure. The gas flow rate entering the dip tube is a mixture of a gas flow rate of 0.033 Nl / h of CO2 and 7 Nl / h of atmospheric air. This gaseous mixture, produced in a mixing chamber, contains CO2, nitrogen and oxygen, the oxygen content in the gas being about 21%. Gas chromatographic analysis of the absorbent solution tested is carried out before the test and at the end of the test. The chromatographic method uses a polar column, a carrier gas, helium and FID (Flame Induced Detection) detection. This analysis makes it possible to determine a proportion of degradation products that appeared during the test. This proportion of the degradation products (% PD) formed is expressed in percentages of areas of the peaks observed on the chromatogram. It can therefore be calculated as follows: ° A) PD = r Total area - Ame r areas r Total area - A min areas Total area / end of test Total area / before test 25 Amines area the area of the principal peak for a 30 wt% MEA solution or a 35 wt% TMHDA solution or the sum of the areas of the three main peaks in the case of J and K formulations containing 30 wt% of TMHDA, 7 % by weight of secondary diamine according to general formula (II) and 3% by weight of piperazine. In the case of the pre-test solution, the difference between the total area and the main peaks results from the impurities of each amine. In the case of the solution after the test, the difference between the total area and the main peaks comes from the impurities and degradation products formed during the test, the latter therefore being evaluated by the formula above. Table 8 below shows the percentages of formed degradation products visible by the chromatographic method.

Formulation% PD MEA 30% + H2O 23.00% TMHDA 35% + H2O 1.00% TMHDA 30% + 2-OPz 7% + Pz 3% + H2O (Formulation J according to the invention) 0.60% TMHDA 30 % + 2-DPz 7% + Pz 3% + H2O (Formulation K according to the invention) 1.30% Table 8 The results in Table 6 confirm that the aqueous solutions according to the invention have a stability comparable to a solution of TMHDA without activators, and about 20 times more stable than a 30% weight MEA solution.

It is clear that the activators according to the invention mixed with piperazine and TMHDA do not modify the stability of the formulation relative to a solution of TMHDA without activator, at 80 ° C in the presence of CO2 and oxygen. The formation of degradation products detected by gas chromatography reaches, for a total concentration of 40% by weight of amines with activators, a level comparable to that observed for a solution containing 35% by weight of TMHDA without activators. to say close to 1%, is considered of the order of uncertainty of the measure which is 0.3%. Since the TMHDA molecule is interesting for its resistance to degradation, in particular thermal and in the presence of oxygen, it may be advantageous to use it in combination with a diamine of general formula (II) or (III), to regenerate the solvent. at higher temperature and thus obtain an acid gas at higher pressure if this is of interest in the case of reinjection of acid gas. This is particularly interesting in the case of post-combustion CO2 capture where the gas to be treated contains oxygen and where the acid gas must be compressed before reinjection and sequestration. The use of an aqueous absorbent solution according to the invention makes it possible to save on the operating costs of the deacidification unit, and on the investment cost and the operating costs associated with the compression of the acid gas.

Claims (15)

REVENDICATIONS1. Absorbent solution for absorbing acidic compounds of a gaseous effluent comprising: - water - N, N, N ', N'-tetramethyl-1,6-hexanediamine of formula (I), \ N / \ / (I) - at least one activator compound chosen from secondary diamines corresponding to one of the general formulas (II) or (III), the general formula (II) being: R -i NH R2 N / H in which: the group R 1 is chosen from one of the elements of the group consisting of: a hydrogen atom and an alkyl group of 1 to 12 carbon atoms, the group R2 is chosen from one of the elements the group consisting of: an alkyl group of 4 to 16 carbon atoms and a phenyl group, the general formula (III) being: H / N \ / R4 D \ N / / F-i3 H in which: - the grouping R3 is chosen from one of the group consisting of: a hydrogen atom and an alkyl group of 1 to 12 carbon atoms, the group R4 is chosen from one of the elements of the group consisting of: an alkyl group of 4 to 16 carbon atoms and a phenyl group. An absorbent solution according to claim 1 comprising: from 10% to 90% by weight, preferably from 20% to 60% by weight, of N, N, 1, 1-tetramethyl-1,6- hexaned iam ine, - a non-zero and less than 50% by weight, preferably less than 30% by weight, of said at least one activator compound according to general formula (II) or (III), and - from 10% to 90% weight, preferably from 50% to 70% by weight, of water. 3. Absorbent solution according to one of the preceding claims, comprising at least one mixture of at least one activator according to general formula (II) and at least one activator according to general formula (III). 4. Absorbent solution according to one of the preceding claims, wherein the activator compound has the general formula (III) and wherein the R3 group is - an alkyl group of 1 to 12 carbon atoms, or - a hydrogen atom to the proviso that the R 4 group is an alkyl group of 8 to 16 carbon atoms or a phenyl group. 5. Absorbent solution according to one of the preceding claims, wherein the activator compound has the general formula (II), and wherein the group R1 is: - an alkyl group of 1 to 12 carbon atoms, or - an atom hydrogen with the proviso that the group R2 is an alkyl group of 8 to 16 carbon atoms or a phenyl group. 6. Absorbent solution according to one of claims 1 to 3, comprising at least one activator compound of general formula (II) selected from the group consisting of: - 2-Butylpiperazine HN / H - 2-Hexylpiperazine H / N / \ / \ / \ N / H 7. Absorbent solution according to one of claims 1 to 5, comprising at least one activator compound of general formula (II) selected from the group consisting of: - 2-PhenylpiperazineH N 38 NH - 2-Octylpiperazine HNN / H - 2-Decylpiperazine H 1 \ 1 / \, N / \ / / H 8. Absorbent solution according to one of claims 1 to 5, comprising a mixture of a first activator according to the general formula (II) and a second activator of the general formula (III), said mixture being selected in the mixture group consisting of: 2-methyl-5-n-butylpiperazine and 2-methyl-6-n-butylpiperazine of the respective formulas: ## STR1 ## -..........'..,.....--, ---..........NOT....'.'.',--- HH / N / H, and 2-methyl-5-n-octylpiperazine (of general formula III) and 2-methyl-6- n-octyl-piperazine (of general formula II) of respective formulas: HN / NH 9. Absorbent solution according to one of the preceding claims, further comprising at least one additional activator compound comprising a primary amine or N Hsecondary function, preferably in an amount less than 15 ') / 0 weight of the absorbent solution, selected in the group consisting of: monoethanolamine; diethanolamine; N-butylethanolamine; aminoethylethanolamine; diglycolamine; piperazine; 1-methyl-piperazine; 2-methylpiperazine; homopiperazine; N- (2-hydroxyethyl) piperazine; N- (2-aminoethyl) piperazine; morpholine; 3- (methylamino) propylamine; 1,6-hexanediamine; N, N'-dimethyl-1,6-hexanediamine; N-methyl-1,6-hexanediamine; N, N ', N'-trimethyl-1,6-hexanediamine. 10.Procédé de elimination of acidic compounds contained in a gaseous effluent, wherein is carried out: - a step of absorption of the acidic compounds by contacting the effluent with an absorbent solution according to one of claims 1 to 9 so as to obtain a gaseous effluent depleted of acidic compounds and an absorbent solution loaded with acid compounds, - then a regeneration step in which at least a portion of the solution charged with acidic compounds is sent to a distillation column to release the compounds acids in the form of a gaseous effluent and obtain a regenerated absorbent solution. 11.Procédé according to claim 10, wherein the absorbent solution loaded with acid compounds obtained during the absorption step is monophasic. 12.Procédé according to one of claims 10 and 11, wherein the step of absorbing the acidic compounds is carried out at a pressure between 1 bar and 120 bar, and at a temperature between 20 ° C and 100 ° C preferably between 30 ° C and 95 ° C, and wherein the regeneration step is carried out at a pressure of between 1 bar and 10 bar and at a temperature of between 100 ° C and 180 ° C. 13.Procédé according to one of claims 10 to 12, wherein the absorption step is followed by at least a liquid-liquid separation step of the absorbent solution loaded biphasic acid compound obtained after heating the absorbent solution, then at least one step of fractional regeneration of the absorbent solution loaded with acidic compounds. 14. Process for treating natural gas according to one of claims 10 to 13. 15. Process for the treatment of industrial gases according to one of claims 5 to 13, preferably for the capture of 002.