FR2953148A1 - Absorbent solution, useful for absorbing acidic compounds contained in a gaseous effluent, comprises at least one amine, water, and at least one degradation-inhibitor compound having phenyl structure to reduce the degradation of the amine - Google Patents

Abstract

Absorbent solution (A) comprises: (a) at least one amine; (b) water; and (c) at least one degradation-inhibitor compound to reduce the degradation of the amine, where the degradation-inhibitor compound has phenyl structure (I). Absorbent solution (A) comprises: (a) at least one amine; (b) water; and (c) at least one degradation-inhibitor compound to reduce the degradation of the amine, where the degradation-inhibitor compound has phenyl structure of formula (I). R1-R6 : A, B1, C1, D, E, F1 or G; A : -NO 2group; B1 : H; C1 : -W1-X group; W1 : O or S; D : -C(=O)-O-V1; X, V1, Y1 : H, 1-12C hydrocarbyl, alkali or alkaline earth element, monovalent or multivalent metal, ammonium cation (NH 4 +>) or resulting from protonation of an amine function or phosphonium cation; E : -S(=O) 2-O-Y1; F1 : 1-12C hydrocarbyl group; G : phenyl group of formula (II); Z : covalent bond, O, S, N-R12 unit or linear or branched 1-20C hydrocarbyl group; and R12 : H or 1-12C hydrocarbyl group. Provided that: one to three radicals of R1-R6 corresponds to the definition of A; at least three radicals of R1-R6 are B1-G; up to three radicals of R1-R6 corresponds to the definition of C1; up to three radicals of R1-R6 corresponds to the definition of D; up to three radicals of R1-R6 are E; up to three radicals of R1-R6 corresponds to the definition of G; one to three radicals of R7-R11 corresponds to the definition of A; at least three radicals of R7-R11 are B1-F1; up to three radicals of R7-R11 corresponds to the definition of C1; up to three radicals of R7-R11 corresponds to the definition of D; and up to three radicals of R7-R11 corresponds to the definition of E. [Image] [Image].

Description

The present invention relates to the field of the deacidification of a gaseous effluent. More specifically, the present invention provides compounds for reducing the degradation of an absorbent solution used to absorb the acidic compounds contained in a gaseous effluent, the absorbent solution comprising amines in aqueous solution.

The deacidification of gaseous effluents, such as, for example, natural gas and combustion fumes, is 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 (H2S, mercaptans, CO2, COS, SO2, CS2). The deacidification of these effluents, in particular decarbonation and desulfurization, imposes specific constraints on the absorbent solution, in particular a thermal and chemical stability, especially with regard to the impurities of the effluent, namely essentially oxygen, SOx and NOx. .

Absorbent solutions most used today are aqueous solutions of alkanolamines. We can cite the document FR 2 820 430 which proposes processes for deacidification of gaseous effluents. However, it is well known to those skilled in the art that these amines have the disadvantage of being degraded under the conditions of implementation.

In particular, the amines can be degraded by oxygen forming acids such as, for example, formic acid, acetic acid or else oxalic acid in the amine solutions. These acids react with the amines following an acid base reaction to form salts, called "Heat Stable Salt" (HSS) or "Heat Stable Amine Salt" (HSAS). These acids are stronger acids than carbonic acid (formed by the reaction of CO2 with water). The salts they form by reaction with the amines are therefore not regenerated in the regeneration column under the normal operating conditions of the units, and accumulate in the unit.

In the case of CO2 capture in fumes from industrial units or from electricity or energy production in general, the degradation phenomena of the absorbent solution with amines are increased by the presence of a massive amount of oxygen in the load to be treated up to 5% by volume in general. In the case of fumes from the combined cycle with natural gas, the volume content of oxygen in the fumes can reach 15%. The degraded solution is characterized by: a decrease in the absorption of the acidic compounds of the filler relative to a fresh solution of amine, an increase in the density of the absorbent solution, as well as its viscosity, which can lead to a loss of performance, the formation of more volatile amines polluting the treated gas and the acid gas from the regeneration step: ammonia, methylamine, dimethylamine and trimethylamine, for example according to the nature of the amine used, an accumulation of degradation products in the absorbent solution 15 which may result in the need for treatment of the degraded solution, possible foaming problems due to degradation products. The degradation of the absorbing solution therefore penalizes the performance and the proper functioning of the gas deacidification units.

To overcome the problem of degradation, failing to limit or eliminate the presence of oxygen in the absorbent solution, compounds are added to the absorbent solution whose role is to prevent or limit the degradation phenomena of the amine compounds. , in particular the degradation caused by the oxidation phenomena. These compounds are commonly referred to as degradation inhibiting additives. The main known modes of action of the degradation-inhibiting additives are, depending on their nature, a reduction-type reaction and / or a capture, trapping and / or stabilization of the radicals formed in the absorbent solution in order to limit or prevent or to interrupt reactions, including chain reactions, degradation.

The patents US 5686016 and US 7056482 cite additives used to limit the degradation of absorbent solutions used respectively for the deacidification of natural gas and for the capture of CO2.

In general, the present invention proposes a family of degradation inhibiting additives which makes it possible in particular to reduce the degradation of an absorbent solution used for the absorption of acidic compounds contained in a gaseous effluent, the absorbent solution comprising compounds amines in aqueous solution.

The present invention relates to an absorbent solution for absorbing the acidic compounds of a gaseous effluent, said solution comprising: a) at least one amine, b) water, c) at least one degradation inhibiting compound to limit the degradation of said amine, the degradation inhibiting compound having the general formula: R 1 wherein each of R 1 to R 6 is selected from one of Groups A, B, C, D, E, F and G, wherein • Group A contains group ùNO2, • group B contains a hydrogen atom, • group C contains a group ùW-X in which • W is an oxygen atom or a sulfur atom, • X is selected from one of the following elements: a hydrogen atom, a hydrocarbon radical containing from 1 to 12 carbon atoms, an alkaline or alkaline earth element, a monovalent or multivalent metal, an ammonium NH4 + cation or resulting from the protonation an amine function, o a phosphonium cation, O ùc Group D contains a group V in which V is chosen from one of the following elements: a hydrogen atom, a hydrocarbon radical containing from 1 to 12 carbon atoms, an alkaline or alkaline element; earth, monovalent or multivalent metal, or a NH 4 + ammonium cation or resulting from the protonation of an amine function, a phosphonium cation, or the group E contains a group O wherein Y is selected from one of Of the following: a hydrogen atom, a hydrocarbon radical having 1 to 12 carbon atoms, an alkaline or alkaline earth element, a monovalent or multivalent metal, an ammonium NH 4 + cation or resulting from protonation of an amine function, o a phosphonium cation, • group F contains a hydrocarbon radical containing from 1 to 12 carbon atoms, • Group G contains a radical corresponding to the following general formula: R 1 R 9 R 10 in which Z is o a covalent bond, o an oxygen atom or a sulfur atom, o an N-R 12 unit in which R 12 is a hydrogen atom or a hydrocarbon radical comprising 1 to 12 carbon atoms, o a linear or branched hydrocarbon unit comprising from 1 to 20 carbon atoms,

and wherein, the radicals R 1 to R 6 are selected having regard to the following rules: 1. between one and three radicals R 1 to R 6 correspond to the definition of group A, 2. at least three radicals R 1 to R 6 are independently selected from groups B to G, 3. at most three radicals R1 to R6 correspond to the definition of group C, 4. at most three radicals R1 to R6 correspond to the definition of group D, 5. at most three radicals R1 to R6 correspond to to the definition of the group E, at most three radicals R1 to R6 correspond to the definition of the group G, and in which, the radicals R7 to R11 are chosen taking into account the following rules: 7. between one and three radicals R7 to R1i correspond to the definition of group A, 8. at least three radicals R7 to R1 i are independently selected from groups B to F, 9. at most three radicals R7 to R11 are as defined in group C, 10. a maximum of three R7 radicals to R1 i correspond to the definition of group D, 11. at most three radicals R7 to Ri i correspond to the definition of group E.

According to the invention, at least one of the radicals R1, R2, R3, R4, R5, R6, R7, R8, R9, R10, R11, R12, X, V, Y and Z may be a hydrocarbon group containing between 1 and 12 carbon atoms and contains, in addition, at least one of the following: a heteroatom, a halogen, a hydroxyl function, a ketone function, a carboxylic function or a nitrile function.

In the case where two radicals among R 1, R 2, R 3, R 4, R 5 and R 6 belong to the group F, these two radicals may be linked together by a covalent bond so as to form a ring consisting of 5 to 8 atoms. In the case where one of R1, R2, R3, R4, R5 and R6 belongs to group G, two radicals from R7, R8, Ro, Rio and R1i may belong to group F and these two radicals may be connected to each other by a covalent bond to form a ring of 5 to 8 atoms. The solution may comprise between 10% and 80% by weight of amine, between 10% and 90% of water and between 5 ppm and 5% by weight of degradation inhibiting compound. The degradation inhibiting compound may be selected from the group containing: ortonitrobenzoic acid, a salt of ortonitrobenzoic acid, metanitrobenzoic acid, a salt of metanitrobenzoic acid, paranitrobenzoic acid, a salt of the acid paranitrobenzoic acid, 2,4-dinitrobenzoic acid, a salt of 2,4-dinitrobenzoic acid, ortonitrophenol, a salt of ortonitrophenol, metanitrophenol, a salt of metanitrophenol, paranitrophenol, a salt of paranitrophenol, 2,4,6-trinitrophenol and 2,4,6-trinitrophenol salt.

The amine may be selected from the group containing: N, N, N ', N', N "-pentamethyldiethylenetriamine, piperazine, monoethanolamine, diethanolamine, methyldiethanolamine, diisopropanolamine, diglycolamine, a glycine salt and a salt of taurine.

In the case where the amine is monoethanolamine, the degradation inhibiting compound may be chosen from paranitrobenzoic acid or the sodium salt of paranitrobenzoic acid.

The invention also relates to a process for absorbing acidic compounds contained in a gaseous effluent, wherein the gaseous effluent is brought into contact with an absorbent solution according to the invention as described above. In the process according to the invention, the aqueous solution can be used to absorb acidic compounds contained in one of the effluents of the group containing the natural gas, the combustion fumes, the synthesis gases, the refinery gases, tail gas from the Claus process, biomass fermentation gas, cement gas and incinerator fumes.

Other features and advantages of the invention will be better understood and will become clear from reading the description given below.

In order to reduce the degradation of an absorbent solution, the inventors have shown that the degradation of an absorbent solution comprising organic compounds provided with an amine function in aqueous solution is substantially reduced in the presence of a small amount of inhibiting additives. degradation described below.

The degradation inhibiting additives according to the invention are nitroaromatic compounds defined by the general formula: in which each of the radicals R1 to R6 is chosen from one of the following 7 groups A, B, C, D, E, F and G and following the rules specified below. Group A: a nitro group -NO2; group B: a hydrogen atom; group C: a group WX in which W is an oxygen atom or a sulfur atom; X is chosen from one of the following elements : a hydrogen atom o a hydrocarbon radical containing 1 to 12 carbon atoms, saturated or unsaturated, linear, branched, cyclic, heterocyclic or aromatic, possibly containing heteroatoms, halogens, and possibly containing hydroxyl functions, ketones, carboxylic acids or nitriles o an alkaline or alkaline-earth element o a monovalent or multivalent metal o an ammonium NH4 + cation or resulting from the protonation of an amine function o a phosphonium cation

Where group D is: ## STR2 ## wherein V is selected from a hydrogen atom

A hydrocarbon radical containing 1 to 12 carbon atoms, saturated or unsaturated, linear, branched, cyclic, heterocyclic or aromatic, which may optionally contain heteroatoms, halogens, and possibly containing hydroxyl, ketone, carboxylic or nitrile functions; an alkaline or alkaline-earth element o a monovalent or multivalent metal o an ammonium cation NH4 + or resulting from the protonation of an amine function o a phosphonium cation

## STR2 ## in which Y is selected from: a hydrogen atom o a hydrocarbon radical containing 1 to 12 carbon atoms, saturated or unsaturated, linear, branched, cyclic, heterocyclic or aromatic, optionally contain heteroatoms, halogens, and possibly containing hydroxyl, ketone, carboxylic or nitrile functions, or an alkaline or alkaline earth element, a monovalent or multivalent metal, an ammonium NH4 + cation or resulting from the protonation of an amine function, a phosphonium cation • Group F: a hydrocarbon radical containing 1 to 12 carbon atoms, saturated or unsaturated, linear, branched, cyclic, heterocyclic or aromatic, which may optionally contain heteroatoms, halogens, and possibly containing hydroxyl functions, ketones , carboxylic or nitrile. Group G: a radical corresponding to the following general formula: R 10 in which Z is a covalent bond, an oxygen atom or a sulfur atom, an N-R 12 unit in which R 12 is a hydrogen atom or a hydrocarbon radical comprising 1 to 12 carbon atoms, o a linear or branched hydrocarbon-based unit containing 1 to 20 carbon atoms and preferably 1 to 10 carbon atoms and which may optionally be bonded to hetero atoms. Each of the radicals R 7 to R 11 is chosen from one of the following 6 groups A, B, C, D, E and F and respecting the rules specified below.

According to the invention, the radicals R 1 to R 6 are chosen taking into account the following rules: 1. between one and three radicals R 1 to R 6 correspond to the definition of group A 2. at least three radicals R 1 to R 6 are chosen independently from groups B to G 3. at most three radicals R1 to R6 correspond to the definition of group C 4. at most three radicals R1 to R6 correspond to the definition of group D 5. at most three radicals R1 to R6 correspond to the definition of group E 25 6. not more than three radicals R1 to R6 correspond to the definition of group G

According to the invention, the radicals R7 to R11 are chosen taking into account the following rules: 7. between one and three radicals R7 to R11 correspond to the definition of the group A 8. at least three radicals R7 to R11 are chosen independently from groups B to F 9. at most three radicals R7 to R11 correspond to the definition of group C 10. at most three radicals R7 to R11 correspond to the definition of group D 11. at most three radicals R7 to R1 correspond to the definition of the group E According to a first embodiment, in the definition of the general formula of the degradation inhibitor additives according to the invention, R1 to R6 are independent, that is to say that they are not interconnected . However, according to a second embodiment, in the case where two of R1 to R6 are selected from the group G, these two radicals may be linked together by a covalent bond so as to form a saturated, unsaturated or aromatic substituted ring. or not, or a heterocycle, the ring consisting of 5, 6, 7 or 8 atoms, in accordance with the rules of organic chemistry.

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, the gases of fermentation of biomass, cement gas, incinerator fumes. These gaseous effluents contain one or more of the following acidic compounds: CO2, H2S, mercaptans, COS, SO2, NO2, 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 can comprise between 50% and 80% of nitrogen, between 5% and 20% of carbon dioxide, between 1% and 10% of oxygen.

The implementation of an absorbent solution for deacidifying a gaseous effluent is generally carried out by performing an absorption step followed by a regeneration step. The absorption step consists of contacting the gaseous effluent with the absorbing solution. Upon contact, the organic compounds provided with an amine function of the absorbent solution react with the acidic compounds contained in the effluent so as to obtain a gaseous effluent depleted of acidic compounds and an acid-enriched absorbent solution. The regeneration step consists in particular in heating and, optionally, in expanding, the absorbent solution enriched in acidic compounds in order to release the acidic compounds in gaseous form. The regenerated absorbent solution, that is to say depleted in acidic compounds is recycled to the absorption step. The absorbent solution according to the invention comprises organic compounds in aqueous solution. In general, the organic compounds are amines, that is to say that they contain at least one amine function. The organic compounds may be in variable concentration, for example between 10% and 80% by weight, preferably between 20% and 60% by weight, in the aqueous solution. The absorbent solution may contain between 10% and 90% water. For example, the organic compounds are amines such as N, N, N ', N', N "-pentamethyldiethylenetriamine or piperazine, for example piperazine is used for the treatment of natural gas and for the decarbonation of combustion fumes. The organic compounds can also be alkanolamines such as monoethanolamine (MEA), diethanolamine (DEA), methyldiethanolamine (MDEA), diisopropanolamine (DIPA) or diglycolamine, preferably MDEA and DEA are commonly used for deacidification of natural gas The MEA is more particularly used for the decarbonation of combustion fumes The organic compounds may also be salts of amino acids such as the salts of glycine or taurine which are especially used for the capture of CO2 in the combustion fumes.

In addition, the absorbent solution according to the invention may contain compounds which physically absorb at least partially one or more acidic compounds of the gaseous effluent. For example, the absorbent solution may comprise between 5% and 50% by weight of absorbent compounds of a physical nature such as, for example, methanol, sulfolane or N-formyl morpholine.

Among all the molecules corresponding to the general formula described above, the following degradation inhibiting additives are preferably used: ortonitrobenzoic acid, metanitrobenzoic acid, paranitrobenzoic acid, 2,4-dinitrobenzoic acid , ortonitrophenol, metanitrophenol, paranitrophenol, 2,4,6-trinitrophenol and salts of the above-mentioned elements. The salts of the degradation-inhibiting compounds according to the invention can be obtained for example by their neutralization with the aid of an alkaline, alkaline earth or metal or ammonium hydroxide or carbonate or with the aid of an amine present in the absorbent solution.

The degradation inhibitor compounds listed in the preceding paragraph are particularly well suited to the prevention of the degradation of amines in aqueous solution implemented in a process for capturing CO2 contained in combustion fumes.

In order to limit the degradation of an absorbent solution composed of amine, in particular alkanolamine, for example monoethanolamine (MEA), in aqueous solution, in particular for capturing the CO 2 from the combustion fumes, it is preferable to use one of the compounds: ortonitrobenzoic acid, metanitrobenzoic acid, paranitrobenzoic acid and 2,4-dinitrobenzoic acid, as well as their salts such as, for example, sodium, potassium, zinc or ammonium salts, such as for example: the sodium salt of ortonitrobenzoic acid, the sodium salt of metanitrobenzoic acid, the sodium salt of paranitrobenzoic acid, the potassium salt of paranitrobenzoic acid or the zinc salt of the acid paranitrobenzoic.

Preferably, according to the invention, use is made of paranitrobenzoic acid or the sodium salt of paranitrobenzoic acid to limit the degradation of an amine, in particular MEA, in aqueous solution used to deacidify a gaseous effluent, particularly in the context of the capture of CO2 contained in combustion fumes.

The absorbent solution according to the invention comprises an amount of degradation inhibiting additives defined by the general formula described above. The absorbent solution may comprise one or more different degradation inhibiting additives corresponding to said general formula. In addition, in the absorbent solution, the degradation inhibitor additives according to the invention may be combined with other degradation inhibitor compounds of different chemical families. According to the invention, the absorbent solution comprises between 5 ppm and 5% by weight of degradation inhibiting additives according to the invention, preferably from 50 ppm to 2% by weight, and an excellent content of degradation inhibiting additives in the solution being between 100 ppm and 1% by weight.

The examples presented below make it possible to compare and illustrate the performance of the degradation inhibitor additives according to the invention, in terms of reducing the degradation of amines in aqueous solution. The degradation tests of an amine in aqueous solution are carried out according to the following procedure. 100 ml of 30% w / w amine solution in deionized water are placed in a glass reactor surmounted by a condenser to prevent evaporation of the water. According to the tests, the incorporated degradation inhibiting additive 25 is varied in the aqueous amine solution. The reactor is heated to 80 ° C in an electric heating block. The solution is stirred at 1200 rpm by a magnetic bar. The presence of counter-blades prevents the formation of a vortex.

7 Nl / h of atmospheric air, that is to say of unpurified ambient air, are brought into contact with the solution by means of a dip tube for 7 days at atmospheric pressure. An ion chromatographic analysis of the thus degraded solution is then carried out. The analytical method uses an anion exchange column, potash eluent and conductimetric detection. This analysis makes it possible to quantify the acetate, oxalate and formate ions which are the species generally followed by those skilled in the art because they testify to the degree of degradation of the amine. The ppm contents of these different anions are given in the table below in the case of a 30% weight aqueous solution of MEA (monoethanolamine) without a degradation inhibitor additive, with 10% by weight of an additive inhibiting agent. conventional degradation (hydroquinone) and with 1% by weight of a degradation inhibitor additive according to the invention, the sodium salt of paranitrobenzoic acid. Name of the additive Additive Acetate Formiate Oxalate% by weight ppm ppm ppm - 0% 51 3910 197 hydroquinone 1% 189 17063 3450 the sodium salt of 1% acid ND 1404 <66 paranitrobenzoic acid ND: value not determined because less than detection limit of the analysis method. This comparative example shows that the use of a conventional degradation inhibiting additive, hydroquinone, aggravates the degradation of MEA while the use of a degradation inhibiting additive according to the invention makes it possible to greatly limit the degradation of the MEA under the conditions of the example. 25

Claims (11)

CLAIMS1) Absorbent solution for absorbing the acidic compounds of a gaseous effluent, said solution comprising: a) at least one amine, b) water, c) at least one degradation inhibiting compound for limiting the degradation of said amine, the degradation inhibitor compound having the general formula: wherein each of R 1 to R 6 is selected from one of A, B, C, D, E, F and G, wherein group A contains a group • Group B contains a hydrogen atom, • Group C contains a group ùW-X in which • W is an oxygen atom or a sulfur atom, • X is chosen from one of the following elements: a hydrogen atom, a hydrocarbon radical containing from 1 to 12 carbon atoms, an alkaline or alkaline earth element, a monovalent or multivalent metal, an ammonium NH 4 + cation or resulting from the protonation of a function amine, o a phosphonium cation, O ùc • the group D conti wherein V is selected from one of the following: o a hydrogen atom o a hydrocarbon radical having 1 to 12 carbon atoms o an alkaline or alkaline earth element o a metal monovalent or multivalent, o an ammonium cation NH4 + or resulting from the protonation of an amine function, o a phosphonium cation, OII ùSùOuyYII • the group E contains a group O in which Y is selected from one of the following: o a hydrogen atom, a hydrocarbon radical containing from 1 to 12 carbon atoms, an alkaline or alkaline earth element, a monovalent or multivalent metal, an ammonium NH4 + cation or resulting from the protonation of an amine function , o a phosphonium cation, • the group F contains a hydrocarbon radical containing from 1 to 12 carbon atoms, • Group G contains a radical corresponding to the following general formula: 1725 in which Z is a covalent bond, o an atom of Oxygen e or a sulfur atom, o an N-R12 unit in which R12 is a hydrogen atom or a hydrocarbon radical comprising 1 to 12 carbon atoms, o a linear or branched hydrocarbon unit containing 1 to 20 carbon atoms, and wherein, the radicals R1 to R6 are selected having regard to the following rules: 1. between one and three radicals R1 to R6 correspond to the definition of group A, 2. at least three radicals R1 to R6 are independently selected from groups B to G, 3. not more than three radicals R1 to R6 correspond to the definition of group C, 4. at most three radicals R1 to R6 correspond to the definition of group D, 5. at most three radicals R1 to R6 correspond to the definition of group E, 6. at most three radicals R1 to R6 correspond to the definition of the group G, and in which, the radicals R7 to R11 are chosen taking into account the following rules: 7. between one and three radicals R7 to R11 correspond to the definition of group A, 8. at least three radicals R7 to R11 are independently selected from groups B to F, 9. at most three radicals R7 to R11 correspond to the definition of group C, 10. not more than three radicals R7 to R11 correspond to the definition of group D, R11 v R R10 18 19 11. at most three radicals R7 to R11 correspond to the definition of group E. 2) Absorbent solution according to claim 1, wherein at least one of the radicals R1, R2, R3, R4, R5, R6, R7, R8 , R9, R10, R11, R12, X, V, Y and Z is a hydrocarbon group containing from 1 to 12 carbon atoms and additionally contains at least one of the following: a heteroatom, a halogen, a hydroxyl function , a ketone function, a carboxylic function or a nitrile function. 3) Absorbent solution according to one of claims 1 and 2, wherein two radicals among R1, R2, R3, R4, R5, R6 belong to the group F and are interconnected by a covalent bond so as to form a cycle constituted from 5 to 8 atoms. 4) Absorbent solution according to one of claims 1 to 3, wherein at least one of R1, R2, R3, R4, R5 and R6 belongs to the group G, and wherein two radicals among R7, R8, R9, Rio and R11 belong to the group F and are linked together by a covalent bond so as to form a ring consisting of 5 to 8 atoms. 5) Absorbent solution according to one of the preceding claims, wherein the solution comprises between 10% and 80% by weight of amine, between 10% and 90% of water and between 5 ppm and 5% by weight of degradation inhibitor compound. . 6) Absorbent solution according to one of the preceding claims, wherein the degradation inhibiting compound is selected from the group containing: ortonitrobenzoic acid, a salt of ortonitrobenzoic acid, metanitrobenzoic acid, a salt of the acid metanitrobenzoic acid, paranitrobenzoic acid, a salt of paranitrobenzoic acid, 2,4-dinitrobenzoic acid, a salt of 2,4-dinitrobenzoic acid, ortonitrophenol, a salt of ortonitrophenol, metanitrophenol, a salt of metanitrophenol, paranitrophenol, a salt of paranitrophenol, 2,4,6-trinitrophenol and a salt of 2,4,6-trinitrophenol. 7) Absorbent solution according to one of the preceding claims, wherein the amine is selected from the group containing: N, N, N ', N', N "-pentamethyldiethylenetriamine, piperazine, monoethanolamine, diethanolamine, methyldiethanolamine, diisopropanolamine, diglycolamine, a salt of glycine and a salt of taurine 8) An absorbent solution according to one of the preceding claims wherein the amine is monoethanolamine and wherein the degradation inhibiting compound is selected Among the paranitrobenzoic acid or the sodium salt of paranitrobenzoic acid 9) Process for absorbing acidic compounds contained in a gaseous effluent, wherein the gaseous effluent is brought into contact with an absorbent solution according to one of the claims. 1 to 8. 10) The process according to claim 9, wherein the aqueous solution is used to absorb acidic compounds contained in one of the effluents of the group containing the e natural gas, combustion fumes, syngas, refinery gases, tail gases from the Claus process, biomass fermentation gases, cement gases and incinerator fumes.