EP2771095A1

EP2771095A1 - Absorbent tertiary monoalkanolamine solution belonging to the 3-alcoxypropylamine family, and method for removing acidic compounds contained in a gas effluent

Info

Publication number: EP2771095A1
Application number: EP12775741.7A
Authority: EP
Inventors: Bruno Delfort; Dominique Le Pennec; Julien Grandjean
Original assignee: IFP Energies Nouvelles IFPEN
Current assignee: IFP Energies Nouvelles IFPEN
Priority date: 2011-10-28
Filing date: 2012-09-28
Publication date: 2014-09-03
Also published as: FR2981860B1; US9486737B2; FR2981860A1; US20140301930A1; WO2013060944A1

Abstract

The absorbent solution for removing acidic compounds contained in a gas effluent comprises water and at least one amine that is selected from among tertiary monoalkanolamines that contain an etheric function and belong to the 3-alcoxypropylamine family having general formula (A). The method for removing the acidic compounds contained in a gas effluent involves placing a gas effluent 1 into the column C1 together with the absorbent solution 4.

Description

ABSORBENT SOLUTION BASED ON TERTICAL MONOALCANOLAMINES BELONGING TO THE FAMILY OF 3-ALCOXYPROPYLAMINES AND PROCESS FOR REMOVING ACIDIC COMPOUNDS CONTAINED IN A

EFFLUENT GASEOUS

The present invention relates to the field of deacidification processes of a gaseous effiuent. The invention is advantageously applicable to the treatment of industrial gas and natural gas. Absorption processes using an aqueous amine solution are commonly used to remove the acidic compounds (in particular CO ₂ , H ₂ S, COS, CS ₂ , SO ₂ and mercaptans) present in a gas. The gas is deacidified by contact with the absorbent solution, and the absorbent solution is thermally regenerated. For example, US 6,852,144 discloses a method for removing acidic compounds from hydrocarbons. The method uses a water-N-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. A limitation of the absorbent solutions commonly used in deacidification applications is an insufficient selectivity of H2S absorption relative to C0 ₂ . In fact, in certain cases of deacidification of natural gas, selective removal of H ₂ S is sought by limiting the absorption of CO2 as much as possible. This constraint is particularly important for gases to be treated already containing a CO ₂ content less than or equal to the desired specification. A maximum absorption capacity of H ₂ S is then sought with a maximum selectivity of H2S absorption with respect to CO ₂ . This selectivity makes it possible to maximize the quantity of treated gas produced and to recover an acid gas at the outlet of the regenerator having the highest possible concentration of H ₂ S, which limits the size of the units of the sulfur chain downstream of the treatment and guarantees better functioning. In some cases, a unit H2S enrichment is required to concentrate the acid gas in H2S. In this case, the most selective amine is also sought. Tertiary amines, such as N-methyldiethanolamine, or congested having slow reaction kinetics with CO2 are commonly used, but have limited selectivities at high H ₂ S loading rates.

Another limitation of the absorbent solutions commonly used in total deacidification applications is slow CO ₂ or COS capture kinetics. In the case where the desired specifications on the C0 ₂ or in COS are very advanced, one seeks a kinetics of reaction as fast as possible so as to reduce the height of the absorption column, this equipment under pressure, typically between 20 and 90 bar, representing a significant part of the process investment costs.

Whether maximum CO ₂ and maximum COS capture kinetics are sought in a total deacidification application, or a minimum CO ₂ capture kinetics in a selective application, it is always desirable to use an absorbent solution having the greatest cyclic capacity. possible. This cyclic capacity, denoted by Δα, corresponds to the difference in charge ratio (a designating the number of moles of acidic compounds absorbed n acid _gas per kilogram of absorbing solution) between the absorbent solution supplying the absorption column and the absorbent solution withdrawn in bottom of said column. Indeed, the more the absorbent solution has a high cyclic capacity, the more the flow of absorbent solution that must be used to deacidify the gas to be treated is limited. In gas treatment processes, the reduction of the absorbent solution flow rate also has a strong impact on the reduction of investments, especially in the dimensioning of the absorption column.

Another essential aspect of industrial gas treatment or flue gas treatment operations is the regeneration 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. Another limitation of absorbent solutions commonly used today is an energy consumption necessary for the regeneration of the solvent which is too important. This is particularly true in the case where the partial pressure of acid gases is low. For example, for an aqueous solution of 2-aminoethanol (PU monoethanolamine or ethanolamine or MEA) at 30% weight used for the capture of CO2 in post-combustion in a thermal power plant smoke, where the partial pressure of CO2 is from order of 0.12 bar, the regeneration energy represents about 3.7 GJ per tonne of CO2 captured. Such energy consumption represents a considerable operating cost for the CO2 capture process.

It is well known to those skilled in the art that the energy required for the regeneration by distillation of an amine solution can be broken down into three different positions: the energy required to heat the solvent between the head and the bottom of the regenerator, the energy necessary to lower the partial pressure of acid gas in the regenerator by vaporization of a stripping gas, and finally the energy necessary to break the chemical bond between the amine and the CO2.

These first two stations are inversely proportional to the flow rates of absorbent solution that it is necessary to circulate in the unit to achieve a given specification. To reduce the energy consumption associated with the regeneration of the solvent, it is therefore preferable once again to maximize the cyclic capacity of the solvent.

It is difficult to find compounds, or a family of compounds, allowing the various deacidification processes to operate at lower operating costs (including regeneration energy) and investments (including the cost of the absorption column).

It is well known to those skilled in the art that tertiary amines or secondary amines with a severe steric hindrance have a kinetics of uptake of C0 ₂ slower than primary or secondary amines uncrowded. In contrast, tertiary or secondary amines with a Severe steric hindrance has instantaneous H 2 S sensing kinetics, which allows for selective removal of PhfeS based on distinct kinetic performance.

Among the applications of these tertiary or hindered amines, the document FR 2 100 475 describes a process for selectively absorbing sulfurous gases by an absorbent compound in aqueous solution, the compound having a general formula which may contain a tertiary amine of which one of the substituents contains an ether function but excluding the alkanolamines.

US Pat. No. 4,405,81 describes a process for the selective removal of H ₂ S in gases containing H ₂ S and CO 2 by an absorbent containing tertiary alkanolamine amines which may or may not contain one or more ether functions which in this case are necessarily on the hydroxyl substituent. The inventors have discovered that the tertiary monoalkanolamine type amines containing or without an ether function are not equivalent in terms of performance for their use in absorbent solution formulations for the treatment of acid gases in an industrial process. The present invention relates to the use of tertiary monoalkanolamines containing an ether function and belonging to the family of 3-alkoxypropylamines.

In general, the subject of the present invention is an absorbent solution for removing acidic compounds contained in a gaseous effluent, comprising:

- some water;

at least one amine corresponding to the following general formula (A): in which R 1 is an alkyl radical containing from 1 to 6 carbon atoms,

R2, R3 and R4 are independently selected from a hydrogen atom and an alkyl radical of 1 to 6 carbon atoms,

R5 is chosen indifferently from a hydrogen atom and an alkyl radical containing from 1 to 6 carbon atoms,

R6 is an alkyl radical containing from 1 to 6 carbon atoms.

According to the invention, the amine may be chosen from the following compounds: N-methyl-N- (3-methoxypropyl) -2-aminoethanol, N-methyl-N- (3-methoxypropyl) -1-amino 2-propanol, N-methyl-N- (3-methoxypropyl) -1-amino-2-butanol, N-ethyl-N- (3-methoxypropyl) -2-aminoethanol, N-ethyl-N- ( 3-methoxypropyl) -1-amino-2-propanol, N-ethyl-N- (3-methoxypropyl) -1-amino-2-butanol, N-isopropyl-N- (3-methoxypropyl) -2-aminoethanol N-isopropyl-N- (3-methoxypropyl) -1-amino-2-propanol and N-isopropyl-N- (3-methoxypropyl) -1-amino-2-butanol. Preferably, the amine is N-methyl-N- (3-methoxypropyl) -2-aminoethanol.

The absorbent solution may comprise between 10% and 90% by weight of said amine and between 10% and 90% by weight of water.

The absorbent solution may further comprise a non-zero amount and less than 20% by weight of a primary or secondary amine compound.

Said primary or secondary amine compound may be chosen from the group consisting of:

- MonoEthanolAmine,

- N-butylethanolamine - Aminoethylethanolamine,

- Diglycolamine,

- Piperazine,

N- (2-hydroxyethyl) piperazine,

N- (2-aminoethyl) piperazine,

- Morpholine,

3- (metylamino) propylamine.

-1,6-hexanediamine

N, N'-dimethyl-1,6-hexanediamine

The absorbent solution may further comprise a physical solvent selected from methanol and sulfolane.

The subject of the invention is also a process for eliminating the acidic compounds contained in a gaseous effluent, in which an absorption step of the acidic compounds is carried out by contacting the gaseous effluent with an absorbent solution according to the invention. .

According to the invention, the absorption step of the acidic compounds can be carried out at a pressure of between 1 bar and 120 bar, and at a temperature of between 20 ° C. and 100 ° C.

After the absorption step, it is possible to obtain a gaseous effluent depleted of acid compounds and an absorbent solution loaded with acidic compounds, and it is possible to carry out at least one regeneration step of the absorbent solution loaded with acidic compounds.

The regeneration step can be carried out at a pressure of between 1 bar and 10 bar and a temperature of between 100 ° C. and 180 ° C.

The gaseous effluent may be chosen from natural gas, synthesis gases, combustion fumes, refinery gases, acid gases from an amine unit, gases from a tail reduction unit of Claus process, biomass fermentation gases, cement gases, incinerator fumes. In the process according to the invention, the gaseous effluent may be a natural gas comprising H ₂ S and CO ₂ , used for the selective removal of H ₂ S with respect to C0 ₂ . The use of the 3-alkoxypropylamine compounds according to the invention makes it possible to obtain greater acid gas absorption capacities than the reference amines. This performance is increased due to greater basicity.

Moreover, the compounds according to the invention have a selective absorption of H 2 S with respect to CO _{2 which is} greater than the reference amines.

Other features and advantages of the invention will be better understood and will become clear from reading the description given hereinafter with reference to FIG. 1 showing a schematic diagram of an acid gas treatment process.

The present invention provides an aqueous solution comprising at least one compound belonging to the family of 3-alkoxypropylamines to remove the acidic compounds contained in a gaseous effluent.

Synthesis of a molecule according to the general formula of the invention

The molecules of the invention can be synthesized using any pathway permitted by organic chemistry. Among these, we can cite one without being exhaustive.

It is represented by the following diagram and calls some comments.

It is possible to prepare the 3-alkoxypropylamines according to the invention by a procedure that generates no salt and is compatible with industrial development. This procedure uses a sequence of four reactions, one of which generates a co-product that is water. CN R-- OH

H ₂

0 H ₂ O

The starting material used is acrylonitrile which is an industrial molecule, precursor of polymers, abundantly available worldwide and the cost is low. The first step consists in the addition of a molecule of an alcohol of formula R 1 -OH and an acrylonitrile molecule to lead to 3-alkoxypropionitrile (reaction 1) according to a well known and abundantly documented reaction. This reaction is especially described in Journal of the American Chemical Society, 725-731 (1944), and ibid 118 (49), 12368-12375 (1996). This reaction, which is an addition reaction, does not generate any by-products. It can be favored in the presence of bases. DE 2121325 (1972), for example, describes the synthesis of 3-methoxypropionitrile by the reaction of methanol and acrylonitrile in the presence of a triethanolamine derivative.

It may be advantageous in reaction 1 to operate with either an excess of acrylonitrile or an excess of alcohol. Any one of the excess reagents is easily separated, for example, by distillation at the end of reaction 1 and then recycled back into the process. Therefore in this step, the possible use of the use of an excess of one or other of the reagents to achieve the maximum conversion under advantageous conditions of time and temperature is fully compatible with the described process. .

The second step is the hydrogenation of the 3-alkoxypropionitrile to give the 3-alkoxypropylamine according to the well known reaction of reduction of nitrile functions to primary amine functions (reaction 2). This reaction can be carried out with any means known to those skilled in the art in respect of organic chemistry. It can be carried out, for example, by means of a suitable hydride such as mixed hydride of lithium and aluminum. It can according to the invention preferably be carried out in the presence of hydrogen, or in the presence of hydrogen and ammonia by means of a suitable catalyst such as for example nickel derivatives. This reaction is a reaction of addition of hydrogen to the nitrile function and generates no byproduct.

OF Wiedman et al. Describe in J. Am. Chem. Soc., (1945), p1194 a general method of hydrogenating dicyanoethyl ether to diaminopropyl ether in the presence of Raney nickel and ammonia at 50 to 150 bar at a temperature of 80 ° C to 125 ° C. GB 869405 (1961) for example describes the hydrogenation of 3-methoxypropionitrile to 3-methoxypropanamine in the presence of hydrogen, ammonia and Raney nickel at 150 ° C at 200 bar.

US 3253040 (1966) for example describes the hydrogenation of 3-methoxypropionitrile to 3-methoxypropanamine in the presence of hydrogen and Raney nickel at 110 ° C under 10 bar.

US Pat. No. 3,372,195 (1968), for example, describes the hydrogenation of 3-methoxypropionitrile to 3-methoxypropanamine in the presence of hydrogen and ammonia and a Ruthenium catalyst at 125 ° C. under 70 bar.

The third step consists in the reaction of the 3-alkoxypropylamine previously obtained with a substituted or unsubstituted epoxide according to a well-known mono-addition reaction (reaction 3). the product obtained is an N- (3-alkoxypropyl) -2-aminoalkanol. It may be advantageous to obtain the desired mono-addition compound to operate with an excess of 3-alkoxypropylamine which is subsequently separated for example by distillation.

Finally, the fourth step consists in the alkylation of the previously obtained N- (3-alkoxypropyl) -2-aminoalkanol to obtain an N-alkyl-N- (3-alkoxypropyl) -2-aminoalkanol which is the product of the invention. (reaction 4).

This alkylation of the nitrogen atom can be carried out using any method permitted by organic chemistry and known to those skilled in the art. For example, the so-called Eschweiler-Clarke methylation reaction which requires a mixture of formaldehyde and formic acid. The Leuckart reaction which uses a ketone or an aldehyde and an ammonium formate can also be mentioned. It is preferred for the invention to effect alkylation by the so-called catalytic reductive alkylation reaction of the amines by means of an aldehyde or a ketone in the presence of hydrogen and a suitable catalyst. Among other things, the catalytic reductive alkylation reactions of amines have the advantage of being rapid and selective and of producing only by-product only water. They are widely used in industrial processes for manufacturing alkylamines such as methylamines or ethylamines and are compatible with the technologies used industrially.

For example, the methylation of N- (3-methoxypropyl) -2-aminoethanol to N-methyl-N- (3-methoxypropyl) -2-aminoethanol can be carried out in an autoclave reactor by reaction of N- (3-methoxypropyl) - 2-aminoethanol with excess formaldehyde under a hydrogen pressure of 20 bar at 120 ° C in 3 hours in the presence of a palladium on charcoal catalyst. The 13 C-NMR (CDCl3) characteristics of N-methyl-N- (3-methoxypropyl) -2-aminoethanol are as follows:

57.7 ppm: CH3-O-CH2-CH2-CH2-N (CH3) -CH2-CH2-OH

70.2 ppm: CH3-O-CH2-CH2-CH2-N (CH3) -CH2-CH2-OH

26.7 ppm: CH3-O-CH2-CH2-CH2-N (CH3) -CH2-CH2-OH

54.1 ppm: CH3-O-CH2-CH2-CH2-N (CH3) -CH2-CH2-OH

41.4 ppm: CH3-O-CH2-CH2-CH2-N (CH3) -CH2-CH2-OH

54.4 ppm: CH3-O-CH2-CH2-CH2-N (CH3) -CH2-CH2-OH

58.8 ppm: CH3-O-CH2-CH2-CH2-N (CH3) -CH2-CH2-OH

For example, the ethylation of N- (3-methoxypropyl) -2-aminoethanol to N-ethyl-N- (3-methoxypropyl) -2-aminoethanol can be carried out by following the same procedure but replacing the formaldehyde with acetaldehyde.

For example, the isopropylation of N- (3-methoxypropyl) -2-aminoethanol to N-isopropyl-N- (3-methoxypropyl) -2-aminoethanol can be carried out by following the same procedure but replacing the formaldehyde with acetone.

A variant of this access route to the molecules of the invention (not shown in the figure) may use acrylamide instead of acrylonitrile. The first step is an addition of the alcohol to the acrylamide leading to the 3-alkoxypropanamide which is then hydrogenated to 3-alkoxypropylamine in a second step. Steps 3 and 4 are the same as those previously described. 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, acid gases from an amine unit, gases from a reduction unit 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: C0 ₂ , H ₂ S, mercaptans, COS, CS ₂ , SO ₂ .

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. By way of illustration, the method according to the invention can be used to absorb at least 70%, preferably at least 80% or even at least 90% of the CO ₂ contained in the combustion fumes. These fumes generally have a temperature of between 20 and 60 ° C., a pressure of between 1 and 5 bar and may comprise between 50 and 80% of nitrogen, between 5 and 40% of carbon dioxide, and between 1 and 20% of carbon dioxide. oxygen, and some impurities such as SOx and NOx, if they have not been removed upstream of the deacidification process. In particular, the process according to the invention is particularly well adapted to absorb the CO ₂ contained in combustion fumes comprising a low CO ₂ partial pressure, for example a CO ₂ partial pressure of less than 200 mbar.

The process according to the invention can be used to deacidify a synthesis gas. The synthesis gas contains carbon monoxide CO, hydrogen H ₂ (generally in a ratio H ₂ / CO equal to 2), water vapor (generally at saturation at the temperature where the washing is carried out) and carbon dioxide C0 ₂ (of the order of ten percent). The pressure is generally between 20 and 30 bar, but can reach up to 70 bar. It contains, in addition, sulfur impurities (H ₂ S, COS, etc.), nitrogen (NH ₃ , HCN) and halogenated impurities. The process according to the invention can be implemented to deacidify a natural gas. Natural gas consists mainly of gaseous hydrocarbons, but can contain several of the following acidic compounds: CO2, H ₂ S, mercaptans, COS, CS2. The content of these acidic compounds is very variable and can be up to 40% for C0 ₂ and H ₂ S. 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 and 120 bar. The invention can be implemented to achieve specifications generally imposed on the deacidified gas, which are less than 2% of CO2, or even less than 50 ppm of CO2, to then achieve a liquefaction of natural gas and less than 4 ppm of h ^ S, and less than 50 ppm, or even less than 10 ppm, total sulfur volume.

Composition of the Absorbent Solution The absorbent solution according to the invention comprises:

a - water;

b - at least one amine chosen from tertiary monoalkanolamines containing an ether function and belonging to the family of 3-alkoxypropylamines corresponding to the following general formula (A):

wherein R1 to R6 are defined below.

R 1 is an alkyl radical containing 1 to 6 carbon atoms and preferably 1 to 2 carbon atoms.

R2, R3 and R4 are independently selected from a hydrogen atom or an alkyl radical containing 1 to 6 carbon atoms and preferably 1 to 2 carbon atoms.

Preferably, R2, R3 and R4 are hydrogen atoms. R5 is chosen indifferently from a hydrogen atom or an alkyl radical containing from 1 to 6 carbon atoms and preferably 1 to 2 carbon atoms.

Preferably, R5 is a hydrogen atom or an alkyl radical containing 1 to 2 carbon atoms.

R6 is an alkyl radical containing from 1 to 6 carbon atoms and preferably 1 to 3 carbon atoms.

The radical R6 can be defined more precisely by the general formula

In which R 7 and R 8 may each be a hydrogen atom or R 7 may be a hydrogen atom and R 8 selected from an alkyl radical containing from 1 to 5 carbon atoms or R 7 and R 8 may each be an alkyl radical containing from 1 to 4 carbon atoms in accordance with the definition of R6.

Preferably, R 6 is a methyl, ethyl, propyl or isopropyl radical.

In other words, the absorbent solution according to the invention comprises at least one amine corresponding to the general formula (A), in aqueous solution.

For example, the absorbent solution according to the invention may comprise an amine corresponding to formula (A), chosen from the following compounds:

Preferably, the absorbent solution according to the invention is composed of a solution of water mixed with the following amine:

N-methyl-N- (3-methoxypropyl) -2-aminoethanol The amines according to general formula (A) may be in variable concentration in the absorbent solution, for example between 10% and 90% by weight, preferably between 20% and 60% by weight, very preferably between 30% and 50% by weight. weight.

The absorbent solution may contain between 10% and 90% by weight of water, preferably between 40% and 80% by weight of water, very preferably from 50% to 70% water.

In one embodiment, the amines according to the general formula (A) can be formulated with a compound containing at least one primary or secondary amine function. For example, the absorbent solution comprises up to a concentration of less than 20% by weight, preferably less than 15% by weight, preferably less than 10% by weight of said compound containing at least one primary or secondary amine function. Preferably, the absorbent solution comprises at least 0.5% by weight of said compound containing at least one primary or secondary amine function. Said compound makes it possible to accelerate the absorption kinetics of the COS and, in certain cases, the CO2 contained in the gas to be treated

A non-exhaustive list of compounds containing at least one primary or secondary amine function that may be included in the formulation is given below:

- Monoethanolamine,

- N-butylethanolamine

- Aminoethylethanolamine,

- Diglycolamine,

- Piperazine,

N- (2-hydroxyethyl) piperazine,

N- (2-aminoethyl) piperazine,

- Morpholine,

3- (methylamino) propylamine.

-1,6-hexanediamine

N, N'-dimethyl-1,6-hexanediamine The absorbent solution may further comprise a physical solvent such as, for example, methanol and sulfolane.

Process for removing acidic compounds in a gaseous effluent

The implementation of an aqueous solution comprising a compound according to general formula (A) for deacidifying a gaseous effluent is carried out schematically by performing an absorption step followed by a regeneration step, for example as represented by Figure 1.

With reference to FIG. 1, the absorption step consists of bringing the gaseous effluent 1 into contact with the absorbent solution 4. The gaseous effluent 1 is introduced at the bottom of C1, the absorbent solution is introduced at the head of C1 . Column C1 is provided with means for contacting gas and liquid, for example loose packing, structured packing or trays. During contact, the amine functions of the molecules according to the general formula (A) of the absorbent solution react with the acidic compounds contained in the effluent so as to obtain a gaseous effluent depleted of acidic compounds 2 discharged at the head of C1 and a solution Absorbent enriched in acidic compounds 3 discharged at the bottom of C1 to be regenerated.

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 absorbent solution enriched in acidic compounds 3 is introduced into the heat exchanger E1, where it is heated by the stream 6 from the regeneration column C2. The heated solution at the outlet of E1 is introduced into the regeneration column C2.

The regeneration column C2 is equipped with internal contacting between gas and liquid, for example trays, loose or structured packings. The bottom of the C2 column is equipped with an R1 reboiler which brings the heat required for regeneration by vaporizing a fraction of the absorbing solution. In the column C2, under the effect of contacting the absorbent solution arriving by 5 with the vapor produced by the reboiler, the acid compounds are released in gaseous form and discharged at the top of C2 through the pipe 7. The solution regenerated absorbent 6, that is to say depleted in acidic compounds 6 is cooled in E1, then recycled in column C1 through line 4.

The absorption step of the acidic compounds can be carried out at a pressure in C1 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 the treatment of industrial fumes, and at a temperature in Cl between 20 ° C and 100 ° C, preferably between 30 ° C and 90 ° C, or between 30 and 60 ° 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.

Regeneration can be carried out at a pressure in C2 of between 1 bar and 5 bar, or even up to 10 bar and at a temperature in C2 of between 100 ° C. and 180 ° C. Preferably, the regeneration temperature in C2 is between 155 ° C. and 180 ° C. in the case where it is desired to reinject the acid gases.

Examples: Example 1: Synthetic procedure

This example illustrates the synthesis of the molecules of the invention as well as a molecule intended for a comparative example, according to the synthetic route previously described, it being understood that all the possibilities of synthesis of these molecules both at the level of the synthetic routes and the possible procedures are not described here. Synthesis of N-methyl-N- (3-methoxypropyl) -2-aminoethanol (for an example according to the invention)

In a first step, to a mixture of 3.22 moles of commercially available 3-methoxypropylamine diluted in 500 ml of water, 1.6 moles of ethylene oxide are added with stirring over 1 hour at a temperature not exceeding not 25 ° C and then stirring is continued for an additional hour at room temperature. After distillation of the water and excess 3-methoxypropylamine, 140 g of N- (3-methoxypropyl) -2-aminoethanol are collected between 120 ° C. and 124 ° C. under 20 mbar.

In a second step, 451 mmol of previously prepared N- (3-methoxypropyl) -2-aminoethanol, 2.25 moles of 37% formaldehyde in water and 0.5 g of a catalyst are introduced into an autoclave reactor. Pd / C. Hydrogen is introduced at a pressure of 20 bar and the medium is heated at a temperature of 80 ° C. for 4 hours. After returning to ambient temperature, the catalyst is filtered off and after distillation 52 g of a product whose NMR spectrum (CDCl3) is in conformity with that of N-methyl-N- (3-methoxypropyl) -2 are collected. aminoethanol and whose characteristics are as follows:

57.7 ppm: CH3-O-CH2-CH2-CH2-N (CH3) -CH2-CH2-OH

70.2 ppm: CH3-O-CH2-CH2-CH2-N (CH3) -CH2-CH2-OH

26.7 ppm: CH3-O-CH2-CH2-CH2-N (CH3) -CH2-CH2-OH

54.1 ppm: CH3-O-CH2-CH2-CH2-N (CH3) -CH2-CH2-OH

41.4 ppm: CH3-O-CH2-CH2-CH2-N (CH3) -CH2-CH2-OH

54.4 ppm: CH3-O-CH2-CH2-CH2-N (CH3) -CH2-CH2-OH

58.8 ppm: CH3-O-CH2-CH2-CH2-N (CH3) -CH2-CH2-OH

Synthesis of N-methyl-N- (2-methoxyethyl) -2-aminoethanol (for a comparative example)

2.64 moles of 2-methylaminoethanol and 0.529 moles of (2-chloroethyl) methyl ether, both of which are commercially available, are introduced into a reactor, and the medium is then heated at a temperature of 80 ° C. for 6 hours. After returning to at room temperature, the medium is neutralized with aqueous sodium hydroxide and then the water, the salt and the excess and residual reagents are eliminated and, after distillation, 30 g of a product whose NMR spectrum (CDCl3) is in conformity with that of N are collected. methyl-N- (2-methoxyethyl) -2-aminoethanol and whose characteristics are as follows:

56.2 ppm: CH3-O-CH2-CH2-N (CH3) -CH2-CH2-OH

69.8 ppm: CH3-O-CH2-CH2-N (CH3) -CH2-CH2-OH

57.9 ppm: CH3-O-CH2-CH2-N (CH3) -CH2-CH2-OH

42.2 ppm: CH3-O-CH2-CH2-N (CH3) -CH2-CH2-OH

58.4 ppm: CH3-O-CH2-CH2-N (CH3) -CH2-CH2-OH

59.0 ppm: CH3-O-CH2-CH2-N (CH3) -CH2-CH2-OH

EXAMPLE 2 Capacity and Selectivity of H 2 S Elimination of a Gaseous Effluent Containing H 2 S and CO 2 with a solution of N-methyl-N- (3-methoxypropyl) -2-aminoethanol:

An absorption test is carried out at 40 ° C. on aqueous amine solutions in a perfectly stirred open reactor on the gas side.

For each solution, the absorption is carried out in a liquid volume of

50 cm3 by bubbling a gaseous stream consisting of a nitrogen mixture: carbon dioxide: hydrogen sulfide 89: 10: 1 in volume proportions, a flow rate of 30NL / h for 90 minutes.

The resulting H2S loading rate (a = number of moles of hfeS / kg of solution) is measured at the end of the test as well as the absorption selectivity with respect to CO2.

This selectivity S is defined as follows: o _ <* 's _χ ₂ (concentration of the gas mixture in CQ ₂₎ _{in SQjt | es te} st _conditions described

C ₀₂ (Concentration of gaseous mixture in H ₂ S)

By way of example, it is possible to compare the degree of charge and the selectivity between an absorbent solution of N-methyl-N- (3-methoxypropyl) -2-aminoethanol at 50% by weight according to the invention and an absorbent solution of 47% by weight methyldiethanolamine (MDEA), a reference compound for the selective removal of h 2 S in natural gas treatment, as well as an absorbent solution of 50% tert-butyldiethanolamine (tBu-DEA), monoalkanoamine Tertiary according to the general formula of US Patent 4,405,811 and free of ether function. The solution according to the invention can also be compared to an absorbing solution N-methyl-N- (2-methoxyethyl) -2-aminoethanol, a tertiary monoalkanolamine containing an ether function but belonging to the family of 2-alkoxyethylamines distinct from 3-alkoxypropylamines. according to the invention.

The taxes

Compound Concentration T (° C) in H2S Selectivity

(Mol / kg)

MDEA

47% 40 0.16 6.3 tBu-DEA

50% 40 0.15 7.6

(according to the general formula of

US 4,405,811)

N-methyl-N- (2-methoxyethyl) -2-

50% 40 0.08 3.0 aminoethanol

N-methyl-N- (3-methoxypropyl) -2-aminoethanol 50% 40 0.21 11, 1

(according to the invention) This example illustrates the gains in the degree of charge and selectivity that can be achieved with an absorbent solution according to the invention, comprising 50% by weight of N-methyl-N- (3-methoxypropyl) -2-aminoethanol.

This example illustrates that not all tertiary monoalkanolamines are equivalent in terms of performance. Indeed, MDEA and tert-butyldiethanolamine (entry 2 of the table) do not contain ether function in contrast to the molecules of the invention.

This example also illustrates that tertiary monoalkanolamines containing an ether function are not all equivalent in terms of performance. In N-methyl-N- (2-methoxyethyl) -2-aminoethanol (entry 3 of the table), the amine is an alkoxyethylamine and not an alkoxypropylamine as in the invention. The example therefore demonstrates that the structure of the alkoxypropylamine according to the invention has particular and improved performances.

Claims

Absorbent solution for removing acidic compounds contained in gaseous effluent, comprising:

- some water;

at least one amine corresponding to the following general formula (A):

in which

R 1 is an alkyl radical containing from 1 to 6 carbon atoms,

R6 is an alkyl radical containing from 1 to 6 carbon atoms. An absorbent solution according to claim 1, wherein the amine is selected from the following compounds:

N-methyl-N- (3-methoxypropyl) -2-aminoethanol, N-methyl-N- (3-methoxypropyl) -1-amino-2-propanol, N-methyl-N- (3-methoxypropyl) 1-amino-2-butanol, N-ethyl-N- (3-methoxypropyl) -2-aminoethanol, N-ethyl-N- (3-methoxypropyl) -1-amino-2-propanol, N- ethyl-N- (3-methoxypropyl) -1-amino-2-butanol, N-isopropyl-N- (3-methoxypropyl) -2-aminoethanol, N-isopropyl-N- (3-methoxypropyl) -1- amino-2-propanol, and N-isopropyl-N- (3-methoxypropyl) -1-amino-2-butanol. Absorbent solution according to claim 1, wherein the amine is N-methyl-N- (3-methoxypropyl) -2-aminoethanol.

Absorbent solution according to one of claims 1 to 3, comprising between 10% and 90% by weight of said amine and between 10% and 90% by weight of water.

Absorbent solution according to one of the preceding claims, further comprises a non-zero amount and less than 20% by weight of a primary or secondary amine compound.

An absorbent solution according to claim 5, wherein said primary or secondary amine compound is selected from the group consisting of:

- MonoEthanolAmine,

- N-butylethanolamine

- Aminoethylethanolamine,

- Diglycolamine,

- Piperazine,

N- (2-hydroxyethyl) piperazine,

N- (2-aminoethyl) piperazine,

- Morpholine,

3- (metylamino) propylamine.

-1,6-hexanediamine

N, N'-dimethyl-1,6-hexanediamine

Absorbent solution according to one of the preceding claims, further comprising a physical solvent selected from methanol and sulfolane. 8. Process for removing acidic compounds contained in a gaseous effluent, in which a step of absorption of the compounds is carried out acids by contacting the gaseous effluent with an absorbent solution according to one of claims 1 to 7.

9. The method of claim 8, 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.

10. Method according to one of claims 8 and 9, wherein after the absorption step, there is obtained a gaseous effluent depleted of acidic compounds and an absorbent solution loaded with acid compounds, and performs at least one regeneration step of the absorbent solution loaded with acidic compounds.

11. The method of claim 10, wherein the regeneration step is carried out at a pressure between 1 bar and 10 bar and a temperature between 100 ° C and 180 ° C.

12. Method according to one of claims 8 to 11, wherein the gaseous effluent is selected from natural gas, synthesis gas, combustion fumes, refinery gases, acid gases from a unit to Amines, gases from a Claus process bottling reduction unit, biomass fermentation gases, cement gases, incinerator fumes. 13. Method according to one of claims 8 to 11, wherein the gaseous effluent is a natural gas comprising HfeS and CO2, implemented for the selective removal of PH2S with respect to CO2.