METHOD FOR THE PRODUCTION OF AMMONIA NITROGEN

Description

[0001] The present invention relates to a process for producing ammoniacal nitrogen involving the reduction of dinitrogen in the presence of a compound (I) comprising at least one element from group 13 of the periodic table, and a reducing agent; and the use of said compound (I) for the reduction of dinitrogen.

[0002] Nitrogen (N) plays an essential role in the composition of living matter. It is notably one of the major constituents of amino acids, proteins including enzymes, and nucleic acids making up DNA and RNA. It is also an essential nutrient for crop growth. However, even though nitrogen is very abundant on the surface of the globe (there is more nitrogen than carbon, hydrogen and phosphorus combined in the whole made up of the biosphere, the hydrosphere and the atmosphere), it is present mainly in the form of an extremely stable gas, dinitrogen (N 2 ). Humans can therefore only marginally benefit from such abundance.Only microorganisms such as Rhizobia involved in the symbiotic fixation of nitrogen by legumes are capable of using this form of nitrogen and transforming it into ammoniacal and then organic nitrogen, which can in turn be used by other living beings and transformed into other reactive forms of nitrogen.

[0003] To meet an increased demand for reactive nitrogen for food production from the industrial revolution at the end of the 19th century, two main processes have drastically changed this reactive nitrogen landscape. First, the increasingly massive use of fossil fuels (coal, oil, natural gas, etc.) for energy production, transport, industry and domestic activities has greatly increased the quantities of oxidized nitrogen present in the environment. The second process which has been the most decisive is the Haber-Bosch process allowing the synthesis of ammonia on an industrial scale, from nitrogen and dihydrogen (H 2 ) in the presence of a solid catalyst based in particular on iron. The production of ammonia NH 3 of approximately 200 million tons / year by this process has quantitatively exceeded symbiotic fixation since the end of the 20th century on a global scale and it is still exploited today.However, this Haber-Bosch process has the following disadvantages: it uses high pressures and temperatures, for example pressures between 100 and 300 bars and temperatures between 300 and 550°C, making this process extremely energy-intensive, requiring centralized and secure production, and involving high operating and transport costs. Furthermore, such a process generates very large quantities of carbon dioxide (around 1.5% of global CO2 production), leading to environmental problems, and its efficiency remains low (20%).

[0004] Research has been conducted on ammonia production processes using milder conditions such as electrochemical reduction, which involves applying an electrical potential to an electrocatalyst based on noble metals such as gold or ruthenium. However, yields remain low and raw materials are rare and extremely expensive. Other processes have been developed using organometallic complexes or compounds of transition metals. In particular, US patent 6,037,459 describes a process comprising a step of contacting with dinitrogen a compound corresponding to the formula M(NR 1 R 2 ) 3 in which M is a transition metal (egmolybdenum), R 1 and R 2 are selected from tertiary alkyl groups, phenyl groups and substituted phenyl groups, to form a metal complex with nitride ligands; and a step of reducing said complex in the presence of a hydrogen source to form ammonia. This process is carried out under ambient temperature and pressure conditions. However, US Patent 6,037,459 describes low yields and the formation of ammonia is not demonstrated. On the other hand, Légaré, MA. et al., Nat. Chem. 12, 1076-1080, discloses a process for producing NH4Cl comprising a step of contacting dinitrogen with (a) a compound having the formula R1R2MY in which M is boron B, Y is bromine Br, R1 is 2,3,5,6-tetramethylphenyl and R2 is 1-(2,6-diisopropylphenyl)-3,3,5,5 tetramethylpyrrolidine-2-ylidene, as well as with a mixture of (b) KC8 / B(OH)3, and (c) toluene as an organic solvent.This step is followed by a hydrolysis step with hydrochloric acid.

[0005] The aim of the present invention is therefore to overcome the drawbacks of the prior art and in particular to provide a simple, economical, industrializable process for producing ammoniacal nitrogen, using abundant raw materials, which can possibly be recycled, and which makes it possible to reduce carbon emissions.

[0006] The first subject of the invention is a process for producing ammoniacal nitrogen, characterized in that it comprises at least the following steps: i) a step of bringing a composition comprising a compound corresponding to the following formula (I): R 1< R 2< MY (I), a reducing agent, and an organic solvent, into contact with dinitrogen (N 2 ), said formula (I) being such that: M is an element from group 13 of the periodic table, preferably chosen from boron, aluminum, and a mixture thereof, R 1< and R 2< , identical or different, are chosen from an alkyl group, an aryl group, an aryl-alkyl group, an -OR group, and an -SR group, R being an alkyl group, an aryl group, or an aryl-alkyl group, and Y is a group chosen from a halogen -X, a -OR 3< group, a -SR 3< group, a triflate group, a mesylate group, and a triflimidate group, R 3< being an alkyl group, an aryl group, or a aryl-alkyl group, and ii) a hydrolysis step in an acid medium.

[0007] The process of the invention is simple, easy to implement, economical, and allows the production of ammoniacal nitrogen under relatively mild reaction conditions. In particular, the use of a compound of formula (I) as defined above allows the activation in a reducing medium of the triple bond of the dinitrogen and the formation of intermediate species which then lead by hydrolysis to ammoniacal nitrogen. Finally, the process is industrializable, uses abundant raw materials, possibly recyclable, and allows the environmental impact to be reduced. Step i) The compound of formula (I) R 1< R 2< MY

[0008] According to the invention, boron is particularly preferred as element M.

[0009] The compound of formula (I) R 1< R 2< MY is not a radical compound.

[0010] In the compound of formula (I), R 1< forms a single covalent bond with element M and R 2< forms a single covalent bond with element M. The groups R 1< and R 2<

[0011] R 1< and R 2< , identical or different, are chosen from an alkyl group, an aryl group, an aryl-alkyl group, a -OR group, and a -SR group, R being an alkyl group, an aryl group, or an aryl-alkyl group.

[0012] An alkyl group as R 1< and / or R 2< may be straight or branched, cyclic or non-cyclic. The alkyl group may comprise from 1 to 14 carbon atoms, and preferably from 2 to 10 carbon atoms. An alkyl group is preferably selected from ethyl, propyl, isopropyl, cyclohexyl, bicyclo[2.2.1]-2-heptyl, and isopinocampheyl. Among such groups, any of cyclohexyl, bicyclo[2.2.1]-2-heptyl, or isopinocampheyl is most preferred.

[0013] The alkyl group as R 1< and / or R 2< may comprise one or more heteroatoms, such as an oxygen atom, or a sulfur atom, provided that a carbon atom of the alkyl group is directly bonded to the element M of formula (I) and that none of the heteroatom(s) present in the alkyl group is directly covalently bonded to another heteroatom.

[0014] An aryl group as R 1< and / or R 2< may be substituted or unsubstituted. The aryl group may comprise from 6 to 30 carbon atoms, and preferably from 6 to 18 carbon atoms. An aryl group is preferably selected from a phenyl group, a -C 6 F 5 group, a 2,4,6-(Me) 3 -C 6 H 2 group, and a 2,4,6-(iPr) 3 -C 6 H 2 group. Among such groups, any of 2,4,6-(Me) 3 -C 6 H 2 or 2,4,6-(iPr) 3 -C 6 H 2 is most preferred.

[0015] The aryl group as R 1< and / or R 2< may comprise one or more heteroatoms, in particular when the aryl group is substituted (i.e. in the substituents of said aryl group), such as an oxygen atom or a nitrogen atom, it being understood that a carbon atom of the aryl group is directly linked to the element M of formula (I).

[0016] An aryl-alkyl group as R 1< and / or R 2< is a group comprising at least one alkyl group and at least one aryl group which are linked directly by a carbon (of the aryl group)-carbon (of the alkyl group) covalent bond, or via an oxygen atom or a nitrogen atom, the aryl and alkyl groups being as previously defined for the R 1< and R 2< groups. The alkyl-aryl group may be directly linked to element M of formula (I) by a carbon atom of the aryl group or by a carbon atom of the alkyl group.

[0017] An alkyl group R of the group -OR or -SR may be linear or branched, cyclic or non-cyclic. The alkyl group R may comprise from 1 to 10 carbon atoms, and preferably from 1 to 4 carbon atoms.

[0018] An aryl group R of the group -OR or -SR may be substituted or unsubstituted. The aryl group R may comprise from 6 to 30 carbon atoms, and preferably from 6 to 18 carbon atoms. An aryl group R is preferably selected from a phenyl group, a naphthyl group, an anthracenyl group or a pyrenyl group.

[0019] An aryl-alkyl group R of the group -OR or -SR is a group comprising at least one alkyl group and at least one aryl group which are linked directly by a carbon (of the aryl group)-carbon (of the alkyl group) covalent bond or via an oxygen atom, or a sulfur atom, the aryl and alkyl groups being as previously defined for the group R.

[0020] The R 1< and R 2< groups can be covalently linked, in particular via a carbon-carbon bond, to together form a divalent group, said groups R 1< and R 2< being as defined above. In this embodiment, the divalent group does not form a planar ring with the element M.

[0021] For example, the divalent group may be an alkyl group (i.e. R 1< and R 2< are alkyl groups), and preferably a 9-bicyclo[3.3.1]nonane group.

[0022] According to one embodiment of the invention, R 1< and R 2< , identical or different, are chosen from an alkyl group, an aryl group, and an aryl-alkyl group.

[0023] According to a preferred embodiment of the invention, at least one of the groups R 1< and R 2< is an alkyl group, and more particularly preferably, both groups R 1< and R 2< are alkyl groups.

[0024] According to a particularly preferred embodiment of the invention, R 1< and R 2< are identical.

[0025] The R 1< and R 2< groups of compound (I) are non-stabilizing groups. In other words, their function is not to stabilize the R 1< R 2< M° radical generated during the process, and consequently to make it more reactive towards the dinitrogen N 2 . Group Y

[0026] Y is a group selected from a halogen -X, a -OR 3< group, a -SR 3< group, a triflate group (-OSO 2 CF 3 ), a mesylate group (-OSO 2 CH 3 ), and a triflimidate group (NTf 2 or N(SO 2 CF 3 ) 2 ), R 3< being an alkyl, aryl, or aryl-alkyl group.

[0027] X is preferably a chlorine atom or a bromine atom, and particularly preferably a chlorine atom.

[0028] An R 3< alkyl group may be linear or branched, cyclic or non-cyclic. The R 3< alkyl group may comprise from 1 to 10 carbon atoms, and preferably from 1 to 4 carbon atoms.

[0029] An R 3< aryl group may be substituted or unsubstituted. The R 3< aryl group may comprise from 6 to 30 carbon atoms, and preferably from 6 to 18 carbon atoms. An R 3< aryl group is preferably selected from phenyl, 2,4,6-(Me) 3 -C 6 H 2 , 2,4,6-(iPr) 3 -C 6 H 2 and naphthyl groups.

[0030] An R 3< aryl-alkyl group is a group comprising at least one alkyl group and at least one aryl group which are linked directly by a carbon (of the aryl group)-carbon (of the alkyl group) covalent bond or via an oxygen atom, or a sulfur atom, the aryl and alkyl groups being as previously defined for the R 3< group.

[0031] Y is preferably a halogen X.

[0032] The Y group of compound (I) is a group with nucleofugal properties. In other words, its function is to facilitate the formation of the radical R 1 < R 2 < M°.

[0033] According to a particularly preferred embodiment of the invention, the compound of formula (I) is chosen from dialkylchloroboranes, dialkylbromoboranes, dialkylchloroaluminium compounds, and dialkylbromoaluminium compounds, such as the halides of diisopinocampheylborane, dicyclohexylborane, or bis(bicyclo[2.2.1]-2-heptyl)borane, or haloboranes based on 9-borabicyclo[3.3.1]nonane.

[0034] The compound of formula (I) has the advantages of being readily commercially available or readily synthetically accessible.

[0035] The compound of formula (I) has the characteristics of a Lewis acid, namely a chemical entity in which one of the atoms constituting it has an electronic gap.

[0036] The reducing agent may be chosen from potassium, sodium, mercury and sodium amalgams, lithium, and a mixture thereof; and preferably potassium.

[0037] The use of an amalgam makes it easier to weigh the quantity of reducing agent to be used in step i).

[0038] The organic solvent can be a conventional organic solvent, an ionic liquid, or a mixture.

[0039] An ionic liquid is well known to those skilled in the art and can be considered as a molten salt at room temperature (eg 18-25°C). The ionic liquid has an organic cationic part and acts as a solvent in the present invention, in the same way as a conventional organic solvent.

[0040] In the invention, conventional organic solvent means an organic solvent that is free of salt or is not in the form of a salt.

[0041] The organic solvent of step i) is preferably chosen from aprotic organic solvents.

[0042] According to one embodiment of the invention, the organic solvent of step i) is chosen from apolar aprotic organic solvents (as conventional organic solvents), ionic liquids, and one of their mixtures.

[0043] According to a first variant of this embodiment, the organic solvent of step i) is chosen from apolar aprotic organic solvents.

[0044] According to a second variant of this embodiment, the organic solvent of step i) is chosen from ionic liquids.

[0045] The apolar aprotic organic solvent of step i) is preferably chosen from THF (tetrahydrofuran) and methyl-THF.

[0046] The ionic liquid of step i) is preferably chosen from ammonium salts, imidazolium salts, phosphonium salts, pyrrolidinium salts, and piperidinium salts, and particularly preferably from alkylammonium salts, alkylimidazolium salts, alkylphosphonium salts, alkylpyrrolidinium salts, and alkylpiperidinium salts.

[0047] The ionic liquid of step i) preferably comprises an anionic part of the bis(trifluoromethanesulfonyl)imidate type.

[0048] Examples of ionic liquids include triethylbutylammonium bis(trifluoromethanesulfonyl)imidate, 1-butyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imidate, 1-ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imidate, trimethylbutylammonium bis(trifluoromethanesulfonyl)imidate, 1-butyl-1-methylpyrrolidinium bis(trifluoromethanesulfonyl)imidate, N-propyl-N-methylpyrrolidinium bis(trifluoromethanesulfonyl)imidate, or 1-butyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imidate.

[0049] The ionic liquid is preferably immiscible in water. This makes subsequent purifications easier.

[0050] During step i), the composition comprising the compound of formula (I), the reducing agent, and the organic solvent, is brought into contact with dinitrogen (N 2 ).

[0051] Step i) is carried out in a dry or anhydrous environment. In other words, step i) is preferably carried out in a glove box or in a suitable device to avoid contact with air and / or humidity.

[0052] Indeed, contact with humidity and / or air leads to the formation of secondary products such as H 2 , and / or R 1< R 2< MOMR 1< R 2< .

[0053] Step i) may last from 1 hour to approximately 20 hours, and preferably from 2 hours to approximately 12 hours.

[0054] Step i) is preferably carried out at a temperature ranging from -80°C to approximately 60°C, and particularly preferably from approximately 0°C to 30°C.

[0055] Step i) is preferably carried out with stirring, for example using a mechanical or magnetic stirrer. Stirring helps promote contact of the composition with the nitrogen, and thus promotes the reaction.

[0056] In order to allow the reaction between dinitrogen and compound (I), the reaction is preferably carried out under a dinitrogen atmosphere, in particular dry dinitrogen.

[0057] Step i) may be carried out at a pressure ranging from about 0.1 bar to 200 bar, and preferably from 1 bar to 100 bar. A pressure of at least 20 bar, and preferably at least 40 bar, is advantageous for improving the yield of ammoniacal nitrogen. A pressure of 1 bar is advantageous from an industrial point of view.

[0058] The reducing agent used in step i) may represent from 0.1% to 20% by weight, and preferably from 0.1% to 10% by weight, relative to the total weight of the composition.

[0059] The compound of formula (I) used in step i) may represent from 0.1% to 10% by weight, and preferably from 2% to 6% by weight, relative to the total weight of the composition.

[0060] During step i), the compound (I) reacts with dinitrogen to form one or more species based on nitrogen and the element M, in particular of the following formula (II): N(MR 1< R 2< ) 3-x H x , x being an integer ranging from 0 to 3.

[0061] The formation of one or more species based on nitrogen and the element M as defined above is explained in particular by the conduct of a radical chain reaction involving at least one or more radicals based on the element M which are sufficiently unstable to react with the nitrogen of the dinitrogen.

[0062] Surprisingly, compound (I) by its formula (I) and thus the definition of Y, M, R 1< and R 2< , has the ability to activate the triple bond of dinitrogen in a reducing medium and to minimize, or even avoid, the dimerization of the radical. Step ii)

[0063] In step ii), the nitrogen-based species and element M are hydrolyzed in an acidic medium to form ammoniacal nitrogen.

[0064] In the invention, ammoniacal nitrogen combines the two most reduced forms of nitrogen: ammonium (NH 4 +< ) and ammonia (NH 3 ). Ammoniacal nitrogen is therefore chosen from ammonium (NH 4 +< ), ammonia (NH 3 ), and their mixture. Generally, depending on the conditions of step ii), and in particular the quantity of acid, ammonium (excess acid) or ammonia (stoichiometric quantities relative to N(MR 1< R 2< ) 3-x H x ) will be obtained.

[0065] Step ii) of hydrolysis in an acid medium can be carried out by bringing a crude reaction product obtained in the previous step i) into contact with an acid solution or with a gaseous acid (in the form of a gas).

[0066] The acidic solution may comprise an aqueous solvent (e.g. water) and at least one acid such as hydrochloric acid, hydrobromide, sulfuric acid, or nitric acid, or an aprotic organic solvent and at least one acid such as hydrochloric acid, hydrobromide, sulfuric acid, or nitric acid.

[0067] The aprotic organic solvent may be selected from ethers such as diethyl ether or dioxane, and alkanes such as hexane or heptane.

[0068] The gaseous acid can be gaseous hydrochloric acid.

[0069] Step ii) advantageously leads to ammonium, in particular when the acid is used in excess relative to the compound of formula (I).

[0070] The aqueous solvent is preferably water.

[0071] The acidic solution can have a pH ranging from about 0 to 6.

[0072] Step ii) can last from about 1 min to 30 min, and preferably from about 2 min to 10 min. Step ii) is a very quick, almost instantaneous step.

[0073] Step ii) is preferably carried out at a temperature ranging from -20°C to approximately 40°C, and particularly preferably from 0°C to approximately 20°C.

[0074] Step ii) is preferably carried out with stirring.

[0075] Step ii) is preferably carried out at atmospheric pressure.

[0076] Step ii) leads to ammonia NH 3 and / or ammonium NH 4 +< . Other steps in the process

[0077] The process may further comprise, after step i) and before step ii), a step i') during which the organic solvent is removed.

[0078] This embodiment is particularly suitable when the organic solvent is a conventional organic solvent.

[0079] Step i') can be carried out by evaporation of the conventional organic solvent.

[0080] The process may comprise a purification step i") after step i) or step i') if it exists. This step i") makes it possible to remove at least part of the secondary products (e.g. salts) possibly formed during step i). In other words, step i") makes it possible to separate the nitrogen-based species and the element M formed in step i), from the salts.

[0081] Step i") may be carried out by extraction of a reaction mixture formed in step i) or step i') if it exists, in particular using an apolar organic solvent. The species based on nitrogen and the element M formed in step i) are soluble in said apolar organic solvent and may be separated from the salts by filtration.

[0082] The apolar organic solvent can be chosen from alkanes such as hexane, pentane, or heptane.

[0083] The preferred nonpolar organic solvent is pentane.

[0084] When the organic solvent of step i) is a conventional organic solvent, the purification step i") may be carried out after step i) or step i'), in particular by extraction of a reaction mixture formed in step i) or step i') as explained above.

[0085] When the organic solvent of step i) is an ionic liquid, the purification step i") can be carried out after step i), in particular by extraction of a reaction mixture formed in step i) as explained above.

[0086] The process may further comprise, before step i), a step i0) of preparing the compound of formula (I).

[0087] The compound of formula (I) can be prepared according to a double hydroboration or hydroalumination protocol as described in the following articles: H.C. Brown, N. Ravindran, J. Am. Chem. Soc. 1976, 98, 1798-1806 And HC Brown, N. Ravindran, J. Am. Chem. Soc. 1976, 98, 1785-1798; or by reacting two equivalents of alkene with one equivalent of a monohaloborane (e.g., having the formula YBH 2 in which Y is as defined in the invention) in THF or diethyl ether, at room temperature.

[0088] Generally, one equivalent of the compound MH 2 Y reacts with two equivalents of an alkene R'CH=CH 2 to form the compound (R'CH 2 CH 2 ) 2 MY.

[0089] The process of the invention preferably does not use gaseous species other than nitrogen (N 2 ) as starting reagent.

[0090] The process may further comprise a step iii) of recycling the compound (I). In this embodiment, step ii) is preferably carried out by bringing the reaction crude obtained in step i), i') or i") into contact under an inert atmosphere with an acid solution comprising an aprotic organic solvent and at least one acid, or with a gaseous acid, said acid solution and said gaseous acid being as defined above.

[0091] Step iii) can then be carried out after step ii) as follows: when the organic solvent is a conventional organic solvent: for example by removing the solvents of steps i), i"), and ii) if they exist, preferably by evaporation, and using an apolar organic solvent to precipitate NH 4 +< and separate / recover compound (I); or when the organic solvent is an ionic liquid: for example by removing the solvents of steps i") and ii) if they exist, and using a distillation system to recover NH 3 and separate / recover compound (I).

[0092] The apolar organic solvent may be as defined previously.

[0093] The second subject of the invention is the use of a compound of formula (I) as defined in the invention, for the reduction of dinitrogen. Examples Example 1: Process for producing ammoniacal nitrogen from dinitrogen using dicyclohexylchloroborane as a compound of formula (i)

[0094] 120 mg of a dicyclohexylchloroborane solution (1M in hexane) marketed under the reference 411124 by the company Sigma-Aldrich was added to 4 ml of anhydrous tetrahydrofuran, followed by 15 mg of potassium. The resulting composition was placed under an atmosphere of pure, dry dinitrogen and stirred for 12 hours. At the end of the reaction, the color of the mixture was brown. An excess of HCl (2 M) in Et 2 O was added under an inert atmosphere allowing the quantitative conversion of H x -N(BCy 2 ) 3-x to NH 4 +< and Cy 2 BCl. The solvents and volatile compounds were removed by evaporation, leaving a solid residue. This solid was extracted with hexane, allowing the separation of Cy 2 BCl from NH 4 +< .

[0095] NH 4 +< is obtained as a white solid. The yield relative to the initially introduced Cy 2 BCl is 38%. Example 2: Process for the production of ammoniacal nitrogen from dinitrogen using (+)-B-Chlorodiisopinocampheylborane as a compound of formula (I)

[0096] 48 mg of (+)-B-Chlorodiisopinocampheylborane (Ipc 2 BCl) marketed under the reference 317012 by the company Sigma-Aldrich was added to 4 mL of anhydrous tetrahydrofuran, followed by 15 mg of potassium. The resulting composition was placed under an atmosphere of pure, dry dinitrogen and stirred for 12 hours. At the end of the reaction, the color of the mixture was brown. An excess of HCl (2 M) in Et 2 O was added under an inert atmosphere allowing the quantitative conversion of H x -N(BIpc 2 ) 3-x to NH 4 +< and Cy 2 BCl. The solvents and volatile compounds were removed by evaporation, leaving a solid residue. This solid was extracted with hexane, allowing the separation of Ipc 2 BCl from NH 4 +< .

[0097] NH 4 +< is obtained in the form of a white solid. The yield compared to Ipc 2 BCl initially introduced is 15%. Example 3: control method (not part of the invention)

[0098] 120 mg of a dicyclohexylchloroborane solution (1M in hexane) marketed under the reference 411124 by the company Sigma-Aldrich was added to 4 mL of anhydrous tetrahydrofuran, followed by 15 mg of potassium. The resulting composition was placed under a pure, dry argon atmosphere and stirred for 12 hours. An excess of HCl (2 M) in Et 2 O was added under an inert atmosphere. No formation of NH 4 +< was observed. Example 4: control method (not part of the invention)

[0099] A suspension of 15 mg of potassium in 4 mL of anhydrous tetrahydrofuran was stirred under a pure, dry nitrogen atmosphere for 12 hours. An excess of HCl (2 mol / L) in Et 2 O was added under an inert atmosphere. No formation of NH 4 +< was observed. Example 5: Process for the production of ammoniacal nitrogen from dinitrogen using bis(bicyclo[2.2.1]-2-heptyl)chloroborane as a compound of formula (I)

[0100] 38 mg of a solution of Bis(bicyclo[2.2.1]-2-heptyl)chloroborane marketed under the reference 771880 by the company Sigma-Aldrich was added to 4 ml of anhydrous tetrahydrofuran, followed by 15 mg of potassium. The resulting composition was placed under an atmosphere of pure, dry dinitrogen and stirred for 12 hours. At the end of the reaction, the color of the mixture was brown. An excess of HCl (2 M) in Et 2 O was added under an inert atmosphere allowing the quantitative conversion of H x -N(BBCH 2 ) 3-x to NH 4 +< and BCH 2 BCl. The solvents and volatile compounds were removed by evaporation, leaving a solid residue. This solid was extracted with hexane, allowing the separation of BCH 2 BCl from NH 4 +< .

[0101] NH 4 +< is obtained as a white solid. The yield relative to the initially introduced Bis(bicyclo[2.2.1]-2-heptyl)chloroborane is 43%. Example 6: Process for the production of ammoniacal nitrogen from dinitrogen using dicyclohexylchloroborane as a compound of formula (I) at different pressures

[0102] In an autoclave, 120 mg of a dicyclohexylchloroborane solution (1 M in hexane) marketed under the reference 411124 by the company Sigma-Aldrich was added to 4 ml of anhydrous tetrahydrofuran, followed by 15 mg of potassium. The autoclave was then sealed. The resulting composition was pressurized (20 bar: Example 6-1, 40 bar: Example 6-2 and 80 bar: Example 6-3) with pure, dry dinitrogen and stirred for 12 hours. At the end of the reaction, the color of the mixture was brown. An excess of HCl (2 M) in Et 2 O was added under an inert atmosphere allowing the quantitative conversion of Hx-N(BCy 2 ) 3-x to NH 4 +< and Cy 2 BCl. The solvents and volatile compounds were removed by evaporation, leaving a solid residue. This solid is extracted with hexane, allowing the separation of Cy 2 BCl from NH 4 +< .

[0103] NH 4 +< is obtained in the form of a white solid. The yield relative to Cy 2 BCl initially introduced is: 60% for a pressure of 20 bars (example 6-1) 76% for a pressure of 40 bars (example 6-2) 94% for a pressure of 80 bars (example 6-3).

Claims

1. A process for producing ammoniacal nitrogen, the ammoniacal nitrogen being selected from ammonium (NH4+), ammonia (NH3), and a mixture thereof, characterised in that it comprises at least the following steps: i) a step of bringing a composition comprising a compound responding to a following formula (I): R1R2MY (I), a reducing agent, and an organic solvent, into contact with dinitrogen (N2), said formula (I) being such that: - M is an element of group 13 of the periodic table, - R1 and R2, identical or different, are selected from an alkyl group, an aryl group, an aryl-alkyl group, an -OR group and an -SR group, R being an alkyl group, an aryl group or an aryl-alkyl group, and - Y is a group selected from a halogen -X, an -OR3 group, an -SR3 group, a triflate group, a mesylate group, and a triflimidate group, R3 being an alkyl group, an aryl group, or an aryl-alkyl group, and ii) a hydrolysis step in acidic medium.

2. The process according to claim 1, characterised in that the element M is selected from boron, aluminium and a mixture thereof.

3. The process according to claim 1 or 2, characterised in that the two groups R1 and R2 are alkyl groups.

4. The process according to any of the preceding claims, characterised in that Y is a halogen X.

5. The process according to any of the preceding claims, characterised in that the reducing agent is selected from potassium, sodium, mercury- and sodium-based amalgams, lithium, and a mixture thereof.

6. The process according to any of the preceding claims, characterised in that step i) is carried out at a temperature ranging from -80°C to 60°C.

7. The process according to any of the preceding claims, characterised in that the reducing agent used in step i) represents from 0.1% to 20% by weight, relative to the total weight of the composition.

8. The process according to any of the preceding claims, characterised in that the compound of formula (I) used in step i) represents from 0.1% to 10% by weight relative to the total weight of the composition.

9. The process according to any of the preceding claims, characterised in that step ii) of hydrolysis in acidic medium is implemented by bringing a reaction crude obtained in preceding step i) into contact with an acidic solution or with a gaseous acid.

10. The process according to claim 9, characterised in that the acidic solution has a pH ranging from 0 to 6.

11. The process according to any of the preceding claims, characterised in that the organic solvent of step i) is selected from apolar aprotic organic solvents.

12. The process according to any of the preceding claims, characterised in that it further comprises, after step i) and before step ii), a step i') of evaporating the organic solvent.

13. The process according to any of claims 1 to 10, characterised in that the organic solvent of step i) is selected from ionic liquids.

14. The process according to any of the preceding claims, characterised in that it comprises a purification step i") after step i) or step i') if present, by extracting a reaction mixture formed in step i) or step i') if present, using an apolar organic solvent.

15. Use of a compound of formula (I) as defined in any of claims 1 to 4, for dinitrogen reduction.