A process for preparing at least one aromatic compound suitable for storing and / or transporting dihydrogen

Abstract

The present invention relates to a process for preparing at least one LOHC aromatic compound and / or one of its geometric isomers, preferably at least of benzyltoluene (BT) and / or at least of dibenzyltoluene (DBT), suitable for storing and / or transporting dihydrogen.

Description

Title of the invention: Process for preparing at least one aromatic compound suitable for storing and / or transporting dihydrogen

[0001] The present invention relates to a process for preparing at least one aromatic compound of formula (I) and / or at least one of its geometric isomers, preferably at least of benzyltoluene (BT) and / or at least of dibenzyltoluene (DBT), preferably of benzyltoluene (BT), preferably suitable for storing and transporting dihydrogen.

[0002] Hydrogen currently represents an attractive alternative to fossil fuel, natural, or electrical energy sources. However, the storage and transport of this energy source remains a major challenge for its rapid and accessible development.

[0003] Several approaches have been studied to store and transport this highly volatile and highly explosive gas more easily, and among these we can mention high pressure storage, cryogenic storage and the storage of gaseous hydrogen adsorbed or absorbed by a solid material.

[0004] Such approaches have the major disadvantage of involving significant operational and / or energy costs. Indeed, storing hydrogen in gaseous form under high pressure requires tanks capable of withstanding high pressures, ranging from 350 to 750 bar, or even higher, which necessitates the use of expensive composite materials. Cryogenic storage of hydrogen in liquid form, on the other hand, requires cooling the hydrogen to a temperature below its boiling point of -253°C, which represents a considerable energy cost as well as the implementation of highly efficient cooling systems.Finally, the disadvantages of storing gaseous hydrogen in a solid material lie mainly in absorption or adsorption performance that is still too often low, in limited rates of hydrogen release under optimal pressures and temperatures, and in the instability of solid storage materials.

[0005] In order to overcome such drawbacks, hydrogen storage in a liquid medium has been preferred. In particular, technology based on liquid organic hydrogen carriers (LOHC) is a promising technology and particularly attractive for long-distance transport, at costs entirely compatible with large-scale development.

[0006] The principle of this LOHC technology consists of fixing hydrogen onto a support molecule, which is preferably and most often liquid at room temperature, in a catalytic hydrogenation step, and then releasing the fixed hydrogen, preferably near the point of consumption, in a catalytic dehydrogenation step.

[0007] Among the LOHC molecules studied today, aromatic liquids with two or three aromatic rings, such as for example benzyltoluene (BT) and / or dibenzyltoluene (DBT), represent molecules particularly well suited for the long-term storage and long-distance transport of large quantities of hydrogen.

[0008] Indeed, LOHC organic liquids of the benzyltoluene (BT) and / or dibenzyltoluene (DBT) type have an advantageous physicochemical profile, notably a high flash point, a high boiling point, and thermal stability. Thus, such LOHC organic liquids can be easily handled, whether in their saturated or unsaturated form, over a wide temperature range, from -30 to 300°C, and are compatible with oil and petrochemical infrastructure.

[0009] The processes for the synthesis of benzyltoluene (BT) and / or dibenzyltoluene (DBT) are generally carried out in the presence of catalysts, for example zeolites or ferric chloride (FeCl3), and most often include an alkylation reaction between benzyl chloride and toluene, alternatively between benzyl alcohol and toluene, or a reaction between diphenylmethane and toluene.

[0010] The operating conditions, for example the nature of the catalysts used, the temperature and / or the number of moles of toluene, make it possible to influence the kinetics of these synthesis processes and to favor the formation of benzyltoluene (BT), dibenzyltoluene (DBT) or mixtures of benzyltoluene (BT) and dibenzyltoluene (DBT).

[0011] Similarly, the operating conditions can also influence the quantities of ortho-, para-, or meta- isomers of benzyltoluene (BT) and dibenzyltoluene (DBT) formed during these synthetic processes. In all cases, such synthetic processes lead to mixtures of benzyltoluene (BT) and / or dibenzyltoluene (DBT) isomers.

[0012] Furthermore, the processes for preparing benzyltoluene (BT) and / or dibenzyltoluene (DBT) usually result in a large volume consumption of chlorine (Cl2) regardless of the starting reagent used (benzyl chloride, benzyl alcohol or diphenylmethane).

[0013] Indeed, benzyl chloride is generally produced industrially by radical activation between toluene and chlorine (Cl2), either through the addition of Free radicals (AIBN, benzoyl peroxide, etc.) are neutralized either by ultraviolet rays, leading to the formation of hydrochloric acid (HCl). Benzyl alcohol is obtained by hydrolysis of benzyl chloride in the presence of basic saponifying agents to neutralize the gaseous hydrochloric acid (HCl) formed, while diphenylmethane is obtained by the reaction of benzyl chloride with benzene.

[0014] Thus, whatever the synthetic route taken, the processes for preparing benzyltoluene (BT) and / or dibenzyltoluene (DBT) involve using benzyl chloride, as a synthetic intermediate or starting reagent, which is obtained from chlorine (Cl2).

[0015] World production of benzyltoluene (BT) / dibenzyltoluene (DBT) is currently estimated at around 50 kilotons per year. However, by way of illustration, for the production of one tonne of benzyltoluene (BT) / dibenzyltoluene (DBT), quantities of chlorine (Cl2) ranging from 0.4 to 0.8 tonnes are required to implement the synthesis processes described above.

[0016] In addition, the processes for preparing benzyltoluene (BT) and / or dibenzyltoluene (DBT) lead to the production of significant quantities of hydrochloric acid in gaseous form (HCl).

[0017] Indeed, as previously stated, the reaction producing one mole of benzyl chloride leads to the formation of one mole of gaseous hydrochloric acid (HCl). Similarly, the reaction of benzene chloride with benzene leads to the production of diphenylmethane and one mole of gaseous hydrochloric acid (HCl).

[0018] On the other hand, the processes for preparing benzyltoluene (BT) and / or dibenzyltoluene (DBT) are also responsible for the production of significant quantities of sodium hydroxide (NaOH).

[0019] Indeed, chlorine (Cl2), used to industrially produce benzyl chloride, is commonly obtained by direct current electrolysis of aqueous sodium chloride (NaCl) solutions. Such electrolysis results in the co-production of sodium hydroxide, hydrogen, and possibly sodium hypochlorite (bleach) per tonne of chlorine produced. Thus, by way of illustration, for the production of one tonne of chlorine, depending on the electrolysis process used, particularly the amount of electricity, quantities of sodium hydroxide ranging from 1.05 to 1.12 tonnes and between 300 and 350 Nm3 of hydrogen are generally produced.

[0020] In view of the above, current processes for preparing benzyltoluene (BT) and / or dibenzyltoluene (DBT) require a considerable volume of chlorine (Cl2) and generate a significant production of acid hydrochloric acid in gaseous form (HCl), which needs to be treated, and have a significant impact on the production of sodium hydroxide (NaOH).

[0021] In addition, such volume requirements for chlorine (Cl2) as well as the production of hydrochloric acid in gaseous form (HCl) and soda (NaOH), caused by the synthesis processes as described above, are expected to increase in view of the growing demand for hydrogen which will require in the coming decades the production of increasingly large volumes of benzyltoluene (BT) and / or dibenzyltoluene (DBT), estimated at between 100 and 1000 kilotons per year.

[0022] Finally, such drawbacks are also encountered during the preparation of other LOHC molecules having at least one aromatic ring in their structure, for example phenylxylylethane (PXE), phenylethylenephenylethane (PEPE) or xylylxylene, and obtained from a synthesis process comprising at least one halogenation chemical reaction between at least one compound comprising at least one aromatic ring substituted by at least one alkyl group and chlorine (Cl2).

[0023] Indeed, in the same way as for the preparation of benzyltoluene (BT) and / or dibenzyltoluene (DBT), such synthesis processes require a significant input of chlorine (Cl2), generally from an electrolysis of aqueous solutions of sodium chloride (NaCl), and produce significant quantities of sodium hydroxide and hydrochloric acid.

[0024] Thus, one of the objectives of the present invention is to implement a process for preparing at least one aromatic compound suitable for storing and transporting hydrogen, capable of overcoming the aforementioned drawbacks, i.e., of significantly reducing the consumption of chlorine (Cl2), resulting from the electrolysis of aqueous solutions of sodium chloride (NaCl), and of reducing the volumes of sodium hydroxide and hydrochloric acid generated during such a synthesis process.

[0025] In particular, one of the aims of the present invention is to propose a process for the preparation of benzyltoluene (BT) and / or dibenzyltoluene (DBT) which does not have the disadvantages mentioned above, i.e. in which the volume consumption of chlorine (Cl2), from an electrolysis of aqueous solutions of sodium chloride (NaCl), and the volume production of sodium hydroxide (NaOH) and hydrochloric acid (HCl) are significantly reduced, in particular compared to the processes classically implemented in the prior art.

[0026] The present invention therefore relates in particular to a method for preparing at least one compound of formula (I) and / or at least one of its geometric isomers:

[0027] [Chem.l]

[0028] Formula (I) in which ni is an integer with the value 0 or 1 and R represents a methyl group,

[0029] said process comprising: i. at least one chlorination step (a) of toluene leading at least to the formation of benzyl chloride and hydrochloric acid (HCl), ii. at least one coupling reaction step (bl) between benzyl chloride, obtained at least in step (a), and benzene, leading at least to the formation of diphenylmethane and hydrochloric acid (HCl), iii. at least one recovery step (c) of the hydrochloric acid (HCl) formed at the end of at least said step (a) and / or (bl), iv. at least one conversion step (d) of hydrochloric acid (HCl), recovered at the end of at least said step (c), into chlorine (Cl2), v. at least one transfer step (e) of chlorine (Cl2), from at least said conversion step (d), to said chlorination step (a), vi. at least one reaction step (b2) between diphenylmethane, obtained at the end of said reaction step by coupling (bl), and toluene, leading to the formation of at least one compound of formula (I) and / or at least one of its geometric isomers, vii. optionally at least one step of adding (e') chlorine (Cl2), which may be obtained from at least one process of electrolysis of at least one aqueous solution of sodium chloride (NaCl) or from any other synthesis process, to said step (a).

[0030] The process according to the invention thus makes it possible to efficiently prepare at least one compound of formula (I) and / or at least one of its geometric isomers, suitable for storing and transporting hydrogen, while considerably reducing the volumes of chlorine (Cl2) from at least one process of electrolysis of aqueous solutions of sodium chloride (NaCl) as well as the quantities of sodium hydroxide (NaOH) and hydrochloric acid (HCl) generated.

[0031] Advantageously, the process according to the invention has the advantage of regenerating significant volumes of chlorine (Cl2) during its implementation, which leads to a significant reduction in the consumption of volumes of chlorine (Cl2), from at least one process of electrolysis of aqueous solutions of sodium chloride (NaCl) necessary for the preparation of the compound of formula (I) and / or one of its geometric isomers, all this without degrading the yield and / or the degree of purity.

[0032] In particular, the process according to the invention makes it possible to regenerate large volumes of chlorine (Cl2) from the conversion of hydrochloric acid (HCl) produced in said at least step (a) and / or (b).

[0033] In other words, the process according to the invention makes it possible to reduce the input of volumes of "fresh" chlorine (Cl2), i.e. from the implementation of one or more processes of electrolysis of aqueous solutions of sodium chloride (NaCl), compared to processes classically described in the prior art.

[0034] In other words, the process according to the invention makes it possible to increase the amount of chlorine (Cl2) regenerated compared to the amount of chlorine (Cl2) from at least one process of electrolysis of aqueous solutions of sodium chloride (NaCl).

[0035] Advantageously, the quantity of chlorine (Cl2) regenerated during the implementation of the process according to the invention, compared to the quantity of chlorine (Cl2) required for the production of the compound of formula (I) and / or one of its geometric isomers, is at least 80%, preferably at least 90% and more preferably at least 95%.

[0036] The process according to the invention thus makes it possible to preserve natural resources, such as sodium chloride salts, and to maintain economic balances by limiting the production of hydrochloric acid and soda, in particular sodium hypochlorite (bleach).

[0037] The quantity of chlorine (Cl2) transferred during step (e) to the chlorination step (a) can advantageously be supplemented with new quantities of chlorine (Cl2) from at least one process of electrolysis of aqueous solutions of sodium chloride (NaCl) as well as from any other type of synthesis process.

[0038] Thus the quantity of chlorine (Cl2) regenerated can be supplemented with "fresh" chlorine to advantageously compensate for losses related to secondary reactions that may take place during the implementation of at least said step (a).

[0039] The process according to the invention thus makes it possible to prepare large quantities of at least one compound of formula (I) with a low demand for "fresh" chlorine, i.e. not regenerated during the process, and while preserving large volumes of salts, in particular aqueous solutions of sodium chloride.

[0040] Furthermore, the process according to the invention leads to a reduction in the quantities produced of sodium hydroxide (NaOH) and hydrochloric acid (HCl).

[0041] Advantageously, the process according to the invention leads to a reduction in the quantities of hydrochloric acid produced at least in one of the steps (a) and (bl).

[0042] Advantageously, the process according to the invention ensures better valorization of the by-products from one of the steps (a), (bl), (c), (d), (e) and / or (b2).

[0043] Indeed, the by-product(s) from at least one of the steps (a), (bl), (c), (d), (e) and / or (b2) is or are efficiently transferred to at least one of the steps of the process.

[0044] The process according to the invention makes it possible to prepare at least one compound of formula (I), and / or at least one of its geometric isomers, capable of meeting the requirements for the storage, transport and release of hydrogen, under optimal industrial and economic conditions.

[0045] The compound of formula (I) and / or at least one of its geometric isomers can advantageously be used as LOHC compound(s).

[0046] In the LOHC application, the hydrogen transport formulations whose use is the subject of the present invention are particularly well suited because of their stability which allows reuse in a large number of hydrogenation / dehydrogenation cycles for the transport and handling of hydrogen from the steam cracking of petroleum products, of waste hydrogen from chemical reactions such as salt electrolysis or of hydrogen from water electrolysis.

[0047] The compound of formula (I) and / or at least one of its geometric isomers can also be used as a heat transfer fluid, dielectric fluid, solvent for purifying gaseous effluents containing aromatic impurities, plasticizers and process solvents.

[0048] The compound(s) of formula (I) is or are obtained in particular from products of renewable origin.

[0049] The carbon in a renewable product comes from plant photosynthesis and therefore from atmospheric CO2. The term "biocarbon" indicates that the carbon is of renewable origin and comes from a biomaterial, as described below. Biocarbon content and biomaterial content are expressions denoting the same value.

[0050] A renewable material, also called a biomaterial, is an organic material in which the carbon comes from CO2 recently fixed (on a human timescale) by photosynthesis from the atmosphere. On land, this CO2 is captured or fixed by plants. In the sea, CO2 is captured or fixed by bacteria or plankton carrying out photosynthesis.

[0051] A biomaterial (100% naturally sourced carbon) has a 14C / 12C isotopic ratio greater than 10⁻¹², typically on the order of 1.2 x 10⁻¹², while a Fossil material has a zero ratio. Indeed, the 14C isotope is formed in the atmosphere and then incorporated through photosynthesis, on a timescale of a few decades at most. The half-life of 14C is 5730 years. Therefore, materials resulting from photosynthesis, namely plants in general, necessarily have a maximum 14C isotope content.

[0052] The determination of the biomaterial or biocarbon content is carried out in accordance with ASTM D 6866 (ASTM D 6866-06) and ASTM D 7026 (ASTM D 7026-04). ASTM D 6866 is concerned with "Determining the Biobased Content of Natural Range Materials Using Radiocarbon and Isotope Ratio Mass Spectrometry Analysis," while ASTM D 7026 is concerned with "Sampling and Reporting of Results for Determination of Biobased Content of Materials via Carbon Isotope Analysis." The first paragraph of the latter refers to the former.

[0053] The first standard describes a test for measuring the 14C / 12C ratio of a sample and comparing it with the 14C / 12C ratio of a reference sample of 100% renewable origin, to give a relative percentage of carbon from renewable sources in the sample. The standard is based on the same concepts as 14C dating, but without applying the dating equations.

[0054] The ratio thus calculated is designated as the "pMC" (percent Modern Carbon). If the material to be analyzed is a mixture of biomaterial and fossil material (without radioactive isotopes), then the pMC value obtained is directly correlated to the quantity of biomaterial present in the sample. The reference value used for 14C dating is a value from the 1950s. This year was chosen because of the existence of atmospheric nuclear tests that introduced large quantities of isotopes into the atmosphere after that date. The 1950 reference corresponds to a pMC value of 100. Taking into account thermonuclear tests, the current value to be used is approximately 107.5 (which corresponds to a correction factor of 0.93). The radioactive carbon signature of a present-day plant is therefore 107.5. A signature of 54 pMC and 99 pMC therefore correspond to a quantity of biomaterial in the sample of 50% and 93%, respectively.

[0055] Other features and advantages of the invention will become more apparent from the description, figure and examples that follow.

[0056] In what follows, and unless otherwise indicated, the bounds of a domain of values ​​are included in that domain, in particular in the expressions "between... and..." and "ranging from... to...".

[0057] The expression "at least one" is equivalent to the expression "one or more" and can be substituted.

[0058] In the remainder of the present invention, the term chlorine has the same meaning as the term dichlorine (Cl2).

[0059] In the remainder of the present invention, the term hydrogen has the same meaning as the term dihydrogen (H2). Compound corresponding to formula (I)

[0060] As indicated above, the process according to the invention is a process for preparing at least one compound corresponding to formula (I) and / or at least one of its isomers:

[0061] [Chem.l]

[0062] Formula (I) wherein:

[0063] ni is an integer equal to 0 or 1, and

[0064] R represents a methyl group.

[0065] Preferably, ni is an integer with the value 0 or 1, in particular with the value zero.

[0066] The process according to the invention can lead to one or more geometric isomers in ortho-, meta-, or para- positions in all proportions.

[0067] According to one embodiment, the process according to the invention is a process for preparing benzyltoluene (compound of formula (I) in which ni = 0).

[0068] According to one embodiment, the process according to the invention is a process for preparing dibenzyltoluene (compound of formula (I) in which ni = 1).

[0069] According to one embodiment, the process according to the invention is a process for preparing benzyltoluene (compound of formula (I) in which nl=0) and dibenzyltoluene (compound of formula (I) in which nl=l).

[0070] Advantageously, the process according to the invention is a process for preparing benzyltoluene (compound of formula (I) in which ni = 0).

[0071] The process according to the invention can produce 80 to 100% by weight, more preferably 90 to 100% by weight, even more preferably 95 to 100% by weight, of benzyltoluene (BT).

[0072] Advantageously, the benzyltoluene (BT) obtained according to the process of the present The invention exhibits a high degree of purity and meets the IEC 60867 specification and / or the DIN 91 437 specification. Step (a)

[0073] As indicated above, the process according to the invention includes at least one chlorination step (a) of toluene leading at least to the formation of hydrochloric acid (HCl) and benzyl chloride.

[0074] Preferably, the process according to the invention includes at least one chlorination step (a), as defined below, between toluene and chlorine (Cl2).

[0075] Said at least chlorination step (a) may be a radical activation reaction, preferably carried out in the presence of one or more free radicals, preferably selected from the group consisting of azobisisobutyronitrile (AIBN), benzyl peroxide or hexaphenylethane, or a radical activation reaction under the effect of ultraviolet, preferably in a wavelength range of 300 to 500 nm.

[0076] Said at least chlorination step (a) is preferably a radical activation reaction under the effect of ultraviolet rays, in particular in a wavelength range of 200 to 600 nm, better from 300 to 500 nm.

[0077] Said at least chlorination step (a) by radical activation under the effect of ultraviolet rays can be carried out using one or more mercury lamps or LEDs.

[0078] According to a preferred embodiment, said at least chlorination step (a) is a radical activation reaction under the effect of ultraviolet, in a wavelength range of 200 to 600 nm, preferably from 300 to 500 nm, and takes place at a pressure of -1.5 to 2 bar, preferably from 0 to 1 bar, at a temperature of -10 to 110°C, preferably from 0 to 100°C, even better from 20 to 80°C.

[0079] Said at least chlorination step (a) is preferably carried out with toluene in a molar quantity in excess with respect to chlorine (Cl2).

[0080] Said at least chlorination step (a) leads at least to the formation of hydrochloric acid (HCl), preferably in gaseous form, and at least benzyl chloride.

[0081] Benzyl chloride, obtained at the end of the chlorination step(s) (a), may be in solution with toluene.

[0082] According to a preferred embodiment, the process according to the invention comprises, successively, at least said chlorination step (a) and at least one purification step (al) of benzyl chloride.

[0083] The purification step(s) (al) may be chosen from the group consisting of at least one distillation step (a' 1) of benzyl chloride, at least one dechlorination step (a”l) of the reaction medium obtained from at least step (a), and / or a mixture of said steps.

[0084] Preferably, the purification step(s) (al) is or are one or more distillation steps (a' 1) of benzyl chloride.

[0085] In other words, preferably, the process according to the invention comprises, successively to at least said chlorination step (a), at least one distillation step (al) of benzyl chloride.

[0086] The purification step(s) (al) allows(s) to improve the degree of purity of the benzyl chloride obtained at least in step (a).

[0087] Advantageously, the distillation step(s) (a' 1) allows(s) to lead to at least one benzyl chloride having a degree of purity of at least 95%, preferably greater than or equal to 99%, more preferably greater than or equal to 99.5%.

[0088] More preferably, during the chlorination step(s), as defined above, toluene is present in an excess molar quantity relative to dichlorine (Cl2). Step (bl)

[0089] As indicated above, the process according to the invention includes at least one coupling reaction step (bl) between benzyl chloride, obtained during step(s) (a), and benzene to lead at least to the formation of hydrochloric acid (HCl) and diphenylmethane.

[0090] Preferably, the process according to the invention comprises a coupling reaction step (bl), as defined below, between at least the benzyl chloride, obtained during step(s) (a), and benzene.

[0091] Said at least one coupling reaction step (bl) is preferably carried out with benzene in a molar quantity in excess with respect to the chloride of the aromatic compound of formula (I) obtained during the and / or step(s) (a).

[0092] Said at least one coupling reaction step (bl) thus leads at least to the formation of hydrochloric acid (HCl), preferably in gaseous form, and diphenylmethane.

[0093] The diphenylmethane thus obtained can be in solution in benzene.

[0094] According to a preferred embodiment, the process according to the invention comprises, successively, at least said coupling reaction step (bl) and at least one purification step (b' 1) of diphenylmethane.

[0095] The purification step(s) (b' 1) may be one or more distillation steps, one or more dechlorination steps of the reaction medium from at least said step (b' 1).

[0096] Advantageously, diphenylmethane has a high degree of purity, preferably having less than 50 ppm of residual chlorine (Cl2) and an acid number of less than 0.1 mg KOH / g. Step (c)

[0097] As indicated above, the process according to the invention includes at least one recovery step (c) of the hydrochloric acid (HCl) formed at the end of step(s) (a) and / or step(s) (bl).

[0098] The recovery step(s) (c) may collect hydrochloric acid (HCl) directly or indirectly formed at the end of step(s) (a) and / or step(s) (bl).

[0099] By "directly formed at the end of step(s) (a) and / or step(s) (bl)", it is understood in the context of the present invention that the hydrochloric acid (HCl) is recovered in gaseous form at the end of step(s) (a) and / or step(s) (bl).

[0100] By "indirectly formed at the end of step(s) (a) and / or step(s) (bl)", it is understood in the context of the present invention that hydrochloric acid (HCl) in gaseous form, formed at the end of step(s) (a) and / or step(s) (bl), can be absorbed by water, in particular in a column with water, to form an aqueous solution of hydrochloric acid (HCl).

[0101] In other words, the recovery step(s) (c) allows the hydrochloric acid, from step(s) (a) and / or step(s) (bl), to be treated in both gaseous and aqueous form.

[0102] Thus said at least step (c) can be implemented to recover at least one aqueous solution of hydrochloric acid (HCl).

[0103] The recovery step(s) (c) may thus include a step of absorption of hydrochloric acid (HCl) in gaseous form, formed at the end of step(s) (a) and / or step(s) (bl), in water.

[0104] Preferably, the process according to the invention includes at least one recovery step (c) of the hydrochloric acid (HCl) formed at the end of step(s) (a) and step(s) (bl).

[0105] Preferably, the recovery step(s) (c) is or are implemented to recover hydrochloric acid (HCl) upstream of at least the chlorination step (a).

[0106] Preferably, step(s) (c) recover(s) hydrochloric acid (HCl) directly or indirectly formed: - following said at least chlorination step (a) of toluene leading at least to the formation of hydrochloric acid and benzyl chloride, and / or, preferably and - at the end of said at least coupling reaction step (bl) between benzyl chloride and benzene leading at least to the formation of hydrochloric acid and diphenylmethane. Step (d)

[0107] As indicated above, the process according to the invention includes at least one step of conversion (d) of hydrochloric acid (HCl), recovered at the end of step or steps (c), into chlorine (Cl2).

[0108] In other words, said at least step (d) is intended to convert hydrochloric acid (HCl), whether in gaseous or aqueous form, into chlorine (Cl2).

[0109] Said at least one conversion step (d) can in particular be carried out by electrolysis of hydrochloric acid (HCl) into chlorine (Cl2), by oxidation of hydrochloric acid (HCl) by nitric acid (HNO3) (Kel-Chlor process), or by catalytic oxidation of hydrochloric acid (HCl) (Deacon, Shell cor, MT chlorine process) or any other synthesis process.

[0110] Preferably, said at least conversion step (d) is carried out by electrolysis of hydrochloric acid (HCl).

[0111] In other words, said at least one conversion step (d) includes at least one electrolysis of hydrochloric acid (HCl), formed at the end of step (a) and / or step (bl), into chlorine (Cl2).

[0112] According to an advantageous embodiment, said at least conversion step (d) is an electrolysis of hydrochloric acid (HCl) leading to the formation of chlorine (Cl2) and hydrogen (H2).

[0113] In the case where said at least conversion step (d) is an electrolysis of hydrochloric acid (HCl), the hydrogen formed can be utilized, preferably either by being partially or totally stored in the compound(s) (I) and / or at least one of its geometric isomers, synthesized in said at least step (b2) (in the hydrogenated form of the aromatic compound(s) of formula (I) and / or one of its geometric isomers obtained at the end of at least said step (b2)), or as an energy source for producing heat or electricity according to methods known to those skilled in the art.

[0114] Said at least recovery step (c) and said at least transfer step (d) may be carried out sequentially or simultaneously, preferably sequentially.

[0115] Preferably, the method according to the invention comprises: - at least one conversion step (d) of hydrochloric acid (HCl) into chlorine (Cl2) and hydrogen (H2) implemented by electrolysis of the hydrochloric acid formed at the end of step(s) (a) and / or step(s) (bl), - at least one hydrogen utilization step (f), preferably at least one storage step for all or part of the hydrogen (H2) in the or compounds of formula (I) and / or one of its geometric isomers synthesized at least said step (b2).

[0116] Advantageously, when the conversion step (d) is carried out by electrolysis of hydrochloric acid (HCl), the water used can be recovered to absorb the hydrochloric acid (HCl) in gaseous form as a result of said at least step (a) and / or said at least step (bl).

[0117] Advantageously, the method according to the invention comprises: - at least one conversion step (d) of hydrochloric acid (HCl) into chlorine (Cl2) and hydrogen (H2) implemented by electrolysis of the hydrochloric acid formed at the end of step (a) of toluene chlorination, as defined above, and / or of the coupling reaction step (bl) between benzyl chloride and benzene, as defined above, - at least one hydrogen valorization step (f), preferably at least one storage step of all or part of the hydrogen (H2) in benzyltoluene (BT) and / or dibenzyltoluene (DBT) of formula (I), preferably benzyltoluene, obtained in said at least step (b2). Step (e)

[0118] As indicated above, the process according to the invention includes at least one transfer step (e) of chlorine (Cl2), from at least the conversion step (d), to at least said chlorination step (a).

[0119] Said at least transfer step (e) thus allows the chlorine (Cl2) to be recycled as a reagent of at least said chlorination step (a).

[0120] In other words, said at least transfer step (e) is a chlorine (Cl2) recirculation step to at least said chlorination step (a). In this way, the chlorine (Cl2), from at least the conversion step (d), is consumed by at least said chlorination step (a).

[0121] Said at least transfer step (e) can be carried out at a temperature ranging from 0°C to 50°C, preferably at a temperature in the vicinity of 27°C.

[0122] Said at least conversion step (d) and said at least transfer step (e) can be carried out sequentially or simultaneously, preferably sequentially. Step (b2)

[0123] As previously stated, the process according to the invention comprises at least one reaction step (b2) between diphenylmethane, obtained at the end of at least said coupling reaction step (bl), and toluene, to lead to the formation of at least one compound of formula (I) and / or one of its geometric isomers.

[0124] Said at least one coupling reaction step (b2) is preferably carried out with toluene in a molar amount in excess of the diphenylmethane obtained in at least said step (bl).

[0125] Said at least one coupling reaction step (b2) can be implemented by catalytic reaction, in particular in the presence of one or more catalysts chosen from the group consisting of zeolites, in particular aluminosilicates having a molar ratio SiO2 / Al2O3 greater than or equal to 20.

[0126] Said at least one coupling reaction step (b2) can in particular be carried out at a temperature ranging from 150 to 400°C, preferably from 170 to 400°C, in the presence of one or more catalysts chosen from the group consisting of zeolites, in particular aluminosilicates having a molar ratio SiO2 / Al2O3 greater than or equal to 20.

[0127] Preferably, the catalyst(s) is or are ZSM-5 type aluminosilicates.

[0128] Preferably, said at least one coupling reaction step (b2) is a coupling reaction of diphenylmethane, obtained at the end of step(s) (bl), and toluene, leading to the formation of at least benzyltoluene (BT) and / or dibenzyltoluene (DBT), preferably benzyltoluene (BT), of the following formula (I):

[0129] [Chem.l] R

[0130] Formula (I) wherein:

[0131] ni is an integer equal to 0 or 1,

[0132] R corresponding to a methyl group (CH3).

[0133] Preferably, in the coupling reaction step (b2), toluene is present in an excess molar amount relative to diphenylmethane.

[0134] Said at least reaction step (b2) can be implemented after at least step(s) (bl), (c), (d), (e).

[0135] Preferably, said at least reaction step (b2) is implemented after at least said step (e). Additional step(s)

[0136] As previously stated, the method according to the invention comprises possibly at least one step of adding chlorine (Cl2), which may be derived of at least one process of electrolysis of at least one aqueous solution of sodium chloride (NaCl) or of any other synthesis process, at least said step (a).

[0137] Preferably, the process according to the invention includes at least one step of adding (e') chlorine (Cl2), which may be obtained from at least one process of electrolysis of at least one aqueous solution of sodium chloride (NaCl) or from any other synthesis process, to at least said step (a).

[0138] Said at least addition step (e') is intended to add chlorine (Cl2) which is not from at least said conversion step (d), to the chlorination step (a).

[0139] In other words, said at least step (e') is intended to add "fresh" chlorine (Cl2), i.e. not from at least the conversion step (d), to be consumed as a reagent by at least said chlorination step (a).

[0140] Thus said at least step (e') makes it possible to complete the supply of chlorine (Cl2), resulting from said at least conversion step (d).

[0141] Said at least step (e') comprises at least the addition of chlorine (Cl2), which may be obtained from at least one electrolysis process of at least one aqueous solution of sodium chloride (NaCl), hydrochloric acid (HCl) obtained by at least one synthesis process of at least one isocyanate, in particular carried out by phosgenation of at least one amine, hydrochloric acid (HCl) obtained by at least one synthesis process of at least one carbonate ester carried out by phosgenation of at least one alcohol, or hydrochloric acid (HCl) obtained by at least one synthesis process of at least one methanesulfonic acid.

[0142] Preferably, said at least step (e') includes at least the addition of chlorine (Cl2) from at least one electrolysis process of at least one aqueous solution of sodium chloride (NaCl).

[0143] The process according to the invention may further include at least one recovery step (g1) of the toluene that did not react in step(s) (a) and / or step(s) (b2), and at least one transfer step (g2) of the toluene to at least said step (a) and / or (b2).

[0144] The purpose of said at least step (g1) is to recover the excess toluene, implemented during at least said step (a) and / or (b2), and the purpose of said at least step (g2) is to transfer said excess toluene to at least said step (a) and / or (b2).

[0145] Said at least steps (gl) and (g2) thus allow the unreacted toluene to be recycled to be consumed as a reactant by at least said step (a) and / or (b2).

[0146] In other words, preferably, the process according to the invention includes at least one recovery step (gl) of the excess toluene, resulting from at least said step (a) and / or (b2), and at least one transfer step (g2) of said excess to at least said step (a) and / or (b2).

[0147] The process according to the invention may also include at least one step of adding (g3) at least of the toluene, which is not implemented at least in at least said step (a) and / or (b2), in at least said step (a) and / or (b2).

[0148] In other words, step (g3) is intended to add at least "fresh" toluene ", i.e., which is not implemented at least in step (a) and / or (b2), to be consumed as a reactant by at least step (a) and / or (b2).

[0149] Preferably, the method according to the invention further comprises: - at least one recovery step (gl) of excess toluene implemented in the chlorination step (a) of toluene and / or of excess toluene implemented in the coupling reaction step (b2) between diphenylmethane and toluene, - at least one addition step (g2) of the toluene recovered by at least step (gl) to step(s) (a) and (b2) as defined above.

[0150] The process according to the invention may further include at least one recovery step (hl) of the benzene that did not react in step (bl) and, and at least one transfer step (h2) of the benzene to at least step (bl) or steps.

[0151] The purpose of said at least step (hl) is to recover the excess benzene, implemented during at least said step (bl), and the purpose of said at least step (h2) is to transfer said excess benzene to at least said step (bl).

[0152] Said at least steps (hl) and (h2) thus allow the benzene, which has not reacted, to be recycled to be consumed as a reactant by at least said step (bl).

[0153] In other words, preferably, the process according to the invention comprises at least one recovery step (hl) of the excess benzene, from at least said step (bl), and at least one transfer step (h2) of said excess to at least said step (bl).

[0154] The process according to the invention may further include at least one recovery step (h3) of the benzene produced in step (b2) and, and at least one transfer step (h4) of the benzene to at least the step(s) (bl).

[0155] Said at least step (h3) is thus intended to recover the benzene produced during at least said step (b2), and said at least step (h4) is intended to transfer said benzene produced to at least said step (bl).

[0156] Said at least steps (h3) and (h4) thus allow the benzene produced during step (b2) to be recycled to be consumed as a reactant by at least said step (bl).

[0157] In other words, preferably, the process according to the invention comprises at least one recovery step (h3) of the benzene produced during said step (b2), and at least one transfer step (h4) of said benzene produced to at least said step (bl).

[0158] The process according to the invention may also include at least one step (h5) of adding "fresh" benzene, i.e. which is not implemented at least in step (bl) and / or (b2), to be consumed as a reactant by at least step (bl).

[0159] According to a preferred embodiment, the method according to the invention comprises: i. at least one step (a) of chlorination of toluene, leading at least to the formation of hydrochloric acid (HCl) and at least benzyl chloride, ii. at least one coupling reaction step (b1) between at least the benzyl chloride, obtained at the end of at least said step (a), and benzene, leading at least to the formation of hydrochloric acid (HCl) and diphenylmethane, iii. at least one recovery step (c) of the hydrochloric acid (HCl) formed at the end of at least step(s) (a) and / or (bl), iv. at least one conversion step (d) of hydrochloric acid (HCl) into chlorine (Cl2) and hydrogen (H2) implemented by electrolysis of hydrochloric acid (HCl), v. at least one transfer step (e) of chlorine (Cl2), from at least one conversion step(s) (d), to at least said chlorination step (a), vi. at least one reaction step (b2) between diphenylmethane, obtained at the end of at least step (bl), and toluene, to lead to at least the formation of at least one compound of formula (I) and / or at least one of its geometric isomers, vii. optionally at least one step of adding chlorine (Cl2), which may be obtained from at least one electrolysis process of at least one aqueous solution of sodium chloride (NaCl) or from any other synthesis process, at least in step(s) (a), viii. Optionally, at least one recovery step (g1) of at least one of said alkylated aromatic compound of formula (I) that did not react in step (a) and / or step (b2) and at least one transfer step (g2) of at least one of said alkylated aromatic compound of formula (I) to at least step(s) (a) and / or (b2), ix. Optionally, at least one recovery step (hl) of benzene not having reacted at step (bl) and at least one transfer step (h2) of benzene to at least step (bl), x. optionally at least one recovery step (h3) of the benzene produced in step(s) (b2) and at least one transfer step (h4) of the benzene to at least step(s) (bl), xi. at least one step for valorizing hydrogen (H2) from at least step (d).

[0160] The chlorination step(s) (a), on the one hand, and the coupling and transalkylation reaction step(s) (bl) and (b2), on the other hand, can be carried out at different sites or at the same site.

[0161] Preferably, the chlorination step(s) (a), on the one hand, and the coupling and transalkylation reaction step(s) (bl) and (b2), on the other hand, are carried out at the same site in order to reduce investment costs and the carbon footprint associated with transporting the chloride of the aromatic compound of formula (I) from one site to another.

[0162] Said at least hydrogen (H2) valorization step can be implemented before or after step(s) (e'), (gl) and (g2), and / or (hl) and (h2), preferably after steps (e'), (gl) and (g2), (hl) and (h2).

[0163] The following examples serve to illustrate the invention without, however, being limiting in nature. EXAMPLES Example 1

[0164] In the following example, a process for preparing pure benzyltoluene (BT) (i.e. not comprising dibenzyltoluene) according to the invention is implemented.

[0165] The quantity of hydrochloric acid (HCl) recycled per tonne of benzyltoluene (BT) produced by the process according to the invention is calculated.

[0166] For each quantity of hydrochloric acid (HCl) recycled per tonne of benzyltoluene (BT) produced by the process according to the invention, the volumes of "fresh" chlorine (Cl2) from an electrolysis process of aqueous sodium chloride solutions required for the chlorination step (a) of toluene in the presence of chlorine (Cl2) are calculated, as well as the quantity of sodium hydroxide (NaOH) produced during this electrolysis process, the quantity of NaCl salt consumed during this electrolysis process, and the quantity of hydrogen from this electrolysis process.

[0167] The quantities are given in the following table 1:

[0168] [Tables 1] Quantity of HC1 recycled per tonne of pure BT Quantity of chlorine (kg) Quantity of sodium (kg) Quantity of hydrogen (Nm3) Quantity of salt (kg) 0 390 429 122 780 80 78 86 24 156 90 39 43 12 78 95 20 21 6 39

[0169] The results show that the more HCl the process according to the invention recycles, the more fresh chlorine (Cl2) volumes, i.e., from an electrolysis process of aqueous solutions of sodium chloride needed to carry out the toluene chlorination step decrease.

[0170] Similarly, the more the quantity of HCl recycled per tonne of pure BT increases, the more the quantity of sodium hydroxide (NaOH), co-produced during the salt electrolysis process, decreases.

[0171] Similarly, the more the quantity of HCl recycled per tonne of pure BT increases, the more the quantity of hydrogen, co-produced during the salt electrolysis process, decreases.

[0172] Similarly, the more the quantity of HCl recycled per tonne of pure BT increases, the more the quantity of salt consumed by the electrolysis process decreases.

[0173] The results confirm that the process according to the invention makes it possible to preserve natural resources, such as sodium chloride salts, necessary for the production of new volumes of chlorine (Cl2) and to limit the co-production of soda. Example 2

[0174] In the following example, the volume of hydrogen recovered is calculated as a function of the chlorine (Cl2) recycling rate during the conversion step (d) of the process for preparing benzyltoluene and / or dibenzyltoluene according to the invention.

[0175] Table 2 shows the quantities produced of chlorine, soda and hydrogen (H2) in the case of hydrolysis of an aqueous solution of salt (NaCl).

[0176] Table 3 shows the quantities produced of chlorine (Cl2) and hydrogen (H2) when hydrochloric acid (HCl) is converted by an electrolysis process.

[0177] The results are given in Tables 2 and 3 below:

[0178] [Tables2] NaCl h2o Chlorine NaOH h2 Equivalent 2 2 1 2 1 MM 58.5 18 71 40 2 KG 610.7 187.9 370.6 417.6 10.4 mol 10.44 10.4 5.2 10.4 5.2

[0179] [Tables3] Conversion into chlorine and hydrogen Chlorine H 2 Equivalent 1 1 MM 36.5 71 .Z KG 3 S LO 370.6 10 J mal 10.4 S -7 5.2

[0180] The results show that the conversion step (d) of the process according to the invention makes it possible to obtain the same quantity of chlorine (Cl2) as in an electrolysis process of aqueous sodium chloride solution intended to produce volumes of "fresh" chlorine (Cl2) intended to be consumed in the chlorination step (a).

[0181] The process according to the invention makes it possible to optimize the valorization of products necessary for the decarbonisation of industry.

Claims

1. Demands Process for preparing at least one compound of formula (I) and / or at least one of its geometric isomers: [Chem.l] Formula (I) wherein: ni is an integer with the value 0 or 1, and R represents a methyl group, said process comprising: i. at least one chlorination step (a) of toluene leading at least to the formation of benzyl chloride and hydrochloric acid (HCl), ii. at least one coupling reaction step (bl) between benzyl chloride, obtained at least in step (a), and benzene, leading at least to the formation of diphenylmethane and hydrochloric acid (HCl), iii. at least one recovery step (c) of the hydrochloric acid (HCl) formed at the end of at least said step (a) and / or (bl), iv. at least one conversion step (d) of hydrochloric acid (HCl), recovered at the end of at least said step (c), into chlorine (Cl2), v. at least one transfer step (e) of chlorine (Cl2), from at least said conversion step (d), to said chlorination step (a), vi. at least one reaction step (b2) between diphenylmethane, obtained at the end of said reaction step by coupling (b1), and toluene, leading to the formation of at least one compound of formula (I) and / or at least one of its geometric isomers, vii. Optionally, at least one step (e') of adding chlorine (Cl2), which may be derived from at least one process of electrolysis of at least one aqueous solution of sodium chloride (NaCl) or of any other synthesis process, at said step (a).

2. Method according to claim 1, characterized in that in formula (I), ni is an integer equal to 0.

3. A process according to claim 1 or 2, characterized in that the chlorination step (a) is a radical activation reaction, preferably under the effect of ultraviolet rays.

4. A process according to any one of the preceding claims, characterized in that toluene is in a molar quantity in excess relative to chlorine (Cl2) in said at least chlorination step (a).

5. A process according to any one of the preceding claims, characterized in that said at least conversion step (d) is an electrolysis of hydrochloric acid (HCl) leading to the formation of chlorine (Cl2) and hydrogen (H2).

6. A process according to the preceding claim, characterized in that it further comprises at least one step of valorization (f) of hydrogen (H2), preferably at least one step of storage (f) of all or part of the hydrogen (H2) in the compound(s) of formula (I) and / or at least one of its geometric isomers synthesized in said step (b2).

7. A process according to any one of the preceding claims, characterized in that it comprises at least one step of adding (e') chlorine (Cl2), which may be obtained from at least one process of electrolysis of at least one aqueous solution of sodium chloride (NaCl) or from any other synthesis process, to said at least step (a).

8. A process according to any one of the preceding claims, characterized in that it comprises at least one recovery step (g1) of the toluene that did not react to said at least step (a) and / or said at least step (b2), and at least one transfer step (g2) of said toluene to at least step(s) (a) and / or (b2).

9. A process according to any one of the preceding claims, characterized in that it further comprises at least one step of adding toluene (g3), which is not carried out at least in step(s) (a) and / or (b2), in at least step(s) (a) and / or (b2).

10. A process according to any one of the preceding claims, characterized in that it further comprises at least one recovery step (hl) of benzene that has not reacted to step(s) (bl) and at least one transfer step (h2) of benzene to at least step(s) (bl).

11. A process according to any one of the preceding claims, characterized in that it further comprises at least one recovery step (h3) of the benzene produced in step or steps (b2) and at least one transfer step (h4) of the benzene to at least step or steps (bl).