Purification of aromatic liquids

Abstract

The present invention relates to a process for purifying an aromatic liquid compound, the process comprising at least one step in which the aromatic liquid compound is contacted with a zeolite-type adsorbent material. The present invention also relates to the use of a zeolite-type adsorbent material for purifying an aromatic liquid compound.

Description

[0001] This invention relates to the field of purification of liquid compounds (more particularly aromatic liquid compounds, and even more particularly liquid compounds comprising at least one, preferably at least two, aromatic rings).

[0002] There are currently many applications using aromatic liquid compounds. Aromatic liquid compounds are subjected to various stresses in some cases, and more particularly to thermal stresses of varying degrees, for varying durations, and often with repetitive frequencies.

[0003] When subjected to thermal stress, and more particularly to large and repeated thermal stress, aromatic liquid compounds tend to degrade, thereby significantly reducing the service life of the aromatic liquid compounds, producing degradation products that at best reduce the yield, and even shortening the service life of the aromatic liquid compounds in their intended applications. In more troublesome or even dangerous ways, it can lead to degradation products that are toxic to the environment or even to organisms.

[0004] In particular, degradation of aromatic liquid compounds is typically observed over time at temperatures more or less close to their stability limits. Degradation products are generally classified into two categories: on the one hand, degradation byproducts with low boiling and flash points, referred to as “light” products; the other is “heavy” degradation byproducts, which typically contain one or more optionally fully or partially unsaturated rings, and can be further classified hereinafter as “polyaromatic” and “polycyclic” products.

[0005] Degradation byproducts with low boiling points and low flash points can cause stability and / or safety issues during use, especially fire risks, pump cavitation problems, or pressure increases within the equipment.

[0006] These degradation byproducts, which have low boiling and low flash points, can usually be removed by extracting the vapor phase present in the aromatic liquid compound, especially when brought to a temperature higher than the boiling temperature of the degradation products formed.

[0007] These “light” degradation products can also be separated by various means based on differences in physicochemical properties from the aromatic liquid compounds of interest, particularly by sedimentation, crystallization, recrystallization, and combinations of two or more of these methods. However, these types of methods remain very time-consuming and energy-intensive, thus making them incompatible with profitable industrial applications.

[0008] Another type of "heavy" polyaromatic and polycyclic degradation products can be similarly separated by various means based on differences in physicochemical properties from the aromatic liquid compounds of interest, such as crystallization, recrystallization, and combinations of two or more of these methods. However, as mentioned earlier, these types of methods remain very time-consuming and energy-intensive, thus making them incompatible with profitable industrial applications.

[0009] One approach to overcoming these problems is typically to replace the used aromatic liquid compounds (i.e., compounds contaminated by degradation byproducts). This solution usually involves equipment downtime, the discharge of aromatic liquid compounds containing the generated impurities, and the treatment of the aromatic liquid compounds contaminated by the impurities. It is easy to understand that this solution represents a loss of time and yield, and therefore represents additional operating costs (which can prove substantial).

[0010] Typically, manufacturers treat “light” byproducts (as previously described) by removing the vapor phase, while “heavy” byproducts accumulate at varying rates and have a very negative impact on the performance and / or yield of systems using aromatic liquid compounds.

[0011] Therefore, there remains a great need for solutions that can limit or delay the formation and / or accumulation of impurities (especially “heavy” byproducts generated during the degradation of organic liquid compounds) to extend the lifespan of the aromatic liquid compounds in their use and thereby prevent the release of toxic compounds into the environment, especially in applications where the aromatic liquid compounds are subjected to large and repeated thermal stresses.

[0012] It has now been unexpectedly discovered that the aforementioned objectives can be achieved, in whole or at least in part, by the present invention. Further objectives will become clear in the following description of the invention.

[0013] Therefore, the inventors have now discovered that the lifespan of the aromatic liquid compound can be greatly improved by capturing the degradation products formed during the use of the aromatic liquid compound, and this capture is carried out by selectively adsorbing the degradation products.

[0014] Therefore, in a first aspect, the present invention relates to a process for purifying an aromatic liquid compound, the process comprising at least the step of contacting the aromatic liquid compound with a zeolite-type adsorbent material.

[0015] In the context of this invention, an "aromatic liquid compound" is a compound comprising at least one aromatic ring, and preferably at least two aromatic rings (e.g., 2, 3, or 4 aromatic rings), and its partially or fully hydrogenated homologues. A partially or fully hydrogenated homologue means that one aromatic ring (or two or more aromatic rings) is partially or fully hydrogenated. Unless otherwise stated, the aromatic liquid compounds of this invention are defined in their fully dehydrogenated form, which means that the definition also covers said organic liquid compounds in their fully or partially hydrogenated form. Among these fully or partially hydrogenated forms, it is preferred that at least one aromatic ring is in its fully dehydrogenated form.

[0016] Thus, quite unexpectedly, it has been found that the treatment of aromatic liquid compounds (which are optionally at least partially or completely hydrogenated) can be simplified, and more particularly, the amount of degradation products can be significantly or even completely reduced by contacting the liquid compounds with zeolite-type adsorbent materials (or materials comprising at least one of the following adsorbents, which are one or more zeolites in any form, more particularly in the form of crystals and / or zeolite-type aggregates).

[0017] According to one embodiment of the invention, degradation products in aromatic liquid compounds (which can be removed or at least their amount can be greatly reduced by means of the process of the invention) are generally and typically the most commonly encountered degradation products, including, as non-limiting examples, benzene, toluene, xylene, ethyltoluene, aniline, phenol, naphthalene, and their fully or partially hydrogenated forms, such as cyclohexane, methylcyclohexane, etc., and more generally, aromatic aprotic nonpolar degradation products of the aromatic liquid compounds (or in fully or partially hydrogenated forms).

[0018] The amount of degradation products in aromatic liquid compounds (which can be removed or at least greatly reduced) can vary over a wide range and is typically between 1 ppm and 10,000 ppm (by mass).

[0019] The aromatic liquid compound used in the purification process of this invention can be any type of compound that is liquid at ambient temperature and pressure (25°C, 1 atmosphere) and contains at least one aromatic ring in its non-hydrogenated form, and preferably contains at least two aromatic rings in their non-hydrogenated form. The aromatic liquid compounds available in the process of this invention may optionally be at least partially or even fully hydrogenated. These aromatic liquid compounds, optionally at least partially or even fully hydrogenated, are generally obtained from petroleum products and / or products synthesized from petroleum products, but may also be obtained from renewable products and / or products synthesized from renewable products.

[0020] It should be understood that the aromatic liquid compounds used in the process of the present invention may take the form of a mixture of one or more aromatic liquid compounds (which may optionally be partially or even completely hydrogenated), and for example, a mixture of aromatic liquid compounds obtained from petroleum products and / or from renewable products.

[0021] In the context of this invention, aromatic liquid compounds derived from petroleum products refer to products obtained from the separation and / or purification of petroleum, as well as compounds obtained from the synthesis of compounds containing aromatic rings of petroleum origin. In the context of this invention, aromatic liquid compounds derived from renewable products refer to products obtained from biomass (and particularly from the extraction of wood (e.g., lignin) and resin-type products), as well as compounds obtained from the synthesis of renewable products.

[0022] According to a preferred embodiment, the aromatic liquid compound that can be used in the process of the present invention conforms to the general formula (1):

[0023] (AX) n -B (1)

[0024] in:

[0025] -A and B, whether identical or different and independent of each other, represent an aromatic ring that is optionally fully or partially hydrogenated; optionally contains at least, and preferably, one heteroatom; and optionally is substituted by one or more saturated or partially or fully unsaturated hydrocarbon groups comprising 1 to 20 carbon atoms, preferably 1 to 18 carbon atoms, more preferably 1 to 12 carbon atoms, even better 1 to 10 carbon atoms, even better 1 to 6 carbon atoms, typically 1 to 3 carbon atoms.

[0026] -X represents a spacer group, selected from single bonds, oxygen atoms, sulfur atoms, and divalent groups (CRR'). m -, divalent group >C=CRR', and divalent group -NR”-, or

[0027] When n is not 0 (zero), X and the aromatic ring it is attached to form a saturated or unsaturated ring containing 4 to 10 ring members, wherein one or more of these ring members may be heteroatoms selected from oxygen, nitrogen, and sulfur. The saturated or unsaturated ring may be further replaced by one or more hydrocarbon chains containing 1 to 30 carbon atoms, preferably 1 to 10 carbon atoms.

[0028] -R and R' are the same or different and are selected independently from: hydrogen; and saturated or partially or completely unsaturated hydrocarbon groups comprising 1 to 6 carbon atoms, preferably 1 to 3 carbon atoms.

[0029] "-R" represents a saturated or partially or completely unsaturated hydrocarbon group containing 1 to 6 carbon atoms, preferably 1 to 3 carbon atoms.

[0030] -m represents an integer between 1 and 4, inclusive, and

[0031] -n can be equal to 0 or represent an integer equal to 1, 2 or 3, preferably equal to 1 or 2. The restriction is that when n is equal to 0, B is substituted by one or more hydrocarbon groups as defined above.

[0032] The term "aromatic ring" is understood to mean monocyclic and polycyclic aromatic hydrocarbons containing 6 to 20 carbon atoms, wherein one or more of the ring members may be heteroatoms selected from oxygen, sulfur, and nitrogen, preferably selected from sulfur and nitrogen, and more preferably nitrogen. "Polycyclic compound" is understood to mean the aforementioned rings that are fused or condensed, for example, two, or more preferably two, three, or four, more preferably two or three, for example, two fused or condensed rings.

[0033] When n equals 0, the aromatic liquid compound of formula (1) as defined above forms part of an optionally partially or fully hydrogenated alkylbenzene class. When n equals 2 or 3, the groups (AX) may be the same or different.

[0034] In a preferred embodiment of the invention, in the aromatic liquid compound of general formula (1), n ​​is equal to 0 and the organic liquid of formula (1) is generally selected from linear alkylbenzenes (which are optionally fully or partially hydrogenated) and branched alkylbenzenes (which are optionally fully or partially hydrogenated), for example, but not limited to, alkylbenzenes and fully or partially hydrogenated homologues, wherein the alkyl portion comprises 10 to 20 carbon atoms.

[0035] Such alkylbenzenes include, again, but are not limited to, decylbenzene, dodecylbenzene, octadecylbenzene, and their homologues that are fully or partially hydrogenated, to name only some of them.

[0036] In another preferred embodiment of the invention, the aromatic liquid compound of general formula (1) exhibits at least two aromatic rings, and in this case, n is not 0 and B is substituted with a hydrocarbon group. More preferably, the hydrocarbon group is an alkyl group containing 1 to 6 carbon atoms, preferably 1 to 4 carbon atoms, and preferably the alkyl group is a methyl group.

[0037] As previously stated, aromatic liquid compounds conforming to general formula (1) above can be used alone or as a mixture of two or more of them in any proportion. According to a preferred embodiment of the invention, the aromatic liquid compound used in the process of the invention may comprise a compound having at least one aromatic group (optionally fully or partially hydrogenated) or a mixture of two or more compounds having at least one aromatic group (optionally fully or partially hydrogenated). As previously stated, the aromatic liquid compound used in the process of the invention is liquid at ambient temperature and ambient pressure.

[0038] According to yet another preferred embodiment of the invention, the aromatic liquid compound is selected from benzyltoluene (BT), dibenzyltoluene (DBT), their partially or completely hydrogenated homologues, and mixtures thereof in any proportion.

[0039] In a very particularly preferred embodiment, the aromatic liquid compound is selected from Arkema. Organic fluids sold under a series of product names.

[0040] Other aromatic liquid compounds suitable for the requirements of this invention, as well as partially or fully hydrogenated homologues, are, for example, those from Eastman (especially under the trade name...). Those that are sold.

[0041] Other examples of aromatic liquid compounds suitable for the requirements of this invention include the following:

[0042] - Diphenyl ethane (DPE) and its isomers, more particularly 1,1-DPE (CAS 612-00-0), 1,2-DPE (CAS 103-29-7) and mixtures thereof (especially CAS 38888-98-1), such organic liquids are commercially available or described in the literature (e.g., in document EP0098677),

[0043] - Xylyl ethers (DT) and their isomers, especially those corresponding to CAS numbers 4731-34-4 and CAS 28299-41-4 and their mixtures, are particularly available commercially from Lanxess under the name Diphyl DT.

[0044] 1,2-phenylxylylethane (PXE) and its isomers, especially those corresponding to CAS numbers 6196-95-8 and CAS 76090-67-0 and their mixtures, are commercially available from Changzhou Winschem under the trade name PXE Oil.

[0045] - Mono-xylyl xylene and bis-xylyl xylene, their isomers and mixtures thereof (CAS 186466-85-3),

[0046] -1,2,3,4-Tetrahydro-(1-phenylethyl)naphthalene (CAS 63674-30-6), this product is particularly available from Dow under the designation Dowtherm. TM Obtained through RP purchase.

[0047] -Diisopropylnaphthalene (CAS 38640-62-9), specifically available from Indus Chemie Ltd under the trademark KMC 113,

[0048] - Monoisopropylbiphenyl and its isomers (CAS 25640-78-2), especially available under the trade name Wemcol.

[0049] - Phenylacetylphenylethane (PEPE) and its isomers (CAS 6196-94-7), particularly available from Changzhou Winschem or Yantai Jinzheng,

[0050] -N-ethylcarbazole, in particular, is available from Allessa GmbH.

[0051] -Phenylated, Tolylpyridine, Diphenylpyridine, Dipyridylbenzene, Dipyridinetoluene

[0052] -and its partially or completely hydrogenated homologues,

[0053] -and mixtures of two or more of them in any proportion,

[0054] Only the major organic liquids known and applicable in the context of this invention are mentioned.

[0055] As previously described, the process of the present invention allows for the purification of liquid compounds by contacting organic liquid compounds with zeolite-type adsorbent materials. Zeolite-type adsorbent materials (these are materials comprising one or more zeolites) are well known to those skilled in the art for removing small molecules, typically present in trace amounts, from gaseous or liquid streams.

[0056] Moreover, zeolite-type adsorbent materials typically contain synthetic zeolites, which, thanks to the wide range of variations in their preparation processes, offer a variety of parameters (which can be adjusted for precise tuning), such as thermal stability, mechanical strength, or regeneration capacity, to meet specific criteria required for the intended use.

[0057] Zeolite-type adsorbent materials used in the context of this invention can be of any type known to those skilled in the art. The most suitable zeolite-type adsorbent materials include natural or synthetic zeolites, and more particularly, zeolite-type adsorbent materials are selected from natural zeolites (such as chalcogenide), and from LTA-type zeolites, FAU-type zeolites, EMT-type zeolites, MFI-type zeolites, and *BEA-type zeolites. These different types of zeolites are readily available commercially or readily synthesized by known procedures available in scientific and patent literature. Furthermore, different types of zeolites are clearly defined and listed, for example, in "Atlas of Zeolite Framework Types" (5th edition, (2001), Elsevier).

[0058] For the purposes of this invention, a mixture of two or more zeolites in any proportion can be used as a zeolite-type adsorbent material. Hierarchical porous homologues of the aforementioned zeolites (referred to as "HPZ") can also be used, which are typically obtained as follows: by direct synthesis, particularly using sacrificial agents, as described, for example, in patent applications WO2015 / 019013 or WO2007 / 043731; or by surface post-treatment, as described, for example, in WO2013 / 106816.

[0059] The zeolites listed above may be used in their “natural” form (i.e., in crystalline form), but are preferably used by techniques known to those skilled in the art as zeolite crystal agglomerates having one or more binders, and particularly by agglomerating zeolite crystals using an agglomerating binder. The agglomerating binder may be of any type capable of agglomerating and coheding zeolite crystals and is generally selected from mineral clays, non-limiting examples of which include kaolin, kaolinite, attapulgite, sepiolite, clinoptilolite, etc., and mixtures of two or more of these clays in any proportion.

[0060] Therefore, advantageously, before drying and / or baking and / or calcining, the zeolite crystals are agglomerated using at least one agglomerating binder; and, if necessary or desired, one or more additives known to those skilled in the art.

[0061] Additives are also well known to those skilled in the art, and their properties and the amount added can vary over a wide range depending on the desired or required effect. Examples of additives that can be used with agglomerating binders include, but are not limited to, surface passivating additives (which function to control the surface reactivity of agglomerates and / or enhance their separation selectivity, e.g., tetrasodium pyrophosphate (TSPP)), as well as rheology modifiers, granulation additives, and mixtures of two or more of them.

[0062] Agglomerated zeolite crystals can also participate in zeolization operations, as is well known to those skilled in the art. This involves converting some or all of the agglomerating binder into a zeolite-type crystalline material to increase the adsorption capacity of the agglomerates. Techniques for the agglomeration, drying, baking, calcination, and zeolization of zeolite crystals are comprehensively described in scientific and patent literature, such as applications WO1999 / 010096 and WO2000 / 050166.

[0063] The zeolites (crystals and aggregates) described above typically and often contain cations to make them electronically neutral. As a non-limiting example, the most commonly used cations are selected from alkali metals, alkaline earth metals, and transition metals, and more particularly from sodium, potassium, calcium, barium, strontium, magnesium, iron, copper, and silver cations. Zeolite-type adsorbent materials used in the context of this invention may, of course, contain one or more of the cations listed above.

[0064] The cations present in zeolite-type adsorbent materials applicable in the context of this invention are derived directly from the synthesis of the adsorbent material (particularly for sodium cations of zeolites prepared from sodium-containing solutions) or via one or more cation exchange operations using conventional techniques known to those skilled in the art, wherein the exchange may be performed on the initial zeolite crystals and / or zeolite crystal agglomerates, before and / or during and / or after their formation (preferably before and / or after their shaping).

[0065] In practice, if necessary or desired, zeolite-type adsorbent materials used in the context of this invention can and generally be shaped by any technique known to those skilled in the art, and more particularly by extrusion, granulation, etc., to be shaped into forms such as beads, extrudates, etc., for example, monolithic solids and membranes.

[0066] According to one embodiment of the process of the present invention, a zeolite-type adsorbent material comprising one or more zeolites selected from the following zeolites is preferably used:

[0067] -LTA zeolite, preferably 5A zeolite, more particularly those containing calcium cations, and its homologues with hierarchical porosity (homogeneous zeolites containing mesopores and micropores),

[0068] -FAU type zeolites, more particularly zeolites LSX, MSX, X and Y, and even more particularly zeolites having a Si / Al atomic ratio between 1 and 3, and their homologues with hierarchical porosity (homogeneous zeolites including mesopores and micropores), such as those described in applications WO2015 / 019013, WO2015 / 019014, WO2015 / 028740 and WO2015 / 028741.

[0069] -FAU type zeolites, and more particularly zeolites with a Si / Al atomic ratio strictly greater than 3, such as USY zeolite and dealuminated Y zeolite.

[0070] -EMT zeolite or EMT-FAU symbiotic zeolite phase, having a Si / Al atomic ratio between 1 and 4, and its hierarchical porous homologues (homogeneous zeolites containing mesoporous and microporous structures), such as those described in application WO2014 / 177567A1.

[0071] -MFI type zeolites, typically having a Si / Al atomic ratio between 8 and 500, preferably between 8 and 250, more preferably between 8 and 100, advantageously between 8 and 50, and even more preferably between 8 and 40, and especially ZSM-5 zeolite, and its hierarchical porous homologues (homogeneous zeolites containing mesoporous and microporous structures), and

[0072] -*BEA type zeolite, typically BETA zeolite having a Si / Al atomic ratio of more than 7, and preferably between 8 and 20.

[0073] In a preferred embodiment, zeolite-type adsorbent materials particularly suitable for the process according to the invention are materials comprising: FAU-type zeolite; one or more cations selected from Na, K, Ba, Ca, Mg, Li, Sr, Ag, Cu, and more particularly NaX, BaX, BaKX, NaCaX, CaBaNaX, NaY, BaY, NaKY, BaKY, and mixtures thereof. These zeolites are commercially available, and most of them are sold by Arkema.

[0074] Therefore, the process for purifying aromatic liquid compounds according to the present invention includes at least one step in which the liquid compound is contacted with a zeolite-type adsorbent material as defined above. It should be understood that the process of the present invention employs one or more zeolite-type adsorbent materials as defined above.

[0075] The contact step can advantageously be carried out at temperatures between -20°C and 250°C, preferably between -15°C and 150°C, preferably between -10°C and 100°C, preferably between -5°C and 80°C, preferably between -5°C and 50°C, advantageously at ambient temperature (in other words at operating temperature), and more specifically, for the obvious economic efficiency of the process of the present invention, without the supply of heat or cold.

[0076] Similarly, the contact step can be performed under pressure, at atmospheric pressure, at reduced pressure, or even under vacuum. However, the operation is preferably performed at atmospheric pressure, or at a pressure that may be up to 20 bar (2 MPa), preferably 2 bar (200 kPa), and especially preferably at atmospheric pressure (i.e., at the working pressure). More specifically, for the obvious economic efficiency of the process of the present invention, it is performed without any supply pressure or reduced pressure, except for the pressure difference generated by devices such as pumps, valves, etc.

[0077] The contact time can vary over a wide range, depending in particular on the nature and amount of the impurities to be removed, the nature and amount of the zeolite-type adsorbent material used, the nature and amount of the liquid to be purified, and the type of contact system used. Furthermore, the contact time varies with the applied temperature and pressure.

[0078] Contact with the zeolite-type adsorbent material can be carried out continuously or intermittently according to any method known to those skilled in the art, and can be carried out, for example, by forcing (pumping) or passing the liquid through the zeolite-type adsorbent material by gravity (e.g. in a packed tower), or by simple contact in a reactor (e.g., a reactor optionally equipped with a stirring system).

[0079] More specifically, the steps in the process of contacting the aromatic liquid to be purified with at least one zeolite-type adsorbent material can be carried out in various static (or intermittent), dynamic, semi-continuous, or continuous processes. For subsequent processes, the stream to be purified typically passes through an adsorbent bed, where contaminants are selectively retained according to specific criteria, such as the type of contaminant (polarity, diameter, volume), the type of stream (gas, liquid), and operating conditions (temperature, pressure), etc.

[0080] Therefore, the contact step can occur individually or multiple times, in an intermittent and / or static manner, in a storage tank, with or without stirring, dynamically or continuously. This purification step preferably occurs before any storage step of the liquid to be treated, and preferably, dynamically through an adsorbent bed, more preferably, dynamically through a stationary adsorbent bed. Therefore, and as a non-limiting example, the contact step in the process of the present invention can be implemented in an intermittent manner, and in this case, one embodiment includes placing an adsorbent bed at the bottom of a container in which the aromatic liquid to be purified is stored, for a duration that can vary depending on the degree of contamination and the type of contaminant to be removed. This time can indeed vary over a wide range and is typically between minutes and days, for example, between 1 hour and 48 hours.

[0081] Alternatively, the contact step can be carried out continuously by any known dynamic process, in which the liquid to be purified passes through a bed of zeolite-type adsorbent material under the previously indicated temperature and pressure conditions. The flow rate of the liquid continuously passing through the adsorbent bed can vary over a wide range depending on the degree of contamination and the type of contaminant to be removed, but is typically regulated to allow contact times generally between minutes and days, for example, between 1 hour and 48 hours. The bed of zeolite-type adsorbent material can be of any type known to those skilled in the art, and more particularly, a fixed bed, a fluidized bed, or a moving bed (simulated or otherwise). In the case of continuous contact, a fixed bed with screen regeneration is preferred, or operation in two adsorbers (the first operating under adsorption and the second under desorption / regeneration).

[0082] In fact, according to a particularly advantageous embodiment of the invention, zeolite-type adsorbent materials can be desorbed and / or regenerated intermittently or continuously by conventional desorption and regeneration techniques, and in particular by heat treatment and / or by means of one or more desorption solvents.

[0083] Therefore, the process of the present invention uses at least one zeolite-type adsorbent material as described above, which can exist in various forms (especially adsorbent beds), for example, one or more types of zeolite in the form of a mixture of crystals or agglomerates, or multiple identical or different adsorbent beds in the same adsorber, wherein one or more adsorbers can be used in series and / or in parallel to maximize the selectivity and extent of removal of impurities present in aromatic fluids (especially monocyclic impurities, such as toluene, benzene, methylcyclohexane, xylene, ethyltoluene, aniline, phenol, naphthalene and their at least partially or fully hydrogenated homologues).

[0084] More specifically, the process of the present invention includes at least the following steps:

[0085] a) Provide an aromatic liquid containing at least one impurity.

[0086] b) Contact the aromatic liquid with at least one zeolite-type adsorbent material.

[0087] c) Collect the aromatic liquid containing the at least one impurity, wherein the weight concentration of the at least one impurity is less than 50% by weight, preferably less than 40% by weight, preferably less than 30% by weight, more preferably less than 20% by weight, relative to the level of impurities present in the liquid from step a).

[0088] d) Optionally regenerate and / or desorb the at least one zeolite-type adsorbent material.

[0089] The process of the present invention is particularly suitable for purifying aromatic liquids containing at least one aromatic ring (and preferably at least two aromatic rings) and contaminated with one or more of the aforementioned impurities, such as byproducts generated during the decomposition of organic liquid compounds, and especially monocyclic impurities, such as toluene, benzene, methylcyclohexane, xylene, ethyltoluene, aniline, phenol, naphthalene and their at least partially or fully hydrogenated homologues, to name only the main representatives, but not limited thereto.

[0090] Therefore, the process according to the invention can be used in a wide range of applications, especially in applications where aromatic liquids are subjected to degradation conditions such as thermal changes (whether significant or periodic) and chemical modifications (whether reversible).

[0091] Possible non-limiting examples of such application areas include those in which aromatic liquids are used as heat transfer fluids or dielectric fluids, or in those in which aromatic liquids are used as liquid organic hydrogen carriers (also referred to by the acronym "LOHC"), as described in application WO2014 / 082801.

[0092] In fact, the process of the present invention is particularly suitable for purifying heat transfer liquids or LOHC liquids, and especially applicable to aromatic liquids benzyltoluene and dibenzyltoluene, alone or in any proportion. According to a particularly preferred embodiment, the process of the present invention involves purifying benzyltoluene or dibenzyltoluene or mixtures thereof by contacting with one or more zeolite-type adsorbents based on one or more FAU-type zeolites as described above.

[0093] As mentioned above, the process of the present invention can be carried out intermittently or continuously, once or multiple times, depending on the requirements encountered in the relevant application fields.

[0094] Therefore, and for example in the case of using LOHC, the organic liquid can be purified once or multiple times before or after one or more steps in the process (and for example before the dehydrogenation step and / or before the hydrogenation step).

[0095] Finally, in another aspect, the present invention relates to the use of the zeolite-type adsorbent materials just defined for the purification of the previously defined aromatic liquid compounds.

Claims

1. A process for purifying an aromatic liquid compound, the process comprising at least the step of contacting the aromatic liquid compound with a zeolite-type adsorbent material, the aromatic liquid compound containing degradation products formed during the use of the aromatic liquid compound, wherein the degradation products are captured by selective adsorption, wherein the aromatic liquid compound is selected from benzyltoluene (BT), dibenzyltoluene (DBT), partially or completely hydrogenated homologues thereof, and mixtures thereof in any proportion.

2. The process claimed in claim 1, wherein, Zeolite-type adsorbent materials are materials containing at least one of the following adsorbents, which are one or more zeolites in the form of crystals and / or zeolite-type aggregates.

3. The process claimed in claim 1 or 2, wherein, The zeolite-type adsorbent material is selected from natural or synthetic zeolites.

4. The process claimed in claim 3, wherein, The zeolite-type adsorbent material is selected from chabazite, LTA-type zeolite, FAU-type zeolite, EMT-type zeolite, MFI-type zeolite, and... BEA type zeolite.

5. The process claimed in claim 1 or 2, wherein, The zeolite-type adsorbent material contains at least one cation selected from alkali metals, alkaline earth metals, and transition metals.

6. The process claimed in claim 5, wherein, The zeolite-type adsorbent material contains at least one cation selected from sodium, potassium, calcium, barium, strontium, magnesium, iron, copper, and silver.

7. The process claimed in claim 1 or 2, wherein, The zeolite-type adsorbent material comprises one or more zeolites selected from the following: - LTA zeolite, and its homologues with hierarchical porosity, - FAU type zeolites, selected from zeolites LSX, MSX, X and Y, with a Si / Al atomic ratio between 1 and 3, and their homologues with hierarchical porosity. - FAU type zeolite, selected from zeolites with a strictly greater than 3 Si / Al atomic ratio. - EMT zeolite or EMT-FAU symbiotic zeolite phase, with a Si / Al atomic ratio between 1 and 4, and its hierarchical porous homologues. - MFI type zeolites, and their hierarchical porous homologues, and - BEA type zeolite.

8. The process claimed in claim 7, wherein the LTA zeolite is 5A zeolite.

9. The process claimed in claim 7, wherein the LTA zeolite is one that contains calcium cations.

10. The process claimed in claim 7, wherein the MFI type zeolite is a zeolite having a Si / Al atomic ratio between 8 and 500.

11. The process claimed in claim 7, wherein the MFI type zeolite is a zeolite having a Si / Al atomic ratio between 8 and 250.

12. The process claimed in claim 7, wherein the MFI type zeolite is a zeolite having a Si / Al atomic ratio between 8 and 100.

13. The process claimed in claim 7, wherein the MFI type zeolite is a zeolite having a Si / Al atomic ratio between 8 and 50.

14. The process claimed in claim 7, wherein the MFI type zeolite is a zeolite having a Si / Al atomic ratio between 8 and 40.

15. The process claimed in claim 7, wherein the MFI type zeolite is ZSM-5 zeolite.

16. The process claimed in claim 7, wherein BEA-type zeolites are BETA zeolites with a Si / Al atomic ratio exceeding 7.

17. The process claimed in claim 7, wherein BEA-type zeolites are BETA zeolites with a Si / Al atomic ratio between 8 and 20.

18. The process claimed in claim 1 or 2, wherein, The zeolite-type adsorbent material comprises the following materials: FAU-type zeolite; one or more cations selected from Na, K, Ba, Ca, Mg, Li, Sr, Ag, and Cu.

19. The process claimed in claim 18, wherein, The zeolite-type adsorbent material is a material containing one of the following: NaX, BaX, BaKX, NaCaX, CaBaNaX, NaY, BaY, NaKY, BaKY, and mixtures thereof.

20. The process claimed in claim 1 or 2, comprising at least the following steps: a) Provide an aromatic liquid containing at least one impurity. b) Contact the aromatic liquid with at least one zeolite-type adsorbent material. c) Collect the aromatic liquid containing the at least one impurity, wherein the weight concentration of the at least one impurity is less than 50% by weight relative to the level of impurities present in the liquid from step a). d) Optionally, regenerate and / or desorb the at least one zeolite-type adsorbent material. The at least one impurity is a degradation product formed during the use of the aromatic liquid compound.

21. The process claimed in claim 20, wherein the weight concentration of the at least one impurity is less than 40 wt% relative to the level of impurities present in the liquid from step a).

22. The process claimed in claim 20, wherein the weight concentration of the at least one impurity is less than 30 wt% relative to the level of impurities present in the liquid from step a).

23. The process claimed in claim 20, wherein the weight concentration of the at least one impurity is less than 20 wt% relative to the level of impurities present in the liquid from step a).

24. The use of zeolite-type adsorbent materials for purifying aromatic liquid compounds by means of the process defined in any one of claims 1 to 23.

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