Method for treating waste lubricating oils comprising esters

Abstract

The present disclosure relates to the field of treatments for lubricating and / or cooling compositions, in particular waste lubricating and / or cooling compositions. In particular, the present disclosure relates to a method for treating waste lubricating and / or cooling compositions comprising esters, in order to improve the recyclability of same.

Description

Process for treating used lubricating oils comprising esters

[0001] This disclosure relates to the treatment of lubricants and / or coolants, including used lubricants. Specifically, this disclosure concerns a method for treating used lubricants and / or coolants containing esters to improve their recyclability. Previous technique

[0002] Lubricating compounds, more simply known as "lubricants," are commonly used in mechanical systems primarily to reduce friction between moving metal parts and to prevent premature wear or even damage to these parts, particularly their surfaces. For example, they are used in various vehicle mechanical systems, including the engine, transmission, and hydraulic system.

[0003] During their use, lubricating compositions are subjected to stresses which cause their degradation and lead to an increase in the rate of undesirable elements, which may come from a degradation of the base oil itself or of the additives generally present in the lubricating compositions, from external pollutants, such as dust, elements emanating from the wear of the parts with which the oil is in contact during its use or even fuel fractions from the engine.

[0004] These various undesirable elements can negatively impact the properties of the lubricating composition, which, after use, becomes a "used," "worn," or "degraded" lubricant. This is why lubricating compositions need to be replaced after a certain period of use.

[0005] In light of current environmental protection and resource conservation challenges, methods have been developed to re-refine, recycle, or recondition used lubricating compositions. This allows for the regeneration of used lubricating oils, which can then be reused in the formulation of new lubricating compositions.

[0006] Furthermore, in an effort to optimize resources and reduce the carbon footprint of lubricants, an increasing number of lubricating compositions include bio-based compounds such as plant-derived triglycerides, or esters of polyols and natural fatty acids. The content of bio-based compounds in lubricating compositions, and particularly esters, is increasing year after year.

[0007] However, the presence of esters in lubricant compositions causes problems during the re-refining or recycling of used lubricant compositions. These processes include a step of treating used lubricating oils with caustic soda to neutralize the free acids formed, which can corrode the recycling equipment. The caustic soda then reacts with the esters present, leading to the formation of solid soaps that can clog the process lines. These problems are so significant that as soon as a Used lubricating oil with an ester content of 5% or higher cannot be regenerated using current processes. Therefore, this type of used lubricating oil is not recycled but incinerated.

[0008] Therefore, there is a need to treat used lubricating oils containing esters so that they can be recycled and re-refined using existing processes. Summary

[0009] This disclosure proposes to treat lubricating oils, including used ones, containing esters with a method comprising a treatment step with a weak base having a pKb between 2 and 6.

[0010] This disclosure relates to a process for treating a lubricating and / or cooling composition comprising at least one ester and at least one free organic acid, said process comprising a step of treating said composition with at least one base having a pKb between 2 and 6.

[0011] Treating used lubricating oils with a weak base having a pKb between 2 and 6 neutralizes the free acids present in the lubricants without causing saponification of the esters. Since the pKb of the weak base is higher than that of sodium hydroxide (NaOH pKb = 0), the esters in the used lubricants do not react with the weak base; only the free acids are neutralized. Therefore, no solid soaps are formed during treatment with a weak base. It is then possible to re-refine and recycle the used lubricating oils using existing processes.

[0012] This process increases the content of bio-based esters in lubricant compositions, as it allows for the re-refining and recycling of used lubricating oils regardless of their ester content. This avoids the incineration of used lubricating oils, increases the proportion of used lubricating oils that are recycled, and improves the carbon footprint of these lubricating oils. Detailed description

[0013] As stated above, this disclosure relates to a process for treating a lubricating and / or cooling composition comprising at least one ester and at least one free organic acid, said process comprising a step of treating said composition with at least one base having a pKb between 2 and 6.

[0014] The expressions "between ... and ...", "ranging from ... to ...", "made up of ... to ...", and "varying from ... to ...", should be understood inclusively, unless otherwise stated.

[0015] In this disclosure, pKb is used to define the strength of the base, pKb = -log(Kb) where Kb is the basicity constant. The lower the pKb, the stronger the base.

[0016] In the description and examples, unless otherwise stated, percentages are mass percentages. Therefore, percentages are expressed as a percentage of the total mass of the composition. Lubricating and / or cooling composition to be treated

[0017] The composition to be treated is a lubricating and / or cooling composition.

[0018] According to the invention, the term "lubricating composition" (or simply "lubricant" or "lubricating oil") refers to any composition that can be used for the lubrication of moving parts, particularly metal parts, of a mechanical system, such as bearings, gears, or motors. A "used lubricating composition" (or simply "used lubricant" or "used oil") refers to a composition that has been used for this purpose.

[0019] The lubricant composition to be treated is generally a used lubricant composition, and it can come from various sources. In particular, as detailed later in the text, it may be a lubricant that has been used to lubricate a motor system, especially a "mobile" one, or to lubricate an industrial system, especially a "stationary" one.

[0020] It is understood that the lubricating composition to be treated may be a mixture of several lubricating compositions, including used ones, from the same source or from several different sources.

[0021] Due to their origin, used lubricants, particularly engine lubricants, contain a number of degradation products derived from the oil itself or its additives, as well as metal particles, metal oxides, and other elements, originating, for example, from the engine. Used oil may contain, in particular, high levels of undesirable elements, such as calcium (Ca), iron (Fe), magnesium (Mg), sodium (Na), nickel (Ni), phosphorus (P), silicon (Si), chlorine (Cl), zinc (Zn), etc.

[0022] A "cooling composition" is defined as a composition that can be used as a coolant for moving parts in a mechanical system, or for stationary components such as data centers or charging stations. Specifically, it can be used to cool the power electronics and / or the rotor and / or stator of an electric motor, or to cool the battery in an electric or hybrid vehicle. A "used cooling composition" refers to a composition that has been used for this purpose.

[0023] In one embodiment, the composition to be treated is both a lubricating and cooling composition. Indeed, friction between moving parts in a mechanical system generates heat, and it may be necessary to simultaneously provide cooling and lubrication to the mechanical systems. The composition to be treated then has a dual function and can provide, or have provided, both lubrication and cooling of moving parts in a mechanical system, particularly in a mobile or stationary drive system, and more specifically in a vehicle propulsion system, for example, in the propulsion system of an electric or hybrid vehicle.

[0024] The lubricating and / or cooling composition to be treated comprises at least one ester. The ester has the general formula R'-C(O)-OR, with an acidic part or acidic residue of formula R'- C(O)-, and an alcohol portion or alcohol residue of formula -OR comprising m carbon atoms and one or more alcohol functional groups. The number of carbon atoms m is an integer, for example, from 1 to 20, or from 3 to 10. The alcohol residue of formula -OR comprises one or more alcohol functional groups. When the alcohol residue of formula -OR comprises several alcohol functional groups, it is a polyol. It may, for example, comprise from 1 to 5 alcohol functional groups. In one embodiment, the ester(s) contained in the lubricating and / or cooling composition to be treated are esters having an alcohol residue comprising at least 3 carbon atoms, preferably at least 4 carbon atoms, or which is a polyol residue.Lubricating and / or cooling compositions to be treated may include esters having a long-chain alcohol portion (e.g., at least 3 carbon atoms, or at least 4 carbon atoms) and / or esters having an alcohol portion that is a polyol, such as glycerol, trimethylol propane, or neopentyl glycol.

[0025] When the composition to be treated includes esters having an alcohol residue comprising m carbon atoms, the alcohol residue has the formula -OR, where R is a carbon chain comprising m carbon atoms, m being an integer, for example between 3 and 20, or between 4 and 10. The carbon chain can be linear or branched, and it can be substituted or unsubstituted. It can have between 4 and 30 carbon atoms, for example between 5 and 22 carbon atoms.

[0026] When the composition to be treated includes esters with an alcohol residue that is a polyol residue, the alcohol residue has the formula -OR, where R represents a polyol residue. R then represents a carbon chain containing at least one other alcohol functional group, for example, between one and four additional alcohol functional groups. The carbon chain R comprises at least two carbon atoms. The carbon chain can be linear or branched, and it can be substituted or unsubstituted. It can have between two and ten carbon atoms, for example, between two and five carbon atoms. The other alcohol functional groups of the polyol can be in free form (-OH) or not. They can, for example, also be in ester form, which is notably the case for triglycerides when the alcohol portion is glycerol.

[0027] According to one embodiment, the esters contained in the lubricating and / or cooling composition to be treated are selected from - aliphatic acid esters, where the aliphatic acid residue comprises a hydrocarbon chain preferably having 3 to 36 carbon atoms and one or two alcohol functional groups, - polyol esters, preferably glycerol, trimethylolpropane, or neopentyl glycol esters, - unsaturated fatty acid polyesters containing up to 6 acid units, and - their mixtures.

[0028] According to one embodiment, the esters contained in the lubricating and / or cooling composition to be treated are at least partly bio-based. "Bio-based" means, for example, a product prepared from materials of biological origin, that is, from raw materials of non-fossil origin. For example, the esters contained in the lubricating and / or cooling composition to be treated may be bio-based at a content greater than or equal to 50%. 60%, 70%, 80%, 90%, 95%, or 99%. In a particular embodiment, the esters contained in the lubricating and / or cooling composition to be treated are bio-based esters. The bio-based ester content may be between 50% and 100% by weight relative to the total weight of esters contained in the lubricating and / or cooling composition to be treated. The bio-based esters may be triglycerides of vegetable origin or prepared from polyols and natural fatty acids. The bio-based carbon content of the esters contained in the lubricating and / or cooling composition to be treated may be greater than or equal to 50%, 60%, 70%, 80%, 90%, 95%, or 99%, according to ASTM D6866-22. The biologically sourced carbon content of the esters contained in the lubricant and / or coolant composition to be treated can be between 50 and 100%, according to ASTM D6866-22.

[0029] By "free organic acids" we mean any organic acid having at least one carboxylic acid COOH function, or any organophosphorus acid, for example of formula (Ra) x P(O)(OH) y Let x be equal to 0, 1, or 2, y be equal to 1, 2, or 3, x + y = 3, and Ra be any organic group. The free organic acid is not esterified, the carboxylic acid (COOH) function(s) is / are free, and the organophosphorus acid comprises at least one free (OH) group. Free carboxylic acids may be free aliphatic acids, which may consist of a hydrocarbon chain preferably having 3 to 36 carbon atoms and one or more acidic functional groups, for example, one or two acidic groups. Aliphatic acids include fatty acids. Free organic acids in the compositions may result from the degradation of the lubricating and / or cooling composition during its use.

[0030] The term "fatty acids" refers to a monocarboxylic acid with an aliphatic chain, having, for example, 4 to 36 carbon atoms, or 4 to 28 carbon atoms, or 6 to 30 carbon atoms. This term encompasses both saturated and unsaturated fatty acids. An example of a fatty acid ester is 2-ethylhexyl laurate.

[0031] Unsaturated fatty acid polyesters can comprise between 4 and 6 acid units.

[0032] The ester content in the lubricating and / or cooling composition to be treated is at least 0.1% by weight relative to the total weight of the composition, preferably between 0.5% and 99%. In one embodiment, the ester content is between 1% and 40%, preferably between 2% and 35%, and more preferably between 3% and 30%. In another embodiment, the ester content is at least 5% by weight relative to the total weight of the composition. For example, it may be between 5% and 20%.

[0033] According to one embodiment, the ester content is between 60 and 99% by weight relative to the total weight of the composition, preferably between 70 and 98%, and preferably between 80 and 95%.

[0034] The lubricating and / or cooling composition to be treated comprises at least one free organic acid, for example at least 0.001% free organic acid by weight of the total composition, preferably at least 0.1% and preferably between 0.1% and 3%. The composition lubricating and / or cooling to be treated may include, for example, between 0.5 and 2.5% or between 1 and 2% of free organic acid.

[0035] The lubricating and / or cooling compositions to be treated may also include one or more base oils conventionally used in the field of lubricants, such as mineral, synthetic or natural, animal or vegetable oils or mixtures thereof.

[0036] It can be a mixture of several base oils, for example a mixture of two, three, or four base oils.

[0037] These base oils can be in particular oils of mineral or synthetic origin belonging to groups I to V according to the classes defined in the API classification (or their equivalents according to the ATIEL classification) and presented in the following table or their mixtures.

[0038] [Table 1]

[0039] In particular, the lubricating and / or cooling composition to be treated may include at least 30% by weight of base oil(s) relative to its total weight, in particular at least 50% by weight of base oil(s), and more particularly between 60 and 99% by weight of base oil(s).

[0040] The lubricating and / or cooling composition to be treated may include one or more base oils from API classification groups I, II, III and / or IV, in particular groups II and / or III.

[0041] Advantageously, the lubricating and / or cooling oil to be treated comprises at least 30% by weight of at least one base oil of mineral or synthetic origin belonging to API Groups I to IV, preferably at least 50% or 60%. In one embodiment, the lubricating and / or cooling oil to be treated comprises between 55% and 95% by weight of at least one base oil of mineral or synthetic origin belonging to groups I to IV of the API classification, preferably between 60 and 93%, and preferably between 65 and 90%.

[0042] According to one embodiment, the lubricating and / or cooling composition to be treated is a used lubricating and / or cooling composition.

[0043] According to a particular embodiment, the lubricating and / or cooling composition to be treated is a used composition that has been used for the lubrication of a motorization system, in particular "mobile", i.e. including light vehicles, heavy goods vehicles, mobile machines known as "off road", or marine vehicles.

[0044] According to another particular embodiment, the lubricating and / or cooling composition to be treated is a used composition that has been used for the lubrication of a so-called industrial system, in particular "stationary", that is to say including, without limitation, turbines, compressors, hydraulic systems, gears, or even forming or cutting machines.

[0045] The lubricating and / or cooling composition to be treated may contain various conventional additives in the field of lubricants, such as friction modifiers, extreme pressure additives, anti-wear additives, detergents, antioxidants, viscosity index (VI) improvers, pour point depressants (PPD) additives, dispersing agents, anti-foaming agents, thickeners, and mixtures thereof.

[0046] As previously mentioned, the properties of the used lubricating and / or cooling composition are degraded due to its use, for a more or less long period, for the lubrication of a mechanical system, in particular a motorization system, such as a combustion engine.

[0047] Due to their origin, used lubricating and / or cooling compositions may contain one or more of the additives described above and impurities resulting from the degradation of additives originally present in the lubricant, or resulting from the wear of moving mechanical parts. Processing method

[0048] The process for treating a lubricating and / or cooling composition comprising at least one ester and at least one free organic acid, includes at least one step of treating said composition with at least one base having a pKb between 2 and 6.

[0049] The pKb of the base can be between 2 and 6, or between 2.5 and 5.5, or between 3 and 5, or between 3.5 and 4.5.

[0050] According to one embodiment, the base is chosen from alkali carbonates, alkali bicarbonates, alkali metal phosphates, phenol salts, tertiary amines, and mixtures thereof. NasPC is an example of an alkali metal phosphate. Sodium phenate is an example of a phenol salt. Preferably, the base is chosen from carbonates and bicarbonates, and preferably from the group consisting of... Sodium carbonate, potassium carbonate, cesium carbonate, rubidium carbonate, potassium bicarbonate, calcium carbonate, sodium bicarbonate, and mixtures thereof. Preferably, the base is sodium carbonate.

[0051] Preferably, the base is a non-nucleophilic base, which helps avoid transesterification reactions. The base can be in solid form or in aqueous solution.

[0052] According to one embodiment, the amount of base used is between 2 and 40% by weight relative to the weight of the lubricating and / or cooling composition to be treated, preferably between 3 and 30%, and more preferably between 4 and 20%.

[0053] According to one embodiment, the process is carried out at a temperature between 0 and 200°C, preferably between 20 and 180°C, and more preferably between 60°C and 170°C. When the temperature is above 100°C, the composition can be heated first to 100°C, which can allow the water in the composition to evaporate, and then heated to a temperature above 100°C.

[0054] According to one embodiment, the process is carried out at ambient pressure.

[0055] According to one embodiment, the treatment process is a process for treating a used lubricating and / or cooling composition comprising: - at least one ester, preferably with a bio-based ester content between 50 and 100% by weight relative to the total weight of esters contained in the used lubricating and / or cooling composition, - at least one free organic acid, and - at least 30% by weight of at least one base oil of mineral or synthetic origin belonging to groups I to IV, said process comprising a step of treating said composition with at least one base having a pKb between 2 and 6.

[0056] This process neutralizes free acids present in used lubricants containing esters and mineral or synthetic base oils without causing saponification of the esters. This allows for the re-refining and recycling of used lubricating oils containing esters and mineral or synthetic base oils using existing processes.

[0057] According to one embodiment, the process includes at least one step b) of treatment of the lubricating and / or cooling composition obtained after treatment with the base (step a)), selected from dehydration, distillation, filtration, hydrogenation, liquid / liquid extraction, decantation, passage over an adsorbent material and transesterification, preferably as detailed below.

[0058] According to one embodiment, the treatment process is a recycling process for a used lubricating and / or cooling composition. The recycling process may include at least one step (b) of treating the used lubricating and / or cooling composition obtained after treatment with the base (step (a)), selected from dehydration, distillation, the filtration, hydrogenation, liquid / liquid extraction, decantation, passage through an adsorbent material and transesterification, preferably as detailed below.

[0059] According to one embodiment, the process includes at least one dehydration step of the lubricating and / or cooling composition obtained in step a). This dehydration step allows the removal of any water present in the lubricating and / or cooling composition obtained after treatment.

[0060] This dehydration can be carried out by any method known to a person skilled in the art, for example by distillation, decantation, heating or passing a stream of hot air through the lubricating composition and / or cooling obtained after treatment.

[0061] According to one embodiment, the dehydration step can be carried out at a temperature between 50 °C and 250 °C, preferably between 100 °C and 200 °C. In particular, it can be carried out at a pressure between 50,000 and 150,000 Pa, preferably at atmospheric pressure.

[0062] In one embodiment, the process includes at least one step of filtering the resulting lubricating and / or cooling composition. This filtration can be carried out by any method known to those skilled in the art. This filtration step may be a particulate or non-particulate filtration step. For example, it can be carried out using diatomaceous earth systems.

[0063] In one embodiment, the process includes at least one additional step of distilling the resulting lubricating composition and / or cooling it. This distillation step(s) may be carried out using any technique known to those skilled in the art. For example, atmospheric distillation or distillation under reduced pressure may be performed. Distillations may, for instance, be carried out at a temperature between 100 °C and 500 °C, preferably between 200 °C and 400 °C, and more preferably between 300 °C and 380 °C. In particular, they may be carried out at a pressure between 25 and 2,000 Pa, preferably between 50 and 1,000 Pa, and more particularly between 50 and 250 Pa.

[0064] According to one embodiment, the process includes at least one step of passing the lubricating and / or cooling composition obtained after treatment onto an adsorbent material.

[0065] The adsorbent material advantageously allows for the selective adsorption of aromatic compounds, in particular polycyclic aromatic hydrocarbons (PAHs).

[0066] In particular, passing over an adsorbent material, preferably activated carbon, advantageously reduces the content of polycyclic aromatic hydrocarbons (PAHs), notably chosen from chrysene, benzo[b]fluoranthene, benzo[j]fluoranthene, benzo[k]fluoranthene, benzo[e]pyrene, benzo[a]pyrene, dibenz[a,h]anthracene and / or benz[a]anthracene, of the lubricating and / or cooling composition obtained after treatment.

[0067] The term "passage of the composition over an adsorbent material" refers to the flow of the composition over the adsorbent support.

[0068] Examples of adsorbent materials include activated carbon, zeolites, clays, and functionalized porous compounds. Activated carbon is preferred.

[0069] In the case of passing the lubricating and / or cooling composition obtained after treatment over activated carbon, the quantity of activated carbon used is preferably between 0.5 and 60 g of activated carbon per litre of composition, preferably between 0.5 and 50 g / l, preferably from 1 to 50 g / l, preferably between 1 and 30 g / l, for example between 5 and 60 g / l, preferably between 5 and 50 g / l.

[0070] The flow rate of the lubricating and / or cooling composition obtained after treatment can be between 1 m 3 / h and 15 m 3 / h, for example between 5 and 10m 3 / h.

[0071] Preferably, activated carbon is characterized by a density between 200 and 500 kg / m³ 3 , for example measured according to the ASTDM D2854 standard.

[0072] Preferably, activated carbon is coal-based carbon, preferably comprising 70 to 95%, advantageously 80 to 90% by weight of carbon.

[0073] The step of passing the lubricating and / or cooling composition obtained after treatment onto an adsorbent support, preferably activated carbon, may be preceded by the following preliminary steps: - one or more distillation stages; and - a filtration step, in particular as defined previously.

[0074] In one embodiment, the process includes at least one hydrogenation (or hydrotreating) step of the lubricating and / or cooling composition obtained in step a), preferably following a prior dehydration and / or distillation step. This hydrogenation step(s) may be carried out by any technique known to those skilled in the art and generally consist of treating the lubricating oil with hydrogen, usually in the presence of a hydrotreating catalyst. Such a catalyst may contain, for example, at least one oxide or sulfide of at least one Group VI metal and / or at least one Group VIII metal, such as molybdenum, tungsten, nickel, or cobalt, and a support, for example, alumina, silica-alumina, or a zeolite.

[0075] According to one embodiment, the process includes at least one liquid / liquid solvent extraction step of the lubricating and / or cooling composition obtained in step a), preferably following a prior dehydration and / or distillation step.

[0076] In particular, liquid-liquid extraction with a solvent is advantageous for clarifying dark-colored used lubricants and / or coolants, and for removing at least some of the unpleasant odor or aromatic compounds, especially polycyclic aromatic hydrocarbons (PAHs). These extraction steps can be carried out using any technique known to those skilled in the art. The extraction is generally performed in a mixer-settler or in an extraction column, using a suitable extraction solvent.

[0077] According to one embodiment, the process includes at least one step of decanting the lubricating composition and / or cooling obtained in step a). The said decanting step(s) may be carried out by any technique known to a person skilled in the art.

[0078] According to one embodiment, the process includes at least one transesterification step (step b)) comprising contacting said lubricating and / or cooling composition obtained in step a) with at least one monoalcohol comprising n carbon atoms, with n < m, and a catalyst. This transesterification step is preferably followed by a distillation step enabling the separation of the esters comprising an alcohol group comprising n carbon atoms obtained in step b) from the remainder of the lubricating and / or cooling composition.

[0079] Transesterification allows the esters present in the lubricating composition to be transformed into an ester with a short-chain "-OR" alcohol part; it is then possible to distill them to separate them from the rest of the lubricating and / or cooling composition, because their boiling point is lower.

[0080] Transesterification is a well-known reaction. It allows the exchange of the alcohol residue (-OR) of an ester for another alcohol residue (-OR). In this case, it allows the exchange of the alcohol residue (-OR) of an ester contained in the composition to be treated for another alcohol residue (-OR) with a shorter chain. Indeed, the ester contained in the lubricant and / or coolant composition to be treated comprises an alcohol residue (-OR) with a carbon atom length, and the ester obtained after transesterification has an alcohol residue (-OR) with an carbon atom length, where n is an integer and n < m. The ester obtained after transesterification therefore has an alcohol residue with a shorter chain.

[0081] This reaction is catalyzed by an acidic or basic catalyst. Preferably, the catalyst is basic, preferably chosen from the alkoxides.

[0082] Examples of acid catalysts include: - Brønsted acids, such as H2SO4, H3PO4, HCl, methansulfonic acid, or para-toluenesulfonic acid, and - Lewis acids, such as AICh, BCh, FeCh, ZnCh, and zeolites. Acid catalysts can be homogeneous or heterogeneous.

[0083] Examples of basic catalysts include: - bases such as NaOH, LiOH or KOH - alcoholates, - basic oxides such as ZnO, MgO and CaO, - zinc aluminates.

[0084] Advantageously, the catalyst is an alkoxide, preferably chosen from among the methanolates and ethoxides. Examples of alkoxides include methyl, ethyl, and propyl alkoxides. In a particular embodiment, the catalyst is chosen from sodium methoxide, potassium methoxide, sodium ethoxide, potassium ethoxide, and mixtures thereof. Basic catalysts may be homogeneous or heterogeneous.

[0085] The amount of catalyst can be between 0.01 and 10% by weight, relative to the weight of the composition to be treated, preferably between 0.1 and 5%.

[0086] The alcohol used in the transesterification step is a monoalcohol comprising n carbon atoms, with n < m. Advantageously, the alcohol is methanol or ethanol. The amount of alcohol used may be between 1 and 50 molar equivalents relative to the amount of esters in the composition to be treated, preferably between 5 and 20 equivalents.

[0087] Transesterification is preferably carried out in an anhydrous medium. An anhydrous medium is defined as a composition containing less than 0.05% water. The reaction can be performed under nitrogen or argon.

[0088] In one embodiment, the lubricating and / or cooling composition to be treated by transesterification contains at least 0.05% water. In this case, the process may include, prior to the transesterification step, a heating / dehydration step to obtain a water content of less than 0.05% in the lubricating and / or cooling composition to be treated. This dehydration step may be carried out at a temperature between 50 °C and 250 °C, preferably between 100 °C and 200 °C. It is preferably carried out at atmospheric pressure.

[0089] Transesterification can be carried out at a temperature between 20 and 150°C, preferably between 40°C and 100°C.

[0090] Transesterification can be followed by a distillation step to separate the esters containing an alcohol group with n carbon atoms obtained in step b) from the remainder of the lubricating and / or cooling composition. This distillation can be carried out using any technique known to those skilled in the art. For example, it could be atmospheric distillation or distillation under reduced pressure. Distillations can be performed at temperatures between 100 °C and 500 °C, preferably between 200 °C and 400 °C, and more preferably between 300 °C and 380 °C. In particular, they can be carried out at pressures between 25 and 2,000 Pa, preferably between 50 and 1,000 Pa, and more particularly between 50 and 250 Pa. Lubricating and / or cooling composition obtained

[0091] The lubricating and / or cooling composition obtained after step a) is free of free organic acids. For example, the lubricating and / or cooling composition obtained after step a) may contain less than 0.1% free organic acids, or less than 0.01% free organic acids, or less than 0.001% free organic acids.

[0092] In the case where the process includes a transesterification step (b), the lubricating and / or cooling composition obtained after transesterification and a distillation step is free of esters and free organic acids. For example, the lubricating and / or cooling composition obtained after transesterification and a distillation step may contain less than 0.5% ester, or less than 0.1% ester, or less than 0.01% ester. The lubricating and / or cooling composition obtained after transesterification and a distillation step may also include less than 0.1% free organic acids, or less than 0.01% free organic acids, or less than 0.001% free organic acids.

[0093] In some cases, the composition obtained is characterized by a high silicon content, in particular strictly greater than 2 ppm, in particular greater than or equal to 5 ppm, more particularly greater than or equal to 10 ppm, in particular greater than or equal to 15 ppm, for example greater than or equal to 20 ppm, in particular up to 300 ppm, in particular up to 290 ppm, for example up to 285 ppm.

[0094] It can also be characterized by a high content of one or more elements chosen from chlorine, oxygen, and nitrogen. For example, it may have a chlorine content of at least 5 ppm, in particular at least 10 ppm, especially greater than or equal to 20 ppm, and in particular greater than or equal to 30 ppm.

[0095] Chlorine content can, for example, be assessed by any method known to a person skilled in the art, for example by X-ray fluorescence (XRF).

[0096] This disclosure also relates to the use of the process to improve the eco-performance of lubricating and / or cooling compositions comprising esters, the eco-performance preferably being characterized by: - minimizing the carbon footprint of lubricating and / or cooling compositions containing esters, - improving the recyclability of lubricating and / or cooling compositions containing esters, - the increase in the content of bio-based compounds in lubricating and / or cooling compositions, and / or - a decrease in the use of fossil resources.

[0097] Examples

[0098] Products used: - H1: Base oil - H2: Used lubricating oil - Myristic acid - HOSO: sunflower oil rich in oleic acid - TMPTO: trimethylpropane trioleate - POE: neopolyol ester - Na2CO3 in aqueous solution at 20% w / w - NaOH in aqueous solution at 30% w / w

[0099] Example 1

[0100] Protocol: The mixture is heated to 60°C, then the basic solution is added. The solution is heated to 90°C for 15 to 30 minutes, then cooled to 30°C. If the mixture has not thickened during neutralization, it is diluted in heptane and then filtered. The filtrate and the solid are collected. where applicable, samples are recovered for analysis. The initial mixture, the filtrate, and the purified solid are analyzed by IR spectroscopy and GC-FID.

[0101] [Table 2]

[0102] These results show that regardless of the base oil, acid content, ester, and ester content, no thickening problems are observed when the base is a weak base, Na₂CO₃. Furthermore, GC-FID analyses demonstrate that only myristic acid is present; therefore, there is no transesterification reaction. Comparative example 1, on the other hand, shows that treatment with sodium hydroxide, under the same conditions, leads to thickening problems.

[0103] Example 2

[0104] Other compositions including a high % of ester were also tested to show that it was possible to treat feeds containing high ester levels with sodium carbonate.

[0105] Protocol at 90°C: 50g of the mixture is heated to 60°C, then the basic solution is added (40g of 20% w / w Na2CO3 solution or 2.5g of 30% w / w NaOH solution). The solution is then heated to 90°C for 15 to 30 minutes and then cooled to 30°C.

[0106] Protocol at 160°C: 50g of the mixture is heated to 60°C, then the basic solution is added (40g of 20% w / w Na2CO3 solution or 2.5g of 30% w / w NaOH solution). The solution is heated to 100°C until all the water in the mixture has evaporated. Then it is heated to 160°C for 15 to 30 minutes. Finally, it is cooled to 30°C.

[0107] [Table 3]

[0108] These results show that increasing the ester content does not cause any thickening problems, whether at 90°C or 160°C, when the base is a weak base, Na2CC>3. Comparative example 2 shows, on the contrary, that treatment with sodium hydroxide, even from 20% ester, leads to thickening problems.

Claims

Demands

1. A process for treating a lubricating and / or cooling composition comprising at least one ester and at least one free organic acid, said process comprising a step of treating said composition with at least one base having a pKb between 2 and 6.

2. A process according to claim 1 characterized in that the base is selected from carbonates and bicarbonates, preferably from sodium carbonate, potassium carbonate, cesium carbonate, rubidium carbonate, potassium bicarbonate, calcium carbonate, sodium bicarbonate, and mixtures thereof, and more preferably, the base is sodium carbonate.

3. A process according to any one of the preceding claims characterized in that the amount of base used is between 2 and 40% by weight relative to the weight of the lubricating and / or cooling composition to be treated.

4. A process according to any one of the preceding claims characterized in that the process is carried out at a temperature between 20 and 180°C, preferably between 60°C and 170°C.

5. A process according to any one of the preceding claims characterized in that the lubricating and / or cooling composition to be treated comprises at least 0.001% of free organic acid relative to the total weight of the composition, preferably at least 0.1% and preferably between 0.1% and 3%.

6. A method according to any one of the preceding claims, characterized in that the esters contained in the lubricating and / or cooling composition to be treated are selected from - aliphatic acid esters, where the aliphatic acid residue comprises a hydrocarbon chain having, preferably, from 3 to 36 carbon atoms and one or two acid functions. - polyol esters, preferably glycerol, trimethylolpropane or neopentyl glycol esters, - unsaturated fatty acid polyesters containing up to 6 acid units, and - their mixtures.

7. A process according to any one of the preceding claims characterized in that the ester content contained in the lubricating and / or cooling composition to be treated is at least 0.1% by weight relative to the total weight of the composition, preferably the ester content is between 0.5 and 99%, preferably between 1 and 40%, and more preferably between 3 and 30%.

8. A process according to any one of the preceding claims, characterized in that the lubricating and / or cooling oil to be treated comprises at least 30% by weight of at least one base oil of mineral or synthetic origin belonging to groups I to IV, preferably at least

9. A method according to any one of the preceding claims characterized in that the lubricating and / or cooling composition to be treated is a used lubricating and / or cooling composition.

10. A process according to any one of the preceding claims characterized in that it comprises at least one treatment step of the lubricating oil obtained after treatment selected from dehydration, distillation, filtration, liquid / liquid extraction, decantation, passage over an adsorbent material and transesterification.

11. Use of the process according to any one of the preceding claims to improve the eco-performance of lubricating and / or cooling compositions comprising esters, the eco-performance preferably being characterized by: - minimizing the carbon footprint of lubricating and / or cooling compositions containing esters, - improving the recyclability of lubricating and / or cooling compositions containing esters, - increasing the content of bio-based compounds in lubricating and / or cooling compositions, and / or - a decrease in the use of fossil resources.

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