WO2025109048A1 - Method for treating waste lubricating oils comprising esters - Google Patents

Abstract

The present application relates to the field of treatments for 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 their recyclability.

Description

Process for treating used lubricating oils comprising esters

Technical field

[0001] The present disclosure relates to the field of treatment of used lubricating and/or cooling compositions. In particular, the present disclosure relates to a method of treatment of used lubricating and/or cooling compositions comprising esters, in order to improve their recyclability.

Prior art

[0002] Lubricating compositions, more simply called "lubricants", are commonly used in mechanical systems for the main purposes of reducing friction forces between the various moving metal parts and to prevent premature wear or even damage to these parts, in particular their surface. For example, they are used in various mechanical systems of vehicles, including the engine, the transmission or even the hydraulic circuit.

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

[0004] These various undesirable elements are likely to negatively impact the properties of the lubricating composition which thus becomes, after use, a so-called “used”, “worn out” or even “degraded” lubricating composition. This is why lubricating compositions need to be replaced after a certain period of use.

[0005] In consideration of current issues of environmental protection and resource conservation, methods have been developed to re-refine, recycle or recondition used lubricating compositions. This makes it possible to regenerate used lubricating oils which can then be reused for the formulation of new lubricating compositions.

[0006] Furthermore, still in an approach of optimizing resources and reducing the carbon footprint of lubricants, more and more lubricating compositions include bio-sourced compounds such as triglycerides of plant origin, or even esters of polyols and natural fatty acids. The content of bio-sourced compounds in lubricating compositions, and in particular esters, is increasing from year to year.

[0007] Nevertheless, the presence of esters in lubricating compositions causes problems during the re-refining or recycling stages of used lubricating compositions. Indeed, these processes include in particular a stage of treating used lubricating oils with soda to neutralize the free acids formed that are likely to corrode the recycling facility. The soda then reacts with the esters present, resulting in the formation of solid soaps, which risk clogging the process lines. These problems are such that as soon as a used lubricating oil has an ester content greater than or equal to 5%, it is not possible to regenerate it with 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 comprising esters so that they can be recycled and re-refined using existing processes.

Summary

[0009] The present disclosure proposes to treat used lubricating oils comprising esters with a method comprising (a) a step of transesterification with a short-chain alcohol in order to obtain esters having a short-chain -OR” group, and (b) a step of distillation of the esters obtained in step a).

[0010] The present disclosure relates to a method for treating a lubricating and/or cooling composition comprising at least one ester, said ester comprising an alcohol residue and at least one acid residue, wherein said alcohol residue comprises m carbon atoms and one or more alcohol functions, said method comprising at least the following steps: a) A transesterification step comprising bringing said lubricating and/or cooling composition into contact with at least one monoalcohol comprising n carbon atoms, with n < m, and a catalyst; and b) A distillation step for separating the esters comprising an alcohol group comprising n carbon atoms obtained in step a) from the remainder of the lubricating and/or cooling composition.

[0011] Step a) of the process makes it possible to transform the esters present in the lubricating composition into an ester having a short-chain alcohol part -OR having n carbon atoms, and an acid part R'-C(O)-, in particular a fatty acid part. It is for example possible to use methanol or ethanol in order to obtain fatty acid methyl esters (or EMAG) or fatty acid ethyl esters.

[0012] Step b) makes it possible to separate the ester fraction obtained from the used lubricating composition. It is then possible to re-refine and recycle the latter according to existing processes implementing a soda treatment step. Indeed, as it no longer contains ester, there is no longer any problem of formation of solid soaps during the soda treatment.

[0013] Furthermore, the ester fraction obtained can also be recovered, in particular when it comprises fatty acid methyl esters or fatty acid ethyl esters, since these compounds can be used as biofuel. The process of the present invention thus has a double advantage and makes it possible to recover the various products obtained. [0014] This process also makes it possible to increase the content of bio-sourced esters in lubricating compositions, because it is then possible to re-refine and recycle used lubricating oils regardless of their ester content. This makes it possible to avoid the incineration of used lubricating oils, to increase the proportion of used lubricating oils that is recycled, and to improve the carbon footprint of these lubricating oils.

Detailed description

[0015] As specified above, the present disclosure relates to a method for treating a lubricating and/or cooling composition comprising at least one ester, said ester comprising an alcohol residue and at least one acid residue, wherein said alcohol residue comprises m carbon atoms and one or more alcohol functions, said method comprising at least the following steps: a) A transesterification step comprising bringing said lubricating and/or cooling composition into contact with at least one monoalcohol comprising n carbon atoms, with n < m, and a catalyst; and b) A distillation step for separating the esters comprising an alcohol group, comprising n carbon atoms, obtained in step a) from the remainder of the lubricating and/or cooling composition.

[0016] The expressions “between ... and ...”, “ranging from ... to ...”, “formed from ... to ...”, and “varying from ... to ...”, must be understood inclusively, unless otherwise stated.

[0017] In the description and the examples, unless otherwise indicated, the percentages are mass percentages. The percentages are therefore expressed in mass relative to the total mass of the composition.

Lubricating and/or cooling composition to be treated

[0018] The composition to be treated is a lubricating and/or cooling composition.

[0019] According to the invention, the term “lubricating composition” (or more simply “lubricant” or “lubricating oil”) is intended to denote any composition that can be used for the lubrication of moving parts, in particular metal parts, of a mechanical system, such as bearings, gears or motors. A “used lubricating composition” (or more simply “used lubricant” or “used oil”) denotes a composition that has been used for this purpose.

[0020] The lubricating composition to be treated is generally a used lubricating composition; it may come from different sources. In particular, as detailed in the rest of the text, it may be a lubricant used for the lubrication of a motorization system, in particular a “mobile” system, or for the lubrication of a so-called industrial system, in particular a “stationary” system.

[0021] It is understood that the lubricating composition to be treated may be a mixture of several lubricating compositions, in particular used ones, coming from the same source or from several different sources. [0022] Due to their origin, used lubricants, in particular engine lubricants, include a number of degradation products derived from the oil itself or from the additives it contains, as well as metal particles, metal oxides and other elements, for example from the engine. A used oil may contain in particular a high content of undesirable elements, for example calcium (Ca), iron (Fe), magnesium (Mg), sodium (Na), nickel (Ni), phosphorus (P), silicon (Si), chlorine (Cl), zinc (Zn) etc.

[0023] By “cooling composition” is meant a composition that can be used as a cooling fluid for moving parts in a mechanical system, or for stationary parts such as data centers or charging stations. It can in particular be used to cool the power electronics and/or the rotor and/or the stator of an electric motor or to cool the battery present in an electric or hybrid vehicle. A “used cooling composition” means a composition that has been used for this purpose.

[0024] According to one embodiment, the composition to be treated is both a lubricating and cooling composition. Indeed, the friction between the moving parts in a mechanical system generates heat, and it may be necessary to jointly ensure cooling of the mechanical systems and their lubrication. The composition to be treated then has a dual function and the composition to be treated may ensure, or have ensured, the lubrication and cooling of the moving parts in a mechanical system, in particular in a mobile or stationary motorization system, more particularly in a vehicle propulsion system, for example in a propulsion system of an electric or hybrid vehicle.

[0025] The lubricating and/or cooling composition to be treated comprises at least one ester. The ester has the general formula R'-C(O)-O-R, with an acid part or acid residue of formula R'-C(O)-, and an alcohol part or alcohol residue of formula -O-R comprising m carbon atoms and one or more alcohol functions. The number of carbon atoms m is an integer, for example between 3 and 20, or between 4 and 10. The alcohol residue of formula -O-R comprises one or more alcohol functions. When the alcohol residue of formula -O-R comprises several alcohol functions, it is a polyol. It may for example comprise between 1 and 5 alcohol functions. According to 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.

[0026] Indeed, the lubricating and/or cooling compositions to be treated generally comprise esters having a long-chain alcohol part (for example at least 3 carbon atoms, or at least 4 carbon atoms) and/or esters having an alcohol part which is a polyol, such as glycerol, trimethylol propane or neopentyl glycol. The boiling point of these esters is then very high, and it is then very difficult to separate them from the rest of the composition to be treated by fractional distillation. The present process makes it possible to transform the esters present in the composition to be treated into an ester having a short-chain alcohol part -OR”. It is then possible to easily distill the esters obtained, because their boiling point is lower. [0027] When the composition to be treated comprises esters having an alcohol residue comprising m carbon atoms, the alcohol residue is of 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 may be linear or branched, and it may be substituted or not. It may have between 4 and 30 carbon atoms, for example between 5 and 22 carbon atoms.

[0028] When the composition to be treated comprises esters having an alcohol residue which is a polyol residue, the alcohol residue is of formula -O-R, where R represents a polyol residue. R then represents a carbon chain comprising at least one other alcohol function, for example between 1 and 4 additional alcohol functions. The carbon chain R comprises at least 2 carbon atoms. The carbon chain may be linear or branched, and it may be substituted or not. It may have between 2 and 10 carbon atoms, for example between 2 and 5 carbon atoms. The other alcohol functions of the polyol may be in the free -OH form, or not. They may, for example, also be in ester form, which is particularly the case for triglycerides, when the alcohol part is a glycerol.

[0029] According to one embodiment, the esters contained in the lubricating and/or cooling composition to be treated are chosen from

- aliphatic acid esters, where the aliphatic acid residue comprises a hydrocarbon chain preferably having from 3 to 36 carbon atoms and one or two acid functions,

- polyol esters, preferably glycerol, trimethylolpropane or neopentyl glycol esters,

- polyesters of unsaturated fatty acids containing up to 6 acid units, and

- their mixtures.

[0030] By "aliphatic acids" is meant an aliphatic acid comprising a hydrocarbon chain preferably having from 3 to 36 carbon atoms, and one or more acid functions, for example one or two acid functions. Aliphatic acids include fatty acids.

[0031] By "fatty acids" is meant a monocarboxylic acid with an aliphatic chain having, for example, from 4 to 36 carbon atoms, or from 4 to 28 carbon atoms, or from 6 to 30 carbon atoms. This term includes saturated and unsaturated fatty acids. Among the fatty acid esters, mention may be made of 2-ethylhexyl laurate.

[0032] Unsaturated fatty acid polyesters may comprise between 4 and 6 acid units.

[0033] The content of esters 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 between 0.5 and 99%. According to one embodiment, the ester content is between 1 and 40%, preferably between 2 and 35% and more preferably between 3 and 30%. According to one embodiment, the ester content is at least 5% by weight relative to the total weight of the composition. It may for example be between 5 and 20%. [0034] 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 preferentially between 80 and 95%.

[0035] The lubricating and/or cooling composition to be treated may also comprise at least one free aliphatic acid, for example at least 0.001% of free aliphatic acid, preferably between 0.001 and 5% of free aliphatic acid.

[0036] By “free aliphatic acid” is meant an aliphatic acid which is not esterified, of which the carboxylic acid function(s) COOH is (are) free, or a corresponding salt.

[0037] The lubricating and/or cooling compositions to be treated may also comprise one or more base oils conventionally used in the field of lubricants, such as mineral, synthetic or natural, animal or vegetable oils or their mixtures.

[0038] It may be a mixture of several base oils, for example a mixture of two, three, or four base oils.

[0039] These base oils may in particular be 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.

[0040] [Table 1]

[0041] In particular, the lubricating and/or cooling composition to be treated may comprise at least 50% by weight of base oil(s) relative to its total weight, in particular at least 60% by weight of base oil(s), and more particularly between 60 and 99% by weight of base oil(s). [0042] The lubricating and/or cooling composition to be treated may comprise one or more base oils of groups I, II, III and/or IV of the API classification, in particular groups II and/or III.

[0043] Advantageously, the lubricating and/or cooling oil to be treated comprises at least 50% by weight of at least one base oil of mineral or synthetic origin belonging to groups I to IV of the API classification, preferably at least 60%. According to 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 preferentially between 65 and 90%.

[0044] According to one embodiment, the lubricating and/or cooling composition to be treated is a used lubricating and/or cooling composition

[0045] According to a particular embodiment, the lubricating and/or cooling composition to be treated is a used composition having been used for the lubrication of a motorization system, in particular “mobile”, that is to say including light vehicles, heavy goods vehicles, so-called “off-road” mobile machines, or even marine vehicles.

[0046] According to another particular embodiment, the lubricating and/or cooling composition to be treated is a used composition having been used for the lubrication of a so-called industrial system, in particular “stationary”, that is to say including, in a non-limiting manner, turbines, compressors, hydraulic systems, gears, or even forming or cutting machines.

[0047] The lubricating and/or cooling composition to be treated may contain various conventional additives in the field of lubricants, such as friction modifying additives, extreme pressure additives, anti-wear additives, detergents, antioxidants, viscosity index (VI) improvers, pour point depressant (PPD) additives, dispersing agents, anti-foaming agents, thickeners, and mixtures thereof.

[0048] As already mentioned previously, 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.

[0049] Due to their origin, used lubricating and/or cooling compositions may thus contain one or more 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.

Treatment process

[0050] The treatment method comprises at least the following steps: a) A transesterification step comprising bringing said lubricating and/or cooling composition into contact with at least one monoalcohol comprising n carbon atoms, with n < m, and a catalyst; and b) A distillation step making it possible to separate the esters comprising an alcohol group comprising n carbon atoms obtained in step a) from the rest of the lubricating and/or cooling composition.

[0051] Step a) makes it possible to transform the esters present in the lubricating composition into esters having a short-chain alcohol part -OR”, it is then possible to distill them in step b) to separate them from the rest of the lubricating and/or cooling composition, because their boiling point is lower.

[0052] Transesterification is a well-known reaction. It allows the alcohol residue -OR of an ester to be exchanged for another alcohol residue -OR”. In the present case, it allows the alcohol residue -OR of an ester contained in the composition to be treated to be exchanged for another alcohol residue -OR”, with a shorter chain. Indeed, the ester contained in the lubricating and/or cooling composition to be treated comprises an alcohol residue -OR with m carbon atoms and the ester obtained after transesterification has an alcohol residue -OR” with n carbon atoms, n being an integer and n < m. The ester obtained after transesterification therefore has an alcohol residue with a shorter chain.

[0053] This reaction is catalyzed by an acid or basic catalyst. Preferably, the catalyst is basic, preferably chosen from alcoholates.

[0054] Among the acid catalysts, we can cite

- Bronsted acids, such as H2SO4, H3PO4, HCl, methanesulfonic acid, or paratoluenesulfonic acid, and

- Lewis acids, such as AICh, BCh, FeCh, ZnCL, and zeolites.

Acid catalysts can be homogeneous or heterogeneous.

[0055] Among the basic catalysts, we can cite

- bases such as NaOH, LiOH or KOH,

- alcoholates,

- basic oxides such as ZnO, MgO and CaO,

- zinc aluminates.

[0056] Advantageously, the catalyst is an alcoholate, preferably chosen from methanolates and ethanolates. Among the alcoholates, mention may be made of methyl, ethyl, and propyl alcoholates. According to a particular embodiment, the catalyst is chosen from sodium methanolate, potassium methanolate, sodium ethanolate, potassium ethanolate, and mixtures thereof. The basic catalysts may be homogeneous or heterogeneous.

[0057] The amount of catalyst may be between 0.01 and 10% by weight, relative to the weight of the composition to be treated, preferably between 0.1 and 5%. [0058] The alcohol used in step a) is a monoalcohol comprising n carbon atoms, with n < m. Advantageously, the alcohol is methanol or ethanol. The quantity of alcohol used may be between 1 and 50 molar equivalents relative to the quantity of esters contained in the composition to be treated, preferably between 5 and 20 equivalents.

[0059] Step a) is preferably carried out in an anhydrous medium. By anhydrous medium is meant a composition which comprises less than 0.05% water. The reaction can be carried out under nitrogen or under argon.

[0060] According to one embodiment, the lubricating and/or cooling composition to be treated comprises at least 0.05% water. In this case, the method may comprise, before step a), a heating/dehydration step, so as 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 of between 50°C and 250°C, preferably between 100°C and 200°C. It is preferably carried out at atmospheric pressure.

[0061] Step a) can be carried out at a temperature between 20 and 150°C, preferably between 40°C and 100°C.

[0062] According to one embodiment, the lubricating and/or cooling composition to be treated comprises at least 1% of free aliphatic acid, and the method comprises, before step a), a step of esterification of the free aliphatic acids carried out with an alcohol and an acid catalyst.

[0063] Among the acid catalysts, we can cite

- Bronsted acids, such as H2SO4, H3PO4, HCl, methanesulfonic acid, or paratoluenesulfonic acid, and

- Lewis acids, such as AICh, BCh, FeCh, ZnCL, and zeolites.

Acid catalysts can be homogeneous or heterogeneous.

[0064] The amount of catalyst may be between 0.01 and 10% by weight, relative to the weight of the free aliphatic acids contained in the composition to be treated, preferably between 0.1 and 5%.

[0065] The alcohol used in this esterification step may be an alcohol as described above for transesterification step a). 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 free aliphatic acids contained in the composition to be treated, preferably between 5 and 20 equivalents.

[0066] In the case where the process comprises a dehydration step and an esterification step before step a), the dehydration step is preferably carried out before the esterification step.

[0067] Distillation step b) can be carried out by any technique known to those skilled in the art. This can be, for example, atmospheric distillation or distillation under reduced pressure. The distillations can, for example, be carried out at a temperature between 100°C and 500°C, preferably between 200°C and 400°C, more preferably between 300°C. and 380°C. In particular, they can be operated at a pressure of between 25 and 2,000 Pa, preferably between 50 and 1,000 Pa, more particularly between 50 and 250 Pa.

[0068] According to one embodiment, the method comprises at least one step c) of treatment of the lubricating and/or cooling composition obtained in step b) chosen from dehydration, distillation, filtration, hydrogenation, liquid/liquid extraction, decantation, and passage over an adsorbent material, preferably as detailed below.

[0069] According to one embodiment, the method comprises at least one step c) of treatment of the lubricating and/or cooling composition obtained in step b) chosen from treatment with a strong base, dehydration, distillation, filtration, hydrogenation, liquid/liquid extraction, decantation, and passage over an adsorbent material, preferably as detailed below.

[0070] According to one embodiment, the method comprises at least one step of treating the lubricating and/or cooling composition obtained in step b) with a strong base. This treatment may be a treatment which is commonly used in a standard process for recycling used lubricating compositions. This step is for example present in different recycling processes (J. Chem. Technol. Biotech 2013, 88, 1780-1793). It is notably described in documents WO94/21761 and EP0574272. The strong base used may be sodium hydroxide or potassium hydroxide. This step may be carried out at a temperature between 50°C and 250°C, preferably between 80°C and 200°C. The amount of base used may be between 0.1 and 1% by mass relative to the total mass of the lubricating and/or cooling composition obtained in step b).

[0071] According to one embodiment, the method comprises at least one step of dehydration of the lubricating and/or cooling composition obtained in step b). This dehydration step makes it possible to eliminate any water possibly present in the lubricating and/or cooling composition obtained in step b).

[0072] This dehydration can be carried out by any method known to those skilled in the art, for example by distillation, decantation, heating or passing a flow of hot air through the lubricating and/or cooling composition obtained in step b).

[0073] 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.

[0074] According to one embodiment, the method comprises at least one step of filtration of the lubricating and/or cooling composition obtained in step b). This filtration can be implemented by any method known to those skilled in the art. This filtration step can be a particulate or non-particulate filtration step. It can for example be implemented by diatomaceous earth type systems. [0075] According to one embodiment, the method comprises at least one additional step of distillation of the lubricating composition and/or cooling obtained in step b). Said distillation step(s) may be carried out by any technique known to those skilled in the art. It may be, for example, atmospheric distillation or distillation under reduced pressure. The distillations may, for example, be carried out at a temperature of between 100°C and 500°C, preferably between 200°C and 400°C, more preferably between 300°C and 380°C. In particular, they may be carried out at a pressure of between 25 and 2,000 Pa, preferably between 50 and 1,000 Pa, more particularly between 50 and 250 Pa.

[0076] According to one embodiment, the method comprises at least one step of passing the lubricating and/or cooling composition obtained in step b) over an adsorbent material.

[0077] The adsorbent material advantageously makes it possible to selectively adsorb aromatic compounds, in particular polycyclic aromatic hydrocarbons (PAHs).

[0078] In particular, passing over an adsorbent material, preferably over activated carbon, advantageously makes it possible to reduce 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 in step b).

[0079] “Passage of the composition over an adsorbent material” means the flow of the composition over the adsorbent support.

[0080] The adsorbent materials may be, for example, activated carbon, zeolites, clays or functionalized porous compounds. Preferably, it is activated carbon.

[0081] In the case of passing the lubricating and/or cooling composition obtained in step b) over activated carbon, the quantity of activated carbon used is preferably between 0.5 and 60 g of activated carbon per liter 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.

[0082] The flow rate of the lubricating and/or cooling composition obtained in step b) may be between 1 m ³ /h and 15 m ³ /h, for example between 5 and 10 m ³ /h.

[0083] Preferably, the activated carbon is characterized by a density of between 200 and 500 kg/m ³ , for example measured according to the ASTDM D2854 standard.

[0084] Preferably, the activated carbon is a coal, preferably comprising from 70 to 95%, advantageously from 80 to 90% by weight of carbon.

[0085] The step of passing the lubricating and/or cooling composition obtained in step b) onto an adsorbent support, preferably onto activated carbon, may be preceded by the following preliminary steps:

- one or more distillation steps, in addition to distillation step b); and

- a filtration step, in particular as defined previously. [0086] According to one embodiment, the method comprises at least one step of hydrogenation (or hydrotreatment) of the lubricating and/or cooling composition obtained in step b), preferably which follows a prior step of dehydration and/or distillation. Said 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, generally in the presence of a hydrotreatment catalyst. Such a catalyst may contain, for example, at least one oxide or a 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.

[0087] According to one embodiment, the method comprises at least one step of liquid/liquid extraction by a solvent of the lubricating and/or cooling composition obtained in step b), preferably which follows a prior step of dehydration and/or distillation.

[0088] In particular, liquid/liquid extraction by a solvent advantageously makes it possible to lighten a used dark-colored lubricating and/or cooling composition, to eliminate at least in part the bad odor or the aromatic compounds, in particular polycyclic aromatic hydrocarbons (PAHs). Said extraction step(s) can be implemented by any technique known to those skilled in the art. The extraction is generally carried out in a mixer-settler or in an extraction column, using a suitable extraction solvent.

[0089] According to one embodiment, the method comprises at least one step of decanting the lubricating and/or cooling composition obtained in step b). Said decanting step(s) may be implemented by any technique known to those skilled in the art.

Lubricating and/or cooling composition obtained after step b)

[0090] The lubricating and/or cooling composition obtained after step b) is free of ester and free aliphatic acids. For example, the lubricating and/or cooling composition obtained after step b) may comprise 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 step b) may also comprise less than 0.1% free aliphatic acids, or less than 0.01% free aliphatic acids, or less than 0.001% free aliphatic acids.

[0091] In certain 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 possibly up to 300 ppm, in particular up to 290 ppm, for example up to 285 ppm.

[0092] It may also be characterized by a high content of one or more elements chosen from chlorine, oxygen and nitrogen. It may, for example, have a chlorine content of at least 5 ppm, in particular at least 10 ppm, in particular greater than or equal to 20 ppm, in particular greater than or equal to 30 ppm. [0093] The chlorine content can be, for example, evaluated by any method known to those skilled in the art, for example by X-ray fluorescence (XRF).

[0094] The present disclosure also relates to the use of the method for improving 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 comprising esters,

- improving the recyclability of lubricating and/or cooling compositions comprising esters,

- increasing the content of bio-sourced compounds in lubricating and/or cooling compositions, and/or

- a reduction in the use of fossil resources.

[0095] Examples

[0096] Products used:

- Sulfuric acid >98.5%

- Anhydrous methanol >99%

- Palmitic acid

- Triglycerides >99% in triesters

- NaHCO3 in 1 M aqueous solution (or saturated)

- HCI 0.1 N

[0097] Equipment used: Double jacketed reactor, motor agitation and Teflon stirring blade. Heating bath, refrigerant and dropping funnel.

[0098] Compositions tested

[Table 2]

0099] Example 1

[0100] Compositions C1 and C2 are subjected to the treatment process as described in the present application.

Composition C1 is subjected to a transesterification step, then a distillation step which allows the methyl esters obtained to be separated from the rest of the composition (the base oil of group I).

Composition C2 is subjected to an esterification step, then a transesterification step, and finally a distillation step which allows the methyl esters obtained to be separated from the rest of the composition (the base oil of group I). After distillation, the compositions obtained are subjected to a standard process for recycling used lubricating compositions, which includes a soda treatment step (WO94/21761). It is possible to recycle the lubricating composition in its entirety and obtain a re-refined lubricating oil.

[0101] Protocol for the esterification step:

[0102] Lubricating composition C2 is introduced into the reactor. The composition is stirred and heated to 60°C. When the temperature is reached, the methanol containing the sulfuric acid is introduced through the dropping funnel (molar ratio alcohol: palmitic acid = 15; H2SO4 at m=0.4% relative to the alcohol). The system is maintained at 60°C for 3 h.

[0103] The mixture is cooled to 40°C. The alcohol phase is separated by decantation, then the organic medium is washed with the 20% v/v NaHCO3 solution which is gradually added to the reactor.

[0104] Methanol and water are evaporated in a rotary evaporator under reduced pressure of 80 mbar at 70°C.

[0105] The reaction is monitored by GC-FID, and after 3 hours, the esterification reaction is complete.

[0106] Protocol for the transesterification step

[0107] Lubricating composition C1, or lubricating composition C2 after the esterification step, is introduced into the reactor. The composition is stirred and heated to 60°C. When the mixture is at reflux, the anhydrous MeONa catalyst and anhydrous methanol are added to the medium (molar ratio alcohol:triglycerides = 11; MeONa at m=0.5% relative to the alcohol).

[0108] After 2 hours at reflux and verification of the glyceride composition by GC-FID, the mixture is cooled to 40°C, the phase containing the glycerol and part of the methanol is decanted. The mixture is washed with 0.1 N HCl 20% V/V then with deionized water at 20% v/v.

[0109] Methanol and water are evaporated using a rotary evaporator under reduced pressure of 80 mbar at 70°C. The reaction yield is 97.9%.

[0110] Comparative example

[0111] Compositions C1 and C2 are subjected directly to the standard process for recycling used lubricating compositions, which includes treatment with soda, without prior transesterification (WO94/21761). It is then not possible to implement the recycling process as a whole, because during the treatment with soda, the formation of solid soaps is observed, which disrupts the recycling process.

Claims

Claims [Claim 1] A method of treating a lubricating and/or cooling composition comprising at least one ester, said ester comprising an alcohol residue and at least one acid residue, wherein said alcohol residue comprises m carbon atoms and one or more alcohol functions, said method comprising at least the following steps: a. A transesterification step comprising bringing said lubricating and/or cooling composition into contact with at least one monoalcohol comprising n carbon atoms, with n < m, and a catalyst; b. A distillation step for separating the esters comprising an alcohol group comprising n carbon atoms obtained in step a) from the remainder of the lubricating and/or cooling composition. [Claim 2] Process according to claim 1 characterized in that the catalyst is a basic catalyst, preferably chosen from alcoholates. [Claim 3] Method according to one of the preceding claims, characterized in that the esters contained in the lubricating and/or cooling composition to be treated are chosen from - aliphatic acid esters, where the aliphatic acid residue comprises a hydrocarbon chain preferably having from 3 to 36 carbon atoms and one or two acid functions. - polyol esters, preferably glycerol, trimethylolpropane or neopentyl glycol esters, - polyesters of unsaturated fatty acids containing up to 6 acid units, and - their mixtures. [Claim 4] Method according to one of the preceding claims, characterized in that the content of esters 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 between 0.5 and 99%, preferably between 1 and 40%, and more preferably between 3 and 30%. [Claim 5] Method according to one of the preceding claims, characterized in that the lubricating and/or cooling composition to be treated comprises at least one free aliphatic acid, preferably at least 0.001% of free aliphatic acid, preferentially between 0.001 and 5% of free aliphatic acid. [Claim 6] Process according to claim 5, characterized in that the content of free aliphatic acid is greater than or equal to 1%, and in that the process comprises, before step a), a step of esterification of the free aliphatic acids carried out with an alcohol and an acid catalyst. [Claim 7] Method according to one of the preceding claims, characterized in that the lubricating and/or cooling oil to be treated comprises at least 50% by weight of at least one oil of base of mineral or synthetic origin belonging to groups I to IV, preferably at least 60%. [Claim 8] Method according to 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. [Claim 9] Method according to one of the preceding claims, characterized in that it comprises at least one step c) of treatment of the lubricating oil obtained in step b) chosen from dehydration, distillation, filtration, liquid/liquid extraction, decantation, and passage over an adsorbent material. [Claim 10] Method according to one of the preceding claims, characterized in that step a) is carried out in an anhydrous medium. [Claim 11] Method according to one of the preceding claims, characterized in that step a) is carried out at a temperature between 20 and 150°C, preferably between 40°C and 100°C. [Claim 12] Method according to one of the preceding claims, characterized in that the lubricating and/or cooling composition to be treated comprises at least 0.05% water, and in that the method comprises, before step a), a dehydration step, so as to obtain a water content of less than 0.05% in the lubricating and/or cooling composition to be treated. [Claim 13] Use of the method according to one of the preceding claims for improving 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 comprising esters, - improving the recyclability of lubricating and/or cooling compositions comprising esters, - increasing the content of bio-sourced compounds in lubricating and/or cooling compositions, and/or - a reduction in the use of fossil resources