PROCESS FOR PURIFYING LUBRICATING OILS AT LEAST PARTIALLY RE-REFINED BY BASIC TREATMENT UNDER MICROWAVE IRRADIATION

Abstract

The present invention relates to the field of re-refining or regeneration of used lubricating compositions. More specifically, the present invention relates to a process for purifying lubricating oils, optionally at least partially re-refined by basic treatment under microwave irradiation, making it possible to obtain a lubricating oil having, in particular, a reduced silicon content, suitable for use as a base oil for the formulation of a new lubricating composition.

Description

Title of the invention: METHOD FOR PURIFYING LUBRICATING OILS AT LEAST PARTIALLY RE-REFINED BY BASIC MICROWAVE IRRADIATION TREATMENT technical field

[0001] The present invention relates to the field of re-refining or regeneration of used lubricating compositions. More specifically, the present invention relates to a process for purifying lubricating oils, optionally at least partially re-refined by basic treatment under microwave irradiation, making it possible to obtain a lubricating oil having, in particular, a reduced silicon content, suitable for use as a base oil for the formulation of a new lubricating composition. Previous technique

[0002] Lubricating compositions, more simply called "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, from elements emanating from the wear of the parts with which the oil is in contact during its use or from fuel fractions 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 lubricating composition described as "used," "worn out," or "degraded." This is why lubricating compositions need to be replaced after a certain period of use.

[0005] In consideration of current environmental protection and resource conservation issues, research has focused on the development of methods for re-refining or reconditioning lubricant compositions used, for the purpose of regenerating lubricating oils that can be reused for the formulation of new lubricating compositions.

[0006] To this end, used lubricating compositions are generally subjected to various operations aimed at removing contaminants and other undesirable elements present therein, and are thus brought under the control of operations similar to those used in the field of petroleum oil refining. For example, among the many methods proposed for re-refining used lubricating compositions, one can cite that described in document EP 0 708 174, which includes steps of dehydration, vacuum distillation, solvent extraction, and hydrotreating.

[0007] A process for preparing a regenerated lubricating oil, advantageously having a reduced content of undesirable polycyclic aromatic hydrocarbons (PAHs) present in a used lubricating composition, is also described in document WO 2018 / 109208, and includes passing the used lubricating composition over activated carbon.

[0008] However, even if such processes make it possible to obtain re-refined lubricating oils with good performance, these re-refined or regenerated oils generally include silicon contents still significantly higher than those of conventional base oils obtained directly from petroleum refining.

[0009] However, the presence of silicon in base oils intended for the formulation of lubricants, in particular for the lubrication of mobile or stationary motorization systems, especially engine lubricants, is undesirable given the wear problems it can cause.

[0010] Therefore, the quantity of re-refined lubricating oils, or the type of re-refined lubricating oils, that can be incorporated in the formulation of lubricating compositions is limited in order to meet the required specifications for the lubricant in terms of silicon content. Consequently, re-refined lubricating oils are generally introduced in limited quantities in favor of virgin base oils.

[0011] There remains a need to optimize the composition of re-refined oils, in particular to reduce their silicon content, in order to be able to fully utilize these regenerated oils for their use as base oils in the formulation of lubricating compositions.

[0012] Most existing purification treatments are carried out at relatively high temperatures, particularly to allow for the efficient removal of heteroatoms, especially silicon. While treatments in a basic medium allow for the removal of silicon, chlorine, and other heteroatoms, such as oxygen and nitrogen, with good efficiency, the high temperatures required implementation can lead to secondary reactions such as the formation of polyaromatic hydrocarbons in lubricants containing traces of esters or other compounds containing heteroatoms.

[0013] Furthermore, the energy consumption of these processes is significant. Indeed, it is necessary to heat all of the regenerated oil in order to carry out these treatments, which requires a considerable energy expenditure, as is the case, for example, for the process described in application WO2023 / 118063A1.

[0014] There is therefore a need to improve existing purification processes, and in particular to remove silicon, by limiting secondary reactions and improving the energy efficiency of the processes. Summary

[0015] The present invention aims precisely to overcome the constraint linked to the presence of undesirable elements, such as silicon, in used or regenerated oils, by limiting energy consumption, for example by at least 50% or 70%.

[0016] It proposes more particularly a process for purifying lubricating oils possibly at least partially re-refined, advantageously allowing the reduction of their silicon content, in order to access regenerated and purified oils usable as base oils for the formulation of lubricating compositions.

[0017] Thus, the invention relates to a process for purifying used oil, possibly at least partially re-refined, comprising: - (a) contacting said used oil with a basic medium comprising a basic compound in a polar solvent selected from (i) water, (ii) a polar solvent comprising an alcohol and / or an ether function, and mixtures thereof, and the irradiation of the reaction medium by microwaves under conditions effective in heating the basic medium to a temperature at most equal to its boiling point at the pressure applied, - (b) a separation between the basic compound and the product resulting from the setting into contact with said used oil.

[0018] By irradiating the reaction medium with microwaves, the basic medium, and in particular the polar solvent with the ions present, will absorb these microwaves and heat up rapidly. This rapid heating will improve contact by increasing the exchange surface area between the basic medium and the used oil, thus promoting the modification of its composition and its treatment, without heating it to high temperatures. This makes it possible to treat the used oil by limiting, or even eliminating, secondary reactions. It also leads to increased energy efficiency by specific heating of the basic medium, the used oil having a low polarity and absorbing practically no microwaves.

[0019] Microwaves are a specific source of electrical energy that heats only the reactant responsible for the treatment, for example, sodium hydroxide. This saves energy and prevents overheating of the used oil, thereby avoiding or reducing side reactions.

[0020] With this process, energy consumption can be reduced by 50%, 60%, 70%, 80%, 90%, or even 95%. For example, for the same load treated by a conventional heating process (3000W autoclave heated for 1 hour at full power, then 30 minutes at 80% of power) and by microwave irradiation (5 minutes of irradiation at 800W then 15 minutes at 150W), energy consumption can be reduced from 4.2 kWh to 0.1 kWh, i.e., a reduction of more than 95%.

[0021] This disclosure therefore also relates to the use of the process to improve the eco-performance of lubricating compositions, eco-performance preferably being characterized by: - minimizing the carbon footprint of lubricating compositions, - improving the recyclability of lubricating compositions, and / or - reducing the use of fossil resources. Brief description of the drawings

[0022] Other features, details and advantages will become apparent from reading the detailed description below and from analyzing the accompanying drawings, in which: Fig. 1

[0023] [Fig. 1] Figure 1 describes one possible embodiment of the invention. In this possible embodiment, the used oil composition, optionally at least partially re-refined (1), is first optionally pre-treated in a pre-treatment section (SI) by undergoing one or more pre-treatment steps (PTT) selected from steps of dehydration, distillation, filtration, hydrogenation, liquid / liquid extraction, transesterification, selective neutralization, decantation, and / or passing the used oil over an adsorbent material, in particular activated carbon. The pre-treated composition (2) is then sent to a treatment section (A) for the implementation of the basic treatment under microwave irradiation (TTbase) in accordance with step (a) of the invention.The treatment can be carried out in an enclosure comprising one or more microwave generators, and optionally waveguides, for example of the type described in reference to the process. The effluent (3) leaving this treatment section (A) can then be sent to an optional solids separation section (S2), or be sent directly to a separation section (B) for . implement step (b) TTsep, for example by washing and / or distillation. Section (B) may thus include a washing section and / or a distillation section to implement one or more of steps (i) to (ii) as described by reference to the process. The effluent (5), exiting step TTsep, may then be sent to a second optional solids separation section (S3), or be sent directly to a purification section (C) to implement step (c), or be sent directly to an optional treatment section (D) for the implementation of one or more post-treatment steps (PostTT) selected from dewatering, distillation, filtration, hydrogenation, liquid / liquid extraction, transesterification, selective neutralization, decantation, and / or passing the used oil over an adsorbent material, in particular activated carbon. Detailed description

[0024] Definitions

[0025] Boiling points as mentioned herein are measured at atmospheric pressure, unless otherwise specified. An initial boiling point is defined as the temperature at which the first vapor bubble forms. A final boiling point is the highest temperature attainable during distillation. At this temperature, no more vapor can be transported to a condenser. The determination of the initial and final boiling points relies on techniques known in the trade, and several methods adapted according to the distillation temperature range are applicable, for example, NF EN 15199-1 (version 2020) or ASTM D2887 for measuring the boiling points of petroleum fractions by gas chromatography, ASTM D7169 for heavy hydrocarbons, and ASTM D7500, D86, or DI 160 for distillates.

[0026] The expression "polar solvent" in the present patent application covers all chemical species, alone or in mixture, comprising at least one carbon-hydrogen, carbon-halogen, carbon-chalcogen or carbon-nitrogen covalent bond and having a non-zero dipole moment, as well as water.

[0027] The term "solvent" includes the aforementioned "polar solvents" and nonpolar solvents, which include, for example, any type of linear, branched, cyclic and / or aromatic saturated or unsaturated hydrocarbon such as pentane, cyclohexane, olefins, toluene or xylene or certain other solvents with zero or almost zero dipole moment such as tetrachloromethane or carbon disulfide.

[0028] The expressions "between ... and ...", "ranging from ... to ...", "made up of ... to ...", and "varying from ... to ...", must be understood inclusive of limits, unless otherwise stated.

[0029] In the description and examples, unless otherwise indicated, percentages are mass percentages. Percentages are therefore expressed as a percentage of the total mass of the used oil.

[0030] Used oil, possibly at least partially re-refined

[0031] According to the invention, the terms "used oil" or "used lubricating composition" (or more simply "used lubricant") refer to any lubricating composition that has been used for the lubrication of moving parts, in particular metal parts, of a mechanical system, such as bearings, gears or motors.

[0032] A used lubricating composition can come from various sources. In particular, as detailed later in the text, it can be a lubricant that has been used to lubricate a motorization system, in particular a "mobile" one, or to lubricate an industrial system, in particular a "stationary" one.

[0033] It is understood that a used lubricating composition may be a mixture of several used lubricating compositions, from the same source or from several different sources.

[0034] Due to their origin, used lubricants, particularly engine lubricants, contain a number of degradation products derived from the oil itself or the additives it contains, as well as metal particles, metal oxides, and other elements, originating, for example, from the engine. Used oil may, in particular, contain a high level of undesirable elements, for example, calcium (Ca), iron (Fe), magnesium (Mg), sodium (Na), nickel (Ni), phosphorus (P), silicon (Si), chlorine (Cl), zinc (Zn), etc.

[0035] Unlike a "used lubricating composition", the expression "new lubricating composition" in the sense of the invention designates a lubricating composition which has not yet been used for the lubrication of moving parts of a mechanical system, and which is ready for this use.

[0036] In the context of the present invention, the expression "lubricating oil at least partly re-refined", also referred to more simply in the following text as "regenerated oil" or "recycled oil", designates an oil derived at least partly from a used lubricating composition that has been subjected to one or more treatment steps, known as re-refining treatment.

[0037] In other words, a lubricating oil that is at least partially re-refined is obtained after one or more processing steps of a used lubricant, aimed at eliminating, at least partially, a number of contaminating elements present therein, such as dust, water, fuel fractions, metallic elements and other residues resulting from the degradation of additives present in the lubricant.

[0038] As detailed in the rest of the text, these pre-treatment steps to which the lubricating oils have been subjected, before their implementation in a purification process according to the invention, can in particular be chosen from steps of dehydration, distillation, filtration, hydrogenation, liquid / liquid extraction, decantation, selective neutralization, transesterification and / or passing of the used lubricant over an adsorbent material, in particular over activated carbon.

[0039] A composition at least partially re-refined according to the invention is thus distinguished from a used lubricating composition or oil. Compared to a used lubricant, the lubricating oil at least partially re-refined has, in particular, a reduced content of certain undesirable contaminants, for example water or fuel, and advantageously a reduced PAH content, and preferably meets a number of quality standards required for a basic lubricating oil.

[0040] A lubricating oil at least partly re-refined according to the invention is also distinct from a virgin or new base oil (i.e. a refined base oil), in particular with regard to the silicon content present in the regenerated oil.

[0041] In particular, an oil at least partly re-refined implemented in the purification process according to this disclosure may include a particularly high silicon content and, in any event, undesirable for the implementation of this regenerated oil for the formulation of a lubricating composition.

[0042] The silicon content of a regenerated oil used in the purification process according to this disclosure may be in particular strictly greater than 10 ppm, more particularly greater than or equal to 15 ppm, for example greater than or equal to 20 ppm, or even greater than or equal to 30 ppm.

[0043] In some cases, the silicon content of a regenerated lubricating oil can reach up to 285 ppm, or even up to 290 ppm, or even up to 300 ppm.

[0044] The silicon content can be evaluated by any method known to those skilled in the art, for example by X-ray fluorescence (XRF), by inductively coupled plasma atomic emission spectrometry (ICP-AES) or by inductively coupled plasma mass spectrometry (ICP-MS).

[0045] Advantageously, as illustrated in the following examples, the purification process according to the invention of a used oil makes it possible to significantly reduce the silicon content present.

[0046] Advantageously, the silicon content initially present in the regenerated lubricating oil can be reduced by at least 25% by mass of its initial value, in particular by at least 30%, advantageously by at least 40%, preferably by at least 50% of its initial value.

[0047] Advantageously, in particular regardless of the silicon content of the starting regenerated lubricating oil, the process according to the invention makes it possible to reduce the quantity of silicon to a content strictly less than 25 ppm, in particular less than or equal to 20 ppm, in particular less than or equal to 1 Ippm.

[0048] Thus, the purification process of the invention proves to be particularly advantageous for treating regenerated lubricating oils which, despite the re-refining treatments to which they have been subjected, have a high residual silicon content, which is undesirable for their use as base oils for the formulation of new lubricants.

[0049] Furthermore, advantageously, as illustrated in the following examples, in addition to significantly reducing the silicon content of the regenerated oil, the process of the invention advantageously reduces the content of other elements that may be considered undesirable, in particular chlorine, nitrogen, and / or oxygen. These elements can prove undesirable in the lubricant, particularly with regard to the corrosion effects (for chlorine), the changes in interfacial properties (for nitrogen), and the tendency toward oxidation (for oxygen) that they can cause.

[0050] In particular, the process of the invention advantageously makes it possible to overcome the constraint of implementing regenerated lubricating oils for the formulation of new lubricants, linked to their silicon content.

[0051] Thus, regenerated and purified lubricating oils according to the process of the invention can be incorporated alone or in mixture with one or more virgin base oils, for the formulation of a lubricant, without limitation of quantity, since they do not contribute to increasing the silicon content in the lubricant.

[0052] Thus, the present invention also relates, according to another of its aspects, to the use of a regenerated and purified lubricating oil according to the process according to the invention, to formulate a new lubricating composition, in particular by adding it with one or more conventional additives in the field of lubricants.

[0053] The process of the invention makes it possible to purify any used oil, possibly at least partially re-refined; in other words, any lubricating oil derived from a used lubricating composition, whether or not it has been subjected to one or more refining treatment steps. Thus, according to one embodiment, the used oil is an oil that has already been subjected to one or more refining treatment steps. According to another embodiment, the used oil has not yet been subjected to a refining treatment step, and the process of the present invention is the first refining treatment step; therefore, the present process can be followed by one or more refining treatment steps. The silicon content of the used oil not having has not yet been subjected to a refining treatment step which may be the same as that described above for used oil at least partially re-refined.

[0054] Used lubricating compositions and, consequently, regenerated lubricating oils, comprise, in majority quantity, 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.

[0055] It may be a mixture of several base oils, for example a mixture of two, three, or four base oils.

[0056] 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.

[0057] [Tables 1] Saturates content Sulfur content Viscosity index (VI) Group I Mineral oils < 90% > 0.03% 80 <VI < 120 Groupement II Huiles hydrocraquées >90% <0.03% 80 <VI< 120 Groupement III Huiles hydrocraquées ou hydro-isomérisées > 90% <0.03% >120 Group IV Polyalphaolephs (PAOs) Group V Esters and other bases not included in groups I to IV

[0058] In particular, the used lubricating composition, from which the regenerated lubricating oil used in the process of the invention is derived, 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).

[0059] The purification process according to the invention advantageously allows the purification of used lubricating oils comprising one or more base oils of groups I, II, III and / or IV of the API classification, in particular of groups II and / or III.

[0060] According to a particular embodiment, the used lubricating oil, treated according to the invention, can be derived from a used lubricating composition, possibly with less partly re-refined, having 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 even marine vehicles.

[0061] According to another particular embodiment, the used lubricating oil, treated according to the invention, can be obtained from the treatment of a used lubricating composition, possibly at least partly re-refined, having been used for the lubrication of an industrial system, in particular a "stationary" one, that is to say including, without limitation, turbines, compressors, hydraulic systems, gears, or even forming or cutting machines.

[0062] A used lubricating composition, from which the used lubricating oil to be treated according to the invention is derived, may contain various conventional additives in the field of lubricants, such as friction modifier 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.

[0063] As already mentioned previously, the properties of the used lubricating 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 an internal combustion engine

[0064] Due to their origin, used lubricating compositions may thus 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.

[0065] The composition of the used lubricant can of course be different depending on the origin of the lubricant, its initial formulation and the fact that it may have been contaminated differently depending on its use.

[0066] The used oil according to the invention comes more particularly from a used lubricating composition which has or has not been subjected to one or more prior pre-treatment steps known in the field of re-refining used lubricants.

[0067] In particular, these treatment steps aim to eliminate, at least partially, water, solid particles, fuel and / or other contaminants, such as PAHs, which are undesirable in the context of lubricant formulation.

[0068] According to a particular embodiment, the used oil according to the invention comes from a used lubricant that has been subjected to one or more prior steps of dehydration, distillation, filtration, hydrogenation, liquid / liquid extraction, decantation, selective neutralization, transesterification and / or passing the used lubricant over an adsorbent material, preferably such as those detailed below.

[0069] According to another embodiment, the used oil has not been subjected to a prior refining treatment step. One or more refining treatment steps may then be carried out following the present purification process, for example one or more steps of dehydration, distillation, filtration, hydrogenation, liquid / liquid extraction, decantation, selective neutralization, transesterification and / or passing the used lubricant over an adsorbent material, preferably as detailed below.

[0070] The detailed refining treatment steps below for used oil can therefore be carried out before or after the process of this application.

[0071] Preferably, the used oil is subjected to at least one dehydration step. This dehydration step makes it possible to remove any water that may be present in the used lubricant.

[0072] Advantageously, the used oil thus comprises a water content less than or equal to 10% by mass, in particular less than or equal to 5% by mass, in particular less than or equal to 5% by mass, notably less than or equal to 2% by mass and more particularly less than or equal to 1% by mass, relative to the total mass of said used oil.

[0073] 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 stream of hot air over the used lubricating composition.

[0074] 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.

[0075] Preferably, the used oil undergoes at least one filtration step. 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.

[0076] Preferably, the used oil is subjected to at least one distillation step, preferably following a prior dehydration step. This distillation step(s) can be carried out using any technique known to those skilled in the art. 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, and more preferably between 300 °C and 380 °C. In particular, they can be operated at a pressure between 25 and 2,000 Pa, preferably between 50 and 1,000 Pa, more particularly between 50 and 250 Pa.

[0077] Advantageously, the used oil is subjected to at least one step of passing said used oil over an adsorbent material.

[0078] The adsorbent material advantageously allows for the selective adsorption of aromatic compounds, in particular polycyclic aromatic hydrocarbons (PAHs).

[0079] 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 used lubricant composition.

[0080] The term "passage of the used lubricating composition over an adsorbent material" means the flow of the used lubricating composition over the adsorbent support.

[0081] The adsorbent materials can be, for example, activated carbon, zeolites, clays or functionalized porous compounds. Preferably, they are activated carbon.

[0082] For example, used oil can be subjected to treatment according to the process described in document WO 2018 / 109208.

[0083] In the case of passing the used lubricating composition over activated carbon, the quantity of activated carbon used is preferably between 0.5 and 60 g of activated carbon per litre of used lubricating 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.

[0084] The flow rate of the used lubricant composition can be between 1m3 / h and 15 m3 / h, for example between 5 and 10m3 / h.

[0085] Preferably, the activated carbon is characterized by a density between 200 and 500 kg / m3, for example measured according to the ASTDM D2854 standard.

[0086] Preferably, the activated carbon is coal coal, preferably comprising 70 to 95%, advantageously 80 to 90% by weight of carbon.

[0087] The step of passing the used lubricating composition over an adsorbent support, preferably activated carbon, is advantageously preceded by the following preliminary steps: - one or more distillation stages; and - a filtration step, in particular as defined previously.

[0088] Advantageously, the used oil is subjected to at least one hydrogenation (or hydrotreating) step, preferably following a prior dehydration and / or distillation step. This hydrogenation step(s) can 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 carrier, for example, alumina, silica-alumina, or a zeolite.

[0089] Advantageously, the used oil is subjected to at least one liquid / liquid extraction step with a solvent, preferably following a prior dehydration and / or distillation step. In particular, liquid / liquid extraction with a solvent advantageously clarifies dark-colored used oil and at least partially removes unpleasant odors or aromatic compounds, especially polycyclic aromatic hydrocarbons (PAHs). This extraction step or 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.

[0090] Advantageously, the used oil is subjected to at least one settling step. This settling step or steps can be carried out by any technique known to those skilled in the art.

[0091] According to one embodiment, the used oil is subjected to at least one transesterification step. This transesterification step is particularly suitable when the composition includes esters, these esters having an alcohol residue comprising m carbon atoms. When the used oil contains more than 3% ester, this transesterification step is preferably carried out prior to the process of the present invention. This transesterification step comprises contacting said used oil 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 from the remainder of the used oil.

[0092] Transesterification allows the esters present in the used oil to be transformed into an ester having a short-chain alcohol part -OR”, 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.

[0093] Transesterification is a well-known reaction. It allows the exchange of the -OR alcohol residue of an ester for another -OR alcohol residue. In this case, it allows to exchange 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 used oil to be treated comprises an alcohol residue -OR with a carbon atoms, and the ester obtained after transesterification has an alcohol residue -OR” with an carbon atoms, n being an integer and n < m. The ester obtained after transesterification therefore has an alcohol residue with a shorter chain.

[0094] This reaction is catalyzed by an acidic or basic catalyst. Preferably, the catalyst is basic, preferably chosen from among the alkoxides.

[0095] Examples of acid catalysts include: - Brønsted acids, such as H2SO4, H3PO4, HCl, methansulfonic acid, or para-toluenesulfonic acid, and - Lewis acids, such as AlCl3, BC13, FeCl3, ZnCl2, and zeolites.

[0096] Acid catalysts can be homogeneous or heterogeneous.

[0097] Among the basic catalysts, we can mention: - bases such as NaOH, LiOH or KOH - alcoholates, - basic oxides such as ZnO, MgO and CaO, - zinc aluminates.

[0098] Advantageously, the catalyst is an alkoxide, preferably selected from methanolates and ethoxides. Examples of alkoxides include methyl, ethyl, and propyl alkoxides. In one particular embodiment, the catalyst is selected from sodium methoxide, potassium methoxide, sodium ethoxide, potassium ethoxide, and mixtures thereof. Basic catalysts may be homogeneous or heterogeneous.

[0099] The quantity 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%.

[0100] 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 contained in the composition to be treated, preferably between 5 and 20 equivalents.

[0101] Transesterification is preferably carried out in anhydrous medium. Anhydrous medium is defined as a composition containing less than 0.05% water. The reaction can be carried out under nitrogen or argon.

[0102] According to one embodiment, the used oil 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, so as to obtain a water content of less than 0.05% in the used oil to be treated. This step of Dehydration can 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.

[0103] Transesterification can be carried out at a temperature between 20 and 150°C, preferably between 40°C and 100°C.

[0104] Transesterification can be followed by a distillation step to separate the esters comprising an alcohol group with n carbon atoms obtained from the remainder of the used oil. This distillation can be carried out by any technique known to those skilled in the art. For example, it could be 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, and more preferably between 300 °C and 380 °C. In particular, they can 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.

[0105] According to one embodiment, the used oil is subjected to at least one selective neutralization step. This selective neutralization step is particularly suitable when the used oil contains at least one ester and at least one free organic acid. This selective neutralization step includes at least one step of treating said used oil with at least one base having a pKb between 2 and 6.

[0106] 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.

[0107] According to one embodiment, the base is selected from alkali carbonates, alkali metal phosphates, phenol salts, tertiary amines, and mixtures thereof. Examples of alkali metal phosphates include Na3PO4. Examples of phenol salts include sodium phenate. Preferably, the base is selected from carbonates, and more preferably, it is selected from the group consisting of sodium carbonate, potassium carbonate, cesium carbonate, rubidium carbonate, and mixtures thereof. Most preferably, the base is sodium carbonate.

[0108] Preferably the base is a non-nucleophilic base, which avoids transesterification reactions. The base can be in solid form or in aqueous solution.

[0109] According to one embodiment, the basic quantity used is between 2 and 40% by weight relative to the weight of the used oil, preferably between 3 and 30%, and more preferably between 4 and 20%.

[0110] 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 initially heated to 100°C, which can allow the water in the composition to evaporate, then heated to a temperature above 100°C.

[0111] According to one embodiment, the selective neutralization is carried out at ambient pressure.

[0112] It is understood that the invention is in no way limited to the processing of used oils as described above. The process of the invention can thus be used to purify any lubricating oil, possibly at least partially re-refined, particularly one resulting from prior treatment steps other than those described above.

[0113] Generally, the used lubricating oil used in the process of the invention has a kinematic viscosity measured at 100 °C according to ASTM D445 of between 2 and 12 mm² / s, in particular between 3 and 10 mm² / s.

[0114] The used lubricating oil used in a purification process according to the invention is characterized in particular by a high silicon content, in particular strictly greater than 10 ppm, in particular greater than or equal to 15 ppm, more particularly greater than or equal to 20 ppm, in particular greater than or equal to 30 ppm, in particular up to 300 ppm, in particular up to 290 ppm, for example up to 285 ppm.

[0115] The used lubricating oil used in a purification process according to the invention may also be characterized by a high content of one or more elements selected from chlorine, oxygen, and nitrogen. For example, it may 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.

[0116] The chlorine content can, for example, be evaluated by any method known to those skilled in the art, for example by X-ray fluorescence (XRF).

[0117] Purification process

[0118] Step (a) according to the invention may include one or more of the following features: - step (a) is carried out in the presence of 0.1 to 50% by mass of basic compound relative to the total mass of said composition, preferably 0.1 to 15% by mass, more preferably 1 to 15% by mass, even more preferably 1 to 10% by mass. - the basic medium / composition ratio is 0.1 / 99.9 to 80 / 20, preferably 1 / 99 to 60 / 40, more preferably 5 / 85 to 50 / 50, even more preferably 10 / 90 to 45 / 55; - The basic compound is chosen from LiOH, NaOH, CsOH, Ba(OH)2, Na2O, KOH, K2O, CaO, Ca(OH)2, MgO, Mg(OH)2, NH4OH, TMAOH (Tetramethylammonium hydroxide), TEAOH (Tetraethylammonium hydroxide), TBAOH, MeONa, EtONa and their mixtures; - The contact is made for a duration of 1 second to 48 hours, preferably from 30 seconds to 2 hours, preferably longer from 1 minute to 1 hour. - the polar solvent is chosen from (i) water, (ii) alcohols in the C4 to C1 groups, preferably methanol, ethanol, propan-1-ol, propan-2-ol, butan-1-ol, butan-2-ol, 2-methylpropan-1-ol, ethylene glycol, propylene glycol, (iii) alcohols comprising an ether function, preferably glycol ethers such as polyethylene glycol, polypropylene glycol, tetraethylene glycol, diethylene glycol, triethylene glycol, (iv) cyclic ethers, preferably tetrahydrofuran, 2-methyltetrahydrofuran, cyclopentylmethyl ether, tetrahydropyran, 1,4-dioxane, eucalyptol, and mixtures thereof - the contact is made at an absolute pressure of 0.05 to 100 bars, preferably from 1 to 50 bars.

[0119] Step (a) is a waste oil treatment step in the presence of a basic medium under microwave irradiation.

[0120] This treatment makes it possible, in particular, to modify the compounds containing heteroatoms, and especially those containing silicon, contained in the used oil and to promote their subsequent elimination. In particular, despite the complexity of the hydrocarbon matrix, microwave irradiation makes it possible to selectively heat the basic medium due to the presence of a polar solvent, and thus reduce the temperature increase of the used oil, reducing, or even eliminating, secondary reactions.

[0121] Microwaves are electromagnetic waves of a specific wavelength and frequency range, situated between infrared and radio frequencies in the electromagnetic spectrum. Microwaves typically have a frequency of 300 MHz to 300 GHz (wavelength from 1 m to 1 mm). Examples of usable microwave frequencies are 0.915 GHz, 2.45 GHz, 5.8 GHz, 24 GHz, or any other frequency within the range of 300 MHz to 300 GHz.

[0122] Microwaves can be generated by one or more microwave generators, for example arranged around or inside a reaction zone containing the reaction medium. Optionally, one or more waveguides may be provided to guide the microwaves towards the reaction medium. The microwaves are generated by a system called a magnetron at a specific frequency; it can be a magnetron or any other electronic system, corresponding to a wavelength specific. Wave propagation within the reaction zone can be single-mode or multi-mode depending on the dimensions of the reaction zone.

[0123] The treatment of step (a) can be implemented in any device allowing contact between the basic medium and the used oil, and comprising one or more microwave generators or magnetrons, and optionally one or more waveguides.

[0124] The reaction zone in which the used oil and the basic medium are brought into contact can include one or more reactors equipped with microwave generator(s), operating continuously in co-current or counter-current, or one or more reactors equipped with microwave generator(s) and optionally with one or more mixers, operating discontinuously (in batch).

[0125] When contact is continuous, it is generally preferable to circulate the basic medium in a downward direction, while the used oil can circulate in either an upward or downward direction. Preferably, the basic medium is brought into contact with the used oil in the form of droplets. This can be achieved using one or more suitable injection devices or one or more static mixers, possibly under turbulent flow conditions.

[0126] Turbulent flow can be obtained when the flow has a Reynolds number of at least 2000, preferably at least 3000, more preferably at least 4000, or even at least 10000. Turbulent flow can advantageously be achieved using at least one static mixer. That is to say, the used oil and the basic medium are introduced into at least one tube equipped with at least one internal element capable of generating turbulent flow with a Reynolds number of at least 2000.

[0127] Due to the difference in polarity between the basic medium and the used oil, microwave irradiation will selectively heat the droplets of the basic medium efficiently and rapidly. These droplets are thus likely to explode by superheating into smaller droplets, promoting exchange and reaction, and this with a small amount of energy.

[0128] When contact is carried out discontinuously (in batch mode), in the reaction zone, the basic medium forms a lower phase and the used oil forms an upper phase. It is then preferable to irradiate the basic medium from a position above the lower phase, in order to promote heating of the basic medium near the interface with the upper phase and mixing with the latter. In particular, when the basic medium begins to boil near its interface with the used oil, droplets of the basic medium are projected into the used oil and explode inside the used oil causing agitation of the reaction medium and promoting the reaction.

[0129] By way of example, devices sold by the companies Sairem or Tomocon can be used to implement step (a).

[0130] According to the invention, the used oil to be treated is brought into contact with a basic medium comprising a basic compound in a polar solvent chosen from (i) water, (ii) a polar solvent comprising an alcohol function and / or an ether function, and mixtures thereof.

[0131] Advantageously, the quantity of basic compound used can be from 0.1 to 50% by mass, preferably from 0.1 to 15% by mass, more preferably from 1 to 15% by mass, even more preferably from 1 to 10% by mass, in particular from 1 to 5% by mass, relative to the total mass of the used oil treated.

[0132] The basic compound may comprise an oxide, hydroxide, bicarbonate, or alkoxide of an alkali metal cation or an alkaline earth metal cation, or a hydroxide or bicarbonate of a quaternary ammonium cation, for example of a tetramethylammonium (TMA+), tetraethylammonium (TEA+), tetrapropylammonium (TPA+), tetrabutylammonium (TBA+) cation, alone or in mixture.

[0133] The basic compound can, for example, be chosen from LiOH, NaOH, CsOH, Ba(OH)2, Na2O, KOH, K2O, CaO, Ca(OH)2, MgO, Mg(OH)2, EtONa, MeONa, NH4OH, TEAOH, TBAOH, TMAOH, and mixtures thereof. Their concentrations will be limited, in particular, by their solubilities in the chosen solvents.

[0134] In the preferred embodiment, the basic compound may comprise an oxide or hydroxide of an alkali metal cation or an alkaline earth metal cation, alone or in mixture, preferably a hydroxide of an alkali metal cation or an alkaline earth metal cation.

[0135] A preferred basic compound may be selected from NaOH, KOH and their mixtures, advantageously in a polar solvent selected from water and / or methanol.

[0136] The basic compound can be added to the used oil in suspension or in solution in the polar solvent.

[0137] Polar solvents, due to their ability to be polarized, are capable of absorbing microwaves, which increases their temperature. The ability of a material to be polarized can be expressed by the electrical permittivity (denoted e*) of the material, which is a complex number having a real part and an imaginary part usually expressed by the equation e*=e'-je”, where e': real permittivity (F / m), e”: imaginary permittivity (F / m), e*: complex permittivity (F / m).

[0138] The delta tangent (δ), or loss tangent, or loss factor, is the dissipation factor of the sample, or the efficiency with which microwave energy is converted into thermal energy. This delta angle, or loss angle, corresponds to The angle at which the material is out of phase with respect to the electric field. The tangent parameter delta thus represents the capacity of a substance to convert electromagnetic energy into heat at a given frequency and temperature. It is defined as the ratio of the imaginary and real parts of the permittivity: tan δ = δ' / ε'.

[0139] The real permittivity is considered to be in phase with the alternating electric current, and the imaginary permittivity represents the phase lag, that is, the tangent of the angle between the sum of the two parts (complex permittivity). The real permittivity is equal to the imaginary part divided by the real part. The loss tangent (tan d) can be used to represent the fraction of stored energy lost per oscillation period of the field.

[0140] The choice of the polar solvent can thus be made according to the loss tangent of this solvent at the microwave frequency used in the process, the solvent having the highest loss tangent value being able to be heated the fastest, which makes it possible to reduce the contact time.

[0141] Furthermore, the relationship between the dielectric properties and the intensity of the microwave power within the product is characterized by the penetration depth. The penetration depth with respect to microwave power is defined as the distance within the product at which the incident power is reduced to 1 / e (e = 2.7183) of its value at the surface; that is, approximately 65% ​​of the incident power is reduced between the surface and this distance. When the material absorbs very little, it is considered transparent; this is the case, for example, with polyethylene and polystyrene. In general, the penetration depth decreases as the frequency increases. Temperature also plays a role. In the case of water, at a frequency of 2.45 GHz, the penetration depth is 2.88 cm at room temperature and increases to 55 mm at 100 °C. At a frequency of 915 MHz, the water penetration depth is 76.51 cm at room temperature.Furthermore, for a given solvent at a given frequency, the penetration depth will also vary depending on its basic compound content. This penetration depth is generally greater when the basic compound concentration decreases. In addition, the density of the basic medium increases with its basic compound concentration, which can make contact more difficult. It may therefore be advantageous to limit the concentration of the basic compound in the basic medium (i.e., to use a more dilute basic medium). It may then be preferable to increase the volume of basic medium used.

[0142] It is thus understood that a person skilled in the art can choose the microwave frequency according to the depth of penetration of the basic medium considered and the dimensions of the reaction zone.

[0143] According to one embodiment, the used oil has a tangent coefficient delta (δ) low, for example less than 0.1, preferably less than 0.05 and more preferably less than 0.01.

[0144] The polar solvent used in the present invention is selected from (i) water, (ii) a polar solvent comprising an alcohol function and / or an ether function, and mixtures thereof.

[0145] When the polar solvent includes an alcohol functional group, it is preferably a primary or secondary alcohol, more preferably a primary alcohol, for example methanol. This can further reduce side reactions.

[0146] A polar solvent comprising an alcohol functional group and / or an ether functional group may advantageously be chosen from: - alcohols in the C1 to C4 groups, preferably methanol, ethanol, propan-l-ol, propan-2-ol, butan-l-ol, butan-2-ol, 2-methylpropan-l-ol, ethylene glycol, propylene glycol, and more preferably alcohols in the C1-C3 groups, and in particular primary alcohols, for example methanol, - alcohols comprising an ether function, preferably glycol ethers such as polyethylene glycol (PEG), tetraethylene glycol, polypropylene glycol, for example a PEG with an average molar mass of 200g / mol, more preferably diethylene glycol, triethylene glycol, polyethylene glycol, - cyclic ethers, preferably tetrahydrofuran, 2-methyltetrahydrofuran, cyclopentylmethyl ether, tetrahydropyran, 1,4-dioxane, eucalyptol - and their mixtures.

[0147] Preferably, the polar solvent can be chosen from water and / or an alcohol, in particular a C1-C3 or C1-C4 alcohol, optionally mixed with a cyclic ether to improve the homogeneity of the solvent mixture.

[0148] Advantageously, the basic compound can be added in step (a) in solution or in suspension in the polar solvent, and the content of the basic compound in the polar solvent can be from 0.1 to 50% by mass, preferably from 1% to 30% by mass, more preferably from 5 to 25% by mass.

[0149] When the solvent is water, it may advantageously have a pH greater than 7, for example from 7.1 up to a pH approaching the saturation of the compound in water, preferably from 8 to 14, more preferably from 9 to 14, or within any range defined by two of these limits. Preferably, a pH greater than 10 or greater than 12 is chosen, more preferably a pH of at least 12.5.

[0150] The conditions for implementing step (a) may nevertheless advantageously allow the amount of basic compound used to be reduced.

[0151] The volume ratio of the basic medium / composition, i.e. the volume ratio of the mixture (basic compound + polar solvent) / composition, may be from 0.1 / 99.9 to 80 / 20, preferably from 1 / 99 to 60 / 40, more preferably from 5 / 85 to 50 / 50, even more preferably from 10 / 90 to 45 / 55.

[0152] During step a), the reaction medium, comprising the used oil to be treated and the basic medium, is irradiated by microwaves under conditions effective in heating the basic medium to a temperature at most equal to its boiling point at the pressure applied.

[0153] Thus, in general, the basic medium can be heated to a temperature high enough to vaporize at least part of the solvent, for example, by being heated to a temperature at which solvent vapor bubbles appear, but at most equal to the boiling point of the basic medium, at the pressure applied. This temperature at which vapor bubbles appear corresponds approximately to a temperature 5 to 15 °C lower, for example 10 °C lower, than the boiling point of the polar solvent (taken alone, without a basic compound). Since temperature can only be measured on a more global scale, this phenomenon is due to a temperature gradient between the surface and the core of the solvent or basic solution.

[0154] Thus, advantageously, the basic medium can advantageously be heated to a (minimum) temperature 5 to 15 °C lower than the boiling point of the polar solvent (without the basic compound), for example a minimum temperature 10 °C lower than the boiling point of the polar solvent (without the basic compound).

[0155] It may happen that, at the applied pressure, the polar solvent, or one of its components, decomposes at its boiling point. In this case, it is advantageous to heat the polar solvent to a temperature of maximum stability, namely to the highest possible temperature before decomposition. For example, the temperature can be set 5 to 15 °C, preferably 10 °C, below the decomposition temperature of the polar solvent (taken alone, without any basic compound) at the applied pressure.

[0156] The implementation temperature of step (a) thus depends on the nature of the basic medium. It is typically in the range of 60 to 150 °C, preferably from 65 to 115 °C.

[0157] The conditions implemented during step (a) can be determined by a person skilled in the art by tests and / or modeling, depending on the basic compound, the nature of the polar solvent, the power of the irradiated microwaves, the duration of irradiation, and the basic medium / composition ratio.

[0158] By way of example, these conditions include one or more of the following: - microwave frequencies in the range of 300 MHz to 300 GHz, for example 0.915 GHz, 2.45 GHz, 5.8 GHz, 24 GHz, - a power output between 50 and 1500W, for example between 100 and 900W, - an absolute pressure of 0.05 to 100 bar, preferably from 1 to 50 bar, preferably more at atmospheric pressure, - a contact duration of 1 second to 48 hours, preferably 30 seconds to 2 hours, preferably longer, from 1 minute to 1 hour

[0159] When the contact is continuous, the duration of contact can be between 1 second and one minute, for example between 2 seconds and 30 seconds.

[0160] When contact is performed discontinuously (in batches), the contact time can range from 5 minutes to two hours. In this case, the power used can vary during the process. For example, the power used can be between 600 and 1000 W during the first few minutes, for example, the first 5 minutes, then the power can be reduced to between 50 and 200 W. It can then be used intermittently.

[0161] When the basic medium reaches a temperature at most equal to its boiling point at the applied pressure, the solvent vapor bubbles formed in the medium increase the contact surface area between the used oil and the basic compound, thus promoting the treatment. Since microwave irradiation heating is rapid and localized, the temperature of the reaction medium can remain relatively low during the contact time, for example below 150 °C, or even below 130 °C, for example on the order of 100 °C, which considerably limits side reactions.

[0162] Preferably, during contact, the reaction medium or a contact zone can be maintained at a target temperature depending on the irradiation power and / or duration. This target temperature can be chosen from the range of 60 to 150 °C.

[0163] This control can be achieved by placing a thermocouple inside the reaction zone and regulating the irradiation power and / or the duration of irradiation so as to maintain the desired temperature inside the reaction zone.

[0164] Alternatively or in combination, the control can be achieved by measuring the incident microwave power and the microwave power reflected by the reaction medium, and by regulating the incident microwave power and / or the irradiation time so as to maintain a reflected microwave power / microwave power incident at a target ratio for which the reaction medium, or a reaction contact zone, is at the target temperature. This target ratio can be determined beforehand by tests.

[0165] For example, a high irradiation power can be applied at the beginning of the contact, and then, once the target temperature is reached, this power can be reduced. The reaction medium can then be irradiated intermittently. Advantageously, the ratio of basic medium to composition can be as high as possible, which can make it possible to reduce the power and / or duration of irradiation to reach the desired temperature, particularly when the concentration of the basic compound in the basic medium is low.

[0166] The product resulting from the contact, which thus includes the modified used oil, can then be separated (step (b)), and possibly further treated.

[0167] Step (b) may be preceded or followed by a solids separation step by (i) filtration, (ii) centrifugation, (iii) hydrocyclone, or (iv) a combination of two or three of these steps. This solids separation step may facilitate phase separation in step (b) by removing all or part of the solids present in the product from step (a).

[0168] The separation of step (b) can be carried out by (i) washing with a polar solvent, (ii) distillation, or (iii) by a combination of these steps (i), (ii).

[0169] This step makes it possible to separate a phase containing the purified used oil having a reduced content of heteroatoms, and in particular at least of silicon, and advantageously a reduced content of other heteroatoms, and in particular of chlorine, nitrogen, oxygen.

[0170] Step (b) may include a washing step (i) to recover a phase containing the purified used oil and a phase containing the solvent used for washing, salt and impurities.

[0171] In other words, at the exit of the washing step, these phases are recovered separately, for example following a liquid / liquid separation (centrifugation and / or decantation and / or other) carried out at the end of the washing step.

[0172] This step (i) makes it possible to remove impurities containing heteroatoms, and in particular silicon, present in the effluent exiting step (b) by solubilizing them in a polar solvent (water or an organic solvent).

[0173] The solvent may be a polar solvent selected from (i) water, (ii) a polar solvent comprising an alcohol function and / or an ether function, (iii) a solvent immiscible with the product of contacting, and mixtures thereof.

[0174] A polar solvent comprising an alcohol and / or an ether functional group is as defined in step (a). The same solvent as that used in step (a) may or may not be used.

[0175] A usable immiscible polar solvent is described for example in the optional pretreatment step.

[0176] In a preferred embodiment, the polar solvent is chosen by water or an alcohol, preferably a C1-C3 alcohol.

[0177] The water used may have an acidic pH (pH<7), basic pH (pH >7) or neutral pH (pH=7), preferably a neutral pH.

[0178] In one embodiment, the water used has an acidic or neutral pH. In particular, the water used does not contain any basic compound and, specifically, does not contain any basic compound comprising an alkali metal or alkaline earth metal cation.

[0179] An acidic pH can be obtained by adding one or more organic or inorganic acids. Examples are given with reference to washing (ii) of the optional pretreatment step. Preferably, the water can have a pH of 0.1 to 6.9.

[0180] A basic pH can be obtained by adding a basic compound, for example those used in step a). Preferably, the water can have a pH of 7.1 to 14.

[0181] Step (b) can be carried out at a temperature of 10 °C to 120 °C, preferably from 15 °C to 95 °C, more preferably from 15 °C to 80 °C, or within any range defined by any two of these limits, advantageously without external heating. Step (b) is typically carried out at atmospheric pressure.

[0182] During step (b), the polar solvent / effluent volume ratio can be from 1 / 99 to 90 / 10, from 20 / 80 to 80 / 20, from 30 / 70 to 70 / 30, from 35 / 65 to 65 / 35, from 35 / 65 to 60 / 40, from 40 / 60 to 60 / 40, or in any interval defined by any two of the aforementioned bounds.

[0183] Step (b)(i) may include, or consist of, contacting the effluent from step (a) with a polar solvent by any means known in the prior art.

[0184] For example, the effluent from step (a) and the polar solvent can be introduced into tanks, reactors, or mixers commonly used in the industry, and the two components can be mixed. Contacting may involve vigorous agitation of the two components by a mixing device. For example, the two components may be mixed together by stirring or shaking. Alternatively, contacting may be carried out in a chamber in which the two components flow in countercurrents, for example, in contact columns with suitable packing to increase contact between the treated waste oil phase and the polar solvent. Alternatively, contacting may be carried out in a static mixer in co-current mode or in a cavitation section.

[0185] This contact may occur more than once, particularly under the conditions described above. For example, two or more washes may be carried out, for example two to four washes.

[0186] The washing step (b)(i) can be carried out continuously or in batch.

[0187] Step (b) may include a distillation step (ii). A person skilled in the art will know Implement this step under suitable conditions to recover the purified used oil. Distillation step (ii) can be carried out at atmospheric pressure or under reduced pressure, preferably at atmospheric pressure. This step can be carried out in a distillation column or similar equipment.

[0188] Step (b) may include one or more of steps (i) to (ii) depending on the desired separation objective. In preferred embodiments, step (b) may include: - at least one washing step (i), optionally followed by at least one distillation step (ii), or - at least one distillation step (ii), optionally followed by at least one washing step (i).

[0189] The product resulting from the contact of step a) separated in step b) thus forms a modified composition having a reduced content of heteroatoms.

[0190] The sequence of steps (a) and (b) can make it possible to eliminate at least 25% by mass of its initial value, in particular at least 30%, advantageously at least 40%, preferably at least 50% of its initial value, notably without having to heat the used oil to be treated or at a moderate temperature. Steps (a) and (b) may optionally be repeated in order to further reduce the silicon content, and possibly also the content of other heteroatoms.

[0191] The process may also include a purification step (c) by passing over a solid adsorbent. This is thus a trapping step.

[0192] During this step (c), the modified used oil from step (b) can be purified by passing over a solid adsorbent in order to reduce the content of at least one element among F, Cl, Br, I, O, N, S, Mo, Zn, Ni, Si, P, Fe, Ca, Na, K, and Mg and / or the water content.

[0193] Typically, the modified used oil of step (b) may be contacted with silica gel, clays, alkali or alkaline earth metal oxide, iron oxide, ion exchange resins, activated carbon, activated aluminum oxide, molecular sieves, alkali oxide and / or porous supports containing modified or unmodified double lamellar hydroxide and silica gel, or any mixture thereof, to trap silicon and / or metals and / or phosphorus and / or halogenates.

[0194] The adsorbent can be operated in regenerative or non-regenerative mode, at a temperature below 400°C, preferably below 100°C, more preferably below 60°C, or even at room temperature, for example chosen from: (i) silica gel, (ii) clay, (iii) crushed clay, (iv) apatite, (v) hydroxyapatite and their combinations, (vi) alumina, for example, alumina obtained by boehmite precipitation, calcined alumina such as Sasol's Ceralox®, (vii) boehmite, (viii) bayerite, (ix) hydrotalcite, (x) spinel such as Sasol's Pural® or Puralox®, (xi) promoted alumina, for example, BASF's Selexsorb®, acid-promoted alumina, alumina promoted by a zeolite and / or by a metal such as Ni, Co, Mo, or a combination of at least two among them, (xii) an acid-treated clay such as Clariant's Tonsil®, (xiii) a molecular sieve in the form of an aluminosilicate containing an alkali or alkaline earth cation, for example 3A, 4A, 5A, 13X sieves,for example marketed under the brand name Siliporite ® of Ceca, (xiv) a zeolite, (xv) an activated carbon, or a combination of at least two adsorbents, the adsorbent or at least two adsorbents retaining at least 20% by weight, preferably at least 50% by weight of at least one element among F, Cl, Br, I, O, N, S, Mo, Zn, Ni, Si, P, Fe, Ca, Na, K, and Mg and / or water.

[0195] According to a preferred embodiment, the adsorbent is regenerable, has a specific surface area of ​​at least 200 m2 / g and is operated, for example in a fixed bed reactor, at a temperature below 100°C, for example from ambient temperature to 100°C, and / or a WH of 0.1 to 10 h-1 and / or at a pressure of 1 to 90 bar in the presence of H2 or in the absence of H2.

[0196] The purification step (iii) on adsorbent can be carried out continuously or in batch, in one or more reactors, such as fixed bed reactors, fluidized bed reactors or any other type of suitable reactor or device.

[0197] Use of purified used oil obtained by the process

[0198] Advantageously, as mentioned previously, the regenerated oil obtained at the end of step (b) of the process of the invention has a significantly reduced silicon content compared to the used oil before the treatment according to the invention introduced in step (a).

[0199] Advantageously, the silicon content in the purified lubricating oil at the end of step (b) is strictly less than 25 ppm, in particular less than or equal to 20 ppm, in particular less than or equal to 11 ppm.

[0200] The re-refined lubricating oil recovered at the end of the process according to the invention, having a very low silicon content, is suitable as a base oil for the formulation of lubricants, in particular lubricants for systems of mobile or industrial system motors, just like a virgin base oil, without requiring further purification steps.

[0201] Advantageously, the lubricating oil recovered at the end of step (b) thus has properties substantially comparable to those of virgin oils and in particular meets the quality standards of base oils.

[0202] According to a particular embodiment, the purified lubricating oil obtained from the process of the invention can be used as a base oil to formulate a new lubricating composition.

[0203] The invention thus relates, according to another of its aspects, to a process or method for preparing a new lubricating composition, comprising at least the following steps: (i) recover a purified lubricating oil from the processing of a lubricating oil possibly at least partially re-refined by a process according to the invention, as detailed above; (ii) optionally, mix said purified lubricating oil from step (i) with one or more other lubricating oils; and (iii) supplement said purified lubricating oil from step (i) or the mixture of lubricating oils from step (ii), with at least one additive.

[0204] The additive(s) may be of any type suitable for use in a lubricant and chosen according to the intended use of the lubricant.

[0205] The regenerated and purified base oil can be used alone or mixed with one or more other lubricating oils, in particular with one or more virgin base oils (i.e. newly refined lubricating oils that have never been used in lubricants), with one or more other base oils regenerated and purified by a process according to the invention or with one or more regenerated lubricating oils from known re-refining treatments.

[0206] The regenerated and purified base oil can be used to formulate lubricants for the lubrication of various mechanical systems.

[0207] According to one embodiment, the regenerated and purified base oil can be used to formulate lubricants 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 even marine vehicles.

[0208] According to another embodiment, the regenerated and purified base oil can be used to formulate lubricants for the lubrication of an industrial system, in particular a "stationary" one, i.e. including, but not limited to, turbines, compressors, hydraulic systems, gears, or even forming or cutting machines.

[0209] In particular, it can be used for the lubrication of bearings, gears, or various mechanical parts of an engine. In particular, the re-refined and purified base oil according to the invention can be used to formulate lubricants for drive systems, such as the transmission or the engine in a drive system, especially for heavy or light vehicles or marine engines.

[0210] Additives can be introduced individually and / or in the form of mixtures like those already commercially available for commercial formulations of lubricants for vehicle engines, with a level of performance as defined by ACEA (European Automobile Manufacturers' Association) and / or API (American Petroleum Institute), known to those skilled in the art.

[0211] These additives may in particular be selected from friction modifier additives, extreme pressure additives, anti-wear additives, detergents, antioxidants, viscosity index (VI) improvers, pour point lowering (PPD) agents, dispersants, antifoaming agents, thickeners and mixtures thereof.

[0212] These additives can be added to a regenerated and purified base oil according to the invention in an appropriate quantity determined by a person skilled in the art.

[0213] The invention will now be described by means of the following examples, given by way of illustration and not limitation of the invention.

[0214] Implementation methods

[0215] This disclosure relates to various embodiments as presented below: Embodiment 1: A process for purifying used oil, possibly at least partially re-refined, comprising: a. contacting said used oil with a basic medium comprising a basic compound in a polar solvent selected from (i) water, (ii) a polar solvent comprising an alcohol and / or an ether function, and mixtures thereof, and irradiating the reaction medium with microwaves under conditions effective in heating the basic medium to a temperature not exceeding its boiling point at the pressure applied, b. separation between the basic compound and the product resulting from contacting said used oil.

[0216] Embodiment 2: Purification process according to embodiment 1, characterized in that the used oil, optionally at least partially re-refined, comprises at least one of the following characteristics: - said used oil contains a Silicon content strictly greater than 10 ppm, in particular greater than or equal to 15 ppm, more particularly greater than or equal to 20 ppm, in particular greater than or equal to 30 ppm, in particular up to 300 ppm, in particular up to 290 ppm, for example up to 285 ppm, - prior to step (a) or subsequent to step (b), said used oil is subjected to at least one treatment step selected from steps of dehydration, distillation, filtration, hydrogenation, liquid / liquid extraction, transesterification, selective neutralization, decantation and / or passing of the used oil over an adsorbent material, in particular over activated carbon.

[0217] Embodiment 3: Purification process according to embodiment 1 or 2, characterized in that step (a) comprises one or more of the following features: - step (a) is carried out in the presence of 0.1 to 50% by mass of basic compound relative to the total mass of said composition, preferably from 0.1 to 15% by mass, more preferably from 1 to 15% by mass, even more preferably from 1 to 10% by mass, - the ratio by mass of basic medium to composition is 0.1 / 99.9 to 80 / 20, preferably 1 / 99 to 60 / 40, more preferably 5 / 85 to 50 / 50, and even more preferably 10 / 90 to 45 / 55. - the basic compound is chosen from LiOH, NaOH, CsOH, Ba(OH)2, Na2O, KOH, K2O, CaO, Ca(OH)2, MgO, Mg(OH)2, NH4OH, TMAOH, TEAOH, TBAOH, MeONa, EtONa and mixtures thereof - the contact is made for a duration of 1 second to 48 hours, preferably from 30 seconds to 2 hours, more preferably from 1 minute to 1 hour, - the polar solvent is chosen from (i) water, (ii) alcohols in the Cl to C4 range, preferably methanol, ethanol, propan-l-ol, propan-2-ol, butan-l-ol, butan-2-ol, 2-methylpropan-l-ol, ethylene glycol, propylene glycol, (iii) alcohols comprising an ether function, preferably glycol ethers such as polyethylene glycol, polypropylene glycol, tetraethylene glycol, diethylene glycol, triethylene glycol, (iv) cyclic ethers, preferably tetrahydrofuran, 2-methyltetrahydrofuran, cyclopentylmethyl ether, tetrahydropyran, 1,4-dioxane, eucalyptol, and mixtures thereof - the contact is made at an absolute pressure of 0.05 to 100 bars, preferably from 1 to 50 bars.

[0218] Embodiment 4: Purification process according to one of embodiments 1 to 3, characterized in that the contact is carried out continuously in a reaction zone in which the basic medium and the used oil flow in co-current or counter-current, the basic medium being introduced in the form of droplets.

[0219] Embodiment 5: Purification process according to one of embodiments 1 to 3, characterized in that the contacting takes place in a reaction zone in which the basic medium forms a lower phase and the used oil forms an upper phase, and the microwaves irradiate the basic medium from a position located above the lower phase.

[0220] Embodiment 6: Purification process according to one of the preceding embodiments, characterized in that during contacting, the reaction medium or a reaction contact zone is maintained at a temperature not exceeding the boiling point of the basic medium at the pressure applied, by adjusting an irradiation power and / or an irradiation time.

[0221] Embodiment 7: Purification process according to one of the preceding embodiments, characterized in that the temperature of the basic medium is chosen in a temperature range from 60°C to 150°C.

[0222] Embodiment 8: Purification process according to one of the preceding embodiments, characterized in that step (b) is preceded or followed by a step of separation of solids by (i) filtration, (ii) centrifugation, (iii) hydrocyclone or (iv) a combination of two or more of these steps.

[0223] Embodiment 9: Purification process according to one of the preceding embodiments, characterized in that the separation of step (b) is carried out by (i) washing with a polar solvent, (ii) distillation, or (iii) by a combination of these steps (i), (ii).

[0224] Embodiment 10: Purification process according to the preceding embodiment, characterized in that the washing step (b)(i) is carried out with water at neutral, basic or acidic pH, or with an alcohol.

[0225] Embodiment 11: Purification process according to one of the preceding embodiments, characterized in that the product from the separate contact in step (b) undergoes a purification step (c) by passing over a solid adsorbent in order to reduce the content of at least one element among F, Cl, Br, I, O, N, S, Mo, Zn, Ni, Si, P, Fe, Ca, Na, K, and Mg and / or the water content.

[0226] Embodiment 12: Use of a purification process as defined according to one of the preceding embodiments, to reduce the silicon content of a lubricating oil optionally at least partially re-refined.

[0227] Embodiment 13: Use according to the preceding embodiment, to reduce the quantity of silicon to a content strictly less than 25 ppm, in particular less than or equal to 20 ppm, in particular less than or equal to 11 ppm.

[0228] Embodiment 14: A method for preparing a lubricating composition comprising at least the steps of: (i) purify a used oil possibly at least partially re-refined by a purification process as defined according to one of embodiments 1 to 11; (ii) optionally, mix said purified lubricating oil from step (i) with one or more other lubricating oils, in particular selected from virgin base oils, regenerated lubricating oils purified by a purification process as defined in any one of embodiments 1 to 11; and lubricating oils that are at least partially re-refined; and (iii) supplement said purified lubricating oil from step (i) or the mixture of lubricating oils from step (ii), with at least one additive, preferably selected from friction modifiers, extreme pressure additives, anti-wear additives, detergents, antioxidants, viscosity index (VI) improvers, pour point depressants (PPD) additives, dispersants, antifoaming agents, thickeners and mixtures thereof.

[0229] Embodiment 15: Use of a purification process as defined according to one of embodiments 1 to 11 to improve the eco-performance of lubricating compositions, the eco-performance preferably being characterized by: - ​​minimizing the carbon footprint of the lubricating compositions, - improving the recyclability of the lubricating compositions, and / or - reducing the use of fossil resources. Examples

[0230] The silicon content of lubricating oils is determined by an analytical method based on X-ray fluorescence (XRF) after filtering the sample.

[0231] The device used is the MINILABOTRON 2000 from Sairem. It has a maximum power of 2 kW at 2.45 GHz.

[0232] The two lubricating oils treated are commercially available regenerated (or re-refined) lubricating oils: oils A and B. These regenerated oils contain, in particular, silicon, which is to be removed, and absorb very little microwave radiation (Tanô = 0.0050 for A and 0.0047 for B). They are subjected to a purification process according to this disclosure, under the conditions below.

[0233] Oils A and B have the following properties: Parameters Oil A Oil B KV40 [mmVs] 33.0 13.91 KV100 [mmVs] 5.9 3.319 Viscosity index 122 109 Density (kg / m³) 849.3 843.8 Volatility 7.2 32.8 Air point (°C) 236 182 Thermal conductivity 40°C (mW spls s) 131 3 131.99 Sulfur content (%) 0.11 27 Aromatic content (%) 7.2 ND

[0234] The regenerated lubricating oils, before purification, and after purification and extraction as described above, are analyzed to measure silicon content, following the measurement protocol described above.

[0235] The tests are carried out in batch on 300g of oil in a flask. Sodium hydroxide solutions were tested at different ratios and concentrations (10 to 25%) and at different ratios to oil (3 to 5%).

[0236] The microwave exposure time varied from 10 to 30 minutes. All tests were carried out under atmospheric pressure.

[0237] Before each test, nitrogen was injected into the vial to eliminate oxygen and avoid any risk of fire.

[0238] The power applied to the batch reactions starts at 800W until vapor bubbles appear in the solution. The power is then reduced to between 150 and 200W and the irradiation is then carried out discontinuously.

[0239] The mechanical agitation is 300 rpm. The Minilabotron detects the percentage of irradiation absorbed and it is possible to program the irradiation power according to the absorption or as a fixed value.

[0240] The results are presented in the following table

[0241] [Tables2] Today, the tested concentration of the solution... NaOH used (% by weight) Quantity of NaOH added (% by weight) I (mtn) Initial Si (ppm) Final St (ppm) % reduction of Si Oil A 25 3 10 30 15: 50 Oil A 25 Q. 20 30 15 50 Oil A 25 5- 20 30 16 47 Today, A 10 4 30 30 14 53 Oil B 25 S 20 32 13 59 Oil B 25 3 10 32 11 66 Oil B 25 5' 20 32 16 50 Oil B 10 4 30 32 20 38

[0242] The purification treatment significantly reduced the silicon content in both regenerated oils. Very low levels, below 20 ppm, or even below 15 ppm, can be achieved in a very short time and with minimal energy consumption. The present process therefore offers a very good compromise between energy efficiency and silicon reduction.

Claims

Demands

1. A process for purifying a used oil, optionally at least partially re-refined, comprising: a. contacting said used oil with a basic medium comprising a basic compound in a polar solvent selected from (i) water, (ii) a polar solvent comprising an alcohol and / or an ether function, and mixtures thereof, and irradiating the reaction medium with microwaves under conditions effective in heating the basic medium to a temperature at most equal to its boiling point at the pressure applied, b. separating the basic compound from the product obtained from contacting said used oil.

2. A purification process according to claim 1, characterized in that the used oil, optionally at least partially re-refined, comprises at least one of the following characteristics: - said used oil contains a Silicon content strictly greater than 10 ppm, in particular greater than or equal to 15 ppm, more particularly greater than or equal to 20 ppm, in particular greater than or equal to 30 ppm, in particular up to 300 ppm, in particular up to 290 ppm, for example up to 285 ppm, - prior to step (a) or subsequent to step (b), said used oil is subjected to at least one treatment step selected from steps of dehydration, distillation, filtration, hydrogenation, liquid / liquid extraction, transesterification, selective neutralization, decantation and / or passing the used oil over an adsorbent material, in particular over activated carbon.

3. A purification process according to claim 1 or 2, characterized in that step (a) comprises one or more of the following features: - step (a) is carried out in the presence of 0.1 to 50% by mass of basic compound relative to the total mass of said composition, preferably from 0.1 to 15% by mass, more preferably from 1 to 15% by mass, even more preferably from 1 to 10% by mass, - The ratio of base medium to composition is 0.1 / 99.9 to 80 / 20, preferably 1 / 99 to 60 / 40, more preferably 5 / 85 to 50 / 50, and even more preferably 10 / 90 to 45 / 55, - The basic compound is chosen from LiOH, NaOH, CsOH, Ba(OH)2, Na2O, KOH, K2O, CaO, Ca(OH)2, MgO, Mg(OH)2, NH4OH, TMAOH, TEAOH, TBAOH, MeONa, EtONa and mixtures thereof, - Contact is made for a duration of 1 second to 48 hours, preferably 30 seconds to 2 hours, more preferably 1 minute to 1 hour, - The polar solvent is chosen from (i) water, (ii) alcohols from C1 to C4, preferably methanol, ethanol, propan-l-ol, propan-2-ol, butan-l-ol, butan-2-ol, 2-methylpropan-l-ol, ethylene glycol, propylene glycol, (iii) alcohols comprising an ether function, preferably glycol ethers such as polyethylene glycol, polypropylene glycol, tetraethylene glycol, diethylene glycol, triethylene glycol,(iv) cyclic ethers, preferably tetrahydrofuran, 2-methyltetrahydrofuran, cyclopentylmethyl ether, tetrahydropyran, 1,4-dioxane, eucalyptol, and mixtures thereof - contact is carried out at an absolute pressure of 0.05 to 100 bar, preferably 1 to 50 bar.

4. A purification process according to any one of claims 1 to 3, characterized in that the contact is carried out continuously in a reaction zone in which the basic medium and the used oil flow in co-current or counter-current, the basic medium being introduced in the form of droplets.

5. A purification process according to any one of claims 1 to 3, characterized in that the contacting takes place in a reaction zone in which the basic medium forms a lower phase and the used oil forms an upper phase, and the microwaves irradiate the basic medium from a position located above the lower phase.

6. A purification process according to any one of the preceding claims, characterized in that during contacting, the reaction medium or a reaction contact zone is maintained at a temperature not exceeding the boiling point of the basic medium at the pressure applied, by adjusting an irradiation power and / or an irradiation time.

7. A purification process according to any one of the preceding claims, characterized in that the temperature of the basic medium is chosen in a temperature range from 60°C to 150°C.

8. A purification process according to any one of the preceding claims, characterized in that step (b) is preceded or followed by a step of separating solids by (i) filtration, (ii) centrifugation, (iii) hydrocyclone or (iv) a combination of two or more of these steps.

9. A purification process according to any one of the preceding claims, characterized in that the separation of step (b) is carried out by (i) washing with a polar solvent, (ii) distillation, or (iii) by a combination of these steps (i), (ii).

10. A purification process according to the preceding claim, characterized in that the washing step (b)(i) is carried out with water at neutral, basic or acidic pH, or with an alcohol.

11. A purification process according to any one of the preceding claims, characterized in that the product resulting from the separate contact in step (b) undergoes a purification step (c) by passing over a solid adsorbent in order to reduce the content of at least one element among F, Cl, Br, I, O, N, S, Mo, Zn, Ni, Si, P, Fe, Ca, Na, K, and Mg and / or the water content.

12. Use of a purification process as defined according to any one of claims 1 to 11, to reduce the silicon content of a lubricating oil optionally at least partially re-refined.

13. Use according to the preceding claim, to reduce the amount of silicon to a content strictly less than 25 ppm, in particular less than or equal to 20 ppm, in particular less than or equal to 11 ppm.

14. A process for preparing a lubricating composition comprising at least the steps of: (i) purifying a used oil, optionally at least partially re-refined, by a purification process as defined in any one of claims 1 to 11; (ii) optionally, mixing said purified lubricating oil from step (i) with one or more other lubricating oils, in particular selected from virgin base oils, regenerated lubricating oils, and lubricating oils purified by a purification process such as defined according to any one of claims 1 to 11; and lubricating oils at least partly re-refined; and (iii) supplementing said purified lubricating oil from step (i) or the mixture of lubricating oils from step (ii), with at least one additive, preferably selected from friction modifiers, extreme pressure additives, anti-wear additives, detergents, antioxidants, viscosity index (VI) improvers, pour point depressants (PPD) additives, dispersants, antifoaming agents, thickeners and mixtures thereof.

15. Use of a purification process as defined according to any one of claims 1 to 11 to improve the eco-performance of lubricating compositions, eco-performance preferably being characterized by: - ​​minimizing the carbon footprint of lubricating compositions, - improving the recyclability of lubricating compositions, and / or - reducing the use of fossil resources.