FR3130826A1 - Method for purifying at least partly re-refined lubricating oils - Google Patents

Abstract

Method for purifying at least partly re-refined lubricating oils The present application relates to a method for purifying an at least partly re-refined lubricating oil, comprising at least the following steps:(a) contacting said lubricating oil at least partly re-refined with from 0.1% to 50% by weight of at least one strong base comprising an alkali or alkaline earth metal cation; and(b) recovering said purified lubricating oil by separating the strong base comprising the alkali metal or alkaline earth metal cation from the product obtained at the end of step (a). It also relates to the use of said purification process, to reduce the silicon content in an at least partly re-refined lubricating oil as well as a process for preparing a lubricating composition from at least one purified lubricating oil. according to the purification process according to the invention.

Description

Method for purifying at least partly re-refined lubricating oils

The present invention relates to the field of the re-refining or regeneration of used lubricating compositions. More specifically, the present invention relates to a method for purifying an at least partly re-refined lubricating oil, allowing access to a lubricating oil having in particular a reduced silicon content, suitable for its use as a base oil for the formulation of a new lubricating composition.

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

During their use, the 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 lubricating compositions, external pollutants, such as dust, elements emanating from the wear of the parts with which the oil is in contact during its use or even fuel fractions from the engine.

These various undesirable elements are liable to have a negative impact on the properties of the lubricating composition which thus becomes, after use, a so-called “used”, “worn” or even “degraded” lubricating composition. This is why lubricating compositions need to be replaced after a certain period of use.

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

To do this, the used lubricating compositions are generally subjected to various operations aimed at eliminating the contaminants and other undesirable elements which are present therein, and are thus brought to undergo operations similar to those employed in the field of the refining of petroleum oils. For example, among the many methods proposed for re-refining used lubricating compositions, mention may be made of that described in document EP 0 708 174, and comprising steps of dehydration, distillation under vacuum, extraction using solvent and hydrotreating.

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 comprises passing the lubricating composition used on activated carbon.

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

However, the presence of silicon in the base oils intended for the formulation of lubricants, in particular for the lubrication of mobile or stationary engine systems, in particular of engine lubricants, is undesirable given the wear problems that it can engender.

Consequently, the quantity of re-refined lubricating oils, or even the nature of the re-refined lubricating oils, which can be incorporated for the formulation of lubricating compositions, is limited in order to comply with the specifications required for the lubricant in terms of silicon content. . Consequently, re-refined lubricating oils are generally introduced in limited quantities in favor of new base oils.

There thus 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 exploit these regenerated oils for their use as base oils in the formulation of lubricating compositions.

The present invention aims precisely to overcome the constraint linked to the presence of undesirable elements, such as silicon, in regenerated oils.

It more particularly proposes a new method for purifying lubricating oils which have been at least partly re-refined, advantageously making it possible to reduce the content of undesirable elements, in particular silicon, in order to obtain regenerated and purified oils which can be used as base for the formulation of lubricating compositions.

Thus, the invention relates, according to a first of its aspects, to a process or a method for purifying an at least partly re-refined lubricating oil, said process comprising at least the following steps:
(a) contacting said lubricating oil at least in part re-refined, called "regenerated lubricating oil" with from 0.1% to 50% by mass of at least one strong base comprising an alkali metal cation or alkaline- earthy; And
(b) recovery of said purified lubricating oil by separation of the strong base comprising the alkali or alkaline-earth metal cation from the product obtained at the end of step (a).

Preferably, as detailed in the rest of the text, step (a) of bringing the regenerated lubricating oil into contact with said strong base is carried out in the presence of water and, preferably, step (b) of separation of said strong base is carried out via one or more stages of filtration, distillation, decantation and/or liquid/liquid extraction, preferably liquid/liquid extraction, in particular with water.

Such a process has already been proposed for the purpose of purifying feedstocks containing pyrolysis oils from plastic waste with a view to their use in a steam cracking process, in the applications filed under the numbers FR2104616, FR2104617 and FR2109395.

On the other hand, to the knowledge of the inventors, it has never been proposed to take advantage of this way of purifying plastic pyrolysis oils, to purify partially re-refined lubricating oils, and in particular with a view to lowering the silicon content.

According to the invention, the term “used lubricating composition” (or more simply “used lubricant” or even “used oil”) is intended to denote 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.

A used lubricating composition can come from different sources. In particular, as detailed in the rest of the text, it may be a lubricant that has been used for the lubrication of a motorization system, in particular "mobile", or even for the lubrication of a so-called industrial system, especially "stationary".

It is understood that a used lubricating composition can be a mixture of several used lubricating compositions, coming from the same source or from several different sources.

Due to their origin, used lubricants, particularly engine lubricants, include a number of degradation products derived from the oil itself or from the additives it contains, as well as metal particles, oxides metal and other elements, for example from the engine. A used oil can 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.

Unlike a "used lubricating composition", the expression "new lubricating composition" within the meaning of the invention designates a lubricating composition which has not yet been used for the lubrication of the moving parts of a mechanical system, and who is ready for this use.

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

In other words, an at least partly re-refined lubricating oil is obtained at the end of one or more stages of treatment of a used lubricant, aimed at eliminating, at least partly, a certain number of contaminating elements which are present there, such as dust, water, fuel fractions, metallic elements and other residues resulting from the degradation of the additives present in the lubricant.

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, settling and/or passage of the used lubricant over an adsorbent material, in particular over activated carbon.

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

An at least partly re-refined lubricating oil according to the invention is also distinct from a virgin or new base oil (that is to say a refined base oil), in particular with regard to the silicon content present in the regenerated oil.

In particular, an at least partly re-refined oil used in the treatment method according to the invention may comprise a particularly high silicon content and, in any event, undesirable for the implementation of this regenerated oil. for the formulation of a lubricating composition.

The silicon content of a regenerated lubricating oil used in the purification process according to the invention may in particular be strictly greater than 2 ppm, preferably greater than or equal to 5 ppm, in particular greater than or equal to 10 ppm, plus 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.

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

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 else by mass spectrometry at inductively coupled plasma (ICP-MS).

Advantageously, as illustrated in the examples which follow, the purification process according to the invention of a regenerated lubricating oil makes it possible to significantly reduce the silicon content present in the regenerated oil.

Advantageously, the silicon content initially present in the regenerated lubricating oil can be reduced by at least 50% by weight of its initial value, in particular by at least 60%, advantageously by at least 70%, preferably by at least 80% of its initial value.

Advantageously, in particular whatever 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 10 ppm, in particular less than or equal to 7 ppm, in particular less than or equal to 5 ppm.

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

The invention thus relates, according to another of its aspects, to a process or a method for reducing the silicon content in an at least partly re-refined lubricating oil, said process implementing at least steps (a) and (b) previously defined.

It also relates to the use of at least one purification process according to the invention, implementing at least the aforementioned steps (a) and (b), to reduce the silicon content of a lubricating oil at least in part. re-refined.

It also relates to a process for the preparation of an at least partly re-refined lubricating oil comprising less than 10 ppm, in particular less than 7 ppm, preferably less 5 ppm of silicon, from lubricating oil at least partly re-refined, said method implementing at least steps (a) and (b) defined above.

Furthermore, advantageously, as illustrated in the examples which follow, in addition to significantly reducing the silicon content of the regenerated oil, the process of the invention advantageously makes it possible to reduce the content of other elements which may be considered undesirable, in particular chlorine, nitrogen and/or oxygen. These elements can prove to be undesirable at the level of the lubricant, in particular with regard to the effects of corrosion (for chlorine), modifications of the interfacial properties (for nitrogen) and tendency to oxidation (for oxygen) which they can spawn.

In particular, the process of the invention, in particular in the case where the regenerated oil comprises a high chlorine content, advantageously makes it possible to significantly reduce this content. Such a reduction in the chlorine content is advantageous in view of the undesirable effects of corrosion which may be caused by the hydrogen chloride which may be generated by the residual chlorine present in the lubricating oil.

Advantageously, the chlorine content of a regenerated oil treated according to the invention is less than or equal to 30 ppm, in particular less than or equal to 25 ppm, and more particularly less than or equal to 10 ppm, or even less than or equal to 5 ppm .

The invention thus relates to the use of a purification process according to the invention, implementing at least the aforementioned steps (a) and (b), to reduce the content of silicon, chlorine, oxygen and/or in nitrogen, in particular in silicon and/or in chlorine, more particularly in silicon of an at least partly re-refined lubricating oil.

The regenerated and purified lubricating oil, obtained at the end of the treatment process according to the invention, proves to be particularly suitable, and this without requiring additional purification treatment, for its implementation as a base oil, for example for the purpose of being marketed as is, post-processed in fractions of different viscosities or even formulated with additives to produce a new lubricating composition.

In particular, the method of the invention advantageously makes it possible to overcome the constraint of using regenerated lubricating oils for the formulation of new lubricants, linked to their silicon content.

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

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

The invention relates in particular to a process or a method for preparing a lubricating composition comprising at least the following steps:
(i) purifying an at least partly re-refined lubricating oil by a purification process according to the invention as defined above;
(ii) optionally, mixing said purified lubricating oil from step (i) with one or more other lubricating oils, in particular chosen from virgin base oils, lubricating oils regenerated and purified according to the process of the invention and at least partly re-refined lubricating oils;
(iii) supplementing said purified lubricating oil from step (i) or the mixture of lubricating oils from step (ii), with at least one additive, preferably chosen from friction modifier additives, extreme additives anti-wear additives, detergents, antioxidants, viscosity index improvers, pour point depressants, dispersants, anti-foaming agents, thickeners, and mixtures thereof.

Other characteristics, variants and advantages of the process for purifying at least partly re-refined lubricating oils according to the invention will emerge better on reading the description and the examples which follow, given by way of non-limiting illustration. invention.

The expressions “between … and …”, “ranging from … to …”, “formed from … to …”, and “varying from … to …”, must be understood as limits included, unless otherwise stated.

In the description and the examples, unless otherwise indicated, the percentages are percentages by weight. The percentages are therefore expressed by mass relative to the total mass of the composition.

Claims (12)

Process for purifying an at least partly re-refined lubricating oil, comprising at least the following steps:
(a) bringing said at least partly re-refined lubricating oil into contact with from 0.1% to 50% by mass of at least one strong base comprising an alkali or alkaline-earth metal cation; And
(b) recovery of said purified lubricating oil by separation of the strong base comprising the alkali or alkaline-earth metal cation from the product obtained at the end of step (a). Process according to Claim 1, in which the said at least partly re-refined lubricating oil, implemented in step (a), comes from a used lubricating composition having been subjected to one or more pre-treatment steps chosen from stages of dehydration, distillation, filtration, hydrogenation, liquid/liquid extraction, settling and/or passage of the used lubricant over an adsorbent material, in particular over activated carbon. Process according to any one of Claims 1 or 2, in which the said at least partly re-refined lubricating oil, implemented in step (a), has a silicon content strictly greater than 2 ppm, preferably greater than or equal to to 5 ppm, in particular greater than or equal to 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. Process according to any one of the preceding claims, in which the contacting of the said at least partly re-refined lubricating oil with the said strong base in step (a) is carried out for a period of at least 1 minute, in particular ranging from 1 minute to 48 hours, in particular from 5 minutes to 2 hours, preferably for a period of 20 minutes to 40 minutes, for example approximately 30 minutes. Process according to any one of the preceding claims, in which the contacting of the said at least partly re-refined lubricating oil with the said strong base in step (a), is carried out at a temperature of at most 450°C, in particular at most 400° C., more particularly at most 350° C., for example ranging from 50° C. to 450° C., in particular approximately 225° C., in particular at a pressure ranging from 0.1 at 100 bars, preferably from 1 to 50 bars. Process according to any one of the preceding claims, in which the at least partly re-refined lubricating oil is brought into contact, in step (a), with 0.1% to 40% by mass, preferably 0.5% to 30% by mass, in particular 1.0% to 20% by mass, more particularly 1.0% to 5.0% by mass, of strong base comprising an alkali or alkaline-earth metal cation. A method according to any preceding claim, wherein said strong base comprising an alkali or alkaline earth metal cation is selected from lithium hydroxide, sodium hydroxide, cesium hydroxide, barium dihydroxide , sodium oxide, potassium hydroxide, potassium oxide, calcium oxide, calcium dihydroxide, magnesium oxide, magnesium dihydroxide, and mixtures thereof, preferably is sodium hydroxide. A method according to any preceding claim, wherein said regenerated lubricating oil is contacted in step (a) with said strong base in the presence of water. Process according to any one of the preceding claims, in which step (b) is carried out via one or more stages of filtration, distillation, decantation and/or liquid/liquid extraction, preferably liquid/liquid extraction. liquid, especially with water. Use of a purification process as defined according to any one of Claims 1 to 9, for reducing the silicon content of an at least partly re-refined lubricating oil. Use according to the preceding claim, for reducing the quantity of silicon to a content strictly less than 10 ppm, in particular less than or equal to 7 ppm, more particularly less than or equal to 5 ppm. Process for the preparation of a lubricating composition comprising at least the steps consisting in:
(i) purifying an at least partly re-refined lubricating oil by a purification process as defined in any one of claims 1 to 9;
(ii) optionally, mixing said purified lubricating oil from step (i) with one or more other lubricating oils, in particular chosen from virgin base oils, lubricating oils regenerated and purified by a purification process as defined according to any one of claims 1 to 9; and at least partly re-refined lubricating oils; 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 chosen from friction modifier additives, extreme additives anti-wear additives, detergents, antioxidants, viscosity index (VI) improvers, pour point depressants (PPD), dispersants, antifoaming agents, thickeners and their mixtures.