WO2011161378A1

WO2011161378A1 - Process for purifying a used hydrocarbon-based feedstock

Info

Publication number: WO2011161378A1
Application number: PCT/FR2011/051434
Authority: WO
Inventors: Samuel Mignard; Maurice Born; Dominique Rio
Original assignee: Societe De Conception D'equipements Pour L'environnement Et L'industrie
Priority date: 2010-06-22
Filing date: 2011-06-22
Publication date: 2011-12-29
Also published as: FR2961521B1; EP2585567A1; FR2961521A1; EP2585567B1

Abstract

Process for purifying a hydrocarbon-based feedstock, comprising one or more compounds to be eliminated, which comprises the steps: a) of extracting light compounds present within the feedstock; b) of filtering the compounds to be eliminated, in the presence of a supercritical fluid; c) of treating the feedstock using a conversion agent; d) of separating the purified hydrocarbon-based feedstock.

Description

PROCESS FOR PURIFYING A USED HYDROCARBONIC LOAD

DESCRIPTION

The present invention relates to a process for treating or purifying a hydrocarbon feed comprising pollutant compounds, undesirable or requiring to be removed, in particular to allow the use of the hydrocarbon feedstock thus purified. The invention also relates to the treatment of this charge by means of a transformation agent.

In particular, the process according to the invention can be implemented for the treatment of waste oils, such as motor oils, hydraulic oils, gear oils or industrial oils, and mixtures thereof, in particular to regenerate them. in a lubricating base of commercial quality identical to the original product for a new use. This type of treatment may be referred to as "re-refining or regenerating used oils". The field of the invention is therefore that of the regeneration of hydrocarbon feedstocks, such as used or used oils such as motor oils, hydraulic oils, gear oils or industrial oils, and mixtures thereof.

An oil corresponds, conventionally to a mixture of hydrocarbons also comprising various additives reinforcing the intrinsic properties of this oil or providing additional properties for a specific use. Among the additives commonly used in oils, in particular in motor oils, mention may be made of:

• antioxidant additives whose function is to slow the oxidation of the oil and thus extend its life;

• detergent additives whose function is to keep clean the parts intended to be in contact with the oil;

Dispersant additives, for example alkyl-succimides, which serve to suspend in the oil solid impurities present in the engine oil such as soot, dust, wear metals;

Anti-wear additives contributing to forming a protective film on the surfaces of the parts in contact with said oil, for example organometallic compounds such as zinc alkyl-dithio-phosphates;

Antirust additives, detergents, for example sulfonates or phenolates, viscosity index improvers or anti-foam additives, etc.

In use, the oils are subjected to stresses that will cause their degradation leading to an increase in the contaminant content of said oils, these contaminants may be derived from a degradation of the aforementioned additives, such as antioxidant additives, anti-wear agents; or external pollutants, such as dust; or wear metals emanating from, for example, parts with which the oil is in contact during use; or even fractions of fuel (gas oil or gasoline) more or less oxidized or thermally cracked and which may be in liquid or solid form including soot; or else contaminants related to the storage of used oils in which there are sometimes substances constituting light fractions which are generally water, or chlorinated or petroleum solvents.

This results in a polluted oil with a stronger coloration than the original clean oil, hence the name of black oils in the field of waste oils, in particular because of the presence of oxidation products or cracking fuel. In order to be reusable, the oil must be freed from these contaminants and, to this end, undergoes depollution operations generally similar to those of refining, such as:

A primary treatment intended to eliminate the water and / or the solid elements suspended in the used oil, this treatment being conventionally carried out by summary filtration and / or by decantation;

Operations for separating pollutant compounds dissolved in the used oil, for example by distillation, resulting in a fraction that can be recovered more or less colored and close to the desired base oil;

Finishing operations, essentially to obtain a discolored oil, for example, by adsorption of said oils on activated bleaching grounds or by catalytic hydrogenation.

These refining processes have replaced the older processes using sulfuric acid and which had the major disadvantage of producing large quantities and may be of the order of 20% of extremely polluting acidic sludge. Such methods are for example described in US-4101414.

In addition, other means of separation have been studied to substitute for distillation; in particular the filtration of a used oil which can be achieved by tangential filtration. Such tangential filtration generally involves passing the oil tangentially to the filter surface. The oil passes through the filter thanks to the pressure it exerts on the latter, whereas the colloidal or solid undesirable elements present in the used oil remain mainly in the tangential flow of circulation, thus causing a less clogging of the filter than that which would be obtained if the oil was filtered by frontal filtration. However, in view of the high viscosity of the oils, the rate of passage of the oil through the porosity of the filter is reduced compared to liquids whose viscosity is close to or identical to that of water, which affects the filtration efficiency. To overcome this disadvantage, it is possible to increase the temperature of the viscous liquid, such as an oil, and to pass on a mineral ultrafiltration filter the liquid to be treated, and this at a temperature of up to 350ºC. However, this type of process has drawbacks such as a very high operating temperature which requires precautions because of the flammability of the product to be treated; mechanical stresses applied to the ceramic membranes, these stresses being caused by the differential expansion of the constituent material of the membranes due to the temperature difference induced by the heating during the filtration. In addition, the oxidation of the used oil can modify its composition and make it more viscous.

Another solution may be to add an adjuvant to the oil to be treated, which will make it possible to reduce the viscosity of the liquid to be filtered. This adjuvant may be a liquid organic solvent such as propane, hexane, heptane or any other organic solvent miscible in the oil. It is also possible to use a fluid in the supercritical state, such as carbon dioxide in the supercritical state, as described in the international patent application WO-00 / 521-18. However, these methods can lead to an important transition from undesirable elements in the filtrate through the filter, which is to be avoided.

Other methods of treating used oils are also known.

International Patent Application WO-94/021761 discloses a method of regenerating used lubricating oils in which used oils are filtered to remove solid particles they may contain. Then, these oils are heated and a strong base is added before removing impurities, in particular metals. The purpose of this method is to improve the efficiency on an industrial scale compared to an implementation in the laboratory. This process is also aimed at improving the yield compared to the traditional distillation process.

Nevertheless, this method has the disadvantage of introducing a base in a non-depolluted load; the chemical treatment can not be total without consuming a large amount of base and generate significant amounts of waste.

Patent Application EP-1712608 describes a process for the regeneration of used mineral oils to obtain lubricating bases. This process comprises the demetallization of the oil by means of treatment with an ammonium salt and then a double distillation in the presence of alkali hydroxides of the demetallized oil. This process can be carried out at moderate temperatures in order to preserve the installations used.

This process, essentially chemical, requires a very complex control of the reactions with the ammonium salts; the industrial implementation of such a process remains very problematic.

These known methods are therefore not satisfactory. Thus, the invention provides a process for purifying a hydrocarbon feedstock comprising additives, degradation products, contaminants or any pollutant compounds or compounds requiring to be eliminated, in particular with a view to allowing the use of the hydrocarbon feedstock as well as purified. The method according to the invention makes it possible to provide a solution to all or part of the problems of known methods.

In particular, the method according to the invention allows a significant reduction in the passage of contaminant elements through the filter during the filtration treatment of a used oil, regardless of the filtration mode used.

The process according to the invention also makes it possible to purify waste oils and thus to allow their reuse, in particular as a lubricating base.

In addition, the ease of implementation of the process according to the invention makes it possible to purify quantities of hydrocarbon feedstocks, in particular waste oils, in places that do not allow the implementation of known processes requiring the installation of bulky and expensive equipment, particularly isolated or remote areas; these moderate volumes of hydrocarbon feedstocks to be purified can not therefore be purified because they can not be transported easily. interest The economic and environmental advantages of the process according to the invention therefore constitute an additional advantage.

Moreover, the process according to the invention easily adapts to the size of the deposits of used oil to be purified. It is particularly advantageous in terms of investment in equipment compared to processes using distillation under reduced pressure followed by treatment under high pressure of hydrogen, while being non-polluting compared to known processes using sulfuric acid. concentrated. In addition, it is nondestructive of the base oil molecules and avoids the chemical transformation of the feedstock because the molecules making up the base oil are not thermally or oxidatively converted.

In addition, it complies fully with the objective of protecting the environment since it allows both used oils to be recycled into pure base oils, without generating pollutant residues to be disposed of since they are recovered elsewhere. in the form of road bitumens. Indeed, the process according to the invention leads directly, without resorting to any finishing treatment with acid or hydrogen, to base oils of comparable quality to that obtained by means of conventional refining processes as well as Road asphalt of technical quality superior to bitumen from petroleum as containing most of the synthetic polymers of lubricating oils.

A first aspect of the invention therefore relates to a process for purifying a hydrocarbon feedstock, comprising one or more compounds to be eliminated, which comprises the steps of:

a) extracting light compounds present in the load;

b) filtering the compounds to be removed, in the presence of a fluid in the supercritical state;

(c) treating the feed with a process agent;

d) separating the purified hydrocarbon feedstock. Preferably, the invention relates to a process comprising successively steps (a), (b), (c) and (d).

For the process according to the invention, the hydrocarbon feedstock is generally a feedstock comprising one or more hydrocarbons and optionally one or more compounds comprising carbon atoms, hydrogen atoms and which may also comprise one or more heteroatoms.

According to another aspect of the process according to the invention, the hydrocarbon feedstock is a mineral or mineral oil or a synthetic or synthetic oil derived from petrochemistry.

As mineral or mineral oil, mention may be made of mineral oils derived from the fractional distillation of crude oil which, properly additivated, become industrial oils, gear oils, hydraulic oils or motor oils.

As synthesis oil, mention may be made of polyisobutenes, poly-α-olefins, hydrotreated or hydroisomerized lubricating bases, IOPs or polyolefin olefins.

According to another aspect of the invention, the hydrocarbon feedstock is in liquid form under the conditions of implementation of the process. According to another aspect of the process according to the invention, the compound (s) to be eliminated are:

• additives initially present in the unwashed or used load, including dispersant additives, detergent additives, anti-wear additives, polymers; and may have been degraded in whole or in part;

• elements initially not included in the load, including water, dust, soot, metal elements from eg the wear of the parts with which the load is in contact during use.

The dispersant additives may be organic compounds comprising a polar part and a lipophilic part and may allow the suspension within the hydrocarbon feedstock of solid or colloidal elements such as dust, soot, wear metals, solid residues or colloidal oxidation. These dispersant additives generally make it possible to prevent these solid or colloidal elements from agglomeration and thus prevent the formation of deposits within the filler These dispersant additives constitute the major chemical obstacle preventing the disassembly of the used lubricant.

The dispersing additives may for example be alkenylsuccinimide compounds, in particular of formula (1):

(1)

in which R ¹ represents a hydrocarbon group, or "Mannich base" type compounds, in particular of formula (2):

(2)

in which R ² represents an alkyl group.

According to one aspect of the process according to the invention, the extraction of the light compounds present within the feed has for main purpose the elimination of fuels or water. The elimination of water is particularly advantageous when a ceramic filtration membrane is used. Advantageously, the extraction step is carried out under vacuum or under reduced pressure, preferably under the usual vacuum extraction conditions.

According to another aspect of the process according to the invention, the extraction step is carried out at a pressure customary for those skilled in the art, in particular at a pressure of less than 0.08 bar, for example less than 0.05 bar, or even less than 0.03 bar. According to another aspect of the process according to the invention, the extraction step is carried out at a temperature customary for those skilled in the art, in particular at a temperature ranging from 100 to 250 ° C., for example at about 150 ° C. According to another aspect of the process according to the invention, the filtration concerns the majority of the compounds to be removed, preferably 80% or even 90% or more of the compounds to be removed are filtered.

According to another aspect of the process according to the invention, the filtration of the compounds is carried out by means of a filter which may be a membrane based on metals or metal alloys such as steel, for example stainless steel, or nickel; oxides such as oxides selected from Al ₂ O ₃ , ZrO ₂ , TiO ₂ .

According to another aspect of the process according to the invention, the filter makes it possible to retain compounds or particles whose mean size, ie the mean particle diameter, ranges from 1 nm to 10 μm, in a manner that is preferably 2nm at 1 μιη and more preferably from 2nm to 0.1 μιη.

According to another aspect of the process according to the invention, the filtration is a frontal filtration or a tangential filtration, in particular a monophasic tangential filtration.

According to the present invention, the flow of charge meets or crosses the filter perpendicularly when the filtration is frontal or flows parallel to the filter surface when the filtration is tangential.

Advantageously, the filtration is assisted or carried out in the presence of a fluid in the supercritical state. The fluid in the supercritical state can be selected from CO ₂ , N ₂ O, SF ₆ , alkanes such as methane, ethane, propane or hexane. Preferably, the fluid in the supercritical state is CO ₂ .

The fluid in the supercritical state may be present in an amount ranging from 2 to 60% by weight of hydrocarbon feedstock to be purified, preferably in an amount ranging from 8 to 30%, more preferably ranging from about 12 to 25%, even more preferably in an amount of about 15% to 20%, especially when this fluid is CO ₂ .

According to another aspect of the process according to the invention, the filtration is carried out at a temperature ranging from 50 to 450 ° C., preferably from 60 to 200 ° C., more preferably ranging from 100 to 180 ° C., even more preferably from 100 to 180 ° C. approximately 15 ° C.

According to another aspect of the process according to the invention, the filtration is carried out at a pressure ranging from 50 to 350 bar, preferably from 100 to 250 bar, more preferably from 120 to 180 bar, even more preferred about 150 bars.

During the filtration step, the membrane or filter retains all the particles or compounds having a diameter greater than the average mesh size of said filter and thus make it possible to isolate a filtrate freed from these compounds or particles, or even size molecules. smaller that can be retained by polarization effect of the layer. In general, the action of the fluid in the supercritical state can be implemented before, simultaneously with or after the filtration step.

In the process according to the invention, the fluid in the supercritical state generally makes it possible to reduce the viscosity of the hydrocarbon feedstock to be treated and thus allow or facilitate its filtration. Thus, a lowering of the viscosity by a factor of 4 to 5 is possible.

Generally, the dissolution of the supercritical fluid in the hydrocarbon feed leads to an increase in its volume. This increase can be from a factor ranging from 1.01 to 3, in particular a factor of about 1.15.

The monophasic tangential filtration within the process according to the invention makes it possible in particular to retain the metals or soots that would still be present in the hydrocarbon feedstock, especially in used oil, after an initial extraction step. At the end of this monophasic tangential filtration, the hydrocarbon feedstock may be subjected to a biphasic filtration assisted by a supercritical fluid and to separate a residue, highly viscous or solid, a purified liquid and high viscosity, generally higher or equal to 1000cSt measured at 40ºC, preferably greater than or equal to 1500cSt measured at 40ºC.

In the case of CO ₂ in the supercritical state, it is found that it behaves as a solvent and is generally completely dissolved in the hydrocarbon feedstock as a whole. The process is then in monophasic mode.

At the end of the concentration, the amount of CO ₂ is increased to thin the retentate which has become very viscous. In the case where the CO ₂ is no longer dissolved in only part of the charge, the process is in two-phase mode.

It is thus possible surprisingly to separate a solid or quasi-solid, so-called dry, phase from an exclusively liquid and oily phase during the purification of a used oil. The separated solid phase is for example of the bituminous type which is then concentrated by a factor of 10 to 100, preferably by a factor of 20 to 60. Generally, the majority or all of the compounds to be eliminated or undesirable within the oil to be purified is concentrated in this residue or solid phase. Most often a physically and chemically inert residue is obtained which can be used for road surfacing or as a jointing material for example.

After filtration, the residue and the liquid may be subjected to an expansion to separate the supercritical fluid, in particular CO ₂ , for recycling.

The use of CO ₂ as a supercritical fluid in the process according to the invention makes it possible to greatly improve its safety, in particular by reducing the fire risks associated with conventional processes for refining used oils.

The method according to the invention can be implemented continuously or discontinuously, that is to say batch or batch.

During the final stage of distillation of the hydrocarbon feedstock making it possible to separate the converted compounds in such a way as to render them non-distillable, the yield is generally of the order of 80 to 85% efficiency, evaporation enthalpy of about 300kJ / kg of oil, sensible heat of about 2kJ / kg of oil / K.

According to another aspect of the process according to the invention, the filtration may be preceded by the addition of an aggregating agent. Preferably, such an aggregating agent is of the bitumen type. It is then generally added in an amount ranging from 0.1 to 10% by weight of starting hydrocarbon feedstock, preferably in an amount ranging from 0.5 to 2% by weight of hydrocarbon feedstock, in particular in a quantity 1% by weight of hydrocarbon feedstock starting. According to another aspect of the process according to the invention, the treatment of the filler by means of a transformation agent may be a bleaching, a salification, a saponification, a trapping or a chemical modification of the compounds to be eliminated. Preferably, it is a saponification. According to another aspect of the process according to the invention, the treatment of the filler by means of a transformation agent is carried out by means of a hydroxide derivative of metal or alkaline earth metal used alone or in a mixture, for example NaOH or KOH, which may be used in aqueous solution, for example at about 50% by weight.

According to another aspect of the process according to the invention, the treatment of the feedstock by means of a transformation agent is carried out at atmospheric pressure or at higher pressures. In particular, the treatment of the feedstock with a transformation agent is carried out at a pressure ranging from 1 to 10 bar or alternatively from 2 to 5 bar. Conducting this treatment step at atmospheric pressure is advantageous.

According to another aspect of the process according to the invention, the treatment of the feedstock by means of a transformation agent is carried out at a temperature ranging from 30 to 350 ° C., preferably from 50 to 200 ° C., even more preferably from 50 to 200 ° C. about 95 to 100ºC.

According to another aspect of the process according to the invention, the treatment of the feedstock by means of a transformation agent is carried out with stirring, preferably with vigorous stirring, or even very strong stirring.

Advantageously, during the step of separating the compounds to be removed from the purified hydrocarbon feedstock, the separation is facilitated by the transformation of these compounds by means of or by the action of the transformation agent. This final step is therefore advantageously implemented following the treatment step with a transformation agent.

Also advantageously, the separation step is carried out by distillation of the hydrocarbon feedstock making it possible to separate the transformed compounds between the distillable fractions and the fractions made non-distillable.

According to another aspect of the process according to the invention, the distillation is a vacuum distillation, for example a falling film vacuum distillation or a reduced-pressure distillation in a thin layer. When performing a falling film distillation, the start distillation parameters are advantageously about 19mbar for the pressure, about 240 ° C. for the medium temperature and about 50 ° C. for the temperature at the top. of column. At the end of distillation, these parameters are generally about 19mbar for the pressure, of about 375ºC, tending towards 400ºC, for the temperature of the medium and about 375ºC for the temperature at the head of column.

The particular or preferred features of the method according to the invention can be combined with each other in ways to define variants of the method according to the invention. In particular, the specific combinations of the preferred characteristics define preferred variants of the process according to the invention.

Thus, one of the preferred variants of the invention is a process for purifying a used oil, comprising one or more compounds to be eliminated, which comprises the steps, in particular successive steps:

a) extracting light compounds present in the load;

b) filtering the compounds to be removed tangentially in the presence of a fluid in the supercritical state;

c) treating the oil with a transformation agent, preferably sodium hydroxide in aqueous solution;

d) separating the compounds transformed by distillation of the hydrocarbon feedstock.

An even more preferred variant of the invention is a process for purifying a used oil, comprising the steps, in particular successive steps:

a) extracting, by distillation under vacuum or under reduced pressure, light compounds present in the load;

b) filtering the compounds to be removed tangentially in the presence of about 15% by weight hydrocarbon feed CO ₂ in the supercritical state;

c) treating the oil or the hydrocarbon feedstock with soda in aqueous solution at about 50% by weight;

d) separating the transformed compounds by distillation under reduced pressure of the hydrocarbon feedstock.

Moreover, the method according to the invention can be implemented within an installation comprising at least:

A first unit, for example a tank, in which the hydrocarbon feedstock to be purified is placed;

A filtration unit connected to the first unit; and

• a retentate collection unit and a filtrate collection unit both connected to the filtration unit.

A schematic embodiment of the method according to the invention is illustrated in Figure 1 which shows a schematic sectional view of an example of an installation for implementing the method of the invention. Example:

A more detailed embodiment of the method according to the invention is illustrated in Figure 2 which shows a schematic sectional view of an example of an installation for implementing the method of the invention.

The used oil (HU) is the result of the draining of a new ACE E7 oil grade ACE E7 heavy duty diesel engine turbo diesel engine running 60,000km in a RVI brand truck; this type of used oil was chosen for its severity during the regeneration treatment (strong additivation and presence of a large amount of compounds derived from the degradation of diesel, see Table 1);

The oil (HU) is brought to a temperature of 150ºC in the exchanger (e1) and then introduced into the extractor (2) under a partial vacuum of 20mmHg.

The water (E) extracted at the top is directed towards (s1), the bottom of the column is introduced into the extractor (3). The volatile fractions (FV) which are fuels are extracted at the top of the column and are directed to (s2); HU, free of its volatile fractions (HU-E-FV) is directed to the mixing plant (1).

Beforehand, the additive (A) is heated to 150ºC; it is introduced into HU-E-FV in a mixing plant (1); the additive (A) is a bitumen aggregation agent introduced at about 1% by weight. The mixture (HU-E-FV + A) is brought to a temperature of 150ºC in the exchanger (e2).

The fluid (C) stored in (s3) is CO2; it is heated to 150ºC and 150 bar which corresponds to a supercritical state; it is introduced at the rate of 20% by weight in (f1) at the same time as the used oil (HU-E-FV + A).

The used oil (HU-E-FV + A) is introduced into a first tangential filtration loop (f1); the transmembrane pressure of 4 bar allows the passage of the oil through the membrane.

The retentate (R1) is introduced into a second loop (f2).

The filtrate (F + C) is directed to the separator (d), (C) is recycled to (s3), the separated filtrate (F) is directed to the exchanger (e3).

The retentate (R2) is introduced into a third loop (f3).

The filtrate (F + C) is directed to the separator (c2), (C) is recycled to (s3), (F) is directed to the exchanger (e3).

The retentate (R3) is directed to the bitumen pool (PB).

The filtrate (F + C) is directed to the separator (c3), (C) is recycled to (s3), (F) is directed to the exchanger (e3).

(F) is brought to a temperature of about 100ºC, and is introduced into the saponification plant (4). Solution (S) is composed of 5% by weight of water and 5% by weight of sodium hydroxide of purity equal to 98.5%; (S) is introduced at 10% by weight in the saponification plant (4) with (F) where it is maintained at a reflux temperature of 95 to 100ºC for several hours (4 to 7 hours) under very strong agitation.

The mixture (F + S) after reaction is directed to the exchanger (e4) where it is heated to 250ºC

The mixture (F + S) is introduced into the distillation plant (5); at the start of the distillation, the pressure is 19 mm Hg with a bottom temperature of 240ºC and a temperature at the top of column of 50ºC; the final temperature at the top is 375ºC at 19mm Hg, the bottom temperature does not exceed 400ºC. At the top of the colon, the water is recovered from the sodium hydroxide solution (S) and then the base oil (HB) with a yield of 84%. The enthalpy of vaporization was calculated at 300 kJ / kg of oil and the sensible heat Cp is 2 kJ / kg / K.

The distillation residue (R4) is sent to the bitumen pool (PB) (see Table 1 for the metal content).

Base oil (HB) extracted at the top is directed to storage; the reduction of pollutants is total (see Table 1); traces of silicon are attributable to the use of the silicone paste used to seal the glassware; the phosphorus which was the most difficult marker to reduce has disappeared. The sodium introduced by the soda in excess does not bring pollution.

The metal contents were analyzed by atomic adsorption spectrometry (ASTM D5185); the viscosities were measured by standard NF EN ISO 3104; nitrogen contents were measured by chemiluminescence (ASTM D 4629).

Table 1: reduction of pollutant markers at each step After the oil treatment, a test according to EN12591 (European Union standard defining the different types of bitumen) was carried out on the retentate from ultrafiltration. Three analytical methods from this standard have been implemented; their characteristics and the results obtained are shown in Table 2.

Table 2

The result of the aging resistance test shows the residual presence of antioxidants that have not been completely neutralized. Additional oxidation would neutralize these antioxidant compounds. The bitumen can nevertheless be used before or after such additional treatment.

Spectrometric analysis by atomic adsorption spectrometry (ASTM D5185) gave the results shown in Table 3.

The characterization tests carried out on the vacuum distillation residue gave the results shown in Table 4.

Table 4 These results show the possibility of obtaining at the end of the implementation of the process according to the invention, besides a quality oil for its use, also a bitumen that can be used according to the standards and practices in force.

Claims

1. A process for purifying a hydrocarbon feedstock, comprising one or more compounds to be removed, which comprises the steps of:

a) extracting light compounds present in the load;

(c) treating the feed with a process agent;

d) separating the purified hydrocarbon feedstock.

2. Method according to claim 1 comprising successively steps (a), (b), (c) and (d).

3. Method according to claims 1 or 2 wherein the hydrocarbon feedstock comprises one or more hydrocarbons and optionally one or more compounds comprising carbon atoms, hydrogen and which may also include one or more heteroatoms.

4. Process according to Claims 1 to 3, the hydrocarbon feedstock of which is chosen from mineral or mineral oil or synthetic or synthetic oil.

5. Process according to claims 1 to 4, the hydrocarbon feedstock of which is chosen from mineral oils resulting from the fractional distillation of crude oil.

6. Process according to claims 1 to 5, the hydrocarbon feedstock is selected from industrial oils, gear oils, hydraulic oils or motor oils, used or used.

7. Process according to Claims 1 to 6, in which the compound (s) to be removed are chosen from dispersant additives, detergent additives, anti-wear additives, polymers, soot, metallic elements.

8. Process according to claims 1 to 7, the extraction or separation is carried out by distillation under vacuum or under reduced pressure.

9. Process according to claims 1 to 8, the filtration is preceded by the addition of an aggregating agent.

10. Process according to claims 1 to 9, the filtration of which is preceded by the addition of a bitumen-type aggregation agent added in an amount ranging from 0.1 to 10% by weight of starting hydrocarbon feedstock.

1 1. Process according to Claims 1 to 10, the filtration of which is preceded by the addition of a bitumen-type aggregation agent added in an amount ranging from 0.5 to 2% by weight of starting hydrocarbon feedstock.

12. Process according to claims 1 to 1 1, the fluid in the supercritical state is present in an amount ranging from about 2 to 60% by weight of hydrocarbon feedstock to be purified.

13. Process according to claims 1 to 12, the fluid in the supercritical state is CO ₂ .

14. Process according to claims 1 to 13, the fluid in the supercritical state is CO ₂ present in an amount of about 15 to 20% by weight of hydrocarbon feedstock.

15. Process according to claims 1 to 14, the filtration of which is a tangential filtration.

16. The method of claims 1 to 15 whose filtration is carried out at a temperature ranging from 100 to 180ºC or at a pressure ranging from 120 to 180 b ars.

17. Process according to claims 1 to 16, the treatment of the charge by means of a transformation agent is carried out by saponification.

18. The method of claims 1 to 17 wherein the transformation agent is selected from NaOH or KOH, used alone or in admixture.

19. The method of claims 1 to 18 comprising the steps, in particular successive:

a) extracting by distillation, under vacuum or under reduced pressure, light compounds present in the batch;

b) filtering the compounds to be removed tangentially in the presence of CO ₂ in the supercritical state;

d) separating the transformed compounds by distillation under reduced pressure of the purified hydrocarbon feedstock.