WO2013098510A1

WO2013098510A1 - Method for extracting metals present in hydrocarbon fractions

Info

Publication number: WO2013098510A1
Application number: PCT/FR2012/053016
Authority: WO
Inventors: Joëlle NOKERMAN; Vincent RIETSCH; Romain RUPPERT
Original assignee: Total Raffinage Marketing
Priority date: 2011-12-27
Filing date: 2012-12-20
Publication date: 2013-07-04
Also published as: FR2984913A1

Abstract

The invention relates to a method for extracting metals from a hydrocarbon fraction containing coordinated metals, comprising the following steps: demetallation of the coordinated metals by (i) bringing said hydrocarbon fraction into reaction, in an inert atmosphere, with an aprotic polar solvent and an acid buffer solution, having a pH of between 0.8 and 2.5, the reaction medium thus obtained further comprising a reducing metal having a standard potential, E₀, of between -0.7 and -0.9 V, present in an amount of at least 6 equivalents per 1 equivalent of coordinated metal, (ii) reflux heating the reaction medium to a temperature matching the boiling temperature of said aprotic polar solvent, until discolouration of the reaction medium, and extraction of the metal salts by adding a lipophilic solvent and the acid buffer solution, said metals being recovered in the acid buffer phase.

Description

Process for extracting metals present in hydrocarbon fractions

The invention relates to a process for extracting metals present in hydrocarbon fractions containing coordinated metals. Heavy oils usually have a significant share of different petrophorphyrins or coordinated metals, from a few particles per million to a few hundred ppm. These, difficult to separate from crude oil, are metallated, mainly by vanadium (IV) and nickel (II). Of the petroporphyrins, vanadium porphyrins are typical of marine sediments, while those of nickel are mainly present in a continental environment. The high thermodynamic stability of these compounds explains their predominance in sediments vis-à-vis other metalloporphyrins.

The nickel and vanadium contained in the petroleum residues are mainly concentrated in the asphaltene fraction of the latter. In the particular case of Athabasca bitumens, metals were also found in significant quantities in the Maltene fraction. The metal compounds present in the residues are in the form of soluble organometallic complexes such as porphyrins. Nickel and Vanadium may also be present in non-porphyrinic structures, which are currently poorly defined. In the particular case of vanadium, it seems that porphyrins are largely in the majority compared to other metallic structures.

On the other hand, it appears that the vanadium present in heavy oils is essentially in the form of vanadylporphyrins. The most common forms of vanadylporphyrins have been identified as the ETIO (etioporphyrin) form, which derives directly from Theme, and the DPEP (deoxophylloerythroetioporphyrin) form which derives from different types of chlorophylls. The presence of vanadium in heavy oil comes from the slow degradation of these systems.

The removal of these metals as early as possible in crude treatments is a necessity as these metals reduce the service life of the catalysts that are used in downstream refining operations, such as catalytic cracking, hydrocracking and hydrodesulfurization (EP 1939270 A1). Indeed, some metals such as vanadium poison the catalyst by depositing on its surface, tending to reduce the activity, which requires the premature replacement thereof. Other metals, such as nickel, generate side reactions such as dehydrogenation. In the refining industry, if necessary, the metals present in petroleum hydrocarbons are removed by hydrotreating, and more particularly by hydrodemetallization, or by coking. These processes, however, lead to a significant loss of raw material and lead to the formation of vanadium pentoxide V ₂ O ₅ , which poses problems of toxicity (L. Zychlinski et al., Arch., Environ Tox 1991, 20, 295 -298) and corrosion (LF Drbal et al, Power Plant Engineering by Black & Veatch, Springer, New York, 1996).

The catalysts are based on noble metals, and therefore expensive, it is advisable to preserve and save them by demetalling the porphyrins contained in the crude oil. However, these metalloporphyrins are often contained in asphaltenes, a portion of these oils soluble in toluene and insoluble in alkanes. In heavy oils, there are colloidal aggregates, which can be very stable, and thus prevent easy extraction of these metalloporphyrins.

However, several patents have been published to provide methods for extracting metalloporphyrins using polar solvents such as 2-pyrrolidone (US 3,052,627) or 2-butyrolactone (US 2,913,394). US Pat. No. 4,643,821 describes the best specific solvents for extracting vanadylporphynes in asphaltenes. It is by employing a mixture of aromatic and polar solvents that the best results have been obtained insofar as this mixture makes it possible both to solubilize the heavy oils and to extract the metalloporphyrins.

One of the objectives of the inventors is to achieve this demetallation reaction with high yields and using the mildest possible conditions to preserve the crude oil. For this purpose, numerous methods of demetallation of various metalloporphyrins have been described in the literature or patents such as, for example, oxidation demetallation (US Pat. (US 5,726,056, PM Fedorak et al., Enzyme Microb.Techn., 1993, 15, 429-437), electrolytic demetallation (US 5,529,684, C. Ovalles et al, Fuel Processing Technology, 1996, 48, 241-247). or photolysis (H. Kunkely et al, Inorganic Chemistry Communications, 2007, 10, 479-481). However, two main methods emerge: an electrochemical route and a chemical route. Both approaches have been considered and are described in the literature, in particular by MF Ali et al, Fuel Processing Technology, 2006, 32, 573-584.

Mr. F. Ali et al lists a large quantity of proposed chemical reagents for the demetallation of petroporphyrins. Several of the studies described have been carried out by manufacturers (Exxon, Shell, China Petrochemical Corp., etc.). While some of the proposed reagents appear to be relatively non-destructive of organic matter, others, such as hydrofluoric acid, sulfuric acid, nitric acid and sodium hypochlorite, are not very selective towards demetallation of porphyrins. In addition to the demetallation reactions, deterioration of unmetallated molecules is observed by different side reactions, such as oxidation, polymerization of unsaturated compounds and incorporation of chlorine. This explains the reason why the development of these demetallation processes was not a priori led to the stage of industrialization.

The patent application cited above, EP 1 939 270 A1, discloses a process for the selective metalloporphyrin oxidation demetallation of a real charge and removal of the metal in a single step. The oxidant used is a hydroperoxide and the oxidation is catalyzed by Fe (III). However, the use of such conditions is not without consequences, since they lead to the deterioration of heavy oil by oxidation and the formation of free radicals. Despite high demetallation rates on real load, this method is therefore not entirely satisfactory economically.

The Applicant has focused his research on chemical demetallation using acidic and / or reducing conditions. This method is generally represented in the literature by a general equation PM (II) + 2 HX ^ PH ₂ + MX ₂

The use of acidic conditions is valid for many metal ions, for example zinc-octaethylporphyrin (Zn (II) OEP), which requires dilute hydrochloric acid (HCl) or Ni (II) OEP for which sulfuric acid (H ₂ SO ₄ ) is essential for the demetallation reaction. However, the use of a strong acid, even destructive vis-à-vis oils, is not recommended in engineering because of corrosion problems.

In the case of vanadylporphyrins (O = V (IV)), both reductive and acidic conditions are required (J. W. Buchler, The Porphyrins, Ed D. Dolphin, 1978). Vanadium being paramagnetic, in order to determine the structure of vanadylporphyrins by NMR, geochemists have developed a demetallation reaction under very stringent conditions, such as treatment with methanesulfonic acid at 110 ° C. for 1 h 30 (US 3190829). Then, the bases thus obtained, are metallized with nickel (II) to obtain nickelporphyrins analysable by NMR because diamagnetic. However, this method causes the degradation of 60 to 70% porphyrins.

The SU 1403082 A1 patent describes conditions that are much milder at temperatures and pressures, and more selective, with the use of zinc as a reducing agent and acetic acid as a source of protons. This document describes the possibility of demetalling Vanadium metalloporphyrins by reduction in the presence of H ⁺ ions. Zinc powder is used as a reducing agent and glacial acetic acid is used as a protic solvent (ie proton donor). The demetallation tests were carried out at a pressure close to atmospheric pressure and at a relatively low temperature, namely the boiling point of acetic acid (ie 1 18.1 ° C. to 1013 mbar). The Russian patent discloses the recovery of demetallated porphyrins, using diethyl ether, with a yield of between 60 and 85% by weight as a function of the proportion acetic acid / zinc powder. One of the aims described in this document is the search for a shortest reaction time possible (20 to 30 min) while avoiding the implementation of an inert atmosphere. This method therefore uses a reagent and inexpensive and non-toxic solvents.

On the basis of this document, the Applicant has attempted to implement a demetallation of porphyrins based on Ni and V, and more generally on a hydrocarbon fraction comprising such porphyrins or of coordinated metals. However, the strict implementation of this process, as described in this document, did not provide the expected results in terms of yields and reaction times.

The publication of J. G. Reynolds (Prepr Pap-Am Chem Soc, Div.

Fuel. Chem., 2004, 49 (1), 79-80) relates to the extraction of nickel and vanadium from petroform crude petroleum crude oils. The implementation there described does not use reducing metals or inert atmosphere, the reaction medium being weakly acidic.

In order to overcome the drawbacks of the prior art, the Applicant has set itself the objective of implementing a process for the demetallation of porphyrins and derivatives, simple, under non-corrosive conditions, at relatively low temperatures, from order of a hundred degrees, and at pressures close to atmospheric ones.

Accordingly, the invention relates to a process for extracting metals from a hydrocarbon fraction containing coordinated metals, comprising the following steps of:

1) demetallation of the metals coordinated by (i) reacting, under an inert atmosphere, said hydrocarbon fraction with an aprotic polar solvent and an acidic buffer solution, with a pH of between 0.8 and 2.5, the medium reaction mixture thus obtained further comprising a reducing metal having a standard potential, E ₀ , between -0.7 and -0.9 V, present in an amount of at least 6 equivalents for 1 equivalent of coordinated metal, (ii) refluxing the reaction medium at a temperature corresponding to the boiling point of said aprotic polar solvent, until the reaction medium is decoloured, and

2) extraction of the metal salts by addition of a lipophilic solvent and the acidic buffer solution, said metals being recovered in the acidic buffer phase. The applicant has thus shown that the implementation of the process allows a recovery of the coordinated metals from this hydrocarbon fraction, which metals advantageously represent nickel and vanadium, with a level of between 2% and 30% for vanadium. preferably between 10% and 22%, and between 2% and 8% nickel. In addition, the extraction of metals has the advantages of avoiding, on the one hand, the poisoning of the catalysts used in the treatment of these hydrocarbon fractions and, on the other hand, the degradation of this fraction.

The implementation and the optimization of the process to achieve such levels have been carried out by the Applicant by considering model porphyrins containing vanadium and nickel.

Examples of such porphyrins that have been considered are vanadyloctaethylporphyrin (O = VOEP), vanadyletioporphyrin (O = VETIO) existing under four isomers (O = VETIO I, O = VETIO II, O = VETIO III, O = VETIO IV), Nickeloctaethylporphyrin (NiOEP), Nickeletimorphyrin (NiETIO) existing under four isomers (NiETIO I, NiETIO II, NiETIO III , NiETIO IV), because representative of petroporphyrins and others, in petroleum fractions.

This method, when used on these model porphyrins, makes it possible to obtain metal extraction rates (V and Ni) of between 10% and 96%, the levels of the lower limit being usually obtained for Nickel.

Indeed, the Applicant has therefore shown that, without being bound by any theory, nickel porphyrins have the lowest recovery rates, which can be explained by the fact that they are less reducible in the medium. due to their standard potential, E ₀ , of about -1.2 V, whereas that of vanadium porphyrins has a value of about -1.0 V.

Moreover, it has been observed that the metal recovery rates and the material balance of the metals, defined as being the quantities present in the aqueous phase and in the organic phase by the lipophilic solvent, are better, for example respectively from a factor 2 to 4 for recovery rates, and about 10% to 25% for material balances, for O = VOEP and NiOEP, compared to O = VETIO and NiETIO.

The method of the invention has the advantage of being implemented in a simple way, in particular on an industrial scale, by using mild conditions, in particular at pressures close to those of atmospheric pressure, and operating conditions allowing the non-degradation of the hydrocarbon fraction of starting and conventional devices implementation.

The hydrocarbon fraction to be treated contains coordinated metals in particular in the form of metal-based petrophorphyrines essentially representing vanadium and nickel, which does not exclude other complex structures also coordinated by these metals. Such fractions are advantageously crude and have very variable levels of these metals depending on the origin thereof. By way of example, the average metal contents extracted from the 375 ° C + section (equivalent to an atmospheric residue) are between 1, 2 and 135 ppm Ni and between 1 and 2300 ppm vanadium, in the 375 ° section. C-550 ° C (equivalent to a distillate vacuum), the average contents of these metals are between 0 and 0.3 ppm and between 0 and 0.8 ppm, and in the 550 ° C + section (equivalent to a vacuum residue), the respective average contents are at 175 ppm and from 4 to 3000 ppm.

The first step of the process (step 1) concerns a demetallation reaction of the coordinated metals present in the forms indicated above of the hydrocarbon fraction.

This reaction is carried out by bringing the hydrocarbon fraction into contact with an aprotic polar solvent (step 1) (i)), which is very advantageously chosen so as to be able to solubilize the porphyrins and the petroporphyrins and to be miscible with water. and especially in the acid buffer solution. Preferably, this solvent is selected from the group consisting of dioxane, tetrahydrofuran, acetone, acetonitrile, dimethylformamide, dimethylsulfoxide, furfural, and mixtures thereof, preferably dioxane.

The demetallation reaction also involves the addition of an acid buffer solution (step 1) (i)), preferably of the phosphate buffer, sulfate or nitrate buffer, the concentration of which varies advantageously between 0.10 M and 2 M, in between 0.15 M and 2 M.

The pH of implementation of the demetallation reaction must be between 0.8 and 2.5, preferably between 1.4 and 1.8. If necessary, the pH can be adjusted by adding an acidic or basic compound to obtain these values.

The aprotic polar solvent can be added first, then the acid buffer is added, or vice versa. It is also possible to add an aprotic polar solvent / acid buffer mixture.

The Applicant has shown that the volume ratio between the aprotic polar solvent and the acid buffer can have as much influence on the kinetics of demetallation as on the recovery rate of the metals of interest.

Advantageously, the volume ratio aprotic polar solvent / acid buffer is between 1, 5 and 16, more preferably between 4 and 8, in particular between 3 and 5.

In addition, this ratio which has been advantageously defined is also based advantageously on the amounts of reducing metal and the amount of hydrocarbon fraction to be treated. Therefore, it is advantageous to use 1 liter of aprotic polar solvent / acid buffer mixture, preferably in a volume ratio of between 3 and 5, of from 1 to 40 g, preferably from 9 to 40 g, of reducing metal. and between 0.7 and 1.3 kg of hydrocarbon fraction, preferably between 0.9 and 1.1 kg.

The reaction medium is obtained by mixing the hydrocarbon fraction, aprotic polar solvent, acid buffer solution and reducing metal, the latter having a standard potential, E ₀ , between -0.7 and -0.9 V .

In order for the reaction to be quantitative with regard to the standard potentials of vanadylporphyrins (E ₀ of approximately -1 V) and nickelporphyrins (E ₀ of approximately -1.2 V), the choice of reducing metal is governed by its E ₀ . Such reducing metals are advantageously chromium (E ₀ = - 0.74 V (Cr ³ 7 Cr)) and zinc (E ₀ = -0.76 V (Zn ² 7 Zn)), zinc being the preferred.

The amounts of reducing metal present in the reaction medium is at least 6 equivalents for 1 equivalent of coordinated metal. Indeed, considering the model porphyrins, O = VOEP, O = VETIO, NiOEP and NiETIO, the stoichiometry of the reaction involves 3 moles of metal to reduce 1 mole of porphyrin, with exchange of 6 electrons. For example, 100-400 mg of reducing metal, preferably 200-400 mg for about 2-5.5 mg of metals (sum of Ni and V), may be considered on a laboratory scale, in a ratio by weight of the amount of reducing metal on the amount of metals between 20 and 100. These quantities can be extrapolated for implementation on a pilot or industrial scale, provided that the respective proportions are respected. The reducing metal is usually in the form of powder or filings.

The amount of reducing metal present in the reaction medium and necessary for the demetallation reaction can be added all at once, or very advantageously several times during the reaction. Indeed, an addition several times, preferably at least twice, or even three times, of the amount required over the duration of the reaction substantially improves the kinetics of the reaction, which reduces the duration of the reaction of about 50%. The demetallation reaction (step 1) involves maintaining the reaction medium under an inert atmosphere, such as under argon or nitrogen or other rare gas.

The reaction under an inert atmosphere promotes the kinetics of demetallation and improves the extraction efficiencies of the metals.

The reaction medium obtained by mixing the hydrocarbon fraction, aprotic polar solvent, acidic buffer solution and reducing metal is refluxed (stage 1) (ii) at the boiling point of the aprotic polar solvent mixture. acid buffer, until discoloration of the reaction medium.

The purpose of the demetallation reaction is to extract metal ions from petroporphyrins or the like.

Without being bound by any theory and on the basis of model porphyrin demetallation reactions described above, the first step of this reaction would correspond to the dielectronic reduction of the coordinated metals, for example from O = VOEP to a reaction intermediate, vanadyloctaethylchlorin. (O = VOEC), leading to color changes of the compounds obtained, from the initial blue-violet color to the green color in the case of O = VOEP. In a second step, a further reduction by four electrons is observed, resulting in a porphyrinogenic compound (s). The porphyrinogenic compound is subsequently degraded, this degradation being accompanied by the release of metal ions in the reaction medium which is noted by a loss of color, the reaction medium thus becoming colorless. In the presence of the acidic buffer solution, these metal ions stabilize in the form of salts, such as phosphate salts. According to this second step, the loss of color is explained by a loss of aromaticity of the porphyrin-type macrocycle.

The duration of the demetallation step is usually between 1 and 7 hours, advantageously between 1, 5 and 6 hours. The reaction medium is preferably brought to room temperature after the completion of step 1). It is thus essential to carry out the process under an inert atmosphere because the presence of oxygen in all likelihood leads to one or more reoxidation of the various intermediate compounds. We can observe a gain in metal recovery rate by a factor of two, especially for vanadium.

The second step of the process (step 2)) consists of an extraction of the metal salts by adding a lipophilic solvent and the acidic buffer solution, said metals being recovered in the acidic buffer phase.

Once step 1) has been completed, the lipophilic solvent is added to the reaction medium, very advantageously chosen from the group consisting of chlorinated solvents, for example chloroform, trichlorethylene, tetrachlorethylene and / or methylene chloride, and benzene derivatives. , such as toluene, xylene and / or ethylbenzene, a reformate cut and their mixture. The benzene derivatives and in particular toluene are advantageously used because they make it possible to obtain a maximum recovery rate.

Subsequently, the acidic buffer solution is added, the added volumes of lipophilic solvent and acidic buffer being preferably in the ratio of 1 to 3, and in any case adapted to the volume of the reaction medium and, according to embodiments the ratio between the sum of the solvent / acid buffer volumes and the volume of the reaction medium is preferably between 0.4 and 1. The addition of acid buffer can be done at the same time as the addition of solvent.

This step of adding lipophilic solvent and acid buffer is implemented as a liquid-liquid extraction step in order firstly to wash the organic phase obtained with the lipophilic solvent, and secondly to extract the metal salts and thus concentrate the acidic buffer phase rich in these metal salts. According to this implementation, the yield is maximum. The organic phase is preferably washed at least two more times with water which is recovered and combined with the acidic buffer phase. The organic phase is enriched in coordinated metals that have not been demetallated.

The method may also advantageously comprise a filtration step of the reaction medium at the end of the demetallation step (step 1)).

This filtration step is carried out in order to eliminate particles of powder or filings of unreacted reducing metal. However, the filtration may cause a deposit on the filter of insoluble metal salts in the reaction medium. This recovery can, according to modes of For example, the metal salts with the species present in the acidic buffer may have different solubilities. Thus, depending on the case, a cleaning of the filter for the recovery of insoluble salts can be carried out, typically by washing with a strong acid, such as the nitric acid of usual concentration for a mineralization, then by microwave treatment, in particular during 0.5-2h at a temperature between 150 ° C and 170 ° C. The recovery rate and the material balances indicated above take this aspect into account.

The process may comprise an additional step, carried out after step 2), of treating the acidic buffer phase enriched in metal salts with a strong acid, such as nitric acid, while hot (T ° = 70 °). C-90 ° C), the mineralized material, obtained after evaporation of the whole, preferably under reduced pressure, is then recovered and for example analyzed by ICP-AES to determine the content of the metals.

According to embodiments of the invention, the method further comprises after step 1), after an optional filtration step, a step of removing the aprotic polar solvent / buffer mixture, in particular by evaporation under reduced pressure.

The mineralizate obtained after evaporation of the mixture undergoes the treatment of step 2) described above. Although the yields are satisfactory, this implementation is however less preferred than the previous one. The percentage of metal demetallation or recovery is defined as the ratio between the content of metals in the aqueous phase and optionally that in the filter and the sum of the metal contents in the aqueous phase, in the organic phase and optionally in the the filter.

The process may comprise a separation step, in particular by electrolysis, and recycling of the reducing metal which has been oxidized, present in the acidic buffer phase, to step 1), and also at least one step of separating and recycling the solvents used, implemented after step 2). Treatment of the acidic buffer phase containing the metal salts is possible in order to separate and recycle, for example, zinc oxidized to Zn ²⁺ during the reduction of the coordinated metals at the end of step 2). This step can be carried out in particular by electrolysis. To do this, a prior elimination of most of the solubilized salts in it must be implemented. One possibility is to promote the precipitation of salts by varying the pH of the aqueous phase. The precipitated salts can then be recovered by filtration, which makes it possible to limit their presence in the aqueous effluents. The zinc metal can then be introduced in step 1) of the process.

Furthermore, after step 2), the process may include at least one step of separating and recycling the solvents used during the demetallation (step 1), that is to say, separating the residual hydrocarbon fraction. aprotic polar solvent, and / or extraction (step 2)), that is to say the lipophilic polar solvent relative to the apolar protic solvent, especially after their recovery during the various operations.

For example, on a petroleum production unit, the following quantities of reagents can be envisaged, on the basis of a crude oil comprising 100 ppm of Ni and V per ton.

Gross: 250 T / h 675 T / h

Zinc: 2.3 T / h 6.1 T / h

Dioxane: 200000 L / h 540000 L / h

Acidic buffer: 150000 L / h ~ 150 T / h 405000 L / h

Toluene: 150000 L / h 405000 L / h The invention is now described in more detail with reference to the nonlimiting examples which follow and to the drawings in which:

- Figure 1 shows the structures of the various model porphyrins vanadyloctaethylporphyrin (O = VOEP), vanadyletioporphyrin (O = VETIO) existing under four isomers (O = VETIO I, O = VETIO II, O = VETIO III, O = VETIO IV) , nickeloctaethylporphyrin (NiOEP), nickeletioporphyrin (NiETIO) existing in four isomers (NiETIO I, NiETIO II, NiETIO III, NiETIO IV),

- Figure 2 shows a diagram of the demetallation reaction of O = VOEP. Example 1

General procedure for the demetallation reaction of O = VOEP in the presence of dioxane and sodium phosphate buffer

At room temperature, vanadyloctaethylporphyrin (50 mg, 0.08 mmol, 1 eq) and zinc (200 mg, 3.06 mmol, 38 eq) are added to a solution of 80 mL of dioxane (filtered over alumina: Merck 1 .01097 ) and 20 mL of sodium phosphate buffer solution (pH = 1.5, 0.15 M) previously degassed for 10 minutes with argon. The reaction medium is then refluxed for 90 minutes still under argon. After returning to ambient temperature, the resulting solution is filtered on filter paper. After addition of 30 ml of dichloromethane and an additional 20 ml of sodium phosphate buffer solution (pH = 1.5 and 0.15 M), the two liquid phases obtained are separated using a light bulb. to decant. The organic phase is then washed with water (2 × 15 mL) and then concentrated under reduced pressure (25 ° C., 15 mmHg). The combined aqueous phases (acid buffer and water) are evaporated on a sand bath at 110 ° C overnight. The residue from the organic phase is taken up in 10 mL of nitric acid concentration allowing mineralization, then this solution is placed for 1 hour in microwaves (800 W, 50 bar, 150-170 ° C). Similarly, the filter is placed in 10 ml of nitric acid and then treated with microwaves (800 W, 50 bar, 150-170 ° C). The acidic buffer phase (and water) is taken up in 10 ml of nitric acid for 1 hour in a sand bath at 80 ° C. The mineralizates are then assayed at the ICP-AES, which allows to isolate the vanadium:

Organic phase: 136 g, recovery rate = 4%,

Filter: 1469 g, recovery rate = 41%, and

Aqueous phase: 1988 g, recovery rate = 55%.

Initial vanadium content in the sample: 4.25 mg

Vanadium recovered: 3.59 mg

The material balance so 85% Example 2: pH influence

The protocol of Example 1 was repeated by varying the pH of the phosphate acid buffer solution. Insoluble metal salts, based on phosphates, on the filter were not taken into account for the balance sheets and recovery rates.

Table 1 presents the results obtained. Table 1

The results indicate that in the pH range according to the invention an aqueous phase enriched with vanadium salts is obtained. Outside this range (pH = 3.5), the recovery rate is not satisfactory.

The material balance is explained by the fact that insoluble phosphate-based metal salts have not been taken into account.

Example 3: Influence of the zinc content

The protocol of Example 1 was repeated by varying the total amount of zinc introduced, all things being equal. Insoluble salts on the filter were not taken into account. Table 2 presents the results obtained.

Table 2

These results indicate that at least a quantity of 100 mg of zinc is required to treat 4.25 mg vanadium O = VOEP (ZnA / porphyrin ratio = 23.5).

Example 4: Influence of the volume of the acidic phosphate buffer

The protocol of Example 1 was repeated by varying the volume of the 0.15 M phosphate buffer, all things being equal (pH = 1.5, the volume of CH ₂ Cl ₂ being 80 mL).

Table 3 presents the results obtained.

Table 3

The results of this Table 3 show that at a given concentration in acidic buffer solution, a minimum volume is required, advantageously in the ratio indicated above.

Example 5: Influence of Acid Buffer Concentration

The protocol of Example 1 was repeated by varying the concentration of the phosphate buffer at a constant volume of 20 ml (pH = 1.5, the volume of CH 2 Cl 2 being 80 ml).

The results are reported in Table 4

Table 4

The results shown in Table 4 show that the recovery rate of V and the satisfactory material balance are obtained in a wide range in acid buffer concentration.

Example 6

Example 1 was repeated considering 50 mg of NiOEP having a nickel content of 4.96 mg.

The following results are obtained:

Nickel recovery rate (aqueous phase + filter): 36%

Organic phase: 64%

Material balance: 81%

Example 7

The protocol of Example 1 was repeated considering O = VETIO, vanadium content of 4.69 mg for 50 mg of sample, and NiVETIO, nickel content of 5.48 mg for 50 mg of sample . Table 5 groups the results obtained. Table 5

Whereas O = OEP and O = VETIO, and NiOEP and NiETIO have a very important structural analogy (ethyl group instead of a methyl group) and therefore a similar reduction potential (30 mV difference for free bases). ), the demetallation rate for the same metal appears completely different. This can be explained by the concentration of the different species present. The O = VETIO, and also the NiETIO by analogy is actually a mixture of four isomers (Figure 1), and the concentration of the different species is necessarily lower than that of the O = VOEP. Referring to a general equation of simplified kinetics, it can be considered that if the concentration of the species is lower, the kinetics of the reaction decreases.

Example 8

The protocol of Example 1 is carried out with a crude oil sample (10 g) containing 3.60 mg of vanadium and 0.8 mg of nickel (sample A). In this example, we vary:

the duration of the demetallation reaction, the amount of zinc added, and

the lipophilic extraction solvent

Table 6 presents the results obtained Table 6

The results indicate that the best metal recovery rate is obtained after 6 hours of reaction considering 400 mg of zinc.

Moreover, the change of extraction solvent, all other conditions being equal, is in favor of the choice of benzene derivatives, showing the best rates.

Claims

1. A method of extracting metals from a hydrocarbon fraction containing coordinated metals, comprising the steps of:

2) extraction of the metal salts by addition of a lipophilic solvent and the acidic buffer solution, said metals being recovered in the acidic buffer phase.

2. The process according to claim 1, wherein the solvent is selected from the group consisting of dioxane, tetrahydrofuran, acetone, acetonitrile, dimethylformamide, dimethylsulfoxide, furfural, and mixtures thereof, preferably dioxane. .

3. Method according to claim 1 or 2, wherein the acidic buffer solution is a phosphate, sulfate or nitrate buffer, the concentration of which varies advantageously between 0.10 M and 2 M, in particular between 0.15 M and 2 M.

4. Method according to one of claims 1 to 3, wherein the pH is between 1, 4 and 1, 8. 5. Method according to one of claims 1 to 4, wherein the volume ratio aprotic polar solvent / acid buffer is between 1,

5 and 16, more preferably between 4 and 8, in particular between 3 and 5.

6. Method according to one of claims 1 to 5, wherein for 1 liter of aprotic polar solvent mixture / acid buffer, preferably in a volume ratio of between 3 and 5, is used from 1 to 40 g of metal. reducing agent, and between 0.7 and 1.3 kg of hydrocarbon fraction, preferably between 0.9 and 1.1 kg.

7. Method according to one of claims 1 to 6, wherein it is implemented for 100-400 mg of reducing metal, preferably 200-400 mg, 2-5.5 mg of metals (sum of Ni and V ), in a ratio by weight of the amount of reducing metal to the amount of metals between 20 and 100.

8. Method according to one of claims 1 to 7, wherein the reducing metal present in the reaction medium is added in one go or in several times during the reaction.

9. Method according to one of claims 1 to 8, wherein the lipophilic solvent is selected from the group consisting of chlorinated solvents, for example chloroform, trichlorethylene, tetrachlorethylene and / or methylene chloride, benzene derivatives , such as toluene, xylene and / or ethylbenzene, a reformate cut and their mixture.

The method according to one of claims 1 to 9, wherein the added volumes of lipophilic solvent and acidic buffer are in the ratio of 1 to 3, and the ratio of the sum of the solvent / acid buffer volumes and the volume of the medium. the reaction being between 0.4 and 1.

1 1. Method according to one of claims 1 to 10, further comprising, after step 1), and after an optional filtration step, a step of removing the aprotic polar solvent / buffer mixture.

12. Method according to one of claims 1 to 1 1, further comprising a step of separating and recycling the reducing metal, which has been oxidized, present in the acidic buffer phase, to step 1), implemented after step 2).

13. Method according to one of claims 1 to 12, further comprising at least one step of separating and recycling the solvents used during the demetallation (step 1) and / or extraction (step 2)), put implemented after step 2).