RU2804748C2 - Method for selective extraction of transition metals from organic residues - Google Patents

Abstract

FIELD: chemical technology.

SUBSTANCE: process for selective recovery of transition metals from an organic stream, which can be obtained in oil refining processes and/or in processes for the hydrogenation conversion of heavy hydrocarbons. The extracting agent consists of an ionic liquid containing an ammonium salt and an anion with chelating properties. The anion is selected from salicylate, thiosalicylate, acetate, citrate, oxalate, malonate, dicyanoamide and glutarate. The molten organic stream and extractive agent enter an extractor unit operating at a temperature of at least 150°C, where liquid extraction is carried out to obtain a liquid mixture containing ionic liquid and metals. After extraction, the liquid mixture is cooled to a temperature of 0-70°C and it becomes two-phase. The cooled mixture is then fed to the first separation unit to separate the liquid phase containing the ionic liquid and metals and the solid phase depleted in metal. Then, the separated liquid phase is fed into the liquid precipitation and separation unit, adding an anti-solvent, obtaining a solid phase containing metals, and a liquid stream containing the anti-solvent and ionic liquids.

EFFECT: efficient recovery of metals present in organic phases.

18 cl, 1 dwg, 8 tbl, 6 ex

Description

Cross reference to related application

This application claims priority to Italian Patent Application No. 102018000010955, filed on December 11, 2018, the contents of which are incorporated herein by reference in their entirety.

Field of technology to which the invention relates

The present invention relates to a method for the selective recovery of transition metals from an organic stream that can be obtained from petroleum refining processes and/or hydrogenation processes of heavy hydrocarbons, preferably the stream can be obtained from slurry hydrogenation processes (EST) owned by Eni S.p.A.

For purposes of this application, said organic stream is defined as a system containing organic compounds having a boiling point greater than or equal to 340°C, such as aromatic, aliphatic and asphaltene compounds, and solids, carbonaceous residues, metal compounds that may contain transition metal sulfides, such as molybdenum, iron, nickel and vanadium, having dimensions less than a millimeter.

In particular, this method is applicable to solid slurry and wash streams obtained from slurry phase hydrogenation processes, such as, for example, the EST process.

As used in this patent application, the term "wash" means an organic stream in suspension phase that contains hydrocarbons having a boiling point greater than or equal to 340°C, characterized by the presence of asphaltenes in an amount greater than or equal to 5% by weight, and characterized by the presence of solids in an amount greater than or equal to 5% by weight, said solids containing carbonaceous residues, metal compounds, which may contain transition metal sulfides, such as molybdenum, iron, nickel and vanadium, and having dimensions less than a millimeter.

For purposes of this discussion, the term "solid" means the fraction insoluble in tetrahydrofuran and is referred to throughout the application by the acronym THF-i.

For purposes of this discussion, the term "asphaltenes" means the organic fraction that is soluble in tetrahydrofuran but insoluble in n-pentane.

Asphaltenes are classified according to their insolubility in normal paraffinic hydrocarbons (usually having 5 to 7 carbon atoms, C5-C7). These compounds usually consist of nuclei of polycondensed aromatic hydrocarbons, variously branched and united by linear chains. These compounds may contain heteroatoms (S, N) in the cores, which gives asphaltenes polar properties.

As used in this patent application, the term “solid slurry” means a material that is solid at room temperature and has the characteristics of easy grinding and subsequent easy transport even over long distances, without the need for special temperature control. These characteristics are maintained at temperatures ranging from 50°C to 60°C.

Solid slurry is hard at room temperature and has a softening point between 80°C and 100°C and a penetration rate of 2 dmm to 5 dmm (where dmm means 0.1 mm). The softening point is the temperature at which a solid slurry becomes soft and indicates the temperature dependence of the consistency of a solid slurry. The degree of penetration is measured in accordance with the standard method ASTM-D5-06 and is expressed in units of 0.1 mm (decimillimeter) penetration of a needle of a given weight into the material at room temperature.

The consistency of solid sludge is caused by a high concentration of asphaltene compounds relative to the maltenes content.

The solid slurry may contain the above solids containing carbonaceous residues, metal compounds, which in turn may contain transition metal sulfides, such as molybdenum, iron, nickel and vanadium, having dimensions less than a millimeter.

For purposes of this discussion, the term maltenes refers to a number of compounds that are soluble in tetrahydrofuran as well as n-pentane.

For the purposes of this discussion, the EST (Eni Slurry Technology) process owned by Eni S.p.A. for the hydrogenation conversion of heavy petroleum products includes the following steps:

- Supply of a molybdenum-containing catalyst precursor, heavy oil products and a hydrogen-containing stream to the hydrogenation conversion section in the suspension phase;

- Carrying out the process of hydrogenation transformation with the formation of a reaction stream, which is subsequently separated at high pressure and high temperature into a vapor phase and a suspension phase;

- Subsequently, the separated vapor phase is supplied to the gas processing section in order to separate the liquid fraction from the gas containing hydrogen and hydrocarbon gases having from 1 to 4 carbon atoms; wherein said liquid fraction includes naphtha, atmospheric gas oil (AGO), vacuum gas oil (VGO);

- Subsequently, the suspension phase is fed to the separation section for the purpose of separating vacuum gas oil (VGO), heavy vacuum gas oil (HVGO), light vacuum gas oil (LVGO), atmospheric gas oil (AGO), from the heavy organic product stream that contains asphaltenes, unconverted raw materials, catalyst and solid formed during the hydrogenation conversion process;

- Recirculating a portion of said heavy organic products into the reaction section and forming a wash stream with the remainder.

In the EST process, the wash stream may optionally be subjected to chemical or physicochemical treatment to produce a light phase called asphalt tar and a heavy phase called solid slurry.

State of the art

The preferred physico-chemical treatment is the treatment described in WO 2017/109728, which discloses a method for treating refinery wash streams, which includes the following steps:

- collecting a wash stream from a refinery containing a hydrocarbon component in suspension phase having a boiling point greater than or equal to 140°C, characterized in that the amount of asphaltenes present is greater than or equal to 5% by weight and characterized by a content of solids present greater than or equal to 5 % by weight;

- mixing said wash stream, at a temperature greater than or equal to 100°C, with a mixture of hydrocarbons or with a stream which has a total aromatic content between 50% and 70% by weight, and an initial boiling point equal to or greater than the temperature at which mixing is carried out , in order to form a suspension containing greater than or equal to 10% by weight of compounds having a boiling point T _bp less than or equal to 350°C;

- feeding said suspension to a liquid-solid separation step, which is carried out at a temperature greater than or equal to 100°C, releasing a solid phase containing a residual organic component and a solid component, solid slurry, and a liquid containing solid residues;

- cooling the solid phase thus obtained below 60°C, and storing it while maintaining the temperature below or equal to 60°C.

In this method, the ratio of the mass of the washing stream to the mass of the stream is in the range between 1:0.5 and 1:4, and the average residence time of the mixture during mixing and before the separation of liquid and solid is less than or equal to 12 hours.

Additionally, a preferred physicochemical treatment is that described in WO 2018/178927, which discloses a method for physically separating solids and asphaltenes present in refinery wash streams at a conversion greater than or equal to 90%.

Said method involves heating the refinery wash stream at a temperature greater than or equal to 185°C and not higher than 220°C, preferably between 200 and 220°C, wherein said heated wash stream is subsequently subjected to precipitation by successively lowering the temperature, which is controlled down to a minimum a temperature of 100°C, preferably between 100°C and 170°C, more preferably between 100°C and 160°C, without stirring the wash stream, so that a light phase and a heavy phase are formed, depending on their density.

Controlled temperature reduction can occur in various ways:

- using a temperature-controlled container of appropriate size, for example hot oil temperature-controlled, or

- by mixing a hot decanting stream, for example a heated wash stream, with a cold stream, for example bitumen tar, the temperature of which can vary between 200°C and 80°C, taking into account the appropriate heat balance of the system to calculate flow rates.

In the method described in WO 2018/178927, the temperature decrease occurs at a rate ranging from 3°C per minute to 10°C per minute, preferably from 5°C per minute to 10°C per minute, more preferably 10°C per minute minute.

In the method described in WO 2018/178927, the required time for the formation of a heavy phase or solid slurry can vary preferably from 15 minutes to 2 hours, more preferably the time varies between 20 minutes and 1 hour. In the method described in WO 2018/178927, the deposition rate is preferably between 85 mm/hour and 300 mm/hour.

In this patent application, all operating conditions set forth in the text are to be understood as preferred conditions, even if not specifically stated.

For purposes of this discussion, the verb "to construe" or "to include" also includes the expressions "consisting of" or "substantially consisting of."

For the purpose of this discussion, interval definitions always include limit values unless otherwise noted.

Crude oil, the feedstock to the refinery, contains traces of heavy metals. Consequently, organic residual products containing transition metals are formed in oil refining processes. Recycling of these residual products can also address the issue of environmental impact: for example, in cement factories, the concentration of heavy metals increases in the final product, as well as in the environment, if the amount of flue gases is not effectively reduced.

The loss of transition metals also has a significant economic impact, since some metals, such as molybdenum and vanadium, have significant values that are expected to increase as some Far Eastern countries industrialize.

Patent application WO 2014/025561 describes a method for recovering hydrocracking catalyst from an effluent stream leaving a slurry hydrocracking zone. This method provides for the separation of the effluent stream into a first stream containing solvent and bitumen pitch, and a second stream that contains bitumen pitch and catalyst.

Separation can be accomplished by centrifugation, filtration, decantation or by electrostatic separation. The second stream is treated by acid leaching to extract the catalyst to form an aqueous solution and a residue. The aqueous solution is then treated with “anions” to form an insoluble salt, a catalyst, and additional aqueous solution.

US document No. 2013/0247406 describes a comprehensive method that includes:

- the process of valorizing heavy crude oils to convert them into lighter products in the presence of a catalyst;

- an oil and oil removal process in which heavy residues and heavier products produced by the processing of heavy crude oils are separated using a spent catalyst, which will subsequently be recovered;

- catalyst synthesis zone.

The catalyst is isolated by treatment using membrane filtration technology, followed by a thermal removal step of volatile components.

WO 2009/070778 describes a method for recovering metals from spent catalyst used in a slurry process for upgrading heavy oils. According to WO 2009/070778, the phase containing the spent catalyst is subjected to pyrolysis, the pyrolysis residues being brought into contact with an aqueous leach solution containing ammonia and air to dissolve the Group VIB and VIII metals to form a compressed suspension. Said suspension contains at least one soluble metal complex from Groups VIB and VIII, ammonium sulfate and a solid residue containing at least one metal complex from Group VB and coke.

Subsequently, the solid residue containing ammonium metavanadate and coke is separated from the compressed suspension and removed. Some of the Group VIII metals are deposited. Precipitation is carried out at a given pH value in order to selectively precipitate part of the complexes of Group VIB and VIII metals.

US 2010/0122938 relates to a process for separating very fine solid particles of hydrocracking catalyst from a liquid suspension of hydrocarbons, said solid particles being present in an amount between 5% and 40% by weight. The method includes the following stages:

- cooling the slurry stream containing hydrocarbons and solids, preferably to a temperature in the range from 55°C to 75°C; - mixing said cooled stream with a solvent in a solvent/suspension weight ratio in the range from 3:1 to 1:3, with forming a first mixture containing liquid hydrocarbons, a solvent and a stream containing heavy hydrocarbons in which a solid catalyst is encapsulated;

- separating the first mixture in the first centrifuge to form a second mixture containing a small amount of heavy hydrocarbons in which the solid catalyst is encapsulated, and a third mixture containing heavy hydrocarbons in which the solid catalyst is encapsulated;

- separating the second mixture in at least one second centrifuge to form a fourth mixture containing solvent and liquid hydrocarbons, and a fifth mixture containing a significant concentration of heavy hydrocarbons in which the solid catalyst is encapsulated;

- mixing the third mixture and the fifth mixture to form the final mixture;

- drying of the final mixture with the formation of a mixture of hydrocarbons, with impurities of the vapor phase and coke-like solid residue;

- separation of impurities from hydrocarbons and extraction of solid residue.

US Pat. No. 7,790,646 describes a process for converting fine catalyst present in an amount between 5 and 40% by weight and contained in a slurry stream along with heavy oils and coke-like materials from which the catalyst metals are subsequently recovered. This method includes the following stages:

- mixing a suspension containing heavy oils and spent catalyst containing Group VIII and VI metal sulfides with a solvent, preferably in a volume ratio between 0.5/1 and 5/1, preferably at a temperature in the range from 25°C to 80 °C, thus asphaltenes precipitate;

- separation, preferably by decantation and/or centrifugation, of spent catalyst and precipitated asphaltenes from heavy oils and from the solvent;

- transformation of precipitated asphaltenes into coke-like material containing metals, which can be recovered by thermal pyrolysis.

EP 2440635 describes a process for recovering metals from a stream enriched in hydrocarbons and carbonaceous residues, which includes the following steps:

- submitting said stream to primary treatment, which is carried out in one or more stages, wherein said stream is treated in the presence of a fluxing material in a suitable installation, at a temperature in the range from 80°C to 180°C, and subjected to liquid-solid separation so that obtain bituminous pitch consisting of liquid and solid sludge;

- optionally removing from said separated solid sludge a hydrocarbon component which has a boiling point below a temperature in the range from 300°C to 350°C;

- supplying said solid sludge, optionally dried, for secondary heat treatment, which includes:

- flameless pyrolysis at temperatures ranging from 400°C to 800°C;

- oxidation of the pyrolysis residue carried out under oxidizing conditions and at temperatures ranging from 400°C to 800°C.

Patent application US 2010/0326887 describes the separation of non-tacky asphalt tar from a hydrocarbon slurry by distillation treatment, which results in a reduction of vacuum gas oil (VGO) content in the final product below 14% by weight. The solids concentrate at the bottom of the column, forming asphalt pitch.

Mattew T. Clough: in the journal Phys. Chem. 2013, 15, pp. 20480-20495 “Thermal decomposition of carboxylate ILs: trends and mechanism”, described the thermal decomposition of some specific ionic liquids.

WO 2011/090610 describes a method for removing metals from crude oil, which involves contacting said crude oil with an ionic liquid that is immiscible with the oil to extract a mixture containing ionic liquids and metals. Metals that can be removed are alkali metals, alkaline earth metals, transition metals, aluminum, copper, lead, antimony, and combinations thereof. Typical ionic liquids are selected from imidazole, ammonium, phosphonium and pyridine. Thus, the mixtures are separated at a lower temperature than the extraction step to remove the remaining crude oil. A demulsifier can be used at the extraction and separation stage.

WO 2011/090617 describes a method for removing metals from a thermal residue that is kept in contact with an ionic liquid that is immiscible with the residue, thereby forming a mixture containing ionic liquids and metals. Metals that may be present are alkali metals, alkaline earth metals, transition metals, aluminum, copper, lead, antimony, and combinations thereof. Typical ionic liquids are selected from imidazole, ammonium, phosphonium and pyridine. Thus, the mixtures are separated at a lower temperature than the extraction step to remove the remaining crude oil. A demulsifier can be used at the extraction and separation stage.

Extraction is carried out at at least 150°C and subsequent separation is carried out at 80°C. This method allows the extraction of alkali metals, alkaline earth metals, transition metals, aluminum, copper, lead and antimony, preferably nickel and vanadium. Experimental data show that the removal of vanadium and nickel is not selective; whereas iron is removed selectively.

US Patent No. 7,553,406 discloses a method for purifying hydrocarbons containing impurities. Extraction is carried out with an ionic liquid, which is subsequently separated in order to reduce the content of impurities in the hydrocarbons. The ionic liquids used in this method are formed using specially selected cations and anions. The impurities to be removed are sulfur compounds, halide compounds and nitrogen compounds.

WO 2010/116165 describes the removal of mercury from liquid or gaseous hydrocarbons by contacting with a specific ionic liquid; the mixture is then separated.

There are no known methods in the prior art that are capable of effectively recovering metals present in organic phases, especially when said metals are present in low concentration and as insoluble salts in common organic solvents or in aqueous solutions.

Description of the invention

To overcome the disadvantages and limitations of the prior art, the Applicant has developed a process for selectively recovering transition metals, also present as sulfides, from an organic stream, preferably from a material defined as solid slurry, and from a wash stream produced in heavy hydrocarbon hydrogenation processes, more preferably from solid sludge and wash stream produced from Eni's slurry hydrogenation conversion processes using suitable ionic liquids.

The subject matter of this patent application is a method for the selective recovery of transition metals from an organic stream containing transition metals, which includes the following steps:

- melting said organic stream to a liquid state and possibly a first extracting agent if it is solid, wherein said extracting agent consists of an ionic liquid or a mixture of two or more ionic liquids, wherein said ionic liquid contains an ammonium salt as a cation and an anion with chelating properties in as an anion;

b. supplying to a first liquid-liquid extraction unit, operated at a temperature of at least 150° C., said molten organic stream and said first extracting agent, optionally molten, and performing liquid-liquid extraction, producing a liquid mixture containing an ionic liquid , or a mixture of two or more ionic liquids, and metals;

c. after extraction, cooling at a temperature between 0°C (zero degrees Celsius) and 70°C, said liquid mixture, which after cooling becomes two-phase, and subsequently this two-phase mixture enters the first liquid-solid separation unit (L). -T) to separate the liquid phase, which contains ionic liquid and metals, and the solid phase, depleted of metal;

d. after the first separation, the separated metal-depleted solid phase is optionally sent to a washing unit into which a solvent is supplied to remove residual ionic liquid by soaking in the solvent, and a washed metal-depleted solid phase is obtained;

e. supplying the separated liquid phase containing ionic liquids and metals to a liquid phase precipitation and separation unit by adding a counter-solvent, thereby obtaining a solid phase containing metals and a liquid stream containing the counter-solvent and ionic liquids.

Using the described and claimed method, it is possible to advantageously and efficiently extract transition metals present in an organic stream obtained from a refinery or from a heavy hydrocarbon hydrogenation process. Depending on the type of ionic liquid, one or more metals can be selectively extracted.

In this patent application, extraction efficiency is measured by the amount of metals extracted. The amount of metals extracted is determined as the difference between the amount of metals in the organic stream entering the first liquid-liquid extraction unit and the amount of metals contained in the metal-depleted solid obtained after solvent washing.

The extraction efficiency in this patent application is calculated from the amount of metals extracted according to the equation:

[A]

In equation [A]:

m _SDM,OUT = mass of metal-depleted solid obtained after solvent washing;

Me _SDM,OUT = metal concentration in wt.% measured in the metal-depleted solid sample obtained after solvent washing;

m _FR.ORG.,IN = mass of solids contained in the organic fraction;

Me _FR.ORG.,IN = metal concentration in mass% measured in the organic fraction.

This method of calculating extraction efficiency provides the best estimate of metal extraction efficiency, both in operational terms (only the metal extraction step is carried out without precipitation) and in analytical terms (two solids are analyzed, one free of metals and the other with an increased concentration of metals) .

Using the specified metal measurement and efficiency calculation methods, the Applicant estimated the recovery of molybdenum, vanadium, iron and nickel.

Brief description of drawings

Further objects and advantages of the present invention will become clearer from the following description and the accompanying drawings, which are given only as non-limiting examples representing preferred embodiments of the present invention.

Figure 1 illustrates a preferred embodiment of the present invention, wherein (1) denotes an organic stream containing transition metals, preferably a wash stream or solid slurry, which enters the first extractor (A), (16) denotes a fresh ionic liquid that enters the first extractor (A), (2) is a liquid mixture that is cooled in apparatus (B). After cooling, the mixture becomes two-phase, containing liquid and solid phases. Said two-phase mixture is separated in a liquid-solid separator (C) to obtain a metal-depleted solid phase (3) (the expression “metal-depleted solid phase” in this patent application means a phase which, at room temperature, has a reduced metal content compared to starting material, and is enriched with organic components based on carbon and hydrogen) and a liquid phase (7) (that is, a liquid phase that at room temperature contains an ionic liquid and is enriched with metals that were in the starting material). The solid phase (3) is sent to the washing unit (D) with solvent (4) to wash away the ionic liquid, which optionally remains on the solid phase, thus obtaining a metal-free washed solid phase (5) and washing solvent (6), from of which a small amount of ionic liquid can be extracted. The liquid phase containing the ionic liquid and metals (7) enters the liquid-solid precipitation and separation unit (E). An anti-solvent (11) is also supplied to the block (E) in order to precipitate the solid stream (12) containing metals and extract the ionic liquid (8).

The antisolvent containing residual ionic liquid (8) is recovered in the evaporation unit (G) to form antisolvent (14) and a metal-free ionic liquid (10), which is returned to the first extraction unit (A).

Preferably, the evaporation unit may be a flash apparatus or a distillation column.

Best Mode for Carrying Out the Invention

The method for selective recovery of transition metals from an organic stream, which is the subject of the present patent application, will now be described, also with reference to Figure 1.

Organic phases of petroleum refining processes may contain transition metal sulfides, especially if they are produced in petroleum refining processes and/or hydrogenation processes of heavy hydrocarbons. Preferably, the process described and patented in this patent application deals with organic phases that can be obtained in petroleum refining processes and/or in hydrogenation processes of heavy hydrocarbons, preferably in the EST slurry processes owned by Eni S.p.A.

The organic stream may preferably be a wash stream or solid slurry obtained from a heavy hydrocarbon hydrogenation process or an EST process.

The organic stream, preferably a wash stream or solid slurry (1), and a first extracting agent (16) are molten (liquid) and supplied to a first liquid-liquid extraction unit (A) operating at a temperature of at least 150° C.

The first extracting agent (16) consists of an ionic liquid, or a mixture of two or more ionic liquids.

In addition to the ionic liquid, an extracting agent may be present, which is preferably selected from complexing molecules containing a thio group, preferred among these molecules being thiocarbazones, thioureas, mercaptobenzenes and aromatic carboxylic acids containing a thiol group. Among thiocarbazones, dithizone is particularly preferred, thiourea is particularly preferred among thioureas, thiophenol is particularly preferred among mercaptobenzenes, and thiosalicylic acid is particularly preferred among carboxylic acids containing a thiol group.

Ionic liquids that can be used to implement the described and claimed method contain quaternary ammonium or phosphonium salts as a cation and an anion with chelating properties as an anion.

The cation may be selected from an ammonium salt, preferably imidazolinium, pyridinium, tetraalkylguanidinium, uronium, thiouronium; or from a quaternary phosphonium salt. The anion may be selected from an anion with chelating properties, preferably such as salicylate, thiosalicylate, acetate, citrate, oxalate, malonate, dicyanide and glutarate.

More preferably, the ammonium salt is an imidazolinium salt with various substituents.

More preferably, the anion with chelating properties is selected from acetate, salicylate, thiosalicylate, citrate.

Even more preferably, the ionic liquid is selected from (1-butyl-3-methylimidazolinium) acetate,

(1-butyl-3 methylimidazolinium) dicyanoamide,

(1-ethyl-3 methylimidazolinium) salicylate,

(1-ethyl-3 methylimidazolinium) thiosalicylate.

After liquid-liquid extraction, a liquid mixture containing the ionic liquid or mixtures thereof and metals is obtained (2).

The liquid mixture (2) is cooled in a temperature range between 0°C and 70°C, preferably between 10°C and 50°C, even more preferably to room temperature, whereby it becomes two-phase, and subsequently the mixture is sent to the first separation unit ( C) to separate the liquid phase containing ionic liquids and metals (7) and the metal-depleted solid phase (3).

Preferably this separation is carried out using filtration or centrifugation.

After separation, the metal-depleted solid phase (3) can optionally be supplied to a washing unit (D) into which a solvent (4) is supplied to remove residual ionic liquids by storing them in the solvent (6), and obtain a washed metal-depleted solid ( 5).

Subsequently, the separated liquid phase containing ionic liquids and metals (7) is treated in the liquid-solid separation unit (E) with an anti-solvent (11) to extract the metals (12): during counter-extraction, the anti-solvent precipitates the metals (12), separating them from ionic liquids (8).

Preferably, the antisolvent containing ionic liquid (8) may be further recovered in an evaporation unit (G) to form an antisolvent (14) and a metal-free ionic liquid (10), which may be recycled to the first extraction unit (A).

Preferably, the evaporation can be carried out by flash evaporation or distillation.

Transition metals that can be selectively extracted using the described and claimed method are selected from scandium, titanium, vanadium, chromium, manganese, iron, cobalt, nickel, copper, zinc, yttrium, zirconium, niobium, molybdenum, ruthenium, rhodium, palladium, silver, cadmium, lanthanum, hafnium, thallium, tungsten, rhenium, osmium, iridium, platinum, gold and mercury; preferably the metals are selected from molybdenum, vanadium, nickel, cobalt, chromium, manganese and iron.

Step (A), a liquid-liquid extraction, can be repeated many times using different ionic liquids, each time depending on the metal to be extracted.

Additional additives or extracting agents other than the ionic liquids used may be used in the extraction steps, preferably selected from complexing molecules containing a thio group, of which thiocarbazones, thioureas, mercaptobenzenes and aromatic carboxylic acids containing a thiol group are preferred. Among thiocarbazones, dithizone is particularly preferred, thiourea is particularly preferred among thioureas, thiophenol is particularly preferred among mercaptobenzenes, and thiosalicylic acid is particularly preferred among carboxylic acids containing a thiol group.

These additional additives or extracting agents are not ionic liquids.

Preferably, the mass ratio of the organic stream to the ionic liquid, or mixture of ionic liquids, may vary between 1:10 and 1:0.5, more preferably between 1:4 and 1:0.5; more preferably between 1:1 and 1:0.9.

The specified weight ratio does not include additional additives or extracting agents. If additional additives or extracting agents are present, the total amount remains constant because part of the ionic liquid is replaced by part of the additive or extracting agent.

The mass ratio between the amount of organic stream supplied to the first extraction unit and the sum of the amount of ionic liquid or mixture of ionic liquids and the amount of extracting agent preferably ranges from 0.5/1 to 1/1, more preferably between 1.1/1 and 0.9/1, even more preferably equal to 1/1.

The solvent (4) used in the washing step (D) may be selected from methanol and tetrahydrofuran.

The antisolvent used in the liquid-liquid extraction steps subsequent to the first step may be selected from water, ethanol, propanol, and more preferably water.

The operating temperature at which the first extraction can be carried out is preferably between 150°C and 250°C, preferably between 150°C and 220°C, even more preferably between 150°C and 200°C.

The operating temperature at which the first separation can be carried out is preferably between 0°C and 70°C, preferably between 10°C and 50°C, even more preferably at room temperature.

All extraction and separation operations can be carried out at atmospheric pressure, or using a maximum of 15 atmospheres of excess pressure.

The reaction time during the extraction step preferably varies between 4 and 48 hours, more preferably between 8 and 36 hours, even more preferably between 12 and 24 hours, even more preferably the reaction time is 24 hours.

Some examples of application of the present invention will now be described, which are provided for descriptive, non-limiting purposes only, and which represent preferred embodiments of the present invention.

Examples

Six experimental tests were carried out, the operating conditions and results of which are shown in Tables 1 and 2.

These tests were carried out using EST solid sludge produced by static sedimentation of an industrial wash stream as the starting material. The material used has the following physical and chemical characteristics given in Table 1.

Table 1

Solid sludge Physico-chemical characteristics Density at 15°C kg/m ³ 1200 Penetration at 25°C dmm 2 Softening point (ring and ball) °C 107 [VGO] wt.% 15% Elemental composition Carbon wt.% 85.9 Hydrogen wt.% 5.9 Nitrogen wt.% 1.3 Sulfur wt.% 3.9 Molybdenum m.d. by weight 9410 Nickel m.d. by weight 3200 Vanadium m.d. by weight 8150 Iron m.d. by weight 970 HPLC compound classes Saturated wt.% 12.4 Aromatic wt.% 17.7 Resins wt.% 19.4 Asphaltenes wt.% 34.8 Insoluble in THF wt.% 15.8

Extraction stage

The tests were carried out in a 30 ml extractor containing approximately 10-15 g in total, taking into account solid slurry, ionic liquid and possible addition of extracting agent. The system was sealed in nitrogen and heated to operating temperature. Conditions were maintained throughout the extraction. At the end of the test, the pressure in the system was released, cooled and the mixture was unloaded from the reactor.

Separation stage

The cooled extraction stream was processed to produce a solid phase at room temperature (metal-free solid slurry) and a liquid phase (metal-rich ionic liquid). This separation was accomplished by filtration through a Teflon filter having a porosity of 0.45 μm or by centrifugation at 10,000 rpm for 10 minutes.

Washing solids

When the solid phase was recovered by filtration or centrifugation, the solid was washed at room temperature with solvent (approximately 50 ml), recovered by filtration and dried at 100°C overnight (metal-depleted solid).

Metal recovery

When the liquid phase has been recovered from the separation step, it is placed in a 100 ml flask and 50 ml of anti-solvent is added. This anti-solvent precipitates metals and therefore forms a solid phase, which is recovered by filtration with a Teflon filter having a porosity of 0.45 μm and dried at 100°C overnight. On the contrary, the liquid phase switches to the ionic liquid recovery stage.

Ionic liquid recovery

The liquid phase is placed in a 100 ml flask and dried in a rotary evaporator under vacuum at 80°C, recovering the ionic liquid (the thermal stability of which is known) at the bottom of the flask and from the recovery flask an anti-solvent having a boiling point lower than the ionic liquid.

EXAMPLE 1

Table 2 shows the operating conditions used in the extraction in Example 1. In other words, in this experiment, 1-butyl-3methylimidazolinium acetate (ABMI) (supplied by Aldrich, CAS No. [284049-75-8], 95%) is used as ionic liquid (IL). No additional extracting agent (EA) is added to the ionic liquid. The extraction is carried out in a 30 ml reactor, at an initial nitrogen pressure of 2 bar (200 kPa), at 200°C for 24 hours. Inside the reactor are placed 7.50 g of the ionic liquid and 7.50 g of the solid sludge of the EST process described in the previous paragraph.

table 2

Operating conditions for the first extraction Organic flow Solid sludge EST Ionic liquid used BMIM (1-butyl-3-methylimidazolinium) acetate Ionic liquid (IL): CAS No.,
Aldrich No., cleanliness [284049-75-8], 95% Name of extracting agent (EA) - Temperature °C 200 Initial pressure atm abs. 2 Time h 24 Mixing rpm 500 Reactor volume ml thirty Amount of EA inside G 0.00 Number of ILs inside G 7.50 Amount of solid sludge inside G 7.51 First separation L-T: Working conditions Type of separation Filtration 0.45 mm Temperature °C 25°C Solid Washing: Operating Conditions Temperature °C 25°C Solvent Methanol Metal recovery: Operating conditions Temperature °C 25°C Anti-solvent Water Extracted metals Molybdenum % 1.2 Vanadium % 58.1

After 24 hours of the experiment, the reactor is cooled and the contents of the reactor are recovered. When cold, the contents have liquid and solid components. The two phases are separated in accordance with the conditions given in Table 2 in the first section of the liquid-solid separation: Operating conditions.

The separation of the two resulting phases is carried out for example 1 by filtration through a Teflon filter at room temperature. This operation allows you to extract the solid phase on the filter and the liquid phase in the flask.

The liquid phase (i.e., the ionic liquid enriched in metals after extraction) is treated with water as a countersolvent. This anti-solvent causes the metals to precipitate, resulting in a solid/liquid mixture that is separated by filtration (Table 2, in the Metals Recovery: Operating Conditions section).

The solid (depleted of metals after extraction) is washed with methanol, and stored on a filter at room temperature to remove excess absorbed ionic liquid (Table 2, in the section Solid Washing: Operating Conditions).

From the elemental analysis of metals in the original EST Solid Sludge and in the metal-free solid, the % extracted metals are calculated.

Using 1-butyl-3methylimidazole acetate as the ionic liquid, under the extraction operating conditions shown in Table 2, 1.2% molybdenum relative to the content of the original EST Solid Sludge and 58.1% vanadium by weight were recovered.

EXAMPLE 2

Table 3 shows the operating conditions used for the extraction in Example 2. In other words, in this experiment, 1-butyl-3-methylimidazolinium acetate (supplied by Aldrich, CAS No. [284049-75-8], 95%) is used as the ionic liquids (IL). An extracting agent (EA) sepaid (thiourea, technical CAS No. [62-56-6], 99%) is added to the ionic liquid. The extraction is carried out in a 30 ml reactor, at an initial nitrogen pressure of 201 kPa, at 200°C for 24 hours. The reactor is charged with 6.26 g of ionic liquid, 0.76 g of extracting agent and 7.03 g of the EST solid slurry described in the previous paragraph.

Table 3

Operating conditions for the first extraction Organic flow Solid sludge EST Ionic liquid (IL) used BMIM (1-butyl-3-methyl-imidazolinium) acetate Ionic liquid (IL): CAS No., Aldrich No., purity [284049-75-8], 95% Name of extracting agent (EA) thiourea [62-56-6], 99% Temperature °C 200 Initial pressure abs. atm 2 Time h 24 Mixing rpm 500 Reactor volume ml thirty Amount of EA inside G 0.76 Number of ILs inside G 6.26 Amount of solid sludge inside G 7.03 First separation L-T: Working conditions Type of separation Centrifugation 10000 rpm, 10 minutes Temperature °C 100°C Extracted Metals Molybdenum % 0.1 Vanadium % 36.4

After 24 hours of the experiment, the reactor is cooled and the contents of the reactor are recovered. When cold, the contents have liquid and solid components. The two phases are separated according to the conditions given in Table 3.

The separation of the two resulting phases is carried out for example 2 by centrifugation at 10,000 rpm for 10 minutes at 100°C. This operation allows you to extract the solid phase and a separate liquid phase.

The content of metals present in the solid thus extracted is then analyzed.

Using the above equation [A], it turns out that by using 1-butyl-3-methylimidazolinium acetate as the ionic liquid with the addition of thiourea as the extracting agent, under the extraction operating conditions given in Table 3, 0.1% of molybdenum w/w is recovered. content in the initial solid sludge is EST and 36.4% vanadium by weight.

EXAMPLE 3

Table 4 shows the operating conditions used for the extraction in Example 3. In other words, in this experiment, 1-butyl-3-methylimidazolinium acetate (supplied by Aldrich, CAS No. [284049-75-8], 95%) is used as the ionic liquids (IL). An extracting agent (EA) sepaid (dithizone, technical CAS No. [60-10-6], 85%) is added to the ionic liquid. The extraction is carried out in a 30 ml reactor, at an initial nitrogen pressure of 201 kPa, at 200°C for 24 hours. The reactor is charged with 6.34 g of ionic liquid, 0.75 g of extracting agent and 7.09 g of the EST solid slurry described in the previous paragraph.

Table 4

Operating conditions for the first extraction Organic flow Solid sludge EST Ionic liquid (IL) used BMIM (1-butyl-3-methyl-imidazolinium) acetate Ionic liquid (IL): CAS No.,
Aldrich No., cleanliness [284049-75-8], 95% Name of extracting agent (EA) Dithizone, [60-10-6], 85% Temperature °C 200 Initial pressure abs. atm 2 Time h 24 Mixing rpm 500 Reactor volume ml thirty Amount of EA inside G 0.75 Number of ILs inside G 6.34 Amount of solid sludge inside G 7.09 First separation L-T: Working conditions Type of separation Centrifugation 10000 rpm, 10 minutes Temperature °C 100°C Extracted metals Molybdenum % 1.4 Vanadium % 52.8

After 24 hours of the experiment, the reactor is cooled and the contents of the reactor are recovered. When cold, the contents have liquid and solid components. The two phases are separated according to the conditions given in Table 4.

The separation of the two resulting phases is carried out for example 3 by centrifugation at 10,000 rpm for 10 minutes at 100°C. This operation allows you to extract the solid phase and a separate liquid phase. The content of metals present in the solid thus extracted is then analyzed.

Using the above equation [A], it turns out that by using 1-butyl-3-methylimidazolinium acetate as the ionic liquid and adding dithizone as the extracting agent, 1.4% of molybdenum w/w is recovered under the extraction operating conditions given in Table 3 content in the initial solid sludge EST and 52.8% vanadium by weight.

Example 4

Table 5 shows the operating conditions used for the extraction in Example 4. In other words, in this experiment, 1-butyl-3-methylimidazolinium dicyanoamide (available from Aldrich, CAS [448245-52-1], 97%) was used as the ionic liquid (IZH). The extraction is carried out in a 30 ml reactor, with an initial nitrogen pressure of 201 kPa, at 200°C for 24 hours. The reactor is charged with 5.42 g of ionic liquid and 5.45 g of the EST solid slurry described in the previous paragraph.

Table 5

Operating conditions for the first extraction Organic flow Solid sludge EST Ionic liquid used BMIM (1-butyl-3-methyl-imidazolinium) dicyanoamide Ionic liquid (IL): CAS No., Aldrich No., purity [448245-52-1], 97% Temperature °C 200 Initial pressure abs. atm 2 Time h 24 Mixing rpm 500 Reactor volume ml thirty Amount of EA inside G 0.00 Number of ILs inside G 5.42 Amount of solid sludge inside G 5.45 First separation L-T: Working conditions Type of separation Centrifugation 10000 rpm, 10 minutes Temperature °C 100°C Extracted Metals Molybdenum % 28.2 Vanadium % 33.4

After 24 hours of the experiment, the reactor is cooled and the contents of the reactor are recovered. When cold, the contents have liquid and solid components. The two phases are separated according to the conditions given in Table 5.

The separation of the two resulting phases is carried out for example 3 by centrifugation at 10,000 rpm for 10 minutes at 100°C. This operation allows you to extract the solid phase and a separate liquid phase.

The content of metals present in the solid thus extracted is then analyzed.

Using the above equation [A], it turns out that by using 1-butyl-3-methylimidazolinium dicyanoamide as the ionic liquid, under the extraction operating conditions given in Table 5, 28.2% of molybdenum relative to the content in the original Solid Sludge EST is recovered and 33.4% vanadium by weight.

Example 5

Table 6 shows the operating conditions used in the extraction in Example 5. In other words, in this experiment, 1-ethyl-3-methylimidazolinium salicylate is used as the ionic liquid. The extraction is carried out in a 30 ml reactor, with an initial nitrogen pressure of 201 kPa, at 200°C for 24 hours. The reactor is charged with 7.04 g of ionic liquid and 7.13 g of the EST solid slurry described in the previous paragraph.

Table 6

Operating conditions for the first extraction Organic flow Solid sludge EST Ionic liquid used EMIM (1-ethyl-3-methylimidazolinium) salicylate
ethylimidazolinium ethyl-3methylimidazolinium) Salicylate Temperature °C 200 Initial pressure abs. atm 2 Time h 24 Mixing rpm 500 Reactor volume ml thirty Amount of EA inside G 0.00 Number of ILs inside G 7.04 Amount of solid sludge inside G 7.13 First separation L-T: Working conditions Type of separation Centrifugation 10000 rpm, 10 min
10 minutes Temperature °C 100°C Extracted Metals Molybdenum % 36.0 Vanadium % 21.3

After 24 hours of the experiment, the reactor is cooled and the contents of the reactor are recovered. When cold, the contents have liquid and solid components. The two phases are separated according to the conditions given in Table 6.

The separation of the two resulting phases is carried out for example 3 by centrifugation at 10,000 rpm for 10 minutes at 100°C. This operation allows you to extract the solid phase and a separate liquid phase. The content of metals present in the solid thus extracted is then analyzed.

Using the above equation [A], it turns out that by using 1-ethyl-3-methylimidazolinium salicylate as the ionic liquid, under the extraction operating conditions given in Table 6, 36.0% of molybdenum relative to the content of the original EST solid slurry is recovered and 21.3% vanadium by weight.

Example 6

Table 7 shows the operating conditions used for the extraction in Example 6. In other words, in this experiment (IL), 1-ethyl-3-methylimidazolinium thiosalicylate is used as the ionic liquid. The extraction is carried out in a 30 ml reactor, with an initial nitrogen pressure of 201 kPa, at 200°C for 24 hours. The reactor was charged with 7.39 g of ionic liquid and 7.38 g of the EST solid slurry described in the previous paragraph.

Table 7

Operating conditions for the first extraction Organic flow Solid sludge EST Ionic liquid used EMIM (1-ethyl-3-methylimidazolinium)
thiosalicylate Temperature °C 200 Initial pressure abs. atm 2 Time h 24 Mixing rpm 500 Reactor volume ml thirty Amount of EA inside G 0.00 Number of ILs inside G 7.39 Amount of solid sludge inside G 7.38 First separation L-T: Working conditions Type of separation Centrifugation 10000 rpm,
10 minutes Temperature °C 100°C Extracted Metals Molybdenum % 25.5 Vanadium % 29.7

After 24 hours of the experiment, the reactor is cooled and the contents of the reactor are recovered. When cold, the contents have liquid and solid components. The two phases are separated according to the conditions given in Table 7.

The separation of the two resulting phases is carried out for example 3 by centrifugation at 10,000 rpm for 10 minutes at 100°C. This operation allows you to extract the solid phase and a separate liquid phase. The content of metals present in the solid thus extracted is then analyzed.

Using the above equation [A], it turns out that by using 1-ethyl-3-methylimidazolinium thiosalicylate as the ionic liquid, under the extraction operating conditions given in Table 7, 25.5% of molybdenum relative to the content of the original EST solid slurry is recovered and 29.7% vanadium by weight.

When comparing the results of the examples, which are shown in Table 8, it can be seen that by varying the ionic liquid, it is possible to quantitatively change the percentage of metals extracted and more or less selectively extract one metal at the expense of another. In fact, it can be seen that in Examples 1, 2 and 3, where 1-butyl-3-methylimidazolinium acetate is used as the ionic liquid, vanadium is preferentially extracted. With the use of other ionic liquids with different molecular structures, molybdenum can also be extracted along with vanadium.

Claims (29)

1. A method for selectively extracting transition metals from an organic stream having a boiling point greater than or equal to 340°C and containing transition metals, which includes the following steps: a. melting said organic stream to a liquid state and optionally a first extracting agent if solid, wherein said extracting agent consists of an ionic liquid or a mixture of two or more ionic liquids, wherein said ionic liquid contains a quaternary ammonium salt or a quaternary phosphonium salt as a cation and an anion with chelating properties as an anion; b. supplying to a first liquid-liquid extraction unit, operated at a temperature of at least 150° C., said molten organic stream and said first extracting agent, optionally molten, and performing liquid-liquid extraction, producing a liquid mixture containing an ionic liquid , or a mixture of two or more ionic liquids, and metals; c. after extraction, cooling at a temperature between 0°C (zero degrees Celsius) and 70°C said liquid mixture, which after cooling becomes two-phase, and subsequently supplying the two-phase mixture to the first liquid-solid separation unit to separate a liquid phase, which contains ionic liquid and metals, and a solid phase, depleted of metal; d. after the first separation, the separated metal-depleted solid phase is optionally sent to a washing unit into which a solvent is supplied to remove residual ionic liquid by soaking in the solvent, and obtaining a washed metal-depleted solid phase; e. supplying a separated liquid phase containing ionic liquids and metals to a liquid-solid precipitation and separation unit and adding an antisolvent, thereby obtaining a solid phase containing metals and a liquid stream containing the antisolvent and ionic liquids, wherein the anion is selected from salicylate, thiosalicylate, acetate, citrate, oxalate, malonate, dicyanamide and glutarate. 2. The method according to claim 1, where the organic stream is obtained in oil refining processes and/or processes for the hydrogenation conversion of heavy hydrocarbons. 3. The method according to claim 2, where the organic stream is obtained in the “Eni Technological Suspension Process” for the hydrogenation conversion of heavy petroleum products, which includes the stages: - supply of a molybdenum-containing catalyst precursor, heavy oil products and a hydrogen-containing stream to the hydrogenation conversion section in the suspension phase; - carrying out the process of hydrogenation transformation with the formation of a reaction stream, which is subsequently separated at high pressure and high temperature into a vapor phase and a suspension phase; - subsequently, the separated vapor phase is supplied to the gas processing section in order to separate the liquid fraction from the gas containing hydrogen and hydrocarbon gases having from 1 to 4 carbon atoms; wherein said liquid fraction includes naphtha, atmospheric gas oil (AGO), vacuum gas oil (VGO); - subsequently, the suspension phase is fed to the separation section for the purpose of separating vacuum gas oil (VGO), heavy vacuum gas oil (HVGO), light vacuum gas oil (LVGO), atmospheric gas oil (AGO), from the stream of heavy organic products that contain asphaltenes, unconverted raw materials, catalyst and solid formed during the hydrogenation conversion process; - recycling part of these heavy organic products into the reaction section and forming a washing stream with the remaining part. 4. The method according to claim 2, where the organic stream is a wash stream or solid slurry obtained from the hydrogenation conversion of heavy hydrocarbons, where the specified wash stream is an organic stream in a suspension phase, characterized by the presence of asphaltenes in an amount greater than or equal to 5% by weight and the presence of solids in a content greater than or equal to 5% by weight, wherein said solids contain carbonaceous residues, metal compounds, which may contain sulfides of transition metals, such as molybdenum, iron, nickel and vanadium, and are less than a millimeter in size ; and wherein said solid slurry is a solid material at room temperature with a softening point defined as the temperature at which the solid slurry softens, between 80°C and 100°C, and a degree of penetration, measured by the standard ASTM-D5-06 method, from 2dmm to 5 dmm (from 0.2 to 0.5 mm); solid slurry can be crushed and subsequently transported at temperatures ranging from 50°C to 60°C without thermostatic control. 5. Method according to any one of paragraphs. 1-4, wherein the antisolvent containing residual ionic liquids is further recovered in an evaporation unit to form the antisolvent and metal-free ionic liquid, which is recycled to the first extraction step. 6. Method according to any one of paragraphs. 1-5, where the transition metals that are selectively extracted are selected from scandium, titanium, vanadium, chromium, manganese, iron, cobalt, nickel, copper, zinc, yttrium, zirconium, niobium, molybdenum, ruthenium, rhodium, palladium, silver, cadmium, lanthanum, hafnium, thallium, tungsten, rhenium, osmium, iridium, platinum, gold and mercury. 7. The method according to claim 6, wherein the transition metals that are selectively extracted are selected from molybdenum, vanadium, nickel, cobalt, chromium, manganese and iron. 8. Method according to any one of paragraphs. 1-7, where at the extraction stage, in addition to the ionic liquid, an extracting agent selected from thiocarbazones, thiocarbamides, mercaptobenzenes and aromatic carboxylic acids containing a thiol group is used. 9. Method according to paragraphs. 1-8, where the cation is selected from imidazolinium, pyridinium, tetraalkylguanidinium, uronium, thiouronium; or quaternary phosphonium salts. 10. Method according to paragraphs. 1-9, where the ionic liquid is selected from acetate (1-butyl-3-methylimidazolinium), dicyanoamide (1-butyl-3-methylimidazolinium), salicylate (1-ethyl-3-methylimidazolinium), thiosalicylate (1-ethyl-3- methylimidazolinium). 11. Method according to any one of paragraphs. 1-10, where separation is carried out by filtration or centrifugation. 12. Method according to any one of paragraphs. 1-11, where the mass ratio between the organic stream and the ionic liquid, or mixture of ionic liquids, varies from 1:10 to 1:0.5. 13. Method according to any one of paragraphs. 1-12, where the solvent used in the washing step is selected from methanol and tetrahydrofuran. 14. Method according to any one of paragraphs. 1-13, wherein the antisolvent used in the liquid-liquid extraction steps after the first step is selected from water, ethanol, propanol. 15. Method according to any one of paragraphs. 1-14, where the operating temperature at which the first extraction is carried out varies from 150°C to 250°C. 16. Method according to any one of paragraphs. 1-15, where the operating temperature at which the first separation is carried out preferably ranges from 0°C to 70°C. 17. Method according to any one of paragraphs. 1-16, where the extraction and separation stages are carried out at a pressure less than or equal to 15 atm. 18. Method according to any one of paragraphs. 1-17, where the extraction time during the extraction step is from 4 to 48 hours.

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