Claims:
1. A process for solvent extraction comprising, simultaneous separation of vanadium and tungsten from sodium molybdate leach liquors or similar solutions using a secondary carbon primary amine, the process comprising of following steps:
a. Contacting the aqueous feed solution with an organic solvent comprising a secondary carbon primary amine to form organometallic complex of amine “ a term called loaded organic (LO)” with vanadium and tungsten;
b. Back extracting (Stripping) the organometallic complex (loaded organic) with alkali solution to release V, W and co-extracted Mo in strip solution thereby regenerating the metal free organic solvent “ a term called Barren solvent (BS)”;
c. Washing the regenerated barren solvent with water to remove the free alkali entrained within it;
d. Recycling the washed barren solvent to the extraction step again.

2. The process for solvent extraction as claimed in claim 1, wherein the organic extractant is a secondary carbon primary amine of the general formula RR´CH-NH2, where R and/or R´ is an aliphatic hydrocarbon group may be straight or branched chain from approximately 12 to 24 carbon atoms.

3. The process for solvent extraction as claimed in claim 1, wherein the organic phase contains an extraction solvent which is preferably a secondary carbon primary amine;
a polar modifier dissolved in aliphatic diluent selected from but not limited to a polar improving agent of C8-C13 alcohols like isodecyl alcohol or similar alcohols and combinations thereof;
diluents selected from but not limited to sulphonated kerosene or kerosene or Exxol D80 (Trade mark of ExxonMobil) or a diluent containing aliphatic hydrocarbon group(s).

4. The process for solvent extraction as claimed in claim 1, wherein the organic phase contains at least an extraction solvent in the range of 2 to 30% volume percentage, at least a polar modifier in the range of 2 to 30% volume percentage and a diluent in the range of 40 to 96% volume percentage.

5. The process for solvent extraction as claimed in claim 1, wherein the leach liquor processed by this invention are spent HDS catalysts or similar materials containing 3-200 g/L Mo and up to 11 g/L V and W, such leach liquors have an acidity ranging from 7 to 7.5 pH.

6. The process for solvent extraction as claimed in claim 1, wherein the extraction occurs at a pH ranging from 7 to 7.5 and results in > 99.8% removal of V and W as organometallic complex of amine and <4% of Mo is co-extracted.

7. The process for solvent extraction as claimed in claim 1, wherein back extraction of the organometallic complex with alkali solution occurs at a pH ranging from 8 to 12 with a stripping efficiency of Mo >99%, V >99.5% and W >99.8%; and
wherein the strip solution contains total metal values of Mo, V and W up to approximately 150 g/L depending on the varying V and W impurity levels.

8. The process for solvent extraction as claimed in claim 1, wherein stripping the organometallic complex is performed under alkaline conditions using alkalis selected from but not limited to alkali ammonia, sodium carbonate, ammonium carbonate, ammonium bicarbonate, ammonium chloride; and mixture of thereof and the like.

9. The process for solvent extraction as claimed in claim 1, wherein the aqueous and organic phase ratio in extraction step are present in the range of 5:1 to 1:5.

10. The process for solvent extraction as claimed in claim 1, wherein the recycling step is continuous and the barren solvent from stripping step is fed to extraction step after washing.

11. A single step process of solvent extraction comprising, simultaneous removal of vanadium and tungsten impurities from sodium molybdate leach liquors or similar solutions using at least a primary amine to recover high purity Mo solution.
, Description:
FORM 2
THE PATENTS ACT, 1970
(39 of 1970)

&

THE PATENT RULES, 2003

COMPLETE SPECIFICATION
[See Section 10, Rule 13]

1.: TITLE OF THE INVENTION
Simultaneous extraction and separation of vanadium and tungsten from molybdate Leach solution by solvent extraction

2. APPLICANT
a) Name : Rubamin Pvt. Ltd.
b) Nationality : Indian
c) Address : Ark, 4th Floor, 1 Krishna Industrial Estate, opp. BIDC Gate, Gorwa, Vadodara, Gujarat 390016, India

PREAMBLE TO THE DESCRIPTION
The following specification particularly describes the invention and the manner in which it is to be performed.

FIELD OF INVENTION
The present invention relates to the simultaneous extraction and separation of vanadium and tungsten impurities mostly found as contaminants in molybdate leach solutions generated from the treatment of spent hydrotreating, hydro cracking and hydro desulphurization (HDS) catalysts /or similar raw materials using a secondary carbon primary amine by solvent extraction.

BACKGROUND
Catalysts are extensively used in the petroleum refinery and petrochemical industries to eliminate sulfur and toxic metal ions like V, Ni, Fe and Cu etc. from various kinds of organic matters existing in various ratios.

Most of these catalysts consist of molybdenum (Mo) containing active metal coated on alumina / or alumina-silica supports. Over time, with the continuous usage of the catalysts, they get exhausted as the impurities gradually start to accumulate. Such impurities include Vanadium (V) and Tungsten (W) amongst others. As these impurities accumulate, the catalysts become more and more ineffective and are considered as spent.

Such spent catalysts bearing high levels of impurities are considered hazardous and require to be treated and handled as per strict regulations prior to disposal. Such treatment and handling are rather costly and result in the loss of substantial volume of valuable metal components thereby resulting in the depletion of natural resources.
It is for this reason that recovering such metals from the spent catalysts has become a subject of great interest in the recycle and reuse industries.

Typically, the most suitable approach to process such spent catalysts is hydrometallurgy, wherein the spent catalyst undergoes alkali leaching/soda roasting followed by water leaching. After leaching V and W are co-leached with the Mo leach solution as impurities due to their similar chemistry. High value Mo products cannot be made from this type of leach solutions without removal of V and W. Removal of these V and W impurities is essential to make high value Mo products. Total concentration of V and W in Mo leach solution remains approximately 3 g/L. The ion exchange resin technique cannot remove such high concentration of impurities due to its lesser loading capacity. The conventional known method for removal of V and W impurities is by precipitation technique. But this is also associated with high solid precipitate generation, multi-step operation and loss of Mo. Therefore, solvent extraction is the preferred and appropriate technique for the removal of such a high V and W impurities from Mo leach solution to make high grade Mo products.

Currently, the processes available either use non selective extractants such as Primene JM-T or Aliquat®336, for targeted metals like V and W, or fail to disclose a single step extraction process for removal of vanadium and tungsten simultaneously from molybdate leach solution.

US 4774003 relates to an Ion exchange extraction of metallic and non-metallic anions by control of the basicity of amine extractants. This process utilizes Primene JM-T as the extractant and fails to disclose a single step extraction process for simultaneous removal of vanadium and tungsten from molybdate leach solution.
US4514369A relates to the co extraction of Mo, V and W using quaternary ammonium salt extractant (Aliquat 336). It has no selective separation of V and W over Mo. The downstream process disclosed in the US patent involves the removal of V using excess ammonium salt addition to precipitate V as Ammonium metavanadate (AMV) product. W from the remaining filtrate bearing Mo was precipitated by lime. Making high grade Mo product using this process is very difficult and high Mo loss during W precipitation is inevitable. The subjected process has multiple steps and possesses tedious operation.
US4500495 relates to the extraction of all the metals i.e., Mo, V and W using quaternary ammonium salt extractant (Aliquat 336). Hence it has no selectivity of V and W extraction over Mo. In the downstream process, all the metals are stripped into solution and V is precipitated by HCl. Mo and W are recovered by evaporation. Therefore, high grade Mo compounds cannot be obtained using this process. The above process has multiple steps and is tedious in operation.
EP0262953A2 relates to the recovery of molybdenum from a solution containing molybdenum and vanadium as ammonium octa-molybdate in a form that is substantially free from vanadium. In this process both Mo and V are co extracted using quaternary ammonium compound extractant and stripped of vanadium and molybdenum with an ammonium bicarbonate solution. To the resultant strip solution, ammonium sulfate is added to form a crop of ammonium metavandate crystals. The process does not mention the presence of W along with V and Mo. The patent fails to disclose selectivity of V and W extraction over Mo therefore pure Mo products cannot be made by using this process.

US4814149 relates to a process for recovering molybdenum from solution that is substantially free from vanadium. In this process both Mo and V were co extracted using quaternary ammonium compound extractant (Aliquat 336) and stripped of both vanadium and molybdenum with an ammonium bicarbonate solution that approached saturation. V is crystallized as ammonium metavandate crystals by adding ammonium sulfate. This process fails to disclose any presence of W in the leach solution, only V and Mo bearing leach solution are disclosed handled. Further, the patent involves no selectivity of V and W over Mo.
EP1080239B1 describes a process to recover molybdenum and vanadium metals from spent catalyst using an organic solvent which contains an extractant, such as an amine. This involves the co extraction of V and Mo and the leach solution also does not contain W. The metal-containing organic solvent is sent to a stripping circuit, where the organic phase is for example contacted with an aqueous ammonium molybdate solution and the molybdenum and vanadium are extracted into the aqueous ammonium molybdate solution. The vanadium is then recovered from this high molybdenum aqueous solution by addition of ammonium hydroxide sufficient to increase the pH and precipitate ammonium metavanadate (NH4VO3). The ammonium metavanadate crystals precipitated cannot be avoided from the contamination of Mo. After removal of the vanadium precipitates, Mo is recovered as ammonium octamolybdate by lowering pH. High grade Mo product cannot be made using this process. In this process there is no selectivity of V and W over Mo.

Other inventions include processes as disclosed in patents US9273377B2, US7736607 inter alia. These processes involve vanadium removal from Mo through ammonium metavanadate precipitation by adding ammonium salt. In these processes there is no mention of W impurities. US4298581 discloses precipitation of all the elements V, W and Mo as their calcium compounds.
All processes discussed above, fail to disclose a single step extraction process of vanadium and tungsten for selective removal over molybdenum. Nor do these processes disclose a less tedious and simple continuous route. Also, only technical grade Mo products can be prepared using the aforementioned processes and it is very difficult to prepare pure Mo products.

It is evident from the aforementioned examples that extensive research has been conducted in this field especially towards a single step, simultaneous and selective separation, cost effective and simple operational process.

Therefore, there is a need for a process which can solve at least one of the problems as disclosed above.

OBJECT OF INVENTION
It is therefore an object of this invention to provide a solvent extraction process to simultaneously and selectively separate vanadium and tungsten impurities from a molybdate leach solution or such other solution generated from leaching of spent hydrotreating, hydro cracking and hydro desulphurization (HDS) catalysts /or similar raw materials using a primary amine, preferably a secondary carbon primary amine.

It is also an object of this invention to provide for a simultaneous solvent extraction separation process for removal of V and W from molybdate leach solution.

Another objective is to provide a single step solvent extraction process which can deal with large volumes of molybdate leach solution bearing higher concentration of V and W impurities.

Another objective is to provide a solvent extraction separation process which is cost effective, easy to operate, simple continuous process having higher through put, requiring no heat, therefore lesser energy consumption.

Another objective is to provide a solvent extraction separation process having less capex.

SUMMARY OF INVENTION
A process for solvent extraction comprising, simultaneous separation of vanadium and tungsten from sodium molybdate leach liquors or similar solutions using a primary amine, the process comprising of following steps:
a. Contacting the aqueous feed solution with an organic solvent comprising a primary amine to form organometallic complex of amine “a term called loaded organic (LO)” with vanadium and tungsten and very little co-extracted Mo.
b. Back extracting (Stripping) the organometallic complex (loaded organic) with alkali solution to release V, W and very little co-extracted Mo in strip solution thereby regenerating the metal free organic solvent “a term called Barren solvent (BS)”.
c. Washing the regenerated barren solvent with water to remove the free alkali entrained within it.
d. Recycling the washed barren solvent to the extraction step again
Wherein, the primary amine is preferably but not limited to a secondary carbon primary amine of the general formula RR´CH-NH2, where R and/or R´ is an aliphatic hydrocarbon group may be straight or branched chain containing approximately 12 to 24 carbon atoms.

A single step process of solvent extraction comprising, simultaneous removal of vanadium and tungsten impurities from sodium molybdate leach liquors or similar solutions using at least a primary amine to recover high purity Mo solution.

BRIEF DESCRIPTION OF DRAWINGS
FIG. 1 is a representation of the process flow associated with embodiments of the present invention;

FIG. 2 is a representation of a schematic diagram of continuous solvent extraction operation associated with the embodiments of the present invention; and

FIG. 3 is a tabular representation of the content information on % composition of V, W & Mo in the Feed & strip raffinate along with other details such as the solvent flow, ratio of aqueous: organic phase, number of extraction stages, % extraction of V, W & Mo and stripping efficiency.

DETAILED DESCRIPTION
Various embodiments of the present invention have been disclosed herein in an attempt to fully and completely disclose the scope of the present invention to those skilled in the art. As may be used in the present specification, single forms “a”, “an”, “the”, inter alia, shall be read to include plural referents unless the context dictates otherwise.

Embodiments of the present invention disclosed herein provide a process for solvent extraction comprising, simultaneous separation of vanadium and tungsten from sodium molybdate leach liquors generated from leaching of spent hydrotreating, hydro cracking and hydro desulphurization (HDS) catalysts /or similar raw materials using a primary amine. Wherein, the primary amine is preferably, but not limited to a secondary carbon primary amine of the general formula RR´CH-NH2, where R and/or R´ is an aliphatic hydrocarbon group may be straight or branched chain containing approximately 12 to 24 carbon atoms.

In an embodiment of the present invention, the process of solvent extraction comprises of following steps:
Extraction: Contacting the aqueous feed (Molybdate leach solution) containing vanadium and tungsten as impurities, with an organic solvent comprising a primary amine to form organometallic complex of amine with vanadium and tungsten, thereby resulting in > 99.8% removal of Vanadium and Tungsten as organometallic complex of amine into the organic solvent wherein % co-extraction of Mo is <4%. The extract raffinate containing Molybdenum and Na2SO4 is further processed to recover molybdenum in pure form. The above mentioned extraction process is carried out at a neutral equilibrium pH ranging from 7 to 7.5.
Back extraction: Back extracting (Stripping) the organometallic complex (loaded organic) generated in the abovementioned extraction step, with alkali solution having a pH from 8 to 12 to release vanadium, tungsten and very little co-extracted molybdenum in strip solution thereby regenerating the metal free organic solvent (Barren solvent) as explained in the process flow sheet of Figure 1.

Wherein, the organometallic complex (loaded organic) is contacted with alkali solution and generate strip solution containing a total metal values of Molybdenum, Vanadium and Tungsten of up to <150 g/L and has a pH 8 to 12 depending on the varying Vanadium and Tungsten impurity levels. The stripping efficiency of Molybdenum is >99%, Vanadium is >99.5% and Tungsten is >99.8% resulting in regenerated barren organic solvent.

In one of the embodiment of the present invention, stripping the organometallic complex is performed under alkaline conditions using alkali selected from but not limited to alkali ammonia, sodium carbonate, ammonium carbonate, ammonium bicarbonate, ammonium chloride; and mixture of thereof and the like. Strip solution is having Mo, V, W and the medium is NaOH. The alkali solution used in the present invention has a pH ranging from 8 to 12, such alkali solution may be selected from but not limited to sodium or ammonia form.

Washing: Washing the barren solvent with water to remove any traces of entrained free alkali. The washing step is performed at room temperature and pH 7.5 – 9 wherein, the organic to aqueous phase ratio is 5:1 to 10:1.

Recycling of barren solvent: After washing the barren solvent regenerated from the back extraction step mentioned above, the said solvent is recycled back to the extraction step as depicted in Fig. 2.

In one of the embodiments of the present invention, the recycling step is continuous.

In a further embodiment of the present invention, the process disclosed herein, may be used to simultaneously extract vanadium and tungsten from molybdate leach solution but not limited to the selected concentrations of the present invention and can be extended to varying concentrations by changing the concentration of extractant and modifier in diluents, number of stages of extraction and organic to aqueous phase ratios.

In one of the embodiments of the present invention, the organic phase containing the extraction solvent, a polar modifier and diluents, comprises of the volume percentage of each component as 2 to 30% extraction solvent, a polar modifier 2 to 30%, 40 to 96% diluent.

The organic solvent of the solvent extraction process disclosed herein, preferably comprises of secondary carbon primary amine of the general formula RR´CH-NH2 as extraction solvent, where R and/or R´ is an aliphatic hydrocarbon group, which may be straight or branched chain consisting from approximately 12 to 24 carbon atoms. The solvent further comprises a modifier dissolved in aliphatic diluents such as EXXOl D80. The modifier is a polar improving agent of C8-C13 alcohols like isodecyl alcohol or similar alcohols combinations thereof. The diluent used is selected from but not limited to a sulphonated kerosene or kerosene or Exxol D80 (Trade mark of ExxonMobil) or a diluent containing aliphatic hydrocarbon groups.

In one of the embodiments of the present invention, the aqueous and organic phase ratio in extraction step are present in the range of 5:1 to 1:5.
In one of the embodiments of the present invention, the aqueous phase comprises of Vanadium, Tungsten and Molybdenum together and along with Na2SO4.

In one of the embodiments of the present invention, the leach liquor contains 16-20 g/L of Molybdenum and up to 3 g/L Vanadium and Tungsten together and the strip solution contains 21-28 g/L of Molybdenum, 40-48 g/L of Vanadium and 17-59 g/L of Tungsten depending on the varying Vanadium and Tungsten impurity level in the spent catalyst raw material. The proposed process can be extended to impurity content of about 3% Vanadium and Tungsten containing Molybdenum raw materials by varying solvent concentration, aqueous: organic phase ratios and number of extraction stages.

Figure 3. details a complete solvent extraction process streams in a tabular format with process parameters such as leach liquor acidity, separation of vanadium, tungsten impurities, phase ratio, number of stages, stripping conditions for solvent regeneration and strip solution.

Exemplary concentrations of tungsten and vanadium in the solutions to which the methods of the present disclosure are applicable can vary. In certain embodiments, the total concentration of vanadium and tungsten in the aqueous solution is about 11 g/L.

In certain embodiments of the present invention, the leach liquor processed by this invention are spent spent hydrotreating, hydro cracking and hydro desulphurization (HDS) catalysts /or similar raw materials. Exemplary concentrations of the tungsten and vanadium in these solutions to which the methods of the present disclosure are applicable can vary from 3-200 g/L Mo and up to 11 g/L V and W, such leach liquors have an acidity ranging from 7 to 7.5 pH.

The invention is not limited thereto, and other exemplary solutions that can be advantageously treated according to the process of the present invention include, but are not limited to, a process comprising of solvent extraction for simultaneous removal of vanadium and tungsten impurities from sodium molybdate leach liquors or similar solutions to recover high purity Mo solution is provided.

According to a further embodiment of the invention, there is provided a single step process comprising of solvent extraction for simultaneous removal of >99.8% vanadium and tungsten impurities from molybdate leach solutions or similar solutions to recover high purity Mo solution.

General reaction of the process disclosed in the present invention may be explained as here under:
2RNH2 + H2SO4 = (RNH3)2+SO42-

Specifically, the chemical reaction for Tungsten may be explained as:
5(RNH3)2+SO42- + H10W12O4610- = (RNH2 )10H10 (H10 W12O46 ) + 5SO42-

Specifically, the chemical reaction for Vanadium may be explained as:
3(RNH3)2+SO42- + 2V3O93- = 2(RNH2)3H3V3O9+ 3SO42-

Specifically, the chemical reaction for Molybdenum may be explained as:
(RNH3)2+SO42- + MoO42- = (RNH2)2 H2MoO4+ SO42-
Wherein, R is a Secondary carbon.

Advantages of the present disclosure are summarized as follows:
- It is a simultaneous solvent extraction separation process for removal of V and W from molybdate leach solution.
- It is a single step solvent extraction process which can handle large volumes for separation of V and W impurities from molybdate leach solution.
- This process which can take care higher concentration of V and W impurities.
- This process is cost effective, ease to operate,
- This process is a simple and continuous process having higher through put,
- This process requires no heat, so lesser energy consumption.
- This is not an acidic operative process, therefore possesses less capex.

WORKING EXAMPLES
EXAMPLE 1
Extraction of vanadium and tungsten: Leach liquor containing Mo 15.55 g/L, V 0.956 g/L and W 1.06 g/L, pH value of 7.26 was contacted with the organic phase at 5 countercurrent stages, an organic phase and an aqueous phase volume flow ratio of 1:1.2, to obtain a raffinate and vanadium and tungsten bearing organic phase, wherein the raffinate after extraction containing tungsten 0.019 g/L, vanadium 0.001 g/L resulting in 99.9% V, 98.21% W extraction efficiency. The organic phase containing V, W and little co-extracted Mo after countercurrent extraction is back-extracted using NaOH strip feed at pH 10.4, 2 countercurrent stages, an organic phase and an aqueous phase the volume flow ratio of 10:1. Stripping efficiency achieved for Mo 99.26%, V 99.48% and W 99.84%.

In this step, the organic phase volume percentage of each component as 8% extractant, 8% polar modifier, 84% diluent, were used. The stripping step consists of NaOH solution maintained at pH 10.4 and recycled to get desired load of metals (total load of Mo, V and W approximately 150 g/L). This solution is withdrawn periodically and equivalent quantity of water is added to maintain the volume, then with NaOH top up to achieve the required back extraction pH.

EXAMPLE 2
Extraction of vanadium and tungsten: Leach liquor containing Mo 15.53 g/L, V 0.479 g/L and W 0.204 g/L, pH value of 7.4 was contacted with the organic phase at 4 countercurrent stages, an organic phase and an aqueous phase the volume flow ratio of 1:3, to obtain a raffinate and vanadium and tungsten bearing organic phase, wherein the raffinate after extraction containing tungsten 0.004 g/L, vanadium 0.001 g/L resulting in 99.79% V, 98.04% W extraction efficiency. The organic phase containing V, W and little co-extracted Mo after countercurrent extraction is back-extracted using NaOH strip feed at pH 11, 2 countercurrent stages, an organic phase and an aqueous phase the volume flow ratio of 10:1. Stripping efficiency achieved for Mo 99.27%, V 99.86% and W 99.97%.
In this step, the organic phase volume percentage of each component as 8% extractant, 8% polar modifier, 84% diluent, were used. The stripping step consists of NaOH solution maintained at pH 11 and recycled to get desired load of metals (total load of Mo, V and W approximately 150 g/L). This solution is withdrawn periodically and equivalent quantity of water is added to maintain the volume, then with NaOH top up to achieve the required back extraction pH.

EXAMPLE 3
Extraction of vanadium and tungsten: Leach liquor containing Mo 18.13 g/L, V 1.4 g/L and W 1.7 g/L, pH value of 7.1 was contacted with the organic phase at 6 countercurrent stages, an organic phase and an aqueous phase the volume flow ratio of, 1:1, to obtain a raffinate and tungsten bearing organic phase, wherein the raffinate after extraction containing tungsten 0.015 g/L, vanadium 0.001 g/L resulting in 99.79% V, 99.12% W extraction efficiency. The organic phase containing V, W and little co-extracted Mo after countercurrent extraction is back-extracted using NaOH strip feed at pH 9, 2 countercurrent stages, an organic phase and an aqueous phase the volume flow ratio of 10:1. Stripping efficiency achieved for Mo 99.00%, V 99.64% and W 99.76%.

In this step, the organic phase volume percentage of each component as 8% extractant, 8% polar modifier, 84% diluent, were used. The stripping step consists of NaOH solution maintained at pH 9 and recycled to get desired load of metals (total load of Mo, V and W approximately 150 g/L). This solution is withdrawn periodically and equivalent quantity of water is added to maintain the volume, then with NaOH top up to achieve the required back extraction pH.