MXPA00010862A - Process to recover molybdenum and vanadium metals from spent catalyst by alkaline leaching - Google Patents

Abstract

There is provided a process to reclaim molybdenum, vanadium and other hydrodesulfurisation metals from catalysts, said process comprising collecting one or more catalysts containing at least one metal sulfide;leaching the catalyst in an atmospheric alkaline leach step;separating the leached slurry into a first liquid stream and a first solid;leaching the first solid in a caustic pressure leach process;separating the second leached slurry into a second liquid stream and a second solid;collecting the first and second liquid streams;oxidizing the combined liquid stream;cooling the oxidized liquid stream;adjusting the pH of the oxidized liquid stream;contacting the cooled oxidized liquid stream with an organic solvent containing an extractant;stripping the soluble metal speciesfrom the organic phase;adjusting the pH of the aqueous phase to selectively precipitate at least one metal as a metal salt;and separating the metal salt from the aqueous phase.

Description

PROCESS TO RECOVER METALLIC MOLYBDENUM AND VANADIUM FROM A SPENTED CATALYST, BY ALKALINE LEACHING TECHNICAL FIELD The present invention relates to a process for recovering products from a spent catalyst, in particular to recover and regenerate metals, oils and alumina-rich fuel products from catalysts used for the processing of petroleum. BACKGROUND OF THE INVENTION Petroleum hydrocarbons (oils) in and on spent catalysts are known to inhibit the economics of metal recovery. The oils present in the catalysts block the pores of the catalyst and require more severe conditions to oxidize the surface metals through hydrometallurgical oxidation. In addition, the oils cause undesirable organic contamination in the leaching processes and in the recovered products. The methods commonly used to remove the oil from the catalysts, such as thermal oil removal or calcination, are not satisfactory, which causes the alumina to react with the metals at high temperature and Ref: 124721 finally reduce the performance of metals. The white metals for regeneration are commonly recovered after the removal of the petroleum coke generated during its use. The coking of the thermally treated catalyst does not limit the recovery of the metals, but it can have an impact on the processing kinetics due to the plugging of the pores of the catalyst. The coke can have an impact on the reaction kinetics of heat treatment by decreasing the diffusion rate due to plugging of the pores of the catalyst. The removal of coke is expensive and requires a high processing temperature of 400 to 800 ° C. At higher temperatures, the reaction is very fast, making the process impossible to perform in a gradual and controlled manner. In addition, the process, which is exothermic on the surface of the catalyst, causes a thermal stress on the surface of the catalyst and makes the metals less soluble species, for example forming spinels. Therefore, a process at a lower temperature and controlled is desirable. To comply with current standards, for example a total regeneration, the oil must be recovered in the form of a commercial product. The oil can not be transformed into a waste stream in the oil removal process. In conventional treatments at high temperature, the oil is burned with the coke, emitting carbon dioxide, carbon monoxide and byproducts of sulfur oxide and nitrogen. A more robust regeneration process minimizes air emissions and provides oil recovery in the form of a value-added product. The metals present in the catalyst are present in the form of a range of sulphides located in a variety of surface geologies. Some of the metal sulfides are easily oxidized to the air at room temperature, but other metal sulfides may require high temperatures and oxygen pressures to oxidize. DESCRIPTION OF THE INVENTION The present invention relates to an integrated process for the treatment of catalysts comprising vehicles containing alumina and a metal or metals, wherein the catalysts contain oil, to recover said metal or metals therefrom, in wherein the process comprises the steps of: a) Collecting one or more catalysts, wherein the catalyst (s) contains two or more metals in the form of metal sulfides, wherein at least two of the metal sulfides are a molybdenum sulfide and a sulfide of vanadium, or a tungsten sulfide and a sulfide of vanadium; b) remove the oil from the catalyst; c) leaching the catalyst (s) to which the oil was removed, in the presence of caustic soda and oxygen at atmospheric pressure, at a lower temperature 60 ° C and at a pH range of 10 to 13, for a time I sufficient to transform in a range of 50 to 70% the at least two metal sulfides in soluble metal and sulfur, thus forming a first leached slurry comprising a first liquid stream containing the soluble metal and the sulfur species and a first solid; d) separating the first leached slurry in the first liquid stream and the first solid; e) leaching the first solid in the presence of caustic soda and oxygen at a partial pressure of oxygen greater than 60 kPa (10 psia), at a temperature higher than 70 °, and at a pH greater than 10, for a sufficient time to transform more 90% of the at least two metal sulfides in soluble metal and sulfur species, based on the metal sulfides present in the catalyst (s) before the passage of part (c), thereby forming a second leached slurry comprising a second liquid stream containing the soluble metal and sulfur species and a second solid; (f) separating the second leached slurry in the second liquid stream and the second solid; g) collecting the first liquid stream and the second liquid stream to form a combined liquid stream; h) oxidizing the combined liquid stream in the presence of oxygen or air or both, thereby forming an oxidized liquid stream; i) cooling the oxidized liquid stream and adjusting the pH to 6.5, thereby precipitating the dissolved alumina and separating said alumina from the oxidized liquid stream; j) adjusting the pH of the oxidized liquid stream to a pH of 2.5; k) contacting the oxidized liquid stream with an organic solvent containing an effective extractant to transfer the soluble metal species to an organic species, thereby creating an organic phase containing at least one soluble metal and an aqueous liquid substantially free of metals containing sulfate; 1) recovering the aqueous liquid substantially free of metals containing sulfate; m) distilling the soluble metal species from the organic phase in the presence of an aqueous solution of ammonia, thereby forming an aqueous phase containing the metal species; n) adjusting the pH of the aqueous phase to selectively precipitate at least one metal in the form of at least one metal ammonium salt; o) separating the metal ammonium salt from the aqueous phase and recovering said metal ammonium salt. DETAILED DESCRIPTION OF THE INVENTION The present invention is a process for recovering metals from a spent oil refining catalyst, without dissolving significant amounts of the catalyst matrix. A variety of catalyst sources can be used in the process; being a common characteristic of the catalysts that are made with vehicles of alumina, alumina-silica or silica-alumina. Without limiting the scope of the present invention, the process will be described by an example of petroleum processing catalysts and, for simplicity, in particular a mixture of alumina-based petroleum catalysts (hydrotreating catalysts), such as a catalyst supply. Residual / HDS catalyst, with vanadium (V), nickel (Ni), cobalt (Co) and molybdenum (Mo) or tungsten (W) as predominant metals, present in the form of metal sulphides. The process according to the present invention solubilizes the metal sulfides while maintaining the majority of the alumina in the form of a solid. The amounts of metals, in the form of metal sulfides, in each catalyst source are easily determined. The common metals present in the hydrotreating catalysts include Mo or W, Co, V and Ni. In a preferred embodiment, sulphides are present in the form of at least two sulfides, such as eg Mo or W and V sulfide. The supply can be mixed with a predetermined metal mixture., for example Mo + V or with a V / Mo ratio. Certain catalysts, for example the hydrodesulfurization catalyst (HDS), undergo oxidation reactions when exposed to air. When an HDS catalyst is processed, it must be mixed with a catalyst containing heavy oils, such as a residual catalyst, to provide a protective oil coating to assist handling before and during the initial process steps. It has been found that a mixture of 75:25 to 50:50 residual catalyst: HDS catalyst works well in the process. A preferred mixture is 75:25. As mentioned, a residual catalyst typically arrives containing free oil, while an HDS catalyst typically contains less oil. It is desirable to remove the oils as one of the stages of the initial process. The HDS catalyst must remain dry before the oil removal process, where the term "dry" as used herein, means free of water. A mechanism to remove the oil is a solvent removal, which removes the petroleum hydrocarbons (oils) present in the catalyst supply without removing the coke. Deep removal greater than 98% is achieved by removing the oil in the presence of an organic solvent, such as toluene or xylene. Since the catalyst can become very reactive when the oil is removed, it is preferred to remove the oil under an inert atmosphere, such as nitrogen. The elimination of the oil can be accelerated by increasing the temperature, but this increases the cost since it becomes necessary to use a pressure vessel. Therefore, oil removal becomes a matter of time versus cost consideration, where an oil removal time of less than 12 hours is desirable. After removing the oil, the solvent is distilled from the raw material, still under a nitrogen atmosphere, and the oil is separated from the solvent and recovered for later use. The oil removing step of the present invention minimizes the dissolution of the catalyst matrix and does not remove the coke.

I The raw material to which the oil was removed and distilled from solvent can be washed with a moderately caustic substance, such as sodium hydroxide under conditions that minimize oxidation, thereby forming a first slurry. The first slurry has a preferred pH of about 10-12. The temperature during the grout phase is maintained below the boiling point of the water. In order to facilitate the kinetics of dissolution, the catalyst can be crushed before or after removing the oil and / or forming the slurry, to improve the economy of the process in the solid / liquid separation stages and to increase the control of the process in the oxidation stages. The catalysts to which the oil was removed are highly reactive and are typically cooled to room temperature or near room temperature to be crushed. If the catalyst to which the oil was removed is crushed, it may be desirable to cool the catalyst with an inert gas, such as nitrogen, and then make a slurry with a mild caustic before grinding. The choice of whether to grind or how much to grind in the process is related and depends on the equipment used. If the catalyst particles are very large, they could get stuck in the equipment and / or cause erosion problems as they flow through the equipment. If the crushing is too small, the particles later may require more elaborate solid / liquid separation techniques. The metals present in the catalyst are present in the form of a family of metal sulfides (e.g., NiS, V2S3, MoS2, CoS). A key to the process according to the present invention is to control the reaction of the sulfides (S2 ~) to soluble thiosulfates (S2032_). The oxidation of the insoluble sulfide to soluble thiosulfate is controlled quantitatively using a mild caustic oxidation. Sodium thiosulfate is a kinetically stable oxidation product under conditions of less than 40 ° C (105 ° F), 103 kPa (15 psia) 02 and pH 12-13. Sulfides will oxidize to sulfate at relatively low speeds when temperatures are between 40-66 ° C (105-150 ° F), the pH between 11-12 and the pressure of 02 greater than 207 kPa (30 psig). Thiosulfate becomes very unstable at temperatures above 148 ° C (300 ° F), at pressures of 02 greater than 414 kPa (60 psia) and pH less than 10.5, and sulphides will be completely converted to sulfate under these conditions. Thiosulfate decomposes quantitatively and / or disproportionately at pH lower than 9, higher than 90 ° C (194 ° F) and / or partial pressure of 02 higher than 207 kPa (30 psia), obtaining products such as sulfur, sulphites , sulphides or sulfates. The raw material to which the oil was removed, distilled and possibly crushed and grout, is subjected to leaching in an atmospheric leaching process. To maintain control of the thiosulfate, the pH of the leach must be adjusted to a value greater than 9 before introducing atmospheric leaching. Preferably, the leaching is carried out in the presence of caustic soda and air or oxygen, at atmospheric pressure, at a temperature of less than 60 ° and at a pH range of about 10 to 13. The pH must be strictly controlled because if it falls too low the control of the leaching reaction is lost. Loss of control is thought to occur in the following way: As the thiosulfate is oxidized to sulfates, an acid is formed, the pH falling and requiring the continuous addition of caustic soda to maintain the pH required for caustic leaching. Any acid formed in the pores of the catalyst particles can create a regime in which the chemistry of the pore is very different from that of the bulk. The alumina vehicle will begin to dissolve as the conditions become more acidic. The solubilized alumina can subsequently precipitate and block the pores, or it can coprecipitate with the soluble vanadium species present in solution. Part of the vanadium co-precipitated with alumina is lost unless the alumina is resolubilized. Thiosulfate control allows this process to be controlled, reducing the need to add caustic soda. The atmospheric caustic leaching is carried out for a sufficient time to transform a range of approximately 50 to 70% of the sulfides into soluble thiosulfate and sulfate species, thus forming a first leached slurry. The pH is maintained at a value of approximately 10 to 12. An advantage of this pH range is that certain metals that may be present but that are not going to be recovered at this stage of the process, such as Fe, Ni or Co, do not They are soluble at this pH. Although the atmospheric leaching process can be carried out in one stage, two to three stages are preferred, with a residence time of one day in each day. The use of more than one atmospheric leaching stage allows the leaching conditions to vary at each stage for optimal control of leaching and oxidation reactions. Care must be taken in selecting the residence time, because if it is too long, the thiosulfate could be oxidized to sulfate. Open tanks can be used, since only atmospheric pressure is desired. The first leached slurry is separated into a first liquid stream, which contains the solubilized metal and sulfur species, and a first solid. With the first solid a slurry can be formed in the manner described above, with freshly prepared mild caustic soda, to form a second slurry. The first solid is transferred to a pressure vessel for pressure leaching, where the air or oxygen pressure and temperature are increased to dissolve the residual metal sulfides that exist in less soluble chemical forms or that are less accessible due to the particle morphology. Although a pressure leaching stage can be used employing temperatures greater than 70 ° C and partial oxygen pressures greater than 69 kPa (10 psia), it has been found that two stages of pressure leaching are effective. In a first pressure leaching, the first solid of the first leach is subjected to a temperature of about 75 ° C and 10 psia of oxygen. Since the thiosulfate reacts to form sulphate with acid or with temperature or with oxygen pressure, the residence time is kept to a minimum. The total residence time in the first pressure leach vessel is about 90 minutes. After the first pressure leaching, the slurry is sent to a solid / liquid separation stage.

The removed water, which contains Mo, V and some soluble S2032 ~ is not subjected to the second pressure leaching. Freshly prepared caustic soda can be added to the solids and these, plus the caustic soda if added, are sent to a second pressure leach vessel. The second pressure leaching is carried out at a temperature of about 120 ° C and 241 kPa (35 psia) of 02. The pH is maintained at a value of about 11. The residence time is about 90 minutes. Solids recovered after a second solid / liquid separation process are substantially free of S, Mo and V, where the term "substantially free" as used herein, means removal rates as high as about 98% of the sulfur, approximately 97% of molybdenum and approximately 92% of vanadium. The metals (Mo and V) and the soluble sulfur species removed from the solids during the atmospheric and pressure leaching stages are contained in the waters. The waters of the different separation stages are collected to form a stream of combined waters. This liquid stream contains completely oxidized metals (MoVI and Vv) as well as soluble reduced metal species such as VIV. The combined liquid stream is oxidized, preferably with oxygen or air. It has been found that a bubble column works well as an oxidation vessel, although standard autoclaves can also be used. The oxidation stage in solution completely oxidizes the soluble metals to their highest oxidation state and transforms any thiosulfate to sulfate. Oxidation is carried out at a pH of less than 10, at temperatures greater than 150 ° C and at a pressure of 02 / air greater than about 345 kPa (50 psia). At this stage it is desirable to allow the thiosulfate to oxidize to sulfate in order to lower the pH of the waters. The liquid stream of the oxidation process in solution is controlled to a white pH of > 6.5 through the oxidation zone and an exit pH of approximately 6.5. If the reaction S032 ~ - * S04 ~ does not decrease the pH sufficiently, an acid such as sulfuric acid (H2S04) can be added to reach the desired exit pH. The resulting oxidized solution is maintained at a pH of about 6.5 while cooling, to allow traces of alumina that have dissolved during the caustic leaching process to precipitate. An additional benefit is that as the alumina precipitates, it co-precipitates contaminants such as arsenic and phosphorus. Essentially, this maintenance and cooling step is a purification step to improve the subsequent metal recovery stages and to avoid the presence of contaminants in the desired final metal products. After cooling, the precipitated solids are removed and the pH adjusted to a value of about 2.5, for example by the addition of sulfuric acid. The recovery of the soluble species of vanadium and molybdenum is carried out in a liquid-liquid ion exchange process. The water stream is contacted with an organic solvent, which contains an extraction agent, such as an amine. The metals are bound to the amine in the organic phase. The liquid-liquid ion exchange can be carried out in a single stage; however, it has been found that two or three steps produce a final aqueous refining that is substantially free of metals. The use of a countercurrent flow is effective in the extraction process. The organic phase containing the metals is sent to a distillation circuit, where the organic phase is contacted with a solution of aqueous ammonium molybdate at a pH of about 6 and the molybdenum and vanadium are extracted into the aqueous solution of ammonium molybdate. The vanadium is recovered from the aqueous solution with high molybdenum content by the addition of a sufficient amount of ammonium hydroxide to increase the pH and precipitate the ammonium metavanadate (NH4V03). After the removal of the precipitate, a portion of the liquid stream is distilled to remove the ammonia. The pH of the resulting solution is lowered to about 2.5, sufficient to precipitate the molybdenum in the form of ammonium molybdate (NH4) 4MOs026 '4H20, or similar species). The ammonium metavanadate is subsequently washed and calcined to transform it into V2Od and / or V203, and the ammonium molybdate is calcined to generate Mo03. Ammonia is recovered during calcination. In the example that is being described herein, solids recovered after the pressure leaching and solid / liquid separation stages contain Ni and / or Co. The controlled oxidation process previously described is effective for preparing recovered solids for leaching selectively not substantially free of contamination by other catalyst metals, such as V, Mo and Co. Ni can be dissolved using an ammonia leaching process. Ni ammonia leaching from reduced metal ores is a common practice that is typically done in an autoclave at a pH of 9 to 10. To recover the nickel, ammonia and part of the CO 2 from the leach solution are distilled. reduce the pH to a value of about 7 and precipitate the nickel in the form of a basic nickel carbonate. This process works well for reduced cobalt and nickel in low oxidation states, although it is very difficult to recover the nickel separated from any amount of cobalt present. Although conventional ammonia / ammonium carbonate leaching processes typically used for the recovery of nickel or cobalt in reduced metal ores can be used, a variation has been found that allows the recovery of nickel with a low cobalt content from the solids generated in the process of leaching by caustic oxidation. In the present invention, the process of caustic oxidation in the early stages of processing, results in highly oxidized nickel and cobalt species and less soluble in the resulting solids, compared to what is normally found in other nickel recovery processes . It is thought that this process leaves cobalt in a more oxidized and less soluble state than nickel. In the present invention, the nickel leaching is carried out at a pH range of about 10.5 to 12 in a solution of ammonia / ammonium carbonate NH40H / (NH4) 2C03), at temperatures in the range of about 40 to 80 ° C. At this pH range, free ammonia is generated above the buffer capacity of ammonium hydrocarbonate, which allows the solubilization of oxidized nickel species and minimizes the solubilization of the more highly oxidized cobalt species present in solids. The ammonia leaching solution containing the solubilized nickel and amine complex is subsequently distilled with heat to remove the ammonia. As the ammonia is removed, the pH decreases to a value of about 10 to 10.5 and a basic nickel carbonate is precipitated. The basic nickel carbonate may also contain residual vanadium species that were not solubilized in the above caustic oxidation stages. The precipitate is separated from the distilled water and can be further purified by subjecting it to sulfuric acid at a pH of less than 4 and at temperatures of up to 80 ° C to dissolve the basic nickel carbonate. After filtering the sulfuric acid solution to remove the insoluble metal impurities, the sulfuric acid solution containing the soluble nickel is treated with sodium hydroxide or with sodium carbonate to increase the pH to a value higher than 8 and to precipitate hydroxide of nickel (Ni (OH) 2) or nickel carbonate (NiC03) as a product. The remaining leached solids are dehydrated to remove residual ammonia. The leached solids I are substantially free of metals and sulfur, but they contain the coke, which is not removed in the process of the present invention. The coke remaining in the alumina catalyst makes these solids attractive as a rich alumina fuel product to be used as raw material for other processes such as cement kilns. In addition, any residual metal remaining in the solids after the leaching processes described, exists in insoluble forms that exclude solids from a classification as hazardous waste, in accordance with current standards. It will be apparent to those skilled in the art that numerous changes and modifications can be made to the present invention without departing from the spirit or scope thereof. It is noted that in relation to this date, the best method known to the applicant to carry out the aforementioned invention, is that which is clear from the present description of the invention.

Claims (9)

1. CLAIMS Having described the invention as an antecedent, the content of the following claims is claimed as property: 1. A process for regenerating metals from catalysts comprising vehicles containing alumina and a metal or metals, wherein the catalysts contain oil, characterized because it comprises: a) collecting one or more catalysts, wherein the catalyst (s) contains two or more metals in the form of metal sulfides, wherein at least two of the metal sulfides are a molybdenum sulfide and a vanadium sulfide; or a tungsten sulfide and a vanadium sulfide; b) remove the oil from the catalyst; c) leaching the catalyst (s) to which the oil was removed, in the presence of caustic soda and oxygen at atmospheric pressure, at a temperature below 60 ° C and at a pH range of 10 to 13, for a sufficient time to transforming the at least two metal sulfides into soluble metal and sulfur into a range of 50 to 70%, thereby forming a first leached slurry comprising a first liquid stream containing the soluble metal and the sulfur species and a first solid; d) separating the first leached slurry in the first liquid stream and the first solid; e) leaching the first solid in the presence of caustic soda and oxygen at a partial pressure of oxygen greater than 60 kPa (10 psia), at a temperature higher than 70 ° C and at a pH greater than 10, for a sufficient time to transform more 90% of the at least two metal sulfides in soluble metal and sulfur species, based on the metal sulfides present in the catalyst (s) before the passage of part (c), thereby forming a second leached slurry comprising a second liquid stream containing the soluble metal and sulfur species and a second solid; (f) separating the second leached slurry in the second liquid stream and the second solid; g) collecting the first liquid stream and the second liquid stream to form a combined liquid stream; h) oxidizing the combined liquid stream in the presence of oxygen or air or both, thereby forming an oxidized liquid stream; i) cooling the oxidized liquid stream and adjusting the pH to 6.5, thereby precipitating the dissolved alumina and separating said alumina from the oxidized liquid stream; j) adjusting the pH of the oxidized liquid stream to a pH of 2.5; k) contacting the oxidized liquid stream with an organic solvent containing an effective extractant to transfer the soluble metal species to an organic species, thereby creating an organic phase containing at least one soluble metal and an aqueous liquid substantially free of metals containing sulfate; 1) recovering the aqueous liquid substantially free of metals containing sulfate; m) distilling the soluble metal species from the organic phase in the presence of an aqueous solution of ammonia, thereby forming an aqueous phase containing the metal species; n) adjusting the pH of the aqueous phase to selectively precipitate at least one metal in the form of at least one metal ammonium salt; o) separating the metal ammonium salt from the aqueous phase and recovering said metal ammonium salt.
2. 2. A process according to claim 1, characterized in that it further comprises leaching the second solid in an aqueous solution of ammonia to place at least one metal in solution, thereby forming a solution containing metal and a second solid leached; and subjecting the metal-containing solution to conditions sufficient to precipitate the at least one metal in the form of at least one metal salt.
3. 3. A process according to any of claims 1 or 2, characterized in that the vanadium is precipitated in the form of a first metal ammonium salt in the step of subsection (m) and further comprises removing the free ammonia from the aqueous phase of the stage of subsection (n); subjecting the aqueous phase to an effective pH to precipitate a second metal in the form of a second metal ammonium salt; separating the second metal salt of ammonium from the aqueous phase; and recover the second metal salt of ammonium.
4. 4. A process according to any of the preceding claims, characterized in that the catalyst (s) is mixed before the stage of part (b); wherein with the catalyst (s) a slurry with a caustic substance is formed prior to the step of part (c); and wherein with the first solid a slurry with freshly prepared caustic soda is formed before the step of part (e).
5. 5. A process according to any of the preceding claims, wherein the catalyst (s) contains oil and coke; characterized in that the removal of the oil is carried out in the presence of at least one organic solvent, thereby removing at least 95% of the oil present without removing the coke; and further comprises distilling the solvent from the material to which the oil was removed prior to the step of part (c).
6. 6. A process according to claim 5, characterized in that the catalyst is a petroleum refining catalyst, preferably a hydrotreating catalyst, more preferably a hydrodesulfurization catalyst and / or residual catalyst; and wherein the catalyst also contains metal sulfides that are selected from the group consisting of cobalt sulfide, nickel sulphide, and combinations thereof.
7. A process according to any of claims 5 or 6, characterized in that a slurry with a caustic substance is formed with the catalyst (s) before the step (c) and with the first solid a slurry with soda is formed caustic freshly prepared before the step of step (e), and wherein each stage of slurry is carried out at a pH in the range of 10 to 12 and under conditions to control oxidation.
8. 8. A process according to any of claims 5, 6 or 7, characterized in that the oxidation step is carried out at a temperature higher than 150 ° C and the pH of the oxidized liquid stream is controlled to a higher value of 6.5.
9. 9. A process according to any of the preceding claims, characterized in that it also comprises removing the ammonia retained in the second solid leached, to obtain an alumina residue.