GB2130566A - Recovering metals from spent hydroprocessing catalysts - Google Patents

Abstract

Metal values, including at least one metal of Group VIII and at least one metal of Group Vb or Group VIb of the Periodic Table, contained in spent hydroprocessing catalyst particles are recovered by first roasting the particles at between 400 and 600 DEG C and then leaching them with a first aqueous solution of ammonia and an ammonium salt to form a first pregnant liquor. The once-leached catalysts are leached with a second aqueous solution of sulfur dioxide forming a second pregnant liquor. The metal values are precipitated from this with hydrogen sulfide and this is roasted with unroasted spent hydroprocessing catalysts. The metal values of Group Vb and Group VIb in the first pregnant liquor are transferred into a first organic solution by liquid ion exchange. The first organic solution is stripped by an aqueous strip solution and the metal values separated by sequential precipitation. The metals of Group VIII are separated and purified by serial liquid ion exchange.

Description

SPECIFICATION Recovering metals from spent hydroprocessing catalysts This invention relates to methods of recovering metals from spent hydroprocessing catalysts.

One modern development in crude oil processing is the upgrading of metal and sulfur containing feedstocks, e.g., crude oils and residua by hydroprocessing methods. Such upgrading is necessary to convert the heavy feedstock into more valuable, lower boiling fractions and to remove contaminants, particularly metals and sulfur, that can pollute the atmosphere upon combustion.

Crude oils contain various dissolved contaminants, including nickel, vanadium, iron, and sulfur. The lighter fractions are frequently distilled off under atmospheric pressure or a partial vacuum leaving the metals in a high boiling fraction generally called the "residual fraction," or "residua." Residua will generally contain at least 35 ppm metal contaminants, frequently as high as 100 ppm, and in extreme cases, higher than 1000 ppm.

These metals and any sulfur present are removed, thereby upgrading the feedstock, by processing the feedstock, with a catalyst, in the presence of hydrogen. Such catalysts are generally a solid support that contains catalytic metals, generally either molybdenum or tungsten with either nickel or cobalt. As the catalyst is used, metals from the feedstock deposit on its exterior surface and the interior surface of its pores, eventually plugging the pores and reducing the activity of the catalyst to such an extent it does not give the desired product quality. Such catalysts are herein defined as "spent catalysts," and contain catalytic metals, an inorganic support matrix, metals removed from the feedstock, sulfur compounds, and a hydrocarbonaceous residuum.

Recently, the obtainable crude oil is tending to be heavier, forcing refiners to use more hydroprocessing catalysts than heretofore necessary to remove metals and sulfur from the feedstock. A shortage of the valuable catalytic metals, particularly cobalt, is therefore possible. In an effort to recycle both the catalytic metals and the catalyst supports, providing a renewable source of catalytic metals, efforts have been made to extract metals from hydroprocessing catalysts, particularly hydrodesulfurization and hydrodemetalation catalysts.

One general method of leaching hydroprocessing catalysts is disclosed in U.S. Patent No. 3,567,433. An aqueous ammonia and ammonium salt leach solution is contacted with spent catalyst particles. The conditions of the system were not optimized, resulting in low metals recovery.

Another leaching process is disclosed in ChemicalAbstracts, 94:178649x. A spent catalyst, containing aluminum, vanadium, nickel, cobalt, and molybdenum, was leached with ammonia and ammonium salts, at a temperature greater than 110 C and an oxygen partial pressure of greater than 1 kg/cm2, for more than 1/2 hour.

Other methods of recovering metals from spent demetalation or desulfurization catalysts are known. U.S.

Patent No. 4,216,118 discloses chlorinating spent catalysts to convert vanadium values to vanadium tetrachloride and nickel values to nickel chloride for recovery by solvent extraction. U.S. Patent No. 4,145,397 discloses recovery of metals from spent catalysts by roasting at high temperatures and leaching with caustic alkali.

An article in Engineering and Mining Journal, May 1978, page 105, describes a plant to process spent catalysts containing no cobalt by first eaching with sodium hydroxide and then with ammonium carbonate.

Cobalt is a particularly difficult metal to remove from hydroprocessing catalysts by conventional aqueous leaching techniques. Under optimum leaching conditions, an aqueous leach solution of ammonia and an ammonium salt rarely removes more than about 50 percent of the cobalt present on the spent catalyst. It has now been discovered in accordance with the invention that if the spent catalysts are leached by a first aqueous solution of ammonia and ammonium salt and subsequently leached by a second aqueous solution having sulfur dioxide dissolved therein, total recovery of cobalt can be well over 90 percent of the metal present on the initial spent catalyst.

According to the invention, there is provided a process for recovering the metal values from spent hydroprocessing catalyst particles where said values include at least one first metal from Group VIII of the Periodic Table and at least one second metal from Group Vb or Group Vlb of the Periodic Table, said process comprising:: (a) roasting the particles in an atmosphere containing molecular oxygen in a temperature in the range from 400"C to 6000C; (b) leaching the particles with a first aqueous solution containing ammonia and an ammonium salt at a temperature less than the atmospheric boiling point of said first aqueous solution, thereby forming a first pregnant liquor and once-leached particles; (c) separating the once-leached particles from the first pregnant liquor; (d) leaching the once-leached particles with a second aqueous solution containing sulfur dioxide, thereby forming a second pregnant liquor and twice-leached particles; (e) separating the second pregnant liquor from the twice-leached particles; (f) precipitating metal sulfides from the second pregnant liquor by the addition of hydrogen sulfide;; (g) roasting said precipitated metal sulfides with fresh spent catalyst in step (a); (h) transferring the metal values contained in the first pregnant liquor of said second metal into a first organic solution by liquid ion exchange; (i) stripping said metal values from said first organic solution with a first aqueous strip solution; (j) separating said metal values by sequential precipitation; (k) selectively transferring the metal values of said first metal from said first pregnant liquor into at least one second organic solution by serial liquid ion exchange; and (I) stripping each of said second organic solutions to form single metal containing aqueous solutions.

Leaching Metals deposited on hydroprocessing catalysts, and in particular the combination of nickel, cobalt, molybdenum and vanadium, can all be removed simultaneously from spent hydroprocessing catalysts by the use of an aqueous leach solution of ammonia and an ammonium salt. Spent hydroprocessing catalysts can be regarded as a high grade ore that contains a peculiar metals composition. Leaching is the method of choice for metals removed from this particular ore since the supports are porous and the metals individually are all known to be leachable; however, to simplify downstream separation of the metals and allow maximum recovery of the inorganic support matrix intact, the leaching conditions chosen should not allow iron, a frequent contamination of oil, or the inorganic support to be leached.

One of the more valuable metals in spent catalyst is cobalt. Typically, less than 50 percent of the cobalt on the catalyst is leached with an aqueous solution of ammonia. It has been found that by contacting the once-leached catalyst from an ammonia leach with a second aqueous leach having sulfur dioxide (SO2) dissolved therein, it is possible to recover greater than 90% of the total initial amount of cobalt present on the unroasted spent catalyst.

To simplify downstream processing, it is preferable to process one aqueous metals-containing stream.

The best choice, for processing, is an aqueous ammoniacal stream. To place the metals leached by the aqueous SO2 solution into the ammoniacal solution, the metals are precipitated as sulfides. The metal sulfides so recovered are mixed with unroasted spent catalyst and reroasted and releached with the first aqueous ammoniacal solution. The first pregnant liquor, the metals-containing product of the first aqueous solution, therefore will have an equilibrium value of cobalt greater than that if the feed were only spent catalysts.

The spent catalyst, as it comes from the catalytic reaction vessel, is highly contaminated with carbonaceous deposits, also termed "coke," and sulfur. These contaminants are easily removed by combustion in an atmosphere containing molecular oxygen, for example, air, but it has been found that the amount of metals leached from the catalyst particles, particularly nickel, tends to suffer if the catalyst is roasted attoo high a temperature. Preferable conditions for reaction with oxygen are at less than 600"C, preferably between 400"C and 500 C. Temperature can be controlled by diluting the oxygen with nitrogen or by other methods known to the art. The catalyst so treated is free from substantial carbonaceous residue and the metals contained therein can be easily removed by a first aqueous leach.The first aqueous leach solution is a solution of ammonia and an ammonium salt. Such a solution will be alkaline, which is preferred to solubilize vanadium and molybdenum, and will contain free ammonia, an effective complexing agent for nickel and cobalt. Ammonia and ammonium carbonate solutions are especially well suited as they allow reagent recycle by means of distillati- af the pregnant liquor and reabsorbtion in fresh or recycle aqueous solution. Ammonium sulfate is another preferred ammonium salt for the practice of this invention. Nickel and cobalt will be free cations and form ammine complexes, and tnolybdenum and vanadium will be in the form of anionic oxide ions and will form ammonium salts.

The catalyst support of the spent catalyst particles will frequently be alumina. However, mixtures of alumina with other refractory inorganic oxides, for example, silica, boria, magnesia and titania, as well as supports that contain naturally occurring alumina-containing clays, for example, kaolin or halloysite, may be leached by the process of this invention.

It will be understood that the catalyst will typically be in the form of uniformly shaped particles, elongated extrudates or spherical particles. Other shapes may be processed by the method of this invention. The catalyst may be crushed or otherwise processed to change its shape before the application of this invention.

In a buffered system such as the ammonia and ammonium salt leach system, two factors must be adjusted for optimal extraction: the concentration of leaching species and the pH of the leach solutions. The solution must contain sufficient ammonia to complex the nickel and cobalt present, and sufficient ammonium to control pH. The pH should be not lowerthan 9.5, or molybdenum and vanadium recoveries suffer, and not higher than 11, or nickel and cobalt recoveries suffer. A concentration of ammonia NH3(aq), hereinafter ammonia, plus NH4+(aq), hereinafter ammonium, not exceeding 6 molar and having the ammonia concentration approximately equal to the ammonium concentration meets these requirements. It is preferred that the solution have at least a six-fold molar ratio of ammonia compared to the amount of cobalt ion plus nickel ion calculated to be on the spent catalyst particles. The molar concentration of the ammonium salt should not exceed about 2 molar, otherwise a vanadium complex precipitates. An especially preferred leach system is one where the ammonia concentration is initially substantially equal to the ammonium ion concentration and both species are present in about 2 molar concentrations.

It has been observed that the length of time of the leach is importantfor maximum cobalt yield. To maximize cobalt recovery, the catalyst particles should not be in contact with the leach solution for more than fifteen minutes. The temperature of the leach is also important. In general, the higher the temperature, the more any particular species will go into solution; but a practical upper limit is the boiling point of the solution at atmospheric pressure, above which a pressure vessel would be required. In practice, a temperature of between 85"C and 95"C is found to be optimal.After 15 minutes at about 85"C, the leach solution will typically contain more than 85 percent of the molybdenum, 75 percent to 80 percent of the nickel, 75 percent to 85 percent of the vanadium, and at least 45 percent of the cobalt. (These percentages refer to the amount by weight of metal in solution compared to the amount of metal that was on the spent catalyst before leaching.) Less than 0.1 percent of the alumina is extracted and less than 5 percent of the iron is extracted.

The once-leached catalyst particles are then removed from the first pregnant liquor and contacted with a second aqueous solution of sulfur dioxide made by either bubbling SO2 directly into the leach tank or by separately making an aqueous solution of SO2 and passing this premade solution into the leach tank. The temperature of this solution should be between 65"C to 1 00 C and preferably between 80"C and 100C.

Preferably the pH is maintained in the range from 2.5 to 3. Since it is preferred to leach as much metal as possible with as little solution as possible, it is preferred that the second solution be as nearly saturated in SO2 as possible.

The twice-leached catalyst is then removed from the second pregnant liquor and the metals dissolved therein are precipitated by addition of hydrogen sulfide to the solution. It has been observed that the typical metals precipitated are nickel, about 5 percent; molybdenum and vanadium, about 2 percent; and cobalt, about 35 percent; where percent refers to the amount present on the unroasted catalyst. The precipitated metal sulfides are removed from the second pregnant liquor and mixed with unroasted spent catalyst. The mix is roasted and leached with ammonia. The temperature of the second pregnant liquor should be cooled to between 10"C and 30"C before precipitation with H2S. A concentration of about 0.1 molar H2S in the second pregnant liquor will precipitate the metals of interest rapidly.

The alumina support of the catalyst tends to be leached into the second aqueous solution. Typical amounts can be as high as 10 percent of the total alumina. Since iron is not precipitated by hydrogen sulfide, this invention provides an easy separation of the valuable catalytic metals from the less valuable contaminant metals.

Extraction of molybdenum and vanadium The first pregnant liquor from the ammoniacal leach is extracted sequentially with several liquid ion exchange reagents. The metal ions of interest can be divided into two categories. In the first category are metals from Group VIII, in particular cobalt and nickel, which are present in the pregnant liquor as cations. In the second category are metals selected from Group V and Group VI, in particular molybdenum, tungsten and vanadium, which are present in the pregnant liquor as oxyanions. In the practice of the present invention the oxyanions are extracted first. The metal values of Group V and Group Vl are transferred into a first organic solution by a first liquid ion exchange. The extraction can be carried out directly on a pregnant liquor from an ammonia and ammonium salt leach solution.This solution typically has a pH of 10 to 10.5. The preferred organic extractant is a quaternary ammonium compound of the general formula RR'3N+CI-, where R is methyl and R' is a group ranging from C8 to C12. Such organic extractants are sold by Henkel Corporation under the Trade Mark Aliquat 336 and by Sherex Chemical Company, under the Trade Mark Adogen 464, and obtainable from Aldrich Chemical as an 1npure compound of methyl tri-capryl ammonium chloride.

The quaternary ammonium compounds are in organic solution, preferably in hydrocarbon solution, for example, kerosene, which may be conditioned by paraffinic alcohol such as decanol. Contacting the aqueous phase with the anion exchange reagent extracts both the molybdenum and the vanadium. The reaction can be generally depicted as:

where x andy are small whole numbers, typically between 0 and 10, and M is any Group V or Vl metal oxyanion, and R can be any organic substituentthat makes the quaternary amine sufficiently hydrophobic. It has been observed that when Aliquat 336 is the anion exchange reagent, the extraction tends to be equilibrium limited by molybdenum.In practice it has been found that the use of multi-stage extraction units extracts molybdenum more readily than single stage extractions.

Stripping and recoverying vanadium and molybdenum values The metals are then stripped from the organic phase into aqueous phase by an aqueous solution of bicarbonate or carbonate solutions or other anion. A preferred stripping solution is saturated aqueous solution of ammonium bicarbonate at a pH of about 8 and a temperature of O"C to 30"C. It has been observed that the stripping tends to be limited by vanadium. When vanadium is known to be present, the bicarbonate strip solution has been found to be particularly well suited for stripping vanadium values from the organic phase.

When the overall process involves leaching spent catalysts with an aqueous solution of ammonia and an ammonium salt, it is preferred that the stripping solution be a saturated solution of ammonium bicarbonate.

In this way new ions are not introduced into streams, allowing easy recycling of the streams to earlier steps in the process. Ammonium is preferred since ammonium meta-vanadate is a preferred product of this process.

Vanadium, if present, can be recovered from the aqueous solution by adjusting its pH to about 7 by addition of concentrated HCI. The chloride ion has been found to be important for the kinetics of the vanadium metavanadate precipitate. See the method discussed in Zhurnal PrikladnoiKhimii, 43, p. 949-954, 1970. Excess ammonium chloride is added to the aqueous solution and any ammonium chloride not dissolved is removed by filtration creating saturated ammonium chloride solution. The solution is warmed to 75 to 80"C for 20 minutes then cooled slowly over a period of about 30 minutes to about 30"C. The solution is further cooled to about 0 C for three hours. Crystals are collected while the solution is cold by filtration and washed with cold H2O.

The resulting aqueous solution may contain either molybdenum or tungsten or no metals at all. The molybdenum or tungesten can be recovered by reducing the volume of the solution until the metals start to precipitate. The precipitation can be aided by adding an appropriate ion to form a less soluble salt, for example, calcium hydroxide may be added to precipitate the less soluble calcium molybdate.

Extracting and recovering cobalt and nickel The Group VIII metals, still in the first pregnant liquor solution, are each selectively placed into an organic solution, by serial liquid ion exchange. Each organic solution so formed is then stripped forming an aqueous solution containing the Group Vill metal. The most prevalent Group VIII metals in the pregnant liquor of spent hydrodesulfurization or hydrodemetalation catalysts are nickel and cobalt.

Nickel is extracted with an organic nickel extractant. Preferred organic extractants include oximes. The hydroxy oxime component has the general formula:

where R, R' and R" may be a variety of organic hydrocarbon radicals such as aliphatic and alkyaryl radicals.

R" may also be hydrogen. Preferably, R and R' are unsaturated hydrocarbons or branched chain alkyl groups containing from 6 to 20 carbon atoms. R and R' are also preferably the same. It is also preferred that R" is hydrogen or unsaturated hydrocarbon or branched chain alkyl groups containing from 6 to 20 carbon atoms.

Suitable oximes are disclosed, for example, in U.S. Patent Nos. 3,224,873, 3,592,775,3,455,680, 3,428,499, 3,276,863 and 3,197,274. Particularly suitable extractants comprise 2-hydroxy-4-nonylbenzophenoxime which is a primary extractant in a composition also containing an alpha-hydroxy oxime sold by Henkel Corporation under the Trade Mark of LIX 64N; 8-diethyl-7-hydroxy-6-dodecanoneoxime, which is the primary extractant in a composition sold by Henkel Corporation under the Trade Mark LIX 63; and 2-hydroxy-4-dodecylbenzophenoxime which is primary extractant in a composition also containing an alpha-hydroxy oxime sold by Henkel Corporation under the Trade Mark LIX 64.

The preferred extracting agent is LIX 64N. This agent contains 46 to 50% betahydroxybenzophenoneoxime and 1 to 2 % of an aliphatic alphahydroxyomixe in a hydrocarbon diluent such as kerosene. This extracting agent provides nearly quantitative extraction of nickel and provides a very high degree of separation for nickel (II) over cobalt (Ill).

Nickel is stripped from the extractant by any conventional stripping solution, for example, sulfuric acid.

Cobalt is extracted next in the serial extractions. The cobalt in the pregnant liquor is in the +3 oxidation state and must be reduced to the +2 oxidation state before it can be easily extracted by conventional cobalt extracting agents. Cobalt (III) is conventionally reduced to cobalt (II) by contacting the cobalt (III) solution with cobalt metal. One form of cobalt metal for this reduction is cobalt shot.

The cobalt (II) is then extracted with an extracting agent containing a metal chelating beta-diketone extractant. A preferred extractant is a beta-diketone of the formula

where n is 1 to 4, m is 1 or 2 and R is an alkyl group of 1 to 25 carbon atoms. The compounds and their preparation are disclosed in U.S. Patent No. 4,152,396. The preferred extractant is sold by Henkel Chemical under the Trade Mark LIX 51. Other organic cobalt (II) extractants include the oximes, dioximes and diketones aforementioned as nickel extractants. If the same extractant is used both for cobalt and nickel, selectivity can be provided by the oxidation state of cobalt.

Suitably, the metal chelating beta-diketone extractant is dissolved in kerosene with about 10-15% of a conditioning agent. Advantageously, the conditioning agent is an alcohol that contains about 10 carbon atoms with decanol being preferred. A preferred hydrocarbon is kerosene. An example of a preferred hydrocarbon is Kermac 470B, which is marketed by Kerr-McGee. The ratio of metal chelating beta-diketone to alcohol to hydrocarbon to be used is governed by considerations such as speed and completeness of phase separations and concentration of cobalt in the liquor to be extracted. When decanol and Kermac 470B are selected for use as the alcohol and the hydrocarbon respectively, the optimum decanol concentration is about 15 volume percent with a concentration range of 10 to 20 volume percent being operative.

The maximum loading capacity of cobalt (II) on the 5 volume percent beta-diketone extractant solution is about 2.6 grams per liter. Beyond this level precipitation occurs in the organic phase. An organic solution containing about 5 volume percent of beta-diketone extractant, is typically sufficient to remove all the cobalt encountered from an ammoniacal leach of spent catalysts. Thus, it is preferred that the organic extractant solution for spent catalysts contains about 5 volume percent beta-diketone and about 15 volume percent decanol and 75 to 85 volume percent Kermac 470B. Suitably the extraction step is carried out at a temperature in the range from room temperature to 400C and is carried out in one stage or two stages of countercurrent extraction. The loading of cobalt (II) on a beta-diketone extraction is strongly pH dependent.

Cobalt (II) begins to load in weakly acidic solutions with the maximum loading taking place between pH 7.5 and 9.5. Thus, pH adjustment by evaporation of ammonia from the leach liquor prior to extraction of nickel values aids cobalt (II) extraction. If necessary, the pH may be further adjusted at this time by addition of sulfuric acid or ammonium hydroxide depending on whether the pH needs to be adjusted upward or downward. It has been found that extractions are favorable in solutions with less than 50 grams per liter of ammonia concentration.

The organic phase containing cobalt may be stripped by several of any alternative methods. One conventional stripping technique frequently used, is stripping the cobalt values with sulfuric acid to produce cobalt sulfate in an aqueous phase. Another stripping method found to work is the use of an ammonia and ammonium salt solution to strip cobalt from the organic phase.

An alternative method is adding other metallic ions, for example, copper (II) or nicke (II), to "crowd" the cobalt from the organic extractantfreeing the cobalt into an aqueous solution.

The aqueous solutions of Group VIII metals produced by this invention can be processed further to produce pure metal or a salt that can be directly reused to form new catalyst. Nickel or cobalt can be electrowon or directly reduced by hydrogen gas. The aqueous solutions of nickel or cobalt can be used directly as a metal source for impregnating or comulling new catalyst.

For a better understanding of the invention, reference will now be made, by way of example, to the accompanying drawings, in which: Figure lisa flow diagram showing the details of the leaching steps of this invention; Figure 2 is a flow diagram showing the total flow scheme of this invention; and Figure 3 is a Raman Spectrum of a novel vanadium bicarbonate complex.

Figure 1 shows in detail the leaching steps of this invention. Spent catalyst is roasted at 4000C to 600"C. The roasted catalyst is then contacted with an aqueous solution containing both ammonia and an ammonium salt. The temperature of this leach is maintained at about 90"C. The first pregnant liquor is further processed, as shown in Figure 1. The once-leached catalyst is contacted with a saturated solution of sulfur dioxide at between 650C to 1 00 C and preferably ' tween 80"C and 1 00 C. The second pregnant liquor is removed from the twice-leached catalysts, which are disposed of. The second pregnant liquor is then contacted with hydrogen sulfide, precipitating metal values from the solution.The metal values precipitated are primarily cobalt and molybdenum. The precipitated sulfides are placed back into the roast to be reroasted and releached with the ammoniacal solution. In this manner, substantially all of the cobalt is recovered and an ammoniacal stream is provided for further processing.

Figure 2 illustrates the total flow scheme of this invention. Metals are recovered from spent catalysts known to contain cobalt, nickel, molybdenum and vanadium. The catalyst is first roasted and leached as described above. The first pregnant liquor is then extracted with a quaternary amine, forming a first set of two streams: an organic stream containing molybdenum and vanadium, and an aqueous stream containing cobalt and nickel. The first organic stream is stripped with an aqueous solution of ammonium bicarbonate.

Hydrochloric acid is added to the aqueous strip solution and ammonium metavanadate is precipitated. The volume of the solution is then reduced and ammonium molybdate is precipitated.

Excess ammonia is removed from the first aqueous stream, by heating the solution. The remaining first pregnant liquor is first exposed to air insuring that cobalt is in the trivalent oxidation state. It is then extracted with LIX 64N, removing the nickel and creating a second set of two streams: an aqueous stream containing cobalt and any impurities, and an organic stream containing nickel. The second organic solution is stripped with sulfuric acid, forming an acidic nickel-containing sulfate solution. The cobalt in the second aqueous stream is reduced over cobalt shot, and extracted with LIX 51, thereby forming a third set of aqueous and organic streams.

The third aqueous stream is recycled to the leach step, enriched in ammonia removed from the ammonia distillation step. The third organic stream is stripped with a solution of ammonia and ammonium carbonate.

By the use of the flow scheme in Figure 1, a process is provided that is entirely compatible with an ammoniacal leach. Therefore, the pregnant liquor from the leach should be in aqueous ammoniacal solution.

Examples The following Examples illustrate the various steps of the process of the invention.

Example I This Example shows the ammoniacal leach step of the present invention.

A spent hydrodesulfurization catalyst containing 1.45 weight percent cobalt and 6.75 weight percent molybdenum was obtained from pilot plant service. The catalyst particles contained, in addition to the catalytic metals 1.62 weight percent nickel and 6.24 weight percent vanadium, as well as 9.86 weight percent carbonaceous deposits and 12.3 weight percent sulfur. vanadium, as well as 9.86 weight percent carbonaceous deposits and 12.3 weight percent sulfur.

The catalyst particles were roasted in a bed about 0.75 inches deep at 310 C for 3 hours, then at 438"C for 3 hours. The temperature never exceeded 450"C. At the end of the roast, the particles had lost 10.2 percent of their original weight. This weight loss was attributed to oxidation, and subsequent loss to the atmosphere of carbon and sulfur.

A leach solution was prepared by dissolving 179 grams (NH4)2CO3 in 1 liter of a 2M aqueous solution of NH40H. Ninety-eight grams of catalyst particles, roasted as above, were placed in a 5-liter flask heated to 85"C. Aliquots were taken every 5 minutes and analyzed by Inductively Coupled Plasma (ICP) to determine metals content.

Table I shows the results.

TABLE I % Metals Extracted Time (minutes) [Co] [Ni] [Mo] [V] [Fe] [P] 5 47 73 86 74 3.6 15 10 47 73 86 76 5.7 17 28 44 85 86 84 4.2 28 The concentrations of nickel, molybdenum and vanadium, in the leach liquor, increases with time, but the concentration of cobalt tends to decrease after about 10 minutes. The leach time can be varied to increase the amount of any metal that is desired. Since phosphorous may interfere with downstream processing of the leach liquor and is not a valuable metal to be recovered, stopping the leach when the solution contains low amounts of phosphorous is preferable.Although this example was leached at 85"C, the spent catalysts could have been leached at any temperature between 75"C and the boiling point of the solution, but preferably between 85"C and 95"C.

Example 2 This Example shows another ammoniacal leach, as effected according to this invention.

Spent hydrodesulfurization catalyst containing 1.4 weight percent cobalt, 6.3 weight percent molybdenum, 2.2 weight percent nickel, and 4.2 weight percent vanadium was roasted for 2 hours at 427"C under a slight flow of air. When substantially all the carbonaceous and sulfurous residue was burned off, the roasting was stopped. When the particles had cooled, they were placed in 1 liter of solution made by dissolving 200 grams of(NH4)2CO3 in 1 liter of 2M aqueous NH40H.

The solution was analyzed for metals after 20 minutes and 180 minutes. The results are shown in Table II.

TABLE II % Metals Extracted Time (minutes) [Co] [Ni] [Mo] [V] 20 48 71 89 68 180 31 83 97 67 It can be seen that with a great increase in the length of time of the leach, more nickel, molybdenum and vanadium were recovered, but the yield of cobalt had significantly fallen.

Example 3 This is another Example of the ammoniacal leach of this invention.

Spent hydroprocessing catalyst particles were roasted at various temperatures and then placed in a solution of 1 M (NH4)2CO3 dissolved in 2M NH40H solution, except the run at 850"C which was placed in 0.5M (NH4)2CO3 in 2M NH40H. Aliquots of solution were removed at 15 minutes and 180 minutes and analyzed by ICP for metals content. The results are tabulated in Table III.

TABLE III Roast Temperature 427"C 600"C 760"C 850"C 15 180 15 180 15 180 15 180 Metal min min min min min min min min % Metals Extracted Co 48 31 46 26 32 34 32 15 Mo 89 97 70 74 81 89 52 62 Ni 71 83 45 46 19 28 8 21 V 68 87 70 73 103 107 80 81 The values given are percent of metals leached into solution compared to the metals content on unleached catalyst.

Nickel recovery suffers as the roast temperature of the spent catalyst particles is increased beyond 600"C.

No metals are significantly better recovered than if the spent catalyst is roasted at 427"C. Cobalt recovery in general is better after 15 minutes at each roast temperature than after 180 minutes at the same roast temperature. It is, in general, best to stop the leach of the present invention after about one hour.

Example 4 This Example shows the SO2 leach of this invention. 30.00 grams of spent catalyst from pilot plant service were leached for 60 minutes in 600 ml of a saturated aqueous solution of SO2. The temperature of the leach was 85"C.

TABLE IV Fe Ni V Al Co Mo Headsppm 6200 7200 21100 353900 14500 13500 Tailsppm 3900 6200 18300 372400 3900 13400 Percentage leached 49.38 30.71 30.21 17.65 78.36 20.13 Analysis of Heads, Tails and final percentage leached is shown in Table IV.

Example 5 This is another Example of the SO2 leach of this invention. 9 grams of spent catalyst from pilot plant service were leached for 180 minutes in 170 ml of a saturated aqueous solution of SO2 at 88"C.

Analysis of the heads, tails and percentage of metals leached is shown in Table V.

TABLE V Fe Ni Vi Co Mo Heads,ppm - 8500 13000 23000 8800 Tails, ppm 1914 3064 7527 2577 7869 Percentage leached - 71.28 53.94 91.09 28.86 Example 6 This Example shows the extent of metals precipitation from the SO2 leach solutions derived in the previous two examples. Metal sulfides were precipitated by bubbling H2S through solutions cooled to room temperature and having a pH between 3.5 and 4.0. The percent metals removed from each SO2 leach liquor is shown in Table VI.

TABLE Vl Solution Co Mo Ni V 1 97.7 > 98.6 > 96.0 92.7 2 97.3 90.1 > 94.9 58.2 Example 7 This Example shows a coextraction of molybdenum and vanadium from a pregnant liquor. The pH of the aqueous solution was varied. It was found that the most efficient extraction was at pH 10.4, which is about as high as practical in an ammoniacal solution. The organic extraction solution was 10% Aliquat 336 in kerosene with 10% decanol added. The aqueous feed solution had 2.4 g/l molybdenum, 3.1 g/l vanadium and a pH of about 10.1. The pH was raised by addition of NH40H and lowered by addition of H2SO4. The aqueous phase and organic phase were contacted at room temperature in a separating funnel. The volume of aqueous solution equaled the volume of organic solution. The results are tabulated in Table VII.

TABLE VII Mo V Contact g/ 91 g/ g/ Time, liter liter D=Orgl liter liter D=Orgl pH 25 (Min) Org Aq Aq Org Aq Aq 10.4 10 1.06 1.28 0.83 2.83 0.43 7.1 10.1 10 0.86 1.62 0.53 2.97 0.40 7.4 9.6 10 0.60 1.88 0.32 3.11 0.43 7.8 10.1 20 0.88 1.63 0.49 3.14 0.41 7.8 Example 8 This Example shows the effect of varying bicarbonate concentrations in ease of stripping metals from a solution of10%Aliquat336in 10%decanol and kerosene loaded with both molybdenum and vanadium.

Aqueous solution having the following concentrations of NH4HCO3 were made: 6.84, 13.68, 20.52, 100.0 and 200.0 grams per liter. An aqueous to organic ratio of 1:1 was used for all concentrations.

The results of the experiments are tabulated in Table VIII.

TABLE VIII INITIAL FINAL [NH4HCO3] Mo* Mo g/l pH org(g/l) org(g/l) aq(g/l) pH 6.84 8.29 3.3 2.9 0.26 8.73 13.68 8.20 3.3 2.5 0.68 8.52 20.52 8.20 3.3 2.1 1.1 8.42 100.0 8.21 3.3 0.4 2.9 8.07 200.0 8.34 4.0 0.3 3.7 8.41 INITIAL FINAL [NH4HCO3] V* V g/l pH org(g/l) org(g/l) aq(g/l) pH 6.84 8.29 6.3 6.132 0.025 8.62 13.68 8.20 6.3 6.140 0.081 8.45 20.52 8.20 6.3 6.010 0.182 8.36 100.0 8.21 5.2 3.476 2.070 8.07 200.0 8.34 5.2 1.247 3.360 8.45 * Analysis for metal concentrations in solution was done by Atomic Absorption.

Example 9 Two organic solutions, one having 3.367 9/l of molybdenum loaded on 10% Aliquat 336 in 10% decanol in kerosene, the other having 6.292 g/l vanadium loaded onto 10% Aliquat 336 in 10% decanol in kerosene, and two aqueous solutions one with 20 g/l N H4HCO3 and the other with 200 9/l NH4HCO3 were made up. A variety af organic to aqueous ratios were chosen and the results tabulated in Tables IX and X.

TABLE IX 20 g/l NH4HCO3 200 9/l NH4HCO3 Ratio pH org(g/l) aq(g/l) pH org(g/l) aq(gIl) 15/1 8.97 3.019 1.389 8.70 2.517 9.412 10/1 8.93 2.994 1.459 8.52 1.562 14.182 5/1 8.87 3.189 1.540 8.35 1.036 11.871 2/1 8.59 2.606 1.318 8.22 0.431 6.096 1/1 8.40 2.217 1.097 8.09 0.248 3.315 1/2 8.19 .570 0.808 8.02 0.151 1.743 1/5 8.19 1.182 0.428 8.03 0.100 0.705 1/10 8.19 0.660 0.266 8.00 0.119 0.350 1/15 8.17 0.635 0.179 8.00 0.127 0.234 Table IX shows the data for stripping the Mo solution.

TABLE X 20 g/l NH4HCO3 200 g/l NH4HCO3 Ratio pH org(g/l) aq(g/l) pH org(g/l) aq(g/l) 15/1 9.03 6.412 0.162 8.52 5.228 * 1011 8.97 6.306 0.175 8.35 5.326 * 5/1 8.6 6.144 0.179 8.32 3.850 * 2/1 8.44 6.080 0.177 - 2.310 * 1/1 8.53 6.104 0.178 8.10 0.743 5.700 1/2 8.25 5.715 0.151 8.03 0.251 1/5 8.17 5.690 0.137 8.00 0.186 1.112 1/10 8.17 5.131 0.112 8.02 0.352 0.800 1/15 8.20 5.050 0.100 7.99 0.277 0.385 * Precipitate Present Table X shows the data for stripping V from the organic. One unusual feature of the 200 g/l NH4HCO3 strip noted is a greenish color not in the pregnant aqueous solution present in the 20 g/l NH4HCO3 solution.It is suspected that this may indicate the formation of a previously unreported vanadium species.

Example 10 The greenish solution of Example 8 was analyzed by Raman spectroscopy.

TABLE XI Transition Energy (cm-1) Intensity Assignment 1063 M CO32 1019 VS HCO32 917 VS VanadiumVcarbonatocomplex 888 sharp ? 674 W CO32 633 w HCO3- 438 M Vanadium V carbonato complex 347 w Vanadium V carbonato complex Raman spectroscopy provides strong evidence for a vanadium V carbonato complexes. Table XI shows the Raman bands of some vanadium containing solutions and their assignment. All solutions were adjusted to pH 8.8 using either nitric acid or sodium hydroxide. Sodium bicarbonate solutions containing vanadium show an intense Raman band at 923 cm-l and a moderate bands at 435 cm-' and 354 cm-' as shown in Figures 3B and D.Neither vanadium-free sodium bicarbonate, Figure 3C, nor bicarbonate-free metavanadate solution, Figure 3A, showed these bands. In addition, we have noted that vanadium bicarbonate solutions usually have a characteristic light green color which we suspect is due to the complex.

Example 11 This example shows the results of costripping both Mo and V from loaded organic solvents with 200 g/l NH4HCO3 solution. An organic solution was prepared that had 3 g/l molybdenum and 6 g/l vanadium dissolved in a kerosene solution containing 10% Aliquat 336 and 10% decanol. Various organic to aqeuous ratios were tried. The data is tabulateu In Table XII.

TABLE XII Ratio pH org(g/l) aq(g/l) org(g/l) aq(g/l) 15/1 8.49 0.168 * 5.175 * 10/1 8.51 0.077 * 4.226 * 5/1 8.52 0.104 * 4.664 * 2/1 8.29 0.051 * 2.166 * 1/1 8.16 0.030 * 0.750 * 1/2 8.01 0.015 0.083 0.321 3.048 1/5 8.03 0.008 0.034 0.234 1.305 1/10 8.00 0.007 0.016 0.211 0.603 1/15 8.00 0.012 0.011 0.349 0.393 * an insoluble pptformed Example 12 This example illustrates the production of a cobalt (II) solution from an aqueous solution initially containing both nickel and cobalt.

Spent catalyst particles, from service in a hydrodesulfurization pilot plant, containing cobalt and molybdenum, as catalytic metals, were in contact with a feedstock containing high levels of vanadium and nickel, as contaminant metals. The catalyst particles were leached with aqueous ammonium carbonate/ ammonia solution at a pH of about 10.5. After heating the solution to evaporate enough ammonia so that ammonia plus ammonium equals about 25 grams per liter at a pH of 9, nickel was extracted by LIX 64N in kerosene. The solution was then passed through a column of cobalt shot and the raffinate from this column containing 2.975 grams per liter of cobalt is extracted with 5 percent by volume LIX 51 in 10 percent decanol and 85 percent Kermac 470B at 500C.The resulting organic solution was stripped with 2 molar ammonium carbonate solution in 15 molar ammonia solution that had its pH adjusted to 10.27 by addition of sulfuric acid. About 25 percent of the cobalt from the LIX 51 was removed during each contact with the ammonia strip. After several counter current extractions, the resulting cobalt (II) carbonate solution was evaporated to produce a cobalt containing brown powder, which is believed to be a mixed oxide, carbonate salt.

The cobalt (II) carbonate solution can be directly recycled to catalyst manufacture or can be processed to produce a cobalt product.

Example 13 Various organic solutions containing cobalt in LIX 51 solution were stripped with aqueous solutions of ammonia and ammonium carbonate. The organic solutions were 5% LIX 51 85% Kermac 470B and 10% decanol. The concentration of cobalt in the organic phase was 2.65 g/l in the 3M and 5M ammonia cases and 3.1 g/l in the 15M ammonia case. The volume ratio of organic (O)/aqueous (A) was varied. The results are tabulated in Table XIII.

TABLE XIII Cobalt stripping with ammonia solution organic phase: 5% LIX 51, 85% Kermac 470B and 10% decanol temperature 50"C organic concentrationlaqueous concentrate (g Co/llter) Stripping Solutions NH3M 15 5 5 3 (NH4)2CO3M 2 2.5 2.5 1.5 Kjeldahl NH3 206 (s/l) pHRT 10.27 10.58 10.4 10.27 Volume Phase Ratio (O/A) 15/1 2.72/0.42 10/1 2.69/0.31 2.98/1.21 3.0/1.05 3.08/0.23 5/1 2.45/0.51 2.94/0.82 2.98/0.81 3.04/0.31 2/1 2.28/0.53 2.83/0.52 2.86/0.47 3.02/0.16 1/1 2.00/0.97 2.84/6.32 2.82/0.28 3.01/0.12 1/2 1.74/0.30 2.67/0.21 2.77/0.17 2.86/0.081 1/5 1.49/0.23 2.45/0.12 2.52/0.094 2.88/0.045 1/10 1.32/0.15 2.34/-0.077 2.97/0.015 2.82/0.028 1/15 1.05/0.22 2.06/0.06 2.61/0.03 2.73/0.025 The data indicate that the cobalt goes into the aqueous phase from the organic phase more readily for the 15M ammonia case than for either the 5M or 3M cases. Therefore, at greater ammonia concentrations more cobalt is stripped if the pH is held at about 10.5.

Claims (15)

1. A process for recovering the metal values from spent hydroprocessing catalyst particles, said values including at least one first metal from Group VIII of the Periodic Table and at least one second metal from Group Vb or Group Vlb of the Periodic Table, said process comprising: (a) roasting the particles in an atmosphere containing molecular oxygen at a temperature in the range from 400"C to 600 ; (b) leaching the particles with a first aqueous solution containing ammonia and an ammonium salt at a temperature less than the atmospheric boiling point of said first aqueous solution, thereby forming a first pregnant liquor and once-leached particles; (c) separating the once-leached particles from the first pregnant liquor;; (d) leaching the once-leached particles with a second aqueous solution containing sulfur dioxide, thereby forming a second pregnant liquor and twice-leached particles; (e) separating the second pregnant liquor from the twice-leached particles; (f) precipitating metal sulfides from the second pregnant liquor by the addition of hydrogen sulfide; (g) roasting said precipitated metal sulfides with fresh spent catalyst in step (a); (h) transferring the metal values contained in the first pregnant liquor of said second metal into a first organic solution by liquid ion exchange; (i) stripping said metal values from said first organic solution with a first aqueous strip solution; (j) separating said metal values by sequential precipitation;; (k) selectively transferring the metal values of said first metal from said first pregnant liquor into at least one second organic solution by serial liquid ion exchange; and (I) stripping each of said second organic solutions to form single metal containing aqueous solutions.

2. A process according to Claim 1, wherein said spent hydroprocessing catalysts are supported on alumina.

3. A process according to Claim 1 or 2, wherein said first aqueous solution has a pH maintained in the range from 9.5 to 11 and concentrations of ammonia plus ammonium not exceeding 6 molar.

4. A process according to Claim 1, 2 or 3, wherein the pH of said second aqueous solution is maintained in the range from 2.5 to 3.

5. A process according to Claim 1,2,3 or 4, wherein said first aqueous strip solution includes bicarbonate ion.

6. A process according to Claim 1,2,3 or 4, wherein said Group Vb metal is vanadium, said first aqueous strip solution contains bicarbonate and a greenish solution is produced in step (i) having the Raman spectrum of Figure SB.

7. A process according to any preceding claim, wherein said metal values of the second metal include oxyanions of molybdenum, tungsten and/or vanadium.

8. A process according to any preceding claim, wherein said liquid ion exchange in step (h) is effected with a quaternary alkyl ammonium salt as the phase transfer reagent.

9. A process according to any preceding claim, wherein said metal values of said first metal include nickel and cobalt.

10. A process according to Claim 9, wherein the nickel is in the divalent state and the cobalt is in the trivalent state.

11. A process according to Claim 10, wherein in step (h) the nickel is transferred with an extractant selected from dioximes and hydroxy-oximes.

12. A process according to Claim 11, wherein said trivalent cobalt is reduced to divalent cobalt, which is extracted with an extractant selected from dioximes, hydroxy-oximes and beta diketones.

13. A process according to any preceding claim, wherein step (t) is effected with a plurality of stripping solutions which include ammonium ion and ammonia.

14. A process for recovering the metal values from spent hydroprocessing catalyst particles, substantially as hereinbefore described with reference to the accompanying drawings.

15. A process for recovering the metal values from spent hydroprocessing catalyst particles containing one or more Group VIII metals including cobalt and at least one Group Vb or Vlb metal, said particles being substantially free from carbonaceous deposits and sulfur, which comprises: (1) leaching the spent catalyst particles with a first aqueous leach solution containing ammonia and an ammonium salt; and (2) subsequently leaching the resulting leached particles with a second aqueous leach solution containing sulfur dioxide.