JPH108157A - Leaching method of vanadium contained in spent catalyst - Google Patents

Abstract

PROBLEM TO BE SOLVED: To selectively leaching vanadium from a used catalyst having a vanadium content of 10% by weight or less such as a sulfuric acid conversion catalyst for inorganic chemistry or an exhaust gas denitration catalyst without high-temperature treatment. Provide a method of recovery. SOLUTION: A used catalyst containing vanadium is brought into contact with sulfuric acid in the presence of metallic aluminum to leaching vanadium.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for leaching and recovering vanadium from a spent catalyst containing vanadium, such as a sulfuric acid conversion catalyst for inorganic chemistry and an exhaust gas denitration catalyst.

[0002]

2. Description of the Related Art Spent catalysts to be recovered from vanadium contained as valuable resources are generally 10% vanadium.
And a desulfurization catalyst containing not less than wt. 10 vanadium
Conventionally, as a method of leaching vanadium from a used desulfurization catalyst containing not less than% by weight, (1) a method of adding sodium sulfate or sodium carbonate, oxidizing and roasting (alkali roasting), and then leaching with water or a diluted caustic soda solution. (JP-A-50-11995, JP-A-54-1074)
No. 95, JP-A-54-61017, Prepr. Am. Chem. So
c., Div. Pet. Chem., 27 [3] (1982) p. 67
4-678). This method is the most common, and converts vanadium into a water-soluble soda salt by oxidizing and roasting by adding a soda salt, and a leaching rate close to 100% by weight can be obtained.

In addition, (2) vanadium is oxidized and roasted according to the same principle as (1) and then leached with a caustic soda solution (JP-A-48-86703). There is a method of leaching as vanadium chloride (JP-A-54-110196).

[0004]

However, the above-mentioned vanadium leaching method is applied to spent catalysts having a vanadium content of at most several weight%, such as sulfuric acid conversion catalysts for inorganic chemistry and exhaust gas denitration catalysts, for economic reasons. It has not been. This is due to the fact that the current vanadium recovery technology from spent catalysts is not suitable for treating spent catalysts other than desulfurization catalysts. Specifically, it is as follows. That is, in the most common alkaline roasting method of the above (1), a high temperature treatment of about 900 ° C. is necessary even if (a) a component such as an oil which needs to be removed by burning hardly adheres to the object to be treated. In addition, (b) the majority of silica as a main component and a part of titania are simultaneously leached (in other words, non-selectively leached), which complicates the post-process, so that economic efficiency is reduced. Have been lost.

In the leaching method using a caustic soda solution of the above (2), silica as a main component is leached at the same time in the chlorination treatment of the above (3), and most of the silica and titania as a main component are leached simultaneously (in other words, , Non-selective leaching), (a) an increase in the cost of the treatment chemicals, and (b) an increase in the complexity of the post-process, so that the above (2) and (3) are economical methods. is not.

SUMMARY OF THE INVENTION In view of the above problems, the present invention selectively uses vanadium from a used catalyst having a vanadium content of 10% by weight or less, such as a sulfuric acid conversion catalyst for inorganic chemistry or an exhaust gas denitration catalyst, without high-temperature treatment. It is an object of the present invention to provide a method for leaching and recovering garbage.

[0007]

SUMMARY OF THE INVENTION In order to achieve the above-mentioned object, the gist of the present invention is to contact a sulfur-containing catalyst containing vanadium with sulfuric acid in the presence of metallic aluminum to leach vanadium.

[0008] When the used catalyst containing vanadium contains an oil, a pretreatment for removing the oil is 300.
After oxidizing and roasting at a temperature of at least ℃ and preferably below 690 ° C, the resulting oxidized and roasted catalyst is contacted with sulfuric acid in the presence of metallic aluminum as described above.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION

[Spent catalyst] The used catalyst to be used in the method for leaching vanadium contained in the used catalyst of the present invention includes:
The main components are silica, titania and the like.

[Pretreatment] The used catalyst usually does not contain a large amount of oil. However, when oil is contained for some reason, it is necessary to remove or mineralize the oil as a pretreatment. This is because if leaching is performed with sulfuric acid without removing or mineralizing the oil, the leaching solution and the oil are mixed and emulsified, and subsequent handling becomes difficult. The removal and mineralization of the oil can be achieved by oxidizing roasting, washing with an organic solvent, or the like. Oxidation roasting is performed for burning or carbonization of the adhered oil. The oxidation roasting temperature is 3
If the temperature is higher than 00 ° C., combustion proceeds relatively efficiently, and the higher the temperature, the better the combustion efficiency. Although there is no particular upper limit for the oxidizing roasting temperature, it is preferable to perform the oxidizing roasting at a temperature lower than the melting temperature of vanadium pentoxide, 690 ° C., from the viewpoint of preventing the catalyst from adhering to the inside of the furnace.

[Leaching] The used catalyst (the catalyst after pretreatment in the case of performing the above pretreatment) is brought into contact with sulfuric acid in the presence of aluminum metal to leach out the contained vanadium. Vanadium is generally contained in the spent catalyst as a pentavalent oxide, but pentavalent vanadium is reduced to tetravalent by a reducing power when metal aluminum is dissolved.
When vanadium becomes tetravalent, its solubility in sulfuric acid increases.

The main reaction for leaching vanadium is presumed to be according to the following reaction formula (I). V ₂ O ₅ + 2Al + 5H ₂ SO ₄ = 2VOSO ₄ + Al ₂ (SO ₄ ) ₃ + 2H ₂ + 3H ₂ O (I)

(1) Sulfuric acid The amount of sulfuric acid is at least one time the stoichiometric amount required for converting vanadium to vanadylic acid sulfate in the above reaction formula (I).
That is, it is sufficient that the amount is at least 4.8 times the weight of the vanadium element contained in the used catalyst. However, if the amount of sulfuric acid is too large, not only does the vanadium leaching rate not be further improved, but also the economy of the present invention becomes negative. In addition, when iron is contained in the spent catalyst, it is desirable that the amount of sulfuric acid necessary to convert iron into sulfate is added to iron because vanadium is leached at the same time as vanadium.

(2) The use of metal aluminum as the reducing agent is such that the dissolution rate of metal aluminum is moderately low and the consumption of metal aluminum is reduced by the stoichiometric amount required in the above reaction formula (I). This is because the leaching reaction proceeds at about 1 to 2 times, that is, about 0.5 to 1 times the weight of the vanadium element contained in the used catalyst, so that it has been found that the efficiency is extremely high.
If the amount of metallic aluminum is increased unnecessarily, the consumption of metallic aluminum tends to increase, and wasteful sulfuric acid is consumed. Preferably, the amount is less than or equal to 100 grams per liter of leachate. As described above, the subject of the method of the present invention is a used catalyst, but the method of the present invention can also be applied to a combustion boiler dust ash of a thermal power plant.

[0015]

EXAMPLES The present invention will be described more specifically based on the following examples. [Example 1] (1) Oxidation roasting A used exhaust gas denitration catalyst containing 4% by weight of an oil component and 6% by weight of vanadium and mainly containing titania was continuously fed to a rotary kiln at a rate of 1 kg / hour. Oxidation roasting was carried out at a temperature of 500 ° C. under such conditions that the residence time in the furnace was 1 hour. As a result, the oil content was reduced to a negligible level.

(2) Vanadium Leaching 100 g of the oxidized roasted sample obtained in the above (1) and 5 g of metal aluminum cut into strips were put into a 2-liter separable flask equipped with a condenser.
One liter by weight of sulfuric acid was added. The stoichiometric amount required to convert 6.25 g of the vanadium element contained in 100 g of the oxidized roasted sample into vanadyl sulfate was 30.0 g of sulfuric acid (a concentration of 2.9% by weight of sulfuric acid). 1
Liters) and 3.3 grams of metallic aluminum.

Next, the separable flask was immersed in a thermostat heated to 90 ° C. to perform heat leaching. The vanadium concentration in the leaching solution was measured every predetermined time until 3 hours had elapsed since the start of the reaction, and the state of leaching of the vanadium was confirmed. During this time, the dissolved amount of the main component titania was negligible, and it was found that vanadium was leached very selectively. The standard oxidation-reduction potential of the leaching solution was about 1000 mV in the initial stage of leaching, but dropped to about 300 mV after 60 minutes from the start of the reaction, whereby the color of the leaching solution changed from yellow to blue. This blue color is the color of tetravalent vanadium ions.

Further, three hours after the start of the reaction, the vanadium leaching rate, the pH of the leaching solution and the amount of dissolved aluminum were measured. The amount of dissolved aluminum was measured by measuring the amount of undissolved metallic aluminum after the completion of the reaction.

Table 1 shows the obtained vanadium leaching rate and the pH of the leaching solution. The amount of dissolved aluminum is
It was about the same as the stoichiometric amount (3.3 grams) of aluminum required to reduce pentavalent vanadium to tetravalent.

Embodiments 2 to 4 500 in Embodiment 1
100 g of an oxidized roasted sample at 5 ° C. and 5 g of stripped metal aluminum were placed in a 2 liter separable flask with a condenser, and 1 liter of 10%, 5% and 2.5% by weight sulfuric acid was placed. (Examples 2, 3, and 4 respectively). Thereafter, a heat leaching test was performed in the same manner as in Example 1.

As a result, the following was obtained in each of the examples. That is, it was found that the dissolved amount of titania, which is a main component, was negligible until 3 hours from the start of the reaction, and that vanadium was extremely selectively leached. The standard oxidation-reduction potential of the leachate was about 1000 mV in the initial stage of leaching, but dropped to about 300 mV after 60 minutes from the start of the reaction, whereby the color of the leachate changed from yellow to tetravalent vanadium ion. Has changed to blue.

Table 1 shows the vanadium leaching rate and the pH of the leaching solution 3 hours after the start of the reaction. The amount of aluminum dissolved is determined by the stoichiometric amount of aluminum necessary to reduce pentavalent vanadium to tetravalent (3.
3 grams).

In Example 4, the amount of sulfuric acid used was stoichiometric (30.0%) necessary to convert vanadium to sulfate.
G), the vanadium leaching rate is less than
It was lower than 3.

[0024]

[Table 1]

Reference Examples 1 and 2
The oxidative roasting was performed in the same manner as in Example 1 except that the temperature was set to 700 ° C. and 700 ° C. (Reference Examples 1 and 2 respectively). As a result, the oil content was reduced to a negligible level at any oxidation roasting temperature. At the time of roasting at 700 ° C., adhesion of the sample to the furnace due to partial melting was observed.

Example 5 contains 3% by weight of vanadium,
200 g of a sulfuric acid conversion catalyst used for inorganic chemistry, containing no oil and containing silica as a main component, and 12 g of metal aluminum cut into strips were placed in a 2-liter separable flask with a condenser, and 50% by weight of sulfuric acid was added. 5
60 milliliters were added. The stoichiometric amount required for converting 6 g of the vanadium element contained in 200 g of this used sulfuric acid conversion catalyst for inorganic chemistry to vanadylic acid sulfate is 28.8 g of sulfuric acid (concentration: 2.8% by weight). 1 liter) and 3.2 grams of metallic aluminum.

Next, the separable flask was immersed in a thermostat heated to 90 ° C. to perform heat leaching. The concentration of vanadium in the liquid was measured at predetermined time intervals until 3 hours had elapsed from the start of the reaction, and the state of leaching of vanadium was confirmed.

As a result, after 30 minutes from the start of the reaction, 95% by weight or more of the vanadium was leached out, and the amount of dissolved silica as the main component was less than 1 gram. It was found to be leached. The standard oxidation-reduction potential of the leaching solution was about 1000 mV at the beginning of leaching, but was about 30 mV after 60 minutes.
0 mV, and the color of the leachate changed from yellow to 4 mV.
The color changed to blue, which is the color of the vanadium ion.

Further, the amount of aluminum dissolved during the leaching of vanadium was determined from the amount of undissolved metallic aluminum after the reaction, and the stoichiometric amount of aluminum required to reduce pentavalent vanadium to tetravalent ( 3.2 grams).

[Comparative Examples 1 to 4] Vanadium leaching was performed according to the method described in Examples 1 to 4 except that no metallic aluminum was added during the leaching of vanadium (Comparative Examples 1 to 4, respectively).

Table 2 shows the vanadium leaching rate 3 hours after the start of the reaction.

[0032]

[Table 2]

From Tables 1 and 2, it can be seen that the vanadium leaching rate is greatly increased when metallic aluminum is added during vanadium leaching as compared to the case where metallic aluminum is not added.

[0034]

According to the method of the present invention, from a spent catalyst containing vanadium, (1) the high temperature treatment of the spent catalyst is not required, and (2) the treatment chemical cost is greatly reduced, and 3) Vanadium can be leached very selectively and with a good leaching rate. Moreover, the obtained leachate can be simply treated in a subsequent step.

Continued on the front page (72) Inventor Toru Kitazaki 2600 Ishigami Gajuku, Tokai-mura, Naka-gun, Ibaraki Prefecture Sumitomo Metal Mining Co., Ltd., Technology Center, Energy & Environment Division (72) Inventor Tadashi Masuko 2600 Ishigami Gajuku, Tokai-mura, Naka-gun, Ibaraki Sumitomo Metal Mining Co., Ltd. Energy & Environment Division Technology Center

Claims (6)

[Claims] 1. A method for leaching vanadium contained in a spent catalyst, comprising contacting a spent catalyst containing vanadium with sulfuric acid in the presence of metallic aluminum. 2. After removing the oil contained in the spent catalyst containing vanadium by oxidizing and roasting at a temperature of 300 ° C. or more, the obtained oxidized and roasted catalyst is contacted with sulfuric acid in the presence of metallic aluminum. A method for leaching vanadium contained in a spent catalyst. 3. The method for leaching vanadium contained in a spent catalyst according to claim 2, wherein the oxidative roasting is performed at a temperature lower than 690 ° C. 4. The method for leaching vanadium contained in a spent catalyst according to claim 1, wherein the main component of the spent catalyst is silica or titania. 5. The use amount of sulfuric acid is 4.8 times or more of the weight of vanadium element contained in the spent catalyst.
4. A method for leaching vanadium contained in a spent catalyst according to any one of the above items 4. 6. The use according to any one of claims 1 to 5, wherein the amount of the metallic aluminum is at least 0.5 times the weight of the elemental vanadium contained in the spent catalyst and at most 100 grams per liter of leachate. Of vanadium contained in spent catalyst.