Method for preparing vanadium leachate using spent vanadium catalyst for sulfuric acid production, and vanadium recovery method using same

Abstract

A method for preparing a vanadium leachate according to one embodiment of the present invention comprises the steps of: forming a mixture by mixing a spent vanadium catalyst for sulfuric acid production with a vanadium leaching enhancer; roasting the mixture to form a roasted product; and leaching vanadium to form a vanadium leachate by immersing the roasted product in water as a solvent.

Description

Method for preparing a vanadium leaching solution using a used vanadium catalyst for sulfuric acid production and a method for recovering vanadium using the same

[0001] The present invention relates to a technology for recovering vanadium from a vanadium catalyst for sulfuric acid production that has been used up, and more specifically, to a method for preparing a vanadium leaching solution using a vanadium catalyst for sulfuric acid production that has been used up and a method for recovering vanadium using the same.

[0002] Sulfuric acid production catalysts primarily use vanadium (V2O5) as the active ingredient and play an important role in the process of oxidizing sulfur dioxide (SO2) gas into sulfur trioxide (SO3). Although sulfuric acid production catalysts can be regenerated and reused, they are eventually disposed of when they reach the end of their lifespan or when damage or wear occurs during the process. In this case, recovering the vanadium contained in the catalyst becomes a very important task when considering economic value and environmental benefits.

[0003] Vanadium possesses high tensile strength, hardness, and fatigue resistance, and thanks to these properties, it plays a very important role as a raw material for alloys of iron or non-ferrous metals. In fact, more than 85% of the world's vanadium production is used as a raw material for metal alloys. Since the vanadium used in catalysts for sulfuric acid production contains a significant amount, it is necessary to efficiently recover and reuse it rather than disposing of it after use.

[0004] Water leaching can be used to recover vanadium from used sulfuric acid production catalysts, but this method has several problems.

[0005] Vanadium compounds (VO xVanadium is formed as a very thin layer on the SiO2 support constituting the catalyst for sulfuric acid production and is not easily leached out due to its characteristics of existing within the pores. In particular, since the SiO2 support has high structural stability, additional treatment such as leaching at high temperatures or micronization is required to increase the leaching rate of vanadium.

[0006] Furthermore, since the catalyst was used in the production of sulfuric acid, when an aqueous leaching process is performed to leach vanadium, the leachate becomes acidic, and at this time, the vanadium forms the so-called red cake (Na2H2V6O). 17 The problem arises that the leaching rate decreases as it precipitates in the form of ). To prevent this, a large amount of acid must be used, which increases costs and environmental burdens.

[0007] Ultimately, in order to fully recover vanadium from used sulfuric acid production catalysts, a new method to solve these problems is required.

[0008] One objective of the present invention is to provide a method for leaching vanadium compounds dispersed on an SiO2 support of a used vanadium catalyst for sulfuric acid production to a higher concentration.

[0009] Another objective of the present invention is to provide a method for recovering vanadium as a vanadium salt or vanadium pentoxide from a used vanadium catalyst for sulfuric acid production.

[0010] Meanwhile, other unspecified objectives of the present invention will be further considered to the extent that they can be easily inferred from the following detailed description and effects.

[0011] To achieve the objectives proposed above, the following solutions are proposed.

[0012] A method for preparing a vanadium leaching solution according to one embodiment of the present invention is characterized by comprising the steps of: mixing a used vanadium catalyst for sulfuric acid production with a vanadium leaching promoter to form a mixture; roasting the mixture to form a roasted product; and immersing the roasted product in water as a solvent to leach vanadium and form a vanadium leaching solution.

[0013] In one embodiment, the vanadium catalyst for sulfuric acid production that has been used may be one in which vanadium pentoxide is supported on an SiO2 support.

[0014] In one embodiment, the vanadium leaching promoter may be at least one selected from the group consisting of Na2CO3 and K2CO3.

[0015] In one embodiment, when the vanadium leaching promoter is Na2CO3, the vanadium contained in the used vanadium catalyst for sulfuric acid production reacts with the vanadium leaching promoter to form NaVO3, and the SiO2 support reacts with the vanadium leaching promoter to form Na2SiO, and when the vanadium leaching promoter is K2CO3, the vanadium contained in the used vanadium catalyst for sulfuric acid production reacts with the vanadium leaching promoter to form KVO3, and the SiO2 support reacts with the vanadium leaching promoter to form K2SiO3.

[0016] In one embodiment, the roasting can be performed at a temperature of 851°C or higher.

[0017] In one embodiment, the content of the vanadium leaching promoter may be 100 to 200 parts by weight per 100 parts by weight of the used vanadium catalyst for sulfuric acid production.

[0018] In one embodiment, in the step of forming the vanadium leaching solution, the solid-liquid ratio (S) of the roasted material and the water wt / L vol) can be 0.2 to 0.5.

[0019] A vanadium recovery method according to one embodiment of the present invention comprises (a) a step of preparing a vanadium leaching solution from a vanadium catalyst for sulfuric acid production that has been used up, and (b) a step of preparing a vanadium salt crystal or vanadium pentoxide from the vanadium leaching solution, wherein step (a) comprises a step of mixing a vanadium catalyst for sulfuric acid production that has been used up and a vanadium leaching promoter to form a mixture, a step of roasting the mixture to form a roasted product, and a step of immersing the roasted product in water as a solvent to leach vanadium and form a vanadium leaching solution.

[0020] A method for preparing a vanadium leaching solution using a used vanadium catalyst for sulfuric acid production according to the present invention and a method for recovering vanadium using the same provide the following effects.

[0021] First, the present invention converts a used vanadium catalyst for sulfuric acid production into a composite that facilitates vanadium leaching by mixing it with a vanadium leaching promoter and then roasting it. Furthermore, through this process, the structural stability of the SiO2 support is weakened and partially dissolved to expose the vanadium in the pores or on the surface, thereby achieving a very high vanadium leaching rate of over 99%.

[0022] Second, the present invention solves the problem of red cake (NaVOx) precipitation occurring in conventional water leaching methods, thereby avoiding the use of large amounts of acid and providing environmental and economic advantages.

[0023] Third, the present invention can achieve high leaching efficiency even under relatively mild conditions, thereby improving the economic efficiency of the vanadium recovery process.

[0024] Fourth, in the present invention, the vanadium concentration increases proportionally with increasing solid-liquid ratio, and the higher the concentration of vanadium in the leaching solution, the higher the recovery rate in the subsequent processes of vanadium salt crystallization or vanadium pentoxide precipitation.

[0025] Meanwhile, it should be added that even if an effect is not explicitly mentioned here, the effects described in the following specification and the provisional effects expected by the technical features of the present invention are treated as described in the specification of the present invention.

[0026] FIG. 1 is a schematic flowchart of a method for preparing a vanadium leaching solution using a vanadium catalyst for sulfuric acid production that has been used up, and a method for recovering vanadium using the same, according to one embodiment of the present invention.

[0027] Figure 2 is a reference diagram to explain the changes before and after the process of mixing and roasting a used vanadium catalyst for sulfuric acid production and a vanadium leaching promoter.

[0028] It should be noted that the attached drawings are provided as examples for reference to help understand the technical concept of the present invention, and the scope of the rights of the present invention is not limited by them.

[0029] Hereinafter, with reference to the drawings, we will examine the configuration of the present invention as guided by various embodiments thereof and the effects derived therefrom. In describing the present invention, detailed descriptions of related known functions are omitted if they are deemed obvious to a person skilled in the art and could unnecessarily obscure the essence of the invention.

[0030] Used vanadium catalysts for sulfuric acid production are catalysts that play an important role in the sulfuric acid production process. These catalysts are used to promote the chemical reaction that oxidizes sulfur dioxide (SO2) gas to sulfur trioxide (SO3), and generally contain vanadium oxide (V2O5) as an active component. To increase reactivity, the catalyst takes the form of a very thin layer of vanadium oxide supported on a silica (SiO2) support.

[0031] The chemical structure of used vanadium catalysts for sulfuric acid production consists of a thin, two-dimensional layer of vanadium oxide (VOx) formed on a silica (SiO2) support. Additionally, vanadium is present within the fine pores of the silica; however, due to this pore structure and the high structural stability of the silica support, leaching out vanadium is not easy. Generally, when attempting to recover vanadium using the water leaching method, the chemical stability of the silica contained in the catalyst can block solvent diffusion during the process, thereby reducing the leaching rate. Furthermore, because the catalyst was exposed to acidic substances during the sulfuric acid production process, the leaching solution becomes acidic during the water leaching process; this leads to the formation of red cake (Na2H2V6O2) from the vanadium. 17 A problem arises where the leaching rate decreases due to precipitation in the form of ). To solve this problem, a large amount of additional acid must be used, but this increases the economic burden and has a negative impact on the environment.

[0032] Below, we propose a new method to recover vanadium from a vanadium catalyst for sulfuric acid production that has been used without these problems.

[0033] FIG. 1 is a schematic flowchart of a method for preparing a vanadium leaching solution using a vanadium catalyst for sulfuric acid production that has been used up, and a method for recovering vanadium using the same, according to one embodiment of the present invention.

[0034] A vanadium recovery method according to one embodiment of the present invention includes the steps of preparing a vanadium leaching solution from a vanadium catalyst for sulfuric acid production that has been used up, and preparing a vanadium salt crystal or vanadium pentoxide from the vanadium leaching solution.

[0035] I will start by explaining the step of preparing a vanadium leaching solution from a vanadium catalyst for sulfuric acid production that has been used.

[0036] First, the vanadium catalyst used for sulfuric acid production is crushed to form a crushed material. At this time, it is not necessary to finely pulverize the material to the level of several to tens of micrometers; crushing it to the level of several hundred micrometers is sufficient.

[0037] Next, a step is performed to form a mixture by mixing the ground material and a vanadium leaching promoter. As the vanadium leaching promoter, at least one selected from the group consisting of Na2CO3 and K2CO3 may be used. The content of the vanadium leaching promoter may be 100 to 200 parts by weight per 100 parts by weight of the vanadium catalyst for sulfuric acid production that has been used.

[0038] After forming the mixture, a step of roasting the mixture is performed. Roasting can be performed at a temperature of 851 °C or higher. More specifically, if the vanadium leaching promoter is Na2CO3, it can be performed at a temperature of 851 °C or higher, which is the melting point of Na2CO3, and if the vanadium leaching promoter is K2CO3, it can be performed at a temperature of 891 °C or higher, which is the melting point of K2CO3.

[0039] During the roasting process, vanadium and a vanadium leaching promoter, and a SiO2 support and a vanadium leaching promoter react as shown in the following equations. Equation 1 is the case where the vanadium leaching promoter is Na2CO3, and Equation 2 is the case where the vanadium leaching promoter is K2CO3.

[0040]

[0041] [Reaction Equation 1]

[0042] V2O5(s) + Na2CO3(s, l) → 2 NaVO3(s, l) + CO2(g)

[0043] SiO2(s) + Na2CO3(s, l) → Na2SiO3(s, l) + CO2(g)

[0044]

[0045] [Reaction Equation 2]

[0046] V2O5(s) + K2CO3(s, l) → 2 KVO3(s, l) + CO2(g)

[0047] SiO2(s) + K2CO3(s, l) → K2SiO3(s, l) + CO2(g)

[0048]

[0049] Figure 2 is a reference diagram to explain the changes before and after the process of mixing and roasting a used vanadium catalyst for sulfuric acid production and a vanadium leaching promoter.

[0050] First, the left side of Fig. 2 illustrates the structure of a used vanadium catalyst for sulfuric acid production prior to roasting. The spherical particles represent a silica (SiO2) support, on which a thin layer of vanadium oxide (VOx) is formed. The vanadium oxide layer exists in two forms: one is a VOx layer located on the surface of the support, and the other is a VOx layer existing within the pores of the silica support. Because this VOx layer is very thin and distributed even within the pores of the support, it has a structure that makes leaching difficult. The silica support serves to immobilize the vanadium oxide and possesses a very chemically stable structure. The diameter of a single support particle is approximately 2 to 100 μm, and the pore size is about 20 to 200 Å. Since the silica support is chemically very stable, the vanadium located within the pores is even more difficult to leach out.

[0051] The right side of Fig. 2 shows the changes in the catalyst after roasting, intended to explain the changes that occur when a used vanadium catalyst for sulfuric acid production is mixed with a vanadium leaching accelerator and then roasted. During the roasting process, the silica support becomes Na2SiO x or K2SiO xIt transforms into. During this process, the structure and pores of the silica, which was a stable compound, collapse; consequently, not only the vanadium oxide layer located on the surface of the support but also the vanadium oxide layer located within the pores of the support react with the vanadium leaching accelerator. As vanadium oxide reacts with the vanadium leaching accelerator, NaVO, which has high solubility in water, x or KVO x It changes into.

[0052] To summarize, before roasting, the structure has vanadium oxide formed on the surface and pores of the silica support (left side of Fig. 2), but after roasting, it takes the form of a mixture of vanadium compounds and silica compounds (right side of Fig. 2). In other words, during the roasting process, the vanadium oxide, which was located in the pores of the silica support and was difficult to leach out, was transformed into a form that could be leached out.

[0053] Next, a step is performed to prepare a vanadium leaching solution by leaching vanadium from the roasted material using water as a solvent.

[0054] NaVO formed during the roasting process x or KVO x It is a substance that is highly soluble in water, and is particularly soluble in alkaline environments. However, as the roasted product dissolves in water, the pH of the water becomes 12 to 14, so NaVO2 can be dissolved without other pH adjusters or additives. x or KVO x It is dissolved in water to produce a vanadium leaching solution.

[0055] In addition, as the roasted product dissolves in water, the pH of the water becomes 12 to 14, so red cake (Na2H2V6O 17 It is possible to prevent the formation of ) in advance.

[0056] In the step of forming the vanadium leaching solution, the solid-liquid ratio of the roasted material to water (S wt / L vol) can be 0.2 to 0.5, and at this time, 99 wt% or more of the vanadium contained in the vanadium catalyst for sulfuric acid production that has been used can be leached out.

[0057] After preparing the vanadium leaching solution, a step may be performed to purify and concentrate the vanadium leaching solution through a solvent extraction process, recover it as vanadium ammonium salt crystals, and produce vanadium pentoxide through pyrolysis. Known methods may be used to produce vanadium salt crystals or vanadium pentoxide from the vanadium leaching solution.

[0058]

[0059] Examples

[0060] Used vanadium catalyst for sulfuric acid production was ground and classified to 50 mesh (297 micron or less). The ground material was mixed with Na2CO3 in a weight ratio of 1:1 and roasted at 860°C for 1 hour. The roasted material was immersed in water to achieve a solid-to-liquid ratio of 0.2 or 0.5 and a leaching process was performed at room temperature for 30 minutes.

[0061] Table 1 shows the chemical analysis results when the solid-liquid ratio during leaching is 0.2 (Example 1), and Table 2 shows the chemical analysis results when the solid-liquid ratio during leaching is 0.5 (Example 2).

[0062]

[0063]

[0064]

[0065] CompositionVSiFeKCaAlCsConc., mg / L7,88510,11751,62537996

[0066]

[0067] CompositionVSiFeKCaAlCsConc., mg / L19,66720,22862,2985112,014

[0068]

[0069] In the case of Example 1, the vanadium leaching rate was 99.37 wt%, and in the case of Example 2, the vanadium leaching rate was 99.15 wt%. It can be seen that a very high vanadium leaching rate was achieved even though coarse particles were used as the pulverized material and the leaching process was carried out at room temperature for a short period of time.

[0070] Meanwhile, when the solid-to-liquid ratio increases, the vanadium concentration in the leachate increases without a decrease in the leaching rate. This means that when vanadium is recovered as vanadium salt or vanadium pentoxide through a precipitation process in a subsequent process, a higher recovery rate can be secured based on the same process. This is because, since the amount of vanadium remaining in the filtrate during precipitation is the same, a higher vanadium concentration in the mother liquor is more favorable for the recovery rate.

[0071] The scope of protection of the present invention is not limited to the description and expression of the embodiments explicitly described above. Furthermore, it is added once again that the scope of protection of the present invention cannot be limited by obvious changes or substitutions in the technical field to which the present invention belongs.

Claims

1. A step of forming a mixture by mixing a used vanadium catalyst for sulfuric acid production with a vanadium leaching promoter; A step of forming a roasted product by roasting the above mixture; and A step comprising: immersing the above-mentioned roasted product in water as a solvent to leach vanadium and form a vanadium leachate; Method for preparing a vanadium leaching solution using a used vanadium catalyst for sulfuric acid production.

2. In Paragraph 1, The vanadium catalyst for sulfuric acid production mentioned above, which has been used, is one in which V2O5 is supported on a SiO2 support, Method for preparing a vanadium leaching solution using a used vanadium catalyst for sulfuric acid production.

3. In Paragraph 2, The vanadium leaching promoter is at least one selected from the group consisting of Na2CO3 and K2CO3, Method for preparing a vanadium leaching solution using a used vanadium catalyst for sulfuric acid production.

4. In Paragraph 2, In the case where the vanadium leaching promoter is Na2CO3, the vanadium contained in the used vanadium catalyst for sulfuric acid production reacts with the vanadium leaching promoter to form NaVO3, and the SiO2 support reacts with the vanadium leaching promoter to form Na2SiO3. In the case where the vanadium leaching promoter is K2CO3, the vanadium contained in the used vanadium catalyst for sulfuric acid production reacts with the vanadium leaching promoter to form KVO3, and the SiO2 support reacts with the vanadium leaching promoter to form K2SiO3. Method for preparing a vanadium leaching solution using a used vanadium catalyst for sulfuric acid production.

5. In Paragraph 1, The above roasting is performed at a temperature of 851 ℃ or higher, Method for preparing a vanadium leaching solution using a used vanadium catalyst for sulfuric acid production.

6. In Paragraph 1, The content of the vanadium leaching promoter is 100 to 200 parts by weight per 100 parts by weight of the used vanadium catalyst for sulfuric acid production, Method for preparing a vanadium leaching solution using a used vanadium catalyst for sulfuric acid production.

7. In Paragraph 1, In the step of forming the vanadium leaching solution, the solid-liquid ratio (S) of the roasted material and the water wt / L vol ) is 0.2 to 0.5 in, Method for preparing a vanadium leaching solution using a used vanadium catalyst for sulfuric acid production. 8.(a) a step of preparing a vanadium leaching solution from a used vanadium catalyst for sulfuric acid production; and (b) a step of producing vanadium salt crystals or vanadium pentoxide from the vanadium leaching solution; comprising, The above step (a) is, A step of forming a mixture by mixing a used vanadium catalyst for sulfuric acid production with a vanadium leaching promoter; A step of forming a roasted product by roasting the above mixture; and A step comprising: immersing the above-mentioned roasted product in water as a solvent to leach vanadium and form a vanadium leachate; Method for recovering vanadium from a used vanadium catalyst for sulfuric acid production.

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