A method for preparing high-purity metatitanic acid using waste denitration catalyst

Abstract

The present invention relates to the field of resource recovery of spent denitration catalysts, and particularly to a method for preparing high-purity metatitanic acid from spent denitration catalysts. The spent denitration catalysts are treated with a mixed alkali solution, then cleaned and separated with an acid to obtain high-purity metatitanic acid solids. This method effectively removes impurities such as vanadium oxide, tungsten oxide, silicon oxide, and aluminum oxide from the spent denitration catalysts, recovering small, uniform metatitanic acid nanoparticles with a TiO2 content exceeding 99%, suitable for further preparation of novel electronic ceramic materials.

Description

Technical Field

[0001] The present invention belongs to the field of resource recovery of waste denitration catalysts, and in particular relates to a method for preparing high-purity metatitanic acid by utilizing waste denitration catalysts. Background Art

[0002] In recent years, with the intensification of my country's efforts to prevent and control air pollution and the large-scale application of denitrification technology, the amount of denitrification catalysts used and the total amount of deactivated catalysts have increased dramatically year by year, and the problem of handling scrapped denitrification catalysts has also arisen. According to statistics, the total amount of deactivated denitrification catalysts after 2022 will be close to 400,000 m3. 3 Each year, approximately 60% of deactivated catalysts cannot be regenerated due to poisoning of active components, overall structural collapse, and mechanical wear, becoming hazardous materials containing heavy metals. my country's 2016 National List of Hazardous Wastes designates spent vanadium-titanium denitrification catalysts as HW50 hazardous waste with leaching toxicity. Traditional methods of disposing of spent denitrification catalysts, such as crushing and landfilling, are not only costly and occupy land resources, but are also highly susceptible to soil and water pollution. Therefore, effectively reducing landfill volume and alleviating environmental pressures remains a persistent challenge for hazardous waste. Meanwhile, the combined W and V metal components in non-renewable denitrification catalysts account for 5-10%, with over 85% being TiO2, making them highly valuable for recycling. Therefore, developing technologies to recycle spent, non-renewable denitrification catalysts not only avoids environmental pollution but also offers significant economic benefits.

[0003] BaTiO3 series ceramics are a new type of electronic ceramic material developed in recent decades. They are widely used in the preparation of multilayer ceramic capacitors (MLCCs), thermistors (PTCRs), dynamic random access memories (DRAMs), temperature control sensors, etc., and are known as the "pillar of the electronic ceramics industry." The traditional industrial production of BaTiO3 powder is mainly based on the solid-phase method, which is to ball-mill the raw materials and then calcine them at high temperature to form barium titanate powder. This method has low equipment requirements and simple operation, but it is also accompanied by high energy consumption, large average particle size of the product powder, and easy agglomeration. Ultrafine barium titanate is prepared by hydrothermal method using titanic acid as the titanium source. It not only has a high proportion of tetragonal phase crystals, but also has uniform particle size and few defects. It can be used in the production of high-end electronic components.

[0004] In view of the above situation, if the waste denitrification catalyst can be utilized and used for the preparation of barium titanate, it will be of great significance for the resource utilization of the waste denitrification catalyst and the subsequent low-cost synthesis of electronic ceramic materials. Summary of the Invention

[0005] The purpose of the present invention is to provide a method for preparing high-purity metatitanic acid using waste denitration catalysts, which can not only recycle the deactivated and non-renewable denitration catalysts and avoid environmental pollution, but also contribute to the low-cost synthesis of subsequent electronic ceramic materials.

[0006] In order to solve the above technical problems, the technical solutions adopted by the present invention are as follows:

[0007] A method for preparing high-purity metatitanic acid by utilizing waste denitration catalysts comprises treating the waste denitration catalysts with a mixed alkali solution, washing with an acid after the treatment, and separating to obtain high-purity metatitanic acid solids.

[0008] The mixed alkali solution is a mixed solution of a strong base and a carbonate or bicarbonate, wherein the concentration of the strong base in the solution is 10-18 mol / L, and the concentrations of the carbonate and bicarbonate are respectively 0.1-2 mol / L.

[0009] Preferably, the mixed alkali solution is a mixed solution of NaOH and NaHCO3 or Na2CO3, or a mixed solution of KOH and KCO3 or K2CO3.

[0010] The amount of mixed alkali solution to be added is calculated based on adding 5-20 ml to 1 gram of spent denitrification catalyst.

[0011] The waste denitration catalyst is treated with mixed alkali solution to obtain sodium metatitanate, which can be divided into two steps:

[0012] First, the spent denitrification catalyst is treated with a mixed alkali solution in a colloid mill at a colloid mill speed of 2000-5000 r / min, a time of 1-5 hours, and an alkali washing temperature of 30-80°C.

[0013] The solid-liquid mixture after the colloid mill treatment is placed in another container such as a flask, heated and stirred, filtered, washed with water, and dried to obtain sodium metatitanate; the heating time is 1-4 hours, the temperature is 90-150°C, and the stirring speed is 200-500r / min.

[0014] Afterwards, the acid is used for cleaning for 2-5 hours at a temperature of 30-90°C and a solid-liquid ratio of 1:10-25 g / mL.

[0015] The concentration of the acid solution is 1-3 mol / L. The acid is preferably nitric acid or oxalic acid.

[0016] During pickling, a surfactant is added in an amount of 1-5 wt% of the pickling solid mass.

[0017] The surfactant can be selected from dodecylbenzenesulfonic acid or sodium alkylbenzenesulfonate.

[0018] The method for preparing high-purity metatitanic acid using spent denitrification catalyst can be divided into three steps:

[0019] (1) The spent denitration catalyst after preliminary dust removal, washing, and grinding (the above three steps are the pretreatment steps) is mixed with a hot alkaline solution and placed in a colloid mill for thorough stirring and mixing;

[0020] (2) placing the solid-liquid mixture obtained in step (1) in a flask, heating and stirring, filtering, washing with water, and drying to obtain crude titanium slag, i.e., sodium metatitanate;

[0021] (3) Add the crude titanium slag obtained in step (2) into a hot acid solution, add a surfactant, stir and pickle, filter, wash with water, and dry to obtain high-purity titanic acid.

[0022] Specifically, the steps are as follows:

[0023] (1) The pretreated waste denitration catalyst is mixed with a mixed alkali solution and placed in a colloid mill for thorough mixing, wherein the solid-liquid ratio of the mixed alkali solution to the waste denitration catalyst is 1:5-20 g / mL, the alkali washing time is 1-5 h, and the alkali washing temperature is 30-80° C.; the mixed alkali solution is a mixed solution of NaOH and NaHCO 3 or Na 2 CO 3 , wherein the concentration of NaOH is 10-18 mol / L, and the concentration of NaHCO 3 or Na 2 CO 3 is 0.1-2 mol / L;

[0024] (2) heating and stirring the solid-liquid mixture in step (1), performing alkaline washing for 1-4 hours at a temperature of 90-150° C. and a stirring speed of 200-500 r / min, and then filtering, washing with water, and drying to obtain sodium metatitanate;

[0025] (3) adding the above solid powder to a 1-3 mol / L nitric acid or oxalic acid solution and heating with stirring, with a solid-to-liquid ratio of 1:10-25 g / mL, and simultaneously adding 1-5 wt% of dodecylbenzenesulfonic acid or sodium alkylbenzenesulfonate; acid washing time is 2-5 h, temperature is 30-90 ° C, and then filtering, washing with water, and drying to obtain a high-purity metatitanic acid solid powder.

[0026] The present invention relates to a method for preparing high-purity metatitanic acid from spent denitration catalysts. The method comprises treating the spent denitration catalyst with a mixed alkali solution to obtain sodium metatitanate, followed by washing with a hot acid solution, and then separating the resulting high-purity metatitanic acid solid. The alkali washing step utilizes a mixed alkali solution. Because tungsten in the denitration catalyst can enter the TiO2 lattice and is therefore more difficult to remove than vanadium, the mixed alkali solution improves the leaching rate of W. The addition of a surfactant in the acid washing step facilitates the removal of alkali metals attached to the catalyst surface, further improving product purity.

[0027] The method of the present invention can effectively remove impurities such as vanadium oxide, tungsten oxide, silicon oxide, aluminum oxide, etc. from the waste denitrification catalyst, and even recover titanate nanoparticles with a TiO2 content greater than 99% and a small and uniform particle size, which are suitable for further preparation of new electronic ceramic materials. DETAILED DESCRIPTION

[0028] The technical solution of the present invention is described below with reference to specific embodiments, but the protection scope of the present invention is not limited thereto:

[0029] Example 1

[0030] The method for preparing high-purity metatitanic acid using waste denitration catalyst comprises the following steps:

[0031] 1) Prepare a mixed solution of NaOH and Na2CO3, wherein the concentration of NaOH is 16M and the concentration of Na2CO3 is 1M.

[0032] 50 g of spent denitration catalyst was fully mixed with 750 mL of mixed alkali solution and placed in a colloid mill. The colloid mill speed was controlled at 2500 r / min, the alkali washing time was 3 h, and the temperature was 40°C.

[0033] 2) Transfer the alkaline-washed solid-liquid mixture to a 1L flask, heat in an oil bath to 110°C, and stir at 300 rpm for 3 hours. Filter the mixture, wash with deionized water until neutral, and dry for later use.

[0034] 3) Prepare a 3M nitric acid solution, thoroughly mix 50 g of the powder from step 2) with 500 mL of the nitric acid solution, add 1 g of sodium alkylbenzene sulfonate, and stir at 50°C for 4 h. Wash with clean water until neutral and then dry to obtain metatitanic acid powder.

[0035] XRF results showed that the TiO2 content in the obtained metatitanic acid powder was 99.45%.

[0036] Example 2-3

[0037] The alkaline washing and acid washing processes were the same as those in Example 1, except that the solid-liquid ratios in step 1) were changed to 1:5 and 1:10, respectively.

[0038] XRF results showed that the TiO2 contents in the metatitanic acid powders were 93.26% and 95.74%, respectively.

[0039] Examples 4-6

[0040] The alkaline washing and acid washing processes were the same as in Example 1, but the concentration of NaOH was changed to 10 M, 12 M and 14 M respectively.

[0041] XRF results showed that the TiO2 contents in the metatitanic acid powders were 88.24%, 94.75% and 96.62%, respectively.

[0042] Comparative Example 1

[0043] The alkaline washing and acid washing process of the spent denitration catalyst was the same as that in Example 1, except that the mixed alkaline solution was replaced with a single NaOH solution with a concentration of 16M.

[0044] XRF results showed that the TiO2 content in the obtained metatitanic acid powder was 97.52%.

[0045] Comparative Example 2

[0046] The alkaline washing and acid washing process of the spent denitration catalyst is the same as that in Example 1, but no surfactant is added during the acid washing process.

[0047] XRF results showed that the TiO2 content in the obtained metatitanic acid powder was 94.43%.

Claims

1. A method for preparing high-purity metatitanic acid using spent denitration catalyst, characterized in that: The spent denitration catalyst is treated with a mixed alkali solution, which is then washed and separated with an acid to obtain a high-purity metatitanic acid solid; the mixed alkali solution is a mixed solution of a strong base and a carbonate or bicarbonate, wherein the concentration of the strong base in the solution is 10-18 mol / L, and the concentration of the carbonate and bicarbonate is 0.1-2 mol / L; the amount of the mixed alkali solution added is calculated based on the addition of 5-20 ml of the mixed alkali solution to 1 gram of the spent denitration catalyst; The acid cleaning time is 2-5 h, the temperature is 30-90 ° C, the solid-liquid ratio is 1:10-25 g / mL, and a surfactant is added during acid cleaning, and the added amount is 1-5 wt% of the acid-washed solid mass.

2. The method for preparing high-purity metatitanic acid using a waste denitration catalyst according to claim 1, wherein: When the spent denitrification catalyst is treated with mixed alkali solution, it is first carried out in a colloid mill with a colloid mill speed of 2000-5000 r / min, a time of 1-5 hours, and an alkali washing temperature of 30-80°C.

3. The method for preparing high-purity metatitanic acid using a waste denitration catalyst according to claim 2, wherein: The solid-liquid mixture after the colloid mill treatment is placed in another container and heated and stirred, filtered, washed with water, and dried to obtain sodium metatitanate; the heating time is 1-4 hours, the temperature is 90-150°C, and the stirring speed is 200-500 r / min.

4. The method for preparing high-purity metatitanic acid using a waste denitration catalyst according to claim 1, wherein: The concentration of the acid solution is 1-3 mol / L.

5. The method for preparing high-purity metatitanic acid using a waste denitration catalyst according to claim 4, wherein: The acid is nitric acid or oxalic acid.

6. The method for preparing high-purity metatitanic acid using a waste denitration catalyst according to any one of claims 1 to 5, characterized in that: Here are the steps: (1) The pretreated waste denitration catalyst is mixed with a mixed alkali solution and placed in a colloid mill for thorough mixing. The solid-liquid ratio of the mixed alkali solution to the waste denitration catalyst is 1:5-20 g / mL, the alkali washing time is 1-5 h, and the alkali washing temperature is 30-80°C. The mixed alkali solution is a mixed solution of NaOH and NaHCO3 or Na2CO3, the concentration of NaOH is 10-18 mol / L, and the concentration of NaHCO3 or Na2CO3 is 0.1-2 mol / L. (2) heating and stirring the solid-liquid mixture in step (1), performing alkaline washing for 1-4 h, at a temperature of 90-150° C., and at a stirring speed of 200-500 r / min, and then filtering, washing with water, and drying to obtain sodium metatitanate solid; (3) Add the above solid to 1-3 mol / L nitric acid or oxalic acid solution and heat with stirring, with a solid-liquid ratio of 1:10-25 g / mL, and add 1-5 wt% of dodecylbenzenesulfonic acid or sodium alkylbenzenesulfonate at the same time; the pickling time is 2-5 h, the temperature is 30-90 ° C, and then filter, wash with water, and dry to obtain high-purity titanate solid powder.