A method for preparing rutile titanium dioxide from waste denitration catalyst

Abstract

The present application belongs to the field of solid waste resource recycling, and particularly relates to a method for preparing rutile type titanium dioxide from waste denitration catalyst. The waste denitration catalyst is treated with mixed alkali liquor, and then treated with nitric acid, and then separated, dried and calcined to obtain rutile type titanium dioxide. The present application has important role in resource utilization of waste denitration catalyst, reduction of mineral resource exploitation, energy saving and emission reduction. In addition, the present application provides a preparation method different from the existing rutile type nano titanium dioxide, which is not only simple in process, but also avoids the defects of existing high-temperature calcination, and the obtained rutile type nano titanium dioxide has high purity.

Description

TECHNICAL FIELD

[0001] The application belongs to the field of solid waste resource recycling, and particularly relates to a method for preparing rutile titanium dioxide from waste denitration catalysts. BACKGROUND

[0002] In recent years, with the increasing environmental protection efforts, the catalytic denitration technology is widely applied, but along with it, about 240,000 tons of waste denitration catalysts are generated in China every year. 3 The deactivated denitration catalysts cannot be regenerated and must be disposed as hazardous waste. The main disposal method in the industry is to make powder after physical cleaning and then mix with new catalysts, but the mixing amount is limited and the service life of the new catalysts is significantly reduced. On the other hand, the total amount of metals such as W and V in the waste denitration catalysts is 5-10%, and more than 85% is TiO2. Therefore, the resource utilization of the waste catalysts can not only effectively reduce the waste of strategic reserve resources such as vanadium, tungsten and titanium, but also effectively reduce the mining of related mineral resources and improve the ecological environment.

[0003] Titanium dioxide, also known as titanium dioxide (TiO2), is widely used in catalysts, coatings, inks, plastics, rubbers, cosmetics and other fields due to its stable physical and chemical properties. Titanium dioxide can be divided into anatase, rutile and brookite according to crystal form. Among them, rutile titanium dioxide is the best white inorganic pigment in the world and is widely used in coatings, inks and other fields. Currently, rutile titanium dioxide is prepared by calcining metatitanic acid obtained by sulfuric acid method or chlorination method at high temperature (about 1050℃) for a long time. However, the titanium dioxide obtained by the above method is easy to sinter, has many crystal defects, large crystal grains, high hardness, and high temperature leads to lattice deoxidation, which makes the product gray and affects the whiteness. Therefore, conversion promoters and crystal form regulators are often added in the industrial production process to reduce the calcination temperature and control the rutile crystal form. Even so, the calcination temperature is still above 900℃, and the rutile titanium dioxide crystal form and morphology are not easy to control at high temperature. SUMMARY

[0004] The purpose of the present application is to provide a method for preparing high-purity rutile titanium dioxide from waste denitration catalysts, which not only recycles and utilizes the deactivated denitration catalysts, but also provides a new method for preparing rutile titanium dioxide with guaranteed quality.

[0005] To solve the above technical problems, the technical scheme adopted by the present application is as follows:

[0006] A method for preparing rutile titanium dioxide from waste denitration catalysts, wherein the waste denitration catalysts are treated with mixed alkali solution, then treated with nitric acid, and then separated, dried and calcined to obtain rutile titanium dioxide.

[0007] The mixed alkali liquor is a mixed solution of strong alkali and carbonate or bicarbonate, the concentration of the strong alkali in the solution is 10-18 mol / L, and the concentration of the carbonate or bicarbonate is 0.1-2 mol / L.

[0008] Preferably, the mixed alkali liquor is a mixed solution of NaOH and NaHCO3 or Na2CO3, or a mixed solution of KOH and KCO3 or K2CO3.

[0009] According to 1 g of the waste denitration catalyst, 5-20 ml of the calculated amount of the mixed alkali liquor is added.

[0010] After the waste denitration catalyst is treated with the mixed alkali liquor, sodium metatitanate is obtained, which can be obtained by two steps:

[0011] 1) The waste denitration catalyst is first treated with the mixed alkali liquor in a colloid mill, the rotation speed of the colloid mill is 2000-5000 r / min, the time is 1-5 h, and the alkali washing temperature is 30-80℃.

[0012] 2) The solid-liquid mixture treated by the colloid mill is placed in another container for heating and stirring, and sodium metatitanate is obtained after filtration, water washing and drying; the heating time is 1-4 h, the temperature is 90-150℃, and the stirring rotation speed is 200-500 r / min.

[0013] The treatment with nitric acid is that the product treated with the mixed alkali liquor is mixed with nitric acid and treated at 70-160℃ for 2-12 h.

[0014] Preferably, the acid washing temperature is higher than 90℃ or the acid washing time is greater than 5 h, so that pure rutile TiO2 can be obtained.

[0015] The concentration of the nitric acid solution is 2-7 mol / L.

[0016] According to 1 g of the product treated with the mixed alkali liquor, 10-35 ml of the amount is mixed with nitric acid.

[0017] The method of the present application can prepare pure rutile TiO2 or mixed TiO2 with different rutile contents by changing the concentration of nitric acid, the acid washing time, the acid washing temperature, the solid-liquid ratio and the like. When the acid washing reaction temperature is greater than 90℃ or the acid washing time is greater than 5 h, pure rutile TiO2 can be obtained.

[0018] The calcination temperature is 400-600℃, the time is 2-4 h, and the temperature rising rate is 2-10℃ / min.

[0019] Specifically, the method for preparing rutile TiO2 from the waste denitration catalyst comprises the following steps:

[0020] (1) the pretreated waste denitration catalyst is mixed with mixed alkali liquor and placed in a colloid mill for sufficient mixing, the solid-liquid ratio of the mixed alkali liquor 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 ℃; the mixed alkali liquor 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;

[0021] (2) the solid-liquid mixture in step (1) is heated and stirred, the alkali washing time is 1-4 h, the temperature is 90-150 ℃, and the stirring speed is 200-500 r / min, and then the sodium metatitanate solid is obtained by filtration, water washing and drying;

[0022] (3) the sodium metatitanate solid is added into 2-7 mol / L nitric acid for heating and stirring, the solid-liquid mass-volume ratio is 1:10-35, the time is 2-12 h, and the temperature is 70-160 ℃; and then high-purity rutile type nano titanium dioxide is obtained by filtration, water washing, drying and calcination at 400-600 ℃ for 2-4 h.

[0023] Compared with the prior art, the present application has the following advantages:

[0024] The present application has the following advantages: BRIEF DESCRIPTION OF DRAWINGS

[0025] Figure 1 XRD patterns of the anatase type, rutile type, anatase and rutile mixed type titanium dioxide prepared in the embodiment part of the present application. DETAILED DESCRIPTION

[0026] The technical solutions of the present application are described below with specific embodiments, but the protection scope of the present application is not limited thereto: Example 1

[0027] The method for preparing anatase type titanium dioxide from waste denitration catalyst is as follows:

[0028] 1) a mixed solution of NaOH and Na2CO3 is prepared, wherein the concentration of NaOH is 16 M, and the concentration of Na2CO3 is 1 M;

[0029] 50 g of waste denitration catalyst was mixed with 750 mL of mixed alkali solution and placed in a colloid mill, the rotation speed of the colloid mill was controlled at 2500 r / min, the alkali washing time was 3 h, and the temperature was 40°C.

[0030] 2) The solid-liquid mixture after alkali washing was transferred to a 1 L flask, heated to 110°C in an oil bath, and stirred at a speed of 300 r / min for 3 h. Then the mixture was filtered and washed with deionized water until neutral, and then dried for use.

[0031] 3) A 1 M nitric acid solution was prepared, 50 g of the powder of step 2) was mixed with 500 mL of the nitric acid solution, and stirred at 90°C for 4 h. After washing with water until neutral, the product was dried to obtain a metatitanic acid powder, and the XRD characterization result was Figure 1 metatitanic acid of medium anatase type. After calcination at 450°C for 2 h, anatase type titanium dioxide was obtained. The XRF result showed that the purity of the product was 99.12%.

[0032] It can be seen that when the concentration of nitric acid is less than the range required by the present application, the final product is anatase TiO2.

[0033] Example 2

[0034] The method for preparing rutile type titanium dioxide from waste denitration catalyst is as follows:

[0035] The alkali washing and acid washing processes were the same as in Example 1, but the concentration of nitric acid in step 3) was changed to 4 M, and the XRD characterization result of the obtained metatitanic acid powder was Figure 1 metatitanic acid of medium anatase type. After calcination at 450°C for 2 h, anatase type titanium dioxide was obtained. The XRF result showed that the purity of the product was 99.12%.

[0036] Example 3

[0037] The alkali washing and acid washing processes were the same as in Example 1, but the concentration of nitric acid in step 3) was changed to 4 M, and the acid washing temperature was 80°C, and the acid washing time was 10 h. The obtained metatitanic acid powder was metatitanic acid of rutile type. After calcination at 450°C for 2 h, rutile type titanium dioxide was obtained.

[0038] Example 4

[0039] The alkali washing and acid washing processes were the same as in Example 1, but the concentration of nitric acid in step 3) was changed to 2 M, and the acid washing temperature was 100°C. The obtained metatitanic acid powder was metatitanic acid of rutile type. After calcination at 450°C for 2 h, rutile type titanium dioxide was obtained.

[0040] Example 5

[0041] The alkali washing and acid washing processes were the same as in Example 1, but the concentration of nitric acid in step 3) was changed to 2 M, and the acid washing temperature was 80°C. The XRD characterization result of the obtained metatitanic acid powder wasFigure 1 Intermediate mixed type metatitanic acid.

[0042] The proportion of rutile type was calculated using Formula 1:

[0043]

[0044] wherein Ia represents the intensity of the anatase peak near 25.4° in the XRD pattern, and Ir represents the intensity of the rutile peak near 27.5°. The proportion of rutile type was calculated to be 62.43%.

Claims

1. A method for producing rutile-type titanium dioxide from a waste de-NOx catalyst, characterized by, The waste denitration catalyst is treated with mixed alkali liquor, and then treated with nitric acid, and then separated, dried and calcined to obtain rutile type titanium dioxide; The mixed alkali liquor is a mixed solution of strong alkali and carbonate or bicarbonate, the concentration of the strong alkali in the solution is 10-18 mol / L, the concentration of the carbonate or bicarbonate is 0.1-2 mol / L, and 5-20 ml of the mixed alkali liquor is added per 1 g of the waste denitration catalyst; The treatment with nitric acid is that the product treated with the mixed alkali liquor is mixed with nitric acid, and treated at 90-160℃ for 2-12 h or at 70-160℃ for 5-12 h, and the concentration of the nitric acid solution is 2-7 mol / L; 10-35 mL of the product treated with the mixed alkali liquor is mixed with nitric acid.

2. The method of claim 1, wherein the spent de-NOx catalyst is prepared by a process comprising: (a) preparing a mixture of the spent de-NOx catalyst and a titanium compound; (b) calcining the mixture; and (c) preparing a mixture of the calcined mixture and a titanium compound; and (d) calcining the mixture. The treatment of the waste denitration catalyst with the mixed alkali liquor is first carried out in a colloid mill, the rotation speed of the colloid mill is 2000-5000 r / min, the time is 1-5 h, and the alkali washing temperature is 30-80℃.

3. The method for preparing rutile titanium dioxide from spent denitrification catalyst as described in claim 2, characterized in that, The solid-liquid mixture treated with the colloid mill is placed in another container for heating and stirring, and then filtered, washed with water and dried to obtain sodium metatitanate; the heating time is 1-4 h, the temperature is 90-150℃, and the stirring speed is 200-500 r / min.

4. The method for preparing rutile titanium dioxide from spent denitrification catalyst as described in claim 1, characterized in that, The calcination temperature is 400-600℃, the time is 2-4 h, and the temperature rising rate is 2-10 ℃ / min.

5. The method of preparing rutile titanium dioxide from spent de-NOx catalyst according to any one of claims 1 to 4, characterized in that, The steps are as follows: (1) the pretreated waste denitration catalyst is mixed with the mixed alkali liquor in the colloid mill, the solid-liquid ratio of the 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℃; the mixed alkali liquor 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) the solid-liquid mixture in step (1) is heated and stirred, the alkali washing time is 1-4 h, the temperature is 90-150℃, and the stirring speed is 200-500 r / min, and then filtered, washed with water and dried to obtain sodium metatitanate solid; (3) the sodium metatitanate solid is added to 2-7 mol / L nitric acid for heating and stirring, the solid-liquid mass volume ratio is 1:10-35, and treated at 90-160℃ for 2-12 h or at 70-160℃ for 5-12 h; and then filtered, washed with water and dried, and calcined at 400-600℃ for 2-4 h to obtain high-purity rutile type nano titanium dioxide.

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