CN114477214A - A kind of method for removing alkali metal from molecular sieve - Google Patents

Abstract

The invention discloses a method for removing alkali metal from a molecular sieve, which is characterized by comprising the following steps: the method comprises the steps of carrying out hydrothermal roasting treatment on an alkali metal-containing molecular sieve under the atmosphere environment of externally applying pressure and externally adding water containing an acidic substance or an alkaline substance, and then carrying out 1-2 times of rinsing with deionized water containing acidity and drying treatment to obtain the alkali metal-containing molecular sieve, wherein the atmosphere environment is 0.01-1 Mpa and contains 1-100% of water vapor, and the hydrothermal roasting treatment temperature is 200-800 ℃. The method can reduce the alkali metal content of the molecular sieve to below 10 wt% by adopting a simpler method.

Description

A kind of method for removing alkali metal from molecular sieve

technical field

The invention relates to a method for removing alkali metals from molecular sieves.

Background technique

With the development of industrialization, molecular sieves are used more and more widely in production. Taking Y-type molecular sieve as an example, Y-type molecular sieve is used in a large amount in industrial applications. The annual domestic production volume exceeds 70,000 tons, and the catalyst is formulated into nearly 200,000 tons. Nearly 150 million tons of oil products are processed with such catalysts each year to produce fuels and chemicals. , widely used in catalytic cracking (FCC), catalytic cracking, hydrogenation, alkylation, transalkylation, lightening of heavy aromatics, light cycle oil (LCO) upgrading, acylation and other processes.

Y-type molecular sieve was synthesized in a sodium-containing aluminosilicate crystallization system, and the initial state was stable NaY form. Since the negative charge of the aluminum oxide tetrahedron is completely neutralized by the positive charge of Na ⁺ , the NaY molecular sieve itself has no acidity. In order to obtain the acidity required for the catalytic reaction, the sodium in the molecular sieve must be removed. Another reason for de-sodiumization is that sodium has a great negative effect on the activity and hydrothermal stability of molecular sieves. In the traditional preparation method, the commonly used molecular sieve sodium removal technology is the solution ion exchange method. The specific method is: mixing and beating NaY molecular sieve, ammonium salt and water according to a certain proportion, adjusting the pH value to be acidic, and controlling the temperature at 65-95. ℃, after exchange for 0.5 to 2 hours, high temperature calcination (550-580 ℃). The exchange and roasting process is repeated 2 to 4 times as required, and excessive ammonium salt needs to be added, resulting in the discharge of a large amount of high-concentration ammonia nitrogen wastewater and polluting the environment. Therefore, how to adopt a new technology to shorten the process flow for rapid NaY removal has become a major technical problem to be solved in the industry.

CN1911513A discloses a method of mixing NaY molecular sieve with water and inorganic ammonium salt for beating, and using an alkaline solution to adjust the pH value of the system to 9-12, and exchanging at 65-90°C. After one exchange, the sodium content is reduced to below 5%. This method can repeatedly adjust the acidity and alkalinity of the system, but the sodium removal effect is not very satisfactory.

CN101633507A discloses a solid-phase ammonium exchange method, that is, according to the weight ratio of molecular sieve: ammonium salt=1:(0.1～1.0), NaY molecular sieve and ammonium salt are mixed, the temperature is kept for 1 hour, and the ammonium exchange is obtained by washing with water once. Molecular Sieve. Although the method of this invention reduces the consumption of ammonium salt and water, the content of sodium in the product is still more than 2%.

CN10570334A discloses a modified NaY molecular sieve by using ion exchange resin. The ion exchange reaction is carried out in two adjacent reaction chambers. There is no direct contact with the ion resin, and the hydrogen ion and sodium ion can be exchanged through the screen under the promotion of their concentration difference, but the sodium removal effect of this method is limited.

As can be seen from the above-mentioned prior art, NaY molecular sieve is subjected to de-sodium treatment, which needs to go through the above-mentioned high-temperature roasting and ammonium exchange steps, and a large amount of ammonia nitrogen waste water will be produced during the ammonium exchange process, which makes the treatment pressure of enterprise waste water larger. Therefore, how to adopt a sodium removal technology that reduces the discharge of ammonia nitrogen wastewater is an urgent problem to be solved. For structural formulas such as MOR and MFI, there is also the problem of how to remove alkali metals while meeting environmental protection requirements.

SUMMARY OF THE INVENTION

The purpose of the present invention is to provide a relatively simple method for removing alkali metals from molecular sieves, which is different from conventional ammonium exchange for removing alkali metals so that the content of alkali metal oxides in molecular sieves can be reduced to less than 10% by weight.

A method for removing alkali metals from a molecular sieve provided by the present invention is characterized in that the method comprises: hydrothermally heating the molecular sieve containing an alkali metal in an atmosphere environment where external pressure is applied and water containing an acidic substance or an alkaline substance is added externally. Roasting treatment, and then leaching with acidic deionized water and drying to prepare, wherein the atmosphere environment, the apparent pressure is 0.01 ~ 1Mpa and contains 1 ~ 100% water vapor, hydrothermal roasting treatment temperature At 200 ~ 800 ℃.

In the preparation method of the present invention, the apparent pressure is 0.01-1Mpa, preferably the apparent pressure is 0.05-0.6MPa, more preferably the apparent pressure is 0.1-0.5MPa, preferably 30-100% water vapor, more preferably Contains 60-100% water vapor.

In the preparation method of the present invention, the acidic substance is selected from the group consisting of ammonium chloride, ammonium sulfate, ammonium carbonate, ammonium bicarbonate, ammonium phosphate, ammonium dihydrogen phosphate, diammonium hydrogen phosphate, hydrochloric acid, sulfuric acid, and nitric acid. or a mixture of various.

In the preparation method of the present invention, the alkaline substance comprises a mixture of one or more of ammonia water, ammonia water and ammonium chloride buffer solution.

In the preparation method of the present invention, the weight ratio of the acid-containing deionized water to the molecular sieve is 1-20, preferably 6-15, more preferably 8-12.

In the preparation method of the present invention, the acid-containing deionized water refers to deionized water diluted with an acid such as nitric acid and adjusted to pH 3-7, preferably pH 2-6, more preferably pH 3-5. Ionized water.

In the preparation method of the present invention, the acid-containing deionized water leaching is performed at a temperature of 30-100°C, preferably 60-80°C.

The preparation method of the present invention can be applied to various alkali metal-containing molecular sieves, such as one or more selected from FAU, MOR, and MFI molecular sieves. In the alkali metal-containing molecular sieve, the alkali metal is selected from one or more of Na, K, Rb and Cs, and the content of the alkali metal is 0.1-20% based on the weight of the alkali metal-containing molecular sieve.

The method for removing alkali metal from the molecular sieve provided by the present invention is different from the conventional method. For example, taking NaY molecular sieve as an example, the sodium oxide content of the obtained NH ₄ NaY molecular sieve can be reduced to less than 10% by weight by a relatively simple method, which avoids to a certain extent the generation of a large amount of ammonia nitrogen wastewater during the ammonium exchange process.

Detailed ways

The present invention will be further illustrated by the following examples, but the content of the present invention is not limited thereby.

The X-ray diffraction pattern was measured on Rigaku TTR-3 powder X-ray diffractometer. Instrument parameters: copper target (tube voltage 40kV, tube current 250mA), scintillation counter, step width 0.02°, scan rate 0.4(°)/min .

The analysis of chemical composition was carried out on a 3013 X-ray fluorescence spectrometer (XRF) of Rigaku Electric Co., Ltd., Japan, using a tungsten target, an excitation voltage of 40 kV, and an excitation current of 50 mA.

The NaY molecular sieve raw material used in the comparative examples and examples is produced by the Changling Branch of Sinopec Catalyst Company, the content of sodium oxide is 13.4% by weight, the unit cell constant is 2.465nm, and the crystallinity is 84.1%.

Example 1

Example 1 illustrates the NaY molecular sieve de-sodium method of the present invention.

Take 100g of NaY molecular sieve and add 10g of ammonia water, at 500 ℃ and external pressure to make the apparent pressure 0.3Mpa, 100% water vapor atmosphere for hydrothermal roasting for 2h, and then use 10 times the pH value of 4 according to the dry weight of molecular sieve. The acid-containing deionized water was washed with acidic water once, the water temperature was 60°C, and the NH ₄ NaY molecular sieve sample was obtained by filtration and drying treatment, which was denoted as JNY-1. Its physical properties are shown in Table 1.

Comparative Example 1

Comparative Example 1 illustrates a comparative sample of NH ₄ NaY molecular sieve obtained by hydrothermal calcination at atmospheric pressure.

Same as Example 1, the difference is that the calcination condition is normal pressure (apparent pressure 0Mpa). A comparative sample of NH4NaY molecular sieve was obtained, which was recorded as DBNY-1. Its physical properties are shown in Table 1.

Example 2

Example 2 illustrates the NaY molecular sieve de-sodium method of the present invention.

Take 100g of NaY molecular sieve and apply pressure externally, add 8g of ammonia water and 15g of ammonium carbonate, hydrothermally calcinate for 2h at 400°C, apparent pressure of 0.5Mpa, and 100% steam atmosphere for 2h, and then proceed according to molecular sieve and pH 6 acidic water. According to the dry basis weight ratio of 1:8, the acid water was rinsed once, the water temperature was 70°C, and the NH ₄ NaY molecular sieve sample was obtained by filtration and drying treatment, which was denoted as JNY-2. Its physical properties are shown in Table 1.

Comparative Example 2

Comparative Example 2 illustrates a comparative sample of NH ₄ NaY molecular sieve obtained by hydrothermal calcination at atmospheric pressure.

Same as Example 1, the difference is that the calcination condition is normal pressure (apparent pressure 0Mpa). A comparative sample of NH ₄ NaY molecular sieve was obtained, which was designated as DBNY-2. Its physical properties are shown in Table 1.

Example 3

Example 3 illustrates the NaY molecular sieve de-sodium method of the present invention.

Take 100g of NaY molecular sieve and apply pressure externally and add 16g of ammonium carbonate, 300 ° C, apparent pressure 0.6Mpa, 90% water vapor atmosphere for hydrothermal roasting for 2h, and then according to molecular sieve and pH value of 5 acidic water according to 1: The dry basis weight ratio of 12 was washed twice with acidic water, the water temperature was 90°C, and the NH ₄ NaY molecular sieve sample was obtained by filtration and drying treatment, which was denoted as JNY-3. Its physical properties are shown in Table 1.

Comparative Example 3

Comparative Example 3 illustrates a comparative sample of NH ₄ NaY molecular sieve obtained by hydrothermal calcination at atmospheric pressure.

Same as Example 1, the difference is that the calcination condition is normal pressure (apparent pressure 0Mpa). A comparative sample of NH ₄ NaY molecular sieve was obtained, which was designated as DBNY-3. Its physical properties are shown in Table 1.

Example 4

Example 4 illustrates the NaY molecular sieve de-sodium method of the present invention.

Take 100g of NaY molecular sieve and apply pressure externally and add 6g of hydrochloric acid, hydrothermally calcined at 450°C, with an apparent pressure of 0.3Mpa and 60% water vapor for 2h, and then according to molecular sieve and pH 4 acidic water at 1:10 The dry weight ratio of NH 4 NaY molecular sieve sample was obtained by acid leaching once, the water temperature was 100 ° C, and the NH ₄ NaY molecular sieve sample was obtained by filtration and drying treatment, which was denoted as JNY-4. Its physical properties are shown in Table 1.

Comparative Example 4

Comparative Example 4 illustrates a comparative sample of NH ₄ NaY molecular sieve obtained by hydrothermal calcination at atmospheric pressure.

Same as Example 1, the difference is that the calcination condition is normal pressure (apparent pressure 0Mpa). A comparative sample of NH ₄ NaY molecular sieve was obtained, which was designated as DBNY-4. Its physical properties are shown in Table 1.

Example 5

Example 5 illustrates the NaY molecular sieve de-sodium method of the present invention.

Take 100g of NaY molecular sieve and apply external pressure and add 16g of ammonium bicarbonate, hydrothermally calcined for 2h at 350°C, apparent pressure 0.5Mpa, 80% steam atmosphere, and then proceed according to molecular sieve and pH 3 acidic water according to 1 The NH 4 NaY molecular sieve sample was obtained by filtration and drying treatment at a dry weight ratio of : 15, and the water temperature was 80° C. to obtain an NH ₄ NaY molecular sieve sample, which was denoted as JNY-5. Its physical properties are shown in Table 1.

Comparative Example 5

Comparative Example 5 illustrates a comparative sample of NH ₄ NaY molecular sieve obtained by hydrothermal calcination at atmospheric pressure.

Same as Example 1, the difference is that the calcination condition is normal pressure (apparent pressure 0Mpa). A comparative sample of NH ₄ NaY molecular sieve was obtained, which was designated as DBNY-5. Its physical properties are shown in Table 1.

Example 6

Example 6 illustrates the NaY molecular sieve de-sodium method of the present invention.

Take 100g of NaY molecular sieve and apply external pressure, add 12g of ammonia water and 10g of ammonium bicarbonate, and conduct hydrothermal roasting at 430°C, under an atmosphere of 0.4Mpa and 50% water vapor for 2h, and then proceed according to molecular sieve and pH 5 acidic Water was rinsed twice with acidic water at a dry weight ratio of 1:8, the water temperature was 90° C., filtered and dried to obtain a NH ₄ NaY molecular sieve sample, which was denoted as JNY-6. Its physical properties are shown in Table 1.

Comparative Example 6

Comparative Example 6 illustrates a comparative sample of NH ₄ NaY molecular sieve obtained by hydrothermal calcination at atmospheric pressure.

Same as Example 1, the difference is that the calcination condition is normal pressure (apparent pressure 0Mpa). A comparative sample of NH ₄ NaY molecular sieve was obtained, which was designated as DBNY-6. Its physical properties are shown in Table 1.

Table 1

sample name Na₂O content, %(w) Unit cell constant, nm Crystallinity, %(w) Example 1 JNY-1 9.2 2.458 82.6 Comparative Example 1 DBNY-1 11.8 2.455 78.1 Example 2 JNY-2 8.0 2.463 84.5 Comparative Example 2 DBNY-2 11.2 2.461 80.1 Example 3 JNY-3 7.4 2.464 86.4 Comparative Example 3 DBNY-3 10.8 2.462 81.2 Example 4 JNY-4 9.2 2.463 82.3 Comparative Example 4 DBNY-4 11.6 2.461 76.9 Example 5 JNY-5 9.5 2.464 85.6 Comparative Example 5 DBNY-5 11.8 2.463 82.1 Example 6 JNY-6 8.7 2.463 81.7 Comparative Example 6 DBNY-6 11.2 2.461 80.3

As can be seen from the results in Table 1, using the method for removing alkali metals from molecular sieves provided by the present invention, compared with the comparative samples obtained in the corresponding comparative examples, the crystallinity is increased by 1.4-5.4 percentage points, and the Na ₂ O content is reduced by 2.4-3.4 percentage points %, that is, the method of the present invention has a better technical effect of dealkalizing metal on the basis of keeping the crystal structure relatively complete.

Claims (11)

1. a method for removing alkali metal from a molecular sieve, it is characterized in that the method comprises: the molecular sieve containing alkali metal is subjected to hydrothermal roasting treatment under external applied pressure and externally adding the atmosphere environment of the water containing acidic substance or alkaline substance, Then it is prepared by rinsing with acidic deionized water and drying, wherein the atmosphere environment has an apparent pressure of 0.01-1Mpa and contains 1-100% water vapor, and the hydrothermal roasting treatment temperature is 200-100%. 800°C. 2. The preparation method according to claim 1, wherein the apparent pressure is 0.05-0.6MPa, preferably the apparent pressure is 0.1-0.5MPa, preferably containing 30-100% water vapor, more preferably containing 60-100% water vapor. 3. The preparation method according to claim 1, wherein the hydrothermal roasting treatment temperature is 350-500 DEG C, and the treatment time is 1.0-4.0 hours. 4. The method according to claim 1, wherein the acidic substance is selected from the group consisting of ammonium chloride, ammonium sulfate, ammonium carbonate, ammonium bicarbonate, ammonium phosphate, ammonium dihydrogen phosphate, diammonium hydrogen phosphate, hydrochloric acid, sulfuric acid, nitric acid A mixture of one or more of them. 5. The preparation method according to claim 1, wherein the alkaline substance comprises a mixture of one or more of ammonia water, a buffer solution of ammonia water and ammonium chloride. 6 . The preparation method according to claim 1 , wherein the weight ratio of the acid-containing deionized water to the molecular sieve is 1-20, preferably 6-15, more preferably 8-12. 7 . 7 . The preparation method according to claim 1 , wherein the acid-containing deionized water preferably has a pH value of 2-6, more preferably a pH value of 3-5. 8 . 8. According to the preparation method of claim 3, the acid-containing deionized water washing is carried out at a temperature of 30-100°C, preferably 60-80°C; the acid-containing deionized water washing is carried out for 1 -2 times. 9. The preparation method according to claim 1, wherein the alkali metal-containing molecular sieve is selected from one or more of FAU, MOR, and MFI structural molecular sieves. 10. The preparation method according to claim 1, wherein the alkali metal is selected from one or more of Na, K, Rb and Cs. 11. The preparation method according to claim 1, wherein, in the molecular sieve containing alkali metal, the content of alkali metal is 0.1-20% based on the weight of the molecular sieve containing alkali metal.