CN104512905B - A clean production method of Beta molecular sieve exchange process - Google Patents

Abstract

A kind of clean preparation method of Beta molecular sieve exchange process, it is characterized in that the method includes that the beta molecular sieve pulp by hydrothermal crystallizing synthesis obtains processes at 200～250 DEG C, make the step of template decomposed in molecular sieve pulp, and at room temperature, molecular sieve pulp is contacted with inorganic acid solution the step carrying out ion-exchange reactions.The method can effectively reduce Beta molecular sieve Na₂On the basis of O content and guarantee molecular sieve crystallinity, decrease the ammonia-nitrogen content in sewage significantly, reached the standard that sewage directly discharges, reach the purpose that molecular sieve cleaning produces.

Description

A clean production method of Beta molecular sieve exchange process

technical field

The invention relates to a method for exchanging Beta molecular sieves, and furthermore relates to a clean production method for reducing the Na ₂ O content of the molecular sieve, ensuring the crystallinity of the molecular sieve, and avoiding the discharge of high-ammonia nitrogen sewage.

Background technique

Beta molecular sieve was synthesized for the first time by the American Mobil Company in 1967 by the classic hydrothermal crystallization method (US3308069). Beta molecular sieve has a three-dimensional twelve-membered ring channel structure. Due to its unique topology and good thermal and hydrothermal stability, it is widely used in alkylation, hydrocracking, hydroisomerization, hydrofinishing, hydrocarbon cracking, etc. Exhibits excellent catalytic performance.

In the process of industrial production of Beta molecular sieves, Beta molecular sieve products contain a large amount of alkali metal ions, which need to be ion-exchanged before they can be used in acid-catalyzed reactions. The usual practice is to use inorganic ammonium salts to exchange Beta molecular sieves. One exchange process can reduce the Na ₂ O content in Beta molecular sieves to 2.5% by weight, and the yield of molecular sieves is 80-85% by weight; after 2-3 exchanges The process can reduce the Na ₂ O content in the Beta molecular sieve to less than 0.05% by weight, and the yield of the molecular sieve is 70-80% by weight. Therefore, the repeated ammonium exchange process caused the yield of molecular sieve to decrease significantly. At the same time, the use of inorganic ammonium salts produces a large amount of high ammonia nitrogen sewage. Sewage with high ammonia nitrogen cannot be discharged directly, and needs to be treated by a vacuum stripping deammonization device.

CN100404432C discloses a method for reducing ammonia nitrogen pollution in the molecular sieve exchange process: first, potassium compounds are used to exchange Na ⁺ in the molecular sieve, and then ammonium salts are used to further exchange K ⁺ in the molecular sieve. In this method, although the K ⁺ exchange ability is strong, Na ⁺ in the molecular sieve can be easily exchanged, but the exchange ability of NH ₄ ⁺ is weak, and it is difficult to exchange K ⁺ in the molecular sieve with ammonium salt. Moreover, this method still needs to be exchanged with ammonium salt, and there is still the problem of ammonia nitrogen pollution.

CN102079531A discloses a molecular sieve exchange method: the molecular sieve is contacted with an aqueous solution containing inorganic acids and organic acids at 0-5° C. for 0.5-3 hours, and then filtered and washed. In this method, the inorganic ammonium salt is replaced by an aqueous solution of an inorganic acid and an organic acid, which solves the problem of ammonia nitrogen pollution in the production process of the FCC catalyst from the source, and can ensure the exchange effect without destroying the structure of the molecular sieve. However, the ammonia nitrogen content in the sewage produced is still as high as 2000-2500 μg/L.

Contents of the invention

The inventors of the present invention unexpectedly discovered through a large number of experiments that when the organic template in the Beta molecular sieve hydrothermal synthesis slurry is partially decomposed at a certain temperature and combined with acid treatment, it can effectively reduce the Beta molecular sieve Na ₂ O content and ensure the crystallization of the molecular sieve Under the premise of high temperature, the content of ammonia nitrogen in sewage can be greatly reduced, and the purpose of clean production of molecular sieves can be achieved. Based on this, the present invention is formed.

The clean production method of the Beta molecular sieve exchange process provided by the present invention is characterized in that the method comprises the step of treating the beta molecular sieve slurry obtained by hydrothermal crystallization synthesis at 150-250°C to partially decompose the organic template agent in the molecular sieve slurry , and at room temperature, the step of contacting the molecular sieve slurry with an inorganic acid solution to carry out an ion exchange reaction.

In the method of the present invention, the preferred composition of said beta molecular sieve-containing slurry is represented by molar ratio: SiO ₂ /Al ₂ O ₃ =15-50, organic template/SiO ₂ =0.08-0.12, H ₂ O /SiO ₂ =6-8.

In the method of the present invention, said organic template is selected from tetraethylammonium hydroxide, tetraethylammonium chloride, tetraethylammonium bromide, tetraethylammonium iodide, tetrapropylammonium hydroxide One or more, wherein the more preferred organic template is tetraethylammonium hydroxide or tetrapropylammonium hydroxide.

In the step of decomposing part of the organic template agent, the amount of decomposition of the part of the organic template agent preferably accounts for 1.0 to 4.0% by weight of the total organic template dose, more preferably 1.2 to 3.0% by weight, and the degree of decomposition is determined by GB7478 -87 method to get.

In order to decompose part of the organic template in the beta molecular sieve-containing slurry, the method adopted may be to treat the beta molecular sieve-containing slurry at 150-230° C. for 0.5-8 hours. For example, when synthetic beta molecular sieves use tetraethylammonium hydroxide as an organic template, in the slurry containing beta molecular sieves, tetraethylammonium hydroxide will be decomposed into triethylamine at 150-230°C. The amount of tetraethylammonium hydroxide and the amount of ammonium brought out by triethylamine in the slurry (at 150-230°C is the stripping liquid) determined by the method of GB7478-87 Know and control the amount of tetraethylammonium hydroxide of decomposition. The inventors also unexpectedly found that when the temperature is in the upper range, such as 200-230°C, the BEA crystal structure of beta molecular sieve is easy to transform into the MOR crystal structure of mordenite (Comparative Examples 3 and 4). The molecular sieve slurry is treated at 160-180°C for 0.5-6 hours.

In the method of the present invention, said inorganic acid is selected from one or more of sulfuric acid, hydrochloric acid, nitric acid and phosphoric acid, preferably sulfuric acid or hydrochloric acid. The said inorganic acid has an acid concentration of 0.001-0.5 mol/L, preferably 0.002-0.01 mol/L, based on the concentration of contained H ⁺ . The present invention implements acidity through the step of contacting with inorganic acid solution, and the pickling can be exchanged with ammonium ions to balance the negative charge of the molecular sieve framework, and meanwhile, this step does not generate ammonia nitrogen wastewater.

In order to effectively reduce the content of Na ₂ O and maintain a higher relative crystallinity and discharge of wastewater with lower ammonia nitrogen, in a most preferred embodiment of the present invention, the hydrothermal crystallization synthesis of tetraethyl-containing The beta molecular sieve slurry with ammonium hydroxide as an organic template is treated at 160-180°C for 0.5-6 hours to decompose 1.2-2.0% by weight of tetraethylammonium hydroxide in the molecular sieve slurry, and then at room temperature, the molecular sieve slurry and acid The mineral acid solution with a concentration of 0.002-0.01mol/L is contacted to carry out ion exchange and recover the obtained product.

The clean production method of the Beta molecular sieve exchange process provided by the present invention also includes the steps of washing and drying the conventional filter cake with deionized water to obtain molecular sieve samples, etc., which are known to those skilled in the art and will not be repeated here.

_The method of the invention can effectively reduce the Na2O content in the Beta molecular sieve and ensure the crystallinity of the molecular sieve by partially decomposing the organic template agent and combining the exchange method of using inorganic acid instead of ammonium salt. At the same time, this clean production method greatly reduces the ammonia nitrogen content in the sewage, and the ammonia nitrogen content is below 50 μg/L, and the sewage can be treated without a vacuum stripping deammonification device to meet the requirement of direct discharge.

detailed description

The following examples will further illustrate the present invention, but do not limit the present invention thereby.

The molecular sieve raw materials used in the examples and comparative examples are all produced by Sinopec; the chemical reagents used are chemically pure unless otherwise specified. In comparative examples and examples, the amount of ammonium in the stripping liquid is measured by GB7478-87; the phase of molecular sieves is measured by X-ray powder diffraction (XRD), and the relative crystallinity is measured by _RIPP145-90 standard method; the Na2O content Determination by X-ray fluorescence spectrometry; determination of ammonia nitrogen in the filtrate by distillation-neutralization titration (HJ537-2009).

Comparative example 1

This comparative example illustrates a conventional ammonium salt exchange process.

Beta molecular sieves were synthesized according to the method provided by CN1154341A.

Add sodium metaaluminate solution (sodium oxide 145.8g/L, aluminum oxide 102.8g/L) and tetraethylammonium hydroxide (TEAOH, 2.417N, Guangzhou Dayou Fine Chemical Co., Ltd.) into deionized water, heat to dissolve, Stir evenly to make a working solution, mix coarse-pore silica gel (150-250μm, 500m2/g, 0.9ml/g, Qingdao Ocean Chemical Factory) with the above working solution, and make the surface of the silica gel wet with the working solution to obtain a reaction mixture , wherein the molar ratio of each component is SiO ₂ /Al ₂ O ₃ =30, Na ₂ O/SiO ₂ =0.075, TEAOH/SiO ₂ =0.09, H ₂ O/SiO ₂ =6.5. The reaction mixture was crystallized in an autoclave at 120° C. for 24 hours, then crystallized at 140° C. for 48 hours, and cooled to room temperature to obtain a Beta molecular sieve slurry.

Stir and mix the above-mentioned Beta molecular sieve slurry (the same below) with ammonium chloride and water according to the weight ratio of Beta (dry basis):NH ₄ Cl:H ₂ O=1:0.3:10, raise the temperature to 80°C and stir for 2 hours, Then filter and collect the filtrate. The ammonia nitrogen content is shown in Table 1; the filter cake was rinsed with deionized water and dried to obtain a conventional ammonium-exchanged Beta molecular sieve, which was denoted as DB1. See Table 1 for the sample phase, relative crystallinity, Na ₂ O content, and ammonia nitrogen content in the filtrate.

Comparative example 2

This comparative example illustrates conventional ammonium salt exchange and pickling procedures.

Using the conventional Beta molecular sieve ammonium salt exchange method, stir and mix the Beta molecular sieve slurry with ammonium chloride and water according to the weight ratio of Beta (dry basis): NH ₄ Cl: H ₂ O = 1:1:20, and adjust the pH of the slurry with dilute hydrochloric acid value was 3.0, the temperature was raised to 80° C. and stirred for 2 hours, then filtered, and the filtrate was collected. The ammonia nitrogen content is shown in Table 1. The filter cake was rinsed with deionized water and dried to obtain a conventional ammonium-exchanged Beta molecular sieve, denoted as DB2. See Table 1 for the sample phase, relative crystallinity, Na ₂ O content, and ammonia nitrogen content in the filtrate.

Example 1

Measure 50ml of the Beta molecular sieve slurry, add 150ml of water and stir evenly, heat up the molecular sieve slurry at 180°C for 0.5h, at this time, 1.25% by weight of tetraethylammonium hydroxide is decomposed. Then at room temperature, under the situation of continuous stirring, adding concentration is 7.84g of sulfuric acid of 2wt%, and the acid concentration of measuring mixed slurry is 0.008mol/L, slurry is filtered, and filtrate is collected, and its ammonia nitrogen content is shown in Table 1; Filter cake Wash and dry with deionized water to obtain a molecular sieve sample exchanged once, denoted as B1. See Table 1 for the sample phase, relative crystallinity, Na ₂ O content, and ammonia nitrogen content in the filtrate.

Example 2

Measure 50ml of the Beta molecular sieve slurry, add 150ml of water and stir evenly. The temperature of the molecular sieve slurry is raised at 170°C and kept for 1 hour. At this time, 1.43% by weight of tetraethylammonium hydroxide is decomposed. Then at room temperature, under the situation of continuous stirring, add the sulfuric acid 10g that concentration is 2wt%, measure the acid concentration of mixed slurry to be 0.0096mol/L, slurry filter, collect filtrate, its ammonia nitrogen content is shown in Table 1; Wash with deionized water and dry to obtain a molecular sieve sample exchanged once, denoted as B2. See Table 1 for the sample phase, relative crystallinity, Na ₂ O content, and ammonia nitrogen content in the filtrate.

Example 3

Measure 80ml of the Beta molecular sieve slurry, add 210ml of water and stir evenly. The temperature of the molecular sieve slurry is raised at 160°C and kept for 2 hours. At this time, 1.67% by weight of tetraethylammonium hydroxide is decomposed. Then at room temperature, under the situation of continuous stirring, adding concentration is 1.2g of hydrochloric acid of 5wt%, and the acid concentration of measuring mixed slurry is 0.0020mol/L, slurry is filtered, and filtrate is collected, and its ammonia nitrogen content is shown in Table 1; filter cake Wash and dry with deionized water to obtain a molecular sieve sample exchanged once, denoted as B3. See Table 1 for the sample phase, relative crystallinity, Na ₂ O content, and ammonia nitrogen content in the filtrate.

Example 4

Measure 80ml of the Beta molecular sieve slurry, add 210ml of water and stir evenly. The temperature of the molecular sieve slurry is raised at 160°C and kept for 6 hours. At this time, 1.72% by weight of tetraethylammonium hydroxide is decomposed. Then at room temperature, under the situation of continuous stirring, adding concentration is 2.37g of hydrochloric acid of 7wt%, and the acid concentration of measuring mixed slurry is 0.0055mol/L, and the slurry is filtered, and the filtrate is collected, and its ammonia nitrogen content is shown in Table 1; filter cake Wash and dry with deionized water to obtain a molecular sieve sample exchanged once, which is denoted as B4. See Table 1 for the sample phase, relative crystallinity, Na ₂ O content, and ammonia nitrogen content in the filtrate.

Example 5

Measure 80ml of the Beta molecular sieve slurry, add 210ml of water and stir evenly. The temperature of the molecular sieve slurry is raised at 160°C and kept for 6 hours. At this time, 1.67% by weight of tetraethylammonium hydroxide is decomposed. Then at room temperature, under the situation of continuous stirring, adding concentration is 60g of hydrochloric acid of 7wt%, and the acid concentration of measuring mixed slurry is 0.12mol/L, and the slurry is filtered, and the filtrate is collected, and its ammonia nitrogen content is shown in Table 1; Wash with deionized water and dry to obtain a molecular sieve sample exchanged once, denoted as B5. See Table 1 for the sample phase, relative crystallinity, Na ₂ O content, and ammonia nitrogen content in the filtrate.

Example 6

Measure 80ml of the Beta molecular sieve slurry, add 210ml of water and stir evenly. The temperature of the molecular sieve slurry is raised at 160°C and kept for 6 hours. At this time, 1.67% by weight of tetraethylammonium hydroxide is decomposed. Then at room temperature, under the situation of continuous stirring, adding concentration is 180g of hydrochloric acid of 7wt%, and the acid concentration of measuring mixed slurry is 0.3mol/L, and the slurry is filtered, and the filtrate is collected, and its ammonia nitrogen content is shown in Table 1; Wash with deionized water and dry to obtain a molecular sieve sample exchanged once, denoted as B6. See Table 1 for the sample phase, relative crystallinity, Na ₂ O content, and ammonia nitrogen content in the filtrate.

Comparative example 3

Measure 80ml of the Beta molecular sieve slurry, add 210ml of water and stir evenly. The temperature of the molecular sieve slurry is kept at 200°C for 4 hours. At this time, 10.2% by weight of tetraethylammonium hydroxide is decomposed. Then at room temperature, under the situation of continuous stirring, adding concentration is 2.37g of hydrochloric acid of 7wt%, and measuring the acid concentration of mixed slurry is 0.0055mol/L; The molecular sieve sample is denoted as DB3. See Table 1 for the sample phase, relative crystallinity, Na ₂ O content, and ammonia nitrogen content in the filtrate.

Comparative example 4

Measure 80ml of the Beta molecular sieve slurry, add 210ml of water and stir evenly. The temperature of the molecular sieve slurry is kept at 230°C for 2 hours. At this time, 13.2% by weight of tetraethylammonium hydroxide is decomposed, and then at room temperature, under the condition of continuous stirring, add concentration It was 2.37g of 7wt% hydrochloric acid, and the acid concentration of the mixed slurry was measured to be 0.0055mol/L; the filter cake was washed with deionized water and dried to obtain a molecular sieve sample exchanged once, which was recorded as DB4. Its properties are shown in Table 1.

Table 1

Sample serial number Phase Relative crystallinity% Na ₂ O weight % Ammonia nitrogen content in filtrate μg/L DB1 Beta 100 0.35 2250.8 DB2 Beta 102 0.31 2346.7 B1 Beta 101 0.12 35.6 B2 Beta 104 0.07 19.6 B3 Beta 102 0.14 12.8 B4 Beta 102 0.04 20.4 B5 Beta 90 0.04 20.0 B6 Beta 83 0.03 18.3 DB3 MOR / / / DB4 MOR / / /

It can be seen from Table 1 that the method provided by the present invention can achieve the same degree of Na ₂ O exchange as conventional ammonium exchange, and the crystallinity can be slightly improved, which meets the requirements of industrial production. At the same time, the content of ammonia nitrogen in the filtrate of this method is between 12.8 and 35.6 μg/L (samples B1 to B6), which is far lower than the conventional ammonium exchange method (comparative example 1) or the combined method of ammonium exchange and acid treatment (comparative example 2) The content level of ammonia nitrogen in the filtrate>2000μg/L basically realizes the zero ammonia nitrogen discharge of sewage and achieves the purpose of clean production.

It can also be seen from Table 1 that when the slurry treatment temperature is in the upper range such as 200 and 230°C (comparative example 3 and comparative example 4, DB3 and DB4 samples), the phase of beta molecular sieve will be transformed into the MOR of mordenite Crystal structure.

Claims (11)

1. A clean production method for a Beta molecular sieve exchange process, characterized in that the method comprises the step of processing the beta molecular sieve slurry obtained by hydrothermal crystallization synthesis at 150 to 250°C to partially decompose the organic template in the molecular sieve slurry , and at room temperature, the step of contacting the molecular sieve slurry with an inorganic acid solution to carry out an ion exchange reaction, wherein the organic template is partially decomposed, and the proportion of the partial decomposition is 1.0-4.0% by weight. 2. according to the method for claim 1, wherein, said beta molecular sieve slurry, its composition is represented by molar ratio: SiO ₂ /Al ₂ O ₃ =15～50, organic templating agent/SiO ₂ =0.08～0.12, H ₂ O/SiO ₂ =6-8. 3. according to the method for claim 1 or 2, wherein, said organic templating agent is selected from tetraethylammonium hydroxide, tetraethylammonium chloride, tetraethylammonium bromide, tetraethylammonium iodide and tetraethylammonium iodide One or more of propyl ammonium hydroxide. 4. according to the method for claim 1 or 2, wherein, said organic templating agent is tetraethyl ammonium hydroxide or tetrapropyl ammonium hydroxide. 5. The method according to claim 1, wherein said organic template is partially decomposed, and the proportion of the partial decomposition is 1.2-3.0% by weight. 6. The method according to claim 1 or 5, wherein said organic template is partially decomposed by treating the beta molecular sieve slurry at 150-230° C. for 0.5-8 hours. 7. The method according to claim 1 or 5, wherein said organic template is partially decomposed by treating the beta molecular sieve slurry at 160-180°C for 0.5-6h. 8. according to the method for claim 1, wherein, said inorganic acid is selected from one or more of sulfuric acid, hydrochloric acid, nitric acid and phosphoric acid. 9. The method according to claim 1 or 8, wherein said inorganic acid has an acid concentration of 0.001 to 0.5 mol/L based on the concentration of H ⁺ contained therein. 10. The method according to claim 9, wherein said acid concentration is 0.002-0.012 mol/L. 11. according to the method for claim 1, it is characterized in that the method is that the beta molecular sieve slurry containing tetraethylammonium hydroxide synthesized by hydrothermal crystallization is the organic template agent at 160～180 ℃ for 0.5～6h, make Tetraethylammonium hydroxide in the molecular sieve slurry is decomposed by 1.2-2.0% by weight, and then at room temperature, the molecular sieve slurry is contacted with an inorganic acid solution with an acid concentration of 0.002-0.01mol/L to carry out ion exchange and recover the obtained product.