Preparation method of Y-type molecular sieve with high rare earth utilization

Abstract

The present invention discloses a method for preparing a Y-type molecular sieve with high rare earth utilization, comprising the following steps: step 1: preparing a NaY molecular sieve slurry using a working solution to obtain a first slurry; step 2: performing ion exchange on a rare earth salt solution and an inorganic acid added to the first slurry to obtain a second slurry; step 3: transferring the second slurry to a filter, adding the rare earth salt solution to perform belt ion exchange to obtain a first filter cake, washing the first filter cake with water, filtering it, flash drying it, roasting it, and then adding water to obtain a third slurry; step 4: transferring the third slurry to a secondary exchange tank, adding the working solution and an inorganic acid to perform ion exchange to obtain a fourth slurry; step 5: transferring the fourth slurry to a filter, adding the rare earth salt solution to perform belt ion exchange to obtain a second filter cake, washing the second filter cake with water, filtering it, and beating it to obtain a Y-type molecular sieve with high rare earth utilization. The method of the present invention is highly environmentally friendly, clean and efficient, and has a convenient process.

Description

Technical Field

[0001] The invention belongs to the technical field of preparation of Y molecular sieves, and particularly relates to a method for preparing a Y-type molecular sieve with high rare earth utilization. Background Art

[0002] Rare earths are non-renewable resources. Current conventional molecular sieve production technology results in a portion of rare earths being lost into the filtrate after the exchange of rare earth ions between NaY molecular sieves and rare earth ions, resulting in a rare earth utilization rate of less than 70%, resulting in significant waste of rare earths. Therefore, increasing the rare earth ion exchange capacity and utilization rate of Y-type molecular sieves is an important approach to reducing costs and increasing efficiency in molecular sieve production. By increasing the rare earth utilization rate during the Y-type molecular sieve exchange process, reducing the amount of rare earth feed, and precisely controlling the slurry concentration at each rare earth exchange step, exchange efficiency can be guaranteed and the discharge of rare earth-containing wastewater can be reduced. This is also a key energy-saving and emission-reduction measure for molecular sieve manufacturers.

[0003] CN113318777A discloses a method for preparing a catalytic cracking catalyst containing a rare earth Y-type molecular sieve. The method comprises: partially exchanging a NaY molecular sieve with an ammonium salt to remove sodium ions, filtering, washing, and drying to obtain an NH4NaY molecular sieve; then contacting the NH4NaY molecular sieve with a rare earth salt solution or a mixed solution of a rare earth salt solution and an ammonium salt, filtering, washing, and drying to obtain a rare earth NaY molecular sieve; and hydrothermally calcining the obtained rare earth NaY molecular sieve under an atmosphere of externally applied pressure and externally added water. The method uses any one or a mixture of ammonium chloride, ammonium nitrate, ammonium carbonate, and ammonium bicarbonate, resulting in the discharge of ammonia nitrogen wastewater, and the inorganic oxides used introduce impurities such as silicon and aluminum.

[0004] CN100344374C discloses a rare earth Y molecular sieve and a preparation method thereof. This method uses ammonia water and water glass alkaline solution to adjust the slurry pH to 8-11. The production and preparation conditions are strict, resulting in a high ammonia nitrogen content in the wastewater, which puts pressure on subsequent wastewater disposal.

[0005] CN103508467A discloses a method for preparing rare earth Y molecular sieves. This involves treating NaY molecular sieves with a mixed solution of a rare earth solution and an ammonium salt to produce a rare earth sodium Y molecular sieve. The rare earth sodium Y molecular sieve is then slurried and contacted with an ammonium salt solution, treated without filtration, and the slurry pH is adjusted using an alkaline liquid such as ammonia, water glass, sodium metaaluminate, or sodium hydroxide to deposit rare earths. This slurry is then calcined twice to produce a rare earth Y molecular sieve with a framework silicon-to-aluminum ratio of 2.5-5.0 and a crystallinity of 35%-65%. This process requires two calcinations and involves the repeated use of ammonia and other alkaline reagents, resulting in high ammonia nitrogen wastewater treatment pressure and the introduction of other ionic impurities.

[0006] Currently, the industrial production of rare earth Y molecular sieves often involves adding ammonium salts for sodium exchange treatment, or adding alkali solution to adjust the slurry's alkaline pH before precipitation and calcination to improve rare earth utilization. This increases costs and energy consumption for manufacturers, hindering energy conservation and environmental protection requirements, and creating challenges for long-term development. Summary of the Invention

[0007] The purpose of the present invention is to provide a method for preparing a Y-type molecular sieve with high rare earth utilization, which solves the problems existing in the current preparation of high rare earth Y-type molecular sieves, such as low rare earth utilization, generation of high ammonia nitrogen wastewater during the preparation process, and inconvenient preparation process.

[0008] The technical solution adopted by the present invention is:

[0009] The preparation method of Y-type molecular sieve with high rare earth utilization rate is specifically carried out according to the following steps:

[0010] Step 1: The qualified NaY molecular sieve slurry after washing is prepared into a first slurry with a solid content of 100-350 g / L using a working solution;

[0011] Step 2: adding a rare earth salt solution to the first slurry at a weight ratio of 0.01-0.5 of NaY dry basis to RE2O3, then adding an inorganic acid to adjust the pH of the first slurry to 3-6.5, and then performing ion exchange at a temperature of 10-100°C to obtain a second slurry;

[0012] Step 3: The second slurry is transferred to a filter for filtration, and then a low concentration rare earth salt solution is added at a weight ratio of 0.01-0.2 of NaY dry basis RE2O3 to perform belt ion exchange to obtain a first filter cake, which is then washed and filtered, then flash dried at a temperature of 115-145°C, and finally calcined at a temperature of 585-615°C for 2-3 hours, and water is added to obtain a third slurry;

[0013] Step 4: The third slurry is transferred to a secondary exchange tank, and the working solution is used to prepare the third slurry to a solid content of 150-250 g / L, and then an inorganic acid is added to adjust the pH of the third slurry to 3.0-6.5, and ion exchange is performed at a temperature of 10-100° C. to obtain a fourth slurry;

[0014] Step 5: The fourth slurry is transported to a filter for filtration, and then a low concentration rare earth salt solution is added according to a weight ratio of 0.01-0.06 of NaY dry basis RE2O3 for belt ion exchange to obtain a second filter cake, the second filter cake is washed and filtered, and the filter cake is then slurried to obtain a Y-type molecular sieve with high rare earth utilization.

[0015] The present invention is also characterized in that:

[0016] In step 1, a qualified NaY molecular sieve slurry is washed with water, wherein the relative crystallinity is ≥83%, the silicon-aluminum ratio is ≥4.80, and the pH is ≤11.

[0017] In step 1 and step 4, the working solution is a mixture of three solutions: the filtrate after filtering the second slurry, the unreacted rare earth-carrying solution, and the filtrate produced after washing the filter cake, wherein the RE2O3 content is 1.5-2.5g / L and the molecular sieve concentration is 20-80g / L.

[0018] In step 2, the rare earth salt solution refers to a rare earth chloride solution or a rare earth nitrate solution having a RE2O3 content of 290-310 g / L.

[0019] 5 . The method for preparing a Y-type molecular sieve with high rare earth utilization according to claim 1 , wherein in step 2 and step 4 , the inorganic acid can be hydrochloric acid or nitric acid with a mass fraction of 10-20%.

[0020] In step 3 and step 5, the low-concentration rare earth salt solution is a rare earth chloride solution or a rare earth nitrate solution with a RE2O3 content of 20-40 g / L.

[0021] In step 3, washing with water specifically comprises: using five times the amount of water as the base amount of the filter biscuits for washing.

[0022] The beneficial effects of the present invention are as follows: the present invention has a method for preparing a Y-type molecular sieve with high rare earth utilization, wherein the solid sodium-rare earth liquid phase equilibrium is broken by suction filtration, and then rare earth exchange is performed. The resulting rare earth Y molecular sieve product has special physical and chemical properties, and its rare earth utilization rate and molecular sieve structural stability are superior to those of the prior art. In particular, it is found in a large amount of production data and experiments that this process does not use an ammonium salt solution for sodium reduction exchange, does not use alkaline solutions such as ammonia water, water glass, sodium metaaluminate, and sodium hydroxide to adjust the pH value, does not introduce other impurity ions into the production system, and does not cause ammonia nitrogen wastewater disposal pressure. The process of this method is clean and efficient, the process is short, the cost is low, and the rare earth utilization rate is high, and the product quality is good. DETAILED DESCRIPTION

[0023] The preparation method of the Y-type molecular sieve with high rare earth utilization rate of the present invention is described in detail below in conjunction with specific embodiments.

[0024] The present invention provides a method for preparing a Y-type molecular sieve with high rare earth utilization. The rare earth content in the prepared Y-type molecular sieve can be arbitrarily adjusted in terms of rare earth oxide, and the utilization rate of the rare earth is improved to a certain extent. The preparation process of the Y-type molecular sieve does not use an exchange medium such as ammonium salt or ammonia water for sodium reduction operation. The preparation process is relatively clean and efficient, and does not cause high ammonia nitrogen wastewater discharge in the production system. It is a short-process preparation method suitable for hydrothermal ultra-stable method to improve the utilization rate of molecular sieve rare earth.

[0025] The preparation method of the Y-type molecular sieve with high rare earth utilization rate of the present invention is further described in detail below through specific examples.

[0026] Example 1;

[0027] A NaY molecular sieve slurry with a crystallinity of 86%, a silicon-aluminum ratio of 5.12, and a pH of 10.8 was prepared using a working solution with a RE2O3 content of 2.4 g / L and a molecular sieve concentration of 58 g / L to prepare a first slurry with a solid content of 180 g / L;

[0028] A rare earth salt solution having a RE2O3 content of 292 g / L was added to the first slurry at a weight ratio of NaY dry basis to RE2O3 of 0.08, and then 15% inorganic acid was added to adjust the pH to 3.6. Then, ion exchange was performed at a temperature of 60°C to obtain a second slurry;

[0029] The second slurry was transferred to a filter for filtration, and then a low-concentration rare earth salt solution with a RE2O3 content of 38 g / L was added at a weight ratio of NaY dry basis to RE2O3 of 0.06 to perform belt ion exchange to obtain a first filter cake. The first filter cake was washed with water 5 times and filtered, and then flash dried at 132°C. Finally, it was calcined at 598°C for 2.5 hours and water was added to obtain a third slurry.

[0030] The third slurry was transferred to a secondary exchange tank, and a working solution with a RE2O3 content of 2.2 g / L and a molecular sieve concentration of 49 g / L was used to adjust the solid content to 180 g / L, and then 15% inorganic acid was added to adjust the pH to 3.2. Ion exchange was performed at a temperature of 60°C to obtain a fourth slurry;

[0031] The fourth slurry is conveyed to a filter for filtration, and then a low-concentration rare earth salt solution with a RE2O3 content of 38 g / L is added according to a weight ratio of 0.06 for dry basis RE2O3 of NaY to perform belt ion exchange to obtain a second filter cake. The second filter cake is washed with water and filtered, and then the filter cake is slurried to obtain a Y-type molecular sieve with a high rare earth utilization rate, a rare earth feed ratio of 16.5% of product oxide rare earth, and a rare earth utilization rate of 99%.

[0032] Example 2;

[0033] A NaY molecular sieve slurry with a crystallinity of 83%, a silicon-aluminum ratio of 5.10, and a pH of 12 was prepared using a working solution with a RE2O3 content of 2.0 g / L and a molecular sieve concentration of 49 g / L to prepare a first slurry with a solid content of 200 g / L;

[0034] A rare earth salt solution having a RE2O3 content of 295 g / L was added to the first slurry at a weight ratio of NaY dry basis to RE2O3 of 0.06, and then 15% inorganic acid was added to adjust the pH to 3.2. Then, ion exchange was performed at a temperature of 60°C to obtain a second slurry;

[0035] The second slurry was transferred to a filter for filtration, and then a low-concentration rare earth salt solution with a RE2O3 content of 38 g / L was added at a weight ratio of NaY dry basis: RE2O3 of 0.04 to perform belt ion exchange to obtain a first filter cake. The first filter cake was washed with water 5 times and filtered, and then flash dried at 120°C. Finally, it was calcined at 601°C for 2.2 hours, and water was added to obtain a third slurry.

[0036] The third slurry was transferred to a secondary exchange tank, and a working solution with a RE2O3 content of 2.0 g / L and a molecular sieve concentration of 49 g / L was used to adjust the solid content to 200 g / L, and then 15% inorganic acid was added to adjust the pH to 3.4. Ion exchange was performed at a temperature of 60°C to obtain a fourth slurry;

[0037] The fourth slurry is conveyed to a filter for filtration, and then a low-concentration rare earth salt solution with a RE2O3 content of 38 g / L is added according to a weight ratio of 0.03 of RE2O3 on a dry basis of NaY to obtain a second filter cake. The second filter cake is washed with water and filtered, and then the filter cake is slurried to obtain a Y-type molecular sieve with a high rare earth utilization rate, a rare earth feed ratio of 11.1% of product oxide rare earth, and a rare earth utilization rate of 96.5%.

[0038] Example 3;

[0039] A NaY molecular sieve slurry with a crystallinity of 83%, a silicon-aluminum ratio of 5.10, and a pH of 12 was prepared using a working solution with a RE2O3 content of 1.8 g / L and a molecular sieve concentration of 49 g / L to prepare a first slurry with a solid content of 250 g / L;

[0040] A rare earth salt solution having a RE2O3 content of 295 g / L was added to the first slurry at a weight ratio of NaY dry basis to RE2O3 of 0.08, and then 15% inorganic acid was added to adjust the pH to 3.2. Then, ion exchange was performed at room temperature to obtain a second slurry;

[0041] The second slurry was transferred to a filter for filtration, and then a low-concentration rare earth salt solution with a RE2O3 content of 35 g / L was added at a weight ratio of NaY dry basis to RE2O3 of 0.04 to perform belt ion exchange to obtain a first filter cake. The first filter cake was washed with water 5 times and filtered, and then flash dried at 120°C. Finally, it was calcined at 610°C for 2 hours, and water was added to obtain a third slurry.

[0042] The third slurry was transferred to a secondary exchange tank, and a working solution with a RE2O3 content of 1.8 g / L and a molecular sieve concentration of 49 g / L was used to adjust the solid content to 250 g / L, and then 15% inorganic acid was added to adjust the pH to 3.4. Ion exchange was performed at room temperature to obtain a fourth slurry;

[0043] The fourth slurry is conveyed to a filter for filtration, and then a low-concentration rare earth salt solution with a RE2O3 content of 35 g / L is added according to a weight ratio of 0.04 for dry basis RE2O3 of NaY to perform belt ion exchange to obtain a second filter cake. The second filter cake is washed with water and filtered, and then the filter cake is slurried to obtain a Y-type molecular sieve with a high rare earth utilization rate, a rare earth feed ratio of 13.4% for product oxide rare earth, and a rare earth utilization rate of 97%.

[0044] Example 4;

[0045] A NaY molecular sieve slurry with a crystallinity of 83%, a silicon-aluminum ratio of 5.10, and a pH of 12 was prepared using a working solution with a RE2O3 content of 2.1 g / L and a molecular sieve concentration of 52 g / L to prepare a first slurry with a solid content of 280 g / L;

[0046] A rare earth salt solution having a RE2O3 content of 301 g / L was added to the first slurry at a weight ratio of NaY dry basis to RE2O3 of 0.06, and then 15% inorganic acid was added to adjust the pH to 3.0. Then, ion exchange was performed at 65°C to obtain a second slurry;

[0047] The second slurry was transferred to a filter for filtration, and then a low-concentration rare earth salt solution with a RE2O3 content of 40 g / L was added at a weight ratio of NaY dry basis to RE2O3 of 0.06 to perform belt ion exchange to obtain a first filter cake. The first filter cake was washed with water 5 times and filtered, and then flash dried at 120°C. Finally, it was calcined at 605°C for 2.3 hours, and water was added to obtain a third slurry.

[0048] The third slurry was transferred to a secondary exchange tank, and a working solution with a RE2O3 content of 2.1 g / L and a molecular sieve concentration of 52 g / L was used to adjust the solid content to 280 g / L, and then 15% inorganic acid was added to adjust the pH to 3.3. Ion exchange was performed at room temperature to obtain a fourth slurry;

[0049] The fourth slurry is conveyed to a filter for filtration, and then a low-concentration rare earth salt solution with a RE2O3 content of 40 g / L is added according to a weight ratio of 0.06 for dry basis RE2O3 of NaY to perform belt ion exchange to obtain a second filter cake. The second filter cake is washed with water and filtered, and then the filter cake is slurried to obtain a Y-type molecular sieve with a high rare earth utilization rate, a rare earth feed ratio of 14.9% of product oxide rare earth, and a rare earth utilization rate of 98%.

[0050] The present invention discloses a method for preparing a Y-type molecular sieve with high rare earth utilization. The method can realize flexible adjustment of rare earth content during the preparation process. The preparation process does not use ammonium salt or ammonia water for sodium reduction operation, does not introduce ammonia nitrogen components, and does not generate ammonia nitrogen wastewater. The generated filtrate can be directly discharged after sedimentation treatment. The preparation method is highly environmentally friendly, the preparation process is clean and efficient, the process is relatively more convenient, and has certain practical significance.

Claims

1. A method for preparing a Y-type molecular sieve with high rare earth utilization, characterized in that: Follow these steps: Step 1: The qualified NaY molecular sieve slurry after washing is prepared into a first slurry with a solid content of 100-350 g / L using a working solution; Step 2: adding a rare earth salt solution to the first slurry at a weight ratio of 0.01-0.5 of NaY dry basis to RE2O3, then adding an inorganic acid to adjust the pH of the first slurry to 3-6.5, and then performing ion exchange at a temperature of 10-100°C to obtain a second slurry; Step 3: The second slurry is transferred to a filter for filtration, and then a low concentration rare earth salt solution is added at a weight ratio of 0.01-0.2 of NaY dry basis RE2O3 to perform belt ion exchange to obtain a first filter cake, which is then washed and filtered, then flash dried at a temperature of 115-145°C, and finally calcined at a temperature of 585-615°C for 2-3 hours, and water is added to obtain a third slurry; Step 4: The third slurry is transferred to a secondary exchange tank, and the working solution is used to prepare the third slurry to a solid content of 150-250 g / L, and then an inorganic acid is added to adjust the pH of the third slurry to 3.0-6.5, and ion exchange is performed at a temperature of 10-100° C. to obtain a fourth slurry; Step 5: The fourth slurry is transported to a filter for filtration, and then a low concentration rare earth salt solution is added according to a weight ratio of 0.01-0.06 of NaY dry basis RE2O3 to perform belt ion exchange to obtain a second filter cake, the second filter cake is washed with water and filtered, and the filter cake is then slurried to obtain a Y-type molecular sieve with high rare earth utilization; In step 1, a qualified NaY molecular sieve slurry is washed with water, wherein the relative crystallinity is ≥83%, the silicon-aluminum ratio is ≥4.80, and the pH is ≤11; In step 1 and step 4, the working solution is a mixture of three solutions: the filtrate after filtering the second slurry, the unreacted rare earth-carrying solution, and the filtrate produced after washing the filter cake, wherein the content of RE2O3 is 1.5-2.5g / L and the molecular sieve concentration is 20-80g / L.

2. The method for preparing a Y-type molecular sieve with high rare earth utilization according to claim 1, characterized in that: In step 2, the rare earth salt solution refers to a rare earth chloride solution or a rare earth nitrate solution with a RE2O3 content of 290-310 g / L.

3. The method for preparing a Y-type molecular sieve with high rare earth utilization according to claim 1, characterized in that: In step 2 and step 4, the inorganic acid may be hydrochloric acid or nitric acid with a mass fraction of 10-20%.

4. The method for preparing a Y-type molecular sieve with high rare earth utilization according to claim 1, characterized in that: In step 3 and step 5, the low-concentration rare earth salt solution is a rare earth chloride solution or a rare earth nitrate solution with a RE2O3 content of 20-40 g / L.

5. The method for preparing a Y-type molecular sieve with high rare earth utilization according to claim 1, characterized in that: In step 3, washing with water specifically comprises: using five times the amount of water as the base amount of the filter biscuits for washing.