Low-sodium high-crystallinity Y-type molecular sieve and preparation method thereof

Abstract

The invention provides a low-sodium high-crystallinity Y-type molecular sieve and a preparation method thereof. The preparation method comprises the following steps: mixing and pulping a NaY molecular sieve, a first inorganic salt and water to form slurry, adding an acidic buffer solution to form a first solution, adjusting the pH value of the first solution to 3.8-4.0, and carrying out ion exchange, filtration, washing and wet baking to obtain an intermediate molecular sieve; and mixing and pulping the intermediate molecular sieve, a second inorganic salt and water to form a slurry, adding an alkaline buffer solution to form a second solution, adjusting the pH value of the second solution to 10.5-12, and carrying out ion exchange, slurry filtration, water washing and wet baking in a pressurized environment to obtain the low-sodium high-crystallinity Y molecular sieve. The invention also provides the low-sodium high-crystallinity Y-type molecular sieve prepared by the preparation method. The preparation method can effectively reduce the sodium content of the molecular sieve and prevent the crystallinity of the molecular sieve from being damaged.

Description

Technical Field

[0001] This invention relates to a Y-type molecular sieve, and more particularly to a low-sodium, high-crystallinity Y-type molecular sieve and its preparation method. Background Technology

[0002] Y-type zeolite is one of the main types used as catalysts and adsorption / separation agents in the petroleum catalytic cracking industry. Due to its high activity and good stability, Y-type zeolite catalysts have greatly changed the landscape of the entire catalytic cracking industry. Y-type molecular sieves are synthesized in a sodium-containing aluminosilicate crystallization system, initially exhibiting a stable NaY morphology. This is because the negative charge carried by the aluminum-oxygen tetrahedra is completely absorbed by the Na... + The positive charge it carries is neutralized, so NaY molecular sieves themselves are not acidic. To obtain the acidity required for the catalytic reaction, sodium must be removed from the molecular sieve. Another reason for sodium removal is that sodium has a significant toxic effect on the activity and hydrothermal stability of the molecular sieve.

[0003] Traditional Na + The current exchange method involves a "two-exchange, two-calcination" process. To meet the requirements for catalyst use, the catalyst microspheres need to be washed to reduce sodium content. NaY molecular sieve, ammonium salt, and water are mixed in a certain ratio and slurried. The pH is adjusted to acidity, and the temperature is controlled at 65-95℃. After exchange for 0.5-2 hours, high-temperature calcination (550-800℃) is performed. Under these conditions, migrating sodium ions can damage the crystal structure, reducing the crystallinity of the molecular sieve and leading to a decrease in specific surface area, thus affecting the catalytic performance of the molecular sieve. Furthermore, CN101633507A discloses a solid-phase ammonium exchange method, in which NaY molecular sieve and ammonium salt are mixed at a weight ratio of molecular sieve:ammonium salt = 1:(0.1-1.0), heated and held for 1 hour, and then washed once with water to obtain the ammonium-exchanged molecular sieve. Although this method reduces the amount of ammonium salt and water used, the sodium content in the product is still above 2%.

[0004] Therefore, there is a need for a method that can effectively reduce the sodium content in molecular sieves while preserving the crystal structure. Summary of the Invention

[0005] To address the aforementioned problems, the present invention aims to provide a low-sodium, high-crystallinity Y-type molecular sieve, its preparation method, and its applications. The Y-type molecular sieve of the present invention is a low-sodium, high-crystallinity Y-type molecular sieve, and its preparation method can reduce the Na content of the Y-type molecular sieve while avoiding damage to its crystallinity.

[0006] To achieve the above objectives, the present invention provides a method for preparing a low-sodium, high-crystallinity Y-type molecular sieve, the method comprising:

[0007] (1) Mix NaY molecular sieve with a first inorganic salt and water to form a slurry. Add an acidic buffer solution to the slurry to form a first solution. Adjust the pH of the first solution to 3.8-4.0 and carry out ion exchange. After the exchange is completed, filter, wash with water, and wet roast to obtain an intermediate molecular sieve.

[0008] (2) Mix the intermediate molecular sieve with the second inorganic salt and water to form a slurry. Add an alkaline buffer solution to the slurry to form a second solution. Adjust the pH of the second solution to 10.5-12.0. Perform ion exchange in a pressurized environment. After the exchange is completed, filter, wash with water, and wet roast to obtain a low-sodium, high-crystallinity Y molecular sieve.

[0009] The alkaline buffer solution includes phosphate buffer (PBS) and / or sodium carbamate buffer (CHES).

[0010] According to the specific implementation plan, the first inorganic salt and the second inorganic salt generally contain ammonium ions. By exchanging ammonium ions with sodium ions, the sodium ion content in the molecular sieve can be reduced.

[0011] According to the specific implementation plan, in step (1), the first inorganic salt may include a soluble ammonium salt, specifically including one or more of the following: ammonium sulfate, ammonium chloride, ammonium nitrate, ammonium acetate, ammonium phosphate, etc.

[0012] According to the specific implementation plan, in step (1), the weight ratio of the NaY molecular sieve to the first inorganic salt and water can be controlled as 1:(0.1-0.3):(5-8).

[0013] According to the specific implementation plan, the present invention does not impose any special restrictions on parameters such as the silicon-to-aluminum ratio of NaY molecular sieves, and all existing NaY molecular sieves can be used in the technical solutions of the present invention.

[0014] According to the specific implementation plan, step (1) involves the first ion exchange, but the exchange of ammonium ions with sodium ions will damage the internal structure of the molecular sieve. This invention improves the freedom of ammonium ions by controlling the pH within a certain range, and ensures that the molecular sieve structure is not significantly damaged while sodium ions are exchanged out; in addition, the addition of an acidic buffer reagent can also alleviate the structural damage of the molecular sieve caused by the acidic environment, while improving the degree of sodium removal.

[0015] According to the specific implementation plan, in step (1), the acidic buffer solution includes a combination of organic acid and ammonium organic acid, specifically a combination of organic acid and ammonium salt of the organic acid.

[0016] In some specific implementations, in step (1), the weight ratio of the NaY molecular sieve to the organic acid and the ammonium organic acid can be controlled as 1:(0.06-0.12):(0.02-0.08).

[0017] In some specific embodiments, in step (1), the acidic buffer solution may include at least one of the following combinations: a combination of oxalic acid and ammonium oxalate, a combination of citric acid and ammonium citrate, a combination of acetic acid and ammonium acetate, and a combination of formic acid and ammonium formate.

[0018] According to the specific implementation plan, in step (1), an inorganic acid can be used to adjust the pH value of the first solution. The inorganic acid includes one or more of sulfuric acid, hydrochloric acid, nitric acid, and phosphoric acid.

[0019] According to the specific implementation plan, in step (1), the temperature of the ion exchange can be controlled at 60℃-90℃, and the time of the ion exchange can be controlled at 0.5h-1h.

[0020] According to the specific implementation plan, in step (1), the ion exchange process may include a stirring operation, and the stirring speed can be controlled to be 300rpm-600rpm.

[0021] Wet calcination is calcination in the presence of water. Compared to conventional calcination (calcination in anhydrous conditions), wet calcination can reduce the size of the crystal cells and improve the hydrothermal stability of the molecular sieve. According to the specific implementation scheme, in step (1), the temperature of wet calcination can be controlled at 500℃-800℃, and the time of wet calcination can be controlled at 0.5h-2h.

[0022] According to the specific implementation plan, the first exchange in step (1) can produce amorphous aluminum, and the second ion exchange in step (2) can remove amorphous components. Compared with the acidic environment in step (1), the alkaline environment in step (2) can not only remove amorphous aluminum, but also effectively remove amorphous silicon. The addition of alkaline buffer reagent can also effectively improve the crystallinity of molecular sieve. Furthermore, ion exchange under pressure can improve the sodium removal efficiency and promote the outward migration of sodium ions in NaY cages, thereby reducing the sodium content in molecular sieve to below 0.2 wt%.

[0023] According to the specific implementation plan, in step (2), the second inorganic salt may include a soluble ammonium salt, specifically one or more of the following: ammonium sulfate, ammonium chloride, ammonium nitrate, ammonium acetate, ammonium phosphate, etc.

[0024] According to the specific implementation plan, in step (2), the weight ratio of the intermediate molecular sieve to the second inorganic salt and water can be controlled as 1:(0.1-0.3):(5-8).

[0025] According to the specific implementation plan, in step (2), the present invention found that an excessively high pH value of the second solution would damage the crystallinity of the molecular sieve, while an excessively low pH value would lead to low exchange efficiency. The present invention adjusts the pH value of the second solution to 10.5-12.0, which allows the molecular sieve to maintain a high degree of crystallinity while simultaneously accelerating the exchange efficiency.

[0026] According to the specific implementation plan, in step (2), an alkaline reagent can be used to adjust the pH value of the second solution. The alkaline reagent may include one or a combination of two or more of ammonia, tetramethylammonium hydroxide, tetraethylammonium hydroxide, and tetrapropylammonium hydroxide.

[0027] According to the specific implementation plan, in step (2), the alkaline buffer reagent may include phosphate buffer (PBS) and / or sodium carbamate (CHES), etc. The alkaline buffer reagent used in this invention provides an acid-base strength that is just enough to open the small cages of the molecular sieve to release sodium ions while avoiding damage to the crystallinity of the molecular sieve, and can also remove amorphous silica and aluminum, thereby improving the crystallinity of the molecular sieve.

[0028] According to the specific implementation plan, in step (2), the weight ratio of the intermediate molecular sieve to the alkaline buffer reagent can be controlled to be 1:(0.06-0.12).

[0029] According to the specific implementation plan, in step (2), the temperature of the ion exchange can be controlled at 60℃-90℃, and the time of the ion exchange can be controlled at 0.5h-1h.

[0030] According to the specific implementation plan, in step (2), the pressure of the pressurized environment can be controlled to be 0.1MPa-0.3MPa.

[0031] According to the specific implementation plan, in step (2), the wet calcination can reduce the cell size and improve the hydrothermal stability of the molecular sieve. The temperature of the wet calcination can be controlled at 500-800℃, and the time of the wet calcination can be controlled at 0.5h-2h.

[0032] According to the specific implementation plan, in step (2), the ion exchange process may include a stirring operation, and the stirring speed can be controlled to be 300rpm-600rpm.

[0033] According to a specific embodiment of the present invention, the above preparation method may include:

[0034] (1) Mix NaY molecular sieve with a first inorganic salt and water in a weight ratio of 1:(0.1-0.3):(5-8) to form a slurry. Add an acidic buffer solution containing an organic acid and an ammonium organic acid to the slurry to form a first solution, wherein the weight ratio of NaY molecular sieve to organic acid and ammonium organic acid is 1:(0.06-0.12):(0.02-0.08). Adjust the pH of the first solution to 3.8-4.0 with an inorganic acid. Perform ion exchange at 60℃-90℃ for 0.5h-1h, accompanied by stirring at 300-600rpm during the exchange process. After the exchange is completed, filter the slurry, wash the filter cake with filtered water, and wet bake the filter cake to obtain an intermediate molecular sieve.

[0035] (2) Mix the intermediate molecular sieve with the second inorganic salt and water in a weight ratio of 1:(0.1-0.3):(5-8) to form a slurry. Add an alkaline buffer solution to the slurry to form a second solution. The alkaline buffer solution includes phosphate buffer (PBS) and / or sodium carbamate buffer (CHES). The weight ratio of the intermediate molecular sieve to the alkaline buffer solution is 1:(0.06-0.12). Adjust the pH of the second solution to 10.5-12.0 using the alkaline reagent. Perform ion exchange at 60-90℃ for 0.5-1h in a pressurized environment with a pressure of 0.1-0.3MPa. After the exchange is completed, filter the slurry. Wash the filter cake with filtered water. Wet-roast the filter cake to obtain a low-sodium, high-crystallinity Y molecular sieve.

[0036] The preparation method provided by this invention can not only effectively reduce the sodium content in the molecular sieve, reducing the sodium oxide weight content of the obtained Y-type molecular sieve product to below 0.2 wt%, but also retain the high crystallinity of the molecular sieve, avoiding significant damage to its structure. In some specific embodiments, the crystallinity of the prepared low-sodium, high-crystallinity Y-type molecular sieve is more than 97% of that of the raw material NaY molecular sieve.

[0037] The present invention also provides a low-sodium, high-crystallinity Y-type molecular sieve, which is obtained by the above-described preparation method. In some specific embodiments, the sodium oxide content of the low-sodium, high-crystallinity Y-type molecular sieve is less than 0.2 wt%; the crystallinity of the low-sodium, high-crystallinity Y-type molecular sieve can reach more than 88%.

[0038] The beneficial effects of this invention include:

[0039] 1. This invention provides a method for preparing a low-sodium, high-crystallinity Y-type molecular sieve. The first exchange in this preparation method is carried out in an acidic environment, which can promote the exchange of sodium ions while avoiding damage to the molecular sieve structure. Furthermore, the addition of an acidic buffer can also alleviate the structural damage to the molecular sieve caused by acidic conditions. The second exchange in this preparation method is an alkaline ion exchange carried out in a pressurized environment, which can not only remove amorphous aluminum but also effectively remove amorphous silicon. In addition, by adjusting the appropriate pH value, the crystallinity of the molecular sieve can be effectively improved. The sodium removal efficiency can be improved by carrying out ion exchange in a pressurized environment, thereby effectively reducing the sodium content.

[0040] 2. The preparation method provided by this invention is applicable to the preparation of ammonium Y-type molecular sieves, which can effectively improve the crystallinity of the molecular sieve, reduce the sodium content in the molecular sieve, and improve the activity of the molecular sieve. This preparation method is simple in procedure and has good application prospects, and can be widely applied in the catalytic cracking catalyst industry. Attached Figure Description

[0041] Figure 1 The XRD diffraction patterns are those of the molecular sieve samples from Example 1 and Comparative Example 1. Detailed Implementation

[0042] In order to provide a clearer understanding of the technical features, objectives and beneficial effects of the present invention, the technical solution of the present invention will now be described in detail below, but it should not be construed as limiting the scope of implementation of the present invention.

[0043] In the following experiments, the phase composition and crystallinity of NaY were characterized using a Rigaku D / Max-3C XRD diffractometer, and the crystallinity was defined by the diffraction peak height of Y-type molecular sieve at 2θ = 22-24.5°.

[0044] The NaY molecular sieve used in the comparative and examples was produced by Changting Catalyst Factory, with a relative crystallinity of 90%, a cell size of 24.62, and a sodium oxide weight content of 13.85%.

[0045] Example 1

[0046] This embodiment provides a low-sodium, high-crystallinity Y-type molecular sieve, the preparation process of which is as follows:

[0047] (1) Mix the molecular sieve and ammonium chloride in a weight ratio of NaY:ammonium chloride:water = 1:0.25:6 and add an organic acid buffer reagent containing oxalic acid and ammonium oxalate (oxalic acid:ammonium oxalate:NaY = 0.06:0.02:1 (by weight)) to form a first solution. Adjust the pH of the first solution to 3.8 with sulfuric acid and carry out ion exchange at 60℃ for 0.5h. After the exchange is completed, filter the slurry, wash the filter cake with filtered water, and wet bake at 600℃ for 1.5h to obtain the intermediate molecular sieve.

[0048] (2) The intermediate molecular sieve, ammonium sulfate and water were mixed evenly according to the weight ratio of intermediate molecular sieve: ammonium sulfate: water = 1:0.3:5. The alkaline buffer reagent phosphate buffer reagent PBS (PBS: intermediate molecular sieve = 0.1:1 (by weight)) was added to form a second solution. The pH value of the second solution was adjusted to 12.0 using ammonia water. Ion exchange was carried out at 90°C for 0.5h under 0.1MPa pressure. After the exchange was completed, the slurry was filtered, the filter cake was washed with filtered water and wet-roasted at 600°C for 1h to obtain the low sodium high crystallinity ammonium Y molecular sieve of Example 1.

[0049] Example 2

[0050] This embodiment provides a low-sodium, high-crystallinity Y-type molecular sieve, the preparation process of which is as follows:

[0051] (1) Mix the molecular sieve and ammonium chloride in a weight ratio of NaY:ammonium chloride:water = 1:0.20:5 and add an organic acid buffer (acetic acid:ammonium acetate:NaY = 0.1:0.05:1 by weight). Adjust the pH to 3.9 with hydrochloric acid and exchange at 90℃ for 0.5h. After the exchange is complete, filter the slurry, wash the filter cake with filtered water, and wet bake at 750℃ for 0.5h to obtain the intermediate molecular sieve.

[0052] (2) The molecular sieve and ammonium sulfate were slurried evenly according to the weight ratio of intermediate molecular sieve: ammonium sulfate: water = 1:0.3:5, and sodium carbamate (CHES) (CHES: intermediate molecular sieve = 0.06:1 (by weight)) was added. The pH was adjusted to 11.0 using tetramethylammonium hydroxide. The exchange was carried out at 80°C for 1 hour under a pressure of 0.2 MPa. After the exchange was completed, the slurry was filtered, the filter cake was washed with filtered water, and then wet-dried at 500°C for 2 hours to obtain the low sodium high crystallinity ammonium Y molecular sieve of Example 2.

[0053] Example 3

[0054] This embodiment provides a low-sodium, high-crystallinity Y-type molecular sieve, the preparation process of which is as follows:

[0055] (1) Mix the molecular sieve and ammonium chloride in a weight ratio of NaY:ammonium acetate:water = 1:0.1:6 and add an organic acid buffer (citric acid:ammonium citrate:NaY = 0.12:0.06:1 by weight). Adjust the pH to 4.0 with sulfuric acid and exchange at 75℃ for 1 hour. After the exchange is complete, filter the slurry, wash the filter cake with filtered water, and wet bake at 650℃ for 1.5 hours to obtain the intermediate molecular sieve.

[0056] (2) The intermediate molecular sieve and ammonium sulfate were slurried evenly according to the weight ratio of intermediate molecular sieve: ammonium sulfate: water = 1:0.3:5, and an alkaline buffer reagent phosphate buffer reagent (PBS) was added (PBS: intermediate molecular sieve = 0.12:1 (by weight)). The pH was adjusted to 11.5 with ammonia water, and the exchange was carried out at 90°C for 0.5 h under a pressure of 0.3 MPa. After the exchange was completed, the slurry was filtered, the filter cake was washed with filtered water, and then wet-dried at 700°C for 2 h to obtain the low sodium high crystallinity ammonium Y molecular sieve of Example 3.

[0057] Example 4

[0058] This embodiment provides a low-sodium, high-crystallinity Y-type molecular sieve, the preparation process of which is as follows:

[0059] (1) Mix the molecular sieve and ammonium chloride in a weight ratio of NaY:ammonium nitrate:water = 1:0.3:6 and add an organic acid buffer (formic acid:ammonium formate:NaY = 0.10:0.06:1 by weight). Adjust the pH to 4.0 with sulfuric acid and exchange at 80℃ for 1 hour. After the exchange is complete, filter the slurry, wash the filter cake with filtered water, and wet bake at 650℃ for 1.5 hours to obtain the intermediate molecular sieve.

[0060] (2) The intermediate molecular sieve and ammonium sulfate were slurried evenly according to the weight ratio of intermediate molecular sieve: ammonium phosphate: water = 1:0.3:5, and alkaline buffer reagent phosphate buffer reagent (PBS) (PBS: intermediate molecular sieve = 0.10:1 (by weight)) was added. The pH was adjusted to 10.0 using tetraethylammonium hydroxide. The exchange was carried out at 80°C for 1 hour under a pressure of 0.15 MPa. After the exchange was completed, the slurry was filtered, the filter cake was washed with filtered water, and wet-roasted at 600°C for 2 hours to obtain the low sodium high crystallinity ammonium Y molecular sieve of Example 4.

[0061] Example 5

[0062] This embodiment provides a low-sodium, high-crystallinity Y-type molecular sieve, the preparation process of which is as follows:

[0063] (1) Mix the molecular sieve and ammonium chloride in a weight ratio of NaY:ammonium sulfate:water = 1:0.25:8 and add an organic acid buffer (oxalic acid:ammonium oxalate:NaY = 0.12:0.08:1 by weight). Adjust the pH to 3.6 with sulfuric acid and exchange at 90℃ for 1 hour. After the exchange is complete, filter the slurry, wash the filter cake with filtered water, and wet bake at 650℃ for 2 hours to obtain the intermediate molecular sieve.

[0064] (2) The molecular sieve and ammonium sulfate were slurried evenly according to the weight ratio of intermediate molecular sieve: ammonium chloride: water = 1:0.25:8, and sodium carbamate (CHES) (CHES: intermediate molecular sieve = 0.08:1 (by weight)) was added. The pH was adjusted to 10.5 using tetrapropylammonium hydroxide. The exchange was carried out at 70°C for 0.5 h under a pressure of 0.25 MPa. After the exchange was completed, the slurry was filtered, the filter cake was washed with filtered water, and wet-roasted at 650°C for 2 h to obtain the low sodium high crystallinity ammonium Y molecular sieve of Example 5.

[0065] Comparative Example 1

[0066] This comparative example provides a low-sodium Y-type molecular sieve, which is prepared using a traditional "two-cross-cross-two-calcination" process. The preparation steps are as follows:

[0067] (1) Mix the molecular sieve with ammonium sulfate and water in a weight ratio of NaY:ammonium sulfate:water = 1:0.25:8 to form a first solution. Adjust the pH of the first solution to 3.6 with hydrochloric acid. Exchange at 90℃ for 1 hour. After the exchange is complete, filter the slurry, wash the filter cake with filtered water, and wet bake at 650℃ for 2 hours to obtain the intermediate molecular sieve.

[0068] (2) The intermediate molecular sieve, ammonium sulfate and water were mixed evenly to form a second solution according to the weight ratio of intermediate molecular sieve: ammonium sulfate: water = 1:0.25:8. The pH of the second solution was adjusted to 3.8 using hydrochloric acid and exchanged at 90℃ for 1 hour. After the exchange was completed, the slurry was filtered, the filter cake was washed with filtered water and wet-roasted at 650℃ for 2 hours to obtain the low sodium Y-type molecular sieve of Comparative Example 1.

[0069] Comparative Example 2

[0070] This comparative example provides an ammonium Y-type molecular sieve, and the preparation process is as follows:

[0071] (1) Mix the molecular sieve with ammonium sulfate and water in a weight ratio of NaY:ammonium sulfate:water = 1:0.3:6 to form a first solution. Adjust the pH to 11.5 with ammonia water, exchange at 90℃ for 1 h, and wet roast at 650℃ for 2 h to obtain the intermediate molecular sieve.

[0072] (2) Repeat step (1) with the intermediate molecular sieve to obtain the ammonium Y-type molecular sieve of Comparative Example 2.

[0073] Comparative Example 3

[0074] This comparative example provides an ammonium Y-type molecular sieve, and the preparation process is as follows:

[0075] (1) Mix the molecular sieve and ammonium chloride in a weight ratio of NaY:ammonium chloride:water = 1:0.20:5 and add organic acid (acetic acid:NaY = 0.1:1 by weight)). Adjust the pH to 3.9 with hydrochloric acid and exchange at 90℃ for 0.5h. After the exchange is complete, filter the slurry, wash the filter cake with filtered water, and wet bake at 750℃ for 0.5h to obtain the intermediate molecular sieve.

[0076] (2) The molecular sieve and ammonium sulfate were mixed evenly according to the weight ratio of intermediate molecular sieve: ammonium sulfate: water = 1:0.3:5. The pH was adjusted to 11.0 using tetramethylammonium hydroxide. The mixture was exchanged at 80°C for 1 hour under a pressure of 0.2 MPa. After the exchange was completed, the slurry was filtered, the filter cake was washed with filtered water, and then wet-roasted at 500°C for 2 hours to obtain the comparative example 3ammonium Y molecular sieve.

[0077] Comparative Example 4

[0078] This comparative example provides an ammonium Y-type molecular sieve, and the preparation process is as follows:

[0079] (1) Mix NaY:ammonium sulfate:water in a weight ratio of 1:0.3:5 until homogeneous, and add alkaline buffer reagent phosphate buffer reagent PBS (PBS:NaY = 0.1:1 by weight) to form a first solution. Adjust the pH of the first solution to 12.0 using ammonia water. Ion exchange is performed at 90℃ for 0.5h under a pressure of 0.1MPa. After the exchange is completed, filter the slurry, wash the filter cake with filtered water until neutral, and wet bake at 600℃ for 1h to obtain an intermediate molecular sieve.

[0080] (2) The intermediate molecular sieve and ammonium chloride were slurried evenly according to the weight ratio of intermediate molecular sieve: ammonium chloride: water = 1:0.25:6. An organic acid buffer reagent containing oxalic acid and ammonium oxalate (oxalic acid: ammonium oxalate: NaY = 0.06:0.02:1 (by weight)) was added to form a second solution. The pH value of the second solution was adjusted to 3.8 using sulfuric acid. Ion exchange was carried out at 60°C for 0.5 h under a pressure of 0.1 MPa. After the exchange was completed, the slurry was filtered, the filter cake was washed with filtered water, and wet-dried at 600°C for 1.5 h to obtain the molecular sieve of Comparative Example 4.

[0081] Comparative Example 5

[0082] This comparative example provides an ammonium Y-type molecular sieve, and the preparation process is as follows:

[0083] (1) Mix NaY:ammonium sulfate:water in a weight ratio of 1:0.3:8 until homogeneous. Adjust the pH of the first solution to 12.0 using ammonia water. Perform ion exchange at 90℃ for 0.5h. After the exchange is complete, filter the slurry. Wash the filter cake with filtered water until neutral and then wet bake at 600℃ for 1h to obtain an intermediate molecular sieve.

[0084] (2) The intermediate molecular sieve and ammonium chloride were slurried evenly according to the weight ratio of intermediate molecular sieve: ammonium chloride: water = 1:0.25:6, and a solution containing alkaline buffer reagent phosphate buffer reagent PBS (PBS: intermediate molecular sieve = 0.1:1 (by weight)) was added. The pH value of the solution was adjusted to 11.5 using ammonia water. Ion exchange was carried out at 60°C for 0.5h under 0.1MPa pressure. After the exchange was completed, the slurry was filtered, the filter cake was washed with filtered water, and wet-dried at 600°C for 1.5h to obtain comparative example 5 molecular sieve.

[0085] Figure 1 The images show the XRD diffraction patterns of the low-sodium, high-crystallinity Y-type molecular sieve of Example 1 and the low-sodium Y-type molecular sieve of Comparative Example 1. Figure 1 It can be seen that, compared with the molecular sieve of Comparative Example 1, the molecular sample prepared in Example 1 of the present invention has stronger Y-type molecular sieve characteristic diffraction peaks and higher Y-type molecular sieve crystallinity.

[0086] The sodium oxide mass content and crystallinity of the Y-type molecular sieve products from Examples 1 to 5 and Comparative Examples 1 to 2 were measured, and the results are summarized in Table 1. The sodium oxide mass content was tested using the fluorescence method, and the crystallinity was tested using the peak area method.

[0087] Table 1

[0088]

[0089] As can be seen from the results in Table 1, compared with the Y-type molecular sieves prepared in the comparative example, the Y-type molecular sieves prepared in each embodiment of the present invention have lower sodium oxide content and higher crystallinity. These results indicate that, compared with existing methods for reducing sodium content in Y-type molecular sieves, the method provided by the present invention can more effectively reduce the sodium content of Y-type molecular sieves while maintaining a high degree of crystallinity.

[0090] As can be seen from the comparison between Comparative Example 1 and the various embodiments, by adding an acidic buffer solution to the acidic exchange environment of the first exchange and an alkaline buffer solution to the alkaline exchange environment of the second exchange during ion exchange, compared with the traditional two-exchange, two-baking method, the sodium content in the molecular sieve can be effectively reduced and the crystallinity of the molecular sieve can be improved.

[0091] As can be seen from the comparison between Comparative Example 2 and the various embodiments, compared with the two-cross-two-roasting method in an alkaline environment, the method provided by the present invention can synergistically improve the crystallinity of molecular sieves and reduce sodium content by using acid treatment and alkali treatment.

[0092] As can be seen from the comparison between Comparative Example 3 and Example 2, although adding organic acid alone also has a sodium-reducing effect, its acid strength is greater than that of adding ammonium organic acid + organic acid simultaneously, resulting in poor crystallinity of the molecular sieve. Ammonium organic acid has a buffering effect, and its presence can also reduce sodium content. Therefore, the sodium removal effect of adding ammonium organic acid is better than that of adding organic acid alone. In addition, by adding an alkaline buffer reagent, not only can the alkalinity of the alkaline environment in the second exchange be made milder, avoiding damage to the crystallinity of the molecular sieve, but it can also precisely open the small cages of the molecular sieve to release sodium ions, reducing the sodium ion content, while removing some amorphous silica and aluminum, thus improving the crystallinity of the molecular sieve.

[0093] As can be seen from the comparison between Comparative Example 4 and Example 1, the treatment effect of the acid-base exchange sequence is better. Since the first step of exchange produces amorphous material, the second step of alkali treatment can remove the amorphous silicon and aluminum, which can further improve the crystallinity of the molecular sieve.

[0094] As can be seen from the comparison between Comparative Example 5 and the various embodiments, the first step involves sodium reduction through alkaline exchange, while the second step, which only involves the addition of an alkaline buffer, results in a poorer sodium reduction effect and lower crystallinity. This result indicates that the acid-base exchange environment with the addition of an acidic buffer can open the molecular sieve cages to allow Na ions to escape without damaging the crystallinity of the molecular sieve.

[0095] The above experimental results demonstrate that the method provided by this invention can reduce the Na content of Y-type molecular sieves while avoiding damage to their crystallinity. This preparation method is applicable to the preparation of ammonium Y-type molecular sieves, yielding molecular sieves with high crystallinity and low sodium content, while also improving their activity. The preparation method is simple and has excellent application prospects, and can be widely applied in the catalytic cracking catalyst industry.

Claims

1. A method for preparing a low-sodium, high-crystallinity Y-molecular sieve, the method comprising: (1) Mix NaY molecular sieve with a first inorganic salt and water to form a slurry. Add an acidic buffer solution to the slurry to form a first solution. Adjust the pH of the first solution to 3.8-4.0 and carry out ion exchange. After the exchange is completed, filter, wash with water, and wet roast to obtain an intermediate molecular sieve. (2) Mix the intermediate molecular sieve with the second inorganic salt and water to form a slurry. Add an alkaline buffer solution to the slurry to form a second solution. Adjust the pH of the second solution to 10.5-12.

0. Perform ion exchange in a pressurized environment. After the exchange is completed, filter, wash with water, and wet roast to obtain a low-sodium, high-crystallinity Y molecular sieve. The alkaline buffer solution includes phosphate buffer and / or sodium carbamate buffer.

2. The production method according to claim 1, wherein The first inorganic salt and the second inorganic salt each comprise soluble ammonium salts.

3. The production method according to claim 1, wherein, The weight ratio of the NaY molecular sieve to the first inorganic salt and water is 1:(0.1-0.3):(5-8).

4. The production method according to claim 1, wherein The acidic buffer solution comprises a combination of organic acids and ammonium organic acids.

5. The preparation method according to claim 4, wherein, The weight ratio of the NaY molecular sieve to organic acid and ammonium organic acid is 1:(0.06-0.12):(0.02-0.08).

6. The preparation method according to claim 1, wherein, In step (1), the temperature of the ion exchange is 60℃-90℃, and the time of the ion exchange is 0.5h-1h; And / or, in step (1), the temperature of the wet baking is 500℃-800℃, and the time of the wet baking is 0.5h-2h.

7. The preparation method according to claim 1, wherein, The weight ratio of the intermediate molecular sieve to the second inorganic salt and water is 1:(0.1-0.3):(5-8).

8. The preparation method according to claim 1, wherein, The weight ratio of the intermediate molecular sieve to the alkaline buffer reagent is 1:(0.06-0.12).

9. The preparation method according to claim 1, wherein, The pH value of the second solution was adjusted using an alkaline reagent; The alkaline reagent includes one or more of ammonia, tetramethylammonium hydroxide, tetraethylammonium hydroxide, and tetrapropylammonium hydroxide.

10. The preparation method according to claim 1, wherein, In step (2), the temperature of the ion exchange is 60℃-90℃, the time of the ion exchange is 0.5h-1h, and the pressure of the pressurized environment is 0.1MPa-0.3MPa. And / or, in step (2), the temperature of the wet baking is 500℃-800℃, and the time of the wet baking is 0.5h-2h.

11. The preparation method according to claim 1, wherein, The crystallinity of the low-sodium, high-crystallinity Y-type molecular sieve is more than 97% of that of the NaY molecular sieve.

12. A low-sodium, high-crystallinity Y-type molecular sieve, which is obtained by the preparation method according to any one of claims 1-11.

13. The low-sodium, high-crystallinity Y-type molecular sieve according to claim 12, wherein, The sodium oxide content of the low-sodium, high-crystallinity Y-type molecular sieve is less than 0.2 wt%. The crystallinity of the low-sodium, high-crystallinity Y-type molecular sieve is above 88%.

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