Process for the preparation of molecular sieve pellets

Abstract

This invention relates to the field of molecular sieve preparation and discloses a method for preparing molecular sieve microspheres. The method comprises: 1) rolling a mixture of molecular sieve powder and alumina powder into microspheres in the presence of water; 2) contacting the microspheres obtained in step 1) with an acid solution, separating the microspheres, and then calcining them. The method of preparing molecular sieve microspheres of this invention yields molecular sieve microspheres with excellent sphericity and improved strength.

Description

Technical Field

[0001] This invention relates to the field of molecular sieve preparation, and specifically to a method for preparing molecular sieve microspheres. Background Technology

[0002] Alumina microspheres are important catalyst carriers, and are often prepared using the oil column molding method. This involves dissolving the alumina-containing raw material in acid to form a sol, which is then dropped into an oil column. The surface tension causes the sol to shrink and gel, forming microspheres. This method produces microspheres with good sphericity and high strength, generally exceeding 40 N / particle. However, the oil column molding process is complex, requires strict control, and generates a large amount of oily wastewater.

[0003] Roll forming is another spheroidizing process, usually carried out in a coating pan. The method involves adding powder to the coating pan, starting the pan, rotating it at a certain speed, and spraying in an appropriate amount of solution, causing the powder to gradually agglomerate and grow into spheres. This process is simple to operate and does not produce wastewater, but the quality of the alumina spheres produced is far inferior to that produced by oil column forming, with significant differences in sphericity and strength. Summary of the Invention

[0004] The inventors of this invention discovered in their research that spraying an acid solution into the ball forming process can increase the viscosity of the powder, but the viscosity of the material is not easy to control, and the balls tend to grow too quickly, which reduces the strength and makes the balls not round.

[0005] To solve this problem, the inventors of this invention conducted further in-depth research and found that when a mixture of molecular sieve powder and alumina powder is spheroidized, the process is carried out only in the presence of water and not in the presence of acid. Furthermore, by contacting the spheroidized pellets with an acid solution, separating the pellets, and then calcining them, molecular sieve pellets with excellent sphericity and improved strength can be obtained, thus completing this invention.

[0006] Therefore, the purpose of this invention is to provide a method for preparing molecular sieve microspheres, which can obtain molecular sieve microspheres with excellent sphericity and improved strength.

[0007] Therefore, the present invention provides a method for preparing molecular sieve microspheres, wherein the method includes the following steps: 1) The step of rolling a mixture of molecular sieve powder and alumina powder into small balls in the presence of water; 2) The step of contacting the small balls obtained in step 1) with the acid solution, separating the small balls and calcining them.

[0008] Preferably, in step 1), the mixed powder containing molecular sieve powder and alumina powder is rolled into balls in the presence of water only to obtain small balls.

[0009] Preferably, in the absence of acid, the mixed powder containing molecular sieve powder and alumina powder is rolled into balls to obtain small balls.

[0010] Preferably, the weight ratio of water to the mixed powder is 0.2-0.55:1, more preferably 0.3-0.5:1.

[0011] Preferably, the water is added by spraying.

[0012] Preferably, the rotational speed of the ball forming is 20-50 rpm.

[0013] Preferably, the weight ratio of the molecular sieve powder to the alumina powder is 1:0.05-1, and more preferably 1:0.4-1.

[0014] Preferably, the molecular sieve powder is one or more of ZSM-5 molecular sieve powder, X-type molecular sieve powder, A-type molecular sieve powder, Y-type molecular sieve powder, β-type molecular sieve powder, SAPO-34 molecular sieve powder, mordenite zeolite, and MCM-22 molecular sieve powder.

[0015] Preferably, the molecular sieve powder has a particle size of 0.5-5 μm, and more preferably 0.7-3 μm.

[0016] Preferably, the alumina powder has a particle size of 10-90 μm, and more preferably 30-50 μm.

[0017] Preferably, in step 2), the acid in the acid solution is one or more of nitric acid, hydrochloric acid, citric acid, formic acid, glacial acetic acid, chloroacetic acid, and oxalic acid.

[0018] Preferably, the acid content in the acid solution is 1-70% by weight, more preferably 10-50% by weight.

[0019] Preferably, the volume ratio of the acid solution to the microsphere is 0.8-5:1, and more preferably 1-3:1.

[0020] Preferably, the contact conditions include a temperature of 5-45°C and a time of 0.5-10 min.

[0021] Preferably, the method further includes a step of drying the microspheres before calcining them.

[0022] Preferably, the calcination conditions include: a temperature of 500-800℃ and a time of 1-10h.

[0023] Through the above technical solution, the present invention can provide a method for preparing molecular sieve microspheres, which can obtain molecular sieve microspheres with excellent sphericity and improved strength. Attached Figure Description

[0024] Figure 1 The image shows the molecular sieve spheres obtained in Example 1. Figure 2 This is an image of the molecular sieve spheres obtained in Comparative Example 2. Detailed Implementation

[0025] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0026] This invention provides a method for preparing molecular sieve microspheres, wherein the method includes the following steps: 1) The step of rolling a mixture of molecular sieve powder and alumina powder into small balls in the presence of water; 2) The step of contacting the small balls obtained in step 1) with the acid solution, separating the small balls and calcining them.

[0027] According to the method of the present invention, in step 1), a mixed powder containing molecular sieve powder and alumina powder is ball-rolled in the presence of water only to obtain small balls. Furthermore, a mixed powder containing molecular sieve powder and alumina powder is ball-rolled in the absence of acid to obtain small balls.

[0028] This invention involves spheroidizing in the presence of water rather than an acid solution, which makes it easier to control the viscosity of the material and results in sphericity of the spheres. Furthermore, by contacting the spheres with an acid solution, separating them, and then calcining them, molecular sieve spheres with excellent sphericity and improved strength can be obtained.

[0029] According to the method of the present invention, preferably, the weight ratio of water to the mixed powder is 0.2-0.55:1; more preferably, from the viewpoint of further improving strength, the weight ratio of water to the mixed powder is 0.3-0.5:1; particularly preferably, the weight ratio of water to the mixed powder is 0.31-0.47:1.

[0030] Specific examples of the weight ratio of water to the mixed powder include, for example, 0.2:1, 0.25:1, 0.3:1, 0.31:1, 0.32:1, 0.35:1, 0.4:1, 0.45:1, 0.46:1, 0.47:1, 0.48:1, 0.5:1, and the ranges formed by the two mentioned above.

[0031] In this invention, by keeping the weight ratio of water to the mixed powder within the above-mentioned range, the sphericity of the spheres obtained by ball rolling can be improved.

[0032] According to the method of the present invention, the water is preferably added by spraying. Adding the water by spraying has the advantages of uniform wetting and preventing clumping.

[0033] According to the method of the present invention, there are no particular limitations on the conditions for ball forming. For example, the rotation speed of ball forming can be 5-50 rpm; preferably, the rotation speed of ball forming is 20-50 rpm; more preferably, the rotation speed of ball forming is 30-50 rpm; and particularly preferably, the rotation speed of ball forming is 40-50 rpm.

[0034] Furthermore, those skilled in the art can select the size of the ball according to specific needs; for example, it can be a ball with a diameter of 1.5-3mm.

[0035] According to the method of the present invention, the weight ratio of the molecular sieve powder to the alumina powder is selected according to the strength requirements. Considering both reaction performance and other factors, preferably, the weight ratio of the molecular sieve powder to the alumina powder is 1:0.05-1; more preferably, the weight ratio of the molecular sieve powder to the alumina powder is 1:0.4-1.

[0036] Specific examples of the weight ratio of the molecular sieve powder to the alumina powder include, for example, 0.05:1, 0.1:1, 0.2:1, 0.25:1, 0.3:1, 0.35:1, 0.4:1, 0.45:1, 0.5:1, 0.55:1, 0.6:1, 0.65:1, 0.7:1, 0.75:1, 0.8:1, 0.85:1, 0.9:1, 0.95:1, 1:1, etc., as well as the ranges formed by the two mentioned above.

[0037] According to the method of the present invention, the molecular sieve powder is not particularly limited. For example, the molecular sieve powder can be one or more of ZSM-5 molecular sieve powder, X-type molecular sieve powder, A-type molecular sieve powder, Y-type molecular sieve powder, β-type molecular sieve powder, SAPO-34 molecular sieve powder, mordenite zeolite and MCM-22 molecular sieve powder.

[0038] In one specific embodiment of the present invention, the molecular sieve powder is ZSM-5 molecular sieve powder.

[0039] According to the method of the present invention, considering the effect of further improving strength, preferably, the particle size of the molecular sieve powder is 0.5-5 μm; more preferably, the particle size of the molecular sieve powder is 0.7-3 μm; and even more preferably, the particle size of the molecular sieve powder is 1-2 μm.

[0040] Specific examples of the particle size of the molecular sieve powder include, for example, 0.5 μm, 0.6 μm, 0.7 μm, 0.8 μm, 0.9 μm, 1 μm, 1.5 μm, 2 μm, 2.5 μm, 3 μm, 3.5 μm, 4 μm, 4.5 μm, 5 μm, etc., as well as any two of the above ranges.

[0041] According to the method of the present invention, from the perspective of further improving the spheroidizing effect, preferably, the particle size of the alumina powder is 10-90 μm; more preferably, the particle size of the alumina powder is 30-50 μm; and even more preferably, the particle size of the alumina powder is 35-40 μm.

[0042] Specific examples of the particle size of the alumina powder include 10μm, 15μm, 20μm, 25μm, 30μm, 35μm, 40μm, 45μm, 50μm, 55μm, 60μm, 65μm, 70μm, 75μm, 80μm, 85μm, 90μm, and any two of the above ranges.

[0043] According to the method of the present invention, preferably, in step 2), the acid in the acid solution is one or more of nitric acid, hydrochloric acid, citric acid, formic acid, glacial acetic acid, chloroacetic acid and oxalic acid; more preferably, in step 2), the acid in the acid solution is nitric acid and / or hydrochloric acid.

[0044] According to the method of the present invention, the acid content in the acid solution can be selected within a wide range. Considering the effect of further improving the strength, preferably, the acid content in the acid solution is 1-70% by weight; more preferably, the acid content in the acid solution is 10-50% by weight; and even more preferably, the acid content in the acid solution is 15-35% by weight.

[0045] According to the method of the present invention, the amount of acid solution used can be selected according to the amount of microspheres used. Preferably, the volume ratio of acid solution to microspheres is 0.8-5:1; more preferably, the volume ratio of acid solution to microspheres is 1-3:1.

[0046] Specific examples of the volume ratio of the acid solution to the microsphere include, for example, 0.8:1, 0.9:1, 1:1, 2:1, 3:1, 4:1, 5:1, and any two of the above.

[0047] In a preferred embodiment of the present invention, the acid solution is soaked in the same volume as the microsphere.

[0048] According to the method of the present invention, the contact is preferably carried out at room temperature. Preferably, the contact conditions include a temperature of 5-45°C and a time of 0.5-10 min; more preferably, the contact conditions include a temperature of 10-30°C and a time of 1-5 min.

[0049] According to the method of the present invention, in a preferred embodiment, the method further includes a step of drying the microspheres before calcining them.

[0050] Drying the pellets before calcining them has the advantage of slow dehydration.

[0051] The drying conditions described above may include, for example, a drying temperature of 80-150°C and a drying time of 1-5 hours; preferably, the drying conditions include a drying temperature of 90-120°C and a drying time of 1-3 hours.

[0052] According to the method of the present invention, preferably, the calcination conditions include: a temperature of 500-800℃ and a time of 1-10h; more preferably, the calcination conditions include: a temperature of 550-650℃ and a time of 3-6h.

[0053] The present invention will be described in detail below through embodiments, but the present invention is not limited to the following embodiments.

[0054] Example 1 1) Mix the molecular sieve raw powder (ZSM-5 molecular sieve powder, particle size 1.0μm, the same below) and alumina powder (particle size 35μm, purchased from China Aluminum Shandong Co., Ltd., the same below) at a weight ratio of 70:30 (dry basis), put them into a sugar coating pot, and spray water at 45rpm to form balls (the weight ratio of water to mixed powder is 0.42:1) until the particle size reaches 2.0mm.

[0055] 2) Take 10 kg of the grown balls and put them into a stirred tank. Pour in a 20% by weight dilute nitric acid solution, ensuring the solution volume covers the balls. Stir slowly at 5 rpm until homogeneous and soak for 2 minutes.

[0056] 3) Take out the small balls, dry them at 110℃ for 2 hours, and then calcine them at 650℃ for 4 hours to obtain molecular sieve small balls S1.

[0057] The image of the molecular sieve spheres obtained in Example 1 is shown below. Figure 1 As shown, through Figure 1 It can be seen that the molecular sieve microspheres obtained in Example 1 are round and have good sphericity.

[0058] Example 2 1) Mix the molecular sieve powder and alumina powder at a weight ratio of 70:30 (dry basis), put them into a sugar coating pot, and spray water at 45 rpm to form balls (the weight ratio of water to mixed powder is 0.32:1), with a length of 2.0 mm.

[0059] 2) Take 10 kg of the grown balls and put them into a stirred tank. Pour in a 20% by weight dilute nitric acid solution, ensuring the solution volume covers the balls. Stir slowly at 5 rpm until homogeneous and soak for 2 minutes.

[0060] 3) Take out the small balls, dry them at 110℃ for 2 hours, and then calcine them at 650℃ for 4 hours to obtain molecular sieve small balls S2.

[0061] The molecular sieve microspheres obtained in Example 2 were round and had good sphericity, similar to those in Example 1.

[0062] Example 3 1) Mix the molecular sieve powder and alumina powder at a weight ratio of 70:30 (dry basis), put them into a sugar coating pot, and spray water at 45 rpm to form balls (the weight ratio of water to mixed powder is 0.46:1), with a length of 2.0 mm.

[0063] 2) Take 10 kg of the grown balls and put them into a stirred tank. Pour in a 20% by weight dilute nitric acid solution, ensuring the solution volume covers the balls. Stir slowly at 5 rpm until homogeneous and soak for 2 minutes.

[0064] 3) Take out the small balls, dry them at 110℃ for 2 hours, and then calcine them at 650℃ for 4 hours to obtain molecular sieve small balls S3.

[0065] The molecular sieve microspheres obtained in Example 3 were round and had good sphericity, similar to those in Example 1.

[0066] Example 4 1) Mix the molecular sieve powder and alumina powder at a weight ratio of 70:30 (dry basis), put them into a sugar coating pot, and spray water at 45 rpm to form balls (the weight ratio of water to mixed powder is 0.28:1), with a length of 2.0 mm.

[0067] 2) Take 10 kg of the grown balls and put them into a stirred tank. Pour in a 20% by weight dilute nitric acid solution, ensuring the solution volume covers the balls. Stir slowly at 5 rpm until homogeneous and soak for 2 minutes.

[0068] 3) Take out the small balls, dry them at 110℃ for 2 hours, and then calcine them at 650℃ for 4 hours to obtain molecular sieve small balls S4.

[0069] The molecular sieve microspheres obtained in Example 4 were round and had good sphericity, similar to those in Example 1.

[0070] Example 5 1) Mix the molecular sieve powder and alumina powder in a weight ratio of 50:50 (dry basis), put them into a sugar coating pot, and spray water at 45 rpm to form balls (the weight ratio of water to mixed powder is 0.42:1) until the particle size reaches 2.0 mm.

[0071] 2) Take 10 kg of the grown balls and put them into a stirred tank. Pour in a 20% by weight dilute nitric acid solution, ensuring the solution volume covers the balls. Stir slowly at 5 rpm until homogeneous and soak for 2 minutes.

[0072] 3) Take out the small balls, dry them at 110℃ for 2 hours, and then calcine them at 650℃ for 4 hours to obtain molecular sieve small balls S5.

[0073] The molecular sieve microspheres obtained in Example 5 were round and had good sphericity, similar to those in Example 1.

[0074] Example 6 The method of Example 1 was followed, except that 20% by weight hydrochloric acid solution was used instead of 20% by weight dilute nitric acid solution, and molecular sieve microspheres S6 were obtained in the same way.

[0075] 1) Mix the molecular sieve raw powder and alumina powder at a weight ratio of 70:30 (dry basis), put them into a sugar coating pot, and spray water at 45 rpm to form balls (the weight ratio of water to mixed powder is 0.42:1) until the particle size reaches 2.0 mm.

[0076] 2) Take 10 kg of the shaped balls and put them into a mixing vessel. Pour in a 20% by weight hydrochloric acid solution, ensuring the solution volume covers the balls. Stir slowly at 5 rpm until homogeneous and soak for 2 minutes.

[0077] 3) Take out the small balls, dry them at 110℃ for 2 hours, and then calcine them at 650℃ for 4 hours to obtain molecular sieve small balls S6.

[0078] The molecular sieve microspheres obtained in Example 6 were round and had good sphericity, similar to those in Example 1.

[0079] Comparative Example 1 The method of Example 1 was followed, except that step 2 was not performed (i.e., acid treatment was not performed), to obtain molecular sieve microspheres D1.

[0080] Comparative Example 2 The method was carried out according to Example 1, except that 1% by weight of nitric acid solution was used to replace water, and molecular sieve microspheres D2 were obtained in the same way.

[0081] The image of the molecular sieve spheres obtained in Comparative Example 2 is shown below. Figure 2 As shown, through Figure 2 It can be seen that the molecular sieve spheres obtained in Comparative Example 2 are not round and have poor sphericity.

[0082] Test Example 1 The sphericity and strength of the molecular sieve microspheres obtained in Examples 1-6 and Comparative Examples 1-2 were tested according to the following methods.

[0083] Sphericity: Reference Figure 1 and Figure 2 To make a judgment, similar to Figure 1 When judged as having good sphericity, similar to Figure 2 If it is not round, it is judged as not round.

[0084] Strength testing method: The strength test was conducted on a DL2 particle strength tester (manufactured by Dalian Penghui Technology Development Co., Ltd.). Ten small balls were randomly selected, and their crushing strength was measured separately. The average value was taken.

[0085] The test results are shown in Table 1. Table 1

[0086] As can be seen from the results in Table 1, Examples 1-6, which use the present invention to first form small balls with water and then contact the small balls with an acid solution, have the effects of good sphericity and significantly improved strength.

[0087] Furthermore, a comparison of Examples 1-3 and Example 4 shows that when the weight ratio of water to the mixed powder is 0.3-0.5:1, the strength can be further improved.

[0088] The preferred embodiments of the present invention have been described in detail above; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combinations of various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.

Claims

1. A process for the preparation of molecular sieve pellets, characterized by, The method includes the following steps: 1) The step of rolling a mixture of molecular sieve powder and alumina powder into small balls in the presence of water; 2) The step of contacting the small balls obtained in step 1) with the acid solution, separating the small balls and calcining them.

2. The method of claim 1, wherein, In step 1), the mixed powder containing molecular sieve powder and alumina powder is rolled into balls in the presence of water only to obtain small balls; Preferably, in the absence of acid, the mixed powder containing molecular sieve powder and alumina powder is rolled into balls to obtain small balls.

3. The method of claim 1, wherein, The weight ratio of water to the mixed powder is 0.2-0.55:1, preferably 0.3-0.5:1; Preferably, the water is added by spraying; Preferably, the rotational speed of the ball forming is 20-50 rpm.

4. The method of any of claims 1-3, wherein, The weight ratio of the molecular sieve powder to the alumina powder is 1:0.05-1, preferably 1:0.4-1.

5. The method of any of claims 1-3, wherein, The molecular sieve powder is one or more of the following: ZSM-5 molecular sieve powder, X-type molecular sieve powder, A-type molecular sieve powder, Y-type molecular sieve powder, β-type molecular sieve powder, SAPO-34 molecular sieve powder, mordenite zeolite, and MCM-22 molecular sieve powder.

6. The method of any of claims 1-3, wherein, The molecular sieve powder has a particle size of 0.5-5 μm, preferably 0.7-3 μm.

7. The method according to any one of claims 1-3, wherein, The alumina powder has a particle size of 10-90 μm, preferably 30-50 μm.

8. The method according to any one of claims 1-3, wherein, In step 2), the acid in the acid solution is one or more of nitric acid, hydrochloric acid, citric acid, formic acid, glacial acetic acid, chloroacetic acid, and oxalic acid.

9. The method according to any one of claims 1-3, wherein, The acid content in the acid solution is 1-70% by weight, preferably 10-50% by weight.

10. The method according to any one of claims 1-3, wherein, The volume ratio of the acid solution to the microsphere is 0.8-5:1, preferably 1-3:

1.

11. The method according to any one of claims 1-3, wherein, The contact conditions include a temperature of 5-45°C and a time of 0.5-10 min.

12. The method according to any one of claims 1-3, wherein, The method further includes a step of drying the microspheres before calcining them.

13. The method according to any one of claims 1-3, wherein, The roasting conditions include a temperature of 500-800℃ and a time of 1-10h.

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