A SAPO-34 molecular sieve, its preparation method and application

Abstract

This invention provides a SAPO-34 molecular sieve, its preparation method, and its application. The preparation method of this invention includes: (1) preparing a directing agent using a degraded MTO catalyst; (2) mixing an aluminum source, a phosphorus source, water, and selectively added silicon source and selectively added template agent to prepare gel II; (3) mixing the directing agent prepared in step (1) with the gel II prepared in step (2), adjusting the pH, and performing hydrothermal crystallization to obtain the SAPO-34 molecular sieve. The method of this invention can achieve minimal or even no template agent, and the prepared SAPO-34 molecular sieve has a smaller particle size and more uniform distribution, exhibiting high catalytic performance in methanol-to-olefins reactions.

Description

Technical Field

[0001] This invention relates to the field of molecular sieves, specifically to a SAPO-34 molecular sieve, its preparation method, and its applications. Background Technology

[0002] SAPO-34 molecular sieve is a type of phosphorus-aluminum molecular sieve with a structure similar to chalcogenide, belonging to the trigonal crystal system. Due to its good thermal and hydrothermal stability, moderate acidity, high specific surface area, and highly ordered microporous channels, SAPO-34 molecular sieve is widely used in the petroleum processing industry. In particular, when SAPO-34 molecular sieve is used as an active component in methanol-to-olefins (MTO) reactions, it exhibits high methanol conversion rates, and selectivity for ethylene and propylene can exceed 80%, with C5... + The content of the component is relatively low.

[0003] Generally, the synthesis of SAPO-34 molecular sieves requires the addition of a template agent, typically an organic amine such as morpholine, triethylamine, or tetraethylammonium hydroxide. These organic amines not only act as templates but also provide a suitable preparation environment. Therefore, a template agent is essential in the synthesis of SAPO-34 molecular sieves, and the amount added is relatively large, resulting in high synthesis costs. Furthermore, residual template agents in the mother liquor require further treatment, which can also lead to environmental pollution.

[0004] In addition, regarding the utilization of MTO catalysts after service life, CN105582885A discloses a method for preparing adsorbents and removing methanol from spent catalysts containing molecular sieves. This method involves preparing adsorbents from spent catalysts containing SAPO-34 using methods such as ball rolling, sheet forming, or extrusion, and then using them to remove methanol and other oxygen-containing compounds from olefin feedstocks. However, this method still suffers from the problem of low utilization rate of the MTO catalyst after service life, and it cannot be recycled as a catalyst.

[0005] In summary, how to synthesize SAPO-34 molecular sieves with minimal or even no template agents, and how to prepare high-performance methanol-to-olefins catalysts, as well as how to fully utilize the resources of methanol-to-olefins catalysts after their service life, have always been hot research topics for researchers. Summary of the Invention

[0006] To address the shortcomings of existing technologies, this invention provides a SAPO-34 molecular sieve, its preparation method, and its applications. The method of this invention can achieve minimal or even no template agent, and the prepared SAPO-34 molecular sieve has a smaller particle size and more uniform distribution, exhibiting high catalytic performance in methanol-to-olefins reactions.

[0007] This invention provides a method for preparing SAPO-34 molecular sieve, comprising:

[0008] (1) Using the dedirecting agent prepared from the MTO catalyst after it has been in service;

[0009] (2) Aluminum source, phosphorus source, water, and selectively added silicon source and selectively added template agent are mixed to prepare gel II;

[0010] (3) The directing agent prepared in step (1) is mixed with the gel II prepared in step (2), the pH is adjusted, and hydrothermal crystallization is carried out to prepare SAPO-34 molecular sieve.

[0011] Further, the method for preparing the directing agent in step (1) includes: preparing an initial gel I by combining the in-service MTO catalyst with an aluminum source, a silicon source, a phosphorus source, a template agent and water; and then crystallizing the initial gel I under low temperature conditions to prepare the directing agent.

[0012] Furthermore, the MTO catalyst after service can be fine powder obtained from a cyclone separator in an industrial methanol-to-olefins unit or catalyst obtained from a settling tank.

[0013] Furthermore, based on the weight of the serviced MTO catalyst, the serviced MTO catalyst comprises: 20%–60% SAPO-34 molecular sieve, 30%–50% kaolin, and 5%–20% binder. The binder is a conventional binder, such as alumina.

[0014] Furthermore, in this invention, the aluminum source is one or more of alumina, boehmite, aluminum isopropoxide, etc.; the silicon source is one or more of silica sol, tetraethyl orthosilicate, silica, etc.; the phosphorus source is one or more of phosphoric acid, phosphate, phosphorous acid, etc.; and the template agent is one or more of morpholine, triethylamine, and tetraethylammonium hydroxide, preferably one or more of triethylamine and tetraethylammonium hydroxide. The types of aluminum source, silicon source, phosphorus source, and template agent used in each step can be the same or different.

[0015] Further, in step (1) when preparing the directing agent, the aluminum source is represented by Al2O3, the silicon source by SiO2, the phosphorus source by H3PO4, and the template agent by R. Then the molar ratio of Al2O3:SiO2:P2O5:R:H2O is 1:0.1-1.5:0.01-2.0:1.0-3.0:10-120.

[0016] Furthermore, in step (1) when preparing the guiding agent, the crystallization under low temperature conditions refers to a temperature not higher than 120°C and a crystallization time not more than 10 hours, preferably a temperature of 90°C to 110°C and a time of 6 to 8 hours.

[0017] Furthermore, in step (2), when preparing gel II, the aluminum source is represented by Al2O3, the silicon source by SiO2, the phosphorus source by H3PO4, and the template agent by R. Then the molar ratio of Al2O3:SiO2:P2O5:R:H2O is 1:0-1.5:0.01-2.0:0-0.8:10-120.

[0018] Further, in step (3), the mass of the added directing agent is 5 wt% to 60 wt% of the mass of gel II, preferably 15 wt% to 50 wt%.

[0019] Furthermore, in step (3), the pH is adjusted to 6-11. Ammonia water can be used to adjust the pH.

[0020] Furthermore, in step (3), the hydrothermal crystallization conditions are: temperature of 150-250℃ and time of 10-60 hours.

[0021] Furthermore, in step (3), the product after hydrothermal crystallization is subjected to conventional post-treatment, such as cooling, filtration, washing, drying and calcination, to obtain SAPO-34 molecular sieve.

[0022] The second aspect of the present invention provides SAPO-34 molecular sieve obtained by the preparation method of the first aspect described above.

[0023] The SAPO-34 molecular sieve has a regular cubic crystal morphology with a grain size of no more than 800 nanometers, and is concentrated in the range of 100 to 600 nanometers.

[0024] The third aspect of this invention provides the application of SAPO-34 molecular sieve obtained by the preparation method provided in the first aspect in the methanol-to-olefins reaction.

[0025] Furthermore, the conditions for the methanol-to-olefins reaction are: temperature 400–700°C, pressure 0.1 MPa–3 MPa, and methanol feed weight hourly space velocity (WHSV) of 1–10 h⁻¹. -1 .

[0026] Compared with the prior art, the present invention has the following advantages:

[0027] The method for preparing SAPO-34 molecular sieve of this invention requires a small amount of template agent, or even none at all, thus effectively solving the problems of high cost of SAPO-34 molecular sieve and subsequent mother liquor wastewater treatment. Simultaneously, it effectively transforms a complex, decommissioned MTO catalyst into the target molecular sieve. Furthermore, the prepared molecular sieve has a smaller and more uniform particle size distribution, exhibiting high diene yields when applied to methanol-to-olefins reactions. Attached Figure Description

[0028] Figure 1The XRD pattern of SAPO-34 molecular sieve D prepared in Example 4;

[0029] Figure 2 SEM image of SAPO-34 molecular sieve D prepared in Example 4;

[0030] Figure 3 SEM image of SAPO-34 molecular sieve E prepared for Comparative Example 1;

[0031] Figure 4 SEM image of SAPO-34 molecular sieve H prepared for Comparative Example 4. Detailed Implementation

[0032] As one embodiment of the present invention, it should be noted that the scope of protection of the present invention is not limited to these specific embodiments.

[0033] The present invention will be further illustrated below through specific embodiments.

[0034] In this invention, XRD data were measured using a Bruker AXS D8 Advance X-ray diffractometer (Germany) to characterize the crystal structure of the molecular sieve and to calculate its relative crystallinity; SEM images were obtained using a FEI Quanta 200F field emission scanning electron microscope (Netherlands) to characterize the morphology of the molecular sieve.

[0035] In this invention, particle size distribution data were measured using a Malvern Mastersizer 2000 laser particle size analyzer to characterize the particle size distribution of the molecular sieve.

[0036]

Example 1

[0037] MTO catalyst after service:

[0038] The catalyst after service was selected from spent catalyst collected from the cyclone separator or slurry tank of the methanol-to-olefins industrial plant. The catalyst composition was 45% (by weight) SAPO-34 molecular sieve, 45% (by weight) kaolin, and 10% (by weight) binder.

[0039] Preparation of directing agents:

[0040] The above-mentioned degraded MTO catalyst was mixed with silica sol, alumina, phosphoric acid, tetraethylammonium hydroxide, and triethylamine (molar ratio of triethylamine to tetraethylammonium hydroxide was 3:1), and an initial gel I was prepared according to the ratio Al2O3:SiO2:P2O5:template:H2O = 1:1.0:0.8:3.0:60. The initial gel I was crystallized at 100℃ for 8 hours. After crystallization, the crystallized product was cooled to obtain the directing agent.

[0041] Preparation of SAPO-34 molecular sieve:

[0042] Using silica sol (30 wt% SiO2), pseudoboehmite (70 wt% Al2O3), and phosphoric acid (85 wt% H3PO4) as silicon, aluminum, and phosphorus sources, respectively, and triethylamine (NEt3) as a template agent, the mixture was prepared in a molar ratio of Al2O3:SiO2:P2O5:NEt3:H2O = 1.0:0.2:0.8:0.6:50 to obtain gel II. Finally, the prepared directing agent was added, and ammonia was added to adjust the pH of the system to 8. The mixture was stirred for at least 2 hours, with the amount of directing agent added being 20 wt% of the mass of gel II. The mixture was then crystallized at 200℃ for 30 hours. After crystallization, the crystallized product was cooled, filtered, washed, and dried, and then calcined at 550℃ for 5 hours to obtain SAPO-34 molecular sieve, denoted as A. This molecular sieve exhibited a uniform particle size distribution, with a grain size of 200–600 nm.

[0043]

Example 2

[0044] MTO catalyst after service:

[0045] The catalyst after service was selected from spent catalyst collected from the cyclone separator or slurry tank of the methanol-to-olefins industrial plant. The catalyst composition was 45% (by weight) SAPO-34 molecular sieve, 45% (by weight) kaolin, and 10% (by weight) binder.

[0046] Preparation of directing agents:

[0047] The above-mentioned degraded MTO catalyst was mixed with silica sol, alumina, phosphoric acid, tetraethylammonium hydroxide, and triethylamine (molar ratio of triethylamine to tetraethylammonium hydroxide was 1:1) and prepared as initial gel I according to the ratio Al2O3:SiO2:P2O5:template:H2O = 1:0.8:0.8:1.5:60. Initial gel I was crystallized at 100℃ for 8 hours. After crystallization, the crystallized product was cooled to obtain the directing agent.

[0048] Preparation of SAPO-34 molecular sieve:

[0049] Using boehmite (70 wt% Al2O3) and phosphoric acid (85 wt% H3PO4) as aluminum and phosphorus sources respectively, and triethylamine (NEt3) as a template agent, the mixture was prepared by mixing in a molar ratio of Al2O3:P2O5:NEt3:H2O = 1.0:1.0:0.6:50 to obtain gel II. Finally, the prepared directing agent was added, and ammonia was added to adjust the pH of the system to 8. The mixture was stirred for at least 2 hours, with the amount of directing agent added being 30 wt% of the mass of gel II. The mixture was then crystallized at 200℃ for 30 hours. After crystallization, the crystallized product was cooled, filtered, washed, and dried, and then calcined at 550℃ for 5 hours to obtain SAPO-34 molecular sieve, denoted as A. This molecular sieve exhibited a uniform particle size distribution, with crystal sizes ranging from 100 to 600 nanometers.

[0050]

Example 3

[0051] MTO catalyst after service:

[0052] The catalyst after service was selected from spent catalyst collected from the cyclone separator or slurry tank of the methanol-to-olefins industrial plant. The catalyst composition was 48% (by weight) SAPO-34 molecular sieve, 42% (by weight) kaolin, and 10% (by weight) binder.

[0053] Preparation of directing agents:

[0054] The above-mentioned degraded MTO catalyst was mixed with silica sol, alumina, phosphoric acid, tetraethylammonium hydroxide, and triethylamine (molar ratio of triethylamine to tetraethylammonium hydroxide was 1:2), and an initial gel I was prepared according to the ratio Al2O3:SiO2:P2O5:template:H2O = 1:0.8:0.8:1.0:60. The initial gel I was crystallized at 100℃ for 8 hours. After crystallization, the crystallized product was cooled to obtain the directing agent.

[0055] Preparation of SAPO-34 molecular sieve:

[0056] Using boehmite (70 wt% Al₂O₃) and phosphoric acid (85 wt% H₃PO₄) as aluminum and phosphorus sources respectively, and triethylamine (NEt₃) as a template agent, the mixture was prepared at a molar ratio of Al₂O₃:P₂O₅:NEt₃:H₂O = 1.0:1.0:0.4:50 to obtain gel II. The amount of directing agent added was 40 wt% of the mass of gel II. The mixture was crystallized at 200 °C for 30 hours. After crystallization, the crystallized product was cooled, filtered, washed, and dried, and then calcined at 550 °C for 5 hours to obtain SAPO-34 molecular sieve, denoted as C. This molecular sieve has a uniform particle size distribution, with a grain size of 200–600 nm.

[0057]

Example 4

[0058] MTO catalyst after service:

[0059] The catalyst after service was selected from spent catalyst collected from the cyclone separator or slurry tank of the methanol-to-olefins industrial plant. The catalyst composition was 45% (by weight) SAPO-34 molecular sieve, 45% (by weight) kaolin, and 10% (by weight) binder.

[0060] Preparation of directing agents:

[0061] The above-mentioned degraded MTO catalyst was mixed with silica sol, alumina, phosphoric acid, tetraethylammonium hydroxide, and triethylamine (molar ratio of triethylamine to tetraethylammonium hydroxide was 1:2), and an initial gel I was prepared according to the ratio Al2O3:SiO2:P2O5:template:H2O = 1:1.0:0.8:3.0:60. The initial gel I was crystallized at 100℃ for 8 hours. After crystallization, the crystallized product was cooled to obtain the directing agent.

[0062] Preparation of SAPO-34 molecular sieve:

[0063] Using boehmite (70 wt% Al₂O₃) and phosphoric acid (85 wt% H₃PO₄) as aluminum and phosphorus sources respectively, they were mixed in a molar ratio of Al₂O₃:P₂O₅:H₂O = 1.0:0.8:50 to obtain gel II. Finally, a directed agent was added, and ammonia was added to adjust the pH of the system to 8. The mixture was stirred for at least 2 hours, with the amount of directed agent added being 50 wt% of the mass of gel II. The mixture was then crystallized at 200℃ for 30 hours. After crystallization, the crystallized product was cooled, filtered, washed, and dried, and then calcined at 550℃ for 5 hours to obtain SAPO-34 molecular sieve, denoted as D. This molecular sieve exhibits a uniform particle size distribution, with crystal sizes ranging from 100 to 600 nanometers.

[0064] Comparative Example 1

[0065] A mixed gel was prepared by mixing silica sol (30 wt% SiO2), pseudoboehmite (70 wt% Al2O3), and phosphoric acid (85 wt% H3PO4) as silicon, aluminum, and phosphorus sources, respectively, and triethylamine (NEt3) as a template agent, according to a molar ratio of Al2O3:SiO2:P2O5:NEt3:H2O = 1.0:0.4:1.2:3.0:50. The mixture was then crystallized at 200℃ for 40 hours. After crystallization, the crystallized product was cooled, filtered, washed, and dried, and then calcined at 550℃ for 5 hours to obtain SAPO-34 molecular sieve, denoted as E. This molecular sieve has a relatively large crystal size, ranging from 2 to 10 micrometers.

[0066] Comparative Example 2

[0067] A mixed gel was prepared by mixing silica sol (30 wt% SiO2), pseudoboehmite (70 wt% Al2O3), and phosphoric acid (85 wt% H3PO4) as silicon, aluminum, and phosphorus sources, respectively, and triethylamine (NEt3) as a template agent, in a molar ratio of Al2O3:SiO2:P2O5:NEt3:H2O = 1.0:0.4:1.2:0.5:50. The mixture was then crystallized at 200 °C for 40 hours. The resulting product was an amorphous species, denoted as F.

[0068] Comparative Example 3

[0069] Same as [Comparative Example 2], except that triethylamine NEt3 template agent was not added when preparing SAPO-34 molecular sieve, and the resulting product was an amorphous species, denoted as G.

[0070] Comparative Example 4

[0071] Same as in Example 1, except that the initial gel I was crystallized at 150°C for 8 hours during the preparation of the directing agent. The obtained SAPO-34 molecular sieve is denoted as H. The particle size distribution of this molecular sieve is non-uniform, with crystal sizes ranging from 100 nanometers to 5 micrometers.

[0072]

Example 5

[0073] The molecular sieves obtained in Examples 1-4, Comparative Example 1, and Comparative Example 4 were used to prepare fluidized bed catalysts for methanol-to-olefins reaction. A fixed fluidized bed catalytic reactor with a stainless steel tube was used. The process conditions investigated were: catalyst loading of 40.0 g, reaction temperature of 480 °C, and weight hourly space velocity of 6 h⁻¹. -1 The pressure was 0.1 MPa, and the evaluation results are shown in Table 1. It can be seen that the comprehensively modified catalyst significantly improves the diene yield in the methanol-to-olefins reaction, and the catalyst exhibits good stability. In this invention, the yields of each product are expressed by mass.

[0074] Table 1

[0075]

[0076] The specific embodiments of the present invention have been described in detail above, but the present invention is not limited thereto. Within the scope of the technical concept of the present invention, various simple modifications can be made to the technical solutions of the present invention, including combining the 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 method for preparing SAPO-34 molecular sieve, characterized in that, include: (1) Using the decoupled MTO catalyst after its service life to prepare the directing agent; (2) Aluminum source, phosphorus source, water, and selectively added silicon source and selectively added template agent are mixed to prepare gel II; (3) Mix the directing agent prepared in step (1) with the gel II prepared in step (2), adjust the pH, and carry out hydrothermal crystallization to obtain SAPO-34 molecular sieve; Step (1) The method for preparing the directing agent includes: preparing an initial gel I by combining the in-service MTO catalyst with an aluminum source, a silicon source, a phosphorus source, a template agent, and water; Then, the initial gel I was crystallized at low temperature to prepare the directing agent; When preparing the directing agent in step (1), the crystallization under low temperature conditions refers to a temperature not higher than 120°C and a crystallization time not more than 10 hours.

2. The preparation method according to claim 1, characterized in that, The MTO catalyst after service comprises, by weight: 20%~60% SAPO-34 molecular sieve, 30%~50% kaolin, and 5%~20% binder.

3. The preparation method according to claim 1, characterized in that, The aluminum source is one or more of alumina, boehmite, and aluminum isopropoxide; the silicon source is one or more of silica sol, tetraethyl orthosilicate, and silica; the phosphorus source is one or more of phosphoric acid, phosphate, and phosphorous acid; and the template agent is one or more of morpholine, triethylamine, and tetraethylammonium hydroxide.

4. The preparation method according to claim 3, characterized in that, The template agent is one or more of triethylamine and tetraethylammonium hydroxide.

5. The preparation method according to claim 1, characterized in that, In step (1), when preparing the directing agent, the aluminum source is represented by Al2O3, the silicon source by SiO2, the phosphorus source by H3PO4, and the template agent is represented by R. Then the molar ratio of Al2O3:SiO2:P2O5:R:H2O is 1:0.1-1.5:0.01-2.0:1.0-3.0:10-120.

6. The preparation method according to claim 1, characterized in that, In step (1), when preparing the guiding agent, the crystallization temperature is 90℃~110℃ and the crystallization time is 6~8h.

7. The preparation method according to claim 1, characterized in that, In step (2), when preparing gel II, the aluminum source is represented by Al2O3, the silicon source by SiO2, the phosphorus source by H3PO4, and the template agent by R. The molar ratio of Al2O3:SiO2:P2O5:R:H2O is 1:0-1.5:0.01-2.0:0-0.8:10-120.

8. The preparation method according to claim 1, characterized in that, In step (3), the mass of the added directing agent is 5wt% to 60wt% of the mass of gel II.

9. The preparation method according to claim 8, characterized in that, In step (3), the mass of the added directing agent is 15wt% to 50wt% of the mass of gel II.

10. The preparation method according to claim 1, characterized in that, In step (3), the pH is adjusted to 6-11; the hydrothermal crystallization conditions are: temperature 150-250℃, time 10-60 hours.

11. A SAPO-34 molecular sieve, characterized in that, Prepared using the method described in any one of claims 1-10.

12. An application of the SAPO-34 molecular sieve according to claim 11 in the methanol-to-olefins reaction.

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