Preparation method and application of SAPO-34 molecular sieve

Abstract

The application provides a preparation method and application of SAPO-34 molecular sieve. The preparation method of the SAPO-34 molecular sieve provided by the application comprises the following steps: S1, activating a used methanol-to-olefin catalyst; S2, mixing the activated catalyst with an acid solution to obtain a first mixture; S3, performing solid-liquid separation on the first mixture to obtain a liquid phase and a solid phase; and S4, mixing the liquid phase with an aluminum source, a phosphorus source, a silicon source and a template agent to obtain a second mixture, and performing crystallization treatment on the second mixture. The SAPO-34 molecular sieve prepared by the application can be used in a methanol-to-olefin reaction, and can exhibit excellent low-carbon olefin selectivity and a longer catalyst service life.

Description

Technical Field

[0001] This invention belongs to the field of catalysts, specifically relating to a method for preparing SAPO-34 molecular sieve and its application. Background Technology

[0002] SAPO molecular sieves are crystalline network structures composed of AlO4, SiO4, and PO4 tetrahedra. The pores within the crystal are due to Si... 4+ Replace P 5+ Or Al 3+ The acidity is produced by substitution with metals. Among the SAPO series of molecular sieves, SAPO-34 molecular sieve is widely used in modern petroleum processing industry due to its good thermal and hydrothermal stability, moderate acidity, high specific surface area, and highly ordered microporous channels. Most notably, this molecular sieve is used as an active component in the methanol-to-olefins (MTO) reaction, enabling near-complete conversion of methanol, with selectivity for ethylene and propylene exceeding 80%, and C5... + The components are present in small amounts, and almost no aromatics are generated.

[0003] Generally, the synthesis of SAPO-34 molecular sieves requires the addition of template agents in addition to conventional chemical reagents such as silicon, aluminum, and phosphorus sources. Commonly used template agents are organic amine species such as morpholine, triethylamine, and tetraethylammonium hydroxide. Organic amines not only act as templates in the synthesis of molecular sieves but also provide a suitable environment for the system. Therefore, broadening the sources of raw materials for molecular sieve synthesis can expand the scope of utilization of chemical raw materials and reduce the synthesis cost of molecular sieves to a certain extent. In addition, regarding the utilization of methanol-to-olefins (MTO) catalysts after service, CN201410575041.3 proposes a method for adsorbing and removing methanol using waste SAPO-34 molecular sieve catalysts, and CN201410573567.8 proposes a method for preparing adsorbents and removing methanol from spent molecular sieve catalysts. This method involves preparing adsorbents from spent SAPO-34 catalysts 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, these methods still suffer from the problem of low utilization rate of the MTO catalyst after service and the inability to recycle it as a catalyst. CN201811433062.6 describes a method that uses two-stage calcination, employing ammonium aluminum sulfate decomposition and acid hydrolysis ripening to obtain alumina and silicon-phosphorus-nitrogen compound fertilizer. This method is energy-intensive and yields products with low added value.

[0004] In summary, how to broaden the range of raw materials for molecular sieve synthesis and fully utilize the resources of methanol-to-olefins catalysts after their service life has always been a hot research topic for researchers. Summary of the Invention

[0005] To address the problems existing in the prior art, this invention provides a novel method for preparing SAPO-34 molecular sieve and a method for resource utilization of post-use MTO catalysts. The method provided by this invention enables the resource utilization of post-service MTO catalysts, efficiently and environmentally solving the problem of MTO catalyst utilization. Simultaneously, the prepared SAPO-34 molecular sieve maintains high catalytic performance when applied to the methanol-to-olefins reaction.

[0006] In a first aspect, the method for preparing SAPO-34 molecular sieve provided by the present invention includes:

[0007] S1: Activate the used methanol-to-olefins catalyst;

[0008] S2: The activated catalyst is mixed with an acid solution to obtain the first mixture;

[0009] S3: Perform solid-liquid separation on the first mixture to obtain a liquid phase and a solid phase;

[0010] S4: The liquid phase is mixed with an aluminum source, a phosphorus source, a silicon source and a template agent to obtain a second mixture, and the second mixture is subjected to crystallization treatment.

[0011] In some embodiments, in step S2, the mass ratio of the catalyst to the acid solution is 1:(2-10), for example, 1:2.5, 1:3, 1:3.5, 1:4, 1:4.5, 1:5, 1:5.5, 1:6, 1:6.5, 1:7, 1:7.5, 1:8, 1:8.5, 1:9, 1:9.5, or any value between them. In some embodiments, in step S2, the mass ratio of the catalyst to the acid solution is 1:(3-8). In some embodiments, the mass ratio of the catalyst to the acid solution is 1:(4-6). After activation treatment, the catalyst, after treatment with an appropriate amount of acid, can synthesize a molecular sieve with high crystallinity, which is beneficial to improving its catalytic performance.

[0012] In some embodiments, in S2, the mixing temperature is 100°C-180°C, for example, 110°C, 110°C, 115°C, 120°C, 125°C, 130°C, 135°C, 140°C, 145°C, 150°C, 155°C, 160°C, 165°C, 170°C, 175°C, or any value between them. In some embodiments, in S2, the mixing temperature is 120°C-150°C.

[0013] In some embodiments, the mixing time in S2 is 2h-24h, for example, 4h, 6h, 8h, 10h, 12h, 14h, 16h, 18h, 20h, or 22h. In some embodiments, the mixing time in S2 is 5h-20h.

[0014] In some embodiments, in S2, the acid solution is selected from one or more inorganic acid solutions. In some embodiments, the inorganic acid solution is an aqueous solution of an inorganic acid. In some embodiments, in S2, the acid solution is selected from one or more of phosphoric acid, sulfuric acid, and hydrochloric acid.

[0015] In some embodiments, the concentration of the acid solution is 0.5 mol / L to 7 mol / L, for example, 1 mol / L, 1.5 mol / L, 2 mol / L, 2.5 mol / L, 3 mol / L, 3.5 mol / L, 4 mol / L, 4.5 mol / L, 5 mol / L, 5.5 mol / L, 6 mol / L, or 6.5 mol / L. In some embodiments, the concentration of the acid solution is 2 mol / L to 6 mol / L.

[0016] In some embodiments, the used methanol-to-olefins catalyst is selected from used methanol-to-olefins catalysts.

[0017] In some embodiments, the decommissioned methanol-to-olefins catalyst is selected from fine powder obtained from a cyclone separator in an industrial methanol-to-olefins unit or from a catalyst obtained from a settling tank.

[0018] In some embodiments, the used methanol-to-olefins catalyst comprises SAPO-34 molecular sieve.

[0019] In some embodiments, in S1, the activation treatment includes calcining the used methanol-to-olefins catalyst in an air atmosphere. In some embodiments, the calcination temperature is 600°C-800°C. In some embodiments, the calcination time is 2 hours-6 hours.

[0020] In some embodiments, in S3, the solid-liquid separation includes filtration or centrifugation.

[0021] In some embodiments, in S4, the liquid phase is first mixed with the aluminum source and the phosphorus source, and then mixed with the silicon source and the template agent to obtain the second mixture.

[0022] In some embodiments, in step S4, the crystallization treatment temperature is 150°C-250°C, for example, 170°C, 200°C, or 220°C. In some embodiments, in step S4, the crystallization treatment time is 10h-60h.

[0023] In some embodiments, in S4, the aluminum source is calculated as Al2O3, the silicon source as SiO2, and the phosphorus source as P2O5. In the second mixture, the molar ratio of aluminum source: silicon source: phosphorus source: template agent: water is 1:(0-1.5):(0.01-2.0):(0.05-3.0):(10-120).

[0024] In some implementations, in S4, the molar ratio of aluminum source to silicon source is 1:0.1, 1:0.3, 1:0.5, 1:0.7, 1:1, or 1:1.3.

[0025] In some embodiments, in S4, the molar ratio of aluminum source to phosphorus source is 1:0.1, 1:0.3, 1:0.5, 1:0.7, 1:1, 1:1.3, 1:1.5 or 1:1.7.

[0026] In some embodiments, in S4, the molar ratio of aluminum source to template agent is 1:0.1, 1:0.3, 1:0.5, 1:0.7, 1:1, 1:1.3, 1:1.5, 1:1.7, 1:2, 1:2.3, 1:2.5 or 1:2.7.

[0027] In some embodiments, in S4, the molar ratio of aluminum source to water is 1:20, 1:30, 1:40, 1:50, 1:60, 1:70, 1:80, 1:90, 1:100, or 1:110.

[0028] In some embodiments, the aluminum source is selected from one or more of alumina, boehmite, aluminum isopropoxide, aluminum nitrate, aluminum chloride, and aluminum sulfate.

[0029] In some embodiments, the phosphorus source is selected from one or more of phosphoric acid, ammonium phosphate, diammonium hydrogen phosphate, ammonium hydrogen phosphate, potassium phosphate, dipotassium hydrogen phosphate, potassium hydrogen phosphate, sodium phosphate, disodium hydrogen phosphate, and sodium hydrogen phosphate.

[0030] In some embodiments, the silicon source is selected from one or more of silica sol, silica, and tetraethyl orthosilicate.

[0031] In some embodiments, the template agent is selected from one or more of morpholine, triethylamine, and tetraethylammonium hydroxide.

[0032] In some embodiments, conventional post-processing steps such as separation, washing, and drying can be performed after crystallization. These processes can employ conventional methods; for example, separation can be achieved through centrifugation, washing can be done with deionized water, and drying can be carried out in an oven. For instance, drying conditions may include drying at 30°C-120°C for 2-20 hours.

[0033] In some embodiments, the preparation method of the SAPO-34 molecular sieve of the present invention includes the following specific steps: the used methanol-to-olefins catalyst is first activated at high temperature and then added to an acidic solution for treatment; then the solid and liquid are separated by centrifugation or filtration to obtain a supernatant; supplementary aluminum source and phosphorus source are added to the supernatant to form initial gel I; finally, silicon source and template agent are added to initial gel I to prepare initial gel II, and then SAPO-34 molecular sieve is prepared under conventional hydrothermal conditions.

[0034] Secondly, the present invention provides a SAPO-34 molecular sieve prepared by the preparation method described in the first aspect.

[0035] Thirdly, the present invention provides the application of the SAPO-34 molecular sieve prepared by the preparation method described in the first aspect in the methanol-to-olefins reaction.

[0036] In some embodiments, the reaction conditions for the methanol-to-olefins reaction are: a reaction pressure of 0.1 MPa-1.0 MPa, a reaction temperature of 400℃-700℃, and a methanol feed weight hourly space velocity of 1 h⁻¹. -1 -10h -1 .

[0037] Compared with the prior art, the present invention has the following advantages:

[0038] 1. It broadens the range of raw materials for molecular sieve synthesis.

[0039] 2. Effectively solves the problem of disposing of methanol-to-olefins catalysts after use.

[0040] 3. The prepared molecular sieve has good crystallization properties and exhibits good catalytic performance in the methanol-to-olefins reaction. The yield of diene (ethylene + propylene) can be comparable to or better than that of existing technologies, achieving good technical results. Detailed Implementation

[0041] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments. The specific embodiments described herein are for illustrative purposes only and are not intended to limit the invention in any way. Furthermore, descriptions of well-known structures and techniques are omitted in the following description to avoid unnecessarily obscuring the concepts of this disclosure. Such structures and techniques have also been described in many publications.

[0042] 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.

[0043] The present invention will be further described below with reference to embodiments, but the embodiments do not limit the scope of protection of the present invention.

[0044] The catalyst used in this invention is selected from spent catalyst collected from the cyclone separator or slurry tank of a methanol-to-olefins industrial plant. The catalyst composition is 45% (by weight) SAPO-34 molecular sieve: 45% (by weight) kaolin: 10% (by weight) binder. The SAPO-34 molecular sieve has a composition of Al2O3:SiO2:P2O5 = 60:20:20.

[0045] Example 1

[0046] Step 1) Activation treatment:

[0047] The catalyst after service was placed in a muffle furnace and air was introduced at a flow rate of 30 mL / min. The temperature was raised to 600 °C and treated for 4 hours.

[0048] Step 2) Treatment of the activated catalyst:

[0049] 15g of the activated catalyst was added to 85g of phosphoric acid solution (4mol / L), and the treatment was carried out at 120℃ for 12 hours. After treatment, the solid and liquid were separated by centrifugation, and the supernatant was used for subsequent molecular sieve synthesis.

[0050] Step 3) Preparation of SAPO-34 molecular sieve:

[0051] Silica sol (30 wt% SiO2), pseudoboehmite (70 wt% Al2O3), and phosphoric acid (85 wt% H3PO4) were used as supplementary silicon, aluminum, and phosphorus sources, respectively. A mixture of tetraethylammonium hydroxide and triethylamine was added as a template agent to the clear solution in step 2). A mixed gel was prepared according to the ratio of Al2O3:SiO2:P2O5:template agent:H2O = 1:0.3:0.8:2.4:50, wherein the mass ratio of triethylamine to tetraethylammonium hydroxide was 3:1. The mixed gel was crystallized at 200℃ for 48 h. After crystallization, the crystallized product was cooled, filtered, washed, and dried, and then calcined at 550℃ for 5 h to obtain SAPO-34 molecular sieve.

[0052] Example 2

[0053] Step 1) Activation treatment:

[0054] The catalyst after service was placed in a muffle furnace and air was introduced at a flow rate of 30 mL / min. The temperature was raised to 600 °C and treated for 4 hours.

[0055] Step 2) Treatment of the activated catalyst:

[0056] 15g of the activated catalyst was added to 75g of hydrochloric acid solution (6mol / L), and the treatment temperature was 150℃ for 8 hours. After treatment, the solid and liquid were separated by centrifugation, and the supernatant was used for subsequent molecular sieve synthesis.

[0057] Step 3) Preparation of SAPO-34 molecular sieve:

[0058] Silica sol (30 wt% SiO2), pseudoboehmite (70 wt% Al2O3), and phosphoric acid (85 wt% H3PO4) were used as supplementary silicon, aluminum, and phosphorus sources, respectively. A mixture of tetraethylammonium hydroxide and triethylamine was added as a template agent to the clear solution in step 2). A mixed gel was prepared according to the ratio of Al2O3:SiO2:P2O5:template agent:H2O = 1:0.3:0.8:2.4:50, wherein the mass ratio of triethylamine to tetraethylammonium hydroxide was 3:1. The mixed gel was crystallized at 200℃ for 48 h. After crystallization, the crystallized product was cooled, filtered, washed, and dried, and then calcined at 550℃ for 5 h to obtain SAPO-34 molecular sieve.

[0059] Example 3

[0060] Step 1) Activation treatment:

[0061] The catalyst after service was placed in a muffle furnace and air was introduced at a flow rate of 30 mL / min. The temperature was raised to 600 °C and treated for 4 hours.

[0062] Step 2) Treatment of the activated catalyst:

[0063] 15g of the activated catalyst was added to 100g of sulfuric acid solution (2mol / L concentration), and the treatment temperature was 100℃ for 20 hours. After treatment, the solid and liquid were separated by centrifugation, and the supernatant was used for subsequent molecular sieve synthesis.

[0064] Step 3) Preparation of SAPO-34 molecular sieve:

[0065] Silica sol (30 wt% SiO2), pseudoboehmite (70 wt% Al2O3), and phosphoric acid (85 wt% H3PO4) were used as supplementary silicon, aluminum, and phosphorus sources, respectively. A mixture of tetraethylammonium hydroxide and triethylamine was added as a template agent to the clear solution in step 2). A mixed gel was prepared according to the ratio of Al2O3:SiO2:P2O5:template agent:H2O = 1:0.3:0.8:2.4:50, wherein the mass ratio of triethylamine to tetraethylammonium hydroxide was 3:1. The mixed gel was crystallized at 200℃ for 48 h. After crystallization, the crystallized product was cooled, filtered, washed, and dried, and then calcined at 550℃ for 5 h to obtain SAPO-34 molecular sieve.

[0066] Example 4

[0067] The only difference between Example 4 and Example 2 is that in step 2), 15g of the activated catalyst is added to 45g of hydrochloric acid solution.

[0068] Example 5

[0069] The only difference between Example 5 and Example 2 is that in step 2), 15g of the activated catalyst is added to 120g of hydrochloric acid solution.

[0070] Example 6

[0071] The only difference between Example 6 and Example 2 is that the acid solution treatment temperature in step 2) is 120°C.

[0072] Example 7

[0073] The only difference between Example 7 and Example 2 is that the acid solution treatment temperature in step 2) is 160°C.

[0074] Example 8

[0075] The difference between Example 8 and Example 2 is only that in step 3), boehmite and phosphoric acid are first added to the clear liquid in step 2) to obtain the first gel, and then silica sol, triethylamine and tetraethylammonium hydroxide are added to the first gel to obtain a mixed gel.

[0076] Comparative Example 1

[0077] Preparation of SAPO-34 molecular sieve:

[0078] 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 and tetraethylammonium hydroxide as mixed template agents, wherein the mass ratio of triethylamine to tetraethylammonium hydroxide was 3:1. The mixture was prepared according to the molar ratio of Al2O3:SiO2:P2O5:template:H2O = 1:0.3:0.8:2.4:50, and the mixture was crystallized at 200℃ for 48 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.

[0079] Comparative Example 2

[0080] Step 1) Activation treatment:

[0081] The catalyst after service was placed in a muffle furnace and air was introduced at a flow rate of 30 mL / min. The temperature was raised to 600 °C and treated for 4 hours.

[0082] Step 2) Preparation of SAPO-34 molecular sieve:

[0083] The activated catalyst was added to deionized water and stirred. Boehmite was added as a supplementary aluminum source, phosphoric acid as a supplementary phosphorus source, and triethylamine and tetraethylammonium hydroxide were used as a mixed template agent, with a mass ratio of triethylamine to tetraethylammonium hydroxide of 3:1. The mixture was prepared by mixing Al₂O₃:SiO₂:P₂O₅:template agent:H₂O = 1:0.3:0.8:2.4:50 to obtain a mixed gel. The mixture was crystallized at 200℃ for 48 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.

[0084] Test case

[0085] The molecular sieves obtained in the above examples and comparative examples were used to prepare fluidized bed catalysts for methanol-to-olefins reactions. A fixed fluidized bed catalytic reactor was used, with a stainless steel tube reactor. 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. In this invention, the yield of each product is expressed by mass.

[0086] The diene yield is the sum of the ethylene and propylene yields, both of which are calculated by gas chromatography.

[0087] Catalyst lifetime refers to the time at which diene selectivity reaches its maximum.

[0088] Table 1

[0089]

[0090] As can be seen from the data in Table 1, the catalyst prepared using the supernatant of the treated methanol-to-olefins catalyst after service as raw material can significantly improve the diene yield in the methanol-to-olefins reaction, and the catalyst has good stability.

[0091] 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 method for preparing SAPO-34 molecular sieve, comprising: S1: Activate the used methanol-to-olefins catalyst; S2: The activated catalyst is mixed with an acid solution to obtain a first mixture; the mass ratio of the catalyst to the acid solution is 1:(4-6); the mixing temperature is 120℃-150℃; S3: Perform solid-liquid separation on the first mixture to obtain a liquid phase and a solid phase; S4: The liquid phase is mixed with an aluminum source, a phosphorus source, a silicon source and a template agent to obtain a second mixture, and the second mixture is subjected to crystallization treatment.

2. The preparation method according to claim 1, characterized in that, In S2, the mixing time is 2h-24h.

3. The preparation method according to claim 1, characterized in that, In S2, the mixing time is 5h-20h.

4. The preparation method according to claim 1, characterized in that, In S2, the acid solution is selected from one or more inorganic acid solutions; and / or The concentration of the acid solution is 0.5 mol / L to 7 mol / L.

5. The preparation method according to claim 1, characterized in that, In S2, the acid solution is selected from one or more of phosphoric acid, sulfuric acid, and hydrochloric acid.

6. The preparation method according to claim 1, characterized in that, In S2, the concentration of the acid solution is 2 mol / L-6 mol / L.

7. The preparation method according to claim 1, characterized in that, The used methanol-to-olefins catalyst is selected from methanol-to-olefins catalysts that have been decommissioned; and / or The used methanol-to-olefins catalyst contains SAPO-34 molecular sieve.

8. The preparation method according to claim 1, characterized in that, The used methanol-to-olefins catalyst is selected from fine powder obtained from the cyclone separator of an industrial methanol-to-olefins unit or catalyst obtained from the settling tank.

9. The preparation method according to claim 1, characterized in that, In S1, the activation treatment includes calcining the used methanol-to-olefins catalyst in an air atmosphere; and / or In S3, the solid-liquid separation includes filtration or centrifugation.

10. The preparation method according to claim 9, characterized in that, In S1, the calcination temperature is 600℃-800℃, and the calcination time is 2h-6h.

11. The preparation method according to claim 1, characterized in that, In S4, the liquid phase is first mixed with the aluminum source and the phosphorus source, and then mixed with the silicon source and the template agent to obtain the second mixture; and / or In S4, the temperature of the crystallization treatment is 150℃-250℃, and the time of the crystallization treatment is 10h-60h.

12. The preparation method according to claim 1, characterized in that, The aluminum source is calculated as Al2O3, the silicon source as SiO2, and the phosphorus source as P2O5. In the second mixture, the molar ratio of aluminum source: silicon source: phosphorus source: template agent: water is 1:(0-1.5):(0.01-2.0):(0.05-3.0):(10-120); and / or The aluminum source is selected from one or more of alumina, boehmite, aluminum isopropoxide, aluminum nitrate, aluminum chloride, and aluminum sulfate; and / or The phosphorus source is selected from one or more of phosphoric acid, ammonium phosphate, ammonium hydrogen phosphate, potassium phosphate, potassium hydrogen phosphate, sodium phosphate, and sodium hydrogen phosphate; and / or The silicon source is selected from one or more of silica sol, silica, and tetraethyl orthosilicate; and / or The template agent is selected from one or more of morpholine, triethylamine, and tetraethylammonium hydroxide.

13. The application of the SAPO-34 molecular sieve prepared by any one of claims 1-12 in the methanol-to-olefins reaction.

14. The application according to claim 13, characterized in that, The reaction conditions for the methanol-to-olefins reaction are as follows: reaction pressure of 0.1 MPa-1.0 MPa, reaction temperature of 400℃-700℃, and methanol feed weight hourly space velocity of 1 h⁻¹. -1 -10h -1 .

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