A ZSM-23 molecular sieve and its preparation method and application

Abstract

The present invention provides a ZSM-23 molecular sieve and a preparation method thereof, wherein the mesoporous pore volume of the molecular sieve having a pore size of 3-8 nm accounts for 45-90% of the total pore volume of the molecular sieve; the relative crystallinity of the molecular sieve is 95-120%, and the relative crystallinity retention of the molecular sieve after 2 hours of hydrothermal treatment with 600 ° C of steam is 95-100%. The preparation method of the molecular sieve comprises the following steps: (1) preparing or selecting a silicon source, such as amorphous silica, for preparing the ZSM-23 molecular sieve; (2) alkali-treating the silicon source amorphous silica for preparing the ZSM-23 molecular sieve described in step (1); (3) preparing the ZSM-23 molecular sieve using the amorphous silica after alkali treatment as a silicon source. The ZSM-23 molecular sieve has a rich mesoporous structure and good hydrothermal stability.

Description

Technical Field

[0001] The present invention relates to a ZSM-23 molecular sieve and a preparation method and application thereof, and in particular to a mesopore-rich ZSM-23 molecular sieve and a preparation method and application thereof. Background Art

[0002] ZSM-23 molecular sieve is a high-silicon-to-aluminum molecular sieve material with an MTT topology, characterized by a one-dimensional teardrop-shaped pore structure composed of ten-membered rings. Due to its unique pore structure and tunable acidic properties, ZSM-23 molecular sieve is widely used in separation, adsorption, and catalysis, playing an irreplaceable role. In the petrochemical industry, it excels in hydrocracking of long-chain alkanes and olefins, and in isomerization of alkanes and aromatics. However, ZSM-23 is a microporous molecular sieve, and its pore size limits its ability to process larger molecules. Therefore, to further expand its application, it is important to prepare high-performance mesoporous ZSM-23 molecular sieves.

[0003] Among the currently disclosed patents, there are few technologies for introducing mesoporous structures into microporous ZSM-23 molecular sieves.

[0004] CN106513035 discloses a method for preparing a composite molecular sieve with a ZSM-23 molecular sieve as a core and an MCM-41 or SBA-15 shell. The mesopores in this method are provided by the mesoporous molecular sieves MCM-41 or SBA-15. Due to their inherent stability and limited silicon-to-aluminum ratio, the resulting composite molecular sieve also suffers from disadvantages such as poor stability and a narrow adjustable silicon-to-aluminum ratio.

[0005] CN105540607 discloses a method for preparing a multi-level pore composite molecular sieve ZSM-22 / ZSM-23. However, both ZSM-22 and ZSM-23 molecular sieves have microporous structures, so the mesoporous structure involved is mainly stacked pores, which have poor regularity and stability.

[0006] Patent CN107235497 introduces starch into the ZSM-23 molecular sieve synthesis pathway, which is then removed by calcination to produce a ZSM-23 molecular sieve with a hierarchical mesoporous-microporous composite structure. This method is simple and low-cost, but because the mesoporous structure is obtained by removing the pore-enlarging agent, it can affect thermal and hydrothermal stability.

[0007] Common methods for preparing micro-mesoporous composite molecular sieves include alkaline or acid post-treatment, hard template methods, and surfactant methods. Detailed processes have been reported numerous times in articles and patents. However, these methods can damage the microporous structure of the molecular sieve, resulting in poor product stability. Other factors include complex processes and high costs, making their application prospects uncertain.

[0008] Therefore, developing a mesoporous ZSM-23 molecular sieve with simple process, low cost and excellent product performance is a technical problem to be solved by those skilled in the art. Summary of the Invention

[0009] In order to overcome the deficiencies in the prior art, the present invention provides a ZSM-23 molecular sieve and a preparation method thereof, wherein the molecular sieve has a rich mesoporous structure and good hydrothermal stability.

[0010] The present invention provides a ZSM-23 molecular sieve, wherein the mesopore volume of the molecular sieve with a pore diameter of 3-8 nm, preferably 3-6 nm, accounts for 45-90%, preferably 50-85%, and more preferably 55-81% of the total pore volume of the molecular sieve; the relative crystallinity of the molecular sieve is 95-120%, and the relative crystallinity retention of the molecular sieve after hydrothermal treatment with water vapor at 600°C for 2 hours is 95-100%.

[0011] In the above molecular sieve, the specific surface area of ​​the molecular sieve is 300-430m 2 / g, pore volume of 0.31-0.5cm 3 / g, micropore specific surface area is 50-170m 2 / g, mesopore specific surface area is 150-310m 2 / g; preferably, the specific surface area is 320-405m 2 / g, pore volume is 0.34-0.45cm 3 / g, micropore specific surface area is 80-140m 2 / g, and the mesopore specific surface area is 261-295m 2 / g.

[0012] The present invention also provides a method for preparing ZSM-23 molecular sieve, which comprises the following steps:

[0013] (1) preparing or selecting a silicon source for preparing ZSM-23 molecular sieve, such as amorphous silicon dioxide;

[0014] (2) treating the silicon source used to prepare the ZSM-23 molecular sieve described in step (1) with an alkali;

[0015] (3) ZSM-23 molecular sieve was prepared using alkali-treated amorphous silica as the silicon source.

[0016] In step (1) of the above method, the silicon source used to prepare the ZSM-23 molecular sieve can be amorphous silica, or other silicon sources known in the art, such as one or more of fumed silica, silica sol and water glass.

[0017] In step (1) of the above method, the amorphous silicon dioxide has a specific surface area of ​​600-1300m 2 / g, preferably 700-1200m 2 / g; pore volume of 0.6-1.3cm 3 / g, preferably 0.7-1.2cm 3 / g; the pore diameter is 1-15 nm, preferably 2-10 nm.

[0018] In step (1) of the above method, the amorphous silica is prepared as follows: a silicon source is added to deionized water and dispersed evenly, and then a surfactant is added and stirred; the solution pH is adjusted to 1-5, preferably 1.5-4, and then heated in a water bath for a period of time; and amorphous silica is obtained after filtering, washing, drying, and calcining.

[0019] In the above method, during the preparation of the amorphous silicon dioxide, the silicon source is an inorganic silicon source, preferably one or more of water glass, silica sol or white carbon black.

[0020] In the above method, during the preparation of amorphous silicon dioxide, the surfactant is one or more of cetyltrimethylammonium chloride, cetyltrimethylammonium bromide, octadecyltrimethylammonium chloride, and octadecyltrimethylammonium bromide.

[0021] In the above method, during the preparation of the amorphous silica, the molar ratio of the silicon source calculated as SiO2 to the surfactant is 1:(0.02-0.3), preferably 1:(0.05-0.2).

[0022] In the above method, during the preparation of the amorphous silica, the molar ratio of the silicon source calculated as SiO2 to deionized water is 1:(30-300), preferably 1:(50-220).

[0023] In the above method, during the preparation of the amorphous silica, the heating temperature is 30-80°C, preferably 40-70°C, and the heating time is 0.5-8h, preferably 3-6h.

[0024] In step (2) of the above method, the alkali treatment is to add the amorphous silica prepared in step (1) into an alkaline solution and heat and stir.

[0025] In the above method, the alkali treatment adopts inorganic alkali treatment, and the inorganic alkali is one or more of sodium hydroxide, potassium hydroxide or ammonia water.

[0026] In the above method, the alkali treatment heating and stirring time is 0.5-12h, preferably 2-8h; the heating temperature is 25-60°C, preferably 30-50°C.

[0027] In the above method, OH - The molar ratio of the inorganic base to the amorphous silicon dioxide is 0.05-0.24, preferably 0.06-0.22. - The molar number of the inorganic base can be obtained by conventional analytical chemistry means, which will not be described in detail here.

[0028] In step (3) of the above method, in preparing the ZSM-23 molecular sieve using alkali-treated amorphous silica as the silicon source, any method known in the prior art for preparing the ZSM-23 molecular sieve may be used, or a method not yet known in the prior art but to be known in the future may be used. For example, a known method is disclosed in Rohrman Jr., AC, et al. "The framework topology of ZSM-23: A high silicazeolite." Zeolites 5.6 (1985): 352-354, US Pat. No. 4,076,842, US Pat. No. 5,405,596, US Pat. No. 5,707,601, and US Pat. No. 7,157,075.

[0029] In step (3) of the above method, preferably, alkali-treated amorphous silica is used as a silicon source, and the silicon source is mixed with an aluminum source, an alkali source (MOH), a template (R), and water to form a gel, which is then crystallized, filtered, washed, dried, and calcined to obtain a ZSM-23 molecular sieve;

[0030] More preferably, the molar ratio of silicon source (as SiO2): aluminum source (as Al2O3): alkali source (as hydroxide): template: H2O in the gel is 1: (0.003-0.03): (0.03-0.3): (0.05-2): (10-90); further preferably, the molar ratio of silicon source (as SiO2): aluminum source (as Al2O3): alkali source (as hydroxide): template: H2O in the gel is 1: (0.005-0.02): (0.03-0.16): (0.08-1.6): (20-70); and / or

[0031] More preferably, the gel is crystallized at 150-200°C, preferably 170-180°C, for 24-96h, preferably 36-72h, and then filtered, washed, dried, and calcined to obtain ZSM-23 molecular sieve; and / or

[0032] More preferably, the drying temperature is 80-120° C., the drying time is 4-12 hours, the roasting temperature is 500-600° C., and the roasting time is 2-6 hours.

[0033] In particular, the present invention discloses the following technical solutions:

[0034] 1. A ZSM-23 molecular sieve, characterized in that: the mesopore volume of the molecular sieve with a pore size of 3-8 nm, preferably 3-6 nm, accounts for 45-90% of the total pore volume of the molecular sieve, preferably 50-85%, and more preferably 55-81%.

[0035] 2. The ZSM-23 molecular sieve according to Scheme 1 is characterized in that: the relative crystallinity of the molecular sieve is 95-120%, and the relative crystallinity retention of the molecular sieve after hydrothermal treatment with water vapor at 600°C for 2 hours is 95-100%.

[0036] 3. The ZSM-23 molecular sieve according to any one of the aforementioned schemes, characterized in that: the specific surface area of ​​the molecular sieve is 300-430m 2 / g, pore volume of 0.31-0.5cm 3 / g, micropore specific surface area is 50-170m 2 / g, mesopore specific surface area is 150-310m 2 / g, for example, the specific surface area of ​​the molecular sieve is 320-405m 2 / g, pore volume is 0.34-0.45cm 3 / g, micropore specific surface area is 80-140m 2 / g, and the mesopore specific surface area is 261-295m 2 / g.

[0037] 4. The ZSM-23 molecular sieve according to any one of the aforementioned schemes, characterized in that: the ZSM-23 molecular sieve has a characteristic diffraction peak at 2θ of about 11.3°+ / -0.3° (for example, + / -0.2° or + / -0.1°) in the XRD spectrum.

[0038] 5. The ZSM-23 molecular sieve according to any one of the aforementioned schemes is characterized in that: the ZSM-23 molecular sieve has characteristic diffraction peaks at 2θ of 11.2-11.5°, 19.5-19.9°, 20.7-21.0°, and 22.8-23.1° in the XRD spectrum.

[0039] 6. A method for preparing the ZSM-23 molecular sieve according to any one of schemes 1 to 5, comprising the following steps:

[0040] (1) preparing or selecting a silicon source for preparing ZSM-23 molecular sieve, such as amorphous silicon dioxide;

[0041] (2) treating the silicon source used to prepare the ZSM-23 molecular sieve described in step (1) with an alkali;

[0042] (3) ZSM-23 molecular sieve was prepared using alkali-treated amorphous silica as the silicon source.

[0043] 7. The use of the alkali-treated amorphous silica obtained in step (2) of the method described in Scheme 6 as a silicon source in the process of preparing ZSM-23 molecular sieve.

[0044] 8. The method or use according to any one of the above schemes, characterized in that: in step (1), the amorphous silicon dioxide has a specific surface area of ​​600-1300m 2 / g, preferably 700-1200m 2 / g; pore volume of 0.6-1.3cm 3 / g, preferably 0.7-1.2cm 3 / g; the pore diameter is 1-13 nm, preferably 2-10 nm.

[0045] 9. The method or use according to any one of the aforementioned schemes is characterized in that: in step (1), the amorphous silica is prepared as follows: a silicon source is added to deionized water and dispersed evenly, and then a surfactant is added and stirred; the solution pH is adjusted to 1-5, preferably 1.5-4, and then heated in a water bath for a period of time; and amorphous silica is obtained after filtering, washing, drying, and calcining.

[0046] 10. The method or use according to any one of the aforementioned schemes, characterized in that: in step (1), the silicon source is an inorganic silicon source, preferably one or more of water glass, silica sol or white carbon black.

[0047] 11. The method or use according to any one of the aforementioned schemes, characterized in that: in step (1), the surfactant is one or more of cetyltrimethylammonium chloride, cetyltrimethylammonium bromide, octadecyltrimethylammonium chloride, and octadecyltrimethylammonium bromide.

[0048] 12. The method or use according to any one of the preceding schemes, characterized in that: in step (1), the molar ratio of the silicon source calculated as SiO2 to the surfactant is 1:(0.02-0.3), preferably 1:(0.05-0.2).

[0049] 13. The method or use according to any one of the preceding schemes, characterized in that: in step (1), the molar ratio of the silicon source calculated as SiO2 to deionized water is 1:(30-300), preferably 1:(50-220).

[0050] 14. The method or use according to any one of the preceding schemes, characterized in that: in step (1), the heating temperature is 30-80°C, preferably 40-70°C, and the heating time is 0.5-8h, preferably 3-6h.

[0051] 15. The method or use according to any one of the preceding schemes, characterized in that: in step (1), the drying temperature is 80-120°C, the drying time is 4-12 hours, the roasting temperature is 500-600°C, and the roasting time is 2-6 hours.

[0052] 16. The method or use according to any one of the aforementioned schemes, characterized in that: in step (2), the alkali treatment is to add the amorphous silica prepared in step (1) into an alkaline solution and heat and stir.

[0053] 17. The method or use according to any one of the aforementioned schemes, characterized in that: in step (2), the alkali treatment adopts inorganic alkali treatment, and the inorganic alkali is one or more of sodium hydroxide, potassium hydroxide or ammonia water.

[0054] 18. The method or use according to any one of the aforementioned schemes, characterized in that: in step (2), the alkali treatment heating and stirring time is 0.5-12 hours, preferably 2-8 hours; the heating temperature is 25-60°C, preferably 30-50°C.

[0055] 19. The method or use according to any one of the above schemes, characterized in that: in step (2), OH - The molar ratio of the inorganic base calculated as alkali to the amorphous silicon dioxide calculated as SiO2 is 0.05-0.24, preferably 0.06-0.22.

[0056] 20. The method or use according to any one of the aforementioned schemes, characterized in that: in step (3), amorphous silica treated with alkali is used as a silicon source, and the silicon source is mixed with an aluminum source, an alkali source (MOH), a template (R), and water to form a gel, which is then crystallized, filtered, washed, dried, and calcined to obtain a ZSM-23 molecular sieve.

[0057] 21. The method or use according to any one of the aforementioned schemes, characterized in that the molar ratio of silicon source (calculated as SiO2): aluminum source (calculated as Al2O3): alkali source (calculated as hydroxide): template: H2O in the gel is 1:(0.003-0.03):(0.03-0.3):(0.05-2):(10-90); further preferably, the molar ratio of silicon source (calculated as SiO2): aluminum source (calculated as Al2O3): alkali source (calculated as hydroxide): template: H2O in the gel is 1:(0.005-0.02):(0.03-0.16):(0.08-1.6):(20-70).

[0058] 22. The method or use according to any one of the preceding schemes, characterized in that the gel is crystallized at 150-200°C, preferably 170-180°C, for 24-96 hours, preferably 36-72 hours, and then filtered, washed, dried, and calcined to obtain ZSM-23 molecular sieve.

[0059] 23. The method or use according to any one of the preceding schemes, characterized in that: in step (3), the drying temperature is 80-120°C, the drying time is 4-12 hours, the roasting temperature is 500-600°C, and the roasting time is 2-6 hours.

[0060] 24. An alkali-treated amorphous silicon dioxide, characterized in that: the specific surface area is 600-1300m 2 / g, preferably 700-1200m 2 / g; pore volume of 0.6-1.3cm 3 / g, preferably 0.7-1.2cm 3 / g; the pore diameter is 1-13 nm, preferably 2-10 nm.

[0061] 25. An alkali-treated amorphous silicon dioxide, characterized in that: the specific surface area is 600-1300m 2 / g, preferably 700-1200m 2 / g; pore volume of 0.6-1.3cm 3 / g, preferably 0.7-1.2cm 3 / g; pore diameter is 1-13nm, preferably 2-10nm;

[0062] The alkali treatment is carried out according to step (2) of the method described in Schemes 6 and 8-19.

[0063] Compared with the prior art, the ZSM-23 molecular sieve and its preparation method and application in the present invention have the following advantages:

[0064] In the method of the present invention, mesoporous amorphous silica is prepared in the early stage with the assistance of a surfactant, and is used as a silicon source for the later synthesis of ZSM-23 molecular sieves. The amorphous silica generated in this process has a mesoporous structure and is not highly crystallized into a stable crystalline form. After being treated in a further low-concentration alkaline solution for a period of time, some -Si-O- bonds are opened, which helps to generate -Si-O-Al- bonds in the molecular sieve structure. However, most of the mesoporous structure is retained. Under the action of a microporous template agent in the later stage, a microporous structure is generated in a suitable ZSM-23 molecular sieve synthesis system. At the same time, the mesoporous structure is further crystallized and stabilized, thereby obtaining a micro-mesoporous composite ZSM-23 molecular sieve. The method has a simple operation process, low dosages of the surfactant and microporous template used, low cost, and excellent performance of the obtained molecular sieve product. It is a feasible industrial production route.

[0065] The ZSM-23 molecular sieve synthesized by the method of the present invention has both the acidic properties of the microporous structure with adjustable properties and the large pore characteristics of the mesoporous structure, high specific surface area and pore volume, high crystallinity, and strong thermal stability and hydrothermal stability. It can be used as an excellent adsorbent or catalyst material, has broader application prospects in the field of shape-selective catalysis, and further improves its performance in petrochemical reactions such as cracking and isomerization of long-chain alkanes and olefins, and isomerization of aromatics. BRIEF DESCRIPTION OF THE DRAWINGS

[0066] Figure 1 This is the XRD spectrum of the product synthesized in Example 1 of the present invention.

[0067] Figure 2 This is the nitrogen physical adsorption diagram of the product synthesized in Example 1 of the present invention. DETAILED DESCRIPTION

[0068] The analysis method of the present invention is as follows: the specific surface area and pore volume of the molecular sieve are measured using an ASAP2405 physical adsorption instrument produced by Micromeritics Corporation of the United States, wherein the specific surface area refers to the sum of the micropore specific surface area and the mesopore specific surface area.

[0069] XRD patterns of the samples were obtained using a Rigaku Dmax2500 X-ray diffractometer, and relative crystallinity was calculated. The sum of the diffraction peak heights at approximately 11.3° and 19.5-23° 2θ in the XRD pattern of a conventional ZSM-23 molecular sieve was taken as 100% crystallinity, and the relative crystallinity of the other samples was calculated by comparison with this value.

[0070] According to the present invention, the ZSM-23 molecular sieve has a characteristic diffraction peak at about 11.3°+ / -0.3° (eg, + / -0.2° or + / -0.1°) 2θ in the XRD spectrum.

[0071] According to the present invention, the ZSM-23 molecular sieve has characteristic diffraction peaks at 2θ of 11.2-11.5°, 19.5-19.9°, 20.7-21.0°, and 22.8-23.1° in the XRD spectrum.

[0072] In order to better illustrate the present invention, the following is further described in conjunction with Examples and Comparative Examples. However, the scope of the present invention is not limited to the scope of these Examples.

[0073] Example 1

[0074] (1) Preparation of mesoporous silicon source

[0075] Add 50g of water glass (SiO2 mass fraction is 27%) to 250g of deionized water, stir and disperse evenly, then add octadecyltrimethylammonium chloride (C 18 TMAC1) was stirred for 0.5h, wherein SiO2 and C 18 The molar ratio of TMACl was 1:0.08; the pH of the solution was adjusted to 2 with hydrochloric acid and then heated in a 50 ° C water bath for 4 h; after completion, the solution was filtered, washed, dried at 80 ° C for 8 h, and calcined at 550 ° C for 3 h to obtain amorphous silica;

[0076] (2) Preparation of micro-mesoporous ZSM-23 molecular sieve:

[0077] a) Dissolve 0.35 g of NaOH in 35 mL of deionized water, add 3.7 g of the mesoporous silicon source (OH) prepared in (1) - / SiO2 molar ratio = 0.14), placed in a 45 ° C water bath and stirred for 3h;

[0078] b) dissolving aluminum sulfate and isopropylamine (IPA) in the remaining water in sequence, and adding the silicon source dispersion obtained in a) thereto to obtain a total molar ratio of SiO2 in the silicon source: Al2O3 in the aluminum source: OH - The gel with a ratio of 1:IPA:H2O=1:0.01:0.08:1.0:50 was crystallized at 180°C for 48 hours, filtered, washed, dried, and calcined to measure its relative crystallinity, specific surface area, pore volume, and pore size distribution. After hydrothermal treatment with steam at 600°C for 2 hours, its hydrothermal stability was measured. The XRD spectrum is shown in the figure below. Figure 1 As shown (confirming that the molecular sieve obtained is ZSM-23 molecular sieve), the nitrogen physical adsorption curve is as follows Figure 2 The specific properties are shown in Table 1.

[0079] Example 2

[0080] (1) Preparation of mesoporous silicon source

[0081] Add 50g of water glass (SiO2 mass fraction is 27%) to 250g of deionized water, stir and disperse evenly, then add octadecyltrimethylammonium chloride (C 18 TMAC1) was stirred for 0.5h, wherein SiO2 and C 18 The molar ratio of TMACl was 1:0.08; the pH of the solution was adjusted to 2 with hydrochloric acid and then heated in a 50 ° C water bath for 4 h; after completion, the solution was filtered, washed, dried at 100 ° C for 4 h, and calcined at 550 ° C for 3 h to obtain amorphous silica;

[0082] (2) Preparation of micro-mesoporous ZSM-23 molecular sieve:

[0083] a) Dissolve 0.42 g of NaOH in 40 mL of deionized water, add 3.7 g of the mesoporous silicon source (OH) prepared in (1) - / SiO2 molar ratio = 0.17), placed in a 35°C water bath and stirred for 6h;

[0084] b) dissolving aluminum sulfate and isopropylamine (IPA) in the remaining water in sequence, and adding the silicon source dispersion obtained in a) thereto to obtain a total molar ratio of SiO2 in the silicon source: Al2O3 in the aluminum source: OH - The gel with a ratio of 1:0.005:0.10:1.0:50 was crystallized at 180°C for 48 hours, filtered, washed, dried, and calcined to measure its relative crystallinity, specific surface area, pore volume, and pore size distribution. After hydrothermal treatment with steam at 600°C for 2 hours, its hydrothermal stability was measured. Figure 1 Similar to the physical adsorption curve of nitrogen Figure 2 The specific properties are shown in Table 1.

[0085] Example 3

[0086] (1) Preparation of mesoporous silicon source

[0087] Add 50g of water glass (SiO2 mass fraction is 27%) to 1200g of deionized water, stir and disperse evenly, then add octadecyltrimethylammonium chloride (C 18 TMAC1) was stirred for 2 h, wherein SiO2 and C 18 The molar ratio of TMACl was 1:0.2; the pH of the solution was adjusted to 3 with hydrochloric acid and then heated in a 50 ° C water bath for 4 h; after completion, the solution was filtered, washed, dried at 80 ° C for 4 h, and calcined at 500 ° C for 3 h to obtain amorphous silica;

[0088] (2) Preparation of micro-mesoporous ZSM-23 molecular sieve:

[0089] a) Dissolve 0.15 g of NaOH in 35 mL of deionized water, add 3.7 g of the mesoporous silicon source (OH) prepared in (1) - / SiO2 molar ratio = 0.06), placed in a 45 ° C water bath and stirred for 3 h;

[0090] b) dissolving aluminum sulfate, isopropylamine (IPA), and NaOH in the remaining water in sequence, and adding the silicon source dispersion obtained in a) thereto to obtain a total molar ratio of SiO2 in the silicon source: Al2O3 in the aluminum source: OH - The gel with a ratio of 1:0.01:0.08:1.0:50 was crystallized at 180°C for 48 hours, filtered, washed, dried, and calcined to measure its relative crystallinity, specific surface area, pore volume, and pore size distribution. After hydrothermal treatment with steam at 600°C for 2 hours, its hydrothermal stability was measured. Figure 1 Similar to the physical adsorption curve of nitrogen Figure 2 The specific properties are shown in Table 1.

[0091] Example 4

[0092] (1) Preparation of mesoporous silicon source

[0093] Add 50g of water glass (SiO2 mass fraction is 27%) to 800g of deionized water, stir and disperse evenly, then add octadecyltrimethylammonium chloride (C 18 TMAC1) was stirred for 2 h, wherein SiO2 and C 18 The molar ratio of TMACl was 1:0.15; the pH of the solution was adjusted to 4 with hydrochloric acid and then heated in a 50 ° C water bath for 4 h; after completion, the solution was filtered, washed, dried at 90 ° C for 4 h, and calcined at 550 ° C for 3 h to obtain amorphous silica;

[0094] (2) Preparation of micro-mesoporous ZSM-23 molecular sieve:

[0095] a) Dissolve 0.42 g of NaOH in 40 mL of deionized water, add 3.7 g of the mesoporous silicon source (OH) prepared in (1) - / SiO2 molar ratio = 0.17), placed in a 40 ° C water bath and stirred for 3 h;

[0096] b) dissolving aluminum sulfate and isopropylamine (IPA) in the remaining water in sequence, and adding the silicon source dispersion obtained in a) thereto to obtain a total molar ratio of SiO2 in the silicon source: Al2O3 in the aluminum source: OH -The gel with a ratio of 1:0.005:0.10:1.0:50 was crystallized at 180°C for 48 hours, filtered, washed, dried, and calcined to measure its relative crystallinity, specific surface area, pore volume, and pore size distribution. After hydrothermal treatment with steam at 600°C for 2 hours, its hydrothermal stability was measured. Figure 1 Similar to the physical adsorption curve of nitrogen Figure 2 The specific properties are shown in Table 1.

[0097] Example 5

[0098] (1) Preparation of mesoporous silicon source

[0099] Add 50g of water glass (SiO2 mass fraction is 27%) to 210g of deionized water, stir and disperse evenly, then add octadecyltrimethylammonium chloride (C 18 TMAC1) was stirred for 1 h, wherein SiO2 and C 18 The molar ratio of TMACl was 1:0.05; the pH of the solution was adjusted to 2 with hydrochloric acid and then heated in a 60 ° C water bath for 4 h; after completion, the solution was filtered, washed, dried at 80 ° C for 8 h, and calcined at 550 ° C for 3 h to obtain amorphous silica;

[0100] (2) Preparation of micro-mesoporous ZSM-23 molecular sieve:

[0101] a) Dissolve 0.35 g of NaOH in 35 mL of deionized water, add 3.7 g of the mesoporous silicon source (OH) prepared in (1) - / SiO2 molar ratio = 0.14), placed in a 50 ° C water bath and stirred for 2 h;

[0102] b) dissolving aluminum sulfate and isopropylamine (IPA) in the remaining water in sequence, and adding the silicon source dispersion obtained in a) thereto to obtain a total molar ratio of SiO2 in the silicon source: Al2O3 in the aluminum source: OH - The gel with a ratio of 1:0.01:0.08:1.0:50 was crystallized at 180°C for 48 hours, filtered, washed, dried, and calcined to measure its relative crystallinity, specific surface area, pore volume, and pore size distribution. After hydrothermal treatment with steam at 600°C for 2 hours, its hydrothermal stability was measured. Figure 1 Similar to the physical adsorption curve of nitrogen Figure 2 The specific properties are shown in Table 1.

[0103] Example 6

[0104] (1) Preparation of mesoporous silicon source

[0105] Add 50g of water glass (SiO2 mass fraction is 27%) to 210g of deionized water, stir and disperse evenly, then add octadecyltrimethylammonium chloride (C 18 TMAC1) was stirred for 1 h, wherein SiO2 and C 18 The molar ratio of TMACl was 1:0.06; the pH of the solution was adjusted to 2 with hydrochloric acid and then heated in a 60 ° C water bath for 4 h; after completion, the solution was filtered, washed, dried at 80 ° C for 8 h, and calcined at 550 ° C for 3 h to obtain amorphous silica;

[0106] (2) Preparation of micro-mesoporous ZSM-23 molecular sieve:

[0107] a) Dissolve 0.10 g NaOH and 1.36 g concentrated ammonia (mass fraction about 27%) in 35 mL deionized water, add 3.7 g mesoporous silicon source (OH) prepared in (1) - / SiO2 molar ratio = 0.22), placed in a 40 ° C water bath and stirred for 6 h;

[0108] b) dissolving aluminum sulfate and isopropylamine (IPA) in the remaining water in sequence, and adding the silicon source dispersion obtained in a) to the remaining water to obtain a total molar ratio of SiO2 in the silicon source: Al2O3 in the aluminum source: OH - The gel with a ratio of 1:0.01:0.15:1.0:50 was crystallized at 180°C for 48 hours, filtered, washed, dried, and calcined to measure its relative crystallinity, specific surface area, pore volume, and pore size distribution. After hydrothermal treatment with steam at 600°C for 2 hours, its hydrothermal stability was measured. Figure 1 Similar to the physical adsorption curve of nitrogen Figure 2 The specific properties are shown in Table 1.

[0109] Comparative Example 1 (refer to CN105540607A)

[0110] Under stirring at 35°C, 0.51g of pseudo-boehmite and 0.3g of strong sodium oxide were added to 26mL of deionized water. After the solution was homogenized, 0.3g of isopropylamine was added, followed by 21g of white carbon black, and the mixture was homogenized again for 1 hour. 24.5g of cereal starch was added, the mixture was heated to 90°C, and stirred and aged for 6 hours. Finally, the obtained mixture was transferred to a hydrothermal reactor with a polytetrafluoroethylene lining, statically crystallized at 160°C for 144 hours, removed, cooled, filtered, and dried at 80°C to obtain the molecular sieve raw powder. The micro-mesoporous composite ZSM-23 molecular sieve was calcined at 500°C for 12 hours in an air atmosphere, and its relative crystallinity, specific surface area, pore volume, and pore size distribution were measured; after hydrothermal treatment with water vapor at 600°C for 2 hours, its hydrothermal stability was measured. The specific properties are shown in Table 1.

[0111] Comparative Example 2

[0112] (1) Preparation of mesoporous silicon source

[0113] Add 50g of water glass (SiO2 mass fraction is 27%) to 250g of deionized water, stir and disperse evenly, then add octadecyltrimethylammonium chloride (C 18 TMAC1) was stirred for 0.5h, wherein SiO2 and C 18 The molar ratio of TMACl was 1:0.08; the pH of the solution was adjusted to 2 with hydrochloric acid and then heated in a 50 ° C water bath for 4 h; after completion, the solution was filtered, washed, dried, and calcined at 550 ° C to obtain amorphous silica;

[0114] (2) a) Disperse 3.7 g of the mesoporous silicon source prepared in (1) into 35 mL of deionized water and stir in a 50°C water bath for 2 h;

[0115] b) Aluminum sulfate, isopropylamine (IPA), and NaOH were sequentially dissolved in the remaining water, and the silicon source dispersion obtained in a) was added thereto to prepare a gel having a total molar ratio of SiO2 in the silicon source: Al2O3 in the aluminum source: NaOH:IPA:H2O = 1:0.01:0.08:1.0:50. After crystallization at 180°C for 48 hours, the gel was filtered, washed, dried, and calcined, and the relative crystallinity, specific surface area, pore volume, and pore size distribution were measured. After hydrothermal treatment with water vapor at 600°C for 2 hours, the hydrothermal stability was measured. Specific properties are shown in Table 1.

[0116] Comparative Example 3

[0117] (1) Preparation of mesoporous silicon source

[0118] Add 50g of water glass (SiO2 mass fraction is 27%) to 1200g of deionized water, stir and disperse evenly, then add octadecyltrimethylammonium chloride (C 18 TMAC1) was stirred for 2 h, wherein SiO2 and C 18 The molar ratio of TMACl was 1:0.2; the pH of the solution was adjusted to 3 with hydrochloric acid and then heated in a 50 ° C water bath for 4 h; after completion, the solution was filtered, washed, dried, and calcined at 550 ° C to obtain amorphous silica;

[0119] (2) a) Dissolve 0.70 g of NaOH in 40 mL of deionized water, add 3.7 g of the mesoporous silica source (OH) obtained in (1) - / SiO2 molar ratio = 0.28), placed in a 45 ° C water bath and stirred for 3 h;

[0120] b) aluminum sulfate and isopropylamine (IPA) were sequentially dissolved in the remaining water, and the silicon source dispersion obtained in a) was added thereto to prepare a gel having a total molar ratio of SiO2 in the silicon source: Al2O3 in the aluminum source: NaOH:IPA:H2O = 1:0.01:0.16:1.0:50. After crystallization at 180°C for 48 hours, the gel was filtered, washed, dried, and calcined, and the relative crystallinity, specific surface area, pore volume, and pore size distribution were measured. After hydrothermal treatment with water vapor at 600°C for 2 hours, the hydrothermal stability was measured.

[0121] Comparative Example 4

[0122] (1) Preparation of mesoporous silicon source

[0123] Add 50g of water glass (SiO2 mass fraction is 27%) to 1200g of deionized water, stir and disperse evenly, then add octadecyltrimethylammonium chloride (C 18 TMAC1) was stirred for 2 h, wherein SiO2 and C 18 The molar ratio of TMACl was 1:0.2; the pH of the solution was adjusted to 3 with hydrochloric acid and then heated in a 50 ° C water bath for 4 h; after completion, the solution was filtered, washed, dried, and calcined at 550 ° C to obtain amorphous silica;

[0124] (2) a) Dissolve 0.10 g of NaOH in 40 mL of deionized water, add 3.7 g of the mesoporous silicon source (OH) prepared in (1) - / SiO2 molar ratio = 0.04), placed in a 45 ° C water bath and stirred for 3 h;

[0125] b) aluminum sulfate, isopropylamine (IPA), and sodium hydroxide were sequentially dissolved in the remaining water, and the silicon source dispersion obtained in a) was added thereto to prepare a gel having a total molar ratio of SiO2 in the silicon source: Al2O3 in the aluminum source: NaOH:IPA:H2O = 1:0.01:0.08:1.0:50. After crystallization at 180°C for 48 hours, the gel was filtered, washed, dried, and calcined, and the relative crystallinity, specific surface area, pore volume, and pore size distribution of the gel was measured; and after hydrothermal treatment with water vapor at 600°C for 2 hours, the hydrothermal stability of the gel was measured.

[0126] Comparative Example 5 (Preparation of Conventional ZSM-23 Molecular Sieve)

[0127] Water glass, aluminum sulfate, isopropylamine (IPA), sodium hydroxide, and water were mixed to prepare a gel with a total molar ratio of SiO2 in the silicon source: Al2O3 in the aluminum source: NaOH:IPA:H2O = 1:0.01:0.08:1.0:50. After heating at 180°C for 72 hours, the gel was filtered, washed, dried, and calcined, and its relative crystallinity was measured. After hydrothermal treatment with water vapor at 600°C for 2 hours, its hydrothermal stability was measured. Specific properties are shown in Table 1.

[0128] Table 1

[0129] <![CDATA[Specific surface area, m 2 / g]]> <![CDATA[Micropore surface area, m 2 / g]]> <![CDATA[Mesoporous surface area, m 2 / g]]> <![CDATA[Pore volume, cm 3 / g]]> Mesoporous content with pore size of 3-8nm, % Relative density, % Relative crystallinity after hydrothermal treatment, % <![CDATA[Relative crystallinity retention, % d > Example 1 395 105 290 0.42 77 102 103 100 Example 2 387 99 288 0.41 56 104 102 98 Example 3 398 107 291 0.45 80 114 110 96 Example 4 378 101 277 0.38 60 100 99 99 Example 5 384 91 293 0.40 69 113 108 96 Example 6 401 114 287 0.45 84 105 106 100 Comparative Example 1 289 126 163 0.28 31 103 74 72 Comparative Example 2 69 61 8 0.03 <![CDATA[- a ]]> <![CDATA[- a ]]> <![CDATA[- a ]]> <![CDATA[- a ]]> Comparative Example 3 232 167 65 0.24 <![CDATA[- b ]]> <![CDATA[- b ]]> <![CDATA[- b ]]> <![CDATA[- b ]]> Comparative Example 4 108 84 24 0.09 <![CDATA[- c ]]> <![CDATA[- c ]]> <![CDATA[- c ]]> <![CDATA[- c ]]> Comparative Example 5 228 188 40 0.24 18 100 101 100

[0130] aNo molecular sieve product was obtained by crystallization under these conditions, so this property could not be analyzed.

[0131] b The products generated under these conditions are mainly other molecular sieves, so this property cannot be analyzed.

[0132] c Under this condition, crystallization is incomplete, so this property cannot be analyzed.

[0133] dRelative crystallinity retention = crystallinity after hydrothermal treatment / relative crystallinity. Due to measurement error, results greater than 100% are considered 100%.

[0134] The data in Table 1 demonstrate that the preparation method of the present invention can produce a ZSM-23 molecular sieve having a micro-mesoporous composite structure through a simple synthesis process, using a low amount of surfactant and at a low cost. The resulting micro-mesoporous composite ZSM-23 molecular sieve exhibits high crystallinity, large specific surface area and pore volume, high mesopore content, a relatively concentrated size distribution, and excellent thermal and hydrothermal stability, possessing broad application prospects.

[0135] The performance of ZSM-23 molecular sieve samples was evaluated in a fixed bed microreactor. 20 -C 30 The reaction conditions and catalytic results in the hydroisomerization reaction are as follows:

[0136] Reaction materials: 90wt% decahydronaphthalene, 10wt% C 20 -C 30 straight-chain alkanes;

[0137] Reaction conditions: reaction temperature 280 ℃; liquid space velocity 1.0 h-1; hydrogen-to-oil ratio 600; reaction hydrogen pressure 4.0 MPa;

[0138] Comparative Example 1:

[0139] Liquid collection (C5 + ): 93%; C 20 -C 30 Isomerization degree: 100%; C 20 -C 30 Isomerization product yield: 46%; C 20 -C 30 The ratio of multi-branched to single-branched components in the isomerization product is 0.6.

[0140] Comparative Example 5:

[0141] Liquid collection (C5 + ): 94%; C 20 -C 30 Isomerization degree: 100%; C 20 -C 30 Yield of isomerization product: 44%; C 20 -C 30 The ratio of multi-branched to single-branched components in the isomerization product: 0.5.

[0142] Example 4:

[0143] Liquid collection (C5 + ): 95%; C 20 -C 30 Isomerization degree: 100%; C 20 -C 30 Isomerization product yield: 53%; C 20 -C 30 The ratio of multi-branched to single-branched components in the isomerization product is 2.1.

[0144] Example 6:

[0145] Liquid collection (C5 + ): 96%; C 20 -C 30 Isomerization degree: 100%; C 20 -C 30 Yield of isomerization product: 54%; C 20 -C 30 The ratio of multi-branched to single-branched components in the isomerization product is 2.3.

Claims

1. A ZSM-23 molecular sieve, characterized in that: The mesopore volume of the molecular sieve with a pore size of 3-8 nm accounts for 45-90% of the total pore volume of the molecular sieve; the relative crystallinity of the molecular sieve is 95-120%, and the relative crystallinity retention of the molecular sieve after hydrothermal treatment with water vapor at 600°C for 2 hours is 95-100%.

2. The ZSM-23 molecular sieve according to claim 1, characterized in that: The mesopore volume of the molecular sieve with a pore diameter of 3-8 nm accounts for 50-85% of the total pore volume of the molecular sieve.

3. The ZSM-23 molecular sieve according to claim 1, characterized in that: The mesopore volume of the molecular sieve with a pore diameter of 3-8 nm accounts for 55-81% of the total pore volume of the molecular sieve.

4. The ZSM-23 molecular sieve according to claim 1, characterized in that: The mesopore volume of the molecular sieve with a pore diameter of 3-6 nm accounts for 45-90% of the total pore volume of the molecular sieve.

5. The ZSM-23 molecular sieve according to claim 1, characterized in that: The mesopore volume of the molecular sieve with a pore diameter of 3-6 nm accounts for 50-85% of the total pore volume of the molecular sieve.

6. The ZSM-23 molecular sieve according to claim 1, characterized in that: The mesopore volume of the molecular sieve with a pore diameter of 3-6 nm accounts for 55-81% of the total pore volume of the molecular sieve.

7. The ZSM-23 molecular sieve according to any one of claims 1 to 6, characterized in that: The specific surface area of ​​the molecular sieve is 300-430m 2 / g, pore volume of 0.31-0.5cm 3 / g, micropore specific surface area is 50-170m 2 / g, mesopore specific surface area is 150-310m 2 / g.

8. The ZSM-23 molecular sieve according to any one of claims 1 to 6, characterized in that: The specific surface area of ​​the molecular sieve is 320-405m 2 / g, pore volume is 0.34-0.45cm 3 / g, micropore specific surface area is 80-140m 2 / g, and the mesopore specific surface area is 261-295m 2 / g.

9. A method for preparing the ZSM-23 molecular sieve according to any one of claims 1 to 8, comprising the steps of: (1) preparing or selecting silicon-source amorphous silica for preparing ZSM-23 molecular sieve; (2) treating the silicon source used to prepare the ZSM-23 molecular sieve described in step (1) with an alkali; (3) ZSM-23 molecular sieve was prepared using alkali-treated amorphous silica as the silicon source.

10. The method according to claim 9, characterized in that: In step (1), the specific surface area of ​​the amorphous silicon dioxide is 600-1300m 2 / g, pore volume of 0.6-1.3cm 3 / g, and the pore diameter is 1-13nm.

11. The method according to claim 10, characterized in that: In step (1), the specific surface area of ​​the amorphous silicon dioxide is 700-1200m 2 / g, pore volume of 0.7-1.2cm 3 / g, and the pore diameter is 2-10nm.

12. The method according to claim 9, wherein: In step (1), the amorphous silica is prepared as follows: a silicon source is added to deionized water and dispersed uniformly, and then a surfactant is added and stirred; after the pH of the solution is adjusted to 1-5, the solution is heated in a water bath for a period of time; Amorphous silicon dioxide is obtained after filtering, washing, drying and calcining.

13. The method according to claim 12, wherein: In step (1), during the preparation of the amorphous silica, the solution pH is adjusted to 1.5-4, and then heated in a water bath for a period of time.

14. The method according to claim 12, wherein: In step (1), the silicon source is an inorganic silicon source, selected from one or more of water glass, silica sol or white carbon black.

15. The method according to any one of claims 12 to 14, characterized in that: In step (1), the surfactant is one or more of cetyltrimethylammonium chloride, cetyltrimethylammonium bromide, octadecyltrimethylammonium chloride, and octadecyltrimethylammonium bromide.

16. The method according to any one of claims 12 to 14, characterized in that: In step (1), the molar ratio of the silicon source calculated as SiO2 to the surfactant is 1:(0.02-0.3).

17. The method according to claim 16, wherein: In step (1), the molar ratio of the silicon source calculated as SiO2 to the surfactant is 1:(0.05-0.2).

18. The method according to any one of claims 12 to 14, characterized in that: In step (1), the molar ratio of the silicon source calculated as SiO2 to deionized water is 1:(30-300).

19. The method according to claim 18, wherein: In step (1), the molar ratio of the silicon source calculated as SiO2 to deionized water is 1:(50-220).

20. The method according to any one of claims 12 to 14, characterized in that: In step (1), the heating temperature is 30-80°C and the heating time is 0.5-8h.

21. The method according to claim 20, characterized in that: In step (1), the heating temperature is 40-70°C and the heating time is 3-6h.

22. The method according to any one of claims 12 to 14, characterized in that: In step (1), the drying temperature is 80-120°C, the drying time is 4-12h, the roasting temperature is 500-600°C, and the roasting time is 2-6h.

23. The method according to claim 9, wherein: In step (2), the alkali treatment is to add the amorphous silica prepared in step (1) into an alkaline solution and heat and stir.

24. The method according to claim 23, wherein: In step (2), the alkali treatment adopts inorganic alkali treatment, and the inorganic alkali is one or more of sodium hydroxide, potassium hydroxide or ammonia water.

25. The method according to claim 23, wherein: In step (2), the alkali treatment heating and stirring time is 0.5-12h; the heating temperature is 25-60°C.

26. The method according to claim 25, characterized in that: In step (2), the alkali treatment heating and stirring time is 2-8h; the heating temperature is 30-50°C.

27. The method according to claim 9, wherein: In step (2), OH - The molar ratio of the inorganic base calculated as alkali to the amorphous silicon dioxide calculated as SiO2 is 0.05-0.

24.

28. The method according to claim 27, wherein: In step (2), OH - The molar ratio of the inorganic base calculated as alkali to the amorphous silicon dioxide calculated as SiO2 is 0.06-0.

22.

29. The method according to claim 9, wherein: In step (3), alkali-treated amorphous silica is used as a silicon source, and the silicon source is mixed with an aluminum source, an alkali source MOH, a template agent R, and water to form a gel, which is then crystallized, filtered, washed, dried, and calcined to obtain a ZSM-23 molecular sieve.

30. The method according to claim 29, wherein: The molar ratio of silicon source in the gel is calculated as SiO2: aluminum source is calculated as Al2O3: alkali source is calculated as hydroxide: template: H2O is 1: (0.003-0.03): (0.03-0.3): (0.05-2): (10-90).

31. The method according to claim 30, wherein: The molar ratio of silicon source calculated as SiO2: aluminum source calculated as Al2O3: alkali source calculated as hydroxide: template: H2O in the gel is 1: (0.005-0.02): (0.03-0.16): (0.08-1.6): (20-70).

32. The method according to any one of claims 29 to 31, characterized in that: The gel is crystallized at 150-200°C for 24-96h, filtered, washed, dried and calcined to obtain ZSM-23 molecular sieve.

33. The method according to claim 32, wherein: The gel was crystallized at 170-180°C for 36-72h.

34. The method according to any one of claims 29 to 31, characterized in that: In step (3), the drying temperature is 80-120°C, the drying time is 4-12h, the roasting temperature is 500-600°C, and the roasting time is 2-6h.

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