ZSM-23 molecular sieve as well as preparation method and application thereof

Abstract

The invention relates to the technical field of molecular sieve preparation, and discloses a ZSM-23 molecular sieve as well as a preparation method and application thereof. The ratio of the amount of 2, 6-dimethylpyridine infrared total B acid to the amount of pyridine infrared total B acid in the ZSM-23 molecular sieve is (65-99): 100, and in the 2, 6-dimethylpyridine infrared B acid, the ratio of the amount of B acid with the desorption temperature lower than 250 DEG C to the amount of the 2, 6-dimethylpyridine infrared total B acid is (64-95): 100. The B acid sites of the ZSM-23 molecular sieve are mainly distributed on the orifices and the outer surface, and the ZSM-23 molecular sieve is mainly composed of weak B acid, is high in catalytic activity, and has excellent catalytic reaction performance mainly composed of an orifice adsorption mechanism.

Description

Technical Field

[0001] This invention relates to the field of molecular sieve preparation technology, specifically to a ZSM-23 molecular sieve, its preparation method, and its application. Background Technology

[0002] ZSM-23 molecular sieve is a microporous molecular sieve with a high silica-to-alumina ratio. Due to its unique pore structure, it is widely used in separation, adsorption, and catalysis. In the petrochemical industry, ZSM-23 molecular sieve exhibits excellent catalytic performance in reactions such as long-chain alkane hydrocracking, olefin hydrocracking, and alkane isomerization, showing broad application prospects and market demand.

[0003] Patent application CN109694082A discloses a method for preparing ZSM-23 molecular sieve, including the following steps: (1) mixing silicon source, aluminum source, alkali source and organic template agent a in water to obtain gel a; (2) mixing silicon source, aluminum source, alkali source, organic template agent b and seed crystal in water to prepare gel, and after mixing evenly, transferring to a crystallization kettle, and crystallizing at 100-200℃ for 1-48h; (3) after the crystallization in step (2), recovering organic template agent b to obtain a first-stage microcrystalline solution; (4) adding gel a to the first-stage microcrystalline solution obtained in step (3), and after the crystallization is completed, recovering organic template agent a to obtain molecular sieve slurry, separating the mother liquor, washing and drying the slurry to obtain ZSM-23 molecular sieve raw powder. The ZSM-23 molecular sieve synthesized in this patent application failed to regulate the distribution of acidic sites. When applied to shape-selective catalytic reactions such as hydroisomerization, toluene disproportionation, and xylene isomerization, the acidic sites in the ZSM-23 molecular sieve channels are poorly accessible and have low utilization rates for most reactions due to steric hindrance and diffusion limitation.

[0004] Patent application CN109516471A discloses a method for synthesizing alumina-rich ZSM-23 molecular sieve. In the initial stage of synthesis, a molecular sieve gel is prepared and pre-crystallized to form a large number of molecular sieve nuclei with a high silica-to-alumina ratio. Then, a low silica-to-alumina ratio, template-free synthetic gel is added, and after crystallization, alumina-rich ZSM-23 molecular sieve with a surface silica-to-alumina ratio of 10-80 is formed. This method synthesizes alumina-rich ZSM-23 molecular sieve with a short time and low template agent dosage, increasing the number of pores and acidic centers on the outer surface, and reducing the grain size, thus enabling wider applications in shape-selective catalysis. However, this method does not achieve precise control over the aluminum atoms at the pores and outer surface, resulting in an insufficient proportion of Brønsted acid (B acid) content at the pores and outer surface. Furthermore, the high proportion of strong B acid at the pores and outer surface of the ZSM-23 molecular sieve promotes other side reactions while simultaneously promoting shape-selective catalysis. Summary of the Invention

[0005] The purpose of this invention is to overcome the problems of existing ZSM-23 molecular sieves, such as the relatively dispersed distribution of acidic sites and the low proportion of Brønsted acid (B acid) at the pore openings and outer surface, resulting in poor reactivity of ZSM-23 molecular sieves primarily based on pore opening adsorption. This invention provides a ZSM-23 molecular sieve, its preparation method, and its applications. The ZSM-23 molecular sieve of this invention has B acid sites mainly distributed at the pore openings and outer surface, and is predominantly composed of weak B acids, exhibiting excellent catalytic reactivity primarily based on pore opening adsorption.

[0006] To achieve the above objectives, the present invention provides a ZSM-23 molecular sieve, wherein the ratio of the total Brønsted acid content of 2,6-dimethylpyridine infrared radiation to the total Brønsted acid content of pyridine infrared radiation is 65~99:100, preferably 70~97:100, more preferably 74~95:100; and in the Brønsted acid of 2,6-dimethylpyridine infrared radiation, the ratio of the Brønsted acid content with a desorption temperature <250°C to the total Brønsted acid content of 2,6-dimethylpyridine infrared radiation is 64~95:100, preferably 67~93:100, more preferably 70~91:100.

[0007] A second aspect of this invention provides a method for preparing ZSM-23 molecular sieve, the method comprising the following steps: (1) A mixture of silicon source, template agent a and water is subjected to a crystallization reaction, and the solid phase material is separated from the reacted material; (2) The solid material, fatty amine and inorganic base are mixed and reacted once, and then ZSM-23 seed crystals are added and reacted twice; (3) The mixture obtained in step (2) is mixed with aluminum source and template agent b, and then crystallized, filtered, washed, dried and calcined in sequence.

[0008] A third aspect of the present invention provides a ZSM-23 molecular sieve prepared by the above method.

[0009] A fourth aspect of the present invention provides a hydrogenation catalyst comprising a support and an active component attached thereto, wherein the support is the ZSM-23 molecular sieve described above.

[0010] The fifth aspect of this invention provides the application of the above-mentioned hydrogenation catalyst in the hydrocracking of long-chain alkanes, the hydrocracking of olefins, or the isomerization of alkanes.

[0011] According to the present invention, the ZSM-23 molecular sieve has Brønsted acid sites mainly distributed at the pore openings and on the outer surface, and is dominated by weak Brønsted acid, exhibiting high catalytic activity and excellent catalytic reaction performance mainly based on the pore opening adsorption mechanism.

[0012] In the preparation method of ZSM-23 molecular sieve described in this invention, a mixture containing metastable pure silicon ten-membered ring molecular sieve nanocrystals is first prepared using a silicon source, a template agent, a fatty amine, and an inorganic base. This mixture is then mixed with an aluminum source and a template agent and crystallized. The chelate formed by the combination of the aluminum source and the template agent can bind to the hydroxyl groups on the surface of the metastable pure silicon ten-membered ring molecular sieve nanocrystals, embedding itself into the framework structure during crystallization and growing into a structurally stable ZSM-23 molecular sieve with a surface rich in weak Brønsted acid sites. The template agent used in this method is inexpensive and requires only a small amount, allowing for precise control of the Al sites in the ZSM-23 molecular sieve. This facilitates the enrichment of weak Brønsted acid sites at the pore openings and on the outer surface, significantly improving the reactivity of the ZSM-23 molecular sieve, which is primarily based on pore opening adsorption. Attached Figure Description

[0013] Figure 1 This is the XRD pattern of the ZSM-23 molecular sieve prepared in Example 1 of this invention. Detailed Implementation

[0014] The following provides a detailed description of specific embodiments of the present invention. It should be understood that the specific embodiments described herein are for illustrative and explanatory purposes only and are not intended to limit the scope of the invention.

[0015] In this invention, "total Brønsted acid content in pyridine infrared spectroscopy" is used to represent the total Brønsted acid content in ZSM-23 molecular sieves, including Brønsted acid on the outer surface of the molecular sieve, at the pore openings, and within the pores. It is determined by pyridine adsorption infrared spectroscopy. The specific process is as follows: ZSM-23 molecular sieve samples are prepared into self-supporting wafers (5~6 mg / cm³). 2 The sample was placed in an in-situ cell and treated under vacuum at 400℃ for 4 h, then cooled to 50℃, and spectra were collected. After adsorbing pyridine for 10 min, the sample was heated to 150℃ for desorption for 1 h, cooled to room temperature, and spectra were collected to calculate the total Brønsted acid content of pyridine. The Brønsted acid content was calculated according to the Lambert-Beer law, using a 1540 cm⁻¹ spectral depth. -1 The amount of Brønsted acid is calculated by measuring the area of ​​the absorption peak.

[0016] In this invention, "total Brønsted acid content of 2,6-dimethylpyridine infrared spectroscopy" is used to represent the amount of Brønsted acid distributed in the pores and outer surface of the ZSM-23 molecular sieve. It is determined by 2,6-dimethylpyridine adsorption infrared spectroscopy. The specific process is as follows: the molecular sieve sample is prepared into a self-supporting wafer (5~6 mg / cm³). 2The sample was placed in an in-situ cell and treated under vacuum at 400℃ for 4 hours, then cooled to 50℃, and spectra were collected. After adsorbing 2,6-dimethylpyridine for 10 minutes, the sample was heated to 150℃ for desorption for 1 hour, cooled to room temperature, and spectra were collected to calculate the total Brønsted acid content of 2,6-dimethylpyridine in the infrared spectrum. The sample was then heated to 250℃ for desorption for 1 hour, cooled to room temperature, and spectra were collected to calculate the Brønsted acid content of 2,6-dimethylpyridine in the infrared spectrum for Brønsted acid with a desorption temperature <250℃. The Brønsted acid content was calculated according to the Lambert-Beer law, using a 1630 cm⁻¹ spectral density. -1 1650cm -1 The amount of Brønsted acid is calculated by measuring the area of ​​the absorption peak.

[0017] In this invention, "the amount of Brønsted acid with a desorption temperature <250°C" is used to represent the amount of weak Brønsted acid. "The amount of Brønsted acid with a desorption temperature <250°C in 2,6-dimethylpyridine infrared Brønsted acid" is used to represent the amount of weak Brønsted acid distributed at the pores and outer surface of the ZSM-23 molecular sieve.

[0018] In this invention, the bulk SiO2 / Al2O3 (molar ratio) was obtained by X-ray fluorescence spectroscopy (XRF) analysis using a ZSX100e X-ray fluorescence spectrometer with Kα spectral line, LiF1 crystal, Rh target material, SC scintillation detector, timing of 20s, and vacuum atmosphere.

[0019] In this invention, the SiO2 / Al2O3 molar ratio on the outer surface was measured by X-ray photoelectron spectroscopy (XPS). The elemental composition and state of the catalyst surface were determined using a Thermofisher Multilab2000 electron spectrometer, with Mg Kα as the excitation source and a cathode voltage and current of 13 kV and 20 mA, respectively. The electron binding energy was calibrated using C1s (284.6 eV).

[0020] In the ZSM-23 molecular sieve of the present invention, Brønsted acid sites are mainly distributed at the pore openings and on the outer surface. Specifically, the ratio of the total Brønsted acid content of 2,6-dimethylpyridine to the total Brønsted acid content of pyridine in infrared spectroscopy is 65~99:100, preferably 70~97:100, and more preferably 74~95:100. That is, 65~99% (preferably 70~97%, more preferably 74~95%) of the Brønsted acid sites in the ZSM-23 molecular sieve are distributed at the pore openings and on the outer surface.

[0021] In the ZSM-23 molecular sieve of the present invention, the Brønsted acid at the pore openings and outer surface is mainly a weak Brønsted acid. Specifically, in the Brønsted acid of 2,6-dimethylpyridine infrared radiation, the ratio of the amount of Brønsted acid with a desorption temperature <250°C to the total amount of Brønsted acid of 2,6-dimethylpyridine infrared radiation is 64~95:100, preferably 67~93:100, more preferably 70~91:100. That is, 64~95% (preferably 67~93%, more preferably 70~91%) of the Brønsted acid at the pore openings and outer surface of the ZSM-23 molecular sieve is a weak Brønsted acid.

[0022] In the ZSM-23 molecular sieve of the present invention, the total pyridine Brønsted acid content in the infrared spectroscopy of the ZSM-23 molecular sieve can be 0.1~0.37 mmol / g, preferably 0.12~0.36 mmol / g, more preferably 0.13~0.35 mmol / g, and even more preferably 0.15~0.33 mmol / g. When the total pyridine Brønsted acid content in the infrared spectroscopy of the ZSM-23 molecular sieve is within the above-mentioned preferred range, the ZSM-23 molecular sieve exhibits higher catalytic activity.

[0023] In the ZSM-23 molecular sieve of the present invention, the total Brønsted acid content of 2,6-dimethylpyridine in infrared spectroscopy of the ZSM-23 molecular sieve can be 0.07~0.35 mmol / g, preferably 0.09~0.33 mmol / g, and more preferably 0.11~0.30 mmol / g. When the total Brønsted acid content of 2,6-dimethylpyridine in infrared spectroscopy of the ZSM-23 molecular sieve is within the above-mentioned preferred range, the ZSM-23 molecular sieve not only has high catalytic activity, but also better catalytic reaction performance mainly based on the pore adsorption mechanism.

[0024] In the ZSM-23 molecular sieve of the present invention, the amount of Brønsted acid (B acid) with a desorption temperature <250°C in the 2,6-dimethylpyridine infrared Brønsted acid of the ZSM-23 molecular sieve can be 0.06~0.31 mmol / g, preferably 0.07~0.30 mmol / g, more preferably 0.09~0.29 mmol / g, and even more preferably 0.10~0.26 mmol / g. When the amount of Brønsted acid with a desorption temperature <250°C in the 2,6-dimethylpyridine infrared Brønsted acid of the ZSM-23 molecular sieve is within the above-mentioned preferred range, the ZSM-23 molecular sieve not only has high catalytic activity, but also better catalytic reaction performance mainly based on the pore adsorption mechanism.

[0025] In the ZSM-23 molecular sieve of this invention, Al sites are mainly distributed on the outer surface of the molecular sieve, which is beneficial for the enrichment of weak β-acid sites at the pore openings and outer surface. Therefore, the bulk SiO2 / Al2O3 ratio of the ZSM-23 molecular sieve of this invention is significantly higher than that of the outer surface SiO2 / Al2O3 ratio. Preferably, the bulk SiO2 / Al2O3 ratio of the ZSM-23 molecular sieve is 40-400 higher than that of the outer surface SiO2 / Al2O3 ratio, more preferably 45-350 higher, and more preferably 50-320 higher.

[0026] In the ZSM-23 molecular sieve of the present invention, the bulk SiO2 / Al2O3 ratio of the ZSM-23 molecular sieve can be 70~500, preferably 90~400, and more preferably 120~300.

[0027] In the ZSM-23 molecular sieve of the present invention, the SiO2 / Al2O3 ratio on the outer surface of the ZSM-23 molecular sieve can be 40~120, preferably 45~90, and more preferably 50~80.

[0028] In some embodiments, the bulk SiO2 / Al2O3 ratio of the ZSM-23 molecular sieve is 70-500, the outer surface SiO2 / Al2O3 ratio is 40-120, and the bulk SiO2 / Al2O3 ratio is 40-400 higher than the outer surface SiO2 / Al2O3 ratio; the total Brønsted acid content of pyridine infrared radiation in the ZSM-23 molecular sieve is 0.10-0.37 mmol / g, the total Brønsted acid content of 2,6-dimethylpyridine infrared radiation is 0.07-0.35 mmol / g, and the ratio of the total Brønsted acid content of 2,6-dimethylpyridine infrared radiation to the total Brønsted acid content of pyridine infrared radiation is 65-99:100; in the Brønsted acid of 2,6-dimethylpyridine infrared radiation, the ratio of the Brønsted acid content with a desorption temperature <250℃ to the total Brønsted acid content of 2,6-dimethylpyridine infrared radiation is 64-95:100. According to this embodiment, the ZSM-23 molecular sieve not only has high catalytic activity, but also good catalytic reaction performance mainly based on pore adsorption mechanism.

[0029] In other embodiments, the bulk SiO2 / Al2O3 ratio of the ZSM-23 molecular sieve is 90-400, the outer surface SiO2 / Al2O3 ratio is 45-90, and the bulk SiO2 / Al2O3 ratio is 45-350 higher than the outer surface SiO2 / Al2O3 ratio; the total Brønsted acid content of pyridine infrared radiation in the ZSM-23 molecular sieve is 0.10-0.37 mmol / g, the total Brønsted acid content of 2,6-dimethylpyridine infrared radiation is 0.07-0.35 mmol / g, and the ratio of the total Brønsted acid content of 2,6-dimethylpyridine infrared radiation to the total Brønsted acid content of pyridine infrared radiation is 70-97:100; in the Brønsted acid of 2,6-dimethylpyridine infrared radiation, the ratio of the Brønsted acid content with a desorption temperature <250℃ to the total Brønsted acid content of 2,6-dimethylpyridine infrared radiation is 67-93:100. According to this embodiment, the catalytic activity of the ZSM-23 molecular sieve is further enhanced, and it has better catalytic reaction performance mainly based on the pore adsorption mechanism.

[0030] In some other preferred embodiments, the bulk SiO2 / Al2O3 ratio of the ZSM-23 molecular sieve is 90-400, the outer surface SiO2 / Al2O3 ratio is 45-90, and the bulk SiO2 / Al2O3 ratio is 45-350 higher than the outer surface SiO2 / Al2O3 ratio; the total Brønsted acid content of pyridine infrared radiation in the ZSM-23 molecular sieve is 0.12-0.36 mmol / g, the total Brønsted acid content of 2,6-dimethylpyridine infrared radiation is 0.09-0.33 mmol / g, and the ratio of the total Brønsted acid content of 2,6-dimethylpyridine infrared radiation to the total Brønsted acid content of pyridine infrared radiation is 70-97:100; in the Brønsted acid of 2,6-dimethylpyridine infrared radiation, the ratio of the Brønsted acid content with a desorption temperature <250℃ to the total Brønsted acid content of 2,6-dimethylpyridine infrared radiation is 67-93:100. According to this preferred embodiment, the ZSM-23 molecular sieve not only has better catalytic activity, but also its catalytic reaction performance, mainly based on the pore adsorption mechanism, is further improved.

[0031] In some further preferred embodiments, the bulk SiO2 / Al2O3 ratio of the ZSM-23 molecular sieve is 120-300, the outer surface SiO2 / Al2O3 ratio is 50-80, and the bulk SiO2 / Al2O3 ratio is 50-320 higher than the outer surface SiO2 / Al2O3 ratio; the total Brønsted acid content of the pyridine infrared spectroscopy of the ZSM-23 molecular sieve is 0.12-0.36 mmol / g, and the 2,6-dimethylpyridine infrared spectroscopy... The total Brønsted acid content is 0.09~0.33 mmol / g, and the ratio of the total Brønsted acid content of 2,6-dimethylpyridine infrared spectroscopy to the total Brønsted acid content of pyridine infrared spectroscopy is 74~95:100. In the Brønsted acid of 2,6-dimethylpyridine infrared spectroscopy, the Brønsted acid content with a desorption temperature <250℃ is 0.10~0.31 mmol / g, and the ratio of the Brønsted acid content with a desorption temperature <250℃ to the total Brønsted acid content of 2,6-dimethylpyridine infrared spectroscopy is 70~91:100. According to this preferred embodiment, the ZSM-23 molecular sieve not only possesses excellent catalytic activity but also achieves optimal catalytic reaction performance primarily based on pore adsorption mechanism.

[0032] The preparation method of ZSM-23 molecular sieve according to the present invention includes the following steps: (1) A mixture of silicon source, template agent a and water is subjected to a crystallization reaction, and the solid phase material is separated from the reacted material; (2) The solid material, fatty amine and inorganic base are mixed and reacted once, and then ZSM-23 seed crystals are added and reacted twice; (3) The mixture obtained in step (2) is mixed with aluminum source and template agent b, and then crystallized, filtered, washed, dried and calcined in sequence.

[0033] According to the preparation method of ZSM-23 molecular sieve described in this invention, the Al sites of ZSM-23 molecular sieve can be precisely controlled, so that the Al sites are mainly distributed on the outer surface of the molecular sieve. This is conducive to the enrichment of weak B acid sites at the pore openings and on the outer surface of the molecular sieve, so that the ZSM-23 molecular sieve not only has high catalytic activity, but also significantly improves the catalytic reaction performance mainly based on the pore opening adsorption mechanism.

[0034] In step (1), the molar ratio of water, the template agent a, and the silicon source (calculated as SiO2) can be (20~80):(0.1~1):1, preferably (30~70):(0.15~0.8):1.

[0035] In step (1), the silicon source can be a silicon source conventionally used in the art. In a specific embodiment, the silicon source can be selected from, but is not limited to, one or any combination of at least two of silica, silica sol, water glass, fumed silica, and tetraethyl orthosilicate. In a preferred embodiment, the silicon source is silica and / or fumed silica.

[0036] In step (1), the template agent a is a template agent capable of guiding the formation of ZSM-23 secondary structural units (such as ten-membered ring structures) in the pure silicon state. The specific type of substance is not particularly limited in this invention, and conventional template agents in the art can be selected. In specific embodiments, the template agent a can be selected from, but is not limited to, one or any combination of at least two of hexamethylenediamine, n-hexamethyleneamine, ethanol, tetrapropylammonium hydroxide, tetrapropylammonium bromide, and triethylamine. In a preferred embodiment, the template agent a is hexamethylenediamine and / or ethanol.

[0037] In step (1), the conditions for the crystallization reaction may include: a temperature of 120~220℃, preferably 140~200℃; and a time of 8~48h, preferably 12~30h.

[0038] In step (1), the crystallization reaction is preferably carried out in a reactor with a polytetrafluoroethylene liner.

[0039] In step (1), the process of separating the solid phase material from the reacted material is called solid-liquid separation. The solid-liquid separation method can be selected from, but is not limited to, gravity sedimentation, filtration separation and centrifugal separation, with centrifugal separation being preferred.

[0040] In step (2), the liquid-to-solid ratio of the fatty amine to the solid material can be 0.3-3 mL / g, preferably 0.5-2 mL / g.

[0041] In step (2), the purpose of adding the aliphatic amine is to promote the orderly arrangement of crystals, thereby facilitating the formation of metastable pure silicon ten-membered ring molecular sieve nanocrystals. The aliphatic amine can be a C12-C18 aliphatic amine. In a specific embodiment, the aliphatic amine is selected from, but is not limited to, at least one of oleylamine (i.e., 9-octadeceneamine), octadecylamine, and dodecylamine. In the most preferred embodiment, the aliphatic amine is oleylamine.

[0042] In step (2), the inorganic base is preferably used in the form of an alkaline solution. The concentration of the alkaline solution can be 0.003~0.015 mol / L, preferably 0.005~0.01 mol / L.

[0043] In step (2), the liquid-to-solid ratio of the alkaline solution to the solid material can be 2 to 15 mL / g, preferably 4 to 10 mL / g.

[0044] In this invention, the inorganic base may be selected from, but is not limited to, at least one of sodium hydroxide, potassium hydroxide, and ammonia water.

[0045] In step (2), the temperature of the secondary reaction is higher than the temperature of the primary reaction. Preferably, the temperature of the secondary reaction is 30-90°C higher than the temperature of the primary reaction, and more preferably 40-80°C higher.

[0046] In step (2), the conditions for the primary reaction may include: a temperature of 20~40℃, preferably 25~30℃; and a time of 3~15h, preferably 6~12h. The primary reaction is preferably carried out under stirring, and the stirring rate may be 100~300rpm.

[0047] In step (2), the conditions for the secondary reaction may include: a temperature of 60~120℃, preferably 80~100℃; and a time of 6~30h, preferably 12~24h. The secondary reaction is preferably carried out under stirring, and the stirring rate may be 100~300rpm.

[0048] In step (2), the amount of ZSM-23 seed crystals used is not particularly limited and can be operated according to the conventional seed crystal usage in the art. In a specific embodiment, the amount of ZSM-23 seed crystals used is 0.1 to 8 parts by weight relative to 100 parts by weight of the solid phase material, preferably 0.5 to 5 parts by weight.

[0049] In step (2), preferably, the specific operation process of mixing the solid material, fatty amine and inorganic base is as follows: the solid material obtained in step (1) is mixed with the fatty amine, and then the alkaline solution is added to the mixture.

[0050] In step (2), under preferred conditions, the specific operation process for adding ZSM-23 seed crystals is as follows: dispersing ZSM-23 seed crystals in deionized water to form a seed crystal solution, and then adding the seed crystal solution. The liquid-to-solid ratio of the deionized water to the ZSM-23 seed crystals can be 5~70 mL / g, preferably 10~60 mL / g.

[0051] According to the preparation method of ZSM-23 molecular sieve of the present invention, in step (3), the molar ratio of the template agent b, the aluminum source (calculated as Al2O3) and the mixture (calculated as SiO2) can be (0.01~0.1):(0.002~0.015):1, preferably (0.02~0.08):(0.005~0.01):1.

[0052] In step (3), in a preferred embodiment, the specific operation process for mixing the aluminum source, template agent b, and the mixture is as follows: prepare an aqueous solution containing the aluminum source and template agent b, and then mix it with the mixture to obtain a gel. In the aqueous solution containing the aluminum source and template agent b, the molar ratio of water to aluminum source (calculated as Al2O3) can be 300~3000, preferably 400~2000.

[0053] In this invention, the template agent b is a template agent capable of guiding the formation of ZSM-23 molecular sieve. The specific type of substance is not particularly limited in this invention, and conventional template agents in the art can be selected. In specific embodiments, the template agent b can be selected from, but is not limited to, one or any combination of at least two of pyrrolidine, isopropylamine, N,N-dimethylformamide, dimethylamine, and ethylenediamine. In the most preferred embodiment, the template agent b is pyrrolidine.

[0054] In this invention, the aluminum source can be any aluminum source conventionally used in the art. In specific embodiments, the aluminum source can be selected from, but is not limited to, one or any combination of at least two of aluminum sulfate, aluminum isopropoxide, sodium aluminate, and aluminum hydroxide. In the most preferred embodiment, the aluminum source is aluminum sulfate.

[0055] In step (3), the crystallization conditions may include: a temperature of 180~220℃ and a time of 24~72h.

[0056] In step (3), the drying conditions may include: a temperature of 80~120℃ and a time of 6~12h.

[0057] In step (3), the calcination conditions may include: a temperature of 540~560℃ and a time of 3~8h.

[0058] The ZSM-23 molecular sieve prepared according to the method of the present invention can achieve precise control of the Al sites of the ZSM-23 molecular sieve, so that the Al sites are mainly distributed on the outer surface of the molecular sieve, which is conducive to the enrichment of weak B acid sites at the pores and the outer surface of the molecular sieve. As a result, the ZSM-23 molecular sieve not only has high catalytic activity, but also significantly improves the catalytic reaction performance mainly based on the pore adsorption mechanism.

[0059] The present invention also provides a ZSM-23 molecular sieve prepared by the above method. The Brønsted acid sites of this ZSM-23 molecular sieve are mainly distributed at the pore openings and on the outer surface, and are predominantly weak Brønsted acid sites, exhibiting high catalytic activity and excellent catalytic reaction performance mainly based on the pore opening adsorption mechanism.

[0060] The hydrogenation catalyst of the present invention contains a support and an active component attached to the support, wherein the support is the ZSM-23 molecular sieve described above.

[0061] In the hydrogenation catalyst, the content of the active component can be 0.1~5 wt.%, preferably 0.2~2 wt.%. The active component can be a conventional metal active component in the art. In a preferred embodiment, the active component is a noble metal component (such as Pt).

[0062] The present invention also provides the application of the above-mentioned hydrogenation catalyst in the hydrocracking reaction of long-chain alkanes, the hydrocracking reaction of olefins, or the isomerization reaction of alkanes.

[0063] In practical applications, due to the specific distribution characteristics of Brønsted acid sites in the ZSM-23 molecular sieve used as a carrier, high catalytic activity can be obtained during application, and the reaction performance of ZSM-23 molecular sieve, which is mainly based on pore adsorption mechanism, has been significantly improved.

[0064] The following examples further illustrate the ZSM-23 molecular sieve, its preparation method, and its applications according to the present invention. These examples are implemented based on the technical solution of the present invention, providing detailed implementation methods and specific operating procedures; however, the scope of protection of the present invention is not limited to the following examples.

[0065] Unless otherwise specified, the experimental methods used in the following embodiments are conventional methods in the art. Unless otherwise specified, the experimental materials used in the following embodiments are commercially available.

[0066] Example 1 4.68 g of hexamethylenediamine was dissolved in 54 g of deionized water, and then 6 g of fumed silica was added. After stirring at room temperature (25 °C) for 1 h, the mixture was transferred to a 100 mL reactor with a polytetrafluoroethylene liner. The mixture was crystallized at 150 °C for 24 h, then quenched and centrifuged to obtain 6.43 g of solid material.

[0067] Add 10 mL of oleylamine to the solid material, mix thoroughly in a shaker, and stir at room temperature for 0.5 h at a stirring rate of 200 rpm. Then add 42 mL of 0.008 mol / L NaOH solution to the mixture and carry out a first reaction at 25 °C with stirring for 6 h at a stirring rate of 200 rpm to obtain mixture A. Add 0.18 g of ZSM-23 seed crystals to deionized water to prepare 10 mL of ZSM-23 seed crystal solution, add it to mixture A, and carry out a second reaction at 80 °C with stirring for 16 h at a stirring rate of 300 rpm to obtain mixture B.

[0068] 0.67 g of Al2(SO4)3·18H2O and 0.40 g of pyrrolidine were added sequentially to 20 mL of deionized water to obtain a clear solution C. Solution C was added to the mixture B, and after thorough mixing, the final mixture was transferred to a 150 mL reactor lined with polytetrafluoroethylene and crystallized at 180 °C for 48 h. After crystallization, the mixture was filtered, washed, dried at 100 °C for 12 h, and then calcined at 550 °C for 4 h to obtain ZSM-23 molecular sieve Z-1 (its XRD pattern is shown in Figure 1). Figure 1 (As shown).

[0069] Analysis using pyridine adsorption infrared spectroscopy and 2,6-dimethylpyridine adsorption infrared spectroscopy revealed that the total pyridine Brønsted acid content of Z-1 molecular sieve ZSM-23 was 0.184 mmol / g, and the total Brønsted acid content of 2,6-dimethylpyridine Brønsted acid was 0.164 mmol / g, with a ratio of 89.1:100. Among the Brønsted acid in 2,6-dimethylpyridine Brønsted acid, the content of Brønsted acid with a desorption temperature <250℃ (i.e., weak Brønsted acid) was 0.149 mmol / g, with a ratio of Brønsted acid with a desorption temperature <250℃ to the total Brønsted acid content of 2,6-dimethylpyridine Brønsted acid being 90.8:100.

[0070] The bulk SiO2 / Al2O3 (molar ratio) of the ZSM-23 molecular sieve Z-1 is 97, and the outer surface SiO2 / Al2O3 (molar ratio) is 46.

[0071] Example 2 17.43 g of hexamethylenediamine was dissolved in 216 g of deionized water, and then 18 g of fumed silica was added. After stirring at room temperature (25 °C) for 1 h, the mixture was transferred to a 300 mL reactor with a polytetrafluoroethylene liner. The mixture was crystallized at 200 °C for 12 h, then quenched and centrifuged to obtain 18.97 g of solid material.

[0072] Add 37 mL of oleylamine to the solid material, mix thoroughly in a shaker, and stir at room temperature for 0.5 h at a stirring rate of 150 rpm. Then add 76 mL of 0.01 mol / L NaOH solution to the mixture and carry out a first reaction at 25 °C with stirring for 12 h at a stirring rate of 150 rpm to obtain mixture A. Add 0.9 g of ZSM-23 seed crystals to deionized water to prepare 30 mL of ZSM-23 seed crystal solution, add it to mixture A, and carry out a second reaction at 100 °C with stirring for 20 h at a stirring rate of 300 rpm to obtain mixture B.

[0073] 0.67 g of Al2(SO4)3·18H2O and 0.85 g of pyrrolidine were added sequentially to 20 mL of deionized water to obtain a clear solution C. Solution C was added to the mixture B, and after thorough mixing, the final mixture was transferred to a 200 mL reactor lined with polytetrafluoroethylene and crystallized at 200 °C for 36 h. After crystallization, the mixture was filtered, washed, dried at 100 °C for 12 h, and then calcined at 550 °C for 4 h to obtain ZSM-23 molecular sieve Z-2.

[0074] Analysis using pyridine adsorption infrared spectroscopy and 2,6-dimethylpyridine adsorption infrared spectroscopy revealed that the total pyridine Brønsted acid content of ZSM-23 molecular sieve Z-2 was 0.179 mmol / g, and the total Brønsted acid content of 2,6-dimethylpyridine Brønsted acid was 0.154 mmol / g, with a ratio of 86.0:100. Among the Brønsted acid in 2,6-dimethylpyridine Brønsted acid, the amount of Brønsted acid with a desorption temperature <250℃ (i.e., weak Brønsted acid) was 0.130 mmol / g, and the ratio of the amount of Brønsted acid with a desorption temperature <250℃ to the total Brønsted acid content of 2,6-dimethylpyridine Brønsted acid was 84.4:100.

[0075] The bulk SiO2 / Al2O3 (molar ratio) of the ZSM-23 molecular sieve Z-2 is 246, and the SiO2 / Al2O3 (molar ratio) on the outer surface is 57.

[0076] Example 3 4.68 g of hexamethylenediamine was dissolved in 54 g of deionized water, and then 6 g of fumed silica was added. After stirring at room temperature (25 °C) for 1 h, the mixture was transferred to a 100 mL reactor with a polytetrafluoroethylene liner. The mixture was crystallized at 170 °C for 24 h, then quenched and centrifuged to obtain 6.34 g of solid material.

[0077] Add 6 mL of oleylamine to the solid material, mix thoroughly in a shaker, and stir at room temperature for 0.5 h at a stirring rate of 200 rpm. Then add 63 mL of 0.005 mol / L NaOH solution to the mixture and carry out a first reaction at 25 °C with stirring for 6 h at a stirring rate of 200 rpm to obtain mixture A. Add 0.18 g of ZSM-23 seed crystals to deionized water to prepare 10 mL of ZSM-23 seed crystal solution, add it to mixture A, and carry out a second reaction at 80 °C with stirring for 16 h at a stirring rate of 200 rpm to obtain mixture B.

[0078] 0.17 g of Al2(SO4)3·18H2O and 0.40 g of pyrrolidine were added sequentially to 20 mL of deionized water to obtain a clear solution C. Solution C was added to the mixture B, and after thorough mixing, the final mixture was transferred to a 150 mL reactor lined with polytetrafluoroethylene and crystallized at 200 °C for 48 h. After crystallization, the mixture was filtered, washed, dried at 100 °C for 12 h, and then calcined at 550 °C for 4 h to obtain ZSM-23 molecular sieve Z-3.

[0079] Analysis using pyridine adsorption infrared spectroscopy and 2,6-dimethylpyridine adsorption infrared spectroscopy revealed that the total pyridine Brønsted acid content of Z-3 molecular sieve ZSM-23 was 0.171 mmol / g, and the total Brønsted acid content of 2,6-dimethylpyridine Brønsted acid was 0.131 mmol / g, with a ratio of 76.6:100. Among the Brønsted acid in 2,6-dimethylpyridine Brønsted acid, the content of Brønsted acid with a desorption temperature <250℃ (i.e., weak Brønsted acid) was 0.104 mmol / g, with a ratio of Brønsted acid with a desorption temperature <250℃ to the total Brønsted acid content of 2,6-dimethylpyridine Brønsted acid being 79.4:100.

[0080] The bulk SiO2 / Al2O3 (molar ratio) of this ZSM-23 molecular sieve Z-3 is 387, and the SiO2 / Al2O3 (molar ratio) on the outer surface is 71.

[0081] Example 4 4.68 g of hexamethylenediamine was dissolved in 54 g of deionized water, and then 6 g of fumed silica was added. After stirring at room temperature (25 °C) for 1 h, the mixture was transferred to a 100 mL reactor with a polytetrafluoroethylene liner. The mixture was crystallized at 150 °C for 24 h, then quenched and centrifuged to obtain 6.61 g of solid material.

[0082] Add 3.3 mL of oleylamine to the solid material, mix thoroughly in a shaker, and stir at room temperature for 0.5 h at a stirring rate of 250 rpm. Then add 30 mL of 0.008 mol / L NaOH solution to the mixture and carry out a first reaction at 25 °C with stirring for 8 h at a stirring rate of 250 rpm to obtain mixture A. Add 0.03 g of ZSM-23 seed crystals to deionized water to prepare 5 mL of ZSM-23 seed crystal solution, add it to mixture A, and carry out a second reaction at 60 °C with stirring for 30 h at a stirring rate of 200 rpm to obtain mixture B.

[0083] 0.44 g of Al2(SO4)3·18H2O and 0.15 g of pyrrolidine were added sequentially to 15 mL of deionized water to obtain a clear solution C. Solution C was added to the mixture B, and after thorough mixing, the final mixture was transferred to a 100 mL reactor lined with polytetrafluoroethylene and crystallized at 180 °C for 24 h. After crystallization, the mixture was filtered, washed, dried at 100 °C for 12 h, and then calcined at 550 °C for 4 h to obtain ZSM-23 molecular sieve Z-4.

[0084] Analysis using pyridine adsorption infrared spectroscopy and 2,6-dimethylpyridine adsorption infrared spectroscopy revealed that the total pyridine Brønsted acid content of Z-4 molecular sieve ZSM-23 was 0.123 mmol / g, and the total Brønsted acid content of 2,6-dimethylpyridine Brønsted acid was 0.104 mmol / g, with a ratio of 84.6:100. Among the Brønsted acid in 2,6-dimethylpyridine Brønsted acid, the content of Brønsted acid with a desorption temperature <250℃ (i.e., weak Brønsted acid) was 0.091 mmol / g, with a ratio of Brønsted acid with a desorption temperature <250℃ to the total Brønsted acid content of 2,6-dimethylpyridine Brønsted acid being 87.5:100.

[0085] The bulk SiO2 / Al2O3 (molar ratio) of the ZSM-23 molecular sieve Z-4 ​​is 137, and the outer surface SiO2 / Al2O3 (molar ratio) is 64.

[0086] Example 5 ZSM-23 molecular sieve was prepared according to the method in Example 1, except that the same volume of dodecylamine was used instead of oleylamine to prepare ZSM-23 molecular sieve Z-5.

[0087] Analysis using pyridine adsorption infrared spectroscopy and 2,6-dimethylpyridine adsorption infrared spectroscopy revealed that the total pyridine Brønsted acid content of Z-5 molecular sieve ZSM-23 was 0.137 mmol / g, and the total Brønsted acid content of 2,6-dimethylpyridine Brønsted acid was 0.109 mmol / g, with a ratio of 79.6:100. Among the Brønsted acid in 2,6-dimethylpyridine Brønsted acid, the content of Brønsted acid with a desorption temperature <250℃ (i.e., weak Brønsted acid) was 0.077 mmol / g, with a ratio of Brønsted acid with a desorption temperature <250℃ to the total Brønsted acid content of 2,6-dimethylpyridine Brønsted acid being 70.6:100.

[0088] The bulk SiO2 / Al2O3 (molar ratio) of the ZSM-23 molecular sieve Z-5 is 122, and the outer surface SiO2 / Al2O3 (molar ratio) is 81.

[0089] Example 6 ZSM-23 molecular sieve was prepared according to the method in Example 1, except that undecylamine was used instead of oleylamine in the same volume to prepare ZSM-23 molecular sieve Z-6.

[0090] Analysis using pyridine adsorption infrared spectroscopy and 2,6-dimethylpyridine adsorption infrared spectroscopy revealed that the total pyridine Brønsted acid content of Z-6 molecular sieve ZSM-23 was 0.118 mmol / g, and the total Brønsted acid content of 2,6-dimethylpyridine Brønsted acid was 0.092 mmol / g, with a ratio of 77.9:100. Among the Brønsted acid in 2,6-dimethylpyridine Brønsted acid, the content of Brønsted acid with a desorption temperature <250℃ (i.e., weak Brønsted acid) was 0.063 mmol / g, with a ratio of Brønsted acid with a desorption temperature <250℃ to the total Brønsted acid content of 2,6-dimethylpyridine Brønsted acid being 68.5:100.

[0091] The bulk SiO2 / Al2O3 (molar ratio) of the ZSM-23 molecular sieve Z-6 is 133, and the outer surface SiO2 / Al2O3 (molar ratio) is 90.

[0092] Example 7 4.68 g of hexamethylenediamine was dissolved in 54 g of deionized water, and then 6 g of fumed silica was added. After stirring at room temperature (25 °C) for 1 h, the mixture was transferred to a 100 mL reactor with a polytetrafluoroethylene liner. The mixture was crystallized at 200 °C for 18 h, then quenched and centrifuged to obtain 6.41 g of solid material.

[0093] Add 12 mL of dodecylamine to the solid material, mix thoroughly in a shaker, and stir at room temperature for 0.5 h at a stirring rate of 200 rpm. Then add 40 mL of 0.01 mol / L NaOH solution to the mixture and carry out a first reaction at 25 °C with stirring for 12 h at a stirring rate of 200 rpm to obtain mixture A. Add 0.18 g of ZSM-23 seed crystals to deionized water to prepare 10 mL of ZSM-23 seed crystal solution, add it to mixture A, and carry out a second reaction at 80 °C with stirring for 16 h at a stirring rate of 300 rpm to obtain mixture B.

[0094] 0.17 g of Al2(SO4)3·18H2O and 0.40 g of pyrrolidine were added sequentially to 20 mL of deionized water to obtain a clear solution C. Solution C was added to the mixture B, and after thorough mixing, the final mixture was transferred to a 150 mL reactor lined with polytetrafluoroethylene and crystallized at 180 °C for 48 h. After crystallization, the mixture was filtered, washed, dried at 100 °C for 12 h, and then calcined at 550 °C for 4 h to obtain ZSM-23 molecular sieve Z-7.

[0095] Analysis using pyridine adsorption infrared spectroscopy and 2,6-dimethylpyridine adsorption infrared spectroscopy revealed that the total pyridine Brønsted acid content of Z-7 molecular sieve ZSM-23 was 0.180 mmol / g, and the total Brønsted acid content of 2,6-dimethylpyridine Brønsted acid was 0.172 mmol / g, with a ratio of 2,6-dimethylpyridine Brønsted acid content to pyridine Brønsted acid content of 95.6:100. Among the Brønsted acid in 2,6-dimethylpyridine Brønsted acid, the content of Brønsted acid with a desorption temperature <250℃ (i.e., weak Brønsted acid) was 0.159 mmol / g, with a ratio of Brønsted acid with a desorption temperature <250℃ to the total Brønsted acid content of 2,6-dimethylpyridine Brønsted acid of 92.4:100.

[0096] The bulk SiO2 / Al2O3 (molar ratio) of the ZSM-23 molecular sieve Z-7 is 364, and the SiO2 / Al2O3 (molar ratio) on the outer surface is 82.

[0097] Example 8 ZSM-23 molecular sieve Z-8 was prepared according to the method in Example 1, except that 0.40 g of isopropylamine was used instead of 0.40 g of pyrrolidine.

[0098] Analysis using pyridine adsorption infrared spectroscopy and 2,6-dimethylpyridine adsorption infrared spectroscopy revealed that the total pyridine Brønsted acid content of Z-8 molecular sieve ZSM-23 was 0.134 mmol / g, and the total Brønsted acid content of 2,6-dimethylpyridine Brønsted acid was 0.096 mmol / g, with a ratio of 71.6:100. Among the Brønsted acid in 2,6-dimethylpyridine Brønsted acid, the content of Brønsted acid with a desorption temperature <250℃ (i.e., weak Brønsted acid) was 0.070 mmol / g, with a ratio of Brønsted acid with a desorption temperature <250℃ to the total Brønsted acid content of 2,6-dimethylpyridine Brønsted acid being 72.9:100.

[0099] The bulk SiO2 / Al2O3 (molar ratio) of the ZSM-23 molecular sieve Z-8 is 203, and the SiO2 / Al2O3 (molar ratio) on the outer surface is 87.

[0100] Example 9 4.68 g of hexamethylenediamine was dissolved in 54 g of deionized water, and then 6 g of fumed silica was added. After stirring at room temperature (25 °C) for 1 h, the mixture was transferred to a 100 mL reactor with a polytetrafluoroethylene liner. The mixture was crystallized at 150 °C for 24 h, then quenched and centrifuged to obtain 6.43 g of solid material.

[0101] Add 10 mL of oleylamine to the solid material, mix thoroughly in a shaker, and stir at room temperature for 0.5 h at a stirring rate of 200 rpm. Then add 42 mL of 0.005 mol / L NaOH solution to the mixture and carry out a first reaction at 25 °C with stirring for 6 h at a stirring rate of 200 rpm to obtain mixture A. Add 0.18 g of ZSM-23 seed crystals to deionized water to prepare 10 mL of ZSM-23 seed crystal solution, add it to mixture A, and carry out a second reaction at 80 °C with stirring for 16 h at a stirring rate of 300 rpm to obtain mixture B.

[0102] 0.34 g of Al2(SO4)3·18H2O and 0.35 g of isopropylamine were added sequentially to 20 mL of deionized water to obtain a clear solution C. Solution C was added to the mixture B, and after thorough mixing, the final mixture was transferred to a 150 mL reactor lined with polytetrafluoroethylene and crystallized at 170 °C for 48 h. After crystallization, the mixture was filtered, washed, dried at 100 °C for 12 h, and then calcined at 550 °C for 4 h to obtain ZSM-23 molecular sieve Z-9.

[0103] Analysis using pyridine adsorption infrared spectroscopy and 2,6-dimethylpyridine adsorption infrared spectroscopy revealed that the total pyridine Brønsted acid content of Z-9 molecular sieve ZSM-23 was 0.124 mmol / g, and the total Brønsted acid content of 2,6-dimethylpyridine Brønsted acid was 0.103 mmol / g, with a ratio of 83.0:100. Among the Brønsted acid in 2,6-dimethylpyridine Brønsted acid, the content of Brønsted acid with a desorption temperature <250℃ (i.e., weak Brønsted acid) was 0.074 mmol / g, with a ratio of Brønsted acid with a desorption temperature <250℃ to the total Brønsted acid content of 2,6-dimethylpyridine Brønsted acid being 71.8:100.

[0104] The bulk SiO2 / Al2O3 (molar ratio) of the ZSM-23 molecular sieve Z-9 is 189, and the SiO2 / Al2O3 (molar ratio) on the outer surface is 88.

[0105] Example 10 4.68 g of hexamethylenediamine was dissolved in 54 g of deionized water, and then 6 g of fumed silica was added. After stirring at room temperature (25 °C) for 1 h, the mixture was transferred to a 100 mL reactor with a polytetrafluoroethylene liner. The mixture was crystallized at 200 °C for 18 h, then quenched and centrifuged to obtain 6.41 g of solid material.

[0106] Add 12 mL of oleylamine to the solid material, mix thoroughly in a shaker, and stir at room temperature for 0.5 h at a stirring rate of 200 rpm. Then add 42 mL of 0.01 mol / L NaOH solution to the mixture and carry out a first reaction at 25 °C with stirring for 12 h at a stirring rate of 200 rpm to obtain mixture A. Add 0.18 g of ZSM-23 seed crystals to deionized water to prepare 10 mL of ZSM-23 seed crystal solution, add it to mixture A, and carry out a second reaction at 80 °C with stirring for 16 h at a stirring rate of 300 rpm to obtain mixture B.

[0107] 0.17 g Al2(SO4)3·18H2O and 0.40 g isopropylamine were added sequentially to 20 mL of deionized water to obtain a clear solution C. Solution C was added to the mixture B, and after thorough mixing, the final mixture was transferred to a 150 mL reactor lined with polytetrafluoroethylene and crystallized at 180 °C for 48 h. After crystallization, the mixture was filtered, washed, dried at 100 °C for 12 h, and then calcined at 550 °C for 4 h to obtain ZSM-23 molecular sieve Z-10.

[0108] Analysis using pyridine adsorption infrared spectroscopy and 2,6-dimethylpyridine adsorption infrared spectroscopy revealed that the total pyridine Brønsted acid content of Z-10 molecular sieve ZSM-23 was 0.127 mmol / g, and the total Brønsted acid content of 2,6-dimethylpyridine Brønsted acid was 0.114 mmol / g, with a ratio of 89.8:100. Among the Brønsted acid in 2,6-dimethylpyridine Brønsted acid, the content of Brønsted acid with a desorption temperature <250℃ (i.e., weak Brønsted acid) was 0.103 mmol / g, with a ratio of Brønsted acid with a desorption temperature <250℃ to the total Brønsted acid content of 2,6-dimethylpyridine Brønsted acid being 90.3:100.

[0109] The bulk SiO2 / Al2O3 (molar ratio) of the ZSM-23 molecular sieve Z-10 is 372, and the outer surface SiO2 / Al2O3 (molar ratio) is 75.

[0110] Comparative Example 1 This comparative example follows the ZSM-23 molecular sieve preparation method described in patent application CN109516471A.

[0111] 0.079 g NaOH, 0.163 g Al2(SO4)3·18H2O, 0.438 g pyrrolidine, and 1.48 g fumed silica were sequentially dissolved in 20.0 g deionized water and thoroughly mixed to obtain gel A. The molar ratio of each component was SiO2 from the silicon source: Al2O3 from the aluminum source: PY: NaOH:H2O = 1 : 0.01 : 0.25 : 0.083 : 45. Gel A was heated in a 180℃ constant temperature oven for 12 h and then cooled to room temperature. 0.119 g NaOH, 0.489 g Al2(SO4)3·18H2O, and 2.22 g fumed silica were sequentially dissolved in 30.0 g deionized water and stirred thoroughly to obtain gel B. The molar ratio of each component was SiO2 from the silicon source: Al2O3 from the aluminum source: NaOH: H2O = 1 : 0.02 : 0.083 : 45; Gel B was added to gel A and mechanically stirred for 1 h to obtain a uniform white gel. This gel was transferred to a 100 mL hydrothermal reactor and crystallized at 180 °C for 44 h. The resulting product was then filtered, washed, and dried at 65 °C for 24 h to obtain ZSM-23 molecular sieve DZ-1.

[0112] Analysis using pyridine adsorption infrared spectroscopy and 2,6-dimethylpyridine adsorption infrared spectroscopy revealed that the total pyridine Brønsted acid content of the ZSM-23 molecular sieve DZ-1 was 0.271 mmol / g, and the total Brønsted acid content of 2,6-dimethylpyridine Brønsted acid was 0.116 mmol / g, with a ratio of 42.8:100. Among the Brønsted acid in the 2,6-dimethylpyridine Brønsted acid, the amount of Brønsted acid with a desorption temperature <250℃ (i.e., weak Brønsted acid) was 0.034 mmol / g, with a ratio of Brønsted acid with a desorption temperature <250℃ to the total Brønsted acid content of 2,6-dimethylpyridine Brønsted acid being 29.3:100.

[0113] The bulk SiO2 / Al2O3 (molar ratio) of the ZSM-23 molecular sieve DZ-1 is 48, and the outer surface SiO2 / Al2O3 (molar ratio) is 44.

[0114] Comparative Example 2 ZSM-23 molecular sieve was prepared according to the method in Example 1, except that oleylamine was not added, and ZSM-23 molecular sieve DZ-2 was obtained.

[0115] Analysis using pyridine adsorption infrared spectroscopy and 2,6-dimethylpyridine adsorption infrared spectroscopy revealed that the total pyridine Brønsted acid content of the ZSM-23 molecular sieve DZ-2 was 0.176 mmol / g, and the total Brønsted acid content of 2,6-dimethylpyridine Brønsted acid was 0.081 mmol / g, with a ratio of 46.0:100. Among the Brønsted acid in the 2,6-dimethylpyridine Brønsted acid, the Brønsted acid content with a desorption temperature <250℃ (i.e., weak Brønsted acid) was 0.037 mmol / g, with a ratio of 45.7:100 between the weak Brønsted acid content with a desorption temperature <250℃ and the total Brønsted acid content of the 2,6-dimethylpyridine Brønsted acid.

[0116] The bulk SiO2 / Al2O3 (molar ratio) of the ZSM-23 molecular sieve DZ-2 is 94, and the SiO2 / Al2O3 (molar ratio) on the outer surface is 89.

[0117] The relevant parameters of the ZSM-23 molecular sieves prepared in the above embodiments and comparative examples are shown in Table 1 below.

[0118] Table 1. Relevant parameters of ZSM-23 molecular sieves prepared in the examples and comparative examples. Application Examples 1-10 and Comparative Examples 1-2 Catalyst powders were prepared by loading 0.5 wt.% of noble metal Pt onto ZSM-23 molecular sieve samples prepared in Examples 1-10 and Comparative Examples 1-2, respectively, using the samples as carriers.

[0119] The performance of ZSM-23 molecular sieve samples was evaluated in a fixed-bed microreactor: Catalyst powder was compressed into tablets, pulverized into 5-10 mesh particles, and loaded into a fixed-bed microreactor. The hydrogenation of ethylcyclohexane was used as a model reaction, with a mixture of 90 wt.% decahydronaphthalene and 10 wt.% ethylcyclohexane as the reactants. The reaction temperature was 280℃, and the liquid hourly space velocity (LHSV) was 1.0 h⁻¹. -1 The hydrogen-to-oil volume ratio was 800, and the reaction hydrogen pressure was 4.0 MPa. The catalytic results are shown in Table 2 below.

[0120] Table 2 Catalytic Results As can be seen from the results in Table 2 above, the hydrogenation catalyst using the ZSM-23 molecular sieve of the present invention as a support has significantly better effects on the ring-opening and hydrogen isomerization of cycloalkanes.

[0121] 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 ZSM-23 molecular sieve characterized by, The ratio of the 2,6-dimethylpyridine infrared total B acid amount to the pyridine infrared total B acid amount of the ZSM-23 molecular sieve is 65-99:100, preferably 70-97:100, and more preferably 74-95:100; and the ratio of the B acid amount with a desorption temperature < 250℃ to the 2,6-dimethylpyridine infrared total B acid amount in the 2,6-dimethylpyridine infrared B acid is 64-95:100, preferably 67-93:100, and more preferably 70-91:

100.

2. The ZSM-23 molecular sieve of claim 1, wherein, The pyridine infrared total B acid amount of the ZSM-23 molecular sieve is 0.1-0.37 mmol / g, preferably 0.13-0.35 mmol / g, and more preferably 0.15-0.33 mmol / g.

3. The ZSM-23 molecular sieve of claim 1 or 2, wherein, The 2,6-dimethylpyridine infrared total B acid amount of the ZSM-23 molecular sieve is 0.07-0.35 mmol / g, preferably 0.09-0.33 mmol / g, and more preferably 0.11-0.30 mmol / g.

4. The ZSM-23 molecular sieve of any one of claims 1-3, wherein, The B acid amount with a desorption temperature < 250℃ in the 2,6-dimethylpyridine infrared B acid of the ZSM-23 molecular sieve is 0.06-0.31 mmol / g, preferably 0.07-0.30 mmol / g, and more preferably 0.1-0.26 mmol / g.

5. The ZSM-23 molecular sieve of any one of claims 1-4, wherein, The bulk SiO2 / Al2O3 ratio of the ZSM-23 molecular sieve is higher than the external surface SiO2 / Al2O3 ratio by 40-400, preferably by 45-350.

6. The ZSM-23 molecular sieve of claim 1 or 5, wherein, The bulk SiO2 / Al2O3 ratio of the ZSM-23 molecular sieve is 70-500, and the external surface SiO2 / Al2O3 ratio is 40-120. Preferably, the bulk SiO2 / Al2O3 ratio of the ZSM-23 molecular sieve is 90-400, and the external surface SiO2 / Al2O3 ratio is 45-90.

7. A method for preparing a ZSM-23 molecular sieve, characterized by, The method comprises the following steps: (1) performing a crystallization reaction on a mixture of a silicon source, a template agent a, and water, and separating solid material from the reacted material; (2) mixing the solid material, a fatty amine, and an inorganic base, and performing a first reaction, then adding ZSM-23 seeds and performing a second reaction; (3) mixing the mixture obtained in step (2) with an aluminum source and a template agent b, and then performing crystallization, filtration, washing, drying, and calcination in sequence.

8. The method of claim 7, wherein, In step (1), the molar ratio of water, the template agent a, and the silicon source, calculated as SiO2, is (20-80) : (0.1-1) : 1, and preferably (30-70) : (0.15-0.8) :

1. Preferably, the silicon source is one or any combination of two or more of white carbon black, silica sol, water glass, fumed silica, and tetraethyl orthosilicate. Preferably, the template agent a is one or any combination of two or more of hexanediamine, n-hexylamine, ethanol, tetrapropylammonium hydroxide, tetrapropylammonium bromide, and triethylamine. Preferably, the crystallization reaction is performed under conditions including a temperature of 120-220℃ and a time of 8-48 h.

9. The method according to claim 7 or 8, characterized in that, In step (2), the liquid-solid ratio of the fatty amine to the solid phase material is 0.3-3 mL / g, preferably 0.5-2 mL / g; Preferably, the fatty amine is C12-C18 fatty amine, more preferably at least one of oleylamine, octadecylamine and dodecylamine.

10. The method according to any one of claims 7-9, characterized in that, In step (2), the inorganic base is used in the form of a base solution, and the concentration of the base solution is 0.003-0.015 mol / L, preferably 0.005-0.01 mol / L; Preferably, the liquid-solid ratio of the base solution to the solid phase material is 2-15 mL / g, preferably 4-10 mL / g; Preferably, the inorganic base is at least one of sodium hydroxide, potassium hydroxide and ammonia.

11. The method according to any one of claims 7-10, characterized in that, In step (2), the temperature of the secondary reaction is higher than that of the primary reaction. Preferably, the conditions of the primary reaction include: temperature 20-40℃, time 3-15 h; Preferably, the conditions of the secondary reaction include: temperature 60-120℃, time 6-30 h.

12. The method according to any one of claims 7-11, characterized in that, In step (2), the amount of the ZSM-23 seed crystal is 0.1-8 parts by weight, preferably 0.5-5 parts by weight, relative to 100 parts by weight of the solid phase material.

13. The method according to any of claims 7-12, characterized by, In step (3), the molar ratio of the amount of the template b, the amount of the aluminum source calculated as Al2O3 and the amount of the mixture material calculated as SiO2 is (0.01-0.1):(0.002-0.015):1, preferably (0.02-0.08):(0.005-0.01):1; Preferably, the template b is one or at least two or more of any combination of pyrrolidine, isopropylamine, N,N-dimethylformamide, dimethylamine and ethylenediamine; Preferably, the aluminum source is one or at least two or more of any combination of aluminum sulfate, aluminum isopropoxide, sodium aluminate and aluminum hydroxide.

14. The method according to any one of claims 7-13, characterized in that, In step (3), the conditions of the crystallization include: temperature 180-220℃, time 24-72 h; Preferably, the conditions of the drying include: temperature 80-120℃, time 6-12 h; Preferably, the conditions of the calcination include: temperature 540-560℃, time 3-8 h.

15. The ZSM-23 molecular sieve prepared by the method of any one of claims 7-14.

16. A hydrogenation catalyst comprising a support and an active component attached to the support, characterized in that, The carrier is the ZSM-23 molecular sieve of any one of claims 1-6 and 15.

17. The use of the hydrogenation catalyst of claim 16 in long-chain alkane hydrocracking reaction, olefin hydrocracking reaction or alkane isomerization reaction.

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