ZSM-23 Molecular Sieve and Method for Preparing It

Abstract

Provided is a ZSM-23 molecular sieve and a preparation method thereof. The total acid amount of the ZSM-23 molecular sieve is 0.05-0.25 mmol / g, the strong acid content is 5-33% of the total acid amount, and the strong acid refers to an acid whose corresponding desorption temperature in NH3 temperature programmed desorption is above 350°C. The preparation method includes the steps of (1) preparing a mixed solution containing a template agent and amorphous silica-alumina and / or amorphous silica-alumina precursor, (2) adding an alkali source and a silicon source to the mixed solution of step (1), and (3) crystallizing the material obtained in step (2), optionally filtering, washing, drying, and optionally calcining to obtain a ZSM-23 molecular sieve. The method is simple, and the obtained ZSM-23 molecular sieve has a low strong acid content and good thermal stability and hydrothermal stability at the same time, and can be used as an excellent adsorbent or catalyst material.

Description

Detailed description of the invention

[0001] [Technical Field] This invention relates to a ZSM-23 molecular sieve, as well as a method for producing and using the same, and more particularly to a ZSM-23 molecular sieve with a low strong acid content, as well as a method for producing and using the same.

[0002] [Background technology] ZSM-23 molecular sieves are molecular sieve materials with a high SiO2 / Al2O3 ratio and an MTT topology structure, and their one-dimensional teardrop-shaped porous channels are composed of 10-membered rings. Due to their unique porous channel structure and tunable acid properties, ZSM-23 molecular sieves are widely used in the fields of separation, adsorption, and catalysis, playing an irreplaceable role. In particular, in the petrochemical industry, they exhibit excellent performance in the hydrocracking of long-chain alkanes and olefins, and in the isomerization of alkanes and aromatic hydrocarbons. Therefore, preparing ZSM-23 molecular sieves with superior performance is extremely important.

[0003] Currently, there are numerous methods for preparing ZSM-23 molecular sieves. US4076842 was the first to disclose a method for synthesizing ZSM-23 molecular sieves using pyrrolidine as a template agent. Subsequently, US4490342 and US5707601 successively disclosed conditions for synthesizing ZSM-23 molecular sieves in systems using bis-quaternary ammonium salts (diquat-7) or small molecule amines and neutral amines as template agents. CN101214971 discloses a method for synthesizing nano-ZSM-23 molecular sieves. A reaction mixture consisting of an aluminum source, a silicon source, sodium hydroxide, and isopropylamine was hydrothermally crystallized to produce ZSM-23 molecular sieves with an average grain diameter of 100 nm or less. CN101613114 discloses a method for synthesizing ZSM-23 molecular sieves using ZSM-22 or ZSM-23 molecular sieves as crystalline species and a small number of template agents, such as ethylamine and n-butylamine. CN102897785 describes a stepwise process in which an organic template agent or an aqueous solution thereof is mixed with an aluminum source in a sealed reaction vessel at 50-190°C for a certain period of time; then a silicon source, organic template agent, water, and crystalline species are added; and the reaction system is hydrothermally crystallized at high temperature to prepare HZSM-23 molecular sieves. Furthermore, CN102992346 discloses a method for synthesizing ZSM-23 molecular sieves without template agents, in which water and an aluminum source are mixed, a sodium source and a silicon source are added; the resulting mixture is uniformly stirred, crystalline species are added; and the reaction system is hydrothermally crystallized to produce the raw material powder for ZSM-23 molecular sieves.

[0004] Among the publicly available techniques for ZSM-23 molecular sieves, the focus has mainly been on exploring the synthesis of new template agents, improving the structure of their porous channels, or reducing preparation costs by improving the synthesis process. There are few methods available to adjust its acidity. A paper (Journal of Catalysis, 1990, 121, 89-98) reported a method to increase the weak acid content of ZSM-23 by isomorphic substitution of Fe atoms with Al atoms. A paper (Ind. Eng. Chem. Res. 2013, 52, 15359-15365) disclosed a method to adjust the acidity distribution of ZSM-23 and thereby adjust its reaction performance by adding auxiliary MgO in a later step. However, these techniques have limited ability to adjust the acidity of the molecular sieves, and the prepared ZSM-23 molecular sieves still have a relatively high acid content, limiting the use of ZSM-23 molecular sieves in the field of shape-selective catalysis.

[0005] [Summary of the Invention] To overcome the shortcomings of existing technologies, the present invention provides a ZSM-23 molecular sieve, as well as a method for preparing and using the same. The ZSM-23 molecular sieve has a low strong acid content, and the method for preparing the ZSM-23 molecular sieve is simple.

[0006] The present invention relates to a ZSM-23 molecular sieve, wherein the total acid content of the ZSM-23 molecular sieve is 0.05 to 0.25 mmol / g, preferably 0.06 to 0.22 mmol / g, more preferably 0.06 to 0.20 mmol / g; the strong acid content of the ZSM-23 molecule is 5 to 33% of the total acid content, preferably 7 to 33%, more preferably 9 to 33%, or even more preferably 7 to 31%, and even more preferably 10 to 28%; where the strong acid refers to an acid whose desorption temperature in NH3 thermal desorption (NH3-TPD) is 350°C or higher; and optionally the ZSM-23 molecular sieve is calcined or uncalcined. In the present invention, ZSM-23 molecular sieve refers to the product obtained by drying after crystallization in molecular sieve preparation (i.e., uncalcined), or the product obtained by drying and calcining after crystallization in molecular sieve preparation (i.e., calcined).

[0007] According to the ZSM-23 molecular sieve described above, the particle size of the ZSM-23 molecular sieve is 100 to 700 nm, preferably 200 to 600 nm, and more preferably 300 to 500 nm.

[0008] According to the ZSM-23 molecular sieve described above, the ZSM-23 molecular sieve has an SiO2 / Al2O3 molar ratio of 40-300 and a specific surface area of ​​200-400 m². 2 The density is / g, and the pore volume is 0.25-0.50 cm³. 3 The amount is / g; preferably, the ZSM-23 molecular sieve has an SiO2 / Al2O3 molar ratio of 40-200 or 50-200 and a specific surface area of ​​280-370 m². 2 The density is / g, and the pore volume is 0.28-0.40 cm³. 3 It is / g.

[0009] According to the ZSM-23 molecular sieve described above, the ZSM-23 molecular sieve has a relative crystallinity of 95-130%, and a relative crystallinity of 93-120% after hydrothermal treatment with steam at 600°C for 2 hours; preferably, the relative crystallinity is 98-120%, and a relative crystallinity of 95-115% after hydrothermal treatment with steam at 600°C for 2 hours.

[0010] This invention provides a method for preparing ZSM-23 molecular sieves, the method comprising the following steps: (1) A step of preparing a mixed solution containing a template agent and amorphous silica-alumina and / or amorphous silica-alumina precursor; (2) A step of adding an alkali source and a silicon source to the mixed solution from step (1); (3) A step of producing a ZSM-23 molecular sieve by crystallizing the substance obtained in step (2) (for example, by static crystallization, i.e., by crystallization without stirring), optionally by filtration, washing, drying, and optionally by calcination.

[0011] According to the method described above, in step (1), the template agent is one or more of isopropylamine, pyrrolidine, N,N-dimethylformamide, and dimethylamine.

[0012] According to the method described above, in step (1), amorphous silica-alumina and / or amorphous silica-alumina precursors are derived from an alkaline aluminum source (e.g., aluminates or metaaluminates such as sodium aluminate, potassium aluminate, sodium metaaluminate, and potassium metaaluminate); in other words, strong acid groups, such as sulfate groups and nitrate groups, are excluded from amorphous silica-alumina and / or amorphous silica-alumina precursors.

[0013] According to the method described above, in step (1), the molar ratio of silicon (as silica):aluminum (as alumina) in the mixed solution is 1:(0.10~0.85), preferably 1:(0.20~0.79), and more preferably 1:(0.24~0.78); and the molar ratio of aluminum (as alumina):the template agent is 1:(10~100), preferably 1:(15~85), and more preferably 1:(20~65).

[0014] According to the above method, in step (1), an amorphous silica-alumina precursor is prepared by the carbonization method, and then a template agent is added to the amorphous silica-alumina precursor to form a mixed solution.

[0015] The method for preparing an amorphous silica-alumina precursor according to a non-limiting embodiment of the present invention includes the steps of preparing a solution of an aluminum source (i.e., an alkaline aluminum source, such as aluminates like sodium aluminate, potassium aluminate, preferably sodium aluminate), and a solution of a silicon-containing compound; mixing a part of the solution of the aluminum source with a part of the solution of the silicon-containing compound, introducing CO2 gas to cause gelation, and when the volume of the introduced CO2 gas reaches 50 to 100%, preferably 70 to 90% of the total volume of the introduced CO2 gas, adding the remaining part of the solution of the silicon-containing compound, then introducing any remaining CO2 gas, and optionally aging to obtain an amorphous silica-alumina precursor.

[0016] In the above method for preparing an amorphous silica-alumina precursor, the remaining part of the solution of the silicon-containing compound as silica contains 5 to 85% by weight, preferably 30 to 70% by weight of the total addition amount of the solution of the silicon-containing compound as silica.

[0017] In the above method for preparing an amorphous silica-alumina precursor, the reaction temperature for gelation is 10 to 40°C, preferably 15 to 35°C, and the pH after gelation is controlled to be 9 to 12.

[0018] In the above method for preparing an amorphous silica-alumina precursor, the solution of the silicon-containing compound is water glass and / or sodium silicate solution.

[0019] In the above method for preparing an amorphous silica-alumina precursor, the concentration of the solution of the aluminum source based on the mass of Al2O3 is 15 to 60 g Al2O3 / L, the concentration of the solution of the silicon-containing compound based on the mass of SiO2 is 40 to 260 g SiO2 / L, and the concentration of the CO2 gas is 30 to 60% by volume.

[0020] In the method for preparing the amorphous silica-alumina precursor described above, the aging time is 5 to 60 minutes, preferably 10 to 30 minutes; the aging temperature is 10 to 40 °C, preferably 15 to 35 °C.

[0021] In step (1) of the method described above, the mixed solution is stirred at 10 to 35 °C for 0.2 to 1.5 hours, preferably stirred at 10 to 25 °C for 0.5 to 1 hour.

[0022] In step (2) of the method described above, based on aluminum (as alumina) in the mixed solution of step (1), SiO2:Al2O3:R2O (alkali source, R is an alkali metal such as sodium and potassium):H2O = 1:(0.0025 to 0.025):(0.015 to 0.08):(30 to 80), and the total charge molar ratio of template agent (SDA) / SiO2 = 0.10 to 1.8, preferably SiO2 / Al2O3 is 50 to 200, H2O / SiO2 is 30 to 60, and R2O / SiO2 is 0.025 to 0.06, an alkali source and a silicon source are added to step (1).

[0023] In step (2) of the method described above, the silicon source is one or more of fumed silica, silica sol, and water glass, and the alkali source is one or more of sodium hydroxide, potassium hydroxide, and ammonia water.

[0024] In step (3) of the method described above, crystallization is carried out at 150 to 200 °C for 8 to 72 hours, preferably at 160 to 180 °C for 10 to 48 hours; drying is carried out at 60 to 130 °C for 2 to 12 hours, preferably at 80 to 120 °C for 4 to 8 hours; firing is carried out at 500 to 600 °C for 2 to 8 hours, preferably at 530 to 570 °C for 3 to 6 hours or 4 to 6 hours.

[0025] Specifically, the present invention discloses the following technical solutions.

[0026] 1. The total acid content is 0.05 to 0.25 mmol / g, preferably 0.06 to 0.22 mmol / g, more preferably 0.06 to 0.20 mmol / g; the strong acid content is 5 to 33% of the total acid content, preferably 7 to 33%, more preferably 9 to 33%, or even more preferably 7 to 31%, and even more preferably 10 to 28%; where the strong acid refers to an acid whose desorption temperature in NH3 thermal desorption (NH3-TPD) is 350°C or higher, and optionally a dry calcined component sieve, a ZSM-23 molecular sieve.

[0027] 2. The molecular sieve according to Solution 1, characterized in that the XRD pattern of the ZSM-23 molecular sieve includes a characteristic peak indicated by 2θ degrees: approximately 11.3°+ / -0.3° (e.g., + / -0.2° or + / -0.1°).

[0028] 3. The molecular sieve according to Solution 1 or 2, characterized in that the XRD pattern of the ZSM-23 molecular sieve includes characteristic peaks indicated by 2θ degrees: 11.2~11.5°, 19.5~19.9°, 20.7~21.0°, and 22.8~23.1°.

[0029] 4. A molecular sieve according to any one of Solutions 1 to 3, characterized in that the particle size of the ZSM-23 molecular sieve is 100 to 700 nm, preferably 200 to 600 nm, and more preferably 300 to 500 nm.

[0030] 5. The ZSM-23 molecular sieve has an SiO2 / Al2O3 molar ratio of 35-300 and a specific surface area of ​​200-400 m². 2 The density is / g, and the pore volume is 0.25-0.50 cm³. 3 The amount is / g; preferably, the ZSM-23 molecular sieve has an SiO2 / Al2O3 molar ratio of 38-200 and a specific surface area of ​​280-370 m². 2 The density is / g, and the pore volume is 0.28-0.40 cm³. 3 A molecular sieve according to any of solutions 1 to 4, characterized by being / g.

[0031] 6. The ZSM-23 molecular sieve is characterized in that its relative crystallinity after calcination is 95-130%, and its relative crystallinity after hydrothermal treatment with steam at 600°C for 2 hours is 93-120%; preferably, its relative crystallinity after calcination is 98-120%, and its relative crystallinity after hydrothermal treatment with steam at 600°C for 2 hours is 95-115%, as described in any of Solutions 1 to 5.

[0032] 7. A method for preparing a ZSM-23 molecular sieve according to any one of Solutions 1 to 6, characterized by comprising the following steps: (1) A mixed solution comprising a template agent and amorphous silica-alumina and / or amorphous silica-alumina precursor, preferably wherein the amorphous silica-alumina and / or amorphous silica-alumina precursor is derived from an alkaline aluminum source (e.g., aluminates or metaaluminates such as sodium aluminate, potassium aluminate, sodium metaaluminate, and potassium metaaluminate); (2) A step of adding an alkali source and a silicon source to the mixed solution from step (1); (3) A step of crystallizing the substance obtained in step (2), optionally filtering, washing, drying, and optionally calcining to produce a ZSM-23 molecular sieve.

[0033] 8. The method according to any one of Solutions 1 to 7, characterized in that in step (1), the template agent is one or more of isopropylamine, pyrrolidine, N,N-dimethylformamide, and dimethylamine.

[0034] 9. The method according to any one of Solutions 1 to 8, characterized in that, in step (1), the molar ratio of silicon (as silica):aluminum (as alumina) in the mixed solution is 1:(0.10~0.85), preferably 1:(0.20~0.79), more preferably 1:(0.24~0.78); and the molar ratio of aluminum (as alumina):the template agent is 1:(10~100), preferably 1:(15~85), more preferably 1:(20~65).

[0035] 10. The method according to any one of Solutions 1 to 9, characterized in that in step (1), an amorphous silica-alumina precursor is prepared by a carbonization method, and then a template agent is added to the amorphous silica-alumina precursor to produce a mixed solution.

[0036] 11. The method for preparing the amorphous silica-alumina precursor in step (1) is The method according to any one of Solutions 1 to 10, comprising the steps of: preparing a solution of an aluminum source (such as an aluminate, preferably sodium aluminate) and a solution of a silicon-containing compound; mixing the aluminum source solution with a portion of the silicon-containing compound solution, introducing CO2 gas to cause gelation, and when the volume of introduced CO2 gas reaches 50-100%, preferably 70-90%, of the total volume of introduced CO2 gas, adding the remaining portion of the silicon-containing compound solution and optionally aging to produce an amorphous silica-alumina precursor.

[0037] 12. The method according to any one of Solutions 1 to 11, characterized in that the remaining portion of the solution of the silicon-containing compound as silica is 5 to 85% by weight, preferably 30 to 70% by weight, of the total amount of the solution of the silicon-containing compound as silica added.

[0038] 13. The method according to any one of Solutions 1 to 12, characterized in that the reaction temperature for the gelation is 10 to 40°C, preferably 15 to 35°C, and the pH after gelation is controlled to 9 to 12.

[0039] 14. The method according to any one of Solutions 1 to 13, characterized in that the solution of the silicon-containing compound is a water glass and / or sodium silicate solution.

[0040] 15. The method according to any one of Solutions 1 to 14, characterized in that the concentration of the aluminum source solution, based on the mass of Al2O3, is 15 to 60 g Al2O3 / L, the concentration of the silicon-containing compound solution, based on the mass of SiO2, is 40 to 260 g SiO2 / L, and the concentration of CO2 gas is 30 to 60 volume%.

[0041] 16. The method according to any one of Solutions 1 to 15, characterized in that the maturation time is 5 to 60 minutes, preferably 10 to 30 minutes; and the maturation temperature is 10 to 40°C, preferably 15 to 35°C.

[0042] 17. The method according to any one of Solutions 1 to 16, characterized in that in step (1), the mixed solution is stirred at 10 to 35°C for 0.2 to 1.5 hours, preferably at 10 to 25°C for 0.5 to 1 hour.

[0043] 18. The method according to any one of Solutions 1 to 17, characterized in that in step (2), an alkali source and a silicon source are added to step (1) based on the aluminum (as alumina) in the mixed solution of step (1), with a total molar ratio of SiO2:Al2O3:R2O (an alkali source, where R is an alkali metal such as sodium and potassium):H2O=1:(0.0025~0.025):(0.015~0.08):(30~80), and template agent (SDA) / SiO2=0.10~1.8, preferably with SiO2 / Al2O3 being 50~200, H2O / SiO2 being 30~60, and R2O / SiO2 being 0.025~0.06.

[0044] 19. The method according to any one of Solutions 1 to 18, characterized in that, in step (2), the silicon source is one or more of fumed silica, silica sol, and water glass, and the alkali source is one or more of sodium hydroxide, potassium hydroxide, and ammonia water.

[0045] 20. The method according to any one of Solutions 1 to 19, characterized in that in step (3), crystallization is carried out at 150 to 200°C for 8 to 72 hours, preferably at 160 to 180°C for 10 to 48 hours; drying is carried out at 60 to 130°C for 2 to 12 hours, preferably at 80 to 120°C for 4 to 8 hours; and firing is carried out at 500 to 600°C for 2 to 8 hours, preferably at 530 to 570°C for 3 to 6 hours or 4 to 6 hours.

[0046] Compared to the prior art, the present invention has the following advantages: According to the method for preparing ZSM-23 molecular sieves provided by the present invention, in the method for preparing an amorphous silica-alumina precursor, all the aluminum sources necessary for synthesis are added to promote the generation of primary structural units of the molecular sieve; when a template agent is added to the amorphous silica-alumina precursor, the template agent preferentially chelates with Al species and then adsorbs onto the surface of the formed primary structural units, achieving the preliminary assembly of the molecular sieve structure and generating numerous crystal nuclei; at the same time, the bonding sites of Al atoms can be better controlled, which is useful for subsequent crystallization to produce ZSM-23 with weaker acid sites and moderately strong acid sites. After adding an auxiliary silicon source to form the final gel, numerous crystal nuclei can rapidly grow into ZSM-23 molecular sieves with high crystallinity and small crystal size after static crystallization. Furthermore, the method of the present invention expands the silica-alumina ratio range for the synthesis of ZSM-23, shortens the crystallization time of the molecular sieve, reduces the amount of template agent used in the synthesis method of ZSM-23 molecular sieve, and produces molecular sieve products with superior performance. It is a green and viable industrial production route.

[0047] The ZSM-23 molecular sieve synthesized by the method of the present invention has a high degree of crystallinity, a smaller grain size, contains weaker and moderately strong acids, has a low strong acid content, and exhibits good thermal and hydrothermal stability, making it an excellent adsorbent or catalyst material.

[0048] [Brief explanation of the drawing] Figure 1 shows the XRD spectrum of the synthesized product of the present invention.

[0049] Figure 2 is a scanning electron microscope image of the synthesized product of the present invention.

[0050] [Detailed explanation] Analytical method according to the present invention: The specific surface area and pore volume of the molecular sieve are measured using the low-temperature liquid nitrogen physicoadsorption method with an ASAP 2405 physicoadscopy system manufactured by Micromeritics, Inc. (USA).

[0051] The silica-alumina molar ratio is determined by chemical analysis.

[0052] The XRD spectrum of the sample is obtained using a Dmax2500 X-ray diffractometer manufactured by Rigaku Corporation (Japan). The relative crystallinity of the molecular sieve is determined by X-ray powder diffraction (XRD). Specifically, the total height of the diffraction peaks indicated by 2θ degrees of approximately 11.3° and 19.5-23° in the XRD spectrum of a conventional ZSM-23 molecular sieve is taken as the 100% crystallinity, and the relative crystallinity is obtained by comparing it with other samples.

[0053] According to the present invention, the ZSM-23 molecular sieve has an XRD pattern that includes a characteristic diffraction peak indicated by 2θ degrees: approximately 11.3° ± 0.3° (e.g., ± 0.2° or ± 0.1°).

[0054] According to the present invention, the ZSM-23 molecular sieve has an XRD pattern that includes characteristic diffraction peaks indicated by 2θ degrees: 11.2~11.5°, 19.5~19.9°, 20.7~21.0°, and 22.8~23.1°.

[0055] Particle size was obtained using a JSM-7500F field emission scanning electron microscope from JEOL Corporation (Japan).

[0056] The acid distribution (including total acid content and strong acid content) was measured using NH3 thermal desorption (NH3-TPD), where the amount of acid with a desorption temperature of 350°C or higher was defined as the amount of strong acid.

[0057] In the present invention, the acid amount is calculated as H + .

[0058] In the present invention, wt% is the mass fraction, and vol% is the volume fraction.

[0059] To better illustrate the present invention, the present invention will be further described below in combination with examples and comparative examples. However, the scope of the present invention is not limited to the scope of these examples.

[0060] Example 1 A sodium aluminate working solution (40 g Al2O3 / L) was prepared. A sodium silicate solution with a SiO2 concentration of 28 wt% was diluted in a sodium silicate working solution (100 g SiO2 / L). 150 mL of the sodium aluminate working solution was placed in a gel formation tank. Then, 50 mL of the sodium silicate working solution was added. The reaction temperature was controlled at 20°C, and CO2 gas with a concentration of 50 vol% was introduced. When the pH reached 10.0, the introduction of CO2 was terminated. Then, 90 mL of the sodium silicate working solution was added, and then the remaining CO2 gas was introduced to stabilize it. The system was aged at 25°C for 30 minutes to produce an amorphous silica-alumina precursor. Based on the total charge molar ratio of SiO2:Al2O3:Na2O:H2O = 1:0.02:0.04:45 and IPA / SiO2 = 0.7 (IPA: isopropylamine as a template agent), isopropylamine was added to the obtained amorphous silica-alumina precursor. The obtained mixture was stirred at 15°C for 0.8 hours to produce a mixed solution containing an amorphous silica-alumina precursor and a template agent. Then, a mixture consisting of sodium hydroxide, silica sol, and water was added to the mixed solution. The obtained mixture was stirred to make it uniform to produce a silica-alumina gel.

[0061] The gel obtained above was poured into a stainless steel reaction vessel and statically crystallized at 160°C for 20 hours. After crystallization was complete, the crystallized system was filtered, washed to neutral, and dried at 120°C to obtain a molecular sieve product called ZSM-23-1. The obtained ZSM-23-1 was calcined in air at 550°C for 3 hours, the relative crystallinity after calcination was measured, and the hydrothermal stability was measured by hydrothermal treatment with steam at 600°C for 2 hours. The specific properties are shown in Table 1. Figure 1 shows the XRD spectrum of the molecular sieve, and Figure 2 shows the scanning electron microscope image of the molecular sieve, confirming that the obtained molecular sieve is the ZSM-23 molecular sieve.

[0062] Example 2 A sodium aluminate working solution (40 g Al2O3 / L) was prepared. A sodium silicate solution with a 28 wt% SiO2 concentration was diluted to a sodium silicate working solution (150 g SiO2 / L). 200 mL of the sodium aluminate working solution was placed in a gel-forming tank. Then, 40 mL of the sodium silicate working solution was added. The reaction temperature was controlled to 25°C, and 50 vol% CO2 gas was introduced. When the pH reached 10.5, the introduction of CO2 was stopped. Then, 40 mL of the sodium silicate working solution was added, followed by the introduction of the remaining CO2 to stabilize the system. The system was aged at 20°C for 20 minutes to produce an amorphous silica-alumina precursor. Based on a total molar ratio of SiO2:Al2O3:Na2O:H2O = 1:0.005:0.04:60 and IPA / SiO2 = 0.15, isopropylamine was added to the obtained amorphous silica-alumina precursor. The resulting mixture was stirred at 20°C for 1 hour to obtain a mixed solution containing an amorphous silica-alumina precursor and a template agent. Next, a mixture consisting of sodium hydroxide, silica sol, and water was added to the mixed solution. The resulting mixture was stirred to homogenize it to produce a silica-alumina gel.

[0063] The gel obtained above was poured into a stainless steel reaction vessel and statically crystallized at 180°C for 18 hours. After crystallization was complete, the crystallized system was filtered, washed to neutral, and dried at 120°C to obtain a molecular sieve product called ZSM-23-2. The obtained ZSM-23-2 was calcined in air at 550°C for 3 hours, the relative crystallinity after calcination was measured, and the hydrothermal stability was measured by hydrothermal treatment with steam at 600°C for 2 hours. Specific properties are shown in Table 1. The XRD spectrum was similar to that in Figure 1, and the scanning electron microscope image was similar to that in Figure 2.

[0064] Example 3 A sodium aluminate working solution (50 g Al2O3 / L) was prepared. A sodium silicate solution with a 28 wt% SiO2 concentration was diluted to a sodium silicate working solution (100 g SiO2 / L). 200 mL of the sodium aluminate working solution was placed in a gel-forming tank. Then, 60 mL of the sodium silicate working solution was added. The reaction temperature was controlled to 30°C, and 50 vol% CO2 gas was introduced. When the pH reached 10.0, the introduction of CO2 was stopped. Then, 40 mL of the sodium silicate working solution was added, followed by the introduction of the remaining CO2 gas to stabilize the system. The system was aged at 35°C for 15 minutes to produce an amorphous silica-alumina precursor. Based on a total molar ratio of SiO2:Al2O3:Na2O:H2O = 1:0.01:0.04:30 and IPA / SiO2 = 0.4, isopropylamine was added to the obtained amorphous silica-alumina precursor. The resulting mixture was stirred at 25°C for 0.5 hours to produce a mixed solution containing an amorphous silica-alumina precursor and a template agent. Next, a mixture consisting of sodium hydroxide, silica sol, and water was added to the mixed solution. The resulting mixture was stirred to homogenize it to produce a silica-alumina gel.

[0065] The obtained gel was poured into a stainless steel reaction vessel and statically crystallized at 160°C for 24 hours. After crystallization was complete, the crystallized system was filtered, washed to neutral, and dried at 120°C to obtain a molecular sieve product called ZSM-23-3. The obtained ZSM-23-3 was calcined in air at 550°C for 6 hours, the relative crystallinity after calcination was measured, and the hydrothermal stability was measured by hydrothermal treatment with steam at 600°C for 2 hours. The specific properties are shown in Table 1. The XRD spectrum was similar to that in Figure 1, and the scanning electron microscope image was similar to that in Figure 2.

[0066] Example 4 A sodium aluminate working solution (20 g Al2O3 / L) was prepared. A sodium silicate solution with a 28 wt% SiO2 concentration was diluted to a sodium silicate working solution (150 g SiO2 / L). 300 mL of the sodium aluminate working solution was placed in a gel-forming tank. Then, 20 mL of the sodium silicate working solution was added. The reaction temperature was controlled to 30°C, and 50 vol% CO2 gas was introduced. When the pH reached 11.0, the introduction of CO2 was stopped. Then, 20 mL of the sodium silicate working solution was added, followed by the introduction of the remaining CO2 gas to stabilize the system. The system was aged at 20°C for 30 minutes to produce an amorphous silica-alumina precursor. Based on the total molar ratio of SiO2:Al2O3:Na2O:H2O = 1:0.01:0.04:45 and IPA / SiO2 = 0.3, isopropylamine was added to the obtained amorphous silica-alumina precursor. The resulting mixture was stirred at 15°C for 1 hour to produce a mixed solution containing an amorphous silica-alumina precursor and a template agent. Next, a mixture consisting of sodium hydroxide, silica sol, and water was added to the mixed solution. The resulting mixture was stirred to homogenize it to produce a silica-alumina gel.

[0067] The gel obtained above was poured into a stainless steel reaction vessel and statically crystallized at 180°C for 24 hours. After crystallization was complete, the crystallized system was filtered, washed to neutral, and dried at 120°C to obtain a molecular sieve product called ZSM-23-4. The obtained ZSM-23-4 was calcined in air at 550°C for 4 hours, and the relative crystallinity after calcination was measured. Hydrothermal stability was measured by hydrothermal treatment with steam at 600°C for 2 hours. Specific properties are shown in Table 1. The XRD spectrum was similar to that in Figure 1, and the scanning electron microscope image was similar to that in Figure 2.

[0068] Example 5 A sodium aluminate working solution (40 g Al2O3 / L) was prepared. A sodium silicate solution with a 28 wt% SiO2 concentration was diluted to a sodium silicate working solution (50 g SiO2 / L). 150 mL of the sodium aluminate working solution was placed in a gel-forming tank. Then, 140 mL of the sodium silicate working solution was added. The reaction temperature was controlled to 25°C, and 50 vol% CO2 gas was introduced. When the pH reached 10.0, the introduction of CO2 was stopped. Then, 140 mL of the sodium silicate working solution was added, followed by the introduction of the remaining CO2 gas to stabilize the system. The system was aged at 25°C for 20 minutes to produce an amorphous silica-alumina precursor. Based on a total molar ratio of SiO2:Al2O3:Na2O:H2O = 1:0.01:0.04:45 and IPA / SiO2 = 0.4, isopropylamine was added to the obtained amorphous silica-alumina precursor. The resulting mixture was stirred at 15°C for 1 hour to produce a mixed solution containing an amorphous silica-alumina precursor and a template agent. Next, a mixture consisting of sodium hydroxide, fumed silica, and water was added to the mixed solution. The resulting mixture was stirred to homogenize it to obtain a silica-alumina gel.

[0069] The gel obtained above was poured into a stainless steel reaction vessel and statically crystallized at 180°C for 12 hours. After crystallization was complete, the crystallized system was filtered, washed to neutral, and dried at 120°C to obtain a molecular sieve product called ZSM-23-5. The obtained ZSM-23-5 was calcined in air at 550°C for 3 hours, the relative crystallinity after calcination was measured, and the hydrothermal stability was measured by hydrothermal treatment with steam at 600°C for 2 hours. Specific properties are shown in Table 1. The XRD spectrum was similar to that in Figure 1, and the scanning electron microscope image was similar to that in Figure 2.

[0070] Example 6 A sodium aluminate working solution (40 g Al2O3 / L) was prepared. A sodium silicate solution with a 28 wt% SiO2 concentration was diluted to a sodium silicate working solution (50 g SiO2 / L). 150 mL of the sodium aluminate working solution was placed in a gel-forming tank. Then, 140 mL of the sodium silicate working solution was added. The reaction temperature was controlled to 25°C, and 50 vol% CO2 gas was introduced. When the pH reached 10.0, the introduction of CO2 was stopped. Then, 140 mL of the sodium silicate working solution was added, followed by the introduction of the remaining CO2 gas to stabilize the system. The system was aged at 25°C for 20 minutes to produce an amorphous silica-alumina precursor. Based on a total molar ratio of SiO2:Al2O3:Na2O:H2O = 1:0.01:0.04:45 and SDA (structure-directing agent) / SiO2 = 0.1, pyrrolidine (SDA) was added to the obtained amorphous silica-alumina precursor. The resulting mixture was stirred at 15°C for 1 hour to produce a mixed solution containing the amorphous silica-alumina precursor and the template agent. Next, a mixture consisting of sodium hydroxide, fumed silica, and water was added to the mixed solution. The resulting mixture was stirred to homogenize it and a silica-alumina gel was produced.

[0071] The gel obtained above was poured into a stainless steel reaction vessel and statically crystallized at 180°C for 12 hours. After crystallization was complete, the crystallized system was filtered, washed to neutral, and dried at 120°C to obtain a molecular sieve product called ZSM-23-6. The obtained ZSM-23-6 was calcined in air at 550°C for 4 hours, the relative crystallinity after calcination was measured, and the hydrothermal stability was measured by hydrothermal treatment with steam at 600°C for 2 hours. Specific properties are shown in Table 1. The XRD spectrum was similar to that in Figure 1, and the scanning electron microscope image was similar to that in Figure 2.

[0072] Comparative Example 1 (See CN101214971A) An aluminum source, a silicon source, an alkali source, isopropylamine, and H2O were prepared and mixed based on the molar ratio of Al2O3 in the aluminum source, SiO2 in the silicon source, NaOH in the alkali source, isopropylamine, and H2O = 0.006:1:0.06:0.8:12 (the aluminum source was sodium aluminate, the silicon source was silica sol, and the alkali source was sodium hydroxide) to produce a reaction mixture. First, the aluminum source was added to an aqueous sodium hydroxide solution and the resulting mixture was uniformly stirred; then the silicon source was added and the resulting mixture was uniformly stirred; and then the isopropylamine was added and the resulting mixture was uniformly stirred to produce a reaction mixture. The resulting reaction mixture was transferred to a high-pressure reaction vessel and hydrothermally crystallized at 170°C for 3 days. Next, the obtained mixture was filtered, washed to neutral, and dried at 120°C to obtain a molecular sieve product called CNZSM-23-1; the obtained CNZSM-23-1 was calcined in air at 550°C for 3 hours, the relative crystallinity after calcination was measured, and its hydrothermal stability was measured by hydrothermal treatment with steam at 600°C for 2 hours. The specific properties are shown in Table 1.

[0073] Comparative Example 2 (See CN102992346A) 8.12 g of H2O and 0.092 g of aluminum sulfate were homogeneously mixed. 0.38 g of NaOH was added to the resulting mixture. Next, 3.32 g of silica sol with a silica content of 30.5% was added to the mixture while stirring. Stirring was continued until the solution was homogeneous. Then, 10% ZSM-23 molecular sieve was added as a crystal species (the amount of crystal species was calculated based on the mass percentage of SiO2 added). The reaction materials were added to a PTFE stainless steel reaction vessel and dynamically crystallized at 160°C for 10 hours. The resulting product was filtered by suction and dried to obtain the final product. The ratio of the reaction materials was SiO2:0.008319Al2O3:0.27Na2O:35H2O. The product was designated CNZSM-23-2. It was calcined in air at 550°C for 3 hours, and its relative crystallinity was measured after calcination. It was then hydrothermally treated with steam at 600°C for 2 hours, and its hydrothermal stability was measured. The specific properties are shown in Table 1.

[0074] Comparative Example 3 A sodium aluminate working solution (50 g Al2O3 / L) was prepared. A sodium silicate solution with a 28 wt% SiO2 concentration was diluted to a sodium silicate working solution (100 g SiO2 / L). 200 mL of the sodium aluminate working solution was placed in a gel-forming tank. Then, 60 mL of the sodium silicate working solution was added. The reaction temperature was controlled to 30°C, and 50 vol% CO2 gas was introduced. When the pH reached 10.0, the introduction of CO2 was stopped. Then, 40 mL of the sodium silicate working solution was added, followed by the introduction of the remaining CO2 gas to stabilize the system. The system was aged at 25°C for 30 minutes to obtain an amorphous silica-alumina precursor. Based on a total molar ratio of SiO2:Al2O3:Na2O:H2O = 1:0.01:0.04:30 and IPA / SiO2 = 0.4, a mixture consisting of sodium hydroxide, silica sol, isopropylamine, and water was added to the amorphous silica-alumina precursor obtained above. The resulting mixture was stirred to homogenize it and a silica-alumina gel was produced.

[0075] The gel obtained above was poured into a stainless steel reaction vessel and statically crystallized at 160°C for 24 hours. After crystallization was complete, the crystallized system was filtered, washed to neutral, and dried at 120°C to obtain a molecular sieve raw material powder called CZSM-23-3, and its relative crystallinity was measured. The obtained CZSM-23-3 was calcined in air at 550°C for 3 hours, and its relative crystallinity after calcination was measured. It was then hydrothermally treated with steam at 600°C for 2 hours to measure its hydrothermal stability. The specific properties are shown in Table 1.

[0076] Comparative Example 4 Solid aluminum sulfate was diluted in 60 mL of aluminum sulfate working solution (a) (having a concentration of 100 g Al2O3 / L). Concentrated aqueous ammonia was added to an appropriate amount of distilled water to dilute aqueous ammonia (b) to a concentration of approximately 10% by weight. A sodium silicate solution containing 28% by weight SiO2 was diluted in 140 mL of sodium silicate working solution (c) (having a concentration of 100 g SiO2 / L). 0.5 liters of distilled water was added to a 5 liter stainless steel reaction tank, stirred, and heated to 70°C. The valves of the containers containing (a), (b), and (c) were opened, and the flow rate of (a) was controlled to maintain a neutralization reaction time of 40 minutes. Then, the flow rate of (b) was quickly adjusted to maintain the pH of the system at 7-8, and the temperature of the system was controlled to approximately 60°C. After the reaction of aluminum sulfate was complete, the addition of (b) was stopped, and the formed silica-alumina sol was aged at 25°C for 40 minutes. Based on a total molar ratio of SiO2:Al2O3:Na2O:H2O = 1:0.02:0.04:45 and IPA / SiO2 = 0.7, isopropylamine was added to the amorphous silica-alumina precursor obtained above. The resulting mixture was stirred at 15°C for 0.8 hours to produce a mixed solution containing the amorphous silica-alumina precursor and a template agent. Next, a mixture consisting of sodium hydroxide, silica sol, and water was added to the mixed solution. The resulting mixture was stirred to homogenize it to produce a silica-alumina gel.

[0077] The gel obtained above was poured into a stainless steel reaction vessel and statically crystallized at 180°C for 36 hours. The crystallized system was then filtered, washed to neutral, and dried at 120°C to obtain a molecular sieve called CZSM-23-4, and its relative crystallinity was measured. The obtained CZSM-23-4 was calcined in air at 550°C for 3 hours, and its relative crystallinity after calcination was measured. It was then hydrothermally treated with steam at 600°C for 2 hours to measure its hydrothermal stability. The specific properties are shown in Table 1.

[0078] Comparative Example 5 (Preparation of conventional ZSM-23 molecular sieve) Water glass, aluminum sulfate, isopropylamine (IPA), sodium hydroxide, and water were mixed to produce 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. The resulting gel was heated at 180°C for 72 hours, filtered, washed, dried, and calcined. The relative crystallinity of the resulting product was measured, and its hydrothermal stability was measured after hydrothermal treatment with steam at 600°C for 2 hours.

[0079] [Table 1]

[0080] From the data in Table 1, it can be seen that the preparation method in the examples of the present invention can synthesize ZSM-23 molecular sieves with high crystallinity, a wider silica-alumina ratio range, relatively small crystal grains, relatively high content of weak and medium-strong acids, and good thermal and hydrothermal stability.

[0081] The performance of ZSM-23 molecular sieve samples was evaluated using a fixed-bed microreactor. Linear C 20 ~C 30 The reaction conditions and catalyst results for Comparative Example 1 and Example 3 in the hydrogenation isomerization reaction were as follows: Reaction materials: 90% by weight decahydronaphthalene, 10% by weight C 20 ~C 30 Straight-chain alkanes; Reaction conditions: Reaction temperature 280°C, liquid space velocity 1.0 h -1 Hydrogen-to-oil ratio: 600; Hydrogen reaction pressure: 4.0 MPa; Comparative Example 3 Liquid yield (C5 + ):93%;C 20 ~C 30 Degree of isomerization: 100%;C 20 ~C 30 Isomerization product yield: 42%;C 20 ~C 30 The ratio of the multi-branched component to the single-branched component in the isomerized product is 0.4.

[0082] Example 3 Liquid yield (C5 + ):96%;C 20 ~C 30 Degree of isomerization: 100%;C 20 ~C 30 Isomerization product yield: 58%;C 20 ~C 30 The ratio of the multi-branched component to the single-branched component in the isomerized product is 2.8. [Brief explanation of the drawing]

[0083] [Figure 1] Figure 1 shows the XRD spectrum of the synthesized product of the present invention. [Figure 2] Figure 2 is a scanning electron microscope image of the synthesized product of the present invention.

Claims

1. A ZSM-23 molecular sieve, wherein the total acid content of the ZSM-23 molecular sieve is 0.05 to 0.25 mmol / g; the strong acid content of the ZSM-23 molecular sieve is 5 to 33% of the total acid content; where the strong acid is NH ３ Temperature-induced desorption (NH ３ A ZSM-23 molecular sieve characterized by referring to an acid whose desorption temperature in TPD is 350°C or higher.

2. The ZSM-23 molecular sieve according to claim 1, characterized in that the total acid content of the ZSM-23 molecular sieve is 0.06 to 0.22 mmol / g; and the strong acid content of the ZSM-23 molecular sieve is 9 to 33% of the total acid content.

3. The ZSM-23 molecular sieve according to claim 1, characterized in that the total acid content of the ZSM-23 molecular sieve is 0.06 to 0.20 mmol / g; and the strong acid content of the ZSM-23 molecular sieve is 10 to 28% of the total acid content.

4. The molecular sieve according to any one of claims 1 to 3, characterized in that the particle size of the ZSM-23 molecular sieve is 100 to 700 nm.

5. The aforementioned ZSM-23 molecular sieve is SiO ２ / Al ２ O ３ The molar ratio is 35 to 300, and the specific surface area is 200 to 400 m². ２ The concentration is per gram, and the pore volume is 0.25 to 0.50 cm³. ３ A molecular sieve according to any one of claims 1 to 4, characterized in that it is / g.

6. The ZSM-23 molecular sieve has a SiO ２ / Al ２ O ３ molar ratio of 38 to 200, a specific surface area of 280 to 370 m ２ / g, and a pore volume of 0.28 to 0.40 cm ３ / g, and is characterized by the molecular sieve according to any one of claims 1 to 5.

7. The molecular sieve according to any one of claims 1 to 6, characterized in that the ZSM-23 molecular sieve has a relative crystallinity of 95 to 130% after firing, and a relative crystallinity of 93 to 120% after hydrothermal treatment with steam at 600°C for 2 hours.

8. The molecular sieve according to any one of claims 1 to 7, characterized in that the ZSM-23 molecular sieve has a relative crystallinity of 98 to 120% after firing, and a relative crystallinity of 95 to 115% after hydrothermal treatment with steam at 600°C for 2 hours.

9. A method for preparing a ZSM-23 molecular sieve according to any one of claims 1 to 8, characterized by comprising the following steps: (1) A step of preparing a mixed solution comprising a template agent and amorphous silica-alumina and / or amorphous silica-alumina precursor, wherein the amorphous silica-alumina and / or amorphous silica-alumina precursor is derived from an alkaline aluminum source (e.g., aluminates or metaaluminates such as sodium aluminate, potassium aluminate, sodium metaaluminate, and potassium metaaluminate); (2) A step of adding an alkali source and a silicon source to the mixed solution of step (1); (3) A step of crystallizing the substance obtained in step (2), filtering, washing, drying, and calcining to produce a ZSM-23 molecular sieve.

10. The method according to claim 9, characterized in that in step (1), the template agent is one or more of isopropylamine, pyrrolidine, N,N-dimethylformamide, and dimethylamine.

11. The method according to any one of claims 9 to 10, characterized in that, in step (1), the molar ratio of silicon (as silica):aluminum (as alumina) in the mixed solution is 1:(0.10 to 0.85); and the molar ratio of aluminum (as alumina):the template agent is 1:(10 to 100).

12. The method according to claim 11, characterized in that, in step (1), the molar ratio of silicon (as silica):aluminum (as alumina) in the mixed solution is 1:(0.24 to 0.78); and the molar ratio of aluminum (as alumina):the template agent is 1:(20 to 65).

13. In step (1), an amorphous silica-alumina precursor is prepared by carbonization, and then a template agent is added to the amorphous silica-alumina precursor to produce a mixed solution. The method for preparing the amorphous silica-alumina precursor in step (1) above is: A step of preparing a solution of an aluminum source and a solution of a silicon-containing compound, respectively; The aluminum source solution is mixed with a portion of the silicon-containing compound solution, and CO ２ By introducing a gas to induce gelation, the introduced CO ２ CO2, the volume of the gas, has been introduced. ２ When the total volume of the gas reaches 50-100%, the remaining portion of the silicon-containing compound solution is added and aged to produce an amorphous silica-alumina precursor. The method according to any one of claims 9 to 12, characterized by performing the following.

14. The method according to claim 13, characterized in that the remaining portion of the solution of the silicon-containing compound as silica contains 5 to 85% by weight of the total amount of the solution of the silicon-containing compound as silica added.

15. The method according to any one of claims 13 to 14, characterized in that the gelation reaction temperature is 10 to 40°C and the pH after gelation is controlled to 9 to 12.

16. The method according to any one of claims 13 to 15, characterized in that the solution of the silicon-containing compound is a water glass and / or sodium silicate solution.

17. Al ２ O ３ Based on the mass of the aluminum source, the concentration of the solution is 15 to 60 g Al ２ O ３ / L and SiO ２ Based on the mass of the silicon-containing compound, the concentration of the solution of the silicon-containing compound is 40 to 260 g SiO ２ / L, and the CO ２ The method according to any one of claims 13 to 16, characterized in that the gas concentration is 30 to 60 volume percent.

18. The method according to any one of claims 13 to 17, characterized in that the maturation time is 5 to 60 minutes; and the maturation temperature is 10 to 40°C.

19. The method according to any one of claims 9 to 18, characterized in that in step (1), the mixed solution is stirred at 10 to 35°C for 0.2 to 1.5 hours.

20. In step (2), Using the aluminum (as alumina) in the mixed solution of step (1) as a reference, SiO ２ : Al ２ O ３ : R ２ O (an alkali source, where R is an alkali metal such as sodium and potassium):H ２ O = 1: (0.0025 to 0.025): (0.015 to 0.08): (30 to 80), and template agent (SDA) / SiO ２ The method according to any one of claims 9 to 19, characterized in that an alkali source and a silicon source are added to step (1) based on a total molar ratio of 0.10 to 1.

8.

21. SiO ２ / Al ２ O ３ 50-200, H ２ O / SiO ２ 30-60, and R ２ O / SiO ２ The method according to claim 20, characterized in that the ratio is 0.025 to 0.

06.

22. The method according to any one of claims 9 to 21, characterized in that, in step (2), the silicon source is one or more of fumed silica, silica sol, and water glass, and the alkali source is one or more of sodium hydroxide, potassium hydroxide, and ammonia water.

23. The method according to any one of claims 9 to 22, characterized in that in step (3), crystallization is carried out at 150 to 200°C for 8 to 72 hours; drying is carried out at 60 to 130°C for 2 to 12 hours; and firing is carried out at 500 to 600°C for 2 to 8 hours.

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