A composite molecular sieve of HZSM-23@Al-SBA-15, its preparation method and application

Abstract

This invention discloses an HZSM-23@Al-SBA-15 composite molecular sieve, its preparation method, and its applications. The composite molecular sieve uses an HZSM-23 molecular sieve as the core and an Al-SBA-15 molecular sieve as the shell. The core crystallinity of the HZSM-23@Al-SBA-15 composite molecular sieve is 95-110%, preferably 97-108%. The preparation method of the composite molecular sieve includes the preparation of the HZSM-23 molecular sieve core. The HZSM-23@Al-SBA-15 composite molecular sieve synthesized by this method has high HZSM-23 core crystallinity and good hydrothermal stability.

Description

Technical Field

[0001] This invention relates to an HZSM-23@Al-SBA-15 composite molecular sieve, its preparation method, and its application; more specifically, it relates to an HZSM-23@Al-SBA-15 core-shell composite molecular sieve, its preparation method, and its application. Background Technology

[0002] ZSM-23 molecular sieve is a high silica-to-alumina ratio molecular sieve material with one-dimensional teardrop-shaped channels featuring a ten-membered ring structure. Due to its unique pore structure, ZSM-23 molecular sieve plays an irreplaceable role in separation, adsorption, and catalysis. However, conventionally prepared ZSM-23 molecular sieves have a high strong acid content, which can easily lead to hydrocracking as a side reaction during hydroisomerization. Therefore, to further expand its application range, it is essential to increase the weak acid content in ZSM-23 molecular sieves and introduce mesoporous or macroporous structures into microporous ZSM-23 molecular sieves.

[0003] In patent CN107235497, starch is added to regulate the synthesis pathway of ZSM-23 molecular sieve, which is then removed by calcination, thereby obtaining a ZSM-23 molecular sieve with a hierarchical mesoporous-microporous composite structure. This method is simple and low-cost, but because its mesoporous structure is obtained by removing the pore-expanding agent, it has low crystallinity and poor hydrothermal stability.

[0004] CN105540607 discloses a method for preparing multi-level porous composite molecular sieves ZSM-22 / ZSM-23. However, both ZSM-22 and ZSM-23 molecular sieves have microporous structures, so the mesoporous structures involved are mainly stacked pores, which have poor regularity and stability.

[0005] CN106513035 discloses a method for preparing a composite molecular sieve with ZSM-23 molecular sieve as the core and SBA-15 as the shell. However, since the SBA-15 shell is synthesized under strongly acidic conditions, it further affects the crystallinity of the ZSM-23 molecular sieve core, thus impacting its stability. Summary of the Invention

[0006] To address the shortcomings of existing technologies, this invention provides an HZSM-23@Al-SBA-15 composite molecular sieve, its preparation method, and its applications. The HZSM-23@Al-SBA-15 composite molecular sieve synthesized by this method exhibits high crystallinity of the HZSM-23 core and good hydrothermal stability.

[0007] The first aspect of the present invention is to provide an HZSM-23@Al-SBA-15 composite molecular sieve, wherein the composite molecular sieve has an HZSM-23 molecular sieve as the core and an Al-SBA-15 molecular sieve as the shell, the core crystallinity of the HZSM-23@Al-SBA-15 composite molecular sieve is 95~110%, preferably 97~108%, and the core crystallinity of the composite molecular sieve is 96~108%, preferably 98~105%, after being hydrothermally treated with steam at 600 °C for 2 hours.

[0008] The core-shell mass ratio of the composite molecular sieve of the present invention is 1:1 to 1:9, preferably 1:2 to 1:4; the total acid content of the composite molecular sieve is 0.07 to 0.35 mmol / g, preferably 0.09 to 0.32 mmol / g; the acid content below 350℃ is 60 to 95%, preferably 65 to 90%; and the Al-SBA-15 molecular sieve, based on the weight of the Al-SBA-15 molecular sieve, has an Al content of 2.45 to 10.05% by mass, preferably 2.83 to 8.50% by mass, calculated as alumina.

[0009] The specific surface area of ​​the composite molecular sieve described in this invention is 310~470 m². 2 / g, pore volume 0.31~0.68 cm³ 3 / g, preferably, the specific surface area of ​​the composite molecular sieve is 330~460 m² / g. 2 / g, pore volume 0.32~0.65 cm³ 3 / g.

[0010] The SiO2 / Al2O3 molar ratio of the composite molecular sieve of the present invention is 40~120, preferably 50~110.

[0011] A second aspect of the present invention is to provide a method for preparing HZSM-23@Al-SBA-15 composite molecular sieves, the method comprising the following steps:

[0012] (1) Preparation of nuclear molecular sieve HZSM-23 molecular sieve:

[0013] ① Prepare a mixture A containing a first template agent and amorphous silica-alumina and / or amorphous silica-alumina precursor;

[0014] ② Add an alkali source and a silicon source to the mixture from step ①;

[0015] ③ The material obtained in step ② is crystallized, washed, dried, calcined, and subjected to ammonium exchange to obtain HZSM-23 molecular sieve;

[0016] (2) Preparation of HZSM-23@Al-SBA-15 composite molecular sieve

[0017] ① After adding the silicon source to the acid solution and stirring for a period of time, let it stand and age to obtain the silicon source hydrolysate;

[0018] ② Mix the hydrolysate obtained in step (2)①, the HZSM-23 molecular sieve obtained in step (1)③, the second template agent, and aluminum isopropoxide evenly to obtain mixed slurry B. After crystallization, wash, dry, and calcinate to obtain HZSM-23@Al-SBA-15 composite molecular sieve.

[0019] In step (1)① of the above method, the first template agent is one or more of isopropylamine, pyrrolidine, N,N-dimethylformamide, and dimethylamine.

[0020] In step (1)① of the above method, the molar ratio of silicon (calculated as silicon oxide) to aluminum (calculated as aluminum oxide) in the mixture A is 1:(0.10-0.85), preferably 1:(0.20-0.79), and more preferably 1:(0.24-0.78); the molar ratio of aluminum (calculated as aluminum oxide) to template agent is 1:(10-100), preferably 1:(15-85), and more preferably 1:(20-65).

[0021] In step (1)① of the above method, an amorphous silicon-aluminum precursor is prepared by carbonization, and then a first template agent is added to the amorphous silicon-aluminum precursor to obtain the mixture.

[0022] In step (1)① of the above method, the mixture A is stirred at 10-35℃ for 0.2-2 hours.

[0023] In step (1)② of the above method, based on the aluminum (calculated as alumina) in the mixture A in step (1)①, the total feed molar ratio of SiO2:Al2O3:R2O (alkali source, where R is an alkali metal, such as sodium or potassium):H2O=1:(0.0025-0.025):(0.015-0.08):(30-80) and template agent (SDA) / SiO2=0.10-1.8 is preferably 50-200 for SiO2 / Al2O3, 30-60 for H2O / SiO2, and 0.025-0.06 for R2O / SiO2. The alkali source and silicon source are added to the material in step (1)①.

[0024] In step (1)② of the above method, 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.

[0025] In step (1)③ of the above method, the crystallization conditions are: crystallization at 150-200℃ for 8-72 hours; drying temperature at 80-120℃ for 4-8 hours; and calcination temperature at 530-570℃ for 3-6 hours.

[0026] In step (1)③ of the above method, ammonium exchange is carried out using conventional methods, such as one or more ammonium exchanges. The Na2O content in the ZSM-23 molecular sieve after ammonium exchange is less than 0.2%. After that, washing, drying and calcination can be carried out. The drying temperature is 80-120℃ and the time is 4-8 hours. The calcination temperature is 530-570℃ and the time is 3-6 hours.

[0027] In the preparation method of the nuclear molecular sieve HZSM-23 of the present invention, during the preparation of the amorphous silica-alumina precursor, all the aluminum sources required for synthesis are added, which promotes the generation of the 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 on the surface of the formed primary structural units, realizing the pre-assembly of the molecular sieve structure and generating a large number of crystal nuclei. At the same time, it can better control the binding sites of Al atoms, which helps to obtain a higher acid content below 350℃ during the later crystallization. When the silicon source is added to form the final gel, after static crystallization, a large number of crystal nuclei rapidly grow into a highly crystalline ZSM-23 molecular sieve.

[0028] In step (2)① of the above method, the silicon source is one or both of tetraethyl orthosilicate and methyl orthosilicate. The acid is one or more of hydrochloric acid, nitric acid, and sulfuric acid. The pH of the acid solution is 1.0~4.0.

[0029] In step (2)① of the above method, the stirring time is 4~10 hours and the temperature is 20~45℃; the standing aging time is 8~48 hours.

[0030] In step (2)② of the above method, the second template agent is a poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide) triblock copolymer (P123); preferably, aluminum isopropoxide and template agent P123 are first dissolved in an acid solution, and then mixed with other raw materials. The acid is one or more of hydrochloric acid, nitric acid, and sulfuric acid. The molar concentration of hydrogen ions in the acid solution is 0.1~0.7 mol / L, preferably 0.2~0.6 mol / L.

[0031] In step (2)② of the above method, the mass ratio of P123 to HZSM-23 is 0.15~0.55, preferably 0.18~0.50; the mass ratio of silicon source to HZSM-23 is 1~4, preferably 1.2~3; the mass ratio of deionized water to HZSM-23 is 18~50, preferably 20~40; and the molar ratio of SiO2 in the silicon source to Al2O3 in aluminum isopropoxide is 15~120, preferably 20~100.

[0032] In step (2)② of the above method, the mixture B needs to be continuously stirred at 15~30 ℃ for 6~8h before crystallization.

[0033] In step (2)② of the above method, the crystallization temperature of the mixture B is 80~120 ℃ and the crystallization time is 16~40 hours.

[0034] In step (2)② of the above method, the drying temperature is 80-120 ºC and the time is 4-8 hours; the calcination temperature is 530-570ºC and the time is 3-6 hours.

[0035] The aforementioned HZSM-23@Al-SBA-15 composite molecular sieve is suitable for hydroisomerization reactions using cycloalkane-rich feedstocks, wherein the cycloalkane content is 30-60%; the reaction temperature is 250-350 °C, and the liquid hourly space velocity is 0.5-1.5 h⁻¹. -1 The hydrogen-to-oil ratio is 600-1000, and the reaction hydrogen pressure is 3.5-5.0 MPa.

[0036] Compared with existing technologies, the HZSM-23@Al-SBA-15 composite molecular sieve, its preparation method, and its application have the following advantages:

[0037] (1) The inventors were surprised to find that the HZSM-23 molecular sieve prepared by the method of the present invention is the core of the composite molecular sieve. During the synthesis of shell Al-SBA-15 molecular sieve under strong acid conditions, the core of the synthesized HZSM-23@Al-SBA-15 composite molecular sieve still maintains a high degree of crystallinity, which greatly improves the hydrothermal stability of HZSM-23@Al-SBA-15 composite molecular sieve.

[0038] (2) The HZSM-23@Al-SBA-15 composite molecular sieve of the present invention has a high acid content below 350℃, which is conducive to the isomerization reaction of the primary pyrolysis products of Al-SBA-15 molecular sieve and effectively reduces secondary pyrolysis and carbon deposition. Attached Figure Description

[0039] Figure 1 This is the wide-angle XRD pattern of the product synthesized in Example 1 of the present invention, namely the XRD pattern of the nuclear HZSM-23 molecular sieve.

[0040] Figure 2 This is the small-angle XRD pattern of the product synthesized in Example 1 of the present invention, namely the XRD pattern of the shell Al-SBA-15 molecular sieve. Detailed Implementation

[0041] The specific preparation process of a non-limiting amorphous silicon-aluminum precursor in this embodiment of the invention is as follows: An aluminum source solution (preferably sodium aluminate) and a silicon-containing compound solution are prepared separately; the aluminum source solution is mixed with a portion of the silicon-containing compound solution, and CO2 gas is introduced to form a gel. When the volume of the introduced CO2 gas accounts for 50-100% of the total introduced volume, preferably 70-90%, the remaining portion of the silicon-containing compound solution is added, and the remaining CO2 gas is introduced. The amorphous silicon-aluminum precursor is then obtained after aging.

[0042] In the preparation process of the above-mentioned amorphous silicon-aluminum precursor, the remaining silicon-containing compound solution, calculated as silicon dioxide, accounts for 5-85 wt% of the total amount of silicon-containing compound solution added, calculated as silicon dioxide, preferably 30-70 wt%.

[0043] In the preparation process of the above-mentioned amorphous silicon-aluminum precursor, the gelation reaction temperature is 10-40℃, preferably 15-35℃, and the pH value after gelation is controlled to be 9-12.

[0044] In the preparation process of the above-mentioned amorphous silicon-aluminum precursor, the silicon-containing compound solution is water glass and / or sodium silicate solution.

[0045] In the above-mentioned preparation process of amorphous silicon-aluminum precursor, the concentration of the aluminum source solution is 15-60 gAl2O3 / L based on the mass of Al2O3, the concentration of the silicon-containing compound solution is 40-260 gSiO2 / L based on the mass of SiO2, and the concentration of the CO2 gas is 30-60 g.

[0046] In the preparation process of the above-mentioned amorphous silicon-aluminum precursor, the aging time is 5-60 minutes and the aging temperature is 10-40℃.

[0047] In this invention, the relative crystallinity is measured by XRD, and the crystallinity of the HZSM-23 molecular sieve prepared in step (1) of Example 1 is taken as the benchmark, which is 100%. In the XRD spectrum of the composite molecular sieve, the crystallinity is calculated based on the peaks of the HZSM-23 molecular sieve.

[0048] Specific surface area and pore volume were determined by cryogenic liquid nitrogen physical adsorption using an ASAP 2405 physical adsorption instrument from Micromeritics, Inc., USA.

[0049] The total acid content and the acid content below 350℃ were measured by NH3 temperature-programmed desorption (NH3-TPD), where the total acid content is the acid content corresponding to the desorption temperature of 120~500℃.

[0050] To better illustrate the present invention, further explanation is provided below with reference to embodiments and comparative examples. However, the scope of the present invention is not limited to these embodiments, and unless otherwise specified, all percentages in the following embodiments and comparative examples refer to mass percentages.

[0051] Example 1

[0052] (1) Preparation of nuclear molecular sieve HZSM-23

[0053] A working solution of sodium aluminate with a concentration of 40 g Al2O3 / L was prepared. A sodium silicate solution containing 28 wt% SiO2 was taken and diluted to a working solution of sodium silicate with a concentration of 100 g SiO2 / L. 150 mL of the sodium aluminate working solution was placed in a gelation tank, and then 50 mL of sodium silicate working solution was added. The reaction temperature was controlled at 20ºC, and CO2 gas with a concentration of 50 wt% was introduced. When the pH reached 10.0, the CO2 introduction was stopped, and then 90 mL of sodium silicate working solution was added. The remaining CO2 gas was then introduced for stabilization. After aging at 25 ℃ for 30 minutes, an amorphous silica-alumina precursor was obtained. Isopropylamine was added to the amorphous silica-alumina precursor obtained above at a total molar ratio of SiO2:Al2O3:Na2O:H2O=1:0.02:0.04:45 and IPA / SiO2=0.7 (IPA being the template agent isopropylamine). After stirring at 15 °C for 0.8 hours, a mixed solution containing the amorphous silica-alumina precursor and the template agent was obtained. Then, a mixture of sodium hydroxide, silica sol, and water was added and stirred until homogeneous to obtain a silica-alumina gel. The obtained gel was poured into a stainless steel reactor and statically crystallized at 160 °C for 20 hours. After crystallization, the gel was filtered, washed until neutral, and dried at 120 °C to obtain the molecular sieve product NaZSM-23-1. A certain amount of NaZSM-23-1 molecular sieve sample was weighed and placed in a 2 mol / L ammonium nitrate solution with a liquid-to-solid ratio of 10. After stirring continuously in a water bath at 80-90 ℃ for 1 hour, the sample was filtered and washed. The above operation was repeated twice. The sample was then dried in an oven at 80-100 ℃ for 8 hours and calcined in air at 550 ℃ for 3 hours to obtain HZSM-23-1. Its relative crystallinity was measured. After hydrothermal treatment with steam at 600 ℃ for 2 hours, its hydrothermal stability was measured. The specific properties are shown in Table 1.

[0054] (2) Preparation of HZSM-23@Al-SBA-15 composite molecular sieve

[0055] ① Add 15.0 g of tetraethyl orthosilicate to 50.0 g of HCl solution with pH=2.0, stir at 40℃ for 4 hours, and let stand for 36 hours to obtain silicon source hydrolysate.

[0056] ② 3.0g P123 was dissolved in 250mL of 0.30mol / L hydrochloric acid solution; 2.55g aluminum isopropoxide, 10g HZSM-23-1, and the silicon source hydrolysate obtained in step (2) ① were added successively and stirred at room temperature for 4 hours; the resulting mixture was transferred to a hydrothermal reactor and crystallized at 100℃ for 24 hours. After filtration and washing until neutral, it was dried at 100℃ to obtain molecular sieve product Z-1. The specific properties are shown in Table 1. Figure 1 The image shows the wide-angle XRD pattern of a core-shell composite molecular sieve. Figure 2 This is the small-angle XRD pattern of a core-shell composite molecular sieve.

[0057] Example 2

[0058] (1) Preparation of nuclear molecular sieve HZSM-23

[0059] A working solution of sodium aluminate with a concentration of 40 g Al2O3 / L was prepared. A sodium silicate solution containing 28 wt% SiO2 was taken and diluted to a working solution of sodium silicate with a concentration of 150 g SiO2 / L. 200 mL of the sodium aluminate working solution was placed in a gelation tank, and then 40 mL of sodium silicate working solution was added. The reaction temperature was controlled at 25°C, and CO2 gas with a concentration of 50 wt% was introduced. When the pH value reached 10.5, the CO2 introduction was stopped, and another 40 mL of sodium silicate working solution was added. The remaining CO2 gas was then introduced for stabilization. After aging at 20°C for 20 minutes, an amorphous silica-alumina precursor was obtained. Isopropylamine was added to the amorphous silica-alumina precursor obtained above at a total molar ratio of SiO2:Al2O3:Na2O:H2O=1:0.005:0.04:60 and IPA / SiO2=0.15. After stirring at 20°C for 1 hour, a mixed solution containing the amorphous silica-alumina precursor and template agent was obtained. Then, a mixture of sodium hydroxide, silica sol, and water was added to the solution and stirred until homogeneous to obtain silica-alumina gel. The obtained gel was poured into a stainless steel reactor and statically crystallized at 180°C for 18 hours. After crystallization, the solution was filtered, washed until neutral, and dried at 120°C to obtain the molecular sieve product NaZSM-23-2. A certain amount of NaZSM-23-2 molecular sieve sample was weighed and placed in a 2 mol / L ammonium nitrate solution with a liquid-to-solid ratio of 10. The solution was stirred continuously in a water bath at 80-90°C for 1 hour, then filtered and washed. After repeating the above operation process twice, the sample was dried in an oven at 80~100 ℃ for 8 hours and calcined in air at 550 ℃ for 3 hours to obtain HZSM-23-2, and its relative crystallinity was measured. After hydrothermal treatment with water vapor at 600 ℃ for 2 hours, its hydrothermal stability was measured. The specific properties are shown in Table 1.

[0060] (2) Preparation of HZSM-23@Al-SBA-15 composite molecular sieve

[0061] ① Add 15.0 g of tetraethyl orthosilicate to 50.0 g of HCl solution with pH=2.0, stir at 20℃ for 10 hours, and let stand for 24 hours to obtain silicon source hydrolysate.

[0062] ② 3.5 g P123 was dissolved in 250 mL of 0.40 mol / L hydrochloric acid solution; 2.55 g aluminum isopropoxide, 17 g HZSM-23-2, and the silicon source hydrolysate obtained in step (2) ① were added successively and stirred at room temperature for 4 hours; the resulting mixture was transferred to a hydrothermal reactor and crystallized at 100℃ for 24 hours. After filtration and washing until neutral, it was dried at 100℃ to obtain molecular sieve product Z-2. Its specific properties are shown in Table 1. Its wide-angle XRD spectrum is similar to Figure 1 Similarly, small-angle XRD patterns and Figure 2 similar.

[0063] Example 3

[0064] (1) Preparation of nuclear molecular sieve HZSM-23

[0065] A working solution of sodium aluminate with a concentration of 50 g Al2O3 / L was prepared. A sodium silicate solution containing 28 wt% SiO2 was taken and diluted to a working solution of sodium silicate with a concentration of 100 g SiO2 / L. 200 mL of the sodium aluminate working solution was placed in a gelation tank, and then 60 mL of sodium silicate working solution was added. The reaction temperature was controlled at 30℃, and CO2 gas with a concentration of 50 wt% was introduced. When the pH reached 10.0, the CO2 introduction was stopped, and then 40 mL of sodium silicate working solution was added. The remaining CO2 gas was then introduced for stabilization. After aging at 35℃ for 15 minutes, an amorphous silica-alumina precursor was obtained. Isopropylamine was added to the amorphous silica-alumina precursor obtained above at a total molar ratio of SiO2:Al2O3:Na2O:H2O=1:0.01:0.04:30 and IPA / SiO2=0.4. After stirring at 25ºC for 0.5 hours, a mixed solution containing the amorphous silica-alumina precursor and template agent was obtained. Then, a mixture of sodium hydroxide, silica sol, and water was added to the solution and stirred until homogeneous to obtain silica-alumina gel. The obtained gel was poured into a stainless steel reactor and statically crystallized at 180℃ for 18 hours. After crystallization, the solution was filtered, washed until neutral, and dried at 120℃ to obtain the molecular sieve product NaZSM-23-3. A certain amount of NaZSM-23-3 molecular sieve sample was weighed and placed in a 2 mol / L ammonium nitrate solution with a liquid-to-solid ratio of 10. After stirring continuously in a water bath at 80~90℃ for 1 hour, the solution was filtered and washed. After repeating the above operation process twice, the sample was dried in an oven at 80~100 ℃ for 8 hours and calcined in air at 550 ℃ for 3 hours to obtain HZSM-23-3, and its relative crystallinity was measured. After hydrothermal treatment with water vapor at 600 ℃ for 2 hours, its hydrothermal stability was measured. The specific properties are shown in Table 1.

[0066] (2) Preparation of HZSM-23@Al-SBA-15 composite molecular sieve

[0067] ① Add 15.0 g of tetraethyl orthosilicate to 50.0 g of HCl solution with pH=3.0, stir at 30℃ for 8 hours, and let stand for 36 hours to obtain silicon source hydrolysate.

[0068] ② 3.93 g P123 was dissolved in 250 mL of 0.50 mol / L hydrochloric acid solution; 3.41 g aluminum isopropoxide, 10 g HZSM-23-3, and the silicon source hydrolysate obtained in step (2) ① were added successively and stirred at room temperature for 4 hours; the resulting mixture was transferred to a hydrothermal reactor and crystallized at 100℃ for 24 hours. After filtration and washing until neutral, it was dried at 100℃ to obtain molecular sieve product Z-3. Its specific properties are shown in Table 1. Its wide-angle XRD spectrum is similar to Figure 1 Similarly, small-angle XRD patterns and Figure 2 similar.

[0069] Example 4

[0070] (1) Preparation of nuclear molecular sieve HZSM-23

[0071] A working solution of sodium aluminate with a concentration of 20 g Al2O3 / L was prepared. A sodium silicate solution containing 28 wt% SiO2 was taken and diluted to a working solution of sodium silicate with a concentration of 150 g SiO2 / L. 300 mL of the sodium aluminate working solution was placed in a gelation tank, and then 20 mL of sodium silicate working solution was added. The reaction temperature was controlled at 30ºC, and CO2 gas with a concentration of 50 wt% was introduced. When the pH reached 11.0, the CO2 introduction was stopped, and another 20 mL of sodium silicate working solution was added. The remaining CO2 gas was then introduced for stabilization. After aging at 20 ℃ for 30 minutes, an amorphous silica-alumina precursor was obtained. Isopropylamine was added to the amorphous silica-alumina precursor obtained above at a total molar ratio of SiO2:Al2O3:Na2O:H2O=1:0.01:0.04:45 and IPA / SiO2=0.3. After stirring at 15 °C for 1 hour, a mixed solution containing the amorphous silica-alumina precursor and template agent was obtained. Then, a mixture of sodium hydroxide, silica sol, and water was added to the solution and stirred until homogeneous to obtain silica-alumina gel. The obtained gel was poured into a stainless steel reactor and statically crystallized at 180 °C for 18 hours. After crystallization, the solution was filtered, washed until neutral, and dried at 120 °C to obtain the molecular sieve product NaZSM-23-4. A certain amount of NaZSM-23-4 molecular sieve sample was weighed and placed in a 2 mol / L ammonium nitrate solution with a liquid-to-solid ratio of 10. After stirring continuously in a water bath at 80-90 °C for 1 hour, the solution was filtered and washed. After repeating the above operation process twice, the sample was dried in an oven at 80~100 ℃ for 8 hours and calcined in air at 550 ℃ for 3 hours to obtain HZSM-23-4, and its relative crystallinity was measured. After hydrothermal treatment with water vapor at 600 ℃ for 2 hours, its hydrothermal stability was measured. The specific properties are shown in Table 1.

[0072] (2) Preparation of HZSM-23@Al-SBA-15 composite molecular sieve

[0073] ① Add 15.0 g of tetraethyl orthosilicate to 80.0 g of HCl solution with pH=1.0, stir at 35℃ for 6 hours, and let stand for 24 hours to obtain silicon source hydrolysate.

[0074] ② 3.0 g P123 was dissolved in 200 mL of 0.50 mol / L hydrochloric acid solution; 1.75 g aluminum isopropoxide, 10 g HZSM-23-3, and the silicon source hydrolysate obtained in step (2) ① were added successively and stirred at room temperature for 4 hours; the resulting mixture was transferred to a hydrothermal reactor and crystallized at 100 ℃ for 24 hours. After filtration and washing until neutral, it was dried at 100 ℃ to obtain molecular sieve product Z-4. Its specific properties are shown in Table 1; its wide-angle XRD spectrum is similar to Figure 1 Similarly, small-angle XRD patterns and Figure 2 similar.

[0075] Example 5

[0076] (1) Preparation of nuclear molecular sieve HZSM-23

[0077] A working solution of sodium aluminate with a concentration of 40 g Al2O3 / L was prepared. A sodium silicate solution containing 28 wt% SiO2 was taken and diluted to a working solution of sodium silicate with a concentration of 50 g SiO2 / L. 150 mL of the sodium aluminate working solution was placed in a gelation vessel, and then 140 mL of sodium silicate working solution was added. The reaction temperature was controlled at 25 ℃, and CO2 gas with a concentration of 50 wt% was introduced. When the pH reached 10.0, the CO2 introduction was stopped, and another 140 mL of sodium silicate working solution was added. The remaining CO2 gas was then introduced for stabilization. After aging at 25 ℃ for 20 minutes, an amorphous silica-alumina precursor was obtained. Isopropylamine was added to the amorphous silica-alumina precursor obtained above at a total molar ratio of SiO2:Al2O3:Na2O:H2O=1:0.01:0.04:45 and IPA / SiO2=0.4. After stirring at 15 °C for 1 hour, a mixed solution containing the amorphous silica-alumina precursor and template agent was obtained. Then, a mixture of sodium hydroxide, fumed silica, and water was added to the solution and stirred until homogeneous to obtain silica-alumina gel. The obtained gel was poured into a stainless steel reactor and statically crystallized at 180 °C for 18 hours. After crystallization, the solution was filtered, washed until neutral, and dried at 120 °C to obtain the molecular sieve product NaZSM-23-5. A certain amount of NaZSM-23-5 molecular sieve sample was weighed and placed in a 2 mol / L ammonium nitrate solution with a liquid-to-solid ratio of 10. After stirring continuously in a water bath at 80-90 °C for 1 hour, the solution was filtered and washed. After repeating the above operation process twice, the sample was dried in an oven at 80~100 ℃ for 8 hours and calcined in air at 550 ℃ for 3 hours to obtain HZSM-23-5, and its relative crystallinity was measured. After hydrothermal treatment with water vapor at 600 ℃ for 2 hours, its hydrothermal stability was measured. The specific properties are shown in Table 1.

[0078] (2) Preparation of HZSM-23@Al-SBA-15 composite molecular sieve

[0079] ① Add 23.31 g of tetraethyl orthosilicate to 100.0 g of HCl solution with pH=2.0, stir at 40℃ for 4 hours, and let stand for 24 hours to obtain silicon source hydrolysate.

[0080] ②4.2 g P123 was dissolved in 300 mL of 0.30 mol / L hydrochloric acid solution; 0.92 g aluminum isopropoxide, 10 g HZSM-23-3, and the silicon source hydrolysate obtained in step (2) ① were added successively and stirred at room temperature for 6 hours; the resulting mixture was transferred to a hydrothermal reactor and crystallized at 100 ℃ for 24 hours. After filtration and washing until neutral, it was dried at 100 ℃ to obtain molecular sieve product Z-5. Its specific properties are shown in Table 1; its wide-angle XRD spectrum is similar to Figure 1 Similarly, small-angle XRD patterns and Figure 2 similar.

[0081] Comparative Example 1: (Refer to CN106513035A)

[0082] 1.38 g of Al₂SO₄ and 1.36 g of NaOH were dissolved in 12.8 g of deionized water, and then 7.28 g of pyrrolidine was added and stirred thoroughly. 48.29 g of silica sol (40 wt% SiO₂) was added and stirred until a gel was formed. The molar ratio of the additives was SiO₂:0.0125Al₂O₃:0.05Na₂O:0.32pyrrolidine:10H₂O. The formed gel was transferred to a high-pressure reactor and heated and stirred. After crystallization at 180 °C for 72 hours, it was washed, filtered, and dried at 120 °C to obtain the molecular sieve product DNa-ZSM-23-1. A certain amount of DNa-ZSM-23-1 molecular sieve sample was weighed and placed in a 2 mol / L ammonium nitrate solution with a liquid-to-solid ratio of 10. After stirring continuously in a water bath at 80-90 °C for 1 hour, it was filtered and washed. After repeating the above operation process twice, the sample was dried in an oven at 80~100 ℃ for 8 hours and calcined in air at 550 ℃ for 3 hours to obtain DHZSM-23-1, and its relative crystallinity was measured. After hydrothermal treatment with water vapor at 600 ℃ for 2 hours, its hydrothermal stability was measured. The specific properties are shown in Table 1.

[0083] 6 g of P123 was dissolved in 144 g of deionized water. Then, 6.24 g of silica sol (40 wt% SiO2), 0.31 g of aluminum sulfate, and 10 g of DHZSM-23-1 molecular sieve powder were added sequentially. After mixing evenly, a certain amount of HCl was added to adjust the pH of the solution to 2-4. After stirring for 2 hours, the resulting slurry was transferred to a hydrothermal reactor and crystallized at 100 °C for 24 hours. The reaction product was filtered, washed until neutral, and dried at 100 °C to obtain molecular sieve product DZ-1. The specific properties are shown in Table 1.

[0084] Comparative Example 2:

[0085] (Preparation of nuclear ZSM-23 molecular sieve according to CN102992346A)

[0086] 0.092 g of aluminum sulfate was dissolved in 8.12 g of H2O, and then 0.38 g of NaOH was added. After dissolving, 2.53 g of silica sol (40 wt% SiO2) was added, and stirring was continued until the solution became homogeneous. Then, 10% ZSM-23 molecular sieve was added as seed crystals (the amount of seed crystals was calculated as a percentage of the mass of SiO2 added). The reaction raw materials (the ratio was SiO2:0.008319Al2O3:0.27Na2O:35H2O) were transferred to a hydrothermal reactor and dynamically crystallized at 160 ℃ for 10 hours. After filtering and drying, the product was obtained as molecular sieve product DNa-ZSM-23-2. A certain amount of DNa-ZSM-23-2 molecular sieve sample was weighed and placed in a 2 mol / L ammonium nitrate solution with a liquid-to-solid ratio of 10. After stirring continuously in a water bath at 80~90 ℃ for 1 hour, the sample was filtered and washed. After repeating the above operation process twice, the sample was dried in an oven at 80~100 ℃ for 8 hours and calcined in air at 550 ℃ for 3 hours to obtain DHZSM-23-2, and its relative crystallinity was measured. After hydrothermal treatment with water vapor at 600 ℃ for 2 hours, its hydrothermal stability was measured. The specific properties are shown in Table 1.

[0087] 15.0 g of tetraethyl orthosilicate was added to 50.0 g of HCl solution with pH=2.0. After stirring at room temperature for 4 hours, the solution was allowed to stand for 36 hours to obtain the silicon source hydrolysate.

[0088] 3.0 g P123 was dissolved in 250 mL of 0.30 mol / L hydrochloric acid solution; 2.55 g aluminum isopropoxide, 10 g DHZSM-23-3, and the silicon source hydrolysate obtained in step (2) ① were added successively and stirred at room temperature for 4 hours; the resulting mixture was transferred to a hydrothermal reactor and crystallized at 100 ℃ for 24 hours. After filtration and washing until neutral, it was dried at 100 ℃ to obtain molecular sieve product DZ-3. The specific properties are shown in Table 1.

[0089] Comparative Example 3:

[0090] A gel with a total molar ratio of SiO2 from silicon source: Al2O3 from aluminum source: NaOH: IPA: H2O = 1:0.01:0.08:1.0:50 was prepared by mixing water glass, aluminum sulfate, isopropylamine (IPA), sodium hydroxide, and water. After heating at 180 °C for 72 hours, the gel was washed, filtered, and dried at 120 °C to obtain the molecular sieve product DNa-ZSM-23-2. A certain amount of DNa-ZSM-23-2 molecular sieve sample was weighed and placed in a 2 mol / L ammonium nitrate solution with a liquid-to-solid ratio of 10. The solution was stirred continuously in a water bath at 80-90 °C for 1 hour, then filtered and washed. After repeating the above operation process twice, the sample was dried in an oven at 80~100 ℃ for 8 hours and calcined in air at 550 ℃ for 3 hours to obtain DHZSM-23-3, and its relative crystallinity was measured. After hydrothermal treatment with water vapor at 600 ℃ for 2 hours, its hydrothermal stability was measured. The specific properties are shown in Table 1.

[0091] 15.0 g of tetraethyl orthosilicate was added to 50.0 g of HCl solution with pH=2.0. After stirring at room temperature for 4 hours, the solution was allowed to stand for 36 hours to obtain the silicon source hydrolysate.

[0092] 3.0 g P123 was dissolved in 250 mL of 0.30 mol / L hydrochloric acid solution; 2.55 g aluminum isopropoxide, 10 g DHZSM-23-3, and the silicon source hydrolysate obtained in step (2) ① were added successively and stirred at room temperature for 4 hours; the resulting mixture was transferred to a hydrothermal reactor and crystallized at 100 ℃ for 24 hours. After filtration and washing until neutral, it was dried at 100 ℃ to obtain molecular sieve product DZ-3. The specific properties are shown in Table 1.

[0093] The performance of ZSM-23 molecular sieve samples was evaluated in a fixed-bed microreactor. The hydrogenation of ethylcyclohexane was used as a model reaction, with reactants consisting of 90 wt% decahydronaphthalene and 10 wt% ethylcyclohexane. The reaction temperature was 300 °C and the liquid hourly space velocity (LHSV) was 1.0 h⁻¹. -1 The hydrogen-to-oil ratio was 800, and the reaction hydrogen pressure was 4.0 MPa. Catalysts were prepared by loading noble metal Pt onto samples from Comparative Example 1, Comparative Example 2, and Examples 1 and 5, respectively. The catalytic results are as follows:

[0094] Example 1:

[0095] Ethylcyclohexane conversion: 91%; C8H 18 Yield: 74%; C8H 18 Isomerization degree: 98%; C8H 18 The ratio of multi-branched to single-branched components in the isomerized product is 2.2.

[0096] Example 5:

[0097] Ethylcyclohexane conversion: 92%; C8H 18 Yield: 72%; C8H 18 Isomerization degree: 97%; C8H 18 The ratio of multi-branched to single-branched components in the isomerized product is 2.4.

[0098] Comparative Example 1:

[0099] Ethylcyclohexane conversion: 81%; C8H 18 Yield: 51%; C8H 18 Isomerization degree: 66%; C8H 18 The ratio of multi-branched to single-branched components in the isomerized product is 0.7.

[0100] Comparative Example 2:

[0101] Ethylcyclohexane conversion: 78%; C8H 18 Yield: 46%; C8H 18 Isomerization degree: 71%; C8H 18 The ratio of multi-branched to single-branched components in the isomerized product is 1.0.

[0102] Table 1

[0103]

Claims

1. An HZSM-23@Al-SBA-15 composite molecular sieve, characterized in that: The composite molecular sieve uses HZSM-23 molecular sieve as the core and Al-SBA-15 molecular sieve as the shell. The core crystallinity of the HZSM-23@Al-SBA-15 composite molecular sieve is 95~110%, and after hydrothermal treatment with steam at 600℃ for 2 hours, the core crystallinity of the composite molecular sieve is 96~108%. The preparation method of the composite molecular sieve includes the following steps: (1) Preparation of nuclear molecular sieve HZSM-23 molecular sieve: ① Prepare a mixture A containing a first template agent and amorphous silica-alumina and / or amorphous silica-alumina precursor; ② Add an alkali source and a silicon source to the mixture from step ①; ③ The material obtained in step ② is crystallized, washed, dried, calcined, and subjected to ammonium exchange to obtain HZSM-23 molecular sieve; (2) Preparation of HZSM-23@Al-SBA-15 composite molecular sieve ① After adding the silicon source to the acid solution and stirring for a period of time, let it stand and age to obtain the silicon source hydrolysate; ② Mix the hydrolysate obtained in step (2)①, the HZSM-23 molecular sieve obtained in step (1)③, the second template agent, and aluminum isopropoxide evenly to obtain mixed slurry B. After crystallization, wash, dry, and calcinate to obtain HZSM-23@Al-SBA-15 composite molecular sieve.

2. The molecular sieve according to claim 1, characterized in that: The HZSM-23@Al-SBA-15 composite molecular sieve has a nucleus crystallinity of 97~108%, and after being hydrothermally treated with steam at 600℃ for 2 hours, the nucleus crystallinity of the composite molecular sieve is 98~105%.

3. The molecular sieve according to claim 1, characterized in that: The core-shell mass ratio of the composite molecular sieve is 1:1 to 1:9; the total acid content of the composite molecular sieve is 0.07 to 0.35 mmol / g; the acid content below 350℃ is 60 to 95%; and the Al-SBA-15 molecular sieve, based on the weight of Al-SBA-15 molecular sieve, has an Al content of 2.45 to 10.05% by mass, calculated as alumina.

4. The molecular sieve according to claim 3, characterized in that: The core-shell mass ratio of the composite molecular sieve is 1:2 to 1:4; the total acid content of the composite molecular sieve is 0.09 to 0.32 mmol / g; the acid content below 350℃ is 65 to 90%; and the Al-SBA-15 molecular sieve, based on the weight of Al-SBA-15 molecular sieve, has an Al content of 2.83 to 8.50% by mass, calculated as alumina.

5. The molecular sieve according to claim 1, characterized in that: The specific surface area of ​​the composite molecular sieve is 310~470 m². 2 / g, pore volume is 0.31~0.68cm³ 3 / g.

6. The molecular sieve according to claim 5, characterized in that: The specific surface area of ​​the composite molecular sieve is 330~460m². 2 / g, pore volume 0.32~0.65cm³ 3 / g.

7. The molecular sieve according to claim 1, characterized in that: The SiO2 / Al2O3 molar ratio of the composite molecular sieve is 40~120.

8. The molecular sieve according to claim 7, characterized in that: The SiO2 / Al2O3 molar ratio of the composite molecular sieve is 50~110.

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

10. The molecular sieve according to claim 1, characterized in that: In step (1)①, the silicon in the mixture A is calculated as silicon oxide and the aluminum is calculated as aluminum oxide, with a silicon-aluminum molar ratio of 1:0.10-0.85; the aluminum is calculated as aluminum oxide, with an aluminum-template molar ratio of 1:10-100.

11. The molecular sieve according to claim 10, characterized in that: In step (1)①, the silicon in the mixture A is calculated as silicon oxide and the aluminum is calculated as aluminum oxide, with a silicon-aluminum molar ratio of 1:0.20-0.79; the aluminum is calculated as aluminum oxide, with an aluminum-template molar ratio of 1:15-85.

12. The molecular sieve according to claim 11, characterized in that: In step (1)①, the silicon in the mixture A is calculated as silicon oxide and the aluminum is calculated as aluminum oxide, with a silicon-aluminum molar ratio of 1:0.24-0.78; the aluminum is calculated as aluminum oxide, with an aluminum-template molar ratio of 1:20-65.

13. The molecular sieve according to claim 1, characterized in that: In step (1)①, an amorphous silicon-aluminum precursor is prepared by carbonization, and then a first template agent is added to the amorphous silicon-aluminum precursor to obtain the mixture.

14. The molecular sieve according to claim 1, characterized in that: In step (1)①, the mixture A is stirred at 10-35℃ for 0.2-2 hours.

15. The molecular sieve according to claim 1, characterized in that: In step (1)②, based on the aluminum in the mixture A in step (1)① (calculated as alumina), an alkali source and a supplementary silicon source are added to the material in step (1)① according to the total feed molar ratio of SiO2:Al2O3:R2O alkali source:H2O=1:0.0025-0.025:0.015-0.08:30-80 and template agent SDA / SiO2=0.10-1.8, where R is an alkali metal.

16. The molecular sieve according to claim 15, characterized in that: In step (1)②, SiO2 / Al2O3 is 50-200, H2O / SiO2 is 30-60, R2O / SiO2 is 0.025-0.06; and / or R is sodium or potassium.

17. The molecular sieve according to claim 1, characterized in that: In step (1)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.

18. The molecular sieve according to claim 1, characterized in that: In step (1)③, the crystallization conditions are: crystallization at 150-200℃ for 8-72 hours; drying temperature at 80-120℃ for 4-8 hours; and calcination temperature at 530-570℃ for 3-6 hours.

19. The molecular sieve according to claim 1, characterized in that: In step (1)③, ammonium exchange is carried out using conventional methods, and the Na2O mass content in the ZSM-23 molecular sieve after ammonium exchange is less than 0.2%; then washing, drying and calcination are carried out, with the drying temperature being 80-120℃ and the time being 4-8 hours; the calcination temperature being 530-570℃ and the time being 3-6 hours.

20. The molecular sieve according to claim 1, characterized in that: In step (2)①, the silicon source is one or two of tetraethyl orthosilicate and methyl orthosilicate, the acid is one or more of hydrochloric acid, nitric acid and sulfuric acid, and the pH of the acid solution is 1.0~4.

0.

21. The molecular sieve according to claim 1, characterized in that: In step (2)①, the stirring time is 4~10 hours and the temperature is 20~45℃; the standing aging time is 8~48 hours.

22. The molecular sieve according to claim 1, characterized in that: In step (2)②, the second template agent is poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide) triblock copolymer P123.

23. The molecular sieve according to claim 22, characterized in that: In step (2)②, aluminum isopropoxide and template agent P123 are first dissolved in an acid solution, and then mixed with other raw materials; the acid is one or more of hydrochloric acid, nitric acid and sulfuric acid, and the molar concentration of hydrogen ions in the acid solution is 0.1~0.7mol / L.

24. The molecular sieve according to claim 23, characterized in that: In step (2)②, the molar concentration of hydrogen ions in the acid solution is 0.2~0.6 mol / L.

25. The molecular sieve according to claim 1, characterized in that: In step (2)②, the mass ratio of P123 to HZSM-23 is 0.15~0.55; the mass ratio of silicon source to HZSM-23 is 1~4; the mass ratio of deionized water to HZSM-23 is 18~50; and the molar ratio of SiO2 in the silicon source to Al2O3 in aluminum isopropoxide is 15~120.

26. The molecular sieve according to claim 25, characterized in that: In step (2)②, the mass ratio of P123 to HZSM-23 is 0.18~0.50; the mass ratio of silicon source to HZSM-23 is 1.2~3; the mass ratio of deionized water to HZSM-23 is 20~40; and the molar ratio of SiO2 in the silicon source to Al2O3 in aluminum isopropoxide is 20~100.

27. The molecular sieve according to claim 1, characterized in that: In step (2)②, the mixture B needs to be stirred continuously at 15~30℃ for 6~8h before crystallization.

28. The molecular sieve according to claim 1, characterized in that: In step (2)②, the crystallization temperature of the mixture B is 80~120℃ and the crystallization time is 16~40 hours.

29. The molecular sieve according to claim 1, characterized in that: In step (2)②, the drying temperature is 80-120ºC and the time is 4-8 hours; the calcination temperature is 530-570ºC and the time is 3-6 hours.

30. The HZSM-23@Al-SBA-15 composite molecular sieve of any one of claims 1-29 is used for the hydroisomerization reaction of cycloalkane-rich feedstocks.

31. The reaction according to claim 30, characterized in that: The cycloalkane content is 30-60%; the reaction temperature is 250-350℃, and the liquid hourly space velocity is 0.5-1.5 h⁻¹. -1 The hydrogen-to-oil ratio is 600-1000, and the reaction hydrogen pressure is 3.5-5.0 MPa.

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