A zsm-22 / zsm-23 co-crystal molecular sieve, its preparation method and application

Abstract

This invention discloses a ZSM-22 / ZSM-23 eutectic molecular sieve, its preparation method, and its applications. The total acid content of the eutectic molecular sieve is 0.10~0.37 mmol / g, with the acid content below 350℃ accounting for 55~80% of the total acid content; preferably, the total acid content is 0.13~0.35 mmol / g, with the acid content below 350℃ accounting for 56~77% of the total acid content; more preferably, the total acid content is 0.15~0.33 mmol / g, with the content below 350℃ accounting for 57~75% of the total acid content. The method for preparing the ZSM-22 / ZSM-23 eutectic molecular sieve includes the following steps: (1) preparing a mixture A containing a structure-directing agent (SDA), amorphous silica-alumina, or amorphous silica-alumina precursor; (2) preparing a mixture B containing a silicon source and an alkaline source; (3) thoroughly mixing mixture A and mixture B to obtain a final gel, which is then subjected to dynamic crystallization, filtration, washing, drying, and calcination to obtain the ZSM-22 / ZSM-23 eutectic molecular sieve. The ZSM-22 / ZSM-23 eutectic molecular sieve has a high weak acid content and a low strong acid content, which can reduce hydrocracking side reactions and carbon deposition when used in isomerization reactions.

Description

Technical Field

[0001] This invention relates to a ZSM-22 / ZSM-23 eutectic molecular sieve, its preparation method, and its application. Specifically, it relates to a ZSM-22 / ZSM-23 eutectic molecular sieve, its preparation method, and its application in isomerization. Background Technology

[0002] ZSM-22 and ZSM-23 molecular sieves are two types of ten-membered ring one-dimensional porous silica-alumina molecular sieves developed by Mobil Corporation of the United States. The former has a TON topology, while the latter has an MTT topology. The two have similar pore structures and similar pore sizes (0.56×0.45 for the former and 0.52×0.45 for the latter). Both exhibit good performance in hydroisomerization reactions and can be used to improve the low-temperature fluidity of oils. Both also have relatively mature preparation methods and processes.

[0003] CN1762807A discloses a method for preparing ZSM-23 / ZSM-22 composite molecular sieves. The method involves adding ZSM-23 molecular sieve seed crystals to a gel obtained by mixing a silicon source, an aluminum source, an inorganic alkali, water, and a template agent, and then crystallizing the gel after adjusting the pH to a suitable level with acid to obtain the composite molecular sieve.

[0004] CN107311202B discloses a method for synthesizing ZSM-22 / ZSM-23 composite molecular sieves with low template agent dosage. The method involves dissolving an inorganic alkali source in deionized water, adding template agent A and an aluminum source, and then adding template agent B and a silicon source after complete dissolution to form a first initial gel. This gel is then subjected to ultrasonic oscillation to obtain a first ultrasonic mixture. A second initial gel is prepared using the same proportions (without adding template agent). The first ultrasonic mixture is added to the second initial gel, stirred evenly, and then subjected to ultrasonic oscillation. The resulting second ultrasonic mixture is transferred to a crystallization reactor for crystallization to obtain the ZSM-22 / ZSM-23 composite molecular sieve.

[0005] CN103964460B discloses a method for synthesizing ZSM-22 / ZSM-23 composite molecular sieves using a conventional sol-gel method under seedless conditions. The method involves dissolving an inorganic alkali source in deionized water, adding an aluminum source and a template agent to prepare working solution A; then adding a silicon source and adjusting the pH to 9-13, followed by aging and crystallization of the resulting gel to obtain ZSM-22 / ZSM-23 molecular sieves.

[0006] CN107416860B discloses a TON / MTT composite topological zeolite molecular sieve with controllable relative content and its preparation method. In this method, an inorganic alkali source is dissolved, and template agent A, boron / iron / gallium sources are added until completely dissolved. Then, template agent B and a silicon source are added to form an initial gel. Finally, all-silicon ZSM-22 seed crystals are added and ultrasonically vibrated. The composite molecular sieve is then crystallized in a high-pressure microwave reactor.

[0007] The aforementioned ZSM-22 / ZSM-23 composite molecular sieve has advantages such as uniform molecular sieve composition distribution and good pore structure. However, no matter how the composition of the ZSM-22 / ZSM-23 composite molecular sieve is controlled, it is impossible to solve the problem that the high content of strong acid in the composite molecular sieve can easily aggravate the hydrocracking and carbon deposition of by-reactants in the hydroisomerization reaction. Summary of the Invention

[0008] To address the shortcomings of existing technologies, this invention discloses a ZSM-22 / ZSM-23 eutectic molecular sieve, its preparation method, and its applications. The ZSM-22 / ZSM-23 eutectic molecular sieve has a high weak acid content and a low strong acid content, which, when used in isomerization reactions, can reduce hydrocracking side reactions and decrease carbon buildup.

[0009] The first aspect of this invention relates to a ZSM-22 / ZSM-23 eutectic molecular sieve, wherein the total acid content of the eutectic molecular sieve is 0.10~0.37 mmol / g, and the acid content below 350℃ accounts for 55~80% of the total acid content; preferably, the total acid content is 0.13~0.35 mmol / g, and the acid content below 350℃ accounts for 56~77% of the total acid content; more preferably, the total acid content is 0.15~0.33 mmol / g, and the content below 350℃ accounts for 57~75% of the total acid content.

[0010] The ZSM-23 relative crystallinity in the ZSM-22 / ZSM-23 eutectic molecular sieve of the present invention is 95~110%, preferably 97~108%; after hydrothermal treatment at 600℃ for 2 hours, the relative crystallinity is 94~108%, preferably 95~105%.

[0011] In the above-mentioned ZSM-22 / ZSM-23 eutectic molecular sieve, based on the weight of the ZSM-22 / ZSM-23 eutectic molecular sieve, the relative content of ZSM-22 molecular sieve is 10~95wt%, preferably 15~90wt%.

[0012] In the aforementioned ZSM-22 / ZSM-23 eutectic molecular sieve, the molar ratio of the eutectic molecular sieve is 40–200, and the specific surface area is 200–280 m². 2 / g, pore volume 0.50~0.80 cm³ 3 / g; preferably, the molar ratio is 50–180, and the specific surface area is 210–270 m². 2 / g, pore volume 0.55~0.75 cm³ 3 / g.

[0013] A second aspect of this invention relates to a method for preparing ZSM-22 / ZSM-23 eutectic molecular sieves, the method comprising the following steps: (1) Prepare a mixture A containing a structure-directing agent (SDA), amorphous silicon-aluminum or amorphous silicon-aluminum precursor; (2) Prepare a mixed solution B of silicon source and alkali source; (3) Mix mixture A and mixture B thoroughly to obtain the final gel, and then obtain ZSM-22 / ZSM-23 eutectic molecular sieve after dynamic crystallization, filtration, washing, drying and calcination.

[0014] In step (1) of the above method, the structure directing agent (SDA) is a mixture of dimethylamine and diethylamine.

[0015] In step (1) of the above method, the molar ratio of the structure-directing agent (SDA) dimethylamine to diethylamine is 12~30, preferably 15~25.

[0016] In step (1) of the above method, the molar ratio of silicon (calculated as silicon oxide) to aluminum (calculated as aluminum oxide) in the mixed solution is 1: (0.10~0.85), preferably 1: (0.20~0.80); the molar ratio of aluminum (calculated as aluminum oxide) to structure directing agent (the sum of the masses of dimethylamine and diethylamine) is 1: (10~350), preferably 1: (15~300).

[0017] In step (1) of the above method, an amorphous silicon-aluminum precursor is prepared by carbonization, and then a structure-directing agent is added to the amorphous silicon-aluminum precursor to obtain a mixture A.

[0018] In step (1) of the above method, the mixed solution A is stirred at 10~25 ℃ for 1~6 hours, preferably at 15~20 ℃ for 2~4 hours.

[0019] In step (2) of the above method, when preparing the mixed solution B, the alkali source is first dissolved in a small amount of water, and then a supplementary silicon source is added to it. The amounts of alkali source, deionized water, and supplementary silicon source are based on the aluminum (calculated as alumina) in the mixed solution in step (1), and the total feed molar ratio is SiO2 : Al2O3 : R2O (alkali source) : H2O = 1 : (0.005~0.025) : (0.015~0.08) : (40~80), SDA / SiO2 = 0.30~1.5. The preferred ratio is SiO2 / Al2O3 = 50~180, H2O / SiO2 = 30~60, R2O / SiO2 = 0.02~0.05, and SDA / SiO2 = 0.30~1.2.

[0020] In step (2) of the above method, the supplementary silicon source is one or more of silica sol, tetraethyl orthosilicate, water glass or fumed silica, preferably silica sol; the alkaline source is sodium hydroxide or / and potassium hydroxide.

[0021] In step (3) of the above method, the crystallization conditions are: dynamic crystallization at 150~200 ℃ for 16~84 hours, with a rotation speed of 10~60 rpm; preferably, dynamic crystallization at 160~180 ℃ for 20~72 hours, with a rotation speed of 20~40 rpm; drying temperature at 60~120 ℃ for 2~12 hours, preferably drying at 80~120 ℃ for 4~8 hours; calcination temperature at 500~600 ℃ for 2~8 hours, preferably calcination at 530~570 ℃ for 3~6 hours.

[0022] The aforementioned eutectic molecular sieve is used in a hydroisomerization reaction under the following conditions: reactants are mainly long-chain alkanes; reaction temperature is 200–350 °C; pressure is 3.5–4.5 MPa; hydrogen-to-oil ratio is 400–1000; and liquid hourly space velocity is 0.5–1.5 h⁻¹. -1 .

[0023] Compared with the prior art, the present invention provides a ZSM-22 / ZSM-23 eutectic molecular sieve, its preparation method, and its application, which have the following advantages: (1) The ZSM-22 / ZSM-23 eutectic molecular sieve of the present invention has a high proportion of acid content to total acid content below 350℃, and exhibits excellent catalytic performance in the hydroisomerization decondensation reaction of long-chain alkanes.

[0024] (2) In the preparation method of ZSM-22 / ZSM-23 eutectic molecular sieve provided by the present invention, all the aluminum sources required for synthesis are added when preparing the amorphous silica-alumina precursor, which promotes the generation of the primary structural unit of the molecular sieve; when two structure directing agents are added to the amorphous silica-alumina precursor, the two structure directing agents will preferentially chelate with the Al species in the primary structural unit, and then achieve the pre-assembly of the TON / MTT composite topology under their synergistic guiding effect, while better controlling the binding sites of Al atoms, promoting the later crystallization to generate a molecular sieve with more weak acid sites; when the silicon source is added to form the final gel, ZSM-22 / ZSM-23 eutectic molecular sieve is generated by dynamic crystallization. Attached Figure Description

[0025] Figure 1 The image shows the XRD pattern of the synthesized product in Example 1 of this invention.

[0026] Figure 2 This is a scanning electron microscope image of the synthesized product in Example 1 of the present invention. Detailed Implementation

[0027] In this invention, the relative crystallinity of the molecular sieve was determined by X-ray powder diffraction (XRD). Specifically, the sum of the peak areas of the diffraction peaks at 2θ of approximately 9.8–12.5° and 19.0–27.5° in the XRD pattern of ZSM-23 molecular sieve in Comparative Example 1 was used as a benchmark, with a crystallinity of 100%. The relative crystallinity of other samples was obtained by comparison with this benchmark. The crystallinity was calculated based on the ZSM-23 molecular sieve pattern in the eutectic molecular sieve.

[0028] In this invention, the acid distribution is measured by NH3 temperature-programmed desorption (NH3-TPD), wherein the acidic sites corresponding to the desorption temperature between 120 and 500 °C are taken as the total acid content, and the acidic sites corresponding to the desorption temperature below 350 °C are taken as the weak acid sites.

[0029] In this invention, wt% is the mass fraction and v% is the volume fraction.

[0030] 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.

[0031] The specific preparation process of a non-limiting amorphous silicon-aluminum precursor in this embodiment of the invention is as follows: An aluminum source (preferably sodium aluminate) solution and a silicon-containing compound solution are prepared separately; the sodium aluminate 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 optionally aged to obtain the amorphous silicon-aluminum precursor.

[0032] 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 to 85 wt% of the total amount of silicon-containing compound solution added, calculated as silicon dioxide, preferably 30 to 70 wt%.

[0033] In the preparation process of the above-mentioned amorphous silicon-aluminum precursor, the gelation reaction temperature is 10-30 °C, and the pH value after gelation is controlled to be 9-12.

[0034] 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.

[0035] In the above-mentioned preparation process of amorphous silicon-aluminum precursor, the concentration of the aluminum source solution is 15-60 g Al2O3 / L based on the mass of Al2O3, the concentration of the silicon-containing compound solution is 40-260 g SiO2 / L based on the mass of SiO2, and the concentration of the CO2 gas is 30-60 g.

[0036] In the preparation process of the above-mentioned amorphous silicon-aluminum precursor, the aging time is 5-60 minutes, preferably 10-30 minutes; the aging temperature is 10-40 ℃, preferably 15-35 ℃.

[0037] Example 1 Prepare a 40 g Al2O3 / L sodium aluminate working solution. Take a sodium silicate solution containing 28 wt% SiO2 and dilute it to a 100 g SiO2 / L sodium silicate working solution. Place 150 mL of the sodium aluminate working solution in a gelation tank, then add 50 mL of the sodium silicate working solution. Control the reaction temperature at 20 °C and introduce CO2 gas at a concentration of 50 v%. When the pH value reaches 10.0, stop introducing CO2 and add another 90 mL of the sodium silicate working solution. Then, aerate and stabilize for 15 minutes to obtain an amorphous silica-alumina precursor. Add dimethylamine and diethylamine to the amorphous silica-alumina precursor obtained above and stir at 15 °C for 2.5 hours to obtain mixture A. Dissolve sodium hydroxide in the remaining water, then add the required amount of silica sol (containing 28 wt% SiO2) dropwise, and stir until homogeneous to obtain mixture B; After thoroughly mixing mixture A and mixture B, a gel with a final molar ratio of SiO2 : Al2O3 : Na2O : DMA : DEA : H2O = 1 : 0.01 : 0.04 : 0.4 : 0.02 : 50 was obtained. The resulting gel was transferred to a stainless steel reactor and dynamically crystallized at 160 ℃ and 30 rpm for 48 hours. After crystallization, the product was filtered, washed until neutral, dried at 100 ℃ for 6 hours, and calcined in air at 550 ℃ for 3 hours to obtain product Z-1, the properties of which are shown in Table 1. Figure 1 The image shows the XRD pattern of the composite molecular sieve. Figure 2 This is a scanning electron microscope image of the composite molecular sieve.

[0038] Example 2 Prepare a 40 g Al2O3 / L sodium aluminate working solution. Take a sodium silicate solution containing 28 wt% SiO2 and dilute it to a 150 g SiO2 / L sodium silicate working solution. Place 200 mL of the sodium aluminate working solution in a gelation tank, then add 40 mL of the sodium silicate working solution. Control the reaction temperature at 25 °C and introduce CO2 gas at a concentration of 50 wt%. When the pH value reaches 10.5, stop introducing CO2 and add another 40 mL of the sodium silicate working solution. Then, allow the mixture to stabilize for 20 minutes to obtain an amorphous silica-alumina precursor. Add dimethylamine and diethylamine to the amorphous silica-alumina precursor obtained above and stir at 10 °C for 4 hours to obtain mixture A. Dissolve sodium hydroxide in the remaining water, then add the required amount of silica sol (containing 28 wt% SiO2) dropwise, and stir until homogeneous to obtain mixture B; After thoroughly mixing mixture A and mixture B, a gel with a final molar ratio of SiO2 : Al2O3 : Na2O : DMA : DEA : H2O = 1 : 0.02 : 0.02 : 1.0 : 0.04 : 50 was obtained. The resulting gel was transferred to a stainless steel reactor and dynamically crystallized at 180 ℃ and 30 rpm for 60 hours. After crystallization, the gel was filtered, washed until neutral, dried at 100 ℃ for 6 hours, and calcined in air at 550 ℃ for 6 hours to obtain product Z-2. Its properties are shown in Table 1. Its XRD pattern is similar to... Figure 1 Similarly, scanning electron microscope images and Figure 2 similar.

[0039] Example 3 Prepare a 50 g Al2O3 / L sodium aluminate working solution. Take a sodium silicate solution containing 28 wt% SiO2 and dilute it to a 100 g SiO2 / L sodium silicate working solution. Place 200 mL of the sodium aluminate working solution in a gelation tank, then add 60 mL of the sodium silicate working solution. Control the reaction temperature at 30 °C and introduce 50 wt% CO2 gas. When the pH reaches 10.0, stop introducing CO2 and add another 40 mL of the sodium silicate working solution. Then, allow the mixture to stabilize for 30 minutes to obtain an amorphous silica-alumina precursor. Add dimethylamine and diethylamine to the amorphous silica-alumina precursor obtained above and stir at 20 °C for 2 hours to obtain mixture A. Dissolve sodium hydroxide in the remaining water, then add the required amount of silica sol (containing 28 wt% SiO2) dropwise, and stir until homogeneous to obtain mixture B; After thoroughly mixing mixture A and mixture B, a gel with a final molar ratio of SiO2 : Al2O3 : Na2O : DMA : DEA : H2O = 1 : 0.005 : 0.025 : 0.60 : 0.04 : 60 was obtained. The resulting gel was transferred to a stainless steel reactor and dynamically crystallized at 160 ℃ and 40 rpm for 24 hours. After crystallization, the gel was filtered, washed until neutral, dried at 100 ℃ for 6 hours, and calcined in air at 550 ℃ for 4 hours to obtain product Z-3. Its properties are shown in Table 1. Its XRD pattern is similar to... Figure 1 Similarly, scanning electron microscope images and Figure 2 similar.

[0040] Example 4 Prepare a 20 g Al2O3 / L sodium aluminate working solution. Take a sodium silicate solution containing 28 wt% SiO2 and dilute it to a 150 g SiO2 / L sodium silicate working solution. Place 300 mL of the sodium aluminate working solution in a gelation tank, then add 20 mL of the sodium silicate working solution. Control the reaction temperature at 30 °C and introduce CO2 gas at a concentration of 50 wt%. When the pH value reaches 11.0, stop introducing CO2 and add another 20 mL of the sodium silicate working solution. Then, aerate and stabilize for 15 minutes to obtain an amorphous silica-alumina precursor. Add dimethylamine and diethylamine to the amorphous silica-alumina precursor obtained above, and stir at 20 °C for 4 hours to obtain mixture A. Dissolve sodium hydroxide in the remaining water, then add the required amount of silica sol (containing 28 wt% SiO2) dropwise, and stir until homogeneous to obtain mixture B; After thoroughly mixing mixture A and mixture B, a gel with a final molar ratio of SiO2 : Al2O3 : Na2O : DMA : DEA : H2O = 1 : 0.01 : 0.05 : 0.4 : 0.02 : 40 was obtained. The resulting gel was transferred to a stainless steel reactor and dynamically crystallized at 160 ℃ and 30 rpm for 48 hours. After crystallization, the gel was filtered, washed until neutral, dried at 100 ℃ for 6 hours, and calcined in air at 550 ℃ for 4 hours to obtain product Z-4, the properties of which are shown in Table 1. Its XRD pattern is similar to... Figure 1 Similarly, scanning electron microscope images and Figure 2 similar.

[0041] Example 5 Prepare a 40 g Al2O3 / L sodium aluminate working solution. Take a sodium silicate solution containing 28 wt% SiO2 and dilute it to a 50 g SiO2 / L sodium silicate working solution. Place 150 mL of the sodium aluminate working solution in a gelation tank, then add 140 mL of the sodium silicate working solution. Control the reaction temperature at 20 °C and introduce 50 wt% CO2 gas. When the pH reaches 10.0, stop introducing CO2 and add another 140 mL of the sodium silicate working solution. Then, aerate and stabilize for 20 minutes to obtain an amorphous silica-alumina precursor. Add dimethylamine and diethylamine to the amorphous silica-alumina precursor obtained above, and stir at 15 °C for 2 hours to obtain mixture A. Dissolve sodium hydroxide in the remaining water, then add the required amount of silica sol (containing 28 wt% SiO2) dropwise, and stir until homogeneous to obtain mixture B; After thoroughly mixing mixture A and mixture B, a gel with a final molar ratio of SiO2 : Al2O3 : Na2O : DMA : DEA : H2O = 1 : 0.01 : 0.04 : 0.5 : 0.02 : 50 was obtained. The resulting gel was transferred to a stainless steel reactor and dynamically crystallized at 180 ℃ and 30 rpm for 72 hours. After crystallization, the gel was filtered, washed until neutral, dried at 100 ℃ for 6 hours, and calcined in air at 550 ℃ for 3 hours to obtain product Z-5, the properties of which are shown in Table 1. Its XRD pattern is similar to... Figure 1 Similarly, scanning electron microscope images and Figure 2 similar.

[0042] Comparative Example 1 (Refer to CN107416860B) KOH and NaOH were added to deionized water and completely dissolved. Then, 1-methylbutylamine, methyl borate, and boric acid were added sequentially, and the mixture was stirred until completely dissolved. Finally, pentylamine and fumed silica were added sequentially to form an initial gel with a molar ratio of SiO2 : B2O3 : 1-methylbutylamine : pentylamine : OH. - Deionized water = 1 : 0.01 (molar ratio of potassium borate: boric acid = 3 : 1, based on B2O3) : 1.0 : 1.0 : 0.1 (molar ratio of KOH: NaOH = 1:1) : 70; 10 wt% all-silicon ZSM-22 as seed crystals (based on SiO2) was added to the obtained gel, and ultrasonically vibrated for 30 minutes at 50 ℃, 60 kHz frequency, and 1000 W ultrasonic power; the gel obtained after ultrasonication was transferred to a high-pressure microwave reactor and heated to 170 ℃ for crystallization for 1 hour. After filtration and washing until neutral, it was dried at 100 ℃ for 6 hours and calcined in air at 550 ℃ for 3 hours to obtain product DZ-1, the properties of which are shown in Table 1.

[0043] Comparative Example 2 (Refer to CN112479224A) 0.247 g of NaOH was dissolved in 21.5 g of deionized water, and then 13.23 g of silica sol (containing 28 wt% SiO2) was added and mixed thoroughly to obtain gel A. 0.411 g of Al2(SO4)3·18H2O was dissolved in 20 g of deionized water to obtain solution B. Solution B was slowly added dropwise to gel A, and after stirring continuously for 30 minutes, dimethylamine and diethylamine were added. After stirring for 2 hours, an initial gel with a molar ratio of 1:0.01:0.05:0.72:0.03:45 was obtained. The obtained gel was transferred to a hydrothermal reactor and dynamically crystallized at 180 °C for 66 hours (40 rpm). After filtration and washing until neutral, it was dried at 100 °C for 6 hours and then at 550 °C. After roasting in air at ℃ for 3 hours, product DZ-2 was obtained, and its properties are shown in Table 1.

[0044] Comparative Example 3 Prepare a 40 g Al2O3 / L sodium aluminate working solution. Take a sodium silicate solution containing 28 wt% SiO2 and dilute it to a 100 g SiO2 / L sodium silicate working solution. Place 150 mL of the sodium aluminate working solution in a gelation tank, then add 50 mL of the sodium silicate working solution. Control the reaction temperature at 20 ℃ and introduce CO2 gas with a concentration of 50 v%. When the pH value reaches 10.0, stop introducing CO2 and add another 90 mL of the sodium silicate working solution. Then, ventilate and stabilize for 15 minutes to obtain an amorphous silica-alumina precursor. Sodium hydroxide, dimethylamine, and diethylamine were dissolved in the remaining water, and then the required amount of silica sol (SiO2 28wt%) was added dropwise. The mixture was stirred until homogeneous to obtain mixture B. After thoroughly mixing mixture A and mixture B, a gel with a final molar ratio of SiO2 : Al2O3 : Na2O : DMA : DEA : H2O = 1 : 0.01 : 0.04 : 0.4 : 0.02 : 50 was obtained. The resulting gel was transferred to a stainless steel reactor and dynamically crystallized at 160 ℃ and 30 rpm for 48 hours. After crystallization, the product was filtered, washed until neutral, dried at 100 ℃ for 6 hours, and calcined in air at 550 ℃ for 3 hours to obtain product DZ-3, the properties of which are shown in Table 1.

[0045] Table 1 As can be seen from the data in Table 1, the preparation method of the present invention can prepare ZSM-22 / ZSM-23 composite molecular sieve with high weak acid content, low strong acid content, and controllable relative content of the two molecular sieves.

[0046] The hydroisomerization properties of ZSM-22 / ZSM-23 composite molecular sieve samples were evaluated in a fixed-bed microreactor. The composite molecular sieve was exchanged for ammonium form and then calcined to obtain the hydrogen form molecular sieve. After loading with the noble metal Pt, it was tableted, pulverized into 20-40 mesh particles, and then packed. Hexadecane was used as the loading agent. n -C 16 The model compound was reacted at a temperature of 300 °C, a pressure of 4.0 MPa, and a volume ratio of H2 / n -C 16 =600, liquid hourly space velocity is 1.2 h -1 The reaction results are as follows: Example 1: n -C 16 The conversion rate was 92.0%; i -C 16 Yield: 82.8%; Isoparaffin yield: 90.9%.

[0047] Comparative Example 1: n -C 16 The conversion rate was 92.1%; i -C 16 Yield: 51.8%; Isoparaffin yield: 76.1%.

[0048] Comparative Example 2: n -C 16 The conversion rate was 92.5%; i -C 16 Yield: 49.4%; Isoparaffin yield: 81.3%.

[0049] Comparative Example 3: n -C 16 The conversion rate was 92.6%; i -C 16 Yield: 25.9%; Isoparaffin yield: 50.5%.

Claims

1. A method for preparing ZSM-22 / ZSM-23 eutectic molecular sieve, characterized in that: The method includes the following: (1) Prepare a mixture A containing structure-directing agent SDA, amorphous silicon-aluminum or amorphous silicon-aluminum precursor; (2) Prepare a mixed solution B of silicon source and alkali source; (3) Mix mixture A and mixture B thoroughly to obtain the final gel, and then obtain ZSM-22 / ZSM-23 eutectic molecular sieve after dynamic crystallization, filtration, washing, drying and calcination; The structure-directing agent SDA is a mixture of dimethylamine and diethylamine; the molar ratio of dimethylamine to diethylamine in the structure-directing agent SDA is 12-30. In step (1), 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); the molar ratio of aluminum (calculated as aluminum oxide) to the sum of the amounts of structure-directing agents dimethylamine and diethylamine is 1: (10~350). In step (2), the amounts of alkali source, deionized water, and supplementary silicon source are based on aluminum in mixture A in step (1), calculated as alumina, according to SiO2 : Al2O3 : R2O : H2O = 1 : (0.005~0.025) : (0.015~0.08) : (40~80), where R2O is the alkali source.

2. The method according to claim 1, characterized in that: The molar ratio of the structure-directing agent SDA dimethylamine to diethylamine is 15-25.

3. The method according to claim 1, characterized in that: In step (1), the molar ratio of silicon (calculated as silicon oxide) to aluminum (calculated as aluminum oxide) in the mixture A is 1: (0.20~0.80).

4. The method according to claim 1, characterized in that: In step (1), the molar ratio of aluminum (calculated as alumina) to the sum of the amounts of structure-directing agents dimethylamine and diethylamine is 1:(15~300).

5. The method according to claim 1, characterized in that: In step (1), an amorphous silicon-aluminum precursor is prepared by carbonization, and then a structure-directing agent is added to the amorphous silicon-aluminum precursor to obtain a mixture A.

6. The method according to claim 1, characterized in that: In step (1), the mixture A is stirred at 10~25 ℃ for 1~6 hours.

7. The method according to claim 6, characterized in that: In step (1), the mixture A is stirred at 15~20 ℃ for 2~4 hours.

8. The method according to claim 1, characterized in that: In step (2), when preparing the mixture B, the alkali source is first dissolved in a small amount of water, and then a supplementary silicon source is added. The total molar ratio of the feed is: SDA / SiO2 = 0.30~1.5, SiO2 / Al2O3 = 50~180, H2O / SiO2 = 30~60, and R2O / SiO2 = 0.02~0.

05.

9. The method according to claim 1, characterized in that: In step (2), the supplementary silicon source is one or more of silica sol, tetraethyl orthosilicate, water glass or fumed silica; the alkaline source is sodium hydroxide or / and potassium hydroxide.

10. The method according to claim 9, characterized in that: In step (2), the supplementary silicon source is silica sol.

11. The method according to claim 1, characterized in that: In step (3), the crystallization conditions are: dynamic crystallization at 150~200℃ for 16~84 hours, with a rotation speed of 10~60 rpm; drying temperature of 60~120℃, drying time of 2~12 hours; calcination temperature of 500~600℃, calcination time of 2~8 hours.

12. The method according to claim 11, characterized in that: In step (3), the crystallization conditions are: dynamic crystallization at 160~180℃ for 20~72 hours, with a rotation speed of 20~40 rpm; drying temperature at 80~120℃, drying time for 4~8 hours; and calcination temperature at 530~570℃, calcination time for 3~6 hours.

13. The ZSM-22 / ZSM-23 eutectic molecular sieve prepared by any one of the methods described in claims 1-12.

14. The molecular sieve according to claim 13, characterized in that: The total acid content of the eutectic molecular sieve is 0.10~0.37 mmol / g, and the acid content below 350℃ accounts for 55~80% of the total acid content. The relative crystallinity of ZSM-23 in the ZSM-22 / ZSM-23 eutectic molecular sieve is 95~110%; after hydrothermal treatment at 600℃ for 2 hours, the relative crystallinity is 94~108%.

15. The molecular sieve according to claim 13, characterized in that: The total acidity of the eutectic molecular sieve is 0.13~0.35 mmol / g.

16. The molecular sieve according to claim 13, characterized in that: The total acidity of the eutectic molecular sieve is 0.15~0.33 mmol / g.

17. The molecular sieve according to claim 13, characterized in that: The relative crystallinity of ZSM-23 in the ZSM-22 / ZSM-23 eutectic molecular sieve is 97~108%; after hydrothermal treatment at 600℃ for 2 hours, the relative crystallinity is 95~105%.

18. The molecular sieve according to claim 13, characterized in that: In the ZSM-22 / ZSM-23 eutectic molecular sieve, the relative content of ZSM-22 molecular sieve is 10~95wt%, based on the weight of ZSM-22 / ZSM-23 eutectic molecular sieve.

19. The molecular sieve according to claim 18, characterized in that: In the ZSM-22 / ZSM-23 eutectic molecular sieve, the relative content of ZSM-22 molecular sieve is 15~90wt%, based on the weight of ZSM-22 / ZSM-23 eutectic molecular sieve.

20. The molecular sieve according to claim 13, characterized in that: In the ZSM-22 / ZSM-23 eutectic molecular sieve, the SiO2 / Al2O3 molar ratio is 40–200, and the specific surface area is 200–280 m². 2 / g, pore volume 0.50~0.80 cm³ 3 / g.

21. The molecular sieve according to claim 20, characterized in that: In the ZSM-22 / ZSM-23 eutectic molecular sieve, the SiO2 / Al2O3 molar ratio is 50–180, and the specific surface area is 210–270 m². 2 / g, pore volume 0.55~0.75 cm³ 3 / g.

22. The ZSM-22 / ZSM-23 eutectic molecular sieve according to any one of claims 13 to 21 is used for hydroisomerization reaction, characterized in that: The reaction conditions are as follows: reaction temperature 200~350 ℃, pressure 3.5~4.5 MPa, hydrogen-to-oil ratio 400~1000, and liquid hourly space velocity 0.5~1.5 h⁻¹. -1 .

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