A ZSM-12 molecular sieve and its preparation method

Abstract

The present invention discloses a ZSM-12 molecular sieve and a preparation method thereof. The preparation method first performs a hydrothermal crystallization reaction after uniformly mixing an inorganic base, a silicon-containing compound, an aluminum-containing compound, a template and water, and then separates, washes and dries the obtained solid-phase material and mixes it with an alkaline solution. The solid-phase material obtained by the roasting treatment is mixed with a silicon-containing compound, an aluminum-containing compound, an inorganic base, a template and water for treatment, and then obtains the ZSM-12 molecular sieve after separation and drying. The ZSM-12 molecular sieve provided by the present invention has two-stage mesoporous channels, and the preparation method is simple and easy.

Description

Technical Field

[0001] The present invention relates to a zeolite molecular sieve and a preparation method thereof, belonging to the field of molecular sieve synthesis and modification, and specifically relates to a ZSM-12 molecular sieve and a preparation method thereof. Background Art

[0002] Conventional zeolite molecular sieves are microporous materials with narrow pore sizes, making them unsuitable for catalytic reactions involving large hydrocarbons. Therefore, post-processing and modification are often required to create mesopores within the molecular sieve crystals to address this issue. Common methods for creating mesopores include hydrothermal treatment, acid treatment, and alkaline treatment.

[0003] CN103073019A discloses a method for preparing a hierarchical pore zeolite molecular sieve. The method involves mixing various raw materials into a uniform white colloidal substance, placing it in a stainless steel reactor, and hydrothermally treating it at 170°C for 8 to 24 hours. The mixture is then vacuum filtered, and the filtrate is retained for later use. A template, ammonia water, and silica sol are then added to the filtrate, stirred uniformly, and hydrothermally crystallized to obtain a ZSM-12 hierarchical pore zeolite molecular sieve having mesopores or macropores between the grains.

[0004] CN106966408A discloses a bifunctional template for the synthesis of hierarchically porous ZSM-12 zeolite molecular sieves, its preparation, and molecular sieves based thereon. The invention is characterized by the preparation of the bifunctional template. The method for preparing the bifunctional template comprises the following steps: dissolving at least one of 1,4-dichlorobenzyl, α,α'-dibromo-p-xylene, and 1,4-benzenediol with at least one of N,N,N',N'-tetramethyl-1,3-butanediamine, N,N,N',N'-tetramethyl-1,5-pentanediamine, N,N-dimethylhexylamine, N,N,N',N'-tetramethyl-1,6-hexanediamine, and their homologues in a solvent, and heating and incubating the reaction to obtain the bifunctional template. The bifunctional template is then used in a one-step hydrothermal process to obtain a mesoporous-microporous bifunctional hierarchical ZSM-12 molecular sieve.

[0005] CN109665541A discloses a method for synthesizing a low-silicon-to-aluminum ratio ZSM-12 zeolite molecular sieve. This method involves uniformly mixing a silicon source, an aluminum source, an alkaline substance, a template, and water according to a specific material ratio to obtain a mixture. The mixture is then hydrothermally crystallized at 95-180°C for 20-200 hours. The resulting product is then washed and dried to obtain a low-silicon-to-aluminum ratio ZSM-12 zeolite molecular sieve. However, this product is a conventional microporous molecular sieve and does not contain a mesoporous structure. Summary of the Invention

[0006] In response to the shortcomings of the prior art, the main purpose of the present invention is to provide a ZSM-12 molecular sieve containing abundant mesoporous channels and a method for preparing the same. The ZSM-12 molecular sieve provided by the present invention has two levels of mesoporous channels and provides a simple and easy method for preparing the mesoporous ZSM-12 molecular sieve.

[0007] In order to achieve the above-mentioned object of the invention, the first aspect of the present invention provides a method for preparing ZSM-12 molecular sieve, comprising the following steps:

[0008] (1) mixing an inorganic base, a silicon-containing compound, an aluminum-containing compound, a template and water, performing a hydrothermal crystallization reaction after uniform mixing, and then further separating, washing and drying;

[0009] (2) mixing the solid phase material obtained in step (1) with an alkaline solution and then performing a roasting treatment;

[0010] (3) The solid phase material obtained in step (2) is mixed with a silicon-containing compound, an aluminum-containing compound, an inorganic base, a template agent and water, and the mixture is treated after being evenly mixed, and then separated and dried to obtain a ZSM-12 molecular sieve.

[0011] In the above-mentioned preparation method of ZSM-12 molecular sieve, the inorganic base in step (1) is at least one of sodium hydroxide and potassium hydroxide.

[0012] In the above-mentioned preparation method of ZSM-12 molecular sieve, the aluminum-containing compound in step (1) can be selected from one or more of sodium aluminate, aluminum sulfate, aluminum chloride, and aluminum nitrate, preferably one or more of aluminum chloride and aluminum nitrate.

[0013] In the above-mentioned preparation method of ZSM-12 molecular sieve, the silicon-containing compound in step (1) can be selected from one or more of silica gel, white carbon black, silica sol, and water glass, preferably one or more of white carbon black and silica gel.

[0014] In the above-mentioned preparation method of ZSM-12 molecular sieve, the template agent in step (1) is methyltriethylammonium chloride.

[0015] In the above-mentioned preparation method of ZSM-12 molecular sieve, the molar ratio of the inorganic base, silicon-containing compound, aluminum-containing compound, template and water described in step (1) is 1-10 inorganic base: 20-120SiO2: Al2O3: 500-2300H2O: 2-25M, preferably 2-8 inorganic base: 25-110SiO2: Al2O3: 600-2000H2O: 5-20M, where M represents the template.

[0016] In the above-mentioned preparation method of ZSM-12 molecular sieve, the hydrothermal crystallization reaction conditions in step (1) are as follows: the reaction temperature is 140 to 200° C., preferably the reaction temperature is 150 to 190° C.; the reaction time is 17 to 55 hours, preferably the reaction time is 20 to 50 hours.

[0017] In the above-mentioned preparation method of ZSM-12 molecular sieve, the separation in step (1) is liquid-solid separation, and any of the existing methods for achieving liquid and solid phase separation can be used, specifically centrifugation, filtration, etc., preferably filtration; generally, multiple filtrations are required, such as 1 to 10 times.

[0018] In the above-mentioned preparation method of ZSM-12 molecular sieve, the drying conditions in step (1) are as follows: the drying temperature is 100-150° C., and the drying time is 1-10 h.

[0019] In the above-mentioned method for preparing ZSM-12 molecular sieve, the alkaline solution in step (2) is an aqueous solution of an inorganic base, specifically at least one of an aqueous sodium hydroxide solution and an aqueous potassium hydroxide solution. The mass concentration of the alkaline solution is 0.05 wt% to 0.35 wt%, preferably 0.1 wt% to 0.3 wt%.

[0020] In the above-mentioned preparation method of ZSM-12 molecular sieve, the mass ratio of the alkaline solution in step (2) to the solid phase material obtained in step (1) is 0.7 to 1.1:1, preferably 0.8 to 1:1.

[0021] In the above-mentioned preparation method of ZSM-12 molecular sieve, the treatment temperature in step (2) is 500-800°C, preferably 600-700°C; and the treatment time is 2-7h, preferably 3-5h.

[0022] In the above-mentioned preparation method of ZSM-12 molecular sieve, the inorganic base in step (3) is at least one of sodium hydroxide and potassium hydroxide.

[0023] In the above-mentioned preparation method of ZSM-12 molecular sieve, the aluminum-containing compound in step (3) can be selected from one or more of sodium aluminate, aluminum sulfate, aluminum chloride, and aluminum nitrate, preferably one or more of aluminum chloride and aluminum nitrate.

[0024] In the above-mentioned preparation method of ZSM-12 molecular sieve, the silicon-containing compound in step (3) can be selected from one or more of silica gel, white carbon black, silica sol, and water glass, preferably one or more of white carbon black and silica gel.

[0025] In the above-mentioned preparation method of ZSM-12 molecular sieve, the template agent in step (3) is methyltriethylammonium chloride.

[0026] In the above-mentioned method for preparing ZSM-12 molecular sieve, the mass ratio of the solid phase material obtained in step (2) described in step (3) to the silicon-containing compound is 1:0.1 to 1:0.6.

[0027] In the above-mentioned method for preparing ZSM-12 molecular sieve, the mass ratio of the solid phase material obtained in step (2) described in step (3) to the aluminum-containing compound is 1:0.01 to 1:0.04.

[0028] In the above-mentioned preparation method of ZSM-12 molecular sieve, the mass ratio of the solid phase material obtained in step (2) described in step (3) to the inorganic base is 1:0.2 to 1:0.5.

[0029] In the above-mentioned method for preparing ZSM-12 molecular sieve, the mass ratio of the solid phase material obtained in step (2) described in step (3) to the template agent is 1:0.2 to 1:0.5.

[0030] In the above-mentioned method for preparing ZSM-12 molecular sieve, the mass ratio of the solid phase material obtained in step (2) described in step (3) to water is 1:15 to 1:25.

[0031] In the above-mentioned method for preparing ZSM-12 molecular sieve, the mixing in step (3) is preferably carried out under ultrasonic conditions, with an ultrasonic frequency of 15 kHz to 10 MHz and a power of 20 to 100 W / L based on the volume of the solution. The ultrasonic treatment time is 0.1 to 10 minutes, preferably 1 to 5 minutes. The specific mixing process has no specific restrictions on the order in which the materials are introduced.

[0032] In the above-mentioned method for preparing ZSM-12 molecular sieve, the treatment conditions described in step (3) are: a treatment temperature of 130 to 170°C, preferably 120 to 190°C; and a treatment time of 0.5 to 12 hours, preferably 3 to 16 hours. The treatment process described in step (3) generally needs to be carried out in a high-pressure reactor.

[0033] In the above-mentioned method for preparing ZSM-12 molecular sieve, the separation described in step (3) is mainly to remove unreacted raw materials, including silicon, aluminum, alkali and other substances. Any existing method capable of achieving liquid-phase and solid-phase separation can be used, specifically centrifugation, filtration and the like, with filtration being preferred. In general, multiple filtrations are required, such as 1 to 10 times.

[0034] In the above-mentioned preparation method of ZSM-12 molecular sieve, the drying conditions in step (3) are: drying time is 1 to 10 hours, and drying temperature is 100 to 150°C.

[0035] The second aspect of the present invention provides a ZSM-12 molecular sieve obtained by the above preparation method.

[0036] The above-mentioned ZSM-12 molecular sieve is a porous molecular sieve crystal material with two-level mesoporous channels. The pore diameter of the first-level channel is 2 to 7 nm, and its most probable pore diameter is 3 to 6 nm; the pore diameter of the second-level channel is 7 to 50 nm, and its most probable pore diameter is 10 to 20 nm; furthermore, the proportion of the first-level channel is 80 to 90%; and the proportion of the second-level channel is 10 to 20%.

[0037] The total specific surface area of ​​the ZSM-12 molecular sieve is 400 to 600 m 2 / g, the mesopore specific surface area is 40~240m 2 / g.

[0038] The ZSM-12 molecular sieve of the present invention has unique physical and chemical characteristics. During the adsorption or catalytic reaction process, due to its excellent secondary mesoporous channel structure, it has a special screening effect on reactants.

[0039] The ZSM-12 molecular sieve and its preparation method of the present invention have the following technical effects:

[0040] The ZSM-12 molecular sieve preparation method of the present invention first prepares a ZSM-12 molecular sieve precursor, and then treats it with a low-concentration alkaline solution under high temperature conditions. During the treatment process, a small amount of silicon, aluminum and oxygen elements in the crystal are shifted from their original positions, resulting in slight structural defects on the molecular sieve, which will not affect the overall structure of the molecular sieve and can improve the efficiency of mesopore formation in the final product. Then, the hydrothermal reaction is continued, and a small amount of silicon-containing compound, aluminum-containing compound, inorganic base, template and water are added in step (3). These raw materials can re-enter the crystal framework of the molecular sieve during the formation of mesopores, repairing the molecular sieve crystal structure destroyed by the introduction of alkali in step (2). It is ensured that the prepared mesoporous ZSM-12 molecular sieve has a high degree of crystallinity, and both mesopores can be obtained and the crystallinity of the molecular sieve can be maintained as much as possible. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] Figure 1 This is the pore size distribution diagram of the sample obtained in Example 1.

[0042] Figure 2 This is the pore size distribution diagram of the sample obtained in Comparative Example 1. DETAILED DESCRIPTION

[0043] The technical solutions and effects of the present invention are further illustrated below with reference to the following embodiments, but are not limited to the following embodiments.

[0044] Pore ​​structure parameters such as specific surface area of ​​the samples used in this study were measured using low-temperature nitrogen adsorption, using an ASAP2400 physical adsorption instrument produced by Micromeritics Instruments. Prior to measurement, the samples were vacuum-treated at 300°C for at least 4 hours. The total specific surface area was calculated using the BET isotherm equation, the micropore specific surface area and mesopore specific surface area were calculated using the t-plot method, and the pore size distribution was calculated using the BJH method.

[0045] The crystal structure of the sample in the present invention was characterized by an X-ray diffractometer, using a Japanese Rigaku D / max2500 X-ray diffractometer with a Cu target, a Kα radiation source, a graphite monochromator, a tube voltage of 40 kV, a tube current of 80 mA, a scanning range of 5° to 40°, a step size of 0.1°, and a scanning speed of 1° / min.

[0046] Example 1

[0047] In a clean container, place 6 g of sodium hydroxide, 125 g of silica gel, 10 g of aluminum sulfate, 50 g of methyltriethylammonium chloride, and 1000 g of distilled water. Heat the mixture at 160°C for 30 h. After the reaction, filter the solid sample several times and dry it in an oven at 110°C for 10 h to obtain a solid. Next, mix 10 g of the solid prepared in the previous step with 9 mL of 0.2 wt% sodium hydroxide solution and heat it in a muffle furnace at 700°C for 5 h. The solution was then placed in a clean container with 2.6g of potassium hydroxide, 2.5g of silica gel, 0.15g of sodium aluminate, 2.6g of methyltriethylammonium chloride, and 200mL of distilled water, stirred thoroughly, and then placed in an ultrasonic cleaner at a frequency of 10MHz and a power of 100W / L based on the solution volume for 3 minutes. The solution was then transferred to a pressure-resistant reactor and treated at 153°C for 5.5 hours. The resulting sample was filtered multiple times and then dried in an oven at 110°C for 12 hours. The resulting sample, designated C1, was subjected to low-temperature nitrogen adsorption testing and calculated using the BJH method to contain two levels of mesoporous channels. The most probable pore size of the first-level mesopores was 3nm, accounting for 87% of the total pore size, while the most probable pore size of the second-level mesopores was 10nm, accounting for 13% of the total pore size.

[0048] Example 2

[0049] In a clean container, place 9.3 g of sodium hydroxide, 192 g of white carbon black, 10 g of aluminum sulfate, 88 g of methyltriethylammonium chloride, and 1050 g of distilled water. Heat the mixture at 150°C for 50 h. After the reaction, filter the solid sample several times and dry it in an oven at 110°C for 10 h to obtain a solid. Next, mix 10 g of the solid prepared in the previous step with 8 mL of 0.1 wt% potassium hydroxide solution and heat it in a muffle furnace at 700°C for 5 h. The sample was then mixed with 2.0g of sodium hydroxide, 1g of silica gel, 0.1g of sodium aluminate, 2.0g of methyltriethylammonium chloride, and 150mL of distilled water in a clean container and stirred thoroughly. The sample was then placed in an ultrasonic cleaner at a frequency of 10MHz and a power of 100W / L based on the volume of the solution for 1 minute. The sample was then transferred to a pressure-resistant reactor and treated at 120°C for 16 hours. The resulting sample was filtered multiple times and then dried in an oven at 110°C for 12 hours. The resulting sample, designated C2, was subjected to low-temperature nitrogen adsorption testing and calculated using the BJH method. The results showed that the sample contained two levels of mesoporous channels: the most probable pore size of the first-level mesopores was 5nm, accounting for 81% of the total pore size; the most probable pore size of the second-level mesopores was 15nm, accounting for 19% of the total pore size.

[0050] Example 3

[0051] In a clean container, place 2.4 g of sodium hydroxide, 45 g of silica gel, 10 g of aluminum sulfate, 23 g of methyltriethylammonium chloride, and 320 g of distilled water. The mixture was then treated at 190°C for 20 h. After the reaction, the solid sample was filtered multiple times and then dried in an oven at 110°C for 10 h to obtain a solid. Next, 10 g of the solid prepared in the previous step was mixed with 10 mL of 0.3 wt% sodium hydroxide solution and treated in a muffle furnace at 700°C for 5 h. The mixture was then mixed with 5.0 g of potassium hydroxide, 6 g of white carbon black, 0.4 g of aluminum nitrate, 5.0 g of methyltriethylammonium chloride, and 250 mL of distilled water in a clean container and stirred thoroughly. The mixture was then placed in an ultrasonic cleaner at a frequency of 10 MHz and a power of 100 W / L based on the volume of the solution for 5 min. The mixture was then transferred to a pressure reactor and treated at 190°C for 3 h. The resulting sample was then filtered multiple times and dried in an oven at 110°C for 12 h. The resulting sample is designated C3. The obtained sample was tested by low-temperature nitrogen adsorption and calculated using the BJH method. It was found that the sample includes two levels of mesoporous channels. The most probable pore size of the first-level mesopores is 6nm, and its proportion is 85%; the most probable pore size of the second-level mesopores is 17nm, and its proportion is 15%.

[0052] Example 4

[0053] In a clean container, place 5 g of potassium hydroxide, 105 g of silica gel, 10 g of aluminum sulfate, 40 g of methyltriethylammonium chloride, and 900 g of distilled water. The mixture was then treated at 165°C for 40 h. After the reaction, the solid sample was filtered multiple times and then dried in an oven at 110°C for 10 h to obtain a solid. Next, 10 g of the solid prepared in the previous step was mixed with 8 mL of a 0.15 wt% potassium hydroxide solution and treated in a muffle furnace at 650°C for 4 h. The mixture was then mixed with 5.5 g of sodium hydroxide, 2.7 g of white carbon black, 0.18 g of aluminum chloride, 5.3 g of methyltriethylammonium chloride, and 210 mL of distilled water. The sample was then ultrasonically cleaned at a frequency of 10 MHz and a power of 100 W / L per volume for 3 min. The sample was then transferred to a pressure reactor and treated at 165°C for 3.5 h. The resulting sample was filtered multiple times and then dried in an oven at 110°C for 12 h. The resulting sample is designated C4. The obtained sample was subjected to low-temperature nitrogen adsorption test and calculated using the BJH method. It was found that the sample includes two levels of mesoporous channels. The most probable pore diameter of the first-level mesopores is 4.5nm, and its proportion is 82%; the most probable pore diameter of the second-level mesopores is 16nm, and its proportion is 18%.

[0054] Example 5

[0055] In a clean container, place 5g of potassium hydroxide, 80g of silica gel, 10g of aluminum sulfate, 38g of methyltriethylammonium chloride, and 500g of distilled water. The mixture was then treated at 155°C for 38 hours. After the reaction, the solid sample was filtered several times and then dried in an oven at 110°C for 10 hours to obtain a solid. Next, 10g of the solid prepared in the previous step was mixed with 9mL of 0.1wt% sodium hydroxide solution and treated in a muffle furnace at 700°C for 5 hours. The mixture was then mixed with 4.3g of potassium hydroxide, 2.1g of silica gel, 0.11g of aluminum sulfate, 2.6g of methyltriethylammonium chloride, and 200mL of distilled water in a clean container and stirred thoroughly. The mixture was then placed in an ultrasonic cleaner at a frequency of 10MHz and a power of 100W / L based on the volume of the solution for 3 minutes. The mixture was then transferred to a pressure reactor and treated at 145°C for 5 hours. The resulting sample was filtered several times and then dried in an oven at 110°C for 12 hours. The resulting sample was designated C5. The obtained sample was subjected to low-temperature nitrogen adsorption test and calculated using the BJH method. It was found that the sample includes two levels of mesoporous channels. The most probable pore size of the first-level mesopores is 5.5nm, accounting for 86%; the most probable pore size of the second-level mesopores is 18nm, accounting for 14%.

[0056] Comparative Example 1

[0057] In a clean container, place 6 g of sodium hydroxide, 125 g of silica gel, 10 g of aluminum sulfate, 50 g of methyltriethylammonium chloride, and 1000 g of distilled water. The mixture was then treated at 160°C for 30 h. After the reaction, the solid sample was filtered multiple times and then dried in an oven at 110°C for 10 h to obtain a solid. Next, 10 g of the solid prepared in the previous step was mixed with 9 mL of a 0.2 wt% sodium hydroxide solution and treated in a muffle furnace at 700°C for 5 h. The mixture was then mixed with 2.6 g of potassium hydroxide and 200 mL of distilled water in a clean container and stirred thoroughly. The mixture was then placed in an ultrasonic cleaner at a frequency of 10 MHz and a power of 100 W / L per volume of the solution for 3 min. The mixture was then transferred to a pressure reactor and treated at 153°C for 5.5 h. The resulting sample was filtered multiple times and then dried in an oven at 110°C for 12 h. The resulting sample is designated C6. The obtained sample was subjected to a low-temperature nitrogen adsorption test and calculated using the BJH method. It was found that the mesopore distribution of the sample consisted of one mesopore, and the most probable pore diameter of the first mesopore was 22 nm. Compared with Comparative Example 1, the surface area, mesopore area, and crystallinity were greatly reduced, indicating that this method has great defects compared with the present invention.

[0058] Comparative Example 2

[0059] In a clean container, place 9.3 g of sodium hydroxide, 192 g of white carbon black, 10 g of aluminum sulfate, 88 g of methyltriethylammonium chloride, and 1050 g of distilled water. Heat the mixture at 150°C for 50 h. After the reaction, filter the solid sample several times and dry it in an oven at 110°C for 10 h to obtain a solid. Next, mix 10 g of the solid prepared in the previous step with 8 mL of 0.1 wt% potassium hydroxide solution and heat it in a muffle furnace at 700°C for 5 h. The sample was then placed in a clean container with 2.0g of sodium hydroxide, 1g of silica gel, 0.1g of sodium aluminate, 2.0g of methyltriethylammonium chloride, and 150mL of distilled water, stirred evenly, and then placed in an ultrasonic cleaner with an ultrasonic frequency of 10MHz and a power of 100W / L based on the volume of the solution, and ultrasonic treatment was performed for 1 minute. The sample was then transferred to a pressure-resistant reactor and treated at 120°C for 16 hours. The resulting sample was filtered multiple times and then dried in an oven at 110°C for 12 hours. The resulting sample was numbered C7. The resulting sample was subjected to low-temperature nitrogen adsorption testing and calculated using the BJH method. The mesopore distribution of the sample consisted of two mesopores. The most probable pore size of the first mesopore was 4nm, accounting for 78%; the most probable pore size of the second mesopore was 15nm, accounting for 22%. Compared with Comparative Example 2, the sample had a lower mesopore area and lower crystallinity, indicating that this method has some shortcomings compared to the present invention.

[0060] Comparative Example 3

[0061] In a clean container, place 2.4 g of sodium hydroxide, 45 g of silica gel, 10 g of aluminum sulfate, 23 g of methyltriethylammonium chloride, and 320 g of distilled water. The mixture was then treated at 190°C for 20 h. After the reaction, the solid sample was filtered multiple times and then dried in an oven at 110°C for 10 h to obtain a solid. Next, 10 g of the solid prepared in the previous step was mixed with 10 mL of 0.3 wt% sodium hydroxide solution and treated in a muffle furnace at 700°C for 5 h. The mixture was then mixed with 5.0 g of potassium hydroxide, 45 g of white carbon black, 10 g of aluminum nitrate, 23 g of methyltriethylammonium chloride, and 320 mL of distilled water in a clean container and stirred thoroughly. The mixture was then placed in an ultrasonic cleaner at a frequency of 10 MHz and a power of 100 W / L based on the volume of the solution for 5 min. The mixture was then transferred to a pressure reactor and treated at 190°C for 3 h. The resulting sample was filtered multiple times and then dried in an oven at 110°C for 12 h. The resulting sample is designated C6. The obtained sample is ZSM-12 molecular sieve, but has no obvious mesoporous structure and is a conventional microporous molecular sieve.

[0062] Table 1 Pore structure properties of samples of Examples and Comparative Examples

[0063] Table 1 Pore structure properties of samples of Examples and Comparative Examples

[0064]

[0065] Note: In the present invention, the crystallinity of the ZSM-12 molecular sieve in Example 1 is taken as 100%, and the crystallinity of all samples is obtained by comparing with the crystallinity of the ZSM-12 molecular sieve in Example 1.

[0066] Comparison of the embodiments and comparative examples shows that the method of the present invention can not only produce abundant mesopores but also maintain a high degree of crystallinity.

Claims

1. A method for preparing ZSM-12 molecular sieve, comprising the following steps: (1) mixing an inorganic base, a silicon-containing compound, an aluminum-containing compound, a template and water, performing a hydrothermal crystallization reaction after uniform mixing, and then further separating, washing and drying; (2) mixing the solid phase material obtained in step (1) with an alkaline solution, and then calcining the mixture; the mass concentration of the alkaline solution is 0.05wt% to 0.35wt%, and the treatment temperature is 500 to 800°C; (3) The solid phase material obtained in step (2) is mixed with a silicon-containing compound, an aluminum-containing compound, an inorganic base, a template agent and water, and the mixture is treated after being evenly mixed, and then separated and dried to obtain a ZSM-12 molecular sieve.

2. The method for preparing the ZSM-12 molecular sieve according to claim 1, wherein: The inorganic base in step (1) is at least one of sodium hydroxide and potassium hydroxide.

3. The method for preparing the ZSM-12 molecular sieve according to claim 1, wherein: The aluminum-containing compound in step (1) is selected from one or more of sodium aluminate, aluminum sulfate, aluminum chloride, and aluminum nitrate.

4. The method for preparing the ZSM-12 molecular sieve according to claim 1 or 3, wherein: The aluminum-containing compound in step (1) is selected from one or more of aluminum chloride and aluminum nitrate.

5. The method for preparing the ZSM-12 molecular sieve according to claim 1, wherein: The silicon-containing compound in step (1) is selected from one or more of silica gel, white carbon black, silica sol, and water glass.

6. The method for preparing the ZSM-12 molecular sieve according to claim 1 or 5, wherein: The silicon-containing compound in step (1) is selected from one or more of white carbon black and silica gel.

7. The method for preparing the ZSM-12 molecular sieve according to claim 1, wherein: The template agent in step (1) is methyltriethylammonium chloride.

8. The method for preparing the ZSM-12 molecular sieve according to claim 1, wherein: The molar ratio of the inorganic base, silicon-containing compound, aluminum-containing compound, water and template in step (1) is 1-10 inorganic base: 20-120 SiO2: Al2O3: 500-2300 H2O: 2-25M, where M represents the template.

9. The method for preparing the ZSM-12 molecular sieve according to claim 1 or 8, wherein: The molar ratio of the inorganic base, silicon-containing compound, aluminum-containing compound, water and template in step (1) is 2-8 inorganic base: 25-110 SiO2: Al2O3: 600-2000 H2O: 5-20M, where M represents the template.

10. The method for preparing the ZSM-12 molecular sieve according to claim 1, wherein: The hydrothermal crystallization reaction conditions in step (1) are as follows: reaction temperature is 140-200° C., and reaction time is 17-55 h.

11. The method for preparing the ZSM-12 molecular sieve according to claim 1, wherein: The hydrothermal crystallization reaction conditions in step (1) are as follows: reaction temperature is 150-190° C., and reaction time is 20-50 h.

12. The method for preparing the ZSM-12 molecular sieve according to claim 1, wherein: The drying conditions in step (1) are as follows: drying temperature is 100-150° C., and drying time is 1-10 h.

13. The method for preparing ZSM-12 molecular sieve according to claim 1, wherein: The alkaline solution in step (2) is an aqueous solution of an inorganic base, which is at least one of an aqueous sodium hydroxide solution and an aqueous potassium hydroxide solution; the mass concentration of the alkaline solution is 0.1 wt% to 0.3 wt%.

14. The method for preparing the ZSM-12 molecular sieve according to claim 1, wherein: The mass ratio of the alkaline solution in step (2) to the solid phase material obtained in step (1) is 0.7 to 1.1:

1.

15. The method for preparing the ZSM-12 molecular sieve according to claim 1 or 14, wherein: The mass ratio of the alkaline solution in step (2) to the solid phase material obtained in step (1) is 0.8 to 1:

1.

16. The method for preparing the ZSM-12 molecular sieve according to claim 1, wherein: The processing time in step (2) is 2 to 7 hours.

17. The method for preparing ZSM-12 molecular sieve according to claim 1, wherein: In step (2), the treatment temperature is 600-700° C. and the treatment time is 3-5 h.

18. The method for preparing ZSM-12 molecular sieve according to claim 1, wherein: The inorganic base in step (3) is at least one of sodium hydroxide and potassium hydroxide.

19. The method for preparing ZSM-12 molecular sieve according to claim 1, wherein: The aluminum-containing compound in step (3) is selected from one or more of sodium aluminate, aluminum sulfate, aluminum chloride, and aluminum nitrate.

20. The method for preparing ZSM-12 molecular sieve according to claim 1 or 19, wherein: The aluminum-containing compound in step (3) is selected from one or more of aluminum chloride and aluminum nitrate.

21. The method for preparing ZSM-12 molecular sieve according to claim 1, wherein: The silicon-containing compound in step (3) is selected from one or more of silica gel, white carbon black, silica sol, and water glass.

22. The method for preparing ZSM-12 molecular sieve according to claim 1 or 21, wherein: The silicon-containing compound in step (3) is selected from one or more of white carbon black and silica gel.

23. The method for preparing ZSM-12 molecular sieve according to claim 1, wherein: In step (3), the template agent is methyltriethylammonium chloride.

24. The method for preparing ZSM-12 molecular sieve according to claim 1, wherein: The mass ratio of the solid phase material obtained in step (2) to the silicon-containing compound in step (3) is 1:0.1 to 1:0.

6.

25. The method for preparing ZSM-12 molecular sieve according to claim 1, wherein: The mass ratio of the solid phase material obtained in step (2) to the aluminum-containing compound in step (3) is 1:0.01 to 1:0.

04.

26. The method for preparing ZSM-12 molecular sieve according to claim 1, wherein: The mass ratio of the solid phase material obtained in step (2) to the inorganic base in step (3) is 1:0.2 to 1:0.

5.

27. The method for preparing ZSM-12 molecular sieve according to claim 1, wherein: The mass ratio of the solid phase material obtained in step (2) to the template in step (3) is 1:0.2 to 1:0.

5.

28. The method for preparing ZSM-12 molecular sieve according to claim 1, wherein: The mass ratio of the solid phase material obtained in step (2) to water in step (3) is 1:15 to 1:

25.

29. The method for preparing ZSM-12 molecular sieve according to claim 1, wherein: The treatment conditions in step (3) are: treatment temperature of 120 to 190° C., and treatment time of 0.5 to 16 h.

30. The method for preparing the ZSM-12 molecular sieve according to claim 1, wherein: The treatment conditions in step (3) are: treatment temperature is 130-170° C., and treatment time is 3-16 h.

31. The method for preparing the ZSM-12 molecular sieve according to claim 1, wherein: The drying conditions in step (3) are: drying time is 1 to 10 hours, and drying temperature is 100 to 150°C.

32. A ZSM-12 molecular sieve obtained by the preparation method according to any one of claims 1 to 31.

33. The ZSM-12 molecular sieve according to claim 32, wherein ZSM-12 molecular sieve is a porous molecular sieve crystal material with two levels of mesoporous channels. The pore size of the first-level channel is 2 to 7 nm, and its most probable pore size is 3 to 6 nm; the pore size of the second-level channel is 7 to 50 nm, and its most probable pore size is 10 to 20 nm; the proportion of the first-level channel is 80 to 90%; the proportion of the second-level channel is 10 to 20%.

34. The ZSM-12 molecular sieve according to claim 32, wherein The total specific surface area of ​​ZSM-12 molecular sieve is 400~600m 2 / g, the mesopore specific surface area is 40~240m 2 / g.

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