A mesoporous SAPO-34 molecular sieve and its preparation method

Abstract

The present invention discloses a kind of SAPO 34 molecular sieve and preparation method thereof, the SAPO 34 molecular sieve pore size distribution presents secondary mesoporous channel relatively concentrated distribution feature, the pore size of the first level mesopore is 2~6nm, and the pore size of the second level mesopore is 6~50nm. The SAPO 34 molecular sieve preparation method first carries out crystallization reaction after phosphoric acid, tetraethyl orthosilicate, aluminum isopropoxide, morpholine and water are mixed uniformly, then separated, washed, dried and high temperature heat treated;Finally, the solid phase material obtained is mixed with phosphoric acid, tetraethyl orthosilicate, aluminum isopropoxide, morpholine, acid and water, reacted after mixing uniformly, then separated and dried to obtain SAPO 34 molecular sieve. The present invention provides a kind of mesoporous SAPO 34 molecular sieve and preparation method thereof, the SAPO 34 molecular sieve not only has abundant mesoporous channel, but also has higher crystallinity.

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 SAPO-34 molecular sieve and a preparation method thereof. Background Art

[0002] Union Carbide Corporation in the United States was the first to discover a new type of aluminum silicon phosphate molecular sieve with adjustable pore size, abbreviated as SAPO-n. Similar to chabazite, its crystals consist of eight-membered rings, with oxygen atoms linking phosphorus, aluminum, and silicon to form three-dimensional intersecting pores. SAPO-34, a type of SAPO, possesses a unique pore structure and acidic properties, resulting in exceptional catalytic activity and has been widely used in the coal-to-olefins (CTO) and methanol-to-olefins (MTO) industries. However, due to its small pore size, SAPO-34 hinders product diffusion and is prone to secondary reactions. During use, catalysts supported on SAPO-34 are prone to coking, resulting in carbon deposits that clog the pores and deactivate the catalyst, shortening its lifespan and limiting its application.

[0003] CN107954448A discloses a straight-through pore mesoporous SAPO-34 molecular sieve and a preparation method thereof. The invention adopts a secondary treatment method to impregnate a microemulsion rich in silicon / aluminum / phosphorus / SAPO-34 template / structure directing agent into the mesoporous molecular sieve, adjust the appropriate pH, and epitaxially grow the SAPO-34 molecular sieve on the inner surface of the mesoporous molecular sieve through secondary crystallization at a certain temperature, thereby generating a straight-through mesoporous SAPO-34 molecular sieve.

[0004] CN108892152A discloses a method for preparing a mesoporous SAPO-34 molecular sieve. The method comprises the following steps: first, adding sucrose to deionized water and stirring to obtain a sucrose solution; adding an aluminum source to the sucrose solution, stirring and drying to obtain a mixture A; grinding the mixture A and carbonizing it to obtain a carbon-based aluminum compound; then, adding deionized water, a carbon-based aluminum compound, a template A, a template B, a phosphorus source and a silicon source under stirring to obtain an initial gel; then, crystallizing the gel in a high-temperature autogenous pressure crystallization reactor; centrifuging, washing and drying to obtain a SAPO-34 molecular sieve raw powder; and then calcining the raw powder to obtain the mesoporous SAPO-34 molecular sieve.

[0005] CN109179448A discloses a novel method for rapidly preparing mesoporous small-particle SAPO-34 molecular sieves. The method comprises: mixing a phosphorus source and water to form a mixed solution, slowly adding an aluminum source or pseudo-boehmite to form a translucent slurry; adding the mixture to a reaction tank, and adding a silicon source all at once; then adding a template agent, tetraethylammonium hydroxide, and thoroughly mixing and aging; then adding an organic pore-forming medium and thoroughly mixing; slowly heating, then raising the temperature to 180-220°C, and crystallizing for 0.5-3 hours; after crystallization is complete, naturally cooling the crystallization solution to room temperature and filtering to obtain crystallized SAPO-34 crystals; repeatedly washing the solid crystals with water until neutral, and removing the organic pore-forming medium; and drying the solid at 80-150°C to obtain a SAPO-34 product. Summary of the Invention

[0006] In view of the deficiencies in the prior art, the present invention provides a mesoporous SAPO-34 molecular sieve and a preparation method thereof. The SAPO-34 molecular sieve not only has abundant mesoporous channels but also has high crystallinity.

[0007] The first aspect of the present invention provides a mesoporous SAPO-34 molecular sieve, wherein the pore size distribution of the SAPO-34 molecular sieve shows a relatively concentrated distribution characteristic of secondary mesopore channels, the pore size of the first-level mesopores is 2 to 6 nm, the most probable pore size is 4 to 5 nm, the pore size of the second-level mesopores is 6 to 50 nm, the most probable pore size is 12 to 20 nm, the proportion of the first-level mesopores is 70 to 80%, and the proportion of the second-level mesopores is 20 to 30%.

[0008] Furthermore, the total specific surface area of ​​the above-mentioned mesoporous SAPO-34 molecular sieve is 300 to 700 m 2 / g, and the mesopore specific surface area is 35~260m 2 / g.

[0009] A second aspect of the present invention provides a method for preparing a mesoporous SAPO-34 molecular sieve, comprising the following steps:

[0010] (A) mixing phosphoric acid, tetraethyl orthosilicate, aluminum isopropoxide, morpholine and water under contact conditions, mixing uniformly and then performing a crystallization reaction, followed by separation, washing and drying;

[0011] (B) subjecting the solid phase material obtained in step (A) to high temperature heat treatment;

[0012] (C) The solid phase material obtained in step (B) is mixed with phosphoric acid, ethyl orthosilicate, aluminum isopropoxide, morpholine, acid and water, mixed evenly and reacted, and then separated and dried to obtain SAPO-34 molecular sieve.

[0013] Furthermore, in the above-mentioned preparation method of mesoporous SAPO-34 molecular sieve, the amounts of various raw materials in step (A) need to satisfy a certain proportional relationship, and the raw material ratio can be a molar ratio. The specific molar ratio of phosphoric acid, ethyl orthosilicate, aluminum isopropoxide, water and morpholine is 0.6~2.1P: 0.17~1.2SiO2: A12O3: 35~220H2O: 0.9~2.1morpholine, preferably 0.7~2P: 0.2~1SiO2: A12O3: 40~200H2O: 1~2morpholine.

[0014] Furthermore, in the above-mentioned preparation method of mesoporous SAPO-34 molecular sieve, the crystallization reaction temperature in step (A) is 170-230°C, preferably 180-220°C; the reaction time is 20-100h, preferably 25-90h.

[0015] Furthermore, in the above-mentioned preparation method of mesoporous SAPO-34 molecular sieve, the separation in step (A) is liquid-solid separation, and any of the means commonly used in the industry for achieving liquid-solid two-phase separation can be used, such as filtration, which is generally performed multiple times.

[0016] Furthermore, in the above-mentioned preparation method of mesoporous SAPO-34 molecular sieve, the washing in step (A) is generally performed with deionized water, and is generally performed until the filtrate is neutral.

[0017] Furthermore, in the above-mentioned preparation method of mesoporous SAPO-34 molecular sieve, the drying temperature in step (A) is 100-150° C., and the drying time is 1-10 hours.

[0018] Furthermore, in the above-mentioned preparation method of mesoporous SAPO-34 molecular sieve, the high-temperature heat treatment temperature in step (B) is 600-800° C., preferably 650-750° C.; and the treatment time is 1-10 h, preferably 2-8 h.

[0019] Furthermore, in the above-mentioned preparation method of mesoporous SAPO-34 molecular sieve, the acid in step (C) is an organic acid, specifically at least one selected from citric acid, oxalic acid, formic acid, and acetic acid.

[0020] Furthermore, in the above-mentioned method for preparing mesoporous SAPO-34 molecular sieve, the mass ratio of the solid phase material obtained in step (B) to phosphoric acid in step (C) is 1:0.2 to 1:0.4.

[0021] Furthermore, in the above-mentioned method for preparing mesoporous SAPO-34 molecular sieve, the mass ratio of the solid phase material obtained in step (B) described in step (C) to aluminum isopropoxide is 1:0.1 to 1:0.2.

[0022] Furthermore, in the above-mentioned preparation method of mesoporous SAPO-34 molecular sieve, the mass ratio of the solid phase material obtained in step (B) described in step (C) to ethyl orthosilicate is 1:0.1 to 1:0.2.

[0023] Furthermore, in the above-mentioned method for preparing mesoporous SAPO-34 molecular sieve, the mass ratio of the solid phase material obtained in step (B) to morpholine in step (C) is 1:0.1 to 1:0.3.

[0024] Furthermore, in the above-mentioned method for preparing mesoporous SAPO-34 molecular sieve, the mass ratio of the solid phase material obtained in step (B) to the acid in step (C) is 1:0.3 to 1:0.6.

[0025] Furthermore, in the above-mentioned method for preparing mesoporous SAPO-34 molecular sieve, the mass ratio of the solid phase material obtained in step (B) to water in step (C) is 1:15 to 1:25.

[0026] Furthermore, in the above-mentioned method for preparing mesoporous SAPO-34 molecular sieve, the mixing described in step (C) 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 limited to 0.1 to 10 minutes, preferably 1 to 5 minutes. There are no specific restrictions or requirements on the order of adding the various materials.

[0027] Furthermore, in the above-mentioned method for preparing mesoporous SAPO-34 molecular sieve, the reaction temperature in step (C) is 130-170°C, preferably 160-190°C; the reaction time is generally limited to 0.5-12 hours, preferably 2-15 hours. The reaction process in step (C) is limited to being carried out in a pressure-resistant container.

[0028] Furthermore, in the above-mentioned preparation method of mesoporous SAPO-34 molecular sieve, the separation purpose in step (C) is to remove unreacted raw materials, which can be done by filtration, generally multiple filtrations.

[0029] Furthermore, in the above-mentioned preparation method of mesoporous SAPO-34 molecular sieve, the drying temperature in step (C) is 100-150° C., and the drying time is 1-10 hours.

[0030] The third aspect of the present invention provides a mesoporous SAPO-34 molecular sieve obtained by the above preparation method.

[0031] Furthermore, the pore size distribution of the SAPO-34 molecular sieve shows a relatively concentrated distribution characteristic of secondary mesopore channels. The pore size of the first-order mesopores is 2 to 6 nm, the most probable pore size is 4 to 5 nm, the pore size of the second-order mesopores is 6 to 50 nm, the most probable pore size is 12 to 20 nm, the proportion of the first-order mesopores is 70 to 80%, and the proportion of the second-order mesopores is 20 to 30%.

[0032] Furthermore, the total specific surface area of ​​the above-mentioned mesoporous SAPO-34 molecular sieve is 300 to 700 m 2 / g, and the mesopore specific surface area is 35~260m 2 / g.

[0033] The SAPO-34 molecular sieve provided by the present invention can be used in a variety of industries, generally in the chemical industry. Due to its excellent material transport ability, it is suitable for use as an acidic component of a catalyst and can also be used as an adsorption separation agent.

[0034] Compared with existing methods, the mesoporous SAPO-34 molecular sieve and its preparation method provided by the present invention have the following advantages:

[0035] 1. The present invention provides a SAPO-34 molecular sieve with a unique secondary mesoporous channel structure. Compared with traditional SAPO-34 molecular sieves, during adsorption or catalytic reactions, due to its excellent secondary mesoporous channel structure, it has a special screening effect on reactants.

[0036] 2. The present invention provides a method for efficiently preparing mesoporous SAPO-34 molecular sieves. First, a SAPO-34 molecular sieve precursor is synthesized and then subjected to high-temperature heat treatment. The high-temperature heat treatment process causes slight structural damage to the molecular sieve sample, resulting in slight structural defects on the molecular sieve, but does not affect the overall structure of the molecular sieve. The hydrothermal reaction is then continued, and a small amount of phosphoric acid, silicon source, aluminum source and template agent morpholine are added while acid is added in step C to ensure that raw materials such as phosphorus, silicon and aluminum are re-entered into the crystal skeleton of the molecular sieve during the formation of mesopores, and the molecular sieve crystal structure destroyed by the introduction of acid is repaired. The mesoporous SAPO-34 molecular sieve obtained by the preparation method of the present invention has the characteristics of high crystallinity, can obtain mesopores and keep the structure of the molecular sieve intact as much as possible. It is possible to avoid the destruction of the molecular sieve crystal structure when preparing mesoporous molecular sieves using methods such as hydrothermal treatment and acid treatment, thereby affecting the performance of the molecular sieve. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Figure 1 This is the pore size distribution diagram of the material obtained in Example 1. DETAILED DESCRIPTION

[0038] The technical solutions and effects of the present invention are further described below with reference to the following embodiments, but are not limited to the following embodiments.

[0039] In this paper, the crystal structure of the sample was characterized by X-ray diffractometer. A Rigaku D / max2500 X-ray diffractometer was used, equipped 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°~40°, a step size of 0.1°, and a scanning speed of 1° / min.

[0040] In this study, pore structure parameters such as specific surface area were measured using low-temperature nitrogen adsorption, using an ASAP2400 physical adsorption instrument from Micromeritics Instruments. Prior to measurement, the samples were treated at 300°C under vacuum for at least 4 hours. The total specific surface area was calculated using the BET isotherm equation, while the micropore and mesopore specific surface areas were calculated using the t-plot method. The pore size distribution was calculated using the BJH method.

[0041] Example 1

[0042] Dissolve 8.8g of phosphoric acid, 6.52g of morpholine, and 21.35g of aluminum isopropoxide in 85g of distilled water, then add 6.52g of tetraethyl orthosilicate and mix thoroughly. The mixture is then treated at 180°C for 36h. After the reaction, filter the solid sample several times and dry it in an oven at 110°C for 10h to obtain a solid. This solid is then treated in a high-temperature furnace at 700°C for 6h. Next, place 10g of the solid prepared in the previous step, along with 3.5g of phosphoric acid, 1.4g of tetraethyl orthosilicate, 1.2g of aluminum isopropoxide, 1.5g of morpholine, 4.5g of citric acid, and 200mL of distilled water in a clean container and stir thoroughly. The mixture is 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 3min. The mixture is then transferred to a pressure-resistant reactor and treated at 176°C for 8h. The resulting sample is then filtered several times and dried in an oven at 110°C for 12h. The resulting sample is designated C1. The obtained sample was tested by low-temperature nitrogen adsorption and calculated using the BJH method. It was found that the mesopore distribution of the sample consists of two mesopores. The most probable pore diameter of the first mesopore is 5nm, and its proportion is 77%; the most probable pore diameter of the second mesopore is 12nm, and its proportion is 23%.

[0043] Example 2

[0044] Dissolve 10.88g of phosphoric acid, 4.55g of morpholine, and 22.7g of aluminum isopropoxide in 200g of distilled water, then add 11.57g of tetraethyl orthosilicate and mix thoroughly. The mixture is then treated at 220°C for 25h. After the reaction, filter the solid sample several times and dry it in an oven at 110°C for 10h to obtain a solid. This solid is then treated in a high-temperature furnace at 650°C for 8h. Next, place 10g of the solid prepared in the previous step, 2g of phosphoric acid, 1g of tetraethyl orthosilicate, 1g of aluminum isopropoxide, 1g of morpholine, 3g of citric acid, and 150mL of distilled water in a clean container and stir thoroughly. The mixture is 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 1min. The mixture is then transferred to a pressure-resistant reactor and treated at 160°C for 15h. The resulting sample is then filtered several times and dried in an oven at 110°C for 12h. The resulting sample is designated C2. The obtained sample was tested by low-temperature nitrogen adsorption and calculated using the BJH method. It was found that the mesopore distribution of the sample consists of two mesopores. The most probable pore diameter of the first mesopore is 4nm, and its proportion is 71%; the most probable pore diameter of the second mesopore is 17nm, and its proportion is 29%.

[0045] Example 3

[0046] Dissolve 3.81g of phosphoric acid, 9.1g of morpholine, and 22.7g of aluminum isopropoxide in 40g of distilled water, then add 2.31g of tetraethyl orthosilicate and mix thoroughly. The mixture is then treated at 180°C for 90h. After the reaction, the solid sample is filtered multiple times and then dried in an oven at 110°C for 10h to obtain a solid. The solid is then treated in a high-temperature furnace at 750°C for 2h. Next, 10g of the solid prepared in the previous step, 4g of phosphoric acid, 2g of tetraethyl orthosilicate, 2g of aluminum isopropoxide, 3g of morpholine, 6g of citric acid, and 250mL of distilled water are placed in a clean container and stirred thoroughly. The mixture is 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 5 minutes. The mixture is then transferred to a pressure-resistant reactor and treated at 190°C for 2h. The resulting sample is then filtered multiple times and dried in an oven at 110°C for 12h. The resulting sample is designated C3. The obtained sample was subjected to low-temperature nitrogen adsorption test and calculated using the BJH method. It was found that the mesopore distribution of the sample consists of two mesopores. The most probable pore diameter of the first mesopore is 4.5nm, and its proportion is 78%; the most probable pore diameter of the second mesopore is 19nm, and its proportion is 22%.

[0047] Example 4

[0048] Dissolve 7.56g of phosphoric acid, 8.3g of morpholine, and 19.55g of aluminum isopropoxide in 75g of distilled water, then add 9.05g of tetraethyl orthosilicate and mix thoroughly. The mixture is then treated at 215°C for 55h. After the reaction, filter the solid sample several times and dry it in an oven at 115°C for 10h to obtain a solid. This solid is then treated in a high-temperature furnace at 670°C for 3h. Next, place 10g of the solid prepared in the previous step, along with 2.5g of phosphoric acid, 1.3g of tetraethyl orthosilicate, 1.2g of aluminum isopropoxide, 2.3g of morpholine, 5.2g of oxalic acid, and 210mL of distilled water in a clean container and stir thoroughly. The mixture is 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 3min. The mixture is then transferred to a pressure-resistant reactor and treated at 185°C for 3.5h. The resulting sample is then filtered several times and dried in an oven at 110°C for 12h. 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 mesopore distribution of the sample consists of two mesopores. The most probable pore diameter of the first mesopore is 4nm, and its proportion is 71%; the most probable pore diameter of the second mesopore is 15nm, and its proportion is 29%.

[0049] Example 5

[0050] Dissolve 4.56g of phosphoric acid, 5.5g of morpholine, and 17.01g of aluminum isopropoxide in 88g of distilled water, then add 7.89g of tetraethyl orthosilicate and mix thoroughly. The mixture is then treated at 190°C for 36h. After the reaction, filter the solid sample several times and dry it in an oven at 115°C for 10h to obtain a solid. This solid is then treated in a high-temperature furnace at 690°C for 6h. Next, place 10g of the solid prepared in the previous step, 3.3g of phosphoric acid, 1.5g of tetraethyl orthosilicate, 1.6g of aluminum isopropoxide, 2.1g of morpholine, 5.8g of acetic acid, and 200mL of distilled water in a clean container and stir thoroughly. The mixture is 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 3min. The mixture is then transferred to a pressure-resistant reactor and treated at 180°C for 5h. The resulting sample is then filtered several times and dried in an oven at 110°C for 12h. The resulting sample is designated C5. The obtained sample was subjected to low-temperature nitrogen adsorption test and calculated using the BJH method. It was found that the mesopore distribution of the sample consists of two mesopores. The most probable pore diameter of the first mesopore is 4.5nm, and its proportion is 75%; the most probable pore diameter of the second mesopore is 17nm, and its proportion is 25%.

[0051] Comparative Example 1

[0052] Dissolve 8.8g of phosphoric acid, 6.52g of morpholine, and 21.35g of aluminum isopropoxide in 85g of distilled water. Add 6.52g of tetraethyl orthosilicate and mix thoroughly. The mixture is then treated at 180°C for 36 hours. After the reaction, the solid sample is filtered several times and then dried in an oven at 110°C for 10 hours to obtain a solid. The solid is then treated in a high-temperature furnace at 700°C for 6 hours. Then, 10 g of the solid material prepared in the previous step, 8.8 g of phosphoric acid, 6.52 g of morpholine, 21.35 g of aluminum isopropoxide, 6.52 g of ethyl orthosilicate, 4.5 g of citric acid, and 200 mL of distilled water were placed in a clean container and stirred evenly. 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 3 minutes. The mixture was then transferred to a pressure-resistant reactor and treated at 176°C for 8 hours. The resulting sample was then filtered multiple times and dried in an oven at 110°C for 12 hours. The resulting sample was designated C6. The resulting sample was a SAPO-34 molecular sieve, but lacked a distinct mesoporous structure, indicating a conventional microporous molecular sieve.

[0053] Comparative Example 2

[0054] Dissolve 10.88g of phosphoric acid, 4.55g of morpholine, and 22.7g of aluminum isopropoxide in 200g of distilled water, then add 11.57g of tetraethyl orthosilicate and mix thoroughly. Then, treat at 220°C for 25h. After the reaction, filter the solid sample several times and dry it in an oven at 110°C for 10h to obtain a solid. Next, place 10g of the solid prepared in the previous step, 2g of phosphoric acid, 1g of tetraethyl orthosilicate, 1g of aluminum isopropoxide, 1g of morpholine, 3g of citric acid, and 150mL of distilled water in a clean container and stir thoroughly. Then, place the container in an ultrasonic cleaner at a frequency of 10MHz and a power of 100W / L based on the volume of the solution for 1min. Then, transfer the container to a pressure-resistant reactor and treat at 160°C for 15h. Filter the resulting sample several times and dry it in an oven at 110°C for 12h. The resulting sample is designated C7. The resulting sample was subjected to low-temperature nitrogen adsorption testing and calculated using the BJH method. The mesopore distribution of this sample consists of two mesopores. The first mesopore has a most probable pore size of 6 nm and accounts for 67% of the total pore size. The second mesopore has a most probable pore size of 15 nm and accounts for 33% of the total pore size. Compared to Comparative Example 2, this sample has a lower mesopore area and lower crystallinity, indicating that this method has some drawbacks compared to the present invention.

[0055] Comparative Example 3

[0056] Dissolve 3.81g of phosphoric acid, 9.1g of morpholine, and 22.7g of aluminum isopropoxide in 40g of distilled water, then add 2.31g of tetraethyl orthosilicate and mix thoroughly. The mixture is then treated at 180°C for 90h. After the reaction, the solid sample is filtered multiple times and then dried in an oven at 110°C for 10h to obtain a solid. The solid is then treated in a high-temperature furnace at 750°C for 2h. Next, 10g of the solid prepared in the previous step, 6g of citric acid, and 250mL of distilled water are placed in a clean container and stirred thoroughly. The mixture is then ultrasonically cleaned at a frequency of 10MHz and a power of 100W / L based on the volume of the solution for 5min. The mixture is then transferred to a pressure-resistant reactor and treated at 190°C for 2h. The resulting sample is then filtered multiple times and dried in an oven at 110°C for 12h. The resulting sample is designated C8. 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 6 nm. Compared with Comparative Example 3, the surface area, mesopore area, and crystallinity were greatly reduced, indicating that this method has great defects compared with the present invention.

[0057] Table 1 Pore structure properties of samples of Examples and Comparative Examples

[0058]

[0059] Note: The crystallinity of the SAPO-34 molecular sieve in Example 1 is taken as a reference and is set to 100%. The crystallinity of all samples is obtained by comparing with the crystallinity of the SAPO-34 molecular sieve in Example 1.

[0060] By comparing the examples and comparative examples, it can be seen that the method of the present invention can not only produce perfect mesoporous channels, but also maintain a high degree of crystallinity.

Claims

1. A mesoporous SAPO-34 molecular sieve, wherein the pore size distribution of the SAPO-34 molecular sieve shows a relatively concentrated distribution characteristic of secondary mesopore channels, the pore size of the first-order mesopores is 2-6 nm, the most probable pore size is 4-5 nm, the pore size of the second-order mesopores is 6-50 nm, the most probable pore size is 12-20 nm, the proportion of the first-order mesopores is 70-80%; and the proportion of the second-order mesopores is 20-30%.

2. The mesoporous SAPO-34 molecular sieve according to claim 1, characterized in that: The total specific surface area of ​​SAPO-34 molecular sieve is 300~700m 2 / g, and the mesopore specific surface area is 35~260m 2 / g.

3. A method for preparing the mesoporous SAPO-34 molecular sieve according to claim 1 or 2, comprising the following steps: (A) mixing phosphoric acid, tetraethyl orthosilicate, aluminum isopropoxide, morpholine and water under contact conditions, mixing uniformly and then performing a crystallization reaction, followed by separation, washing and drying; (B) subjecting the solid phase material obtained in step (A) to high temperature heat treatment; (C) mixing the solid phase material obtained in step (B) with phosphoric acid, ethyl orthosilicate, aluminum isopropoxide, morpholine, acid and water, mixing well and reacting, and then separating and drying to obtain SAPO-34 molecular sieve; The acid in step (C) is an organic acid; The mass ratio of the solid phase material obtained in step (B) to phosphoric acid in step (C) is 1:0.2 to 1:0.4; the mass ratio of the solid phase material obtained in step (B) to aluminum isopropoxide is 1:0.1 to 1:0.2; the mass ratio of the solid phase material obtained in step (B) to ethyl orthosilicate is 1:0.1 to 1:0.2; and the mass ratio of the solid phase material obtained in step (B) to morpholine in step (C) is 1:0.1 to 1:0.

3.

4. The method for preparing the mesoporous SAPO-34 molecular sieve according to claim 3, characterized in that: The molar ratio of phosphoric acid, tetraethyl orthosilicate, aluminum isopropoxide, water and morpholine in step (A) is 0.6-2.1P:0.17-1.2SiO2:A12O3:35-220H2O:0.9-2.1morpholine.

5. The method for preparing the mesoporous SAPO-34 molecular sieve according to claim 3, characterized in that: The molar ratio of phosphoric acid, tetraethyl orthosilicate, aluminum isopropoxide, water and morpholine in step (A) is 0.7-2P:0.2-1SiO2:A12O3:40-200H2O:1-2morpholine.

6. The method for preparing the mesoporous SAPO-34 molecular sieve according to claim 3, characterized in that: The crystallization reaction temperature in step (A) is 170-230° C., and the reaction time is 20-100 hours.

7. The method for preparing the mesoporous SAPO-34 molecular sieve according to claim 3, characterized in that: The crystallization reaction temperature in step (A) is 180-220° C., and the reaction time is 25-90 hours.

8. The method for preparing the mesoporous SAPO-34 molecular sieve according to claim 3, characterized in that: The drying temperature in step (A) is 100-150° C., and the drying time is 1-10 hours.

9. The method for preparing the mesoporous SAPO-34 molecular sieve according to claim 3, characterized in that: The high temperature heat treatment temperature in step (B) is 600-800° C. and the treatment time is 1-10 hours.

10. The method for preparing the mesoporous SAPO-34 molecular sieve according to claim 3, characterized in that: The high temperature heat treatment temperature in step (B) is 650-750° C. and the treatment time is 2-8 hours.

11. The method for preparing the mesoporous SAPO-34 molecular sieve according to claim 3, characterized in that: The acid in step (C) is selected from at least one of citric acid, oxalic acid, formic acid and acetic acid.

12. The method for preparing the mesoporous SAPO-34 molecular sieve according to claim 3, characterized in that: The mass ratio of the solid phase material obtained in step (B) to the acid in step (C) is 1:0.3 to 1:0.

6.

13. The method for preparing the mesoporous SAPO-34 molecular sieve according to claim 3, characterized in that: The mass ratio of the solid phase material obtained in step (B) to water in step (C) is 1:15 to 1:

25.

14. The method for preparing the mesoporous SAPO-34 molecular sieve according to claim 3, characterized in that: The mixing in step (C) is carried out under ultrasonic conditions, with an ultrasonic frequency of 15 KHz to 10 MHz and a power limited to 20 to 100 W / L based on the volume of the solution.

15. The method for preparing the mesoporous SAPO-34 molecular sieve according to claim 3, characterized in that: The reaction temperature in step (C) is 130-170° C., and the reaction time is 0.5-12 h.

16. The method for preparing the mesoporous SAPO-34 molecular sieve according to claim 3, characterized in that: The reaction temperature in step (C) is 160-190° C., and the reaction time is 2-15 hours.

17. The method for preparing the mesoporous SAPO-34 molecular sieve according to claim 3, characterized in that: The drying temperature in step (C) is 100-150° C., and the drying time is 1-10 hours.

18. A mesoporous SAPO-34 molecular sieve obtained by the preparation method according to any one of claims 3 to 17.

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