Micropore-mesopore-macropore SAPO-5 molecular sieve, and preparation method and application thereof

Abstract

The present application relates to the technical field of molecular sieve preparation, and particularly relates to a micropore-mesopore-macropore SAPO-5 molecular sieve, a preparation method and application thereof, which comprises the following steps: uniformly stirring an aluminum source, a silicon source, a phosphorus source, a structure directing agent and water to obtain a silicon-aluminum-phosphorus gel; placing the silicon-aluminum-phosphorus gel in a reaction kettle and hydrothermally crystallizing in a dynamic oven; after centrifugation, drying and calcination treatment of the obtained product, a micropore-mesopore polycrystalline aggregate SAPO-5 molecular sieve is obtained; adding the micropore-mesopore polycrystalline aggregate SAPO-5 molecular sieve into a tetrapropylammonium hydroxide solution, uniformly stirring and then placing in a reaction kettle for alkali treatment; after centrifugation, drying and calcination treatment of the obtained product, a micropore-mesopore-macropore SAPO-5 molecular sieve is obtained. The SAPO-5 molecular sieve of the present application has a micropore-mesopore-macropore structure with a specific morphology, and solves the problems of molecular sieve framework collapse, destruction of zeolite crystallinity and easy plugging of micropore channels of zeolite caused by alkali treatment in the prior art.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of molecular sieve preparation, in particular to a microporous-mesoporous-macroporous SAPO-5 molecular sieve and a preparation method and application thereof. BACKGROUND

[0002] SAPO-5 molecular sieve is one of the important members in the SAPO series, and has an AFI topological structure. The SAPO-5 is a microporous molecular sieve with a one-dimensional pore structure (about 0.73 nm) of a twelve-membered ring as a basic unit, which is formed by SiO4, AlO4 and PO4 tetrahedrons connected to each other through oxygen bridges. Due to its unique microporous structure, high thermal stability, hydrothermal stability, chemical stability and strong acidity, the SAPO-5 has a wide application in isomerization reaction, alkylation reaction, benzylation reaction, MTO conversion reaction and other fields.

[0003] However, the single microporous channel of the traditional SAPO-5 zeolite seriously limits the intracrystalline mass transfer. When large molecule reactants are involved, the zeolite catalyst will encounter serious diffusion limitation, thus showing low catalytic activity, leading to secondary reaction, coking, covering of active sites and plugging of the pore channel, thus causing serious deactivation of the catalyst, which greatly restricts the practical application of the zeolite material.

[0004] At present, the synthesis methods of the hierarchical pore SAPO-5 mainly include a hard template method, a soft template method and a post-treatment method. The soft and hard template methods usually need a carefully designed mesoporous template agent to guide the formation of the mesoporous structure. Although the hierarchical pore zeolite synthesized by the hard template method has high crystallinity, the type and shape of the hard template are required to be high, and the connectivity of the pore channel is poor after the hard template is removed, which has certain limitations for the industrial application. The soft template method is to synthesize the zeolite by using a hydrophobic alkyl group as a template agent, and the synthesis time is long, the cost is high and it is difficult to control. Therefore, no matter which method is used, the complicated synthesis procedure, high cost and large time consumption seriously limit the industrial application.

[0005] The post-treatment (acid or alkali) of the synthesized molecular sieve for post-modification to prepare the hierarchical pore zeolite is the most commonly used method in the industry at present. However, the conventional acid or alkali treatment of the molecular sieve is easy to cause the collapse of the framework structure, reduce the crystallinity of the zeolite and the silicon and aluminum atoms removed from the framework have randomness, thus leading to poor repeatability of the prepared hierarchical pore zeolite. In addition, the residual silicon and aluminum fragments are easy to plug the microporous channel of the zeolite, thus reducing the accessibility of the active sites to the reactants.

[0006] Therefore, it is an urgent technical problem for those skilled in the art to seek a post-treatment method for preparing SAPO-5 molecular sieves with micro-mesopore-macropore multi-level pores, which is simple and easy to operate, has good repeatability, and can maintain the physical and chemical properties of the original zeolite. SUMMARY

[0007] The present application aims to provide a micro-mesopore-macropore SAPO-5 molecular sieve, a preparation method and application thereof, which has a micro-mesopore-macropore structure with a specific morphology, and solves the key problems in the prior art, such as the collapse of the molecular sieve framework caused by alkali treatment, the destruction of the crystallinity of the zeolite, and the easy plugging of the micropore channels of the zeolite by residual silicon-aluminum fragments.

[0008] In a first aspect, the present application provides a preparation method of a micro-mesopore-macropore SAPO-5 molecular sieve, comprising the following steps:

[0009] S1, uniformly stirring an aluminum source, a silicon source, a phosphorus source, a structure directing agent and water to obtain a silicon-aluminum-phosphorus gel;

[0010] S2, placing the silicon-aluminum-phosphorus gel in a reaction kettle and hydrothermally crystallizing it in a dynamic oven, and after centrifugation, drying and calcination treatment of the obtained product, a micro-mesopore polycrystalline aggregate SAPO-5 molecular sieve is obtained;

[0011] S3, adding the micro-mesopore polycrystalline aggregate SAPO-5 molecular sieve to a tetrapropylammonium hydroxide solution, uniformly stirring and then placing it in a reaction kettle for alkali treatment, and after centrifugation, drying and calcination treatment of the obtained product, a micro-mesopore-macropore SAPO-5 molecular sieve is obtained.

[0012] Firstly, the present application uniformly stirs an aluminum source, a silicon source, a phosphorus source, a structure directing agent and water to obtain a silicon-aluminum-phosphorus gel, and then places the silicon-aluminum-phosphorus gel in a reaction kettle and hydrothermally crystallizes it in a dynamic oven, which can effectively avoid the generation of impurities during the static hydrothermal crystallization process, thereby improving the crystallinity of the molecular sieve. After centrifugation, drying and calcination treatment of the crystallized product, the structure directing agent can be further removed, and a micro-mesopore polycrystalline aggregate SAPO-5 molecular sieve is obtained. Finally, the micro-mesopore polycrystalline aggregate SAPO-5 molecular sieve is added to a tetrapropylammonium hydroxide solution for alkali treatment, and the tetrapropylammonium hydroxide can act as an etchant to extract the framework elements from the specific area (the center of the petal structure) of the synthesized micro-mesopore SAPO-5, forming a uniform macropore structure. At the same time, the treated SAPO-5 molecular sieve can still maintain the original micropore and mesopore structures and the original crystallinity.

[0013] The step S1 specifically comprises: dissolving an aluminum source and a structure-directing agent in distilled water, stirring until clear, sequentially adding a silicon source and a phosphorus source, stirring uniformly, and obtaining a silicon-aluminum-phosphorus gel; wherein the molar ratio of Al2O3, SiO2, P2O5, SDA and H2O in the silicon-aluminum-phosphorus gel is (0.2-1.8):(0.3-0.9):(0.8-5.2):(1.2-10.5):(50-560).

[0014] As the preferred technical solution, in step S1, the aluminum source used in the application includes any one of aluminum isopropoxide, pseudo-boehmite, aluminum sec-butoxide and aluminum hydroxide; the silicon source includes any one of tetraethyl orthosilicate, fumed silica and white carbon black; the structure-directing agent includes any one of tetraethylammonium hydroxide, tetrapropylammonium hydroxide, ethylenediamine, triethylamine and morpholine; and the phosphorus source includes any one of phosphoric acid, ammonium monohydrogen phosphate and ammonium dihydrogen phosphate.

[0015] As the preferred technical solution, in step S2, when the hydrothermal crystallization is performed, the rotation speed of the dynamic oven is controlled to be 20-60 rpm / min, the temperature is controlled to be 140-200 DEG C, and the time is controlled to be 6-48 h.

[0016] The dynamic hydrothermal crystallization can fully stir the Si, Al and P elements in the gel precursor solution, and a uniform flower cluster-shaped zeolite morphology can be obtained. Most importantly, compared with the traditional hydrothermal crystallization, this method can effectively avoid the generation of impurities under the same formula.

[0017] After the dynamic hydrothermal crystallization, the product needs to be further dried and calcined, wherein the drying process is mainly to remove the main water of the zeolite, and the calcination is mainly to remove the micropore template agent filled in the micropore of the zeolite; preferably, the temperature is controlled to be 80-120 DEG C during the drying process, and the time is controlled to be 12-20 h; and preferably, the temperature is controlled to be 500-650 DEG C during the calcination, and the time is controlled to be 2-10 h.

[0018] Further, the micropore-mesoporous polycrystalline aggregate SAPO-5 molecular sieve is added to the tetrapropylammonium hydroxide solution for alkaline treatment, and the tetrapropylammonium hydroxide can be used as an etching agent to extract the skeleton elements of the specific area (the center of the petal structure) of the synthesized micropore-mesoporous SAPO-5, and form a uniform macroporous structure. Specifically, the volume of the tetrapropylammonium hydroxide solution corresponding to each g of the micropore-mesoporous polycrystalline aggregate SAPO-5 molecular sieve is 2.5-10 mL, and the mass fraction of the tetrapropylammonium hydroxide solution is 20-30%.

[0019] As the preferred technical solution, in step S3, when the alkaline treatment is performed, the temperature is controlled to be 120-180 DEG C, and the time is controlled to be 6-24 h.

[0020] At this treatment temperature, tetrapropyl ammonium hydroxide as a mild base treatment agent can achieve the removal of specific area elements of the zeolite, and the principle is that: the growth process of SAPO-5 is pre-crystallization nucleation, and then directional growth around the nucleus, and finally form flower-like SAPO-5 zeolite; in the initial stage of crystallization, the solution contains rich silicon species, so the crystal nucleus is in a silicon-rich state. With the extension of the crystallization time, the Si species in the solution is consumed, and the growing petal-shaped zeolite crystal is in a low-silicon state, so the synthesized zeolite has the characteristics of high-silicon inside (nucleus) and low-silicon outside (petals). When tetrapropyl ammonium hydroxide is used as a weak base to treat the zeolite, the framework species of the zeolite nucleus can be effectively removed. At the same time, due to the low-silicon characteristics of the petal-shaped zeolite, it has high alkali resistance, and can still maintain the original crystal structure during alkali treatment.

[0021] After the alkali treatment, the molecular sieve is further dried and calcined, wherein the temperature is controlled at 90-110 DEG C during drying, and the time is 18-24h; the temperature is controlled at 500-650 DEG C during calcination, and the time is 3-18h.

[0022] In the second aspect, the micropore-mesopore-macropore SAPO-5 molecular sieve prepared by the above method also belongs to the protection scope of the present application, and specifically, the mesopore size of the micropore-mesopore-macropore SAPO-5 molecular sieve is 2-40nm, and the macropore size is 0.1-3um.

[0023] In the third aspect, the application of the micropore-mesopore-macropore SAPO-5 molecular sieve prepared by the present application, which has a mesopore size of 2-40nm and a macropore size of 0.1-3um, in the cracking reaction of triisopropylbenzene also belongs to the protection scope of the present application.

[0024] Studies have shown that when the micropore-mesopore-macropore SAPO-5 molecular sieve of the present application is used as a catalyst in the cracking reaction of triisopropylbenzene, the conversion rate of triisopropylbenzene can be kept high (98.08%) in the initial reaction of 1h, and the conversion rate decreases to 88.41% after 8h of reaction, and it has high selectivity to the deep cracking products isopropylbenzene and benzene, which are 35.41% and 14.16% respectively.

[0025] The preparation method of the micropore-mesopore-macropore SAPO-5 molecular sieve has at least the following beneficial effects:

[0026] 1. In the preparation method of the micropore-mesopore-macropore SAPO-5 molecular sieve of the present application, first, the aluminum source, the silicon source, the structure directing agent, water and the phosphorus source are stirred uniformly to prepare a silicon-aluminum-phosphorus gel; then the silicon-aluminum-phosphorus gel is placed in a reaction kettle and hydrothermally crystallized in a dynamic oven, and the dynamic hydrothermal crystallization can effectively avoid the generation of impurities in the process of static hydrothermal crystallization, thereby improving the crystallinity of the molecular sieve; the hydrothermal crystallization product is subjected to centrifugation, drying and calcination treatment, and the structure directing agent can be further removed to obtain a micropore-mesopore polycrystalline aggregate SAPO-5 molecular sieve; finally, the micropore-mesopore polycrystalline aggregate SAPO-5 molecular sieve is added to a tetrapropylammonium hydroxide solution for alkaline treatment, and the tetrapropylammonium hydroxide can be used as an etching agent to extract the skeleton elements of the specific area (the center of the petal structure) of the synthesized micropore-mesopore SAPO-5 to form a uniform macropore structure, and at the same time, the treated SAPO-5 molecular sieve can still maintain the original micropore and mesopore structure and the original crystallinity. Therefore, the SAPO-5 molecular sieve prepared by the present application has a specific micropore-mesopore-macropore structure, which solves the key problems in the prior art, such as the collapse of the molecular sieve skeleton caused by alkaline treatment, the destruction of the crystallinity of the zeolite, and the easy plugging of the micropore channels of the zeolite by the residual silicon-aluminum fragments.

[0027] 2. The preparation conditions of the present application are relatively mild, the process is simple, and industrial application can be realized. Compared with conventional microporous SAPO-5, the micropore-mesopore-macropore SAPO-5 molecular sieve prepared by the present application has a significantly improved catalytic life in the cracking reaction of triisopropylbenzene, and the conversion rate of triisopropylbenzene and the selectivity of the deep cracking products IPB and Ben are also significantly improved, which plays a certain guiding significance in solving the problem of heavy oil. BRIEF DESCRIPTION OF DRAWINGS

[0028] In order to more clearly illustrate the specific embodiments of the present application or the technical solutions in the prior art, the drawings needed in the following specific embodiments or prior art description will be briefly introduced. Obviously, the drawings in the following description are some embodiments of the present application, and other drawings can also be obtained by those skilled in the art without creative labor.

[0029] Figure 1 The XRD comparison chart of the micropore-mesopore polycrystalline aggregate SAPO-5 molecular sieve, the micropore-mesopore-macropore SAPO-5 molecular sieve and the comparative example 1 in the present application example 1;

[0030] Figure 2 The SEM chart of the micropore SAPO-5 molecular sieve of the present application comparative example 1;

[0031] Figure 3SEM image of the microporous-mesoporous SAPO-5 molecular sieve of Example 1 of the present application;

[0032] Figure 4 SEM image of the microporous-mesoporous SAPO-5 molecular sieve of Example 1 of the present application after being crushed by extrusion (10 MPa);

[0033] Figure 5 SEM image of the microporous-mesoporous SAPO-5 molecular sieve of Example 1 of the present application;

[0034] Figure 6 SEM image of the microporous-mesoporous SAPO-5 molecular sieve of Example 1 of the present application after being crushed by extrusion (10 MPa);

[0035] Figure 7 N2adsorption-desorption isotherm and corresponding pore size distribution of the microporous-mesoporous SAPO-5 molecular sieve and the microporous-mesoporous SAPO-5 molecular sieve of Example 1 of the present application;

[0036] Figure 8 Pore size distribution of the microporous-mesoporous SAPO-5 molecular sieve of Example 1 of the present application by mercury intrusion porosimetry. DETAILED DESCRIPTION

[0037] It should be noted that the following detailed description is merely exemplary in nature and is intended to provide further description of the application. Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs.

[0038] It is also important to note that the terms "including", "comprising", and / or "having" as used herein are specifically intended to be open-ended and also to mean including, but not limited to. As used herein, the singular forms "a", "an" and / or "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms "comprises" and / or "comprising", when used in this specification, specify the presence of stated features, steps, operations, elements, and / or components, but do not preclude the presence or addition of one or more other features, steps, operations, elements, components, and / or groups thereof.

[0039] The technical solutions of the present application will be described clearly and completely in combination with the embodiments. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor are within the protection scope of the present application.

[0040] Example 1

[0041] S11, accurately weigh 7.38 g of aluminum isopropoxide and dissolve it in a solution of 22.5 mL of distilled water and 30 mL of tetrapropylammonium hydroxide (25 wt.%), stir until completely dissolved, then sequentially add 3.6 mL of tetraethyl orthosilicate and 3.2 mL of phosphoric acid, mix well to obtain a silicon-aluminum-phosphorus gel;

[0042] S12, move the silicon-aluminum-phosphorus gel into a 100 mL stainless steel reaction kettle, then put it into a dynamic oven (rotation speed 30 r / min) for hydrothermal crystallization at 160°C for 24 h, wash the crystallized sample to neutral, dry at 80°C overnight, and calcine at 500°C for 10 h to obtain microporous-mesoporous polycrystalline aggregates SAPO-5 molecular sieve, denoted as Example 1a;

[0043] S13, add the microporous-mesoporous polycrystalline aggregates SAPO-5 molecular sieve to a solution of tetrapropylammonium hydroxide (25 wt.%), with a solid / liquid mass ratio of 0.4, stir well, then place it in a reaction kettle for alkali treatment, with a treatment temperature of 90°C and a treatment time of 5 h, centrifuge the obtained product, dry overnight to obtain a white solid powder, then calcine at 550°C for 6 h to obtain microporous-mesoporous-macroporous SAPO-5 molecular sieve, denoted as Example 1b.

[0044] Example 2

[0045] S21, accurately weigh 6.37 g of aluminum isopropoxide and dissolve it in a mixture of 18 mL of distilled water and 4.52 g of ethylenediamine, stir until completely dissolved, then sequentially add 1.87 g of silica sol (30 wt.%), 2.8 mL of phosphoric acid, mix well to obtain a silicon-aluminum-phosphorus gel;

[0046] S22, move the silicon-aluminum-phosphorus gel into a 100 mL stainless steel reaction kettle, then put it into a dynamic oven (rotation speed 40 r / min) for hydrothermal crystallization at 170°C for 24 h, wash the crystallized sample to neutral, dry at 95°C overnight, and calcine at 550°C for 6 h to obtain microporous-mesoporous polycrystalline aggregates SAPO-5 molecular sieve;

[0047] S23, add the microporous-mesoporous polycrystalline aggregates SAPO-5 molecular sieve to a solution of tetrapropylammonium hydroxide (25 wt.%), with a solid / liquid mass ratio of 0.3, stir well, then place it in a reaction kettle for alkali treatment, with a treatment temperature of 120°C and a treatment time of 2 h, centrifuge the obtained product, dry overnight to obtain a white solid powder, then calcine at 550°C for 8 h to obtain microporous-mesoporous-macroporous SAPO-5 molecular sieve.

[0048] Example 3

[0049] S31, accurately weigh 7.20 aluminum sec-butylate into a mixture of 10 mL distilled water and 3.78 g morpholine, stir until completely dissolved, then sequentially add 2.20 g silica sol (30 wt.%), 2.8 mL phosphoric acid, mix well to obtain a silicon-aluminum-phosphorus gel;

[0050] S32, move the silicon-aluminum-phosphorus gel into a 100 mL stainless steel reactor, then put it into a dynamic oven (rotation speed 45 rpm) for hydrothermal crystallization at 160°C for 48 h, wash the crystallized sample to neutral, dry at 110°C overnight, and calcine at 550°C for 8 h to obtain microporous-mesoporous polycrystalline aggregate SAPO-5 molecular sieve;

[0051] S33, add the microporous-mesoporous polycrystalline aggregate SAPO-5 molecular sieve to a tetrapropylammonium hydroxide (25 wt.%) solution (solid / liquid mass ratio 0.3), stir well, then place it in a reactor for alkali treatment, the treatment temperature is 110°C, and the time is 4 h, the obtained product is centrifuged, dried overnight to obtain a white solid powder; then calcine at 550°C for 12 h to obtain microporous-mesoporous-macroporous SAPO-5 molecular sieve.

[0052] Example 4

[0053] S41, accurately weigh 2.10 g pseudoboehmite into a mixture of 10 mL distilled water and 3.50 triethylamine, stir until completely dissolved, then sequentially add 1.7 mL tetraethyl orthosilicate, 3.67 g ammonium dihydrogen phosphate, mix well to obtain a silicon-aluminum-phosphorus gel;

[0054] S42, place the silicon-aluminum-phosphorus gel in a 100 mL stainless steel reactor, then put it into a dynamic oven (rotation speed 55 rpm) for hydrothermal crystallization at 160°C for 36 h, wash the crystallized sample to neutral, dry at 100°C overnight, and calcine at 650°C for 4 h to obtain microporous-mesoporous polycrystalline aggregate SAPO-5 molecular sieve;

[0055] S43, add the microporous-mesoporous polycrystalline aggregate SAPO-5 molecular sieve to a tetrapropylammonium hydroxide (25 wt.%) solution (solid / liquid mass ratio 0.20), stir well, then place it in a reactor for alkali treatment, the treatment temperature is 100°C, and the time is 4 h, the obtained product is centrifuged, dried overnight to obtain a white solid powder; then calcine at 550°C for 6 h to obtain microporous-mesoporous-macroporous SAPO-5 molecular sieve.

[0056] Example 5

[0057] S51, accurately weigh 2.10 g of pseudo-boehmite and dissolve it in a mixture of 10 mL of distilled water and 3.50 mL of triethylamine, stir until completely dissolved, then sequentially add 1.6 mL of tetraethyl orthosilicate and 3.45 g of monobasic ammonium phosphate, mix well to obtain a silicon-aluminum-phosphorus gel;

[0058] S52, move the silicon-aluminum-phosphorus gel into a 100 mL volume stainless steel reaction kettle, then place it in a dynamic oven (rotation speed 50 revolutions / minute) for hydrothermal crystallization at 160°C for 36 h, wash the crystallized sample to neutral, dry at 100°C overnight, and calcine at 600°C for 8 h to obtain microporous-mesoporous polycrystalline aggregate SAPO-5 molecular sieve;

[0059] S53, add the microporous-mesoporous polycrystalline aggregate SAPO-5 molecular sieve to a tetrapropylammonium hydroxide (25 wt.%) solution (solid / liquid mass ratio 0.10), stir well, then place it in a reaction kettle for alkali treatment, treatment temperature 100°C, time 4 h, the obtained product is centrifuged, dried overnight to obtain a white solid powder; then calcine at 550°C for 4 h to obtain microporous-mesoporous-macroporous SAPO-5 molecular sieve.

[0060] Example 6

[0061] S61, accurately weigh 6.59 g of aluminum isopropoxide and dissolve it in a solution of 18 mL of distilled water and 25 mL of tetrapropylammonium hydroxide (25 wt.%), stir until completely dissolved, then sequentially add 3.6 mL of tetraethyl orthosilicate and 3.2 mL of phosphoric acid, mix well to obtain a silicon-aluminum-phosphorus gel;

[0062] S62, move the silicon-aluminum-phosphorus gel into a 100 mL volume stainless steel reaction kettle, then place it in a dynamic oven (rotation speed 30 revolutions / minute) for hydrothermal crystallization at 150°C for 48 h, wash the crystallized sample to neutral, dry at 90°C overnight, and calcine at 500°C for 10 h to obtain microporous-mesoporous polycrystalline aggregate SAPO-5 molecular sieve;

[0063] S63, add the microporous-mesoporous polycrystalline aggregate SAPO-5 molecular sieve to a tetrapropylammonium hydroxide (25 wt.%) solution (solid / liquid mass ratio 0.35), stir well, then place it in a reaction kettle for alkali treatment, treatment temperature 90°C, time 5 h, the obtained product is centrifuged, dried overnight to obtain a white solid powder; then calcine at 500°C for 12 h to obtain microporous-mesoporous-macroporous SAPO-5 molecular sieve.

[0064] Example 7

[0065] S71, accurately weigh 1.45 g of aluminum hydroxide into a mixture of 10 mL of distilled water and 3.50 g of triethylamine, stir until completely dissolved, then sequentially add 0.52 g of fumed Si02and 3.67 g of ammonium phosphate monohydrate, mix well to obtain a silicon-aluminum-phosphorus gel;

[0066] S72, move the silicon-aluminum-phosphorus gel into a 100 mL volume stainless steel reactor, then put it into a dynamic oven (rotation speed 55 rpm) for hydrothermal crystallization at 170°C for 12 h, wash the crystallized sample to neutral, dry at 110°C overnight, and calcine at 580°C for 8 h to obtain microporous-mesoporous polycrystalline aggregate SAPO-5 molecular sieve;

[0067] S73, add the microporous-mesoporous polycrystalline aggregate SAPO-5 molecular sieve to a tetrapropylammonium hydroxide (25 wt.%) solution (solid / liquid mass ratio 0.40), stir well and then move it to the reactor for alkaline treatment, the treatment temperature is 100°C and the time is 4 h, the obtained product is centrifuged, dried overnight to obtain a white solid powder; then calcine at 580°C for 5 h to obtain microporous-mesoporous-macroporous SAPO-5 molecular sieve.

[0068] Example 8

[0069] S81, accurately weigh 7.20 g of aluminum isopropoxide into a mixture of 10 mL of distilled water and 3.78 g of morpholine, stir until completely dissolved, then sequentially add 1.58 g of silica sol (30 wt.%) and 2.8 mL of phosphoric acid, mix well to obtain a silicon-aluminum-phosphorus gel;

[0070] S82, move the silicon-aluminum-phosphorus gel into a 100 mL volume stainless steel reactor, then put it into a dynamic oven (rotation speed 50 rpm) for hydrothermal crystallization at 160°C for 36 h, wash the crystallized sample to neutral, dry at 95°C overnight, and calcine at 600°C for 5 h to obtain microporous-mesoporous polycrystalline aggregate SAPO-5 molecular sieve;

[0071] S83, add the microporous-mesoporous polycrystalline aggregate SAPO-5 molecular sieve to a tetrapropylammonium hydroxide (25 wt.%) solution (solid / liquid mass ratio 0.20), stir well and then move it to the reactor for alkaline treatment, the treatment temperature is 110°C and the time is 4 h, the obtained product is centrifuged, dried overnight to obtain a white solid powder, then calcine at 550°C for 12 h to obtain microporous-mesoporous-macroporous SAPO-5 molecular sieve.

[0072] Comparative Example 1

[0073] Accurately weigh 6.48 g of aluminum isopropoxide into a mixture of 8 mL of distilled water and 3.78 g of triethylamine, stir until completely dissolved, then sequentially add 3.6 mL of tetraethyl orthosilicate, 4.0 mL of phosphoric acid, mix well to obtain a silicon-aluminum-phosphorus gel;

[0074] The silicon-aluminum-phosphorus gel is moved into a stainless steel reactor with a volume of 100 mL, then placed in an oven at 180°C for static hydrothermal crystallization for 36 h, the crystallized sample is washed to neutral, dried at 90°C overnight, and calcined at 550°C for 6 h to obtain microporous SAPO-5 molecular sieve.

[0075] Comparative Example 2

[0076] Referring to the Chinese invention patent with publication number CN108264058A, the SAPO-5 (microporous-mesoporous polycrystalline aggregate SAPO-5 molecular sieve prepared in Example 1) is treated with 0.1M tetrapropylammonium hydroxide modifier, and treated at 80°C for 1 h to prepare a molecular sieve with a hierarchical pore structure.

[0077] Comparative Example 3

[0078] Referring to the method disclosed in Example 1 of the Chinese invention patent with publication number CN106745056A, a SAPO-5 molecular sieve with intercrystalline mesoporous structure is prepared, and the specific preparation method is as follows:

[0079] Accurately weigh 1.45 g of aluminum hydroxide into a mixture of 10 mL of distilled water and 3.50 triethylamine, stir until completely dissolved, then sequentially add 0.52 g of fumed SiO2 and 3.67 g of ammonium dihydrogen phosphate, mix well, then form an aerosol through an aerosol generator, dry at 200°C to obtain a silicon-aluminum-phosphorus oxide;

[0080] Put 1 g of the silicon-aluminum-phosphorus oxide into a 10 mL stainless steel synthesis kettle with a polytetrafluoroethylene liner, then add 0.6428 g of a tetrapropylammonium hydroxide aqueous solution (25%), seal and perform a crystallization reaction at 170°C for 48 h, dry the obtained solid product at 100°C, and then calcine at 540°C for 10 h to remove the template agent to obtain a molecular sieve.

[0081] Figure 1 The XRD spectra of the microporous-mesoporous polycrystalline aggregate SAPO-5 molecular sieve and the microporous-mesoporous-macroporous SAPO-5 molecular sieve prepared in Example 1 of the present application can be seen at 2θ = 7.5, 19.9, 21.3 and 22.6°, which correspond to the (100), (210), (002) and (102) crystal planes of the AFI topology, indicating that the microporous-mesoporous polycrystalline aggregate SAPO-5 molecular sieve material prepared by the present application belongs to a typical SAPO-5 molecular sieve.

[0082] Compared with the micropore-mesopore polycrystalline aggregate SAPO-5 molecular sieve, it can be seen that the crystallinity of the SAPO-5 zeolite after alkali treatment remains the original crystallinity, which indicates that the crystal structure of the SAPO-5 zeolite obtained after alkali treatment of tetrapropylammonium hydroxide remains complete.

[0083] Figure 2 For the traditional static synthesis SAPO-5 zeolite, the grain size is about 25 μm, and the surface is dense and smooth.

[0084] Compared with the SEM image of Figure 3 It can be seen from the comparison that the flower cluster-shaped SAPO-5 morphology formed by the accumulation of primary nanorod grains with a diameter of about 20 nm can be successfully synthesized by a dynamic crystallization method, and the flower cluster-shaped SAPO-5 morphology contains rich intercrystalline mesopores. Figure 4 After being crushed by extrusion at 10 MPa, the internal region of the sample is relatively dense. Figure 5 After being treated with tetrapropylammonium hydroxide, the morphology of the zeolite remains complete, but the internal region of the sample appears a (cavity) phenomenon (indicated by a circle in the figure). Figure 6 After being crushed by extrusion at 10 MPa, the silicon, aluminum and phosphorus elements in the internal region of the sample are completely removed, and a hollow flower-shaped SAPO-5 zeolite morphology is formed.

[0085] From the N2 adsorption-desorption isotherm and the corresponding pore size distribution curve (embedded graph) of Figure 7 It can be seen that the sample presents a typical IV-type adsorption isotherm, which indicates that the sample has obvious intercrystalline mesopore structure, and the pore size distribution is in the range of 2-12 nm.After being treated with tetrapropylammonium hydroxide, the pore size distribution of the SAPO-5 does not change obviously, which can further indicate that the crystal of the zeolite remains complete. Further testing of the SAPO-5 after alkali treatment by mercury intrusion porosimetry shows that the sample has obvious macropore structure, and the pore size is mainly concentrated in 1 μm. Figure 8

[0086] The present application further studies the catalytic performance of the above-mentioned sample as a catalytic cracking reaction catalyst, and the specific experimental method is as follows:

[0087] The reaction is carried out in a normal pressure micro fixed bed reactor, and 0.20 g of catalyst is loaded in the reactor. First, N2 is introduced into the reactor at a flow rate of 50 mL / min, and the temperature is raised from room temperature to the reaction temperature (550℃) at a heating rate of 5℃ / min, and the activation time is 1 h, and then the temperature is lowered to 400℃;

[0088] Then, triisopropylbenzene is introduced by using a micro metering pump, and the feeding amount is controlled to be 1 mL / h. The products after reaction are analyzed on a gas chromatograph equipped with a hydrogen flame ionization detector (FID). Table 1 shows the catalytic reaction effect data of the molecular sieves obtained in Examples 1 and Comparative Examples 1-3.

[0089] Table 1 Catalytic effect data

[0090]

[0091] When the micropore-mesopore-macropore SAPO-5 molecular sieve prepared in Example 1 (Example 1b) was used as a catalyst, the conversion rate of triisopropylbenzene was high (98.08%) in the initial reaction of 1 h, and the conversion rate decreased to 88.41% after 8 h of reaction. The average selectivity of the deep cracking products, isopropylbenzene and benzene, was 35.41% and 14.16%, respectively.

[0092] When the micropore-mesopore polycrystalline aggregate SAPO-5 molecular sieve prepared in Example 1 (Example 1a) was used as a catalyst, the conversion rate of triisopropylbenzene was 85.6% in the initial reaction of 1 h, and the conversion rate decreased to 61.88% after 8 h of reaction. The average selectivity of the deep cracking products, isopropylbenzene and benzene, was 37.16% and 10.24%, respectively.

[0093] The catalytic results show that the introduction of mesopores and macropores into the SAPO-5 zeolite can significantly improve the conversion rate and stability of triisopropylbenzene. This is because the kinetic size of the triisopropylbenzene molecule is 0.94 nm, which is significantly larger than the pore of the SAPO-5 zeolite (~0.73 nm). The triisopropylbenzene molecule can first undergo pre-cracking to generate diisopropylbenzene in the mesopore and macropore channels, and then enter the micropore of the zeolite to generate isopropylbenzene and benzene. Therefore, the micropore-mesopore-macropore SAPO-5 zeolite prepared in the present application can efficiently crack heavy oil macromolecules, and has important guiding significance in solving the problem of crude oil heaviness.

[0094] When the micropore SAPO-5 molecular sieve prepared in Comparative Example 1 was used as a catalyst, the conversion rate of triisopropylbenzene was 3.06% in the initial reaction of 1 h, and the conversion rate decreased to 1.98% after 8 h of reaction. The selectivity of the deep cracking products, isopropylbenzene and benzene, was 1.85% and 5.95%, respectively.

[0095] Although the micropore-mesopore polycrystalline aggregate SAPO-5 molecular sieve in Example 1 was also treated with tetrapropylammonium hydroxide in Comparative Example 2, the molecular sieve obtained after treatment did not have a macropore structure, and its morphology was almost the same as that of the untreated zeolite. It can be seen that the treatment conditions of 80°C for 1 h cannot meet the requirements of alkali treatment of the zeolite. In the catalytic reaction performance test, it can be seen that the conversion rate of triisopropylbenzene and the selectivity of the products obtained by the molecular sieve in Comparative Example 2 are very close to those of the untreated catalyst (Example 1a).

[0096] Although tetrapropylammonium hydroxide is also used in Comparative Example 3, it is mainly used as a structure directing agent, and the obtained molecular sieve is a microporous molecular sieve, and thus the catalyst effect is poor.

[0097] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present application, and are not limited thereto; although the present application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that the technical solutions recorded in the foregoing embodiments can still be modified, or some or all of the technical features can be replaced by equivalents; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present application.

Claims

1. A process for the preparation of a micro-meso-macroporous SAPO-5 molecular sieve, characterized in that, The method comprises the following steps: S1, stirring the aluminum source, silicon source, phosphorus source, structure directing agent and water uniformly to obtain a silicon-aluminum-phosphorus gel; S2, placing the silicon-aluminum-phosphorus gel in a reaction kettle and hydrothermally crystallizing in a dynamic oven, and after centrifugation, drying and calcination treatment of the obtained product, a microporous-mesoporous polycrystalline aggregate SAPO-5 molecular sieve is obtained; S3, adding the microporous-mesoporous polycrystalline aggregate SAPO-5 molecular sieve to a tetrapropylammonium hydroxide solution, stirring uniformly, and then placing in a reaction kettle for alkali treatment, and after centrifugation, drying and calcination treatment of the obtained product, a microporous-mesoporous-macroporous SAPO-5 molecular sieve is obtained; Step S1 specifically comprises: dissolving the aluminum source and the structure directing agent in distilled water, stirring until clear, and then adding the silicon source and the phosphorus source in sequence, and stirring uniformly to obtain a silicon-aluminum-phosphorus gel; In the silicon-aluminum-phosphorus gel, the molar ratio of Al2O3, SiO2, P2O5, SDA and H2O is (0.2-1.8):(0.3-0.9):(0.8-5.2):(1.2-10.5):(50-560); In step S2, when hydrothermally crystallizing, the rotation speed of the dynamic oven is controlled to be 20-60 rpm / min, the temperature is controlled to be 140-200℃, and the time is controlled to be 6-48h; In step S3, the volume of the tetrapropylammonium hydroxide solution corresponding to every g of the microporous-mesoporous polycrystalline aggregate SAPO-5 molecular sieve is 2.5-10mL, and the mass fraction of the tetrapropylammonium hydroxide solution is 20-30%; In step S3, when alkali treatment, the temperature is controlled to be 120-180℃, and the time is controlled to be 6-24h.

2. The production method according to claim 1, characterized by, In step S1, the aluminum source includes any one of aluminum isopropoxide, pseudo-boehmite, aluminum sec-butoxide and aluminum hydroxide; The silicon source includes any one of tetraethyl orthosilicate and fumed silica; The structure directing agent includes any one of tetraethylammonium hydroxide, tetrapropylammonium hydroxide, ethylenediamine, triethylamine and morpholine; The phosphorus source includes any one of phosphoric acid, monoammonium phosphate and dihydrogen ammonium phosphate.

3. The preparation method according to claim 1, characterized in that, In step S2, when drying, the temperature is controlled to be 80-120℃, and the time is controlled to be 12-20h; When calcining, the temperature is controlled to be 500-650℃, and the time is controlled to be 2-10h.

4. The production method according to claim 1, characterized by, In step S3, when drying, the temperature is controlled to be 90-110℃, and the time is controlled to be 18-24h; When calcining, the temperature is controlled to be 500-650℃, and the time is controlled to be 3-18h.

5. A micro-mesopore-macropore SAPO-5 molecular sieve characterized in that, The microporous-mesoporous-macroporous SAPO-5 molecular sieve prepared by the preparation method of any one of claims 1-4 has a mesopore size of 2-40nm and a macropore size of 0.1-3μm.

6. Use of the micro-meso-macroporous SAPO-5 molecular sieve of claim 5, characterized in that, The microporous-mesoporous-macroporous SAPO-5 molecular sieve is applied to a triisopropylbenzene cracking reaction.

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