SAPO-11 molecular sieve as well as synthesis method and application thereof

Abstract

The invention provides an SAPO-11 molecular sieve as well as a synthesis method and application thereof. The synthesis method comprises the following steps: uniformly mixing an aluminum source, auxiliary acid, phosphoric acid and water to obtain a phosphorus-aluminum precursor; respectively dissolving a template agent and a solid silicon source with deionized water, and then adding into the phosphorus-aluminum precursor in a pulse charging manner to obtain mixed gel; in the mixed gel, the molar ratio of the aluminum source in terms of Al2O3 to the phosphoric acid in terms of P2O5 to the silicon source in terms of SiO2 to the template agent to the auxiliary acid to the water is 1: (0.90-1.00): (0.40-0.65): (0.70-0.85): (0.05-0.32): (8-15); and pre-crystallizing the mixed gel at 90-150 DEG C for 0.5-2 hours, then crystallizing at 190-210 DEG C for 12-20 hours, and filtering, washing and drying the obtained crystallized product to obtain the SAPO-11 molecular sieve. The synthesis method can effectively inhibit generation of mixed crystals and can improve the single-kettle yield.

Description

Technical Field

[0001] The invention relates to a SAPO-11 molecular sieve and a synthesis method and application thereof, belonging to the technical field of molecular sieve synthesis. Background Art

[0002] SAPO-11 is a phosphorus aluminum silicon molecular sieve with an AEL topological structure, first synthesized by the United Carbide Corporation (UCC) in the 1880s. Its pore structure is a one-dimensional ten-membered ring straight pore with a size of Due to its special pore structure and mild acidity, it can be used to catalyze the hydrogenation isomerization reaction of linear alkanes. At present, the hydrothermal synthesis method is mainly used in the industry to produce SAPO-11. In order to avoid the problems of viscosity and difficulty in dispersion when the solid content of the raw material system is high and the problem of impurity crystals, the water content of the system is still high, and the single-pot yield is only about 6.5%, which restricts production efficiency and cost.

[0003] At present, the research reports on the preparation of molecular sieves under high solid content raw materials are as follows:

[0004] CN 103864088A discloses a method for synthesizing molecular sieves by solid phase grinding, which can produce SAPO-11 molecular sieves with high crystallinity, and greatly improves the yield and single reactor utilization rate. The specific steps include: weighing a silicon source, an aluminum source, and a self-made template agent, pouring them into a mortar, grinding and mixing for 5-10 minutes, and then grinding them evenly and loading them into a reactor for crystallization reaction, wherein the reaction temperature of the crystallization reaction is 180-220° C., and the reaction time is 9h-5d; the silicon source is white carbon black or silica gel, the aluminum source is boehmite or aluminum hydroxide, wherein the content of the boehmite is 70% Al2O3 and 30% H2O, and the self-made template agent is di-n-propylamine phosphate or diisopropylamine phosphate; wherein the specific preparation steps of the self-made template agent include: dropping phosphoric acid into di-n-propylamine or diisopropylamine, then adding anhydrous ethanol, stirring at 0-80° C. for 2 hours to obtain a white solid, washing the residual reactants on the white solid with a mixture of ether and ethanol, and finally drying the washed white solid to obtain di-n-propylamine phosphate or diisopropylamine phosphate for use as a self-made template agent.

[0005] The defects of this technology or the shortcomings relative to the present invention include: 1. Grinding is required during the gelling process, which is not conducive to mixing and gelling, and it is difficult to achieve industrial application; 2. Since the reaction system is in a solid phase, the mass transfer and heat transfer efficiency are low, so a long crystallization time (mostly 3 to 5 days in the embodiments) is required to achieve a higher degree of crystallinity; 3. The template agent is an organic amine phosphate, which needs to be homemade, and the process steps are many and complicated.

[0006] CN106517230A discloses a multi-level porous SAPO-11 molecular sieve and a solid phase synthesis method, which realizes the synthesis of molecular sieves in a solid phase system by using a dual template method. The specific details are: a solid silicon source, an aluminum source, a mesoporous template, a microporous template and a phosphorus source are mixed and ground, and a crystallization reaction is carried out at 200°C; then, the reaction product is filtered, dried and calcined to obtain a molecular sieve raw powder. Since no solvent and organic template are used, the yield is increased and the raw material cost is reduced.

[0007] The defects of this technology or the shortcomings of the present invention include: 1. Grinding is required during the gelling process, which is not conducive to mixing and gelling, and it is difficult to achieve industrial application; 2. The templates are di-n-propylamine phosphate and hexadecyltrimethylammonium bromide. Among them, di-n-propylamine phosphate needs to be made by oneself, and the process steps are many and complicated. The price of hexadecyltrimethylammonium bromide is relatively high. The amount of the two templates accounts for more than 70% of the total mass of the raw materials, which has the problem of high cost.

[0008] CN106044791A discloses a solid phase synthesis method of thin-lamellar SAPO-34, which adds fluoride to the initial gel, solves the problems of low crystallinity and poor stability in solid phase production, and realizes solid phase synthesis. The specific steps include: mixing deionized water, silicon source, aluminum source, phosphorus source, fluoride and template agent in a specific proportion to obtain an initial gel; aging at room temperature and drying at high temperature to obtain a dry gel; then adding a mixed solution of water and triethylamine to the bottom of the reaction kettle, crushing the dry gel and placing it in a polytetrafluoro beaker, placing the beaker on the liquid in the kettle, and crystallizing to obtain a SAPO-34 molecular sieve;.

[0009] The defects of this technology or the shortcomings relative to the present invention include: first, there are many synthesis steps, which leads to a complicated process and affects the yield and cost; second, there are fluorides in the product, and there are safety and environmental problems in the post-processing process.

[0010] CN111434611A discloses a method for preparing NaY molecular sieve by solid phase conversion, which achieves the purpose of solid phase crystallization by adjusting the raw material ratio and optimizing the guiding agent. The specific steps include: according to the ratio requirements of NaY molecular sieve, a certain amount of guiding agent is selectively added to the solid silicon source and aluminum source, and after stirring evenly, it becomes a solid state reaction mixture, which is loaded into a reactor for crystallization reaction, the temperature is controlled at 90℃-140℃, the crystallization time is 24-120 hours, and finally filtered, washed, and dried to obtain a NaY molecular sieve with a relative crystallinity greater than 60%. This method is different from the traditional hydrothermal crystallization method for producing NaY molecular sieve, and has the characteristics of high utilization rate of silicon and aluminum sources and high product yield.

[0011] The defects of this technology or the shortcomings relative to the present invention include: since the reaction materials are solid, the mass transfer and heat transfer in the synthesis process are adversely affected, the crystallinity of the molecular sieve is difficult to improve, and it is difficult to achieve industrial production.

[0012] The article "Quasi-solid-phase method for rapid synthesis of P-type molecular sieves with high calcium and magnesium ion exchange performance" (Zhang Shu, Guo Hongfei, Liu Xiuwu, et al. Quasi-solid-phase method for rapid synthesis of P-type molecular sieves with high calcium and magnesium ion exchange performance [J]. Journal of Inorganic Chemistry, 2019, 35(12): 2323–2330.) achieved the crystallization of P-type molecular sieves in a high solid content system by first preparing silica-alumina xerogel. The specific details are as follows: Na2SiO3·9H2O and Al2(SO4)3·18H2O are dissolved in an appropriate amount of water, heated to 60°C and stirred thoroughly, mixed and cooled to room temperature for filtration, and washed several times until there is no SO4 in the washing liquid. 2- Then place it in a 100℃ constant temperature drying oven and dry it for 3h to obtain a silicon-alumina xerogel. Place the silicon-alumina xerogel in a stainless steel crystallization kettle lined with polytetrafluoroethylene, add sodium hydroxide and water in a certain proportion, stir and mix well, and then statically crystallize it at a certain temperature for a period of time. After the crystallization is completed, take it out and filter it. The solid phase product is washed with deionized water and dried to obtain a P-type molecular sieve product.

[0013] The defects of this technology or the shortcomings relative to the present invention include: 1. Compared with the conventional method, the solid-phase method is realized by first preparing silica-alumina dry gel, and the process is more complicated; 2. As the first generation of molecular sieves, P-type molecular sieves do not require templates during the synthesis process, so the synthesis phase range is very wide, and its theory and method are not applicable to the more complex synthesis system of SAPO-11 molecular sieve.

[0014] In summary, the reports on the production of SAPO-11 molecular sieves with high solid content in the prior art are mostly ground into gel in a mortar. This method has a small processing volume and requires a homemade template, which is difficult to scale up. In addition, the high solid content synthesis methods of other molecular sieves are mostly achieved by introducing fluoride mineralizers and increasing the type or amount of templates, which has the problem of increased costs and environmental emissions. Since SAPO-11 is a one-dimensional pore molecular sieve, its crystal structure belongs to a metastable state and is prone to produce miscellaneous crystals, it is difficult to develop a synthesis method with high solid content.

[0015] Therefore, providing a novel, efficient and stable SAPO-11 molecular sieve and its synthesis method and application has become a technical problem that needs to be solved urgently in this field. Summary of the invention

[0016] In order to solve the above-mentioned shortcomings and deficiencies, an object of the present invention is to provide a method for synthesizing SAPO-11 molecular sieve.

[0017] Another object of the present invention is to provide a SAPO-11 molecular sieve, which is prepared by the above-mentioned synthesis method of SAPO-11 molecular sieve.

[0018] Another object of the present invention is to provide the use of the SAPO-11 molecular sieve described above in catalyzing the hydroisomerization reaction of linear alkanes.

[0019] In order to achieve the above objectives, on the one hand, the present invention provides a method for synthesizing a SAPO-11 molecular sieve, wherein the method for synthesizing a SAPO-11 molecular sieve comprises:

[0020] Step 1: Evenly mix the aluminum source, auxiliary acid, phosphoric acid and water to obtain a phosphorus aluminum precursor;

[0021] Step 2: Dissolve the template and the solid silicon source in deionized water respectively and then add them to the phosphorus aluminum precursor in a pulse feeding manner to obtain a mixed gel;

[0022] Wherein, in the mixed gel, the molar ratio of aluminum source calculated as Al2O3, phosphoric acid calculated as P2O5, silicon source calculated as SiO2, template, auxiliary acid and water is 1:0.90-1.00:0.40-0.65:0.70-0.85:0.05-0.32:8-15;

[0023] Step 3: pre-crystallize the mixed gel at 90-150° C. for 0.5-2 h, and then crystallize at 190-210° C., preferably 200° C. for 12-20 h. After the crystallization is completed, filter, wash and dry the obtained crystallized product to obtain the SAPO-11 molecular sieve.

[0024] As a specific embodiment of the above-described synthesis method of the present invention, step one specifically includes: adding water to the aluminum source, then adding auxiliary acid and phosphoric acid, and then maintaining the system temperature at 40-55°C through temperature control and stirring for 0.5-3h to obtain a phosphorus aluminum precursor.

[0025] As a specific embodiment of the above-mentioned synthesis method of the present invention, the aluminum source includes at least one of pseudo-boehmite and aluminum hydroxide.

[0026] As a specific embodiment of the above-mentioned synthesis method of the present invention, the auxiliary acid includes at least one of hydrochloric acid, nitric acid, sulfuric acid, oxalic acid, malonic acid, terephthalic acid, etc.; preferably at least one of oxalic acid, malonic acid, terephthalic acid, etc. The present invention does not make specific requirements on the concentration of hydrochloric acid, nitric acid and sulfuric acid, which can be reasonably adjusted according to the actual operation conditions. For example, in some embodiments of the present invention, the concentrations of hydrochloric acid, nitric acid and sulfuric acid can be 37%, 63-65% and 96% respectively.

[0027] As a specific embodiment of the above-mentioned synthesis method of the present invention, in step 2, under the condition of temperature control and stirring at 40-55°C, the template and the solid silicon source are dissolved in deionized water respectively, and then added into the phosphate aluminum precursor in a pulse feeding manner to obtain a mixed gel.

[0028] As a specific embodiment of the above-mentioned synthesis method of the present invention, the solid silicon source includes at least one of solid silica gel, white carbon black, etc. In some embodiments of the present invention, the solid silica gel can be macroporous silica gel.

[0029] As a specific embodiment of the above-mentioned synthesis method of the present invention, wherein the template agent is an organic amine template agent.

[0030] As a specific embodiment of the above-mentioned synthesis method of the present invention, the template agent includes at least one of organic amine template agents such as di-n-propylamine and diisopropylamine.

[0031] As a specific embodiment of the above-mentioned synthesis method of the present invention, the pH value of the mixed gel is 5.5-7.0.

[0032] As a specific embodiment of the above-mentioned synthesis method of the present invention, in step 2, if the pH value of the mixed gel is not 5.5-7.0, an auxiliary acid is added to the mixed gel to make its pH value 5.5-7.0.

[0033] In the present invention, since the process of adding the acid and the template in step 1 and step 2 will have a relatively obvious heat release, temperature control is required in both steps. As a specific embodiment of the above-mentioned synthesis method of the present invention, the temperature control method is a water bath.

[0034] As a specific embodiment of the above-mentioned synthesis method of the present invention, the pulse feeding method includes: adding a feeding speed of 1-3% of the total weight of the template solution and the solid silicon source solution per minute, and the number of adding points is 2-4.

[0035] In some embodiments of the present invention, in step 2, the template and the solid silicon source are first dissolved in deionized water, respectively, and then the template solution and the solid silicon source solution are mixed to obtain a mixed solution, and then the mixed solution is added to the phosphate aluminum precursor in a pulse feeding manner to obtain a mixed gel; it is also possible not to mix the template solution and the solid silicon source solution, but directly add the template solution and the solid silicon source solution to the phosphate aluminum precursor separately or simultaneously. When the two are added separately, it is preferred to add the template solution first and then the solid silicon source solution.

[0036] As a specific embodiment of the above-mentioned synthesis method of the present invention, step 1 and step 2 need to be carried out in a closed reaction kettle or reactor; step 3 needs to be carried out in a synthesis kettle.

[0037] As a specific embodiment of the above-mentioned synthesis method of the present invention, the pre-crystallization temperature is 95-130°C.

[0038] In step three of the above-described synthesis method of the present invention, the filtration, washing and drying are conventional operations, and the operation steps and process parameters of filtration, washing and drying can be reasonably adjusted according to the actual needs of the on-site operation.

[0039] On the other hand, the present invention further provides a SAPO-11 molecular sieve, wherein the SAPO-11 molecular sieve is prepared by the above-mentioned synthesis method of the SAPO-11 molecular sieve.

[0040] As a specific embodiment of the SAPO-11 molecular sieve described above in the present invention, the SAPO-11 molecular sieve is in the shape of nanospheres with a particle size of 20-35 nm.

[0041] In yet another aspect, the present invention further provides the use of the SAPO-11 molecular sieve described above in catalyzing the hydroisomerization reaction of linear alkanes.

[0042] Compared with the prior art, the beneficial technical effects that can be achieved by the present invention include:

[0043] (1) The synthesis method of SAPO-11 molecular sieve provided by the present invention can overcome the mass transfer and product impurity crystal problems in the gelation process under the condition of high solid content (water-aluminum ratio of 8-15) raw materials in the prior art, thereby improving the single-pot yield of SAPO-11 molecular sieve. The reasons or mechanisms for producing this beneficial technical effect include: First, temperature control in step 1 and step 2 promotes the dissolution of solid aluminum salt and silicon source, and significantly reduces the viscosity of the system. Second, the multi-point pulse feeding method in step 2 is conducive to the uniform dispersion of each raw material component in the gelation process. The third point: add auxiliary acid, the added auxiliary acid has strong acidity, which can accelerate the dissolution of aluminum source and promote the gelation of phosphoric acid; in addition, when the auxiliary acid is an organic acid such as oxalic acid, malonic acid, terephthalic acid, etc., it also has a relatively good guiding effect, and it is easier to form a pure phase SAPO-11 molecular sieve. The reason may be: some organic acids react with organic amine templates such as di-n-propylamine and diisopropylamine to generate long-chain molecules, and these long-chain molecules have stronger guiding effects; another possibility is that the organic acid undergoes other reactions in the reaction system to generate cations or anions with guiding effects. The fourth point: In step three, pre-crystallization is first carried out at a lower temperature, and then the temperature is increased for crystallization. The use of a lower temperature for pre-crystallization can accelerate the depolymerization and dissolution of the solid raw material, and can also effectively inhibit the formation of impurity crystals. In summary, the present invention suppresses the formation of impurity crystals and obtains pure-phase SAPO-11 molecular sieve by the synergistic effect of four means, namely, adding auxiliary acid, multi-point pulse feeding, temperature control and two-stage crystallization, when synthesizing SAPO-11 molecular sieve.

[0044] (2) Due to the reduction in the amount of water in the raw material system, a corresponding template concentration can be achieved by adding less template, thereby reducing the amount of template by more than 15% (calculated as the template / Al2O3 molar ratio, from 0.95 to less than 0.85). In addition, on the basis of reducing the amount of template, the present invention suppresses the formation of impurity crystals through the synergistic effect of four means: adding auxiliary acid, multi-point pulse feeding, temperature control and two-stage crystallization, thereby obtaining a pure phase SAPO-11 molecular sieve.

[0045] (3) Since the water-aluminum ratio in the raw material is reduced from the original 60 to below 15, the single-pot yield is significantly improved, and the single-pot yield can be increased from 6.5% to more than 25%. In addition, on the basis of reducing the water-aluminum ratio of the raw material, the present invention suppresses the formation of impurity crystals through the synergistic effect of four means: adding auxiliary acid, multi-point pulse feeding, temperature control and two-stage crystallization, and obtains pure-phase SAPO-11 molecular sieve. BRIEF DESCRIPTION OF THE DRAWINGS

[0046] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0047] Figure 1 The XRD pattern of the SAPO-11 molecular sieve provided for Comparative Example 1.

[0048] Figure 2 The XRD pattern of SAPO-11 molecular sieve provided for Comparative Example 2.

[0049] Figure 3 The XRD pattern of SAPO-11 molecular sieve provided for Comparative Example 3.

[0050] Figure 4 The XRD pattern of SAPO-11 molecular sieve provided for Comparative Example 4.

[0051] Figure 5 The XRD pattern of SAPO-11 molecular sieve provided for Comparative Example 5.

[0052] Figure 6 This is the XRD diagram of the SAPO-11 molecular sieve provided in Example 1 of the present invention.

[0053] Figure 7 This is the XRD diagram of the SAPO-11 molecular sieve provided in Example 2 of the present invention.

[0054] Figure 8 This is the XRD diagram of the SAPO-11 molecular sieve provided in Example 3 of the present invention.

[0055] Fig. 9 This is the XRD diagram of the SAPO-11 molecular sieve provided in Example 4 of the present invention.

[0056] Fig.10 This is the XRD diagram of the SAPO-11 molecular sieve provided in Example 5 of the present invention.

[0057] Fig.11 This is the XRD diagram of the SAPO-11 molecular sieve provided in Example 6 of the present invention.

[0058] Fig.12 This is the XRD diagram of the SAPO-11 molecular sieve provided in Example 7 of the present invention.

[0059] Fig.13 This is the XRD diagram of the SAPO-11 molecular sieve provided in Example 8 of the present invention.

[0060] Fig.14This is the XRD diagram of the SAPO-11 molecular sieve provided in Example 9 of the present invention.

[0061] Fig.15 This is a SEM image of the SAPO-11 molecular sieve provided in Example 1 of the present invention. DETAILED DESCRIPTION

[0062] It should be noted that the term "comprises" and any variations thereof in the specification and claims of the present invention and the above-mentioned drawings are intended to cover non-exclusive inclusions. For example, a process, method, system, product or device that includes a series of steps or units is not necessarily limited to those steps or units clearly listed, but may include other steps or units that are not clearly listed or inherent to these processes, methods, products or devices.

[0063] "Scope" disclosed in the present invention is given in the form of lower limit and upper limit. It can be one or more lower limits, and one or more upper limits respectively. A given range is defined by selecting a lower limit and an upper limit. The selected lower limit and upper limit define the boundaries of a particular range. All ranges defined in this way are combinable, i.e. any lower limit can be combined with any upper limit to form a range. For example, for a specific parameter, a range of 60-120 and 80-110 is listed, and it is understood that a range of 60-110 and 80-120 is also expected. In addition, if the minimum range values ​​listed are 1 and 2, and the maximum range values ​​listed are 3, 4 and 5, then the following ranges can all be expected: 1-3, 1-4, 1-5, 2-3, 2-4 and 2-5.

[0064] In the present invention, unless otherwise specified, the numerical range "ab" represents an abbreviation of any real number combination between a and b, where a and b are real numbers. For example, the numerical range "0-5" means that all real numbers between "0-5" have been listed in the present invention, and "0-5" is just an abbreviation of these numerical combinations.

[0065] In the present invention, unless otherwise specified, all embodiments and preferred embodiments mentioned in the present invention can be combined with each other to form a new technical solution.

[0066] In the present invention, unless otherwise specified, all technical features and preferred features mentioned in the present invention can be combined with each other to form a new technical solution.

[0067] In the present invention, if not specifically stated, the term "two" used in this specification means "at least two".

[0068] In the present invention, unless otherwise specified, all steps mentioned herein may be performed sequentially or randomly, but are preferably performed sequentially. For example, the method includes steps (a) and (b), which means that the method may include steps (a) and (b) performed sequentially, or may include steps (b) and (a) performed sequentially. For example, the method may further include step (c), which means that step (c) may be added to the method in any order, for example, the method may include steps (a), (b) and (c), or may include steps (a), (c) and (b), or may include steps (c), (a) and (b), etc.

[0069] In order to make the purpose, technical scheme and advantages of the present invention clearer, the present invention is further described in detail below in conjunction with the attached table, drawings and examples. The following described embodiments are some embodiments of the present invention, rather than all embodiments, and are only used to illustrate the present invention, and should not be regarded as limiting the scope of the present invention. Based on the embodiments in the present invention, all other embodiments obtained by ordinary technicians in the field without making creative work are within the scope of protection of the present invention. If the specific conditions are not specified in the embodiments, they are carried out according to the normal conditions or the conditions recommended by the manufacturer. If the manufacturer is not specified in the reagents or instruments used, they are all conventional products that can be purchased commercially.

[0070] The sources of raw materials or equipment in the examples and comparative examples of the present invention, including raw material names, specifications, manufacturers, etc., are shown in Table 1 below.

[0071] Table 1

[0072]

[0073]

[0074] Example 1

[0075] This embodiment provides a SAPO-11 molecular sieve, which is prepared by a synthesis method comprising the following specific steps:

[0076] (1) Preparation of a phosphate aluminum precursor: Add water to pseudo-boehmite, then add phosphoric acid and hydrochloric acid, and then control the temperature by, for example, maintaining the temperature at 55° C. in a water bath and stirring for 0.5 h to obtain a phosphate aluminum precursor;

[0077] (2) Gelation process: dipropylamine and solid silica gel are dissolved in deionized water respectively, and then the obtained solutions are mixed to obtain a mixed solution, and then the mixed solution is added to the phosphorus aluminum precursor in a pulse feeding manner, the addition rate is 1% (accounting for the total weight of the mixed solution) per minute and two addition points are used until the addition of all the mixed solution is completed, during which stirring and temperature control are maintained at 55°C to finally obtain a mixed gel, the pH value of which is 7.0, and the ratio (molar ratio) of the mixed gel is aluminum source (in terms of Al2O3): phosphoric acid (in terms of P2O5): silicon source (in terms of SiO2): template: auxiliary acid: water = 1:1.00:0.5:0.85:0.05:8;

[0078] (3) Crystallization and unloading process: The obtained mixed gel was added into a synthesis reactor and pre-crystallized at 90°C for 2 h, and then crystallized at 200°C for 20 h. After the crystallization was completed, the product was filtered, washed and dried to obtain the SAPO-11 molecular sieve product. The single-reactor yield was 31.8%.

[0079] Example 2

[0080] This embodiment provides a SAPO-11 molecular sieve, which is prepared by a synthesis method comprising the following specific steps:

[0081] (1) Preparation of a phosphate aluminum precursor: Add water to pseudo-boehmite, then add phosphoric acid and hydrochloric acid, and then control the temperature by, for example, maintaining the temperature at 40° C. in a water bath and stirring for 3 h to obtain a phosphate aluminum precursor;

[0082] (2) Gelation process: diisopropylamine and solid silica gel are dissolved in deionized water respectively, and then the obtained solutions are mixed to obtain a mixed solution, and then the mixed solution is added to the phosphorus aluminum precursor in a pulse feeding manner, the addition rate is 3% per minute (accounting for the total weight of the mixed solution) and 4 addition points are used until the addition of all the mixed solutions is completed, during which stirring and temperature control are maintained at 50° C. Finally, a mixed gel is obtained, the pH value of which is 5.5, and the ratio (molar ratio) of the mixed gel is, aluminum source (calculated as Al2O3): phosphoric acid (calculated as P2O5): silicon source (calculated as SiO2): template: auxiliary acid: water = 1:0.90:0.45:0.85:0.18:15;

[0083] (3) Crystallization and unloading process: The obtained mixed gel was added into a synthesis reactor and pre-crystallized at 150°C for 0.5 h, and then crystallized at 200°C for 12 h. After the crystallization was completed, the product was filtered, washed and dried to obtain the SAPO-11 molecular sieve product. The single-reactor yield was 27.7%.

[0084] Example 3

[0085] This embodiment provides a SAPO-11 molecular sieve, which is prepared by a synthesis method comprising the following specific steps:

[0086] (1) Preparation of a phosphate aluminum precursor: Add water to pseudo-boehmite, then add phosphoric acid and hydrochloric acid, and then control the temperature by, for example, maintaining the temperature at 50° C. in a water bath and stirring for 3 h to obtain a phosphate aluminum precursor;

[0087] (2) Gelation process: dipropylamine and macroporous silica gel are dissolved in deionized water respectively, and then the obtained solutions are mixed to obtain a mixed solution, and then the mixed solution is added to the phosphorus aluminum precursor in a pulse feeding manner, the addition rate is 3% (accounting for the total weight of the mixed solution) per minute and 4 addition points are used until all the mixed solution is added. During this period, stirring and temperature control are maintained at 55° C. Finally, a mixed gel is obtained, the pH value of which is 5.5, and the ratio (molar ratio) of the mixed gel is, aluminum source (calculated as Al2O3): phosphoric acid (calculated as P2O5): silicon source (calculated as SiO2): template: auxiliary acid: water = 1:0.90:0.65:0.85:0.18:12;

[0088] (3) Crystallization and unloading process: The obtained mixed gel was added into a synthesis reactor and pre-crystallized at 150°C for 1 hour, and then crystallized at 200°C for 20 hours. After the crystallization was completed, the product was filtered, washed and dried to obtain the SAPO-11 molecular sieve product. The single-reactor yield was 30.0%.

[0089] Example 4

[0090] This embodiment provides a SAPO-11 molecular sieve, which is prepared by a synthesis method comprising the following specific steps:

[0091] (1) Preparation of a phosphorus aluminum precursor: After adding water to aluminum hydroxide, phosphoric acid and sulfuric acid are added, and then the temperature is maintained at 50° C. in a water bath and stirred for 3 hours to obtain a phosphorus aluminum precursor;

[0092] (2) Gelation process: di-n-propylamine and white carbon black are dissolved in deionized water respectively, and then the obtained solutions are mixed to obtain a mixed solution, and then the mixed solution is added to the phosphorus aluminum precursor in a pulse feeding manner, the addition rate is 1% (accounting for the total weight of the mixed solution) per minute and 4 addition points are used until the addition of all the mixed solution is completed, during which stirring and temperature control are maintained at 50° C. Finally, a mixed gel is obtained, the pH value of which is 6.3, and the ratio (molar ratio) of the mixed gel is, aluminum source (calculated as Al2O3): phosphoric acid (calculated as P2O5): silicon source (calculated as SiO2): template: auxiliary acid: water = 1:0.90:0.40:0.70:0.05:10;

[0093] (3) Crystallization and unloading process: The obtained mixed gel was added into a synthesis reactor and pre-crystallized at 150°C for 2 hours, and then crystallized at 210°C for 18 hours. After the crystallization was completed, the product was filtered, washed and dried to obtain the SAPO-11 molecular sieve. The single-reactor yield was 29.9%.

[0094] Example 5

[0095] This embodiment provides a SAPO-11 molecular sieve, which is prepared by a synthesis method comprising the following specific steps:

[0096] (1) Preparation of a phosphorus aluminum precursor: After adding water to aluminum hydroxide, phosphoric acid and nitric acid are added, and then the temperature is controlled by, for example, maintaining the temperature at 55° C. in a water bath and stirring for 3 hours to obtain a phosphorus aluminum precursor;

[0097] (2) Gelation process: di-n-propylamine, diisopropylamine and solid silica gel are dissolved in deionized water respectively, and then the obtained solutions are mixed to obtain a mixed solution, and then the mixed solution is added to the phosphorus aluminum precursor in a pulse feeding manner, the addition rate is 1% (accounting for the total weight of the mixed solution) per minute and 4 addition points are used until the addition of all the mixed solutions is completed, during which stirring and temperature control are maintained at 45°C to finally obtain a mixed gel with a pH value of 6.8. The ratio (molar ratio) of the mixed gel is aluminum source (calculated as Al2O3): phosphoric acid (calculated as P2O5): silicon source (calculated as SiO2): template: auxiliary acid: water = 1:0.96:0.55:0.85:0.10:8;

[0098] (3) Crystallization and unloading process: The obtained mixed gel was added into the synthesis reactor and pre-crystallized at 120°C for 2 hours, and then crystallized at 190°C for 12 hours. After the crystallization was completed, the product was filtered, washed and dried to obtain the SAPO-11 molecular sieve. The single-reactor yield was 26.7%.

[0099] Example 6

[0100] This embodiment provides a SAPO-11 molecular sieve, which is prepared by a synthesis method comprising the following specific steps:

[0101] (1) Preparation of a phosphate aluminum precursor: Add water to pseudo-boehmite, then add phosphoric acid and hydrochloric acid, and then control the temperature by, for example, maintaining the temperature at 40° C. in a water bath and stirring for 3 h to obtain a phosphate aluminum precursor;

[0102] (2) Gelation process: dipropylamine and white carbon black are dissolved in deionized water respectively, and then the obtained solutions are mixed to obtain a mixed solution, and then the mixed solution is added to the phosphorus aluminum precursor in a pulse feeding manner, the addition rate is 2% per minute (accounting for the total weight of the mixed solution) and 3 addition points are used until the addition of all the mixed solution is completed, during which stirring and temperature control are maintained at 40°C to finally obtain a mixed gel, the pH value of which is 5.5, and the ratio (molar ratio) of the mixed gel is, aluminum source (calculated as Al2O3): phosphoric acid (calculated as P2O5): silicon source (calculated as SiO2): template: auxiliary acid: water = 1:0.95:0.57:0.82:0.13:12;

[0103] (3) Crystallization and unloading process: The obtained mixed gel was added into a synthesis reactor and pre-crystallized at 150°C for 0.5 h, and then crystallized at 200°C for 20 h. After the crystallization was completed, the product was filtered, washed and dried to obtain the SAPO-11 molecular sieve product. The single-reactor yield was 30.3%.

[0104] Example 7

[0105] This embodiment provides a SAPO-11 molecular sieve, which is prepared by a synthesis method comprising the following specific steps:

[0106] (1) Preparation of a phosphate aluminum precursor: Add water to pseudo-boehmite, then add phosphoric acid and oxalic acid, and then control the temperature by, for example, maintaining the temperature at 40° C. in a water bath and stirring for 3 h to obtain a phosphate aluminum precursor;

[0107] (2) Gel formation process: dipropylamine and white carbon black are dissolved in deionized water respectively, and then the obtained solutions are mixed to obtain a mixed solution, and then the mixed solution is added to the phosphorus aluminum precursor in a pulse feeding manner, the addition rate is 1% (accounting for the total weight of the mixed solution) per minute and 4 addition points are used until the addition of all the mixed solutions is completed, during which stirring and temperature control are maintained at 40°C to finally obtain a mixed gel, the pH value of which is 6.4, and the ratio (molar ratio) of the mixed gel is, aluminum source (calculated as Al2O3): phosphoric acid (calculated as P2O5): silicon source (calculated as SiO2): template: auxiliary acid: water = 1:0.95:0.57:0.72:0.20:12;

[0108] (3) Crystallization and unloading process: The obtained mixed gel was added into a synthesis reactor and pre-crystallized at 150°C for 0.5 h, and then crystallized at 190°C for 20 h. After the crystallization was completed, the product was filtered, washed and dried to obtain the SAPO-11 molecular sieve. The single-reactor yield was 29.8%.

[0109] Example 8

[0110] This embodiment provides a SAPO-11 molecular sieve, which is prepared by a synthesis method comprising the following specific steps:

[0111] (1) Preparation of aluminum phosphate precursor: Add water to pseudo-boehmite, then add phosphoric acid and malonic acid, and then control the temperature by, for example, keeping the temperature at 40° C. in a water bath and stirring for 3 h to obtain an aluminum phosphate precursor;

[0112] (2) Gel formation process: di-n-propylamine and white carbon black are dissolved in deionized water respectively, and then the obtained solutions are mixed to obtain a mixed solution, and then the mixed solution is added to the phosphorus aluminum precursor in a pulse feeding manner, the addition rate is 1% (accounting for the total weight of the mixed solution) per minute and 4 addition points are used until the addition of all the mixed solutions is completed, during which stirring and temperature control are maintained at 40°C to finally obtain a mixed gel, whose pH value is 6.4, and the mixed gel ratio (molar ratio) is, aluminum source (calculated as Al2O3): phosphoric acid (calculated as P2O5): silicon source (calculated as SiO2): template: auxiliary acid: water = 1:0.95:0.57:0.79:0.24:12;

[0113] (3) Crystallization and unloading process: The obtained mixed gel was added into a synthesis reactor and pre-crystallized at 150°C for 0.5 h, and then crystallized at 190°C for 20 h. After the crystallization was completed, the product was filtered, washed and dried to obtain the SAPO-11 molecular sieve. The single-reactor yield was 26.1%.

[0114] Example 9

[0115] This embodiment provides a SAPO-11 molecular sieve, which is prepared by a synthesis method comprising the following specific steps:

[0116] (1) Preparing a phosphate aluminum precursor: adding water to pseudo-boehmite, and then adding phosphoric acid, terephthalic acid and hydrochloric acid, and then controlling the temperature by, for example, maintaining the temperature at 40° C. in a water bath and stirring for 3 hours, to obtain a phosphate aluminum precursor;

[0117] (2) Gelation process: di-n-propylamine and white carbon black are dissolved in deionized water respectively, and then the obtained solutions are mixed to obtain a mixed solution, and then the mixed solution is added to the phosphorus aluminum precursor in a pulse feeding manner, the addition rate is 1% (accounting for the total weight of the mixed solution) per minute and 4 addition points are used until all the mixed solution is added, during which stirring and temperature control are maintained at 40°C to finally obtain a mixed gel, whose pH value is 6.2, and the ratio (molar ratio) of the mixed gel is, aluminum source (in terms of Al2O3): phosphoric acid (in terms of P2O5): silicon source (in terms of SiO2): template: auxiliary acid: water = 1:0.95:0.57:0.72:0.28 (terephthalic acid is 0.20, hydrochloric acid is 0.08):12;

[0118] (3) Crystallization and unloading process: The obtained mixed gel was added into the synthesis reactor and pre-crystallized at 150°C for 0.5 h, and then crystallized at 210°C for 20 h. After the crystallization, the product was filtered, washed and dried to obtain the SAPO-11 molecular sieve. The single-reactor yield was 26.4%.

[0119] Comparative Example 1

[0120] This comparative example provides a SAPO-11 molecular sieve, which is prepared by a conventional synthesis method comprising the following specific steps:

[0121] Pseudoboehmite (aluminum source), phosphoric acid, di-n-propylamine (template), silica sol (silicon source) and deionized water are respectively added into a reactor and stirred to obtain a gel in the following proportions (molar ratio): aluminum source (Al2O3): phosphoric acid (P2O5): silicon source (SiO2): template: water = 1:1.05:0.47:0.93:60. Then crystallize at 200°C for 30h. After the crystallization, the crystallized product is dried and calcined to obtain a SAPO-11 molecular sieve product with a single-reactor yield of 6.5%.

[0122] Comparative Example 2 (high solid content, no auxiliary acid added)

[0123] This comparative example provides a SAPO-11 molecular sieve, which is prepared by a synthesis method comprising the following specific steps:

[0124] (1) Preparation of a phosphate aluminum precursor: Add water to pseudo-boehmite, then add phosphoric acid, and then maintain the system temperature at 50° C. by temperature control and stir for 3 h to obtain a phosphate aluminum precursor;

[0125] (2) Gelation process: di-n-propylamine and solid silica gel are dissolved in deionized water respectively, and then the obtained solutions are mixed to obtain a mixed solution, and then the mixed solution is added to the phosphorus aluminum precursor in a pulse feeding manner, and the addition rate is 1% (accounting for the total weight of the mixed solution) per minute and two addition points are used until the addition of all the mixed solutions is completed. During this period, stirring and temperature control are maintained at 55° C. Finally, a mixed gel is obtained, and its pH value is 7.0. The ratio (molar ratio) of the mixed gel is aluminum source (calculated as Al2O3): phosphoric acid (calculated as P2O5): silicon source (calculated as SiO2): template: water = 1:1.00:0.65:0.85:15;

[0126] (3) Crystallization and unloading process: The obtained mixed gel was added into a synthesis reactor and pre-crystallized at 150°C for 0.5 h, and then crystallized at 200°C for 20 h. After the crystallization was completed, the mixture was filtered, washed and dried to obtain the SAPO-11 molecular sieve product with a single-reactor yield of 26.6%.

[0127] Comparative Example 3 (high solid content, preparation of aluminum-phosphorus precursor and gelation process without temperature control and insulation)

[0128] This comparative example provides a SAPO-11 molecular sieve, which is prepared by a synthesis method comprising the following specific steps:

[0129] (1) Preparation of aluminum phosphate precursor: Add water to pseudo-boehmite, then add phosphoric acid and hydrochloric acid, and then stir for 3 hours to obtain an aluminum phosphate precursor;

[0130] (2) Gelation process: di-n-propylamine and white carbon black are dissolved in deionized water respectively, and then the obtained solutions are mixed to obtain a mixed solution, and then the mixed solution is added to the phosphorus aluminum precursor in a pulse feeding manner, the addition rate is 1% (accounting for the total weight of the mixed solution) per minute and 3 addition points are used until the addition of all the mixed solutions is completed, and stirring is maintained during the period, and finally a mixed gel is obtained, the pH value of which is controlled at 6.3, and the ratio (molar ratio) of the mixed gel is, aluminum source (calculated as Al2O3): phosphoric acid (calculated as P2O5): silicon source (calculated as SiO2): template: auxiliary acid: water = 1:0.90:0.45:0.80:0.15:15;

[0131] (3) Crystallization and unloading process: The obtained mixed gel was added into a synthesis reactor and pre-crystallized at 150°C for 0.5 h, and then crystallized at 200°C for 20 h. After the crystallization was completed, the mixture was filtered, washed and dried to obtain the SAPO-11 molecular sieve product with a single-reactor yield of 21.3%.

[0132] Comparative Example 4 (high solid content, pulse feeding method not used in gelling process)

[0133] This comparative example provides a SAPO-11 molecular sieve, which is prepared by a synthesis method comprising the following specific steps:

[0134] (1) Preparation of a phosphate aluminum precursor: Add water to pseudo-boehmite, then add phosphoric acid and hydrochloric acid, and then maintain the system temperature at 50° C. by temperature control and stir for 3 h to obtain a phosphate aluminum precursor;

[0135] (2) Gelation process: dipropylamine and solid silica gel are dissolved in deionized water respectively, and then the obtained solutions are mixed to obtain a mixed solution, and then the mixed solution is added to the phosphorus aluminum precursor, and stirred for 1 hour under a temperature-controlled insulation state of 55° C. to finally obtain a mixed gel, whose pH value is controlled at 5.5. The ratio (molar ratio) of the obtained mixed gel is aluminum source (calculated as Al2O3): phosphoric acid (calculated as P2O5): silicon source (calculated as SiO2): template: auxiliary acid: water = 1:0.90:0.65:0.85:0.18:8;

[0136] (3) Crystallization and unloading process: The obtained mixed gel was added into a synthesis reactor and pre-crystallized at 110°C for 1 hour, and then crystallized at 200°C for 20 hours. After the crystallization was completed, the product was filtered, washed and dried to obtain the SAPO-11 molecular sieve product with a single-reactor yield of 29.1%.

[0137] Comparative Example 5 (high solid content, no pre-crystallization)

[0138] This comparative example provides a SAPO-11 molecular sieve, which is prepared by a synthesis method comprising the following specific steps:

[0139] (1) Preparation of a phosphorus aluminum precursor: After adding water to aluminum hydroxide, phosphoric acid and sulfuric acid are added, and then the temperature is maintained at 50° C. in a water bath and stirred for 3 hours to obtain a phosphorus aluminum precursor;

[0140] (2) Gelation process: di-n-propylamine and white carbon black are dissolved in deionized water respectively, and then the obtained solutions are mixed to obtain a mixed solution, and then the mixed solution is added to the phosphorus aluminum precursor in a pulse feeding manner, the addition rate is 1% (accounting for the total weight of the mixed solution) per minute and 4 addition points are used until the addition of all the mixed solution is completed, during which stirring and temperature control are maintained at 50° C. Finally, a mixed gel is obtained, the pH value of which is 6.3, and the ratio (molar ratio) of the mixed gel is, aluminum source (calculated as Al2O3): phosphoric acid (calculated as P2O5): silicon source (calculated as SiO2): template: auxiliary acid: water = 1:0.90:0.40:0.70:0.05:10;

[0141] (3) Crystallization and unloading process: The obtained mixed gel was added into a synthesis reactor and crystallized at 200°C for 20 hours. After the crystallization was completed, the SAPO-11 molecular sieve product was filtered, washed and dried, and the single-reactor yield was 32.5%.

[0142] Test Example 1

[0143] In this test example, the crystal form of the SAPO-11 molecular sieves provided in Examples 1 to 9 and Comparative Examples 1 to 5 was determined, wherein the crystal form was determined by XRD test and performed on a Bruker D2 diffractometer using a Cu target K α The light source was (λ=0.15432 nm), the tube voltage was 40 kV, the tube current was 40 mA, and the scanning speed in the range of 5-40° was 4° / min. X-ray diffraction cards (JCPDS) were used for qualitative analysis.

[0144] Among them, the XRD patterns of the products provided by Comparative Examples 1 to 5 and Examples 1 to 9 are as follows: Figure 1-Figure 14 shown.

[0145] from Figure 1 It can be seen that the product provided in Comparative Example 1 is also a pure phase SAPO-11 molecular sieve, but the existing synthesis method provided in Comparative Example 1 has the following disadvantages: the water content of the raw material is relatively high, resulting in a low yield of the product, further affecting production efficiency and energy consumption;

[0146] from Figure 2 It can be seen that although the product provided in Comparative Example 2 is SAPO-11 molecular sieve, it contains obvious AlPO-C impurity crystals;

[0147] from Figure 3 It can be seen that although the product provided in Comparative Example 3 is SAPO-11 molecular sieve, it also contains obvious AlPO-C impurity crystals;

[0148] from Figure 4 It can be seen that although the product provided in Comparative Example 4 is a SAPO-11 molecular sieve, it contains obvious SAPO-31 impurity crystals;

[0149] from Figure 5 It can be seen that the product provided in Comparative Example 5 is a mixed crystal of SAPO-11 and SAPO-31 molecular sieves.

[0150] from Figure 6-Figure 14 It can be seen that the products provided by Examples 1 to 9 of the present invention are all pure-phase SAPO-11 molecular sieves without impurity crystals.

[0151] At the same time, taking the XRD relative crystallinity of the SAPO-11 molecular sieve provided in Comparative Example 1 as 100%, the relative crystallinity of the SAPO-11 molecular sieve products provided in Examples 1 to 9 of the present invention was calculated, and the data are shown in Table 2 below. Among them, the calculation method of the relative crystallinity includes: first selecting 8 characteristic peaks of 2θ of 8.14°, 9.48°, 15.70°, 21.10°, 22.18°, 22.60°, 22.76° and 23.22° in the XRD spectrum of the SAPO-11 molecular sieve sample provided in Comparative Example 1, and calculating the sum of the peak intensities of the 8 characteristic peaks, and then taking 8 characteristic peaks of 2θ of 8.14°, 9.48°, 15.70°, 21.10°, 22.18°, 22.60°, 22.76° and 23.22° in the XRD spectrum of the SAPO-11 molecular sieve sample provided in Examples 1 to 9 of the present invention, respectively, calculating the sum of the peak intensities of the 8 characteristic peaks, and then comparing the sum of the peak intensities in the embodiments with the sum of the peak intensities in Comparative Example 1, respectively, to obtain the relative crystallinity of each sample, and the results are shown in Table 2.

[0152] Table 2

[0153] product Relative crystallinity / % Comparative Example 1 100 Example 1 94 Example 2 89 Example 3 92 Example 4 91 Example 5 93 Example 6 92 Example 7 98 Example 8 98 Example 9 101

[0154] It can be seen from Table 2 above that, compared with Examples 1 to 6, Examples 7 to 9 of the present invention use organic acids as auxiliary acids, and the crystallinity of the SAPO-11 molecular sieve products prepared in these Examples is significantly improved. This is because the organic acid has a certain structure-guiding effect in the crystallization process, and it is easier to synthesize a pure-phase SAPO-11 molecular sieve product after adding the organic acid.

[0155] Test Example 2

[0156] In this test example, a JSM-7610F Plus emission scanning electron microscope was used to analyze the morphology of the product provided in Example 1, with an operating voltage of 5-20 kV and a magnification of 1 000-50 000 times. Fig.15 As shown. Fig.15 It can be seen that the morphology of SAPO-11 provided in Example 1 is nanoscale spheres with a particle size of 20-35 nm.

[0157] In summary, the synthesis method of SAPO-11 molecular sieve provided by the embodiment of the present invention can overcome the mass transfer and product impurity crystal problems in the gelation process of the prior art under the condition of high solid content (water-aluminum ratio of 8-15) raw materials, thereby improving the single-pot yield of SAPO-11 molecular sieve. The reasons or mechanisms for producing this beneficial technical effect include: First, temperature control in step 1 and step 2 promotes the dissolution of solid aluminum salt and silicon source, and significantly reduces the viscosity of the system. Second, the multi-point pulse feeding method in step 2 is conducive to the uniform dispersion of each raw material component in the gelation process. The third point: add auxiliary acid, the added auxiliary acid has strong acidity, which can accelerate the dissolution of aluminum source and promote the gelation of phosphoric acid; in addition, when the auxiliary acid is an organic acid such as oxalic acid, malonic acid, terephthalic acid, etc., it also has a relatively good guiding effect, and it is easier to form a pure phase SAPO-11 molecular sieve. The reason may be: some organic acids react with organic amine templates such as di-n-propylamine and diisopropylamine to generate long-chain molecules, and these long-chain molecules have stronger guiding effects; another possibility is that the organic acid undergoes other reactions in the reaction system to generate cations or anions with guiding effects. The fourth point: In step three, pre-crystallization is first carried out at a lower temperature, and then the temperature is increased for crystallization. The use of a lower temperature for pre-crystallization can accelerate the depolymerization and dissolution of the solid raw material, and can also effectively inhibit the formation of impurity crystals. In summary, when synthesizing SAPO-11 molecular sieve in the embodiment of the present invention, the generation of impurity crystals is suppressed through the synergistic effect of the four means of adding auxiliary acid, multi-point pulse feeding, temperature control and two-stage crystallization, and a pure phase SAPO-11 molecular sieve is obtained.

[0158] In the embodiment of the present invention, since the amount of water in the raw material system is reduced, a corresponding template concentration can be achieved by adding less template, thereby reducing the amount of template by more than 15% (in terms of template / Al2O3 molar ratio, from 0.95 to below 0.85). In addition, on the basis of reducing the amount of template, the embodiment of the present invention suppresses the formation of impurity crystals through the synergistic effect of four means, namely, adding auxiliary acid, multi-point pulse feeding, temperature control and two-stage crystallization, to obtain a pure phase SAPO-11 molecular sieve.

[0159] In the embodiment of the present invention, since the water-aluminum ratio in the raw material is reduced from the original 60 to below 15, the single-pot yield is significantly improved, and the single-pot yield can be increased from 6.5% to more than 25%. In addition, on the basis of reducing the water-aluminum ratio of the raw material, the embodiment of the present invention suppresses the formation of impurity crystals through the synergistic effect of four means of adding auxiliary acid, multi-point pulse feeding, temperature control and two-stage crystallization, and obtains a pure phase SAPO-11 molecular sieve.

[0160] The above is only a specific embodiment of the present invention, and cannot be used to limit the scope of the invention. Therefore, the replacement of equivalent components, or equivalent changes and modifications made according to the protection scope of the patent of the present invention, should still fall within the scope of this patent. In addition, the technical features of the present invention can be freely combined with each other, with each other and with each other, and with each other.

Claims

1. A method for synthesizing SAPO-11 molecular sieve, characterized in that: The synthesis method of the SAPO-11 molecular sieve comprises: Step 1: Evenly mix the aluminum source, auxiliary acid, phosphoric acid and water to obtain a phosphorus aluminum precursor; Step 2: Dissolve the template and the solid silicon source in deionized water respectively and then add them to the phosphorus aluminum precursor in a pulse feeding manner to obtain a mixed gel; Wherein, in the mixed gel, the molar ratio of aluminum source calculated as Al2O3, phosphoric acid calculated as P2O5, silicon source calculated as SiO2, template, auxiliary acid and water is 1:0.90-1.00:0.40-0.65:0.70-0.85:0.05-0.32:8-15; Step 3: pre-crystallize the mixed gel at 90-150° C. for 0.5-2 h, then crystallize at 190-210° C. for 12-20 h, and then filter, wash and dry the obtained crystallized product to obtain the SAPO-11 molecular sieve.

2. The synthesis method according to claim 1, characterized in that Step 1 specifically includes: adding water to the aluminum source, then adding auxiliary acid and phosphoric acid, and then maintaining the system temperature at 40-55° C. by temperature control and stirring for 0.5-3 hours to obtain a phosphorus aluminum precursor.

3. The synthesis method according to claim 1 or 2, characterized in that The aluminum source includes at least one of pseudo-boehmite and aluminum hydroxide.

4. The synthesis method according to claim 1 or 2, characterized in that The auxiliary acid includes at least one of hydrochloric acid, nitric acid, sulfuric acid, oxalic acid, malonic acid and terephthalic acid.

5. The synthesis method according to claim 4, characterized in that The auxiliary acid includes at least one of oxalic acid, malonic acid and terephthalic acid.

6. The synthesis method according to claim 1, characterized in that In step 2, the template and the solid silicon source are dissolved in deionized water respectively under the condition of temperature control and stirring at 40-55° C., and then added into the phosphate aluminum precursor in a pulse feeding manner to obtain a mixed gel.

7. The synthesis method according to claim 1 or 6, characterized in that: The solid silicon source includes at least one of solid silica gel and white carbon black.

8. The synthesis method according to claim 1 or 6, characterized in that: The template agent includes at least one of di-n-propylamine and diisopropylamine.

9. The synthesis method according to claim 1 or 6, characterized in that: The pH value of the mixed gel is 5.5-7.

0.

10. The synthesis method according to claim 9, characterized in that In step 2, if the pH value of the mixed gel is not 5.5-7.0, an auxiliary acid is added to the mixed gel to adjust the pH value to 5.5-7.

0.

11. The synthesis method according to claim 1 or 6, characterized in that: The pulse feeding method includes: adding a feeding speed of 1-3% of the total weight of the template solution and the solid silicon source solution per minute, and adding points of 2-4.

12. The synthesis method according to claim 1, characterized in that: The pre-crystallization temperature is 95-130°C.

13. A SAPO-11 molecular sieve, characterized in that: The SAPO-11 molecular sieve is prepared by the synthesis method of the SAPO-11 molecular sieve according to any one of claims 1 to 12.

14. The SAPO-11 molecular sieve according to claim 13, characterized in that: The SAPO-11 molecular sieve is in the shape of nanospheres, and the particle size is 20-35 nm.

15. Use of the SAPO-11 molecular sieve according to claim 13 or 14 in catalyzing the hydroisomerization reaction of linear alkanes.

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