Hierarchical pore SAPO-18 molecular sieve as well as synthesis method and application thereof

Abstract

The invention relates to the technical field of porous inorganic materials, in particular to a hierarchical pore SAPO-18 molecular sieve and a synthesis method and application thereof, the molecular sieve is prepared by synthesizing a silicon source, an aluminum source, a phosphorus source, a template agent, deionized water and a pore forming agent through a one-step method; wherein the silicon source is calculated according to SiO2, the aluminum source is calculated according to Al2O3, the phosphorus source is calculated according to P2O5, R is a template agent, and T is a pore forming agent; the molar ratio of SiO2 to Al2O3 to P2O5 to R to H2O to T is (0.1 to 1.5) to 1 to (0.8 to 1.5) to (1.5 to 3.0) to (30 to 100) to (0.5 to 3). The method has the advantages that the synthesis process is simple and convenient to operate, and the service life of the SAPO-18 molecular sieve in olefin cracking reaction can be effectively prolonged while the hierarchical porous SAPO-18 molecular sieve is rapidly synthesized.

Description

Technical Field

[0001] The invention relates to the technical field of porous inorganic materials, and in particular to a multi-level porous SAPO-18 molecular sieve and a synthesis method and application thereof. Background Art

[0002] As one of the important chemical raw materials, propylene is used to produce a variety of chemical products widely used in industrial production and people's daily life, such as polypropylene, propylene oxide, phenol and acetone. In addition to hydrocarbon steam cracking, catalytic cracking, methanol to olefins and propane dehydrogenation, the catalytic cracking of C4 olefins is also an important way to obtain propylene. In the field of olefin cracking, the eight-membered ring small pore SAPO-34 molecular sieve has been widely used due to its excellent catalytic performance. However, the microporous structure of the SAPO-34 molecular sieve limits its diffusion performance in reactions involving or generating macromolecules, resulting in severe carbon deposition and easy deactivation of the catalyst. Summary of the invention

[0003] The purpose of the present invention is to overcome the deficiencies in the prior art and provide a multi-level pore SAPO-18 molecular sieve and its synthesis method and application. By using a pore-forming agent in the process of synthesizing the SAPO-18 molecular sieve, a SAPO-18 molecular sieve with a multi-level pore structure can be synthesized, which not only simplifies the preparation process, but also improves the mass transfer performance and anti-carbon deposition ability of the molecular sieve, thereby extending the service life of the catalyst. The method exhibits excellent catalytic performance in olefin cracking reactions and has broad industrial application prospects.

[0004] The present invention is achieved through the following technical scheme: on the one hand, a method for synthesizing a multi-level pore SAPO-18 molecular sieve is provided, wherein the molecular sieve is prepared by synthesizing a silicon source, an aluminum source, a phosphorus source, a template agent, deionized water and a pore-forming agent through a one-step method; wherein the silicon source is calculated as SiO2, the aluminum source is calculated as Al2O3, the phosphorus source is calculated as P2O5, R is a template agent, and T is a pore-forming agent; that is, the molar ratio of SiO2:Al2O3:P2O5:R:H2O:T is 0.1~1.5:1:0.8~1.5:1.5~3.0:30~100:0.5~3.

[0005] The above technical solution can prepare SAPO-18 molecular sieves with multi-level pore structure in one step, which simplifies the synthesis process and saves energy compared with the existing two-step method for preparing SAPO-18 molecular sieves with multi-level pore structure. At the same time, the pore-forming agent used has the advantages of being cheap, environmentally friendly and easy to remove.

[0006] Further, the following steps are included: Step S1: at room temperature, after deionized water and phosphoric acid are fully stirred in the above molar ratio to form a transparent solution, an aluminum source and a silicon source are added in sequence and fully stirred to form a white emulsion, and a template is added and fully stirred; Step S2: adding the pore-forming agent to the mixed solution obtained in step S1, stirring evenly, and aging to form a synthetic sol; Step S3: placing the synthetic sol prepared in step S2 into a crystallization kettle to perform a dynamic hydrothermal reaction; Step S4: washing, centrifuging, drying and calcining the synthetic solution after the reaction in step S3 to obtain hierarchical pore SAPO-18 molecular sieve raw powder.

[0007] Further, in step S1, the silicon source SiO2 is selected from one or more of white carbon black, silica sol, ethyl orthosilicate and water glass, preferably white carbon black and silica sol, and most preferably silica sol; Alternatively, the aluminum source Al2O3 is selected from one or more of pseudo-boehmite, aluminum isopropoxide, aluminum sol, hydrated aluminum oxide and boehmite, preferably pseudo-boehmite, aluminum isopropoxide, and most preferably pseudo-boehmite; Alternatively, the phosphorus source P2O5 is selected from one or more of phosphoric acid, phosphorous acid, phosphates, and phosphorus oxides, preferably phosphoric acid and phosphorous acid, and most preferably phosphoric acid; Alternatively, the template agent R is selected from one or more of N,N-dimethylisopropyldiamine, diethylamine, triethylamine, isopropylamine, tetraethylammonium hydroxide and tetraethylammonium bromide, preferably N,N-dimethylisopropyldiamine, tetraethylammonium hydroxide, and most preferably N,N-dimethylisopropyldiamine; Furthermore, in step S1, after deionized water and phosphoric acid are fully mixed, an aluminum source and a silicon source are added and fully mixed, and then the mixture is fully mixed with a template agent to obtain the mixed solution; In step S2, the pore-forming agent is carbonamide.

[0008] Further, in step S3, in the crystallization kettle, the crystallization speed is 100-200 rpm, the crystallization temperature is 150-180° C., and the crystallization time is 48-72 h.

[0009] Furthermore, in step S4, the drying temperature is 80-120° C., and the drying time is 2-12 hours.

[0010] Furthermore, in step S4, the calcination temperature is 450-650° C., and the calcination time is 4-12 hours.

[0011] Furthermore, in step S4, the calcination environment gas is an inert gas selected from one or more of nitrogen and helium.

[0012] A multi-level porous SAPO-18 molecular sieve prepared by the above-mentioned synthesis method is also provided, and the molecular sieve has a microporous and mesoporous structure; its specific surface area is 480~580m 2 / g, and its pore volume is 0.31~0.48cm 3 / g.

[0013] The invention further provides an application of the multi-level pore SAPO-18 molecular sieve in the catalytic cracking of C4 olefins to produce propylene.

[0014] Beneficial Effects The method for synthesizing the multi-level pore SAPO-18 molecular sieve provided by the present invention simplifies the synthesis steps of the multi-level pore SAPO-18 molecular sieve and saves preparation energy consumption.

[0015] The multi-level pore SAPO-18 molecular sieve synthesis method provided by the present invention uses a pore-forming agent which has the advantages of being cheap, environmentally friendly, and easy to burn off.

[0016] The multi-level pore SAPO-18 molecular sieve synthesis method provided by the present invention improves the mass transfer performance of the molecular sieve and enhances the anti-carbon deposition ability.

[0017] The multi-level porous SAPO-18 molecular sieve catalyst provided by the present invention enables reactants to more fully contact active sites during the catalytic cracking of C4 olefins, improves the mass transfer performance of macromolecular reactants in the molecular sieve, and thus increases the reaction activity and life of the molecular sieve. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 This is a SEM image of the multi-level pore SAPO-18 molecular sieve described in Example 1; Figure 2 This is the SEM image of the conventional SAPO-18 molecular sieve described in Comparative Example 1; Figure 3 is the XRD pattern of the multi-level pore SAPO-18 molecular sieve described in Examples 1 to 9; Figure 4 It is a performance diagram of 1-butene conversion rate of the catalysts described in Example 1, Comparative Example 1 and Comparative Example 2. DETAILED DESCRIPTION

[0019] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with specific embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0020] Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention. The experimental methods without specific conditions in the following examples are usually carried out under conventional conditions or according to the conditions recommended by the manufacturer. Unless otherwise specified, all percentages, ratios, proportions or parts are by weight.

[0021] Unless otherwise specified, the reagents and raw materials used in the examples and comparative examples of the present invention can be obtained through commercial channels.

[0022] Example 1 Preparation of multi-level pore SAPO-18 molecular sieve 219.1g of phosphoric acid (85%), 131.2g of pseudo-boehmite, 928.7g of deionized water, 271.5g of N, N-dimethylisopropyldiamine and 60.1g of silica sol (30%) were mixed and stirred in sequence, and then 30.1g of carbonamide was weighed and added to the mixed solution, and stirred rapidly for 1h. The mixed solution was introduced into a stainless steel reactor, heated to 165℃ at 10℃ / min, and crystallized dynamically (100rpm) for 72h. After the crystallization reaction was completed, the reactor was quickly cooled to room temperature, and the formed crystals were washed and centrifuged to a pH value of 7~9. The obtained solid product was dried at 120℃ for 6h and then calcined at 550℃ for 4h to obtain a multi-level porous SAPO-18 molecular sieve. The XRD results are as follows Figure 3 As shown, in addition, SEM ( Figure 1 ) The results showed that the grain size of the prepared multi-level pore SAPO-18 molecular sieve was about 1um, and the grain surface had a mesoporous structure.

[0023] Example 2 Preparation of multi-level pore SAPO-18 molecular sieve 219.1g of phosphoric acid (85%), 131.2g of pseudo-boehmite, 928.7g of deionized water, 271.5g of N, N-dimethylisopropyldiamine and 60.1g of silica sol (30%) were mixed and stirred in sequence, and then 91.0g of carbonamide was weighed and added to the mixed solution, and stirred rapidly for 1h. The mixed solution was introduced into a stainless steel reactor, heated to 165℃ at 10℃ / min, and crystallized dynamically (100rpm) for 72h. After the crystallization reaction was completed, the reactor was quickly cooled to room temperature, and the formed crystals were washed and centrifuged to a pH value of 7~9. The obtained solid product was dried at 120℃ for 6h and then calcined at 550℃ for 4h to obtain a multi-level porous SAPO-18 molecular sieve. The XRD results are as follows: Figure 3 shown.

[0024] Example 3 Preparation of multi-level pore SAPO-18 molecular sieve 219.1g of phosphoric acid (85%), 131.2g of pseudo-boehmite, 928.7g of deionized water, 271.5g of N, N-dimethylisopropyldiamine and 60.1g of silica sol (30%) were mixed and stirred in sequence, and then 182.1g of carbonamide was weighed and added to the mixed solution, and stirred rapidly for 1h. The mixed solution was introduced into a stainless steel reactor, heated to 165℃ at 10℃ / min, and crystallized dynamically (100rpm) for 72h. After the crystallization reaction was completed, the reactor was quickly cooled to room temperature, and the formed crystals were washed and centrifuged to a pH value of 7~9. The obtained solid product was dried at 120℃ for 6h and then calcined at 550℃ for 4h to obtain a multi-level porous SAPO-18 molecular sieve. The XRD results are as follows Figure 3 shown.

[0025] Example 4 Preparation of multi-level pore SAPO-18 molecular sieve 219.1g of phosphoric acid (85%), 131.2g of pseudo-boehmite, 928.7g of deionized water, 271.5g of N, N-dimethylisopropyldiamine and 15.1g of silica sol (30%) were mixed and stirred in sequence, and then 30.1g of carbonamide was weighed and added to the mixed solution, and stirred rapidly for 1h. The mixed solution was introduced into a stainless steel reactor, heated to 165℃ at 10℃ / min, and crystallized dynamically (100rpm) for 72h. After the crystallization reaction was completed, the reactor was quickly cooled to room temperature, and the formed crystals were washed and centrifuged to a pH value of 7~9. The obtained solid product was dried at 120℃ for 6h and then calcined at 550℃ for 4h to obtain a multi-level porous SAPO-18 molecular sieve. The XRD results are as follows: Figure 3 shown.

[0026] Example 5 Preparation of multi-level pore SAPO-18 molecular sieve 219.1g of phosphoric acid (85%), 131.2g of pseudo-boehmite, 928.7g of deionized water, 271.5g of N, N-dimethylisopropyldiamine and 225.3g of silica sol (30%) were mixed and stirred in sequence, and then 30.1g of carbonamide was weighed and added to the mixed solution, and stirred rapidly for 1h. The mixed solution was introduced into a stainless steel reactor, heated to 165℃ at 10℃ / min, and crystallized dynamically (100rpm) for 72h. After the crystallization reaction was completed, the reactor was quickly cooled to room temperature, and the formed crystals were washed and centrifuged to a pH value of 7~9. The obtained solid product was dried at 120℃ for 6h and then calcined at 550℃ for 4h to obtain a multi-level porous SAPO-18 molecular sieve. The XRD results are as follows Figure 3 shown.

[0027] Example 6 Preparation of multi-level pore SAPO-18 molecular sieve 184.5g of phosphoric acid (85%), 131.2g of pseudo-boehmite, 928.7g of deionized water, 271.5g of N, N-dimethylisopropyldiamine and 60.1g of silica sol (30%) were mixed and stirred in sequence, and then 30.1g of carbonamide was weighed and added to the mixed solution, and stirred rapidly for 1h. The mixed solution was introduced into a stainless steel reactor, heated to 165℃ at 10℃ / min, and crystallized dynamically (100rpm) for 72h. After the crystallization reaction was completed, the reactor was quickly cooled to room temperature, and the formed crystals were washed and centrifuged to a pH value of 7~9. The obtained solid product was dried at 120℃ for 6h and then calcined at 550℃ for 4h to obtain a multi-level porous SAPO-18 molecular sieve. The XRD results are as follows: Figure 3 shown.

[0028] Example 7 Preparation of multi-level pore SAPO-18 molecular sieve 345.9g of phosphoric acid (85%), 131.2g of pseudo-boehmite, 928.7g of deionized water, 271.5g of N, N-dimethylisopropyldiamine and 60.1g of silica sol (30%) were mixed and stirred in sequence, and then 30.1g of carbonamide was weighed and added to the mixed solution, and stirred rapidly for 1h. The mixed solution was introduced into a stainless steel reactor, heated to 165℃ at 10℃ / min, and crystallized dynamically (100rpm) for 72h. After the crystallization reaction was completed, the reactor was quickly cooled to room temperature, and the formed crystals were washed and centrifuged to a pH value of 7~9. The obtained solid product was dried at 120℃ for 6h and then calcined at 550℃ for 4h to obtain a multi-level porous SAPO-18 molecular sieve. The XRD results are as follows: Figure 3 shown.

[0029] Example 8 Preparation of multi-level pore SAPO-18 molecular sieve 219.1g of phosphoric acid (85%), 131.2g of pseudo-boehmite, 928.7g of deionized water, 1178.1g of tetraethylammonium hydroxide (25%), and 60.1g of silica sol (30%) were mixed and stirred in sequence, and then 30.1g of carbonamide was weighed and added to the mixed solution, and stirred rapidly for 1h. The mixed solution was introduced into a stainless steel reactor, heated to 165℃ at 10℃ / min, and crystallized dynamically (100rpm) for 72h. After the crystallization reaction was completed, the reactor was quickly cooled to room temperature, and the formed crystals were washed and centrifuged to a pH value of 7~9. The obtained solid product was dried at 120℃ for 6h and then calcined at 550℃ for 4h to obtain a multi-level porous SAPO-18 molecular sieve. The XRD results are as follows Figure 3 shown.

[0030] Example 9 Preparation of multi-level pore SAPO-18 molecular sieve 219.1g of phosphoric acid (85%), 131.2g of pseudo-boehmite, 928.7g of deionized water, 212.6g of triethylamine, and 60.1g of silica sol (30%) were mixed and stirred in sequence, and then 30.1g of carbonamide was weighed and added to the mixed solution, and stirred rapidly for 1h. The mixed solution was introduced into a stainless steel reactor, heated to 165℃ at 10℃ / min, and crystallized dynamically (100rpm) for 72h. After the crystallization reaction was completed, the reactor was quickly cooled to room temperature, and the formed crystals were washed and centrifuged to a pH value of 7~9. The obtained solid product was dried at 120℃ for 6h and then calcined at 550℃ for 4h to obtain a multi-level porous SAPO-18 molecular sieve. The XRD results are as follows Figure 3 shown.

[0031] Comparative Example 1: Conventional SAPO-18 molecular sieve 219.1g of phosphoric acid (85%), 131.2g of pseudo-boehmite, 928.7g of deionized water, 271.5g of N, N-dimethylisopropyldiamine and 60.1g of silica sol (30%) were mixed in sequence and stirred rapidly for 1h. The mixed solution was introduced into a stainless steel reactor and heated to 165°C at 10°C / min for dynamic crystallization (100rpm) for 72h. After the crystallization reaction was completed, the reactor was quickly cooled to room temperature, the formed crystals were washed and centrifuged to a pH value of 7-9, and the obtained solid product was dried at 120°C for 6h and then calcined at 550°C for 4h to obtain a conventional SAPO-18 molecular sieve. SEM ( Figure 2 ) The results showed that the grain size of conventional SAPO-18 molecular sieve is about 600nm, and compared with the multi-level pore SAPO-18 molecular sieve, there is no mesoporous structure on the grain surface.

[0032] Comparative Example 2: Synthesis of SAPO-34 Molecular Sieve 219.1g of phosphoric acid (85%), 153.8g of pseudo-boehmite, 7.34g of deionized water, 1178g of tetraethylammonium hydroxide (25%) and 90.1g of silica sol (30%) were mixed in sequence and stirred rapidly for 1h. The mixed solution was introduced into a stainless steel reactor and heated to 200℃ at 10℃ / min for static crystallization for 48h. After the crystallization reaction was completed, the reactor was quickly cooled to room temperature, the formed crystals were washed and centrifuged to a pH value of 7-9, and the obtained solid product was dried at 120℃ for 6h and then calcined at 550℃ for 4h to obtain SAPO-34 molecular sieve.

[0033] Test example: Catalyst activity evaluation A micro-fixed bed catalytic reaction evaluation device was used to test the catalytic activity and product selectivity of the molecular sieves described in Example 1 of the representative multi-level pore structure of SAPO-18 molecular sieve, Comparative Example 1 of the conventionally synthesized SAPO-18 molecular sieve, and Comparative Example 2 of the conventionally synthesized SAPO-34 molecular sieve. 1g of 20-40 mesh catalyst was weighed and placed in the middle of a reaction tube with a diameter of 1cm, and 10-20 mesh quartz sand was filled at both ends to fix the position of the catalyst in the reaction tube, and then the reaction tube was placed in the middle of a heating furnace and fixed, and thermocouples were inserted in both the heating furnace and the reaction tube. Nitrogen was introduced and the reaction tube was heated to a reaction temperature of 500°C at a heating rate of 3°C / min, and the temperature was kept constant for 30min. Then the nitrogen was turned off, the 1-butene tank was opened, pure 1-butene was introduced, and a stopwatch was used to time the flow of pure 1-butene, and a mass controller was used to control the flow of pure 1-butene. A heating tape was wrapped between the 1-butene tank and the mass flow controller to ensure that 1-butene existed in a gaseous state during the reaction. The temperature of the heating tape was controlled by a thermostat, and the distribution of the reaction products at 3 min, 5 min, 10 min, 15 min, 20 min and 25 min was quantitatively measured online by gas chromatography. The results are shown in the figure. Figure 4 As shown in Table 1 below.

[0034] Table 1:

[0035] The above experimental results show that compared with conventionally synthesized SAPO-18 molecular sieves and SAPO-34 molecular sieves, the multi-level pore SAPO-18 molecular sieve synthesized by the present invention has higher butene conversion rate, propylene selectivity and reaction activity. At the same time, the multi-level pore molecular sieve synthesized by this scheme can also be used in other processes in the fields of petrochemicals, coal chemicals and fine chemicals.

[0036] Finally, it should be noted that the above is only a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the aforementioned embodiments, it is still possible for those skilled in the art to modify the technical solutions described in the aforementioned embodiments or to make equivalent substitutions for some of the technical features therein. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for synthesizing a multi-level porous SAPO-18 molecular sieve, wherein the molecular sieve is synthesized from a silicon source, an aluminum source, a phosphorus source, a template agent, deionized water and a pore-forming agent by a one-step method; in, The silicon source is calculated as SiO2, the aluminum source is calculated as Al2O3, the phosphorus source is calculated as P2O5, R is a template agent, and T is a pore-forming agent; that is, the molar ratio of SiO2:Al2O3:P2O5:R:H2O:T is 0.1~1.5:1:0.8~1.5:1.5~3.0:30~100:0.5~3.

2. The method for synthesizing the multi-level pore SAPO-18 molecular sieve according to claim 1, characterized in that: The following steps are involved: Step S1: at room temperature, after fully stirring deionized water and phosphoric acid according to the above molar ratio to form a transparent solution, the aluminum source and the silicon source are sequentially added and fully stirred to form a white emulsion, and the template is added and fully stirred to obtain a mixed solution; Step S2: adding the pore-forming agent to the mixed solution obtained in step S1, stirring evenly, and aging to form a synthetic sol; Step S3: placing the synthetic sol prepared in step S2 into a crystallization kettle to perform a dynamic hydrothermal reaction; Step S4: washing, centrifuging, drying and calcining the synthetic solution after the reaction in step S3 to obtain hierarchical pore SAPO-18 molecular sieve raw powder.

3. The method for synthesizing the multi-level pore SAPO-18 molecular sieve according to claim 2, characterized in that: In step S1, the silicon source SiO2 is selected from one or more of white carbon black, silica sol, ethyl orthosilicate and water glass; Alternatively, the aluminum source Al2O3 is selected from one or more of pseudo-boehmite, aluminum isopropoxide, aluminum sol, hydrated aluminum oxide and boehmite; Alternatively, the phosphorus source P2O5 is selected from one or more of phosphoric acid, phosphorous acid, phosphates, and phosphorus oxides; Alternatively, the template agent R is selected from one or more of N,N-dimethylisopropyldiamine, diethylamine, triethylamine, isopropylamine, tetraethylammonium hydroxide and tetraethylammonium bromide.

4. The method for synthesizing the multi-level pore SAPO-18 molecular sieve according to claim 2, characterized in that: In step S1, deionized water and phosphoric acid are fully mixed, and then aluminum source and silicon source are added and fully mixed, and then fully mixed with a template agent to obtain a mixed solution; in step S2, the pore-forming agent is carbonamide.

5. The method for synthesizing the multi-level pore SAPO-18 molecular sieve according to claim 2, characterized in that: In step S3, in the crystallization kettle, the crystallization speed is 100-200 rpm, the crystallization temperature is 150-180° C., and the crystallization time is 48-72 h.

6. The method for synthesizing the multi-level pore SAPO-18 molecular sieve according to claim 2, characterized in that: In step S4, the drying temperature is 80-120° C., and the drying time is 2-12 hours.

7. The method for synthesizing the multi-level pore SAPO-18 molecular sieve according to claim 2, characterized in that: In step S4, the calcination temperature is 450-650° C., and the calcination time is 4-12 hours.

8. The method for synthesizing the multi-level pore SAPO-18 molecular sieve according to claim 2, characterized in that: In step S4, the calcination environment gas is an inert gas selected from one or more of nitrogen and helium.

9. A multi-level pore SAPO-18 molecular sieve prepared by the synthesis method according to any one of claims 1 to 8, characterized in that: The molecular sieve has microporous and mesoporous structures; its specific surface area is 480~580m 2 / g, and its pore volume is 0.31~0.48cm 3 / g.

10. Use of the multi-level pore SAPO-18 molecular sieve according to claim 9 in the catalytic cracking of C4 olefins to produce propylene.

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