A method for preparing SAPO-34 molecular sieve

Abstract

The invention discloses a preparation method of a SAPO 34 molecular sieve, the preparation method including:Sucrose is dissolved in water to form an aqueous solution;Aluminum source, silicon source, phosphorus source, template and water are added to the aqueous solution obtained by step (1) and mixed uniformly, stirring, forming a mixture;Polyoxyethylene polyoxypropylene octadecyl alcohol ether is added to the mixture, and crystallization is carried out after rapid mixing to obtain a molecular sieve stock solution, wherein the addition amount of the polyoxyethylene polyoxypropylene octadecyl alcohol ether is 0.1~20wt% by weight of the aluminum source 100%;The molecular sieve stock solution is filtered, dried, and roasted to obtain a SAPO 34 molecular sieve. The SAPO 34 molecular sieve prepared by the present invention has a higher SAPO 34 catalytic life, is conducive to reducing the carbon deposition rate, and prolongs the life of the active component SAPO 34 molecular sieve in the organic reaction.

Description

Technical Field

[0001] The present invention relates to a method for preparing a molecular sieve, in particular to a method for preparing a SAPO-34 molecular sieve. Background Art

[0002] SAPO-34 molecular sieve is used in the fields of petroleum refining and chemical engineering because of its special pore size and regular pore structure, as well as its strong proton acidity. The SAPO-34 framework is mainly composed of silicoaluminophosphate, with an ellipsoidal CHA cage composed of double six-membered rings, eight-membered rings and four-membered rings, and a three-dimensional cross-pore structure, which has excellent selectivity. However, the chemical bond polarity of SAPO-34 is strong, and the acidity is relatively high, so it is easy to be deactivated by carbon deposition during the reaction of some carbon-based acids.

[0003] SAPO-34 has a 0.38nm transparent channel and a unique cage structure. The micropores are conducive to shape-selective catalytic reactions; however, the acid centers are unevenly distributed in the cage channels. During the acid center reaction, if the acid centers are too concentrated, the acidity will be too strong, the dehydrogenation reaction will be more intense, and the rate of hydrogen transfer will not keep up with the rate of electron loss of carbon atoms, which will easily produce carbon deposition; on the contrary, if the acid center distribution is reasonable, the intensity of the reaction will decrease, and the rate of carbon deposition will be further reduced. At present, domestic and foreign studies have been conducted on SAPO-34 molecular sieves, and SAPO-34 molecular sieves with excellent performance have been prepared. Relevant experimental data show that SAPO-34 molecular sieves with benign acid distribution are conducive to inhibiting excessive cracking reactions, and the catalytic life of SAPO-34 molecular sieves can be effectively extended.

[0004] Chinese patent CN107673370A provides a method for synthesizing nano SAPO-34 molecular sieves. The acidity is regulated by adding an organosilane template during hydrothermal synthesis. The resulting SAPO-34 molecular sieve catalyst exhibits excellent catalytic performance in the MTO reaction, significantly prolongs the catalyst life, and improves the selectivity of light olefins. However, the organosilane template used in this technology is too expensive.

[0005] Chinese patent CN108892152A provides a method for preparing SAPO-34 molecular sieves, which is prepared by obtaining a carbon-based aluminum compound by roasting sucrose and an aluminum source, and has improved utilization of active acid centers and improved selectivity for ethylene and propylene. However, the preparation process of this technology is complicated.

[0006] Chinese patent CN110342539A provides a method for preparing SAPO-34 molecular sieves, which synthesizes multi-level porous SAPO-34 molecular sieves by using soft templates such as sugars, and the interaction between the SAPO-34 molecular sieve and the inorganic precursor is enhanced, which is conducive to the template effect and effectively introduces uniform multi-level channels. The method of the present invention introduces mesopores into the microporous SAPO-34 molecular sieve, thereby improving the catalytic efficiency of the SAPO-34 molecular sieve catalyst; however, the technology uses a large amount of soft templates. Summary of the invention

[0007] The object of the present invention is to provide a method for preparing SAPO-34 molecular sieve, which increases the life of SAPO-34 molecular sieve in catalytic reaction by optimizing the specific surface area and acidity of SAPO-34 molecular sieve; the acid position can also be regulated in the catalyst material, and the carbon deposition rate can be reduced in a series of reactions with acid centers as active sites.

[0008] To achieve the above object, the present invention provides a method for preparing SAPO-34 molecular sieve, which comprises the following steps:

[0009] (1) dissolving sucrose in water to form an aqueous solution;

[0010] (2) adding an aluminum source, a silicon source, a phosphorus source, a template and water to the aqueous solution obtained in step (1), mixing evenly, and stirring to form a mixture;

[0011] (3) adding polyoxyethylene polyoxypropylene octadecyl alcohol ether to the mixture obtained in step (2), rapidly mixing and then crystallizing to obtain a molecular sieve stock solution;

[0012] (4) filtering, drying and calcining the molecular sieve stock solution obtained in step (3) to obtain SAPO-34 molecular sieve;

[0013] Wherein, in step (3), based on 100% by weight of the aluminum source, the amount of polyoxyethylene polyoxypropylene octadecyl alcohol ether added is 0.1 to 20 wt%.

[0014] In the preparation method of SAPO-34 molecular sieve of the present invention, based on 100% weight of the aluminum source, the added amount of sucrose is 0.1-4.9wt%.

[0015] In the preparation method of SAPO-34 molecular sieve of the present invention, the polyoxyethylene polyoxypropylene octadecyl alcohol ether can be added to the aqueous solution in step (1), or can be added after mixing with the silicon source in step (2), or can be added in step (3). The adding method is not limited to the above three or more combinations.

[0016] In the preparation method of SAPO-34 molecular sieve of the present invention, the aluminum source is selected from one or more of pseudo-boehmite, aluminum sulfate, boehmite and alumina.

[0017] In the preparation method of SAPO-34 molecular sieve of the present invention, the silicon source is selected from one or more of active silicon dioxide, white carbon black, sodium silicate, ethyl orthosilicate, silica sol, water glass and white carbon black.

[0018] In the preparation method of SAPO-34 molecular sieve of the present invention, the template agent is selected from one or more of diethylamine, triethylamine, morpholine, diisopropylamine, di-n-propylamine, diethanolamine, triethanolamine, tetraethylammonium hydroxide and N,N-diethylethanolamine.

[0019] In the preparation method of SAPO-34 molecular sieve of the present invention, in step (2), the molar ratio of silicon source: aluminum source: phosphorus source: template: water is (1-2): (2-4): (0.2-2): (1-6): (90-180).

[0020] In the method for preparing SAPO-34 molecular sieve of the present invention, in step (3), the crystallization temperature is 40 to 400° C., and the crystallization time is 0 to 14400 min.

[0021] In the method for preparing SAPO-34 molecular sieve of the present invention, in step (4), the operating conditions of the drying and the calcining are not particularly limited, and conventional operations in the art may be used.

[0022] The SAPO-34 molecular sieve prepared by the present invention has a higher SAPO-34 catalytic life, is beneficial to reducing the carbon deposition rate, and prolongs the life of the SAPO-34 molecular sieve, which is an active component in the organic reaction.

[0023] The preparation method of the present invention adds a nonionic surfactant polyoxyethylene polyoxypropylene octadecyl alcohol ether as an acid site regulator before the SAPO-34 molecular sieve is crystallized, so that the dispersion of the colloidal silicon source is higher, thereby obtaining the effect of regulating the acidity and achieving the purpose of enhancing the catalytic life of the SAPO-34 molecular sieve.

[0024] According to the preparation method of the present invention, the polyoxyethylene polyoxypropylene octadecyl alcohol ether has certain steric hindrance, can regulate the relative distance of the acid sites inside the molecular sieve, and can also increase the pore volume of the molecular sieve.

[0025] The preparation method of the present invention, due to the presence of low-content sucrose, uses sucrose as a pore and acid site regulator, so that the molecular sieve crystals generate certain pores during the roasting process, thereby increasing the specific surface area and pore volume of the SAPO-34 molecular sieve.

[0026] The preparation method of the present invention increases the pore volume of the catalyst by utilizing the steric hindrance effect of the polyoxyethylene polyoxypropylene octadecyl alcohol ether molecules, and combines a small amount of sucrose as a hydroxyl compound to provide hydroxyl sites, thereby synthesizing a SAPO-34 molecular sieve with a long life and excellent acid distribution. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] 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 embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only 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.

[0028] Figure 1 The XRD diffraction pattern of the molecular sieve obtained in the example is compared with the XRD diffraction pattern of the molecular sieve obtained in the comparative example.

[0029] Figure 2 The graph is a graph showing the change in methanol conversion rate over time in the MTO catalytic reaction of the molecular sieve obtained in the example and the molecular sieve obtained in the comparative example.

[0030] Figure 3 NH of Example 1 and Comparative Example 1 3 -TPD graph.

[0031] Figure 4 This is a scanning electron microscope image of the SAPO-34 molecular sieve of Example 1. DETAILED DESCRIPTION

[0032] In order to better illustrate the present invention, the present invention is further described below in conjunction with specific embodiments. However, the scope of the present invention is not limited to the scope of these embodiments. In the present invention, wt% is mass percentage.

[0033] Analysis and determination methods:

[0034] The specific surface area and pore volume were measured using a Quantachrome autosorb-analyzer.

[0035] The size and morphology were observed using a Bruker scanning electron microscope.

[0036] X-ray diffraction analysis was carried out on a D / max-2200PC X-ray diffractometer from Rigaku Corporation.

[0037] The following examples are provided for further explanation, but are not limited to the examples.

[0038] Embodiment 1:

[0039] (1) Weigh 0.4 g of sucrose and dissolve it in 51.32 g of deionized water;

[0040] (2) Add 11.25 g of pseudo-boehmite, 15.75 g of phosphoric acid, and 5.96 g of silica sol to the solution obtained in step (1), mix well, and stir for 1 hour;

[0041] (3) adding 9.82 g of diethylamine to the solution obtained in step (2), and then adding 65.10 g of deionized water, and stirring thoroughly to obtain a uniform mixture;

[0042] (4) 1.91 g of polyoxyethylene polyoxypropylene octadecyl alcohol ether and 6.0 g of deionized water were thoroughly mixed;

[0043] (5) adding the mixed solution obtained in step (4) to the mixture in step (3) and stirring rapidly, then transferring to a stainless steel kettle lined with polytetrafluoroethylene, and placing in an oven at 185° C. for crystallization for 4041 min to obtain a crystallized solution;

[0044] (6) The crystallized liquid in the centrifugal separation step (5) is dried at 110° C. for 3 h, and then the crystals are placed in a muffle furnace and calcined at 550° C. for 5 h to obtain a high-life SAPO-34 molecular sieve Z-1.

[0045] Embodiment 2:

[0046] (1) Weigh 0.5 g of sucrose and dissolve it in 51.32 g of deionized water;

[0047] (2) Add 8.34 g of aluminum oxide, 15.75 g of phosphoric acid, and 7.38 g of water glass to the solution obtained in step (1), mix well, and stir for 1 hour;

[0048] (3) adding 13.67 g of triethylamine and 1.13 g of diethylamine to the solution obtained in step (2), and then adding 63.20 g of deionized water, and stirring thoroughly to obtain a uniform mixture;

[0049] (4) 0.31 g of polyoxyethylene polyoxypropylene octadecyl alcohol ether and 6.0 g of deionized water were thoroughly mixed;

[0050] (5) adding the mixed solution obtained in step (4) to the mixture in step (3) and stirring rapidly, then transferring to a stainless steel kettle lined with polytetrafluoroethylene, and placing in an oven at 180° C. for crystallization for 5041 min to obtain a crystallized solution;

[0051] (6) The crystallized liquid in the centrifugal separation step (5) is dried at 110° C. for 3 h, and then the crystals are placed in a muffle furnace and calcined at 550° C. for 5 h to obtain a high-life SAPO-34 molecular sieve Z-2.

[0052] Embodiment 3:

[0053] (1) Weigh 0.3 g of sucrose and dissolve it in 51.32 g of deionized water;

[0054] (2) Add 11.25 g of boehmite, 15.75 g of phosphoric acid, and 9.45 g of silica sol to the solution obtained in step (1), mix well, and stir for 1 hour;

[0055] (3) adding 9.82 g of diethylamine to the solution obtained in step (2), and then adding 65.10 g of deionized water, and stirring thoroughly to obtain a uniform mixture;

[0056] (4) 0.65 g of polyoxyethylene polyoxypropylene octadecyl alcohol ether and 6.0 g of deionized water were thoroughly mixed;

[0057] (5) adding the mixed solution obtained in step (4) to the mixture in step (3) and stirring rapidly, then transferring to a stainless steel kettle lined with polytetrafluoroethylene, and placing in an oven at 187° C. for crystallization for 4341 min to obtain a crystallized solution;

[0058] (6) The crystallized liquid in the centrifugal separation step (5) is dried at 110° C. for 3 h, and then the crystals are placed in a muffle furnace and calcined at 550° C. for 5 h to obtain a high-life SAPO-34 molecular sieve Z-3.

[0059] Embodiment 4:

[0060] (1) Weigh 0.4 g of sucrose and dissolve it in 51.32 g of deionized water;

[0061] (2) Add 10.0 g of γ-alumina, 15.75 g of phosphoric acid, and 7.75 g of sodium silicate to the solution obtained in step (1), mix well, and stir for 1 hour;

[0062] (3) adding 9.82 g of diethylamine to the solution obtained in step (2), and then adding 65.10 g of deionized water, and stirring thoroughly to obtain a uniform mixture;

[0063] (4) 1.35 g of polyoxyethylene polyoxypropylene octadecyl alcohol ether and 6.0 g of deionized water were thoroughly mixed;

[0064] (5) adding the mixed solution obtained in step (4) to the mixture in step (3) and stirring rapidly, then transferring to a stainless steel kettle lined with polytetrafluoroethylene, and placing in an oven at 190° C. for crystallization for 4241 min to obtain a crystallized solution;

[0065] (6) The crystallized liquid in the centrifugal separation step (5) is dried at 110° C. for 3 h, and then the crystals are placed in a muffle furnace and calcined at 550° C. for 5 h to obtain a high-life SAPO-34 molecular sieve Z-4.

[0066] Embodiment 5:

[0067] (1) Weigh 0.5 g of sucrose and dissolve it in 51.32 g of deionized water;

[0068] (2) Add 11.25 g of pseudo-boehmite, 15.34 g of phosphoric acid, and 5.96 g of silica sol to the solution obtained in step (1), mix well, and stir for 1 hour;

[0069] (3) adding 40.32 g of tetraethylammonium hydroxide to the solution obtained in step (2), and then adding 35.20 g of deionized water, and stirring thoroughly to obtain a uniform mixture;

[0070] (4) 2.21 g of polyoxyethylene polyoxypropylene octadecyl alcohol ether and 6.0 g of deionized water were thoroughly mixed;

[0071] (5) adding the mixed solution obtained in step (4) to the mixture in step (3) and stirring rapidly, then transferring to a stainless steel kettle lined with polytetrafluoroethylene, and placing in an oven at 186° C. for crystallization for 4441 min to obtain a crystallized solution;

[0072] (6) The crystallized liquid in the centrifugal separation step (5) is dried at 110° C. for 3 h, and then the crystals are placed in a muffle furnace and calcined at 550° C. for 5 h to obtain a high-life SAPO-34 molecular sieve Z-4.

[0073] Comparative Example 1:

[0074] (1) Weigh 0.0 g of sucrose and dissolve it in 51.32 g of deionized water;

[0075] (2) Add 11.25 g of pseudo-boehmite, 15.75 g of phosphoric acid, and 5.96 g of silica sol to the solution obtained in step (1), mix well, and stir for 1 hour;

[0076] (3) adding 9.82 g of diethylamine to the solution obtained in step (2), and then adding 71.10 g of deionized water, and stirring thoroughly to obtain a uniform mixture;

[0077] (4) adding 0.0 g of polyoxyethylene polyoxypropylene octadecyl alcohol ether to the mixture obtained in step (3), stirring rapidly, then transferring to a stainless steel kettle lined with polytetrafluoroethylene, and placing in an oven at 185° C. for crystallization for 4041 min to obtain a crystallized solution;

[0078] (5) The crystallized liquid in the centrifugal separation step (4) was dried at 110° C. for 3 h, and then the crystals were placed in a muffle furnace and calcined at 550° C. for 5 h to obtain SAPO-34 molecular sieve C-1.

[0079] The molecular sieves obtained in the examples and comparative examples were subjected to X-ray diffraction analysis, and the specific surface area and pore volume were measured. The results are as follows: Figure 1 And as shown in Table 1.

[0080] Table 1 Molecular sieve properties

[0081]

[0082] from Figure 1 As can be seen from the results, all peak shapes of the examples and comparative examples are completely standard SAPO-34 spectra, proving that the molecular sieves obtained in the examples and comparative examples are all SAPO-34 molecular sieves. As can be seen from the results in Table 1, the SAPO-34 molecular sieve obtained by the preparation method of the present invention has a higher specific surface area and pore volume than the SAPO-34 molecular sieve of the comparative example.

[0083] Figure 3 NH of Example 1 and Comparative Example 1 3 -TPD graph. Figure 3 It can be seen that the preparation method of the present invention adds polyoxyethylene polyoxypropylene octadecyl alcohol ether and sucrose, and the strong acid peak in the high temperature zone of the obtained SAPO-34 molecular sieve is obviously shifted to the low temperature zone. Figure 4 This is a scanning electron microscope image of the SAPO-34 molecular sieve of Example 1. Figure 4 It can be seen that the molecular sieve crystals synthesized by the preparation method of the present invention present a regular cubic structure that is unique to SAPO-34 molecular sieve.

[0084] Embodiment 6:

[0085] The SAPO-34 molecular sieves obtained in Examples 1-5 and Comparative Example 1 were used in MTO catalytic reactions respectively. The MTO catalytic reactions were carried out in a fixed bed reactor. The raw material for the MTO catalytic reaction was a 75% wt methanol solution. The conversion rate of methanol in the product was analyzed. The change of methanol conversion rate over time in the catalytic reaction is shown in FIG. Figure 2 shown.

[0086] from Figure 2 It can be seen that the SAPO-34 molecular sieve obtained by the preparation method of the present invention has a slower carbon deposition rate and a longer catalytic life than the SAPO-34 molecular sieve of the comparative example.

[0087] Although the present invention has been disclosed as above by way of embodiments, they are not intended to limit the present invention. Any person with common knowledge in the technical field may make some changes and modifications without departing from the spirit and scope of the present invention. Therefore, the protection scope of the present invention shall be based on the scope defined by the attached claims.

Claims

1. A method for preparing SAPO-34 molecular sieve, It is characterized in that The following steps are involved: (1) dissolving sucrose in water to form an aqueous solution; (2) adding an aluminum source, a silicon source, a phosphorus source, a template and water to the aqueous solution obtained in step (1), mixing evenly, and stirring to form a mixture; (3) adding polyoxyethylene polyoxypropylene octadecyl alcohol ether to the mixture obtained in step (2), rapidly mixing and then crystallizing to obtain a molecular sieve stock solution; (4) filtering, drying and calcining the molecular sieve stock solution obtained in step (3) to obtain SAPO-34 molecular sieve; Wherein, in step (3), based on 100% by weight of the aluminum source, the amount of polyoxyethylene polyoxypropylene octadecyl alcohol ether added is 0.1 to 20 wt%; Based on 100% of the weight of the aluminum source, the added amount of sucrose is 0.1-4.9wt%.

2. The preparation method according to claim 1, It is characterized in that The polyoxyethylene polyoxypropylene octadecyl alcohol ether can be added to the aqueous solution in step (1), or added after mixing with the silicon source in step (2), or added in step (3).

3. The preparation method according to claim 1, It is characterized in that The template agent is one or more of diethylamine, triethylamine, morpholine, diisopropylamine, di-n-propylamine, diethanolamine, triethanolamine, tetraethylammonium hydroxide and N,N-diethylethanolamine.

4. The preparation method according to claim 1, It is characterized in that The silicon source is one or more of active silicon dioxide, white carbon black, sodium silicate, ethyl orthosilicate, silica sol, water glass and white carbon black.

5. The preparation method according to claim 1, It is characterized in that The aluminum source is one or more of pseudo-boehmite, aluminum sulfate, boehmite, and alumina.

6. The preparation method according to claim 1, It is characterized in that In step (2), the molar ratio of silicon source: aluminum source: phosphorus source: template: water is (1-2): (2-4): (0.2-2): (1-6): (90-180).

7. The preparation method according to claim 1, It is characterized in that In step (3), the crystallization temperature is 40 to 400° C., and the crystallization time is 0 to 14400 min.

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