Phosphorus-containing FER molecular sieve and preparation method thereof

Abstract

The invention discloses a phosphorus-containing FER molecular sieve which is characterized in that the mass fraction of bulk phase P2O5 of the molecular sieve is greater than 0.1%; the molecular sieve is characterized by 29Si MAS NMR after being aged by 100% water vapor at 800 DEG C for 17 hours, the area ratio of a characteristic peak of 116ppm to a characteristic peak of 112ppm of the molecular sieve is less than 1, the molecular sieve is characterized by 27Al MAS NMR, only the characteristic peak of 54ppm exists, the characteristic peak of 0ppm does not exist, and the molecular sieve is characterized by 31P MAS NMR, only the characteristic peaks of 3ppm, 0ppm and-32ppm exist.

Description

Technical Field

[0001] This invention relates to a molecular sieve and its preparation method, and more particularly to a phosphorus-containing FER molecular sieve and its preparation method. Background Technology

[0002] The framework of FER-structured molecular sieves contains 0.42 nm × 0.54 nm ten-membered ring channels (along the

[001] direction) and 0.35 nm × 0.48 nm eight-membered ring channels (along the

[010] direction), which intersect and are layered together. Additionally, there are six-membered ring channels parallel to the ten-membered ring channels, which intersect with the eight-membered ring channels to form a small cage (0.6-0.7 nm in diameter). Due to its unique pore structure, the FER-structured molecular sieve exhibits good shape selectivity, thus possessing the potential to improve the selectivity of low-carbon olefins in catalytic cracking products.

[0003] CN109110779A discloses a method for preparing ZSM-35 molecular sieves. The method involves mixing a silicon source, an aluminum source, an alkali, water, and two organic template agents (a first and a second type) to form a gel, followed by hydrothermal crystallization, filtration, washing, drying, and calcination to obtain the ZSM-35 molecular sieve. The ZSM-35 molecular sieve has a plate-like structure along the c-axis, but the silicon-to-aluminum ratio is not specified. The first organic template agent is an amine compound, preferably ethylenediamine, cyclohexylamine, or butanediamine; the second organic template agent is a six-membered heterocyclic compound, preferably a nitrogen-containing six-membered heterocyclic compound, more preferably pyridine or piperidine.

[0004] CN1288083C discloses a method for preparing magnesium alkali zeolite (FER) via vapor phase transport (VPT). The method involves preparing a gel from a mixture containing an alkali metal (M) source, an oxide source of a trivalent element (X), an oxide source of a tetravalent element (Y), and water. After dehydration to obtain a dry gel, the gel is subjected to a vapor phase of tetrahydrofuran (THF) / water (H₂O) at 100–200 °C to obtain the zeolite product. This method can reduce the amount of template agent used, lower the reaction temperature, and improve the crystallinity of the product. Summary of the Invention

[0005] The inventors discovered that hydrothermal synthesis of phosphorus-containing FER-structured molecular sieves with a low water-to-silica ratio can omit the filtration step, thereby reducing phosphorus loss. Moreover, the prepared phosphorus-containing FER-structured molecular sieves possess unique physicochemical and morphological characteristics. Based on this, the present invention was developed.

[0006] Therefore, the purpose of this invention is to provide a phosphorus-containing FER molecular sieve with NMR phosphorus spectrum, aluminum spectrum, and silicon spectrum characterization characteristics that are different from those of the prior art, and to provide a preparation method thereof. This preparation method can overcome the problem of phosphorus loss that occurs when preparing phosphorus-containing FER structure molecular sieves in the prior art.

[0007] To achieve the above-mentioned objectives of this invention, this invention provides a phosphorus-containing FER molecular sieve, characterized in that the mass fraction of P2O5 in the bulk phase of the molecular sieve is greater than 0.1%; the molecular sieve is aged at 800°C for 17 hours with 100% steam to achieve the desired properties. 29 Si MAS NMR characterization showed that the area ratio of its characteristic peak at -116 ppm to that at -112 ppm was less than 1. 27 Al MASNMR characterization showed only a characteristic peak at 54 ppm and no characteristic peak at 0 ppm. 31 PMAS NMR characterization showed only characteristic peaks at 3 ppm, 0 ppm, and -32 ppm.

[0008] To achieve the above-mentioned objectives of the present invention, the present invention also provides a method for preparing phosphorus-containing FER molecular sieves, characterized in that the method includes: crushing and mixing silicon-aluminum microspheres and inorganic alkali in a pulverizer; adding a phosphorus source and stirring evenly; then adding a template agent and water and stirring evenly to obtain a mixture to be crystallized; crystallizing the mixture to be crystallized in a closed reaction vessel to obtain a crystallized product and recovering the phosphorus-containing FER molecular sieve, wherein, based on the molar ratio of oxides, the molar ratio of silicon to aluminum in the mixture to be crystallized is (10-30):1, the molar ratio of water to silicon is <2.0, the molar ratio of template agent to silicon is >0.2, silicon is calculated as SiO2, and aluminum is calculated as Al2O3.

[0009] The phosphorus-containing FER molecular sieve provided by this invention, after being hydrothermally aged at 800℃ and 100% steam for 17 hours (i.e., the aged sample), is used to... 29 Si MAS NMR characterization showed that the area ratio of the characteristic peak at -116 ppm to that at -112 ppm was less than 1, preferably 0.5 to 0.8; 27 Al MAS NMR characterization still showed only a characteristic peak at 54 ppm and no characteristic peak at 0 ppm; 31 PMAS NMR characterization showed only characteristic peaks at 3 ppm, 0 ppm, and -32 ppm.

[0010] The phosphorus-containing FER molecular sieve provided by this invention has a bulk P2O5 mass fraction of greater than 0.1%, preferably 0.5-3.5%.

[0011] In the preparation method provided by the present invention, the phosphorus-aluminum molar ratio in the mixture to be crystallized is (0.1-1):1, with phosphorus calculated as P2O5 and aluminum calculated as Al2O3.

[0012] In the preparation method provided by this invention, the silicon-aluminum microspheres are purchased from Qingdao Meigao Chemical Co., Ltd., with a silicon-aluminum ratio of 20-30.

[0013] In the preparation method of phosphorus-containing FER molecular sieve provided by the present invention, the phosphorus source is at least one selected from phosphoric acid, hypophosphoric acid, diammonium hydrogen phosphate, and ammonium hypophosphoric acid.

[0014] In the preparation method of phosphorus-containing FER molecular sieve provided by the present invention, the template agent is at least one selected from pyrrolidine, n-butylamine, pyridine, and piperidine.

[0015] In the preparation method of phosphorus-containing FER molecular sieve provided by the present invention, the molar ratio of silicon to aluminum in the mixture to be crystallized is (20-30):1, the molar ratio of water to silicon is (1-1.5):1, the molar ratio of template agent to silicon is 0.5-0.8, and the molar ratio of phosphorus to aluminum is (0.1-1):1.

[0016] In the preparation method of phosphorus-containing FER molecular sieve provided by the present invention, the crystallization treatment is carried out under the conditions of temperature 120-190℃ and time 2-72 hours.

[0017] Compared with existing technologies, the preparation method provided by this invention is simple, saves water resources, and can synthesize phosphorus-containing FER structured molecular sieves in one step.

[0018] Compared with the prior art, the phosphorus-containing FER structure molecular sieve provided by the present invention contains phosphorus in the bulk phase and has good hydrothermal structural stability. The bulk phase contains only framework aluminum and no non-framework aluminum. After hydrothermal aging, the bulk phase also contains only framework aluminum. Attached Figure Description

[0019] Figure 1 These are the XRD spectra of sample PFER-1 from Example 1 and the XRD spectra of sample DP-1 from the comparative example.

[0020] Figure 2 It is sample PFER-1 from Example 1. 29 Si MAS NMR spectrum.

[0021] Figure 3 It is sample PFER-1 from Example 1. 27 Al MAS NMR spectrum.

[0022] Figure 4 It is sample PFER-1 from Example 1. 31 P MAS NMR spectrum.

[0023] Figure 5 Comparative sample DP-1 29 Si MAS NMR spectrum.

[0024] Figure 6 It is the comparative sample DP-1 27 Al MAS NMR spectrum.

[0025] Figure 7 It is the comparative sample DP-1 31 P MAS NMR spectrum. Detailed Implementation

[0026] The present invention will be further illustrated by the following embodiments, but these embodiments do not limit the scope of the invention.

[0027] In the examples and comparative examples, the phosphorus-containing FER molecular sieve samples were referred to as fresh samples, while the fresh samples were referred to as aged samples after being hydrothermally aged at 800°C and 100% steam for 17 hours.

[0028] Examples 1-3 illustrate the preparation of the molecular sieve provided by the present invention and the obtained phosphorus-containing FER molecular sieve.

[0029] Example 1

[0030] Weigh 25g of silicon-aluminum microspheres (Qingdao Meigao Chemical Co., Ltd., silicon-aluminum molar ratio 25) and 1.75g ​​of sodium hydroxide, crush and mix them in a pulverizer, and then put the mixture into a reaction vessel; add 1.13g of H3PO4 (85wt%) dropwise and stir evenly with a glass rod; add 11.19g of pyrrolidine and 2.81g of water dropwise and stir evenly with a glass rod, then transfer the reaction vessel to a crystallization oven and statically crystallize at 150℃ for 48h to obtain a phosphorus-containing FER molecular sieve sample, denoted as PFER-1.

[0031] The XRD pattern of sample PFER-1 is shown below. Figure 1 Legend of PFER-1.

[0032] Fresh and aged samples of PFER-1 29 The Si MAS NMR spectrum is shown below. Figure 2 .

[0033] Fresh and aged samples of PFER-1 27 The Al MAS NMR spectrum is shown below. Figure 3 .

[0034] Fresh and aged samples of PFER-1 31 The PMAS NMR spectrum is shown below. Figure 4 .

[0035] The mass fraction of P2O5 in the bulk phase of sample PFER-1 was 3.3%. The aged sample of PFER-1 was... 29 Si MAS NMR characterization showed that the area ratio of the characteristic peak at -116 ppm to that at -112 ppm was 0.65. 27Al MAS NMR characterization showed only a characteristic peak at 54 ppm and no characteristic peak at 0 ppm. 31 PMAS NMR characterization showed only characteristic peaks at 3 ppm, 0 ppm, and -32 ppm.

[0036] Comparative Example 1

[0037] 1.75 g of diammonium hydrogen phosphate was added to 50.68 g of deionized water and stirred until homogeneous. Then, 1.31 g of sodium hydroxide was added and stirred until homogeneous. Next, 1.35 g of sodium aluminate was added and stirred until homogeneous. Then, 2.83 g of pyrrolidine was added and stirred until homogeneous. Finally, 17 g of solid silica gel was added and stirred until homogeneous to obtain the mixture to be crystallized. The mixture was transferred to a reaction vessel and placed in a rotary oven at 150 °C for 48 h to crystallize. The resulting product was the FER molecular sieve comparison sample, denoted as DP-1.

[0038] The XRD pattern of sample DP-1 is shown below. Figure 1 Legend of DP-1 in the diagram.

[0039] Comparison of fresh and aged samples of DP-1 29 The Si MAS NMR spectrum is shown below. Figure 5 The peak area ratio of -116ppm to -112ppm for the aged sample was 1.1.

[0040] Comparison of fresh and aged samples of DP-1 27 The Al MAS NMR spectrum is shown below. Figure 6 The aluminum skeleton is reduced and transformed into twisted aluminum skeleton and outer aluminum skeleton.

[0041] Comparison of fresh and aged samples of DP-1 31 The PMAS NMR spectrum is shown below. Figure 7 Neither the fresh nor the aged samples showed any phosphorus signal, indicating that phosphorus is lost after conventional hydrothermal synthesis.

[0042] Compared with the fresh sample DP-1, the bulk phase P2O5 mass fraction was 0.073%, indicating that the bulk phase of the FER molecular sieve synthesized by conventional liquid phase with phosphorus in Comparative Example 1 was basically free of phosphorus, and phosphorus was lost.

[0043] Example 2

[0044] Weigh 15g of silica-alumina microspheres and 1.05g of sodium hydroxide, crush and mix them in a pulverizer, and then put the mixture into a reaction vessel. Add 0.68g of H3PO4 (85wt%) dropwise and stir evenly with a glass rod. Add 9.40g of pyrrolidine and 1.68g of water dropwise and stir evenly with a glass rod. Transfer the reaction vessel to a crystallization oven and statically crystallize at 150℃ for 48h to obtain a phosphorus-containing FER molecular sieve sample, denoted as PFER-2.

[0045] The XRD pattern of sample PFER-2 has Figure 1 The PFER-1 diagram has the same features.

[0046] Fresh and aged samples of PFER-2 29 Si MAS NMR spectrum and Figure 2 Having the same characteristics, fresh and aged samples of PFER-2 27 Al MAS NMR spectrum and Figure 3 Having the same characteristics, fresh and aged samples of PFER-2 31 pMAS NMR spectrum and Figure 4 They have the same characteristics.

[0047] The fresh PFER-2 sample had a bulk P2O5 mass fraction of 3.2%, while the aged PFER-2 sample had a P2O5 mass fraction of 3.2%. 29 SiMAS NMR characterization showed that the area ratio of the characteristic peak at -116 ppm to that at -112 ppm was 0.63. 27 Al MAS NMR characterization showed only a characteristic peak at 54 ppm and no characteristic peak at 0 ppm. 31 PMAS NMR characterization showed only characteristic peaks at 3 ppm, 0 ppm, and -32 ppm.

[0048] Example 3

[0049] Weigh 35g of silica-alumina spheres and 2.45g of sodium hydroxide, crush and mix them in a pulverizer, and then put the mixture into a reaction vessel. Add 1.58g of H3PO4 (85wt%) and stir evenly with a glass rod. Add 11.19g of pyrrolidine (99wt%) and 3.93g of water and stir evenly with a glass rod. Transfer the reaction vessel to a crystallization oven and statically crystallize at 150℃ for 48h to obtain phosphorus-containing FER molecular sieve, denoted as PFER-3.

[0050] Fresh and aged samples of PFER-3. 29 Si MAS NMR spectrum and Figure 2 Having the same characteristics, fresh and aged samples of PFER-3 27 Al MAS NMR spectrum and Figure 3 Having the same characteristics, fresh and aged samples of PFER-3 31 pMAS NMR spectrum and Figure 4 They have the same characteristics.

[0051] The fresh sample PFER-3 has a bulk P2O5 mass fraction of 3.0%. The aged sample PFER-3, with... 29 SiMAS NMR characterization showed that the area ratio of the characteristic peak at -116 ppm to that at -112 ppm was 0.64. 27 Al MAS NMR characterization showed only a characteristic peak at 54 ppm and no characteristic peak at 0 ppm. 31 PMAS NMR characterization showed only characteristic peaks at 3 ppm, 0 ppm, and -32 ppm.

Claims

1. A phosphorus-containing FER molecular sieve, characterized in that, The molecular sieve has a bulk P2O5 mass fraction greater than 0.1%; after aging with 100% water vapor at 800℃ for 17 hours, the molecular sieve... 29 Si MAS NMR characterization showed that the area ratio of its characteristic peak at -116 ppm to that at -112 ppm was less than 1. 27 Al MAS NMR characterization showed only a characteristic peak at 54 ppm and no characteristic peak at 0 ppm. 31 PMAS NMR characterization showed only characteristic peaks at 3 ppm, 0 ppm, and -32 ppm.

2. The molecular sieve according to claim 1, characterized in that, by 29 Si MAS NMR characterization showed that the area ratio of the characteristic peak at -116 ppm to that at -112 ppm was 0.5–0.

8.

3. The molecular sieve according to claim 1, characterized in that, The mass fraction of P2O5 in the bulk phase of this molecular sieve is 0.5%–3.5%.

4. A method for preparing a phosphorus-containing FER molecular sieve, characterized in that, The method includes: crushing and mixing silicon-aluminum microspheres and inorganic alkali in a pulverizer; adding a phosphorus source and stirring evenly; adding a template agent and water and stirring evenly to obtain a mixture to be crystallized; crystallizing the mixture to be crystallized in a closed reactor to obtain a crystallized product and recovering phosphorus-containing FER molecular sieves, wherein, based on the molar ratio of oxides, the molar ratio of silicon to aluminum in the mixture to be crystallized is (10-30):1, the molar ratio of water to silicon is <2.0, the molar ratio of template agent to silicon is >0.2, silicon is calculated as SiO2, and aluminum is calculated as Al2O3.

5. The preparation method according to claim 4, characterized in that, In the mixture to be crystallized, the phosphorus-aluminum molar ratio is (0.1-1):1, with phosphorus calculated as P2O5 and aluminum calculated as Al2O3.

6. The preparation method according to claim 4, characterized in that, The silicon-aluminum microspheres have a silicon-to-aluminum molar ratio of 10-30, where silicon is calculated as SiO2 and aluminum as Al2O3.

7. The preparation method according to claim 4, characterized in that, The phosphorus source is at least one selected from phosphoric acid, hypophosphoric acid, diammonium hydrogen phosphate, and ammonium hypophosphoric acid.

8. The preparation method according to claim 4, characterized in that, The template agent is at least one selected from pyrrolidine, n-butylamine, pyridine, and piperidine.

9. The preparation method according to claim 4, characterized in that, In the mixture to be crystallized, the molar ratio of silicon to aluminum is (20-30):1, the molar ratio of water to silicon is (1-1.5):1, the molar ratio of template agent to silicon is 0.5-0.8, and the molar ratio of phosphorus to aluminum is (0.1-1):

1.

10. The preparation method according to claim 4, characterized in that, The crystallization treatment is performed at a temperature of 120-190°C for a time of 2-72 hours.

Images