A phosphorus- and rare-earth-containing CHA-structured molecular sieve, its preparation method and application

Abstract

This invention relates to a CHA-structured molecular sieve containing phosphorus and rare earth elements and its preparation method. The molecular sieve has a silicon-to-aluminum ratio of 5–50, a phosphorus content of 0.1–10%, and a rare earth metal content of 0.5–10%. After treatment with 100% steam at 800°C for 17 hours, the ratio of tetracoordinated framework aluminum to pentacoordinated non-framework aluminum in the aluminum coordination state of the molecular sieve is 1.0–2.0. The preparation method of this molecular sieve eliminates the alkali metal ion exchange step, produces no ammonia nitrogen wastewater, and exhibits better selectivity and higher reactant conversion rates in the catalytic cracking reaction of light hydrocarbons, particularly for ethylene and propylene.

Description

Technical Field

[0001] This invention relates to a molecular sieve, its preparation method and application, and more specifically to a phosphorus- and rare earth-containing molecular sieve, its preparation method and its application in the catalytic cracking reaction of light hydrocarbons. Background Technology

[0002] Molecular sieves are a class of commercially important crystalline substances, possessing strong acidity, large specific surface area, unique pore structure, and relatively stable physicochemical properties. These characteristics enable molecular sieves to be used as heterogeneous catalysts in many industrial processes. SSZ-13 molecular sieve belongs to the CHA topology, its structure consisting of aluminum-oxygen tetrahedra and silicon-oxygen tetrahedra connected end-to-end by oxygen atoms at the vertices, forming an ellipsoidal cage (0.73 × 1.2 nm) with an eight-membered ring structure and a three-dimensional intersecting pore structure. The pore size is 0.38 × 0.38 nm, classifying it as a small-pore molecular sieve. Due to its small pore size, SSZ-13 molecular sieves are currently widely used in gas separation and shape-selective catalysis.

[0003] The earliest method for synthesizing SSZ-13 molecular sieves was disclosed in US4544538. This method uses N,N,N-trimethyl-1-adamantyl ammonium hydroxide as a template agent. The template agent, silicon source, aluminum source, alkali metal salt, and water are mixed uniformly and hydrothermally crystallized at 100–235°C for more than 3 days to obtain SSZ-13 molecular sieves. Based on this method, new methods for synthesizing SSZ-13 molecular sieves have been continuously disclosed.

[0004] CN101973562A discloses a method for synthesizing SSZ-13 molecular sieves using copper-amine complexes as template agents. The method first dissolves gibbsite in deionized water, adds divalent copper salts, stirs, and then adds an organic amine dropwise to the solution. After thorough stirring, solid sodium hydroxide is added and stirred again. Silica sol is then added to the solution, and after stirring for 2-3 hours, the solution is transferred to a reaction vessel and crystallized at 140-180°C for 3-20 days. After filtration, drying, and calcination, the final product is obtained. Although this method does not use organic ammonium salts as template agents, the resulting SSZ-13 molecular sieve has poor ion exchange performance, which is not conducive to subsequent modification treatment. Furthermore, the Cu-SSZ-13 molecular sieve obtained by this method is mainly used for NO2 in vehicle exhaust. x The removal of the substance.

[0005] CN106824261A provides a method for preparing Ni-SSZ-13 molecular sieve. The method uses nickel salt, chelating agent or nickel amine chelate as template agent, and mixes it with silicon source, aluminum source and water. After crystallization at 100-200℃ for 5h-10 days, the crystallized product is washed with water, dried and calcined to obtain the final product Ni-SSZ-13 molecular sieve.

[0006] CN111592008A provides a method for synthesizing Fe-SSZ-13 molecular sieves in one step using iron salts, chelating agents, or iron-amine complexes as template agents.

[0007] Although there are many reports on methods for synthesizing heteroatom SSZ-13 molecular sieves by introducing other elements during in-situ synthesis, there are few reports on the synthesis of phosphorus- and rare earth-containing SSZ-13 molecular sieves. Generally, the preparation method of phosphorus- and rare earth-containing molecular sieves involves using an equal-volume impregnation method to perform subsequent phosphorus and rare earth modifications on the synthesized molecular sieve. Summary of the Invention

[0008] The purpose of this invention is to provide a phosphorus- and rare-earth-containing CHA-structured molecular sieve that differs from existing technologies, and to provide its preparation method and its application in light hydrocarbon catalytic cracking reactions.

[0009] To achieve the above objectives, a first aspect of the present invention is to provide a CHA-structured molecular sieve containing phosphorus and rare earth elements, wherein the molar ratio of silica to alumina in the molecular sieve is 5 to 50, and the phosphorus content of the molecular sieve is 0.1 to 10% based on P2O5 and the rare earth metal content is 0.5 to 10% based on rare earth oxides and the dry weight of the molecular sieve, wherein the rare earth metal is selected from at least one of lanthanum, cerium, and yttrium; and the ratio of tetracoordinate framework aluminum to pentacoordinate non-framework aluminum content in the aluminum coordination state of the molecular sieve after treatment with 100% steam at 800°C for 17 hours is 1.0 to 2.0, and the aluminum coordination state of the molecular sieve is measured using a solid-state magic angle rotating nuclear magnetic resonance method.

[0010] In the molecular sieve, the preferred molar ratio of silicon dioxide to aluminum oxide is 10-35. Based on P2O5 and the dry weight of the molecular sieve, the preferred phosphorus content of the molecular sieve is 0.5-5%. Based on rare earth oxides and the dry weight of the molecular sieve, the preferred rare earth metal content of the molecular sieve is 1-6%.

[0011] Solid magic angle rotation nuclear magnetic resonance method measured 27In the Al MAS NMR spectrum, the integrated area of ​​the peak with a chemical shift near 60 ppm corresponds to the content of the four-coordinate framework aluminum, the integrated area of ​​the peak with a chemical shift near 30 ppm corresponds to the content of the five-coordinate non-framework aluminum, and the aluminum coordination state of the peak with a chemical shift near 0 ppm is six-coordinate non-framework aluminum. The ratio of the content of the four-coordinate framework aluminum to the content of the five-coordinate framework aluminum is the ratio of the integrated area of ​​the peak with a chemical shift near 60 ppm to the integrated area of ​​the peak with a chemical shift near 30 ppm in the NMR spectrum. After treatment at 800℃ and 100% steam for 17 h, the ratio of the content of the four-coordinate framework aluminum to the content of the five-coordinate non-framework aluminum in the phosphorus and rare earth-containing CHA structure molecular sieve is 1.0–2.0, preferably 1.2–1.8.

[0012] The CHA structure molecular sieve is preferably SSZ-13 molecular sieve.

[0013] To achieve the above objectives, a second aspect of the present invention also provides a method for preparing a phosphorus- and rare-earth-containing CHA molecular sieve, characterized by comprising the following steps:

[0014] (a) Add template agent R, aluminum source and silicon source to deionized water, mix them evenly and then load them into a reaction vessel for pre-crystallization reaction;

[0015] (b) After the pre-crystallization reaction is completed, the gel is removed, and a phosphorus source is added to the gel to obtain mixture I. Mixture I is subjected to a crystallization reaction in a reaction vessel to obtain the initial crystallization product. When the phosphorus source is phosphoric acid, an additive needs to be added. The additive is at least one of ammonia, diethylamine, triethylamine, and choline hydroxide. In the mixture I, the molar ratio of each component is as follows: template agent R: aluminum source: silicon source: phosphorus source: additive: water = 0.4~10:1:5~50:0.1~3:0~5:50~1000, where the aluminum source is calculated as Al2O3, the silicon source as SiO2, and the phosphorus source as P2O5.

[0016] (c) The crystallized primary product is washed, dried, and calcined to obtain a phosphorus-containing molecular sieve;

[0017] (d) The phosphorus-containing molecular sieve is obtained by loading rare earth metals and calcining the phosphorus-containing molecular sieve.

[0018] In the preparation method described above, optionally, the template agent in step (a) is N,N,N-trimethyl-1-adamantyl ammonium hydroxide, and an aqueous solution with a mass fraction of 15-30% is used. Optionally, the aluminum source in step (a) is selected from at least one of SB powder, aluminum alkoxide, alumina, aluminum hydroxide, aluminum sulfate, and gibbsite. Optionally, the silicon source in step (a) is selected from at least one of silica sol, silica, fumed silica, silicates, and solid silica gel. Optionally, the temperature of the pre-crystallization reaction in step (a) is 100-140℃, and the crystallization time is 2-48 hours.

[0019] In the preparation method described above, optionally, the phosphorus source in step (b) is at least one of phosphoric acid, diammonium hydrogen phosphate, ammonium dihydrogen phosphate, and phosphorus pentoxide; optionally, when the phosphorus source in step (b) is phosphoric acid, an additive needs to be added, wherein the additive is at least one of ammonia, diethylamine, triethylamine, and choline hydroxide; optionally, the crystallization reaction is carried out at a temperature of 140℃~200℃ for 18h~168h.

[0020] In the preparation method described above, the conditions for the calcination treatment in steps (c) and (d) include: an air atmosphere and / or a water vapor atmosphere, a calcination temperature of 400–800°C, and a calcination time of 0.5–8 hours.

[0021] In the preparation method described above, the loading treatment of the loaded metal in step (d) includes: loading the metal containing the loaded metal onto the molecular sieve once or multiple times by impregnation and / or ion exchange. The rare earth metal compound is selected from rare earth metal chlorides or nitrates. Optionally, the rare earth metal compound is LaCl3, Y(NO3)3, or CeCl3.

[0022] This invention also provides a phosphorus- and rare-earth-containing CHA-structured molecular sieve obtained by the above preparation method.

[0023] To achieve the above objectives, a third aspect of the present invention further provides that the above-mentioned phosphorus- and rare earth-containing CHA structure molecular sieve is used in catalytic cracking as an active component of a catalyst or auxiliary.

[0024] The present invention provides a one-step method for preparing phosphorus-containing CHA-structured molecular sieves, avoiding complex phosphorus modification post-processing steps. This method requires fewer steps than the currently common equal-volume impregnation and ion exchange methods for molecular sieve modification, thus shortening the synthesis time and cost, and preventing a decrease in molecular sieve crystallinity during post-processing. Because the ammonium exchange step in existing technologies is eliminated, there is no ammonia nitrogen wastewater discharge. The molecular sieve obtained by this method, after being treated at 800℃ with 100% steam for 17 hours, exhibits a unique aluminum coordination state with a ratio of 1.0 to 2.0 between four-coordinate framework aluminum and five-coordinate non-framework aluminum. When the phosphorus-containing molecular sieve is further loaded with rare earth metals, it exhibits strong cracking ability, good shape selectivity, and high reactant conversion rate in light hydrocarbon catalytic cracking, while maintaining high ethylene and propylene yields. Attached Figure Description

[0025] Figure 1 This is the X-ray diffraction pattern of the SSZ-13 molecular sieve sample with a CHA structure containing phosphorus and rare earth elements prepared in Example 1.

[0026] Figure 2 This is a scanning electron microscope image of the SSZ-13 molecular sieve sample with a CHA structure containing phosphorus and rare earth elements prepared in Example 1.

[0027] Figure 3 These are SSZ-13 molecular sieve samples with a phosphorus- and rare-earth-containing CHA structure prepared in Example 2 and Comparative Example 1. 27 AlMAS NMR spectrum. Detailed Implementation

[0028] The present invention will be further illustrated by the following examples, but these examples do not limit the scope of the invention.

[0029] Unless otherwise specified, the instruments and reagents used in the embodiments of the present invention are instruments and reagents commonly used by those skilled in the art.

[0030] In the examples and comparative examples, the elemental chemical composition of the molecular sieves was determined by X-ray fluorescence spectrometry, using the standard method of GB / T30905-2014.

[0031] In the examples and comparative examples, the relative crystallinity is expressed as a percentage, which is the ratio of the sum of the peak areas of the four characteristic diffraction peaks at 13.0°, 16.1°, 17.9°, and 20.8° in the X-ray diffraction (XRD) spectra of the obtained product and the SSZ-13 molecular sieve standard. The SSZ-13 molecular sieve synthesized by the method in Example 1 of US4544538 was used as the standard, and its crystallinity was set to 100%. The X-ray diffraction pattern was measured on a Rigaku TTR-3 powder X-ray diffractometer with the following parameters: copper target (tube voltage 40 kV, tube current 250 mA), scintillation counter, step width 0.02°, and scan rate 0.4° / min.

[0032] In the examples and comparative examples, the nitrogen adsorption-desorption curves were measured using an AS-3 or AS-6 static nitrogen adsorption instrument manufactured by Quanta Chrome Instruments. Instrument parameters: The sample was placed in the sample processing system and evacuated to a vacuum of 1.33 × 10⁻⁶ at 300°C. -2 The sample was purified by holding it at a pressure of 4 h under liquid nitrogen temperature of -196℃. The adsorption and desorption amounts of the purified sample under different specific pressures P / P0 were tested to obtain N2 adsorption-desorption isotherms. The specific surface area was then calculated using the two-parameter BET formula.

[0033] In the examples and comparative examples, solid-state NMR tests were performed on a Bruker AVANCE III 600WB NMR spectrometer from Switzerland, and the test conditions were as follows: 27 The resonance frequency of the Al NMR detector was 78.155 MHz, the magic angle rotation speed was 5000 Hz, the pulse width was 1.6 μs, the cycle delay time was 1 s, the number of scans was 8000, and the test temperature was approximately 25℃. The signal peak near the chemical shift of 60 ppm corresponds to tetracoordinate framework aluminum, with an integrated peak area of ​​S1, while the signal peak near the chemical shift of 30 ppm corresponds to pentacoordinate non-framework aluminum, with an integrated peak area of ​​S2. The ratio of tetracoordinate framework aluminum to pentacoordinate non-framework aluminum content is S1 / S2.

[0034] The effects of molecular sieves on the yield and conversion of low-carbon olefins in the catalytic cracking of light hydrocarbons were evaluated using a pure hydrocarbon microreactor. The reaction was carried out in a fixed-bed reactor with 1-octene as the feedstock, nitrogen as the carrier gas at a flow rate of 30 mL / min, a reaction temperature of 550 °C, a regeneration temperature of 600 °C, and a weight hourly space velocity (WHSV) of 20.06 hr. -1 The molecular sieve tablets were sieved into 20-40 mesh particles, with a loading amount of 2.0g and an oil-to-agent ratio of 1.28. After reacting for 140s and purging with nitrogen for 900s, samples were taken for analysis and material balance calculations were performed.

[0035] Example 1

[0036] This embodiment illustrates the phosphorus- and rare-earth-containing CHA-structured molecular sieve of the present invention and its preparation.

[0037] Add 45.22g of N,N,N-trimethyl-1-adamantyl ammonium hydroxide solution (mass fraction 19.49%) and 1.59g of aluminum hydroxide to 39.9g of deionized water and stir for 30min. Add 20g of solid silica gel (containing SiO2 mass fraction 77.4%) to the solution and stir to disperse at room temperature for 3h. Transfer to a hydrothermal reactor and pre-crystallize at 120℃ for 12h. Remove the gel and add 1.9g of phosphoric acid aqueous solution (mass fraction 85%) and 1.58g of triethylamine solution (mass fraction 99%) to the gel and stir for 15min. Transfer the sol to a hydrothermal reactor and crystallize at 160℃ for 60h. Filter, wash to pH=7-8, dry at 120℃ for 12h, and then calcine at 600℃ for 6h to obtain phosphorus-containing molecular sieve.

[0038] 10g of the phosphorus-containing molecular sieve (91wt% on a dry basis) was added to 0.14g of LaCl3 for uniform mixing and impregnation, dried, and calcined at 550℃ for 2h in air atmosphere to obtain sample A. Sample A was then subjected to hydrothermal aging at 800℃ with 100% steam for 17h, followed by a light hydrocarbon catalytic cracking reaction.

[0039] The XRD pattern of sample A is as follows Figure 1 As shown, by Figure 1 As can be seen, sample A has characteristic peaks of 9.5°, 13.0°, 16.1°, 17.9°, and 20.8°, proving that it is an SSZ-13 molecular sieve with a CHA structure.

[0040] The scanning electron microscope image of sample A is shown below. Figure 2 As shown.

[0041] Sample A was subjected to hydrothermal aging at 800°C with 100% water vapor for 17 hours. 27 Al MAS NMR spectrum has Figure 3 Characteristics of the B-curve.

[0042] The physicochemical properties, P2O5 content, rare earth oxide content, micro-reaction evaluation conversion rate, ethylene and propylene yields of sample A are listed in Table 1.

[0043] Example 2

[0044] This embodiment illustrates the phosphorus- and rare-earth-containing CHA-structured molecular sieve of the present invention and its preparation.

[0045] Add 44.93g of N,N,N-trimethyl-1-adamantyl ammonium hydroxide solution (mass fraction 19.49%) and 1.53g of gibbsite to 27.5g of deionized water and stir for 30min. Then add 28.5g of solid silica gel (containing SiO2 mass fraction 77.4%) and stir to disperse at room temperature for 1h. Transfer the sol to a hydrothermal reactor and pre-crystallize at 110℃ for 24h. Remove the sol and add 2.95g of diammonium hydrogen phosphate to the gel. Stir for 15min and transfer the sol to a hydrothermal reactor. Crystallize at 160℃ for 60h. Filter, wash to pH=7-8, dry at 120℃ for 12h, and then calcine at 600℃ for 6h to obtain phosphorus-containing molecular sieve.

[0046] 15g of the above-mentioned phosphorus-containing molecular sieve (90wt% dry basis) was added to 0.63g of LaCl3 for uniform mixing and impregnation, dried, and calcined in air at 550℃ for 2h to obtain sample B. Sample B was then subjected to hydrothermal aging at 800℃ with 100% steam for 17h, followed by a light hydrocarbon catalytic cracking reaction.

[0047] XRD pattern of sample B and Figure 1 Having the same characteristics, it is confirmed to be a CHA-structured SSZ-13 molecular sieve. Scanning electron microscopy images are similar to... Figure 2 They have the same characteristics.

[0048] Sample B was subjected to hydrothermal aging at 800°C with 100% water vapor for 17 hours. 27 The Al MAS NMR spectrum is shown below. Figure 3 The B curve.

[0049] The physicochemical properties, P2O5 content, rare earth oxide content, micro-reaction evaluation conversion rate, ethylene and propylene yields of sample B are listed in Table 1.

[0050] Example 3

[0051] This embodiment illustrates the phosphorus- and rare-earth-containing CHA-structured molecular sieve of the present invention and its preparation.

[0052] Add 30.27g of N,N,N-trimethyl-1-adamantyl ammonium hydroxide solution (mass fraction 19.49%) and 1.91g of alumina to 47.6g of deionized water and stir for 30min. Then add 24g of solid silica gel (containing SiO2 mass fraction 77.4%) and stir to disperse at room temperature for 3h. Transfer the sol to a hydrothermal reactor and pre-crystallize at 120℃ for 48h. Remove the sol and add 4.22g of phosphoric acid aqueous solution (mass fraction 85%) and 4.46g of choline hydroxide solution (mass fraction 99%) to the gel and stir for 15min. Transfer the sol to a hydrothermal reactor and crystallize at 160℃ for 60h. Filter, wash to pH=7-8, dry at 120℃ for 12h, and then calcine at 600℃ for 6h to obtain phosphorus-containing SSZ-13 molecular sieve.

[0053] 15g of the above-mentioned phosphorus-containing molecular sieve (91wt% on a dry basis) was added to 1.08g of LaCl3 for uniform mixing and impregnation, dried, and calcined at 550℃ for 2h in air atmosphere to obtain sample C. Sample C was then subjected to hydrothermal aging at 800℃ with 100% steam for 17h, followed by a light hydrocarbon catalytic cracking reaction.

[0054] XRD pattern of sample C and Figure 1 Having the same characteristics, it is confirmed to be a CHA-structured SSZ-13 molecular sieve. Scanning electron microscopy images are similar to... Figure 2 They have the same characteristics.

[0055] Sample C was subjected to hydrothermal aging at 800°C with 100% water vapor for 17 hours. 27 Al MAS NMR spectrum has Figure 3 Characteristics of the B-curve.

[0056] The physicochemical properties, P2O5 content, rare earth oxide content, microreactor evaluation conversion rate, ethylene and propylene yields of sample C are listed in Table 1.

[0057] Example 4

[0058] This embodiment illustrates the phosphorus- and rare-earth-containing CHA-structured molecular sieve of the present invention and its preparation.

[0059] Add 42.58g of N,N,N-trimethyl-1-adamantyl ammonium hydroxide solution (mass fraction 19.49%) and 2.72g of aluminum sulfate to 24.08g of deionized water and stir for 30min. Then add 25g of solid silica gel (containing SiO2 mass fraction 77.4%) and stir to disperse at room temperature for 1h. Transfer the sol to a hydrothermal reactor and pre-crystallize at 120℃ for 36h. Remove the sol and add 6.47g of diammonium hydrogen phosphate to the gel. Stir for 15min and transfer the sol to a hydrothermal reactor. Crystallize at 160℃ for 60h. Filter and wash until pH=7-8. Dry at 120℃ for 12h and then calcine at 600℃ for 6h to obtain phosphorus-containing SSZ-13 molecular sieve.

[0060] 15g of the above-mentioned phosphorus-containing molecular sieve (93wt% on a dry basis) was added to 1.83g of LaCl3 for uniform mixing and impregnation, dried, and calcined in air at 550℃ for 2h to obtain sample D. Sample D was then subjected to hydrothermal aging at 800℃ with 100% steam for 17h, followed by a light hydrocarbon catalytic cracking reaction.

[0061] XRD pattern of sample D and Figure 1 Having the same characteristics, it is confirmed to be a CHA-structured SSZ-13 molecular sieve. Scanning electron microscopy images are similar to... Figure 2 They have the same characteristics.

[0062] Sample D after hydrothermal aging at 800°C with 100% water vapor for 17 hours 27 Al MAS NMR spectrum has Figure 3 Characteristics of the B-curve.

[0063] The physicochemical properties, P2O5 content, rare earth oxide content, microreactor evaluation conversion rate, ethylene and propylene yields of sample D are listed in Table 1.

[0064] Example 5

[0065] This embodiment illustrates the phosphorus- and rare-earth-containing CHA-structured molecular sieve of the present invention and its preparation.

[0066] Add 44.10g of N,N,N-trimethyl-1-adamantyl ammonium hydroxide solution (mass fraction 19.49%) and 4.28g of SB powder (containing Al2O3 mass fraction 70.6%) to 66.06g of deionized water and stir for 30min. Then add 30g of silica (containing SiO2 mass fraction 81.5%) and stir to disperse at room temperature for 3h. Transfer the sol to a hydrothermal reactor and pre-crystallize at 120℃ for 36h. Remove the sol and add 7.51g of phosphoric acid aqueous solution (mass fraction 85%) and 3.91g of ammonia water (mass fraction 85%) to the gel. Stir for 15min and transfer the sol to a hydrothermal reactor. Crystallize at 160℃ for 60h. Filter, wash to pH=7-8, dry at 120℃ for 12h, and then calcine at 600℃ for 6h to obtain phosphorus-containing SSZ-13 molecular sieve.

[0067] 15g of the above-mentioned phosphorus-containing molecular sieve (91wt% on a dry basis) was added to 0.47g of Y(NO3)3·6H2O for uniform mixing and impregnation, followed by drying and calcination at 550℃ for 2h in air atmosphere to obtain sample E. Sample E was then subjected to hydrothermal aging at 800℃ with 100% steam for 17h, followed by a light hydrocarbon catalytic cracking reaction.

[0068] XRD pattern of sample E and Figure 1 Having the same characteristics, it is confirmed to be a CHA-structured SSZ-13 molecular sieve. Scanning electron microscopy images are similar to... Figure 2 They have the same characteristics.

[0069] Sample E was subjected to hydrothermal aging at 800°C with 100% water vapor for 17 hours. 27 Al MAS NMR spectrum has Figure 3 Characteristics of the B-curve.

[0070] The physicochemical properties, P2O5 content, rare earth oxide content, microreactor evaluation conversion rate, ethylene and propylene yields of sample E are listed in Table 1.

[0071] Example 6

[0072] This embodiment illustrates the phosphorus- and rare-earth-containing CHA-structured molecular sieve of the present invention and its preparation.

[0073] Add 36.75g of N,N,N-trimethyl-1-adamantyl ammonium hydroxide solution (mass fraction 19.49%) and 1.21g of SB powder (containing Al2O3 mass fraction 70.6%) to 56.83g of deionized water and stir for 30min. Then add 24g of silica (containing SiO2 mass fraction 81.5%) and stir to disperse at room temperature for 3h. Transfer the sol to a hydrothermal reactor and pre-crystallize at 140℃ for 6h. Remove the sol and add 1.81g of ammonium dihydrogen phosphate to the gel. Stir for 15min and transfer the sol to a hydrothermal reactor. Crystallize at 160℃ for 60h. Filter and wash until pH=7-8. Dry at 120℃ for 12h and then calcine at 600℃ for 6h to obtain phosphorus-containing SSZ-13 molecular sieve.

[0074] 15g of the above-mentioned phosphorus-containing molecular sieve (88wt% on a dry basis) was added to 1.49g of Y(NO3)3·6H2O for uniform mixing and impregnation, followed by drying and calcination at 550℃ for 2h in air atmosphere to obtain sample F. Sample F was then subjected to hydrothermal aging at 800℃ with 100% steam for 17h, followed by a light hydrocarbon catalytic cracking reaction.

[0075] XRD pattern of sample F and Figure 1 Having the same characteristics, it is confirmed to be a CHA-structured SSZ-13 molecular sieve. Scanning electron microscopy images are similar to... Figure 2 They have the same characteristics.

[0076] Sample F was subjected to hydrothermal aging at 800°C with 100% water vapor for 17 hours. 27 Al MAS NMR spectrum has Figure 3 Characteristics of the B-curve.

[0077] The physicochemical properties, P2O5 content, rare earth oxide content, microreactor evaluation conversion rate, ethylene and propylene yields of sample F are listed in Table 1.

[0078] Example 7

[0079] This embodiment illustrates the phosphorus- and rare-earth-containing CHA-structured molecular sieve of the present invention and its preparation.

[0080] Add 44.10g of N,N,N-trimethyl-1-adamantyl ammonium hydroxide solution (mass fraction 19.49%) and 2.22g of SB powder (containing Al2O3 mass fraction 70.6%) to 68.91g of deionized water and stir for 30min. Then add 30g of silica (containing SiO2 mass fraction 81.5%) and stir to disperse at room temperature for 3h. Transfer the sol to a hydrothermal reactor and pre-crystallize at 140℃ for 28h. Remove the sol and add 4.34g of ammonium dihydrogen phosphate to the gel. Stir for 15min and transfer the sol to a hydrothermal reactor. Crystallize at 160℃ for 60h. Filter, wash to pH=7-8, dry at 120℃ for 12h, and then calcine at 600℃ for 6h to obtain phosphorus-containing SSZ-13 molecular sieve.

[0081] 15g of the above-mentioned phosphorus-containing molecular sieve (90wt% dry basis) was added to 2.41g of Y(NO3)3·6H2O for uniform mixing and impregnation, followed by drying and calcination at 550℃ for 2h in air atmosphere to obtain sample G. Sample G was then subjected to hydrothermal aging at 800℃ with 100% steam for 17h, followed by a light hydrocarbon catalytic cracking reaction.

[0082] XRD pattern of sample G and Figure 1 Having the same characteristics, it is confirmed to be a CHA-structured SSZ-13 molecular sieve. Scanning electron microscopy images are similar to... Figure 2 They have the same characteristics.

[0083] Sample G was subjected to hydrothermal aging at 800°C with 100% water vapor for 17 hours. 27 Al MAS NMR spectrum has Figure 3 Characteristics of the B-curve.

[0084] The physicochemical properties, P2O5 content, rare earth oxide content, microreactor evaluation conversion rate, ethylene and propylene yields of sample G are listed in Table 1.

[0085] Example 8

[0086] This embodiment illustrates the phosphorus- and rare-earth-containing CHA-structured molecular sieve of the present invention and its preparation.

[0087] Add 62.85g of N,N,N-trimethyl-1-adamantyl ammonium hydroxide solution (mass fraction 19.49%) and 1.93g of SB powder (containing Al2O3 mass fraction 70.6%) to 50.95g of deionized water and stir for 30min. Then add 20g of silica (containing SiO2 mass fraction 81.5%) and stir to disperse at room temperature for 3h. Transfer the sol to a hydrothermal reactor and pre-crystallize at 130℃ for 12h. Remove the sol and add 5.16g of ammonium dihydrogen phosphate to the gel. Stir for 15min and transfer the sol to a hydrothermal reactor. Crystallize at 160℃ for 60h. Filter, wash to pH=7-8, dry at 120℃ for 12h, and then calcine at 600℃ for 6h to obtain phosphorus-containing SSZ-13 molecular sieve.

[0088] 10g of the above-mentioned phosphorus-containing molecular sieve (89wt% on a dry basis) was added to 1.01g of CeCl3·7H2O for uniform mixing and impregnation, dried, and calcined at 550℃ in air for 2h to obtain sample H. Sample H was then subjected to hydrothermal aging at 800℃ with 100% steam for 17h, followed by a light hydrocarbon catalytic cracking reaction.

[0089] XRD pattern of sample H and Figure 1 Having the same characteristics, it is confirmed to be a CHA-structured SSZ-13 molecular sieve. Scanning electron microscopy images are similar to... Figure 2 They have the same characteristics.

[0090] Sample H was subjected to hydrothermal aging at 800°C with 100% water vapor for 17 hours. 27 Al MAS NMR spectrum has Figure 3 Characteristics of the B-curve.

[0091] The physicochemical properties, P2O5 content, rare earth oxide content, microreactor evaluation conversion rate, ethylene and propylene yields of sample H are listed in Table 1.

[0092] Example 9

[0093] This embodiment illustrates the phosphorus- and rare-earth-containing CHA-structured molecular sieve of the present invention and its preparation.

[0094] Add 19.40g of N,N,N-trimethyl-1-adamantyl ammonium hydroxide solution (mass fraction 19.49%) and 1.12g of SB powder (containing Al2O3 mass fraction 70.6%) to 60.25g of deionized water and stir for 30min. Then add 22g of silica (containing SiO2 mass fraction 81.5%) and stir to disperse at room temperature for 3h. Transfer the sol to a hydrothermal reactor and pre-crystallize at 140℃ for 18h. Remove the sol and add 1.83g of phosphoric acid aqueous solution (mass fraction 85%) and 1.88g of triethylamine solution (mass fraction 99%) to the gel and stir for 15min. Transfer the sol to a hydrothermal reactor and crystallize at 160℃ for 60h. Filter, wash to pH=7-8, dry at 120℃ for 12h, and then calcine at 600℃ for 6h to obtain phosphorus-containing SSZ-13 molecular sieve.

[0095] 15g of the above molecular sieve (90wt% dry basis) was added to 2.54g of CeCl3·7H2O for uniform mixing and impregnation, dried, and calcined in air at 550℃ for 2h to obtain sample I. Sample I was then subjected to hydrothermal aging at 800℃ with 100% steam for 17h, followed by a light hydrocarbon catalytic cracking reaction.

[0096] XRD pattern of sample I and Figure 1 Having the same characteristics, it is confirmed to be a CHA-structured SSZ-13 molecular sieve. Scanning electron microscopy images are similar to... Figure 2 They have the same characteristics.

[0097] Sample I was subjected to hydrothermal aging at 800°C with 100% water vapor for 17 hours. 27 Al MAS NMR spectrum has Figure 3 Characteristics of the B-curve.

[0098] The physicochemical properties, P2O5 content, rare earth oxide content, microreactor evaluation conversion rate, ethylene and propylene yields of sample I are listed in Table 1.

[0099] Comparative Example 1

[0100] This comparative example illustrates the preparation and physicochemical properties of SSZ-13 molecular sieves containing phosphorus and rare earth elements, obtained by modification with diammonium hydrogen phosphate and anhydrous lanthanum chloride.

[0101] 1.11 g of sodium hydroxide, 27.92 g of N,N,N-trimethyl-1-adamantyl ammonium hydroxide solution (mass fraction 19.49%), and 1.52 g of sodium aluminate were added to 42.62 g of deionized water and stirred for 30 min. Then, 20 g of solid silica gel (containing 77.4% SiO2 by mass) was added and stirred and dispersed at room temperature for 3 h. The sol was transferred to a hydrothermal reactor and crystallized at 160 °C for 60 h. After filtration, the solution was washed until pH = 7-8, dried at 120 °C for 12 h, calcined at 600 °C for 6 h, and then exchanged with soluble ammonium salt at 80 °C for 2 h to obtain SSZ-13 molecular sieve.

[0102] Take 15g of the above-mentioned molecular sieve (86wt% on a dry basis), add a solution prepared with 0.38g of diammonium hydrogen phosphate and 18g of deionized water, mix and impregnate evenly, dry, and calcine at 550℃ in air for 2h to obtain a solid powder. Add a solution prepared with 0.65g of LaCl3 and 15g of deionized water to this powder, mix and impregnate evenly, dry, and calcine at 550℃ in air for 2h to obtain sample D1. Sample D1 is hydrothermally aged at 800℃ with 100% steam for 17h, and then subjected to a light hydrocarbon catalytic cracking reaction.

[0103] XRD pattern of sample D1 and Figure 1 Having the same characteristics, the scanning electron microscope images are similar to Figure 2 They have the same characteristics.

[0104] Sample D1 was subjected to hydrothermal aging at 800°C with 100% water vapor for 17 hours. 27 The Al MAS NMR spectrum is shown below. Figure 3 The D1 curve.

[0105] The physicochemical properties, P2O5 content, rare earth oxide content, microreactor evaluation conversion rate, ethylene and propylene yields of the comparative sample D1 are listed in Table 1.

[0106] Comparative Example 2

[0107] This comparative example illustrates the preparation and physicochemical properties of SSZ-13 molecular sieves containing phosphorus and rare earth elements, obtained by modification with diammonium hydrogen phosphate and yttrium nitrate hexahydrate.

[0108] Add 0.53g sodium hydroxide, 48.86g N,N,N-trimethyl-1-adamantyl ammonium hydroxide solution (mass fraction 19.49%), and 5.56g sodium aluminate to 74.59g deionized water and stir for 30min. Then add 35g solid silica gel (containing 77.4% SiO2 by mass) and stir to disperse at room temperature for 3h. Transfer the sol to a hydrothermal reactor and crystallize at 160℃ for 60h. Filter, wash to pH=7-8, dry at 120℃ for 12h, then calcine at 600℃ for 6h, and finally exchange with soluble ammonium salt at 80℃ for 2h to obtain SSZ-13 molecular sieve.

[0109] 10g of the above-mentioned molecular sieve (88wt% on a dry basis) was added to a solution prepared with 0.31g of diammonium hydrogen phosphate and 12g of deionized water. The mixture was thoroughly mixed, impregnated, dried, and calcined in air at 550℃ for 2 hours to obtain a solid powder. A solution prepared with 0.31g of Y(NO3)3·6H2O and 12g of deionized water was added to this powder. The mixture was thoroughly mixed, impregnated, dried, and calcined in air at 550℃ for 2 hours to obtain sample D2. Sample D2 was then subjected to hydrothermal aging at 800℃ with 100% steam for 17 hours, followed by a light hydrocarbon catalytic cracking reaction.

[0110] XRD pattern of sample D2 and Figure 1 Having the same characteristics, the scanning electron microscope images are similar to Figure 2 They have the same characteristics.

[0111] Sample D2 was subjected to hydrothermal aging at 800°C with 100% water vapor for 17 hours. 27 Al MAS NMR spectrum has Figure 3 Characteristics of the D1 curve.

[0112] The physicochemical properties, P2O5 content, rare earth oxide content, microreactor evaluation conversion rate, ethylene and propylene yields of the comparative sample D2 are listed in Table 1.

[0113] Comparative Example 3

[0114] This comparative example illustrates the preparation and physicochemical properties of SSZ-13 molecular sieves containing phosphorus and rare earth elements, modified with diammonium hydrogen phosphate and cerium chloride heptahydrate.

[0115] 1.10 g of sodium hydroxide, 37.69 g of N,N,N-trimethyl-1-adamantyl ammonium hydroxide solution (mass fraction 19.49%), and 2.88 g of sodium aluminate were added to 57.54 g of deionized water and stirred for 30 min. Then, 27 g of solid silica gel (containing 77.4% SiO2 by mass) was added and stirred and dispersed at room temperature for 3 h. The sol was transferred to a hydrothermal reactor and crystallized at 160 °C for 60 h. After filtration, the solution was washed until pH = 7-8, dried at 120 °C for 12 h, calcined at 600 °C for 6 h, and then exchanged with soluble ammonium salt at 80 °C for 2 h to obtain SSZ-13 molecular sieve.

[0116] Take 20g of the above molecular sieve (87wt% on a dry basis), add a solution prepared with 0.89g of diammonium hydrogen phosphate and 25g of deionized water, mix and impregnate evenly, dry, and calcine at 550℃ in air for 2h to obtain a solid powder. Add a solution prepared with 2.0g of CeCl3·7H2O and 25g of deionized water to this powder, mix and impregnate evenly, dry, and calcine at 550℃ in air for 2h to obtain sample D3. Sample D3 is hydrothermally aged at 800℃ with 100% steam for 17h, and then subjected to a light hydrocarbon catalytic cracking reaction.

[0117] XRD pattern of sample D3 and Figure 1 Having the same characteristics, the scanning electron microscope images are similar to Figure 2 They have the same characteristics.

[0118] Sample D3 after hydrothermal aging at 800°C with 100% water vapor for 17 hours 27 Al MAS NMR spectrum has Figure 3 Characteristics of the D1 curve.

[0119] The physicochemical properties, P2O5 content, rare earth oxide content, microreactor evaluation conversion rate, ethylene and propylene yields of the comparative sample D3 are listed in Table 1.

[0120] Figure 3 A comparison of samples B and D1 shows that both samples retained some four-coordinate framework aluminum after hydrothermal aging. The aluminum spectrum of sample B has a stronger peak near 60 ppm, indicating more four-coordinate framework aluminum. In contrast, the aluminum spectrum of sample D1 shows a traditional "volcano shape". The figure shows that the retention of four-coordinate framework aluminum in sample B is greater than that in sample D1. This indicates that the phosphorus-containing and rare earth-containing SSZ-13 molecular sieve synthesized in this invention can better retain framework aluminum after hydrothermal treatment.

[0121] Table 1

[0122]

[0123] As can be seen from the data in Table 1, the ratio of four-coordinate framework aluminum content to five-coordinate non-framework aluminum content in the SSZ-13 molecular sieve prepared by this invention is higher than that in comparative samples D1, D2, and D3. In the catalytic cracking of 1-octene, the SSZ-13 molecular sieve prepared by this invention exhibits excellent reaction conversion and high yields of ethylene, propylene, and low-carbon olefins, while the SSZ-13 molecular sieve synthesized without phosphorus and modified with phosphorus and rare earth elements has lower reaction conversion and low-carbon olefin yield.

Claims

1. A CHA-structured molecular sieve containing phosphorus and rare earth elements, wherein the molar ratio of silica to alumina in the molecular sieve is 5–50, calculated as P2O5 and based on the dry weight of the molecular sieve, the phosphorus content of the molecular sieve is 0.1–10%, calculated as rare earth oxides and based on the dry weight of the molecular sieve, the rare earth metal content of the molecular sieve is 0.5–10%, and the rare earth metal is at least one selected from lanthanum, cerium, and yttrium; in the aluminum coordination state of the molecular sieve after treatment at 800°C and 100% steam for 17 hours, the ratio of tetracoordinate framework aluminum to pentacoordinate non-framework aluminum content is 1.0–2.0, and the aluminum coordination state of the molecular sieve is measured using solid-state magic angle rotational nuclear magnetic resonance (NMR).

2. The molecular sieve according to claim 1, wherein, The molecular sieve has a silica to alumina molar ratio of 10 to 35, and a phosphorus content of 0.5 to 5% based on P2O5 and the dry weight of the molecular sieve. The molecular sieve also has a rare earth metal content of 1 to 6% based on rare earth oxides and the dry weight of the molecular sieve.

3. The molecular sieve according to claim 1, after being treated at 800°C and 100% steam for 17 hours, has a ratio of 1.2 to 1.8 of tetracoordinated framework aluminum to pentacoordinated non-framework aluminum content.

4. The molecular sieve according to claim 1 is SSZ-13 molecular sieve.

5. The method for preparing the phosphorus- and rare-earth-containing CHA molecular sieve according to any one of claims 1-4, characterized in that, Includes the following steps: (a) Add template agent R, aluminum source and silicon source to deionized water, mix them evenly and then load them into a reaction vessel for pre-crystallization reaction; (b) After the pre-crystallization reaction is completed, the gel is removed, and a phosphorus source is added to the gel to obtain mixture I. Mixture I is subjected to a crystallization reaction in a reaction vessel to obtain the initial crystallization product. When the phosphorus source is phosphoric acid, an additive needs to be added. The additive is at least one of ammonia, diethylamine, triethylamine, and choline hydroxide. In the mixture I, the molar ratio of each component is as follows: template agent R: aluminum source: silicon source: phosphorus source: additive: water = 0.4~10:1:5~50:0.1~3:0~5:50~1000, where the aluminum source is calculated as Al2O3, the silicon source as SiO2, and the phosphorus source as P2O5. (c) The crystallized primary product is washed, dried and calcined to obtain a phosphorus-containing molecular sieve; (d) The phosphorus-containing molecular sieve is obtained by loading rare earth metals and calcining the phosphorus-containing molecular sieve.

6. The preparation method according to claim 5, wherein, The template agent mentioned in step (a) is N,N,N-trimethyl-1-adamantyl ammonium hydroxide, and is an aqueous solution with a mass fraction of 15-30%.

7. The preparation method according to claim 5, wherein, The aluminum source mentioned in step (a) is selected from at least one of SB powder, aluminum alkoxide, aluminum oxide, aluminum hydroxide, aluminum sulfate, and gibbsite.

8. The preparation method according to claim 5, wherein, The silicon source mentioned in step (a) is selected from at least one of silica sol, silicon dioxide, silicate, and solid silica gel.

9. The preparation method according to claim 5, wherein, The pre-crystallization reaction described in step (a) is carried out at a temperature of 100℃~140℃ for 2h~48h.

10. The preparation method according to claim 5, wherein, The phosphorus source mentioned in step (b) is at least one of phosphoric acid, diammonium hydrogen phosphate, ammonium dihydrogen phosphate, and phosphorus pentoxide.

11. The preparation method according to claim 5, wherein, The crystallization reaction described in step (b) is carried out at a temperature of 140℃~200℃ for 18h~168h.

12. The preparation method according to claim 5, wherein, The loading process for loading rare earth metals in step (d) includes loading rare earth metals onto the phosphorus-containing molecular sieve once or multiple times by impregnation and / or ion exchange of a compound containing rare earth metals.

13. The preparation method according to claim 5 or 12, wherein, The rare earth metal compounds are selected from rare earth metal chlorides or nitrates.

14. The preparation method according to claim 13, wherein, The rare earth metal compound is LaCl3, Y(NO3)3 or CeCl3.

15. The phosphorus- and rare-earth-containing CHA-structured molecular sieve of any one of claims 1-4 is used as an active component in catalytic cracking as a catalyst or auxiliary.

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