A fully crystalline molecular sieve catalyst, its preparation method and application

Abstract

This invention discloses a fully crystalline molecular sieve catalyst, its preparation method, and its application. The catalyst comprises the following components: a) 90%–99% ZSM-5 molecular sieve; b) 0.1%–5% rare earth elements; c) 0.02%–5% phosphorus (P); wherein the mass ratio of rare earth elements to P is 1–3:1, and the ratio of the amount of a moderately strong acid to a weak acid in the catalyst is 0.3–1:1. This catalyst, when applied to the cracking of C4 olefins to propylene, exhibits advantages such as high catalyst stability and good propylene selectivity.

Description

Technical Field

[0001] This invention belongs to the field of molecular sieve catalyst preparation technology, specifically relating to a fully crystalline molecular sieve catalyst, its preparation method, and its application. Background Technology

[0002] Zeolite molecular sieves are widely used in catalysis due to their advantages such as uniform and ordered micropores, large specific surface area, and high hydrothermal stability. However, zeolite powder, due to its small particle size, is inconvenient to use in practice, exhibiting disadvantages such as difficulty in recovery, easy deactivation, and aggregation. Therefore, pre-forming is necessary before use. This forming process typically requires the addition of a certain amount of binder, usually accounting for 30%–40% or even higher of the total catalyst weight, to give the catalyst a specific shape and mechanical strength. From this perspective, the binder is essential. However, binders are generally inert components, and their addition effectively "dilutes" the active centers of the molecular sieve, increasing the actual reaction space velocity and accelerating catalyst deactivation. Furthermore, binders have a pore-blocking effect on the molecular sieve, affecting its diffusion performance. Fully crystalline molecular sieves refer to zeolite particles that do not contain inert binders, have high crystallinity, a larger usable effective surface area, and better catalytic performance. Furthermore, fully crystalline molecular sieves essentially convert the binder added during the molecular sieve molding process into an effective component of the sieve, meaning the entire formed catalyst is a molecular sieve with a porous structure. Compared to molecular sieve catalysts containing binders, fully crystalline molecular sieve catalysts have a certain degree of reduced mechanical strength. This is a problem that must be faced and overcome in the industrial application of fully crystalline molecular sieve catalysts.

[0003] Current research on binders mainly focuses on silica and alumina. In alumina binders, aluminum atoms enter the molecular sieve framework, increasing the acidity of the molecular sieve. Similarly, silica binders reduce the acidity and strength. Liu Hui et al. [Liu Hui, Wei Huijuan, Xin Wenjie, Liu Shenglin, Xie Sujuan, Xu Longya, Acta Petrolei Sinica (Petroleum Processing), 30(2014)115-120] reported that in the alkylation reaction of benzene and dimethyl ether, compared with the ZnZSM-11 catalyst with alumina binder, the catalyst with aluminum phosphate binder is more conducive to the conversion of benzene, promoting the methylation reaction while inhibiting the ethylation reaction.

[0004] If the binder is converted into a molecular sieve, forming a catalytic material with a certain shape, size, and mechanical strength together with the original molecular sieve—that is, a binder-free molecular sieve catalyst—the catalyst's reactivity can be fully utilized while ensuring its mechanical strength and acidity. Methods for synthesizing binder-free molecular sieves include liquid-solid phase inversion, gas-solid phase inversion, and assembly molding. However, in actual synthesis, due to improper condition control and other reasons, the resulting binder-free molecular sieve catalysts often exhibit either very poor strength or even pulverization, or poor activity and selectivity, making it difficult to achieve a balance. Summary of the Invention

[0005] To address the problem of poor crushing strength of existing fully crystalline molecular sieve catalysts, this invention provides a novel high-strength fully crystalline molecular sieve catalyst, its preparation method, and its application. This catalyst, when applied to the cracking of C4 olefins to propylene, exhibits advantages such as high catalyst stability and good propylene selectivity.

[0006] A first aspect of the present invention provides a fully crystalline molecular sieve catalyst, wherein the catalyst comprises, by weight of the catalyst, the following components:

[0007] a) 90%–99% ZSM-5 molecular sieve;

[0008] b) 0.1% to 5% rare earth elements;

[0009] c) 0.02% to 5% P element;

[0010] The mass ratio of rare earth elements to phosphorus (P) is 1–3:1.

[0011] The ratio of the amount of medium-strong acid to the amount of weak acid in the catalyst is 0.3 to 1:1.

[0012] According to the present invention, the ratio of the amount of medium strong acid to the amount of weak acid in the catalyst is 0.5 to 1:1.

[0013] According to the present invention, the mass ratio of rare earth elements to P elements in the catalyst is 1 to 2:1.

[0014] According to the present invention, in the catalyst, the SiO2 / Al2O3 molar ratio of component a) the ZSM-5 molecular sieve is 50 to 1000, preferably 100 to 1000.

[0015] According to the present invention, in the catalyst, component b) includes at least one of La, Ce, Pr, and Nd as the rare earth element.

[0016] According to the present invention, the average crushing strength of the fully crystalline molecular sieve catalyst is 60-100 N / 5 mm, preferably 65-80 N / 5 mm. The mass content of the binder component in the fully crystalline molecular sieve is less than 3%.

[0017] According to the present invention, preferably, the catalyst comprises the following components based on the weight of the catalyst:

[0018] a) 96%–99% ZSM-5 molecular sieve;

[0019] b) 0.1% to 3% rare earth elements;

[0020] c) 0.02% to 1% of P element.

[0021] A second aspect of the present invention provides a method for preparing the above-mentioned catalyst, the method comprising the following steps:

[0022] a) Mix the first template agent, aluminum source, silicon source and alkali source evenly, perform first hydrothermal crystallization, and first calcination to obtain precursor I;

[0023] b) After mixing precursor I and binder, the mixture is molded to obtain precursor II;

[0024] c) Precursor II is subjected to a second hydrothermal crystallization in a second template agent vapor atmosphere, followed by a second calcination to obtain precursor III;

[0025] d) Precursor III was subjected to ammonium exchange and a third calcination to obtain precursor IV;

[0026] e) Load precursor IV with rare earth elements and calcine it in the fourth stage to obtain precursor V;

[0027] f) Load precursor V with phosphorus and calcine it in the fifth step to obtain precursor VI;

[0028] g) The precursor VI was subjected to organic acid treatment and steam treatment to obtain the catalyst.

[0029] According to the present invention, in step a), the first template agent comprises at least one of tetramethylammonium bromide, tetraethylammonium bromide, tetrapropylammonium bromide, and tetrapropylammonium hydroxide. The aluminum source comprises at least one of aluminum nitrate, aluminum sulfate, and sodium aluminate. The silicon source comprises at least one of water glass, silica sol, and tetraethyl orthosilicate. The alkali source comprises at least one of sodium hydroxide and potassium hydroxide. The first template agent is in the form of NH4. + The aluminum source is calculated as Al2O3, the silicon source as SiO2, and the alkali source as OH. - The molar ratio of NH4+ to water (calculated as H2O) is: + Al2O3:SiO2:OH -The ratio of H₂O is 0.1–0.5: 0.001–0.02: 1: 0.1–0.4: 5–10. The temperature for the first hydrothermal crystallization is 80–200℃, and the crystallization time is 30–100 hours. An autoclave is preferred for hydrothermal crystallization. The pressure of the autoclave is not particularly limited and is self-generated pressure. After hydrothermal crystallization, the product is washed with water and dried. The drying temperature is 80–120℃, and the time is 10–20 hours. The first calcination temperature is 500–600℃, and the time is 4–8 hours.

[0030] According to the present invention, in step b), the binder is alumina and / or silicon oxide. Preferably, the binder is alumina and silicon oxide. The weight ratio of the materials is precursor I: alumina: silicon oxide = 20-80: 2: 18-78.

[0031] According to the present invention, in step b), the molding is a kneading process. After molding, the material can be dried. The drying temperature is 80–120°C, and the drying time is 5–10 hours.

[0032] According to the present invention, in step c), the temperature of the second hydrothermal crystallization is 130–200°C, and the crystallization time is 20–200 h. The second template agent includes at least one selected from ammonia, ethylenediamine, triethylamine, n-butylamine, hexamethylenediamine, tetrapropylammonium bromide, and tetrapropylammonium hydroxide. Further, preferably, the silicon source is SiO2, and the molar ratio of the silicon source to the second template agent is 1:0.2–0.6. Preferably, the second template agent is added in the form of an aqueous solution. The mass percentage of the aqueous solution of the second template agent is 10%–60%.

[0033] According to the present invention, in step c), the temperature of the second calcination is 500-600°C, and the time is 3-10 hours. Drying can be performed before the second calcination, preferably at 80-120°C for 5-10 hours.

[0034] According to the present invention, in step d), the ammonium exchange can be performed using conventional methods. Preferably, the exchange is carried out at 80–90°C with a 5–10% by weight aqueous solution of an ammonium salt. The ammonium salt is preferably ammonium nitrate. After the ammonium exchange, washing and drying can be performed. The drying conditions are: drying temperature 80–120°C, drying time 8–10 h. The third calcination temperature is 500–600°C, and the calcination time is 4–8 h.

[0035] According to the present invention, the loading of rare earth elements in step e) can be carried out by impregnation, that is, impregnating precursor IV in a rare earth source solution. The rare earth source is a nitrate containing rare earth elements. The impregnation time is 12-48 hours. After impregnation, drying can be performed. The drying temperature is 60-100°C, and the drying time is 10-20 hours. The fourth calcination temperature is 450-600°C, and the time is 6-10 hours.

[0036] According to the present invention, the phosphorus loading method in step f) can be impregnation, that is, impregnating precursor V in a phosphorus source solution. The phosphorus source is phosphoric acid. The impregnation time is 10-30 h. After impregnation, drying can be performed. The drying temperature is 80-120°C and the drying time is 10-20 h. The fifth calcination temperature is 500-600°C and the time is 4-8 h.

[0037] According to the present invention, the organic acid in step g) is a weak organic acid. The organic acid includes at least one selected from acetic acid, oxalic acid, benzoic acid, sorbic acid, citric acid, and malic acid. The organic acid treatment method involves immersing precursor VI in an organic acid solution. The concentration of the organic acid solution is 3 wt% to 10 wt%, preferably 5 wt% to 8 wt%. The organic acid treatment temperature is 200 to 300°C, and the treatment time is 1 to 10 hours.

[0038] According to the present invention, the steam treatment in step g) involves placing the precursor VI in a steam environment. The steam treatment temperature is 500–600°C, and the treatment time is 2–20 hours.

[0039] According to the present invention, preferably, step g) can employ alternating treatments of organic acid and steam. After the organic acid treatment is completed, steam treatment is switched on. One organic acid treatment and one steam treatment constitute one alternating treatment process. Preferably, the alternating treatment process can be performed 1 to 5 times.

[0040] According to the present invention, after the organic acid treatment and steam treatment in step g), nitrogen purging and cooling are performed. The cooling rate is 10-30°C / min. The temperature is reduced to 10-30°C.

[0041] According to the present invention, the catalyst in step g) is a fully crystalline molecular sieve catalyst. The average crushing strength of the fully crystalline molecular sieve catalyst is 60-100 N / 5 mm, preferably 65-80 N / 5 mm. The binder component has a mass content of less than 3%.

[0042] A third aspect of the present invention provides the application of the above-described catalyst or the catalyst prepared by the above-described method in the reaction of cracking C4 olefins to produce propylene.

[0043] According to the present invention, the reaction conditions include: a reaction temperature of 500–600 °C; a reaction pressure of 0–1.0 MPa; and a C4 olefin weight hourly space velocity of 1–20 h⁻¹. -1 Preferably 2-15h -1 .

[0044] Currently, methods for preparing fully crystalline molecular sieve catalysts include liquid-solid phase conversion, gas-solid phase conversion, and assembly molding. However, in actual preparation processes, due to difficulties in controlling conditions or unsuitable raw material selection, the prepared fully crystalline molecular sieve catalysts may have low crystallinity or low crushing strength, making them prone to breakage during use, leading to a decline in catalyst performance and affecting industrial applications.

[0045] Compared with the prior art, the present invention has significant advantages and outstanding effects, as follows:

[0046] (1) In this invention, the catalyst includes molecular sieve, rare earth element, and P element, and is a fully crystalline catalyst with a limited mass ratio of rare earth element to P element and a limited acid ratio of medium strong acid to weak acid. This overcomes the problem of low catalyst crushing strength and ensures that the catalyst has good catalytic performance for the cracking of C4 olefins to propylene.

[0047] (2) In the catalyst preparation method of this invention, the acid strength of the catalyst can be adjusted by treating it with an organic weak acid solution at medium to high temperatures, further weakening the medium-strong acid centers. Further high-temperature steam treatment can stabilize the adjusted acid centers of the catalyst. The prepared catalyst overcomes the problem of low catalyst crushing strength, while ensuring that the catalyst has good performance in the C4 olefin cracking to propylene reaction.

[0048] (3) In this invention, the average crushing strength of the fully crystalline molecular sieve catalyst is 60-100 N / 5 mm, which is significantly better than that of the fully crystalline molecular sieve catalyst prepared by conventional methods. It has good stability and selectivity in the reaction of C4 olefin cracking to propylene. Attached Figure Description

[0049] Figure 1 This is the NH3-TPD spectrum of the catalyst in Example 1.

[0050] Figure 2 This is the NH3-TPD spectrum of the catalyst in Comparative Example 1.

[0051] Figure 3 This is the XRD pattern of the catalyst in Example 1. Detailed Implementation

[0052] The present invention will be further illustrated by the following embodiments, but the scope of protection of the present invention is not limited by the embodiments.

[0053] In this invention, the acid strength of the catalyst is tested using ammonia-programmed temperature desorption (NH3-TPD) technology. Specifically, the sample to be tested is first crushed to 20-40 mesh, 100 mg is weighed and placed in a quartz sample tube, and activated in an activation furnace at 600°C for 1 hour under a helium atmosphere. Then, the temperature is lowered to 100°C, and ammonia gas is introduced to adsorb until saturation. Then, helium gas is purged at the same temperature for 1 hour to remove the physically adsorbed ammonia gas. Next, the temperature is increased to 600°C at a rate of 10°C / min, and the desorption tail gas is analyzed and recorded as an NH3-TPD spectrum by a thermal conductivity detector in chromatography.

[0054] In this invention, based on the NH3-TPD spectrum, desorption peaks are observed in both the low-temperature desorption region (100–200 °C) and the high-temperature desorption region (300–400 °C). The desorption peak at 100–200 °C represents the desorption of NH3 from the weak acid sites on the molecular sieve surface, corresponding to the weak acid centers of the molecular sieve. The desorption peak at 300–400 °C represents the desorption of NH3 from the medium-strong acid sites on the molecular sieve surface, also corresponding to the medium-strong acid centers of the molecular sieve. Gaussian curve fitting was performed on the NH3-TPD spectrum, and the ratio of the medium-strong acid content to the weak acid content of the catalyst was calculated based on the ratio of the peak areas of the medium-strong acid peak to the weak acid peak.

[0055] In this invention, a particle strength tester is used to test the radial mechanical strength of the catalyst. Thirty catalyst particles with a length of 5 mm are taken and their strength is measured. The average value is taken as the average crushing strength of the catalyst.

[0056] In this invention, the stability time denoted as X hours in each example means: within X hours, the propylene yield decrease rate is less than or equal to 3 wt% / hour; after X hours, the catalyst activity decreases rapidly, and the propylene yield decrease rate is greater than 3 wt% / hour.

[0057] Example 1

[0058] a) Using tetrapropylammonium hydroxide as the template agent, aluminum sulfate as the aluminum source, water glass as the silicon source, and sodium hydroxide as the alkali source, the template agent is NH4+. + The aluminum source is calculated as Al2O3, the silicon source as SiO2, and the alkali source as OH. - The molar ratio of NH4 to water is: + Al2O3:SiO2:OH - The ratio of H2O is 0.2:0.002:1:0.2:8. After mixing and stirring the above raw materials evenly, they are transferred to a high-pressure reactor and crystallized at 160℃ for 40 hours. The synthesized product is washed with water, dried at 80℃ for 20 hours, and calcined at 600℃ for 4 hours to obtain ZSM-5 molecular sieve raw powder.

[0059] b) Take 300g of the above molecular sieve raw powder, 8g of alumina, and 200g of silica sol (SiO2 mass content is 40%), mix and knead, and extrude into granules with a diameter of 3 mm, a length of 3-10 mm and a circular cross-section, and dry at 100℃ for 8 hours.

[0060] c) Add a 50% (w / w) aqueous solution of ethylenediamine to a sealed reactor at a molar ratio of silicon source to ethylenediamine of 1:0.2. Place the particulate sample above the reactor. Crystallize at 180°C for 30 hours. After removing the product, dry it at 120°C for 8 hours and calcine it in a muffle furnace at 550°C for 5 hours in air.

[0061] d) After removing the calcined product from step c), it is subjected to ion exchange with a 10% by weight ammonium nitrate aqueous solution at 90°C, washed, dried at 120°C for 8 hours, and then calcined at 500°C for 8 hours.

[0062] e) Prepare a solution containing 1.5 wt% La in lanthanum nitrate, impregnate the above solid for 20 hours, dry at 80°C for 12 hours, and then calcine at 500°C for 6 hours.

[0063] f) Prepare a phosphoric acid solution containing 0.5 wt% P, impregnate the above solid for 10 hours, dry at 100°C for 15 hours, and then calcine at 550°C for 5 hours.

[0064] g) Take 20 g of the above solid product, place it in a tube furnace, heat it to 200 °C in a nitrogen atmosphere, switch to a 5% citric acid aqueous solution, treat for 3 hours, then switch to steam, heat to 550 °C, treat for 3 hours, purge with nitrogen for 3 hours, cool to 200 °C, and repeat the above process once to obtain a high-strength, fully crystalline ZSM-5 molecular sieve catalyst. The NH3-TPD spectrum of the catalyst is shown below. Figure 1 The XRD pattern of the catalyst is shown in [reference needed]. Figure 3 The composition of the fully crystalline molecular sieve catalyst is shown in Table 1.

[0065] A fixed-bed catalytic reactor was used to evaluate the performance of the prepared catalyst in the cracking of C4 hydrocarbons to propylene containing 60 wt% C4 olefins. The process conditions used were: reaction temperature 550 °C, reaction pressure 0.02 MPa, and C4 olefin weight hourly space velocity 20 h⁻¹. -1 The test results are shown in Table 2.

[0066] Example 2

[0067] a) Using tetramethylammonium bromide as the template agent, aluminum nitrate as the aluminum source, water glass as the silicon source, and sodium hydroxide as the alkali source, the template agent is NH4+. + The aluminum source is calculated as Al2O3, the silicon source as SiO2, and the alkali source as OH. - The molar ratio of NH4 to water is: +Al2O3:SiO2:OH - The ratio of H2O is 0.2:0.001:1:0.4:5. After mixing and stirring the above raw materials evenly, they are transferred to a high-pressure reactor and crystallized at 120°C for 50 hours. The synthesized product is washed with water, dried at 120°C for 10 hours, and calcined at 600°C for 4 hours to obtain ZSM-5 molecular sieve raw powder.

[0068] b) Take 300g of the above molecular sieve raw powder, 30g of alumina, and 800g of silica sol (SiO2 mass content is 40%), mix and knead, and extrude into granules with a diameter of 3 mm, a length of 3-10 mm, and a circular cross-section. Dry at 80℃ for 10 hours.

[0069] c) A 50% (w / w) aqueous solution of triethylamine was added to a sealed reactor at a molar ratio of silicon source to triethylamine of 1:0.5. The particulate sample was placed above the reactor. Crystallization was carried out at 130°C for 200 hours. After removal, the product was dried at 80°C for 10 hours and calcined in a muffle furnace at 500°C for 10 hours in air.

[0070] d) After taking out the calcination product from step c), it was subjected to ion exchange with 5% ammonium nitrate aqueous solution at 90°C, washed, dried at 80°C for 10 hours, and then calcined at 600°C for 4 hours.

[0071] e) Prepare a lanthanum nitrate solution containing 3 wt% La, impregnate the above solid for 12 hours, dry at 100°C for 10 hours, and then calcine at 500°C for 6 hours.

[0072] f) Prepare a phosphoric acid solution containing 1 wt% P, impregnate the above solid for 30 hours, dry at 80°C for 20 hours, and then calcine at 600°C for 4 hours.

[0073] g) Take 20 grams of the above solid product, place it in a tube furnace, heat it to 300°C in a nitrogen atmosphere, switch to a 3% oxalic acid aqueous solution, treat for 3 hours, then switch to steam, heat to 600°C, treat for 5 hours, purge with nitrogen for 3 hours, cool to 300°C, and repeat the above process once to obtain a high-strength fully crystalline ZSM-5 molecular sieve catalyst. The composition of the fully crystalline molecular sieve catalyst is shown in Table 1.

[0074] The evaluation method and evaluation conditions are the same as in Example 1, and the evaluation results are shown in Table 2.

[0075] Example 3

[0076] a) Using tetrapropylammonium bromide as a template agent, aluminum nitrate as the aluminum source, water glass as the silicon source, and potassium hydroxide as the alkali source, the template agent is NH4+. + The aluminum source is calculated as Al2O3, the silicon source as SiO2, and the alkali source as OH. - The molar ratio of NH4 to water is: +Al2O3:SiO2:OH - The ratio of H2O is 0.2:0.01:1:0.1:10. After mixing and stirring the above raw materials evenly, they are transferred to a high-pressure reactor and crystallized at 200℃ for 30 hours. The synthesized product is washed with water, dried at 100℃ for 8 hours, and calcined at 600℃ for 5 hours to obtain ZSM-5 molecular sieve raw powder.

[0077] b) Take 600g of the above molecular sieve raw powder, 60g of alumina, and 1500g of silica sol (SiO2 mass content is 80%), mix and knead, and extrude into granules with a diameter of 3 mm, a length of 3-10 mm and a circular cross-section, and dry at 100℃ for 8 hours.

[0078] c) A 50% (w / w) ammonia solution was added to a sealed reactor at a molar ratio of silicon source to ammonia (NH3) of 1:0.6. The particulate sample was placed above the reactor. Crystallization was carried out at 130°C for 200 hours. After removal, the product was dried at 120°C for 8 hours and calcined in a muffle furnace at 600°C for 3 hours in air atmosphere.

[0079] d) After removing the calcined product from step c), it is subjected to ion exchange with a 10% by weight ammonium nitrate aqueous solution at 80°C, washed, dried at 100°C for 8 hours, and then calcined at 500°C for 8 hours.

[0080] e) Prepare a solution containing 0.1 wt% La in lanthanum nitrate, impregnate the above solid for 20 hours, dry at 80°C for 15 hours, and then calcine at 500°C for 6 hours.

[0081] f) Prepare a phosphoric acid solution containing 0.05 wt% P, impregnate the above solid for 10 hours, dry at 100°C for 12 hours, and then calcine at 550°C for 5 hours.

[0082] g) Take 20 g of the above solid product, place it in a tube furnace, heat it to 250 °C in a nitrogen atmosphere, switch to an 8% acetic acid aqueous solution, treat for 1 hour, then switch to steam, heat to 600 °C, treat for 2 hours, purge with nitrogen for 3 hours, cool to 250 °C, and repeat the above process once. Take out the sample to obtain a high-strength fully crystalline ZSM-5 molecular sieve catalyst. The composition of the fully crystalline molecular sieve catalyst is shown in Table 1.

[0083] The evaluation method and evaluation conditions are the same as in Example 1, and the evaluation results are shown in Table 2.

[0084] Example 4

[0085] a) Using tetramethylammonium bromide as the template agent, aluminum sulfate as the aluminum source, silica sol as the silicon source, and sodium hydroxide as the alkali source, the template agent is NH4+. + The aluminum source is calculated as Al2O3, the silicon source as SiO2, and the alkali source as OH. - The molar ratio of NH4 to water is:+ Al2O3:SiO2:OH - The ratio of H2O is 0.5:0.02:1:0.1:6. After mixing and stirring the above raw materials evenly, they are transferred to a high-pressure reactor and crystallized at 80°C for 100 hours. The synthesized product is washed with water, dried at 80°C for 20 hours, and calcined at 600°C for 4 hours to obtain ZSM-5 molecular sieve raw powder.

[0086] b) Take 300g of the above molecular sieve raw powder, 20g of alumina, and 600g of silica sol (SiO2 mass content is 80%), mix and knead, and extrude into granules with a diameter of 3 mm, a length of 3-10 mm, and a circular cross-section. Dry at 100℃ for 8 hours.

[0087] c) A 50% (w / w) aqueous solution of tetrapropylammonium hydroxide was added to a sealed reactor at a molar ratio of silicon source to tetrapropylammonium hydroxide of 1:0.5. The particulate sample was placed above the reactor and crystallized at 180°C for 30 hours. After removal, the product was dried at 120°C for 8 hours and calcined in a muffle furnace at 550°C for 5 hours in air.

[0088] d) After removing the calcined product from step c), it is subjected to ion exchange with a 10% by weight ammonium nitrate aqueous solution at 90°C, washed, dried at 120°C for 8 hours, and then calcined at 500°C for 8 hours.

[0089] e) Prepare a lanthanum nitrate solution containing 2wt% La, impregnate the above solid for 20 hours, dry at 80°C for 12 hours, and then calcine at 500°C for 6 hours.

[0090] f) Prepare a phosphoric acid solution containing 2wt% P, impregnate the above solid for 10 hours, dry at 100°C for 15 hours, and then calcine at 550°C for 5 hours.

[0091] g) Take 20 grams of the above solid product, place it in a tube furnace, heat it to 200°C in a nitrogen atmosphere, switch to a 7% citric acid aqueous solution, treat for 3 hours, then switch to steam, heat to 550°C, treat for 3 hours, purge with nitrogen for 3 hours, cool to 200°C, and repeat the above process once to obtain a high-strength fully crystalline ZSM-5 molecular sieve catalyst. The composition of the fully crystalline molecular sieve catalyst is shown in Table 1.

[0092] The evaluation method and evaluation conditions are the same as in Example 1, and the evaluation results are shown in Table 2.

[0093] Comparative Example 1

[0094] The difference from Example 1 is that neither carboxylic acid post-treatment nor steam post-treatment was used, specifically:

[0095] a) Using tetrapropylammonium hydroxide as the template agent, aluminum sulfate as the aluminum source, water glass as the silicon source, and sodium hydroxide as the alkali source, the template agent is NH4+.+ The aluminum source is calculated as Al2O3, the silicon source as SiO2, and the alkali source as OH. - The molar ratio of NH4 to water is: + Al2O3:SiO2:OH - The ratio of H2O is 0.2:0.002:1:0.2:8. After mixing and stirring the above raw materials evenly, they are transferred to a high-pressure reactor and crystallized at 160°C for 40 hours. The synthesized product is washed with water, dried at 80°C for 20 hours, and calcined at 600°C for 4 hours to obtain ZSM-5 molecular sieve raw powder.

[0096] b) Take 300g of the above molecular sieve raw powder, 8g of alumina, and 200g of silica sol (SiO2 mass content is 40%), mix and knead, and extrude into granules with a diameter of 3 mm, a length of 3-10 mm and a circular cross-section, and dry at 100℃ for 8 hours.

[0097] c) An aqueous solution of 50% ethylenediamine (by mass) was added to a sealed reactor at a molar ratio of silicon source to ethylenediamine of 1:0.2. The particulate sample was placed above the reactor and crystallized at 180°C for 30 hours. The product was then removed, dried at 120°C for 8 hours, and calcined in a muffle furnace at 550°C for 5 hours in air.

[0098] d) After removing the calcined product from step c), it was subjected to ion exchange with a 10% by weight ammonium nitrate aqueous solution at 90°C, washed, dried at 120°C for 8 hours, and then calcined at 500°C for 8 hours.

[0099] e) Prepare a solution containing 1.5 wt% La in lanthanum nitrate, impregnate the above solid for 20 hours, dry at 80°C for 12 hours, and then calcine at 500°C for 6 hours.

[0100] f) Prepare a phosphoric acid solution containing 0.5 wt% P, impregnate the above solid for 10 hours, dry at 100℃ for 15 hours, and then calcine at 550℃ for 5 hours to obtain a fully crystalline ZSM-5 molecular sieve catalyst. The NH3-TPD spectrum of the catalyst is shown in [reference needed]. Figure 2 The composition of the fully crystalline molecular sieve catalyst is shown in Table 1.

[0101] The evaluation method and evaluation conditions are the same as in Example 1, and the evaluation results are shown in Table 2.

[0102] Comparative Example 2

[0103] The difference from Example 1 is that only organic acid post-treatment was used, without steam post-treatment. Specifically:

[0104] a) Using tetrapropylammonium hydroxide as the template agent, aluminum sulfate as the aluminum source, water glass as the silicon source, and sodium hydroxide as the alkali source, the template agent is NH4+. + The aluminum source is calculated as Al2O3, the silicon source as SiO2, and the alkali source as OH. -The molar ratio of NH4 to water is: + Al2O3:SiO2:OH - The ratio of H2O is 0.2:0.002:1:0.2:8. After mixing and stirring the above raw materials evenly, they are transferred to a high-pressure reactor and crystallized at 160°C for 40 hours. The synthesized product is washed with water, dried at 80°C for 20 hours, and calcined at 600°C for 4 hours to obtain ZSM-5 molecular sieve raw powder.

[0105] b) Take 300g of the above molecular sieve raw powder, 8g of alumina, and 200g of silica sol (SiO2 mass content is 40%), mix and knead, and extrude into granules with a diameter of 3 mm, a length of 3-10 mm and a circular cross-section, and dry at 100℃ for 8 hours.

[0106] c) An aqueous solution of 50% ethylenediamine (by mass) was added to a sealed reactor at a molar ratio of silicon source to ethylenediamine of 1:0.2. The particulate sample was placed above the reactor and crystallized at 180°C for 30 hours. The product was then removed, dried at 120°C for 8 hours, and calcined in a muffle furnace at 550°C for 5 hours in air.

[0107] d) After removing the calcined product from step c), it was subjected to ion exchange with a 10% by weight ammonium nitrate aqueous solution at 90°C, washed, dried at 120°C for 8 hours, and then calcined at 500°C for 8 hours.

[0108] e) Prepare a solution containing 1.5 wt% La in lanthanum nitrate, impregnate the above solid for 20 hours, dry at 80°C for 12 hours, and then calcine at 500°C for 6 hours.

[0109] f) Prepare a phosphoric acid solution containing 0.5 wt% P, impregnate the above solid for 10 hours, dry at 100°C for 15 hours, and then calcine at 550°C for 5 hours.

[0110] g) Take 20 grams of the above solid product, place it in a tube furnace, heat it to 200°C in a nitrogen atmosphere, switch to a 5% citric acid aqueous solution, treat for 6 hours, then switch to nitrogen purging for 3 hours and cool to 200°C. Remove the sample to obtain a fully crystalline ZSM-5 molecular sieve catalyst. The average crushing strength of the catalyst was measured to be 50 N / 5 mm, and the ratio of medium-strong acid to weak acid in the catalyst was 1.5:1. The composition of the fully crystalline molecular sieve catalyst is shown in Table 1.

[0111] The evaluation method and evaluation conditions are the same as in Example 1, and the evaluation results are shown in Table 2.

[0112] Comparative Example 3

[0113] The difference from Example 1 is that no organic acid was used; only steam treatment was employed. Specifically:

[0114] a) Using tetrapropylammonium hydroxide as the template agent, aluminum sulfate as the aluminum source, water glass as the silicon source, and sodium hydroxide as the alkali source, the template agent is NH4+. + The aluminum source is calculated as Al2O3, the silicon source as SiO2, and the alkali source as OH. - The molar ratio of NH4 to water is: + Al2O3:SiO2:OH - The ratio of H2O is 0.2:0.002:1:0.2:8. After mixing and stirring the above raw materials evenly, they are transferred to a high-pressure reactor and crystallized at 160℃ for 40 hours. The synthesized product is washed with water, dried at 80℃ for 20 hours, and calcined at 600℃ for 4 hours to obtain ZSM-5 molecular sieve raw powder.

[0115] b) Take 300g of the above molecular sieve raw powder, 8g of alumina, and 200g of silica sol (SiO2 mass content is 40%), mix and knead, and extrude into granules with a diameter of 3 mm, a length of 3-10 mm and a circular cross-section, and dry at 100℃ for 8 hours.

[0116] c) An aqueous solution of 50% ethylenediamine was added to a sealed reactor at a molar ratio of silicon source to ethylenediamine of 1:0.2. The particulate sample was placed above the reactor and crystallized at 180°C for 30 hours. The product was then removed, dried at 120°C for 8 hours, and calcined in a muffle furnace at 550°C for 5 hours in air atmosphere.

[0117] d) After taking out the calcination product from step c), it was subjected to ion exchange with 10% by weight of ammonium nitrate aqueous solution at 90°C, washed, dried at 120°C for 8 hours, and then calcined at 500°C for 8 hours.

[0118] e) Prepare a solution containing 1.5 wt% La in lanthanum nitrate, impregnate the above solid for 20 hours, dry at 80°C for 12 hours, and then calcine at 500°C for 6 hours.

[0119] f) Prepare a phosphoric acid solution containing 0.5 wt% P, impregnate the above solid for 10 hours, dry at 100°C for 15 hours, and then calcine at 550°C for 5 hours.

[0120] g) Take 20 grams of the above solid product, place it in a tube furnace, heat it to 550°C in a nitrogen atmosphere, switch to steam, treat for 6 hours, then switch to nitrogen purging for 3 hours, cool down, and take out the sample to obtain the fully crystalline ZSM-5 molecular sieve catalyst. The composition of the fully crystalline molecular sieve catalyst is shown in Table 1.

[0121] The evaluation method and evaluation conditions are the same as in Example 1, and the evaluation results are shown in Table 2.

[0122] Comparative Example 4

[0123] The difference from Example 1 is that the catalyst does not contain rare earth elements or phosphorus, specifically:

[0124] a) Using tetrapropylammonium hydroxide as the template agent, aluminum sulfate as the aluminum source, water glass as the silicon source, and sodium hydroxide as the alkali source, the template agent is NH4+. + The aluminum source is calculated as Al2O3, the silicon source as SiO2, and the alkali source as OH. - The molar ratio of NH4 to water is: + Al2O3:SiO2:OH - The ratio of H2O is 0.2:0.002:1:0.2:8. After mixing and stirring the above raw materials evenly, they are transferred to a high-pressure reactor and crystallized at 160℃ for 40 hours. The synthesized product is washed with water, dried at 80℃ for 20 hours, and calcined at 600℃ for 4 hours to obtain ZSM-5 molecular sieve raw powder.

[0125] b) Take 300g of the above molecular sieve raw powder, 8g of alumina, and 200g of silica sol (SiO2 mass content is 40%), mix and knead, and extrude into granules with a diameter of 3 mm, a length of 3-10 mm and a circular cross-section, and dry at 100℃ for 8 hours.

[0126] c) An aqueous solution of 50% ethylenediamine (by mass) was added to a sealed reactor at a molar ratio of silicon source to ethylenediamine of 1:0.2. The particulate sample was placed above the reactor and crystallized at 180°C for 30 hours. The product was then removed, dried at 120°C for 8 hours, and calcined in a muffle furnace at 550°C for 5 hours in air.

[0127] d) After taking out the calcination product from step c), it was subjected to ion exchange with 10% by weight of ammonium nitrate aqueous solution at 90°C, washed, dried at 120°C for 8 hours, and then calcined at 500°C for 8 hours.

[0128] e) Take 20 grams of the above solid product, place it in a tube furnace, heat it to 200°C in a nitrogen atmosphere, switch to a 5% citric acid aqueous solution, treat for 3 hours, then switch to steam, heat to 550°C, treat for 3 hours, purge with nitrogen for 3 hours, cool to 200°C, and repeat the above process once. Take out the sample to obtain the fully crystalline ZSM-5 molecular sieve catalyst. The composition of the fully crystalline molecular sieve catalyst is shown in Table 1.

[0129] The evaluation method and evaluation conditions are the same as in Example 1, and the evaluation results are shown in Table 2.

[0130] Comparative Example 5

[0131] The difference from Example 1 is that step e) involves preparing a lanthanum nitrate solution containing 1.6 wt% La, and step f) involves preparing a phosphoric acid solution containing 0.4 wt% P. Everything else is the same as in Example 1. The catalyst composition is shown in Table 1, and the test results are shown in Table 2.

[0132] As can be seen from the comparison between Example 1 and Comparative Examples 1 to 4, the catalyst of the present invention is the result of the combined effects of rare earth loading, phosphorus, organic acid post-treatment and steam post-treatment. When the catalyst does not contain rare earth and phosphorus, organic acid post-treatment and steam post-treatment cannot achieve the purpose of the present invention.

[0133] Table 1 Catalyst Composition for Each Example

[0134] Component a), % Component b), % Component c), % adhesive components Example 1 98 1.5 0.5 0 Example 2 96 3 1 0 Example 3 99.85 0.1 0.05 0 Example 4 96 2 2 0 Comparative Example 1 98 1.5 0.5 0 Comparative Example 2 98 1.5 0.5 0 Comparative Example 3 98 1.5 0.5 0 Comparative Example 4 100 0 0 0 Comparative Example 5 98 1.6 0.4 0

[0135] Table 2. Test results of each catalyst.

[0136]

[0137] The specific embodiments of the present invention have been described in detail above; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combining the various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.

Claims

1. A fully crystalline molecular sieve catalyst, comprising the following components based on the weight of the catalyst: a) 90%~99% ZSM-5 molecular sieve; b) 0.1%~5% rare earth elements; c) 0.02%~5% P element; in, The mass ratio of rare earth elements to phosphorus (P) is 1~3:

1. The ratio of the amount of medium-strong acid to the amount of weak acid in the catalyst is 0.3~1:1; The acidity was measured using NH3-TPD. The desorption peak at 100~200℃ corresponds to the weak acid center of the molecular sieve, and the desorption peak at 300~400℃ corresponds to the medium strong acid center of the molecular sieve. The ratio of the medium strong acid content to the weak acid content of the catalyst was obtained based on the ratio of the peak area of ​​the medium strong acid peak to the peak area of ​​the weak acid peak. Component b) The rare earth element includes at least one of La, Ce, Pr, and Nd.

2. The catalyst according to claim 1, characterized in that, In the catalyst, the mass ratio of rare earth elements to phosphorus elements is 1~2:1; and / or, the ratio of the amount of medium strong acid to the amount of weak acid is 0.5~1:

1.

3. The catalyst according to claim 1, characterized in that, The SiO2 / Al2O3 molar ratio of the ZSM-5 molecular sieve in component a) is 50~1000.

4. The catalyst according to claim 1, characterized in that, The SiO2 / Al2O3 molar ratio of the ZSM-5 molecular sieve in component a) is 100~1000.

5. A method for preparing the catalyst according to any one of claims 1 to 4, comprising the following steps: a) Mix the first template agent, aluminum source, silicon source and alkali source evenly, perform first hydrothermal crystallization, and first calcination to obtain precursor I; b) After mixing precursor I and binder, the mixture is molded to obtain precursor II; c) Precursor II is subjected to a second hydrothermal crystallization in a second template agent vapor atmosphere, followed by a second calcination to obtain precursor III; d) Precursor III was subjected to ammonium exchange and a third calcination to obtain precursor IV; e) Load precursor IV with rare earth elements and calcine it in the fourth stage to obtain precursor V; f) Load precursor V with phosphorus and calcine it in the fifth step to obtain precursor VI; g) The precursor VI was subjected to organic acid treatment and steam treatment to obtain the catalyst.

6. The preparation method according to claim 5, characterized in that, In step a), The first template agent includes at least one of tetramethylammonium bromide, tetraethylammonium bromide, tetrapropylammonium bromide, and tetrapropylammonium hydroxide; And / or, the aluminum source includes at least one of aluminum nitrate, aluminum sulfate, and sodium aluminate; And / or, the silicon source includes at least one of water glass, silica sol, and tetraethyl orthosilicate; And / or, the alkali source includes at least one of sodium hydroxide and potassium hydroxide; And / or, the first template agent is NH4 + The aluminum source is calculated as Al2O3, the silicon source as SiO2, and the alkali source as OH. - The molar ratio of NH4+ to water (calculated as H2O) is: + Al2O3:SiO2:OH - : H2O=0.1~0.5: 0.001~0.02: 1: 0.1~0.4: 5~10.

7. The preparation method according to claim 5, characterized in that, In step a), the temperature of the first hydrothermal crystallization is 80~200℃, and the crystallization time is 30~100h; And / or, the temperature of the first roasting is 500~600℃, and the time is 4~8h.

8. The preparation method according to claim 5, characterized in that, In step b), the binder is aluminum oxide and / or silicon oxide.

9. The preparation method according to claim 8, characterized in that, The binder is alumina and silicon dioxide; the weight ratio of the feed materials is precursor I: alumina: silicon dioxide = 20~80:2:18~78.

10. The preparation method according to claim 5, characterized in that, In step c), The second template agent includes at least one selected from ammonia, ethylenediamine, triethylamine, n-butylamine, hexamethylenediamine, tetrapropylammonium bromide, and tetrapropylammonium hydroxide; And / or, the temperature of the second hydrothermal crystallization is 130~200℃, and the crystallization time is 20~200h; And / or, the second calcination temperature is 500~600℃, and the time is 3~10h.

11. The preparation method according to claim 5, characterized in that, In step g), the organic acid includes at least one selected from acetic acid, oxalic acid, benzoic acid, sorbic acid, citric acid, and malic acid; And / or, the temperature for organic acid treatment is 200~300℃, and the treatment time is 1~10h.

12. The preparation method according to claim 5, characterized in that, In step g), the temperature of the steam treatment is 500~600℃, and the treatment time is 2~20 hours.

13. The use of a catalyst according to any one of claims 1 to 4 or a catalyst prepared by any one of claims 5 to 12 in the cracking of C4 olefins to propylene.

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