Phosphorus-modified ZSM-5 molecular sieve and preparation method thereof

Abstract

A phosphorus-modified ZSM-5 molecular sieve is characterized in that in a 31P MAS-NMR spectrogram, the chemical shift range of resonance signal peaks is 5-20 ppm, and after hydrothermal aging is carried out for 17 h under the conditions of 800 DEG C and 100% water vapor, the area ratio of the resonance signal peaks with chemical shifts of-30 + / -3 ppm to-40 + / -3 ppm is larger than 1; the phosphorus content retention rate of the molecular sieve after water washing is higher than 50%.

Description

Technical Field

[0001] The present invention relates to a modified ZSM-5 molecular sieve and a preparation method thereof, and further relates to a phosphorus-modified ZSM-5 molecular sieve and a preparation method thereof. Background Art

[0002] ZSM-5 molecular sieve is a medium-pore molecular sieve with high silicon three-dimensional straight channels and MFI structure developed by Mobil Oil Company of the United States (USP3702886). Its unique pore structure gives it good shape-selective catalytic and isomerization performance. It also has the characteristics of high thermal and hydrothermal stability, high specific surface area, wide range of silicon-aluminum ratio, unique surface acidity and low carbon deposition. ZSM-5 molecular sieve is widely used as a catalyst and catalyst carrier, and has been successfully used in production processes such as alkylation, isomerization, disproportionation, catalytic cracking, methanol to gasoline, and methanol to olefins.

[0003] Since 1983, ZSM-5 molecular sieve has been used as a catalytic cracking octane number aid in catalytic cracking process, aiming to improve the octane number of catalytic cracking gasoline and the selectivity of light olefins. US3758403 first reported the use of ZSM-5 molecular sieve as an active component for increasing propylene production, which was used together with REY as an active component of FCC catalyst. US5997728 disclosed the use of ZSM-5 molecular sieve without any modification as an aid for increasing propylene production, but the propylene yield was not high. Although HZSM-5 molecular sieve has good shape selectivity and isomerization performance, its disadvantage is poor hydrothermal stability and easy deactivation under harsh high-temperature hydrothermal conditions, which reduces the catalytic performance.

[0004] In the 1980s, Mobil Corporation discovered that phosphorus can improve the hydrothermal stability of ZSM-5 molecular sieves, and phosphorus modification of ZSM-5 molecular sieves increases the yield of light olefins. Conventional ZSM-5 additives activated with phosphorus are usually used to selectively convert primary cracking products (such as gasoline olefins) into C3 and C4 olefins. ZSM-5 molecular sieves are modified by introducing an appropriate amount of inorganic phosphorus compounds after synthesis, which can stabilize the framework aluminum under harsh hydrothermal conditions.

[0005] CN 1211469A discloses a five-membered ring molecular sieve composition for producing more propylene and ethylene, which is composed of 85-95% by weight of five-membered ring molecular sieve, 2-10% by weight of phosphorus calculated as oxide, 0.3-5% by weight of alkaline earth metal calculated as oxide, and 0.3-5% by weight of transition metal element calculated as oxide. The composition is used for catalytic thermal cracking reaction to obtain a higher ethylene yield.

[0006] US5171921 discloses a phosphorus-modified ZSM-5 molecular sieve having a silicon-aluminum ratio of 20-60. After being impregnated with a phosphorus-containing compound and treated with steam at 500-700°C, it has higher activity when used for the reaction of converting C3-C20 hydrocarbons into C2-C5 olefins than HZSM-5 that is not treated with phosphorus.

[0007] CN102166533A discloses a method for preparing a phosphorus-modified ZSM-5 molecular sieve, which comprises adding the molecular sieve to a phosphorus-containing aqueous solution, reacting for a period of time at a certain pH value, temperature and pressure, and then filtering, drying and calcining to obtain the phosphorus-modified molecular sieve. Thereafter, the phosphorus-modified molecular sieve is added to an aqueous solution containing rare earth ions, reacting for a period of time at a certain temperature and pressure, and then filtering, washing, drying and calcining to obtain a composite modified molecular sieve. The composite modified molecular sieve is used to prepare a model catalyst having higher hydrothermal stability and micro-activity than the unmodified molecular sieve model catalyst and the molecular sieve model catalyst modified by other methods.

[0008] CN106994364A discloses a method for preparing a phosphorus-modified ZSM-5 molecular sieve, which comprises first mixing one or more phosphorus-containing compounds selected from phosphoric acid, diammonium hydrogen phosphate, ammonium dihydrogen phosphate and ammonium phosphate with a ZSM-5 molecular sieve having a high alkali metal ion content to obtain a mixture having a phosphorus loading of at least 0.1 wt% in terms of P2O5, drying and roasting the mixture, and then performing an ammonium crosslinking step and a water washing step to reduce the alkali metal ion content therein to below 0.10 wt%, and then undergoing drying and hydrothermal aging steps at 400-1000°C and 100% water vapor. The phosphorus-containing ZSM-5 molecular sieve obtained by the preparation method has a high total acid content, excellent cracking conversion rate and propylene selectivity, and also has a high liquefied gas yield.

[0009] Although the use of organic / inorganic phosphorus-containing compounds to modify ZSM-5 molecular sieves can inhibit skeleton dealumination and thus improve hydrothermal stability, the introduction of phosphorus species also has the effect of regulating the properties of the acid center of the ZSM-5 molecular sieve, thereby improving the cracking conversion rate of long-chain alkanes and the selectivity of light olefins, but in the roasting process of the prior art, phosphoric acid or ammonium phosphate will self-polymerize due to dehydration to generate large molecular phosphorus species such as polyphosphoric acid, which are easily enriched on the outer surface of the molecular sieve, blocking the pores, reducing the pore volume and specific surface area, resulting in a low phosphorus-aluminum activation efficiency, and the ideal effect of improving hydrothermal stability cannot be achieved after phosphorus modification. Summary of the invention

[0010] The inventors found, based on a large number of experiments, that treating ZSM-5 molecular sieves with inorganic phosphorus compounds having a valence state of +1 and smaller molecules, such as hypophosphorous acid and ammonium hypophosphite, as phosphorus sources and combining with a specific preparation and calcination temperature different from the conventional prior art, can not only promote the activation coordination of phosphorus with framework aluminum, but also the phosphorus-modified ZSM-5 molecular sieve obtained by the treatment has physical and chemical characteristics different from conventional phosphorus-containing ZSM-5 molecular sieves and a higher phosphorus retention rate after the molecular sieve is washed with water. Based on this, the present invention is formed.

[0011] The purpose of the present invention is to overcome the problems of hydrothermal stability, cracking activity and low-carbon olefin selectivity in the prior art, and to provide a phosphorus-modified ZSM-5 molecular sieve with physical and chemical characteristics different from those of the prior art and a preparation method thereof.

[0012] In order to achieve the above object, the first aspect of the present invention is to provide a phosphorus-modified ZSM-5 molecular sieve, characterized in that 31 In the P MAS-NMR spectrum, the chemical shift range of the resonance signal peak is 5 to -20 ppm.

[0013] Molecular sieve 31 In the P MAS-NMR spectrum, due to the diversity of phosphorus species, the chemical shift of the resonance signal peak generated has a certain range, representing the degree of condensation of the overall phosphorus species. Among them, the resonance signal peaks in the low field range of 0ppm, -6ppm and -15ppm represent phosphorus species with a lower degree of condensation such as monomeric phosphoric acid and pyrophosphoric acid, while the resonance signal peaks of -20 to -40ppm represent polyphosphoric acid species with a higher degree of condensation. The inventors of the present invention unexpectedly discovered that in the preparation process of phosphorus-modified ZSM-5 molecular sieve, a calcination method different from the conventional 550°C in the prior art was adopted, and after low-temperature calcination at 300 to 400°C in the atmosphere of air, the chemical shift range of the resonance signal peak was 5 to -20ppm, indicating that the condensation degree of its phosphorus species was low; while the phosphoric acid-modified molecular sieve of the prior art had a higher degree of condensation of phosphorus species after calcination at the conventional 550°C, and the chemical shift range of the resonance signal peak was 5 to -50ppm.

[0014] The phosphorus-modified ZSM-5 molecular sieve of the present invention is further subjected to hydrothermal aging at 800° C. and 100% steam for 17 hours. 31In the P MAS-NMR spectrum, the chemical shift of -30±3ppm and -40±3ppm resonance signal peak area ratio>1, preferably, the area ratio is 1.05-1.4, more preferably 1.1-1.3. The chemical shift of -30±3ppm resonance signal represents the tetracoordinate phosphorus species formed after stabilizing the framework aluminum species, and the -40±3ppm resonance signal represents the condensed pentacoordinate phosphorus species. The larger the resonance signal peak area ratio of -30±3ppm to -40±3ppm, the more phosphorus species that can stabilize the framework aluminum. In the prior art, the resonance signal peak area ratio of -30±3ppm to -40±3ppm of the ZSM-5 molecular sieve modified with a phosphorus-containing precursor such as diammonium hydrogen phosphate or phosphoric acid with a phosphorus valence of +5 is <1.

[0015] The phosphorus-modified ZSM-5 molecular sieve of the present invention is further subjected to hydrothermal aging at 800°C and 100% steam for 17 hours. 27 In the Al MAS-NMR spectrum, resonance signal peaks with chemical shifts of 39±3ppm and -12±3ppm appear simultaneously. The resonance signal with chemical shift of 39±3ppm indicates the framework aluminum species stabilized after coordination with phosphorus species, i.e. distorted tetracoordinate framework aluminum; the resonance signal with chemical shift of -12±3ppm indicates the extra-framework aluminum species combined with phosphorus species.

[0016] The phosphorus-modified ZSM-5 molecular sieve of the present invention has a higher phosphorus retention rate after water washing. For example, after being washed with hot water at 70°C for 2 hours, the phosphorus content retention rate is higher than 50%, about 51-75%, while the phosphorus content retention rate of the prior art is less than 50%. The phosphorus content retention rate is defined as P2O5 before water washing / P2O5 after water washing, calculated in mass percentage.

[0017] The phosphorus-modified ZSM-5 molecular sieve of the present invention has a molar ratio of phosphorus to aluminum of 0.01 to 5, preferably 0.1 to 3.

[0018] In one embodiment of the molecular sieve, the molecular sieve is modified with a phosphorus-containing compound having a phosphorus valence state of +1 and obtained by a step of calcining in air at 300-400°C.

[0019] In order to achieve the above-mentioned purpose, the second aspect of the present invention provides a method for preparing the above-mentioned phosphorus-containing ZSM-5 molecular sieve, characterized in that the HZSM-5 molecular sieve is contacted and impregnated with an aqueous solution of a phosphorus-containing compound with a phosphorus valence state of +1, and then dried and air-roasted at 300-400°C to obtain a phosphorus-modified ZSM-5 molecular sieve; or the HZSM-5 molecular sieve is mixed and ground with a solid phosphorus-containing compound with a phosphorus valence state of +1 to obtain a mixture, which is heated and melted, cooled to 20-25°C, and then calcined at 300-400°C.

[0020] The preparation method of the phosphorus-containing ZSM-5 molecular sieve provided by the invention comprises two steps: impregnation with a phosphorus precursor aqueous solution of +1-valent phosphorus and heating and melting treatment.

[0021] In one embodiment of the present invention, the aqueous solution is impregnated, the water-to-screen weight ratio is 0.5-2, and the process is carried out for 0.5-10 hours; the drying is carried out in an air atmosphere at 100-120°C for 2-24 hours; the calcination is carried out in an air atmosphere at 300-400°C, preferably 330-370°C, more preferably 350°C, for 0.5-12 hours.

[0022] In one embodiment of the present invention, the heating and melting treatment is performed at a temperature higher than the melting point of the solid phosphorus-containing compound and lower than the temperature at which the solid phosphorus-containing compound decomposes or dehydrates (for example, the melting point of hypophosphorous acid is 26.5°C and the decomposition temperature is 130°C), and the treatment time is 2 to 72 hours.

[0023] In the preparation method provided by the present invention, the HZSM-5 molecular sieve is treated with a phosphorus-containing compound with a phosphorus valence state of +1. By selecting a relatively small +1-valent phosphorus source, the migration process of phosphorus species into the pores of the ZSM-5 molecular sieve is accelerated, and the activation efficiency of phosphorus aluminum species is accelerated. The phosphorus-containing compound with a phosphorus valence state of +1 is one or more of hypophosphorous acid, ammonium hypophosphite, and hypophosphite; or, the phosphorus-containing compound aqueous solution with a phosphorus valence state of +1 is an aqueous solution of hypophosphorous acid adjusted to a pH value of 5-9 with ammonia water. As phosphorus-containing precursors, after air roasting at 300-400°C, especially 350°C, phosphorus is converted from +1 to a higher oxidation valence state and has the conditions to stabilize the framework aluminum during the aging process.

[0024] The phosphorus-containing ZSM-5 molecular sieve provided by the present invention has a significant coordination effect between phosphorus species and framework aluminum, so that the framework aluminum is fully protected, and has a higher crystal retention (95% to 110%) after hydrothermal aging at 800°C and 100% water vapor for 17 hours, so that the phosphorus-modified ZSM-5 molecular sieve has excellent hydrothermal stability. The phosphorus-modified ZSM-5 molecular sieve of the present invention can be used as a catalyst in catalytic cracking reactions. For example, in the cracking reaction of n-tetradecane, the main indicators are improved relative to the comparative samples, for example, a higher conversion rate and liquefied gas yield, and the yields of trienes (ethylene, propylene and butene) are all significantly improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 For samples 31 P MAS-NMR spectrum.

[0026] Figure 2 The sample was treated with 800℃, 100% steam, and 17h hydrothermal aging. 31 P MAS-NMR spectrum.

[0027] Figure 3 For samples 27 Al MAS-NMR spectrum.

[0028] Figure 4 For samples 31 P MAS-NMR spectrum.

[0029] Figure 5 The sample was treated with 800℃, 100% steam, and 17h hydrothermal aging. 31 P MAS-NMR spectrum.

[0030] Figure 6 For samples 27 Al MAS-NMR spectrum.

[0031] Figure 7 For samples 31 P MAS-NMR spectrum.

[0032] Figure 8 The sample was treated with 800℃, 100% steam, and 17h hydrothermal aging. 31 P MAS-NMR spectrum.

[0033] Fig. 9 For samples 27 Al MAS-NMR spectrum.

[0034] Fig.10 For samples 31 P MAS-NMR spectrum.

[0035] Fig.11 The sample was treated with 800℃, 100% steam, and 17h hydrothermal aging. 31 P MAS-NMR spectrum.

[0036] Fig.12 For samples 27 Al MAS-NMR spectrum. DETAILED DESCRIPTION

[0037] The present invention will be further described below by way of examples, but the contents of the present invention are not limited thereto.

[0038] X-ray diffraction (XRD) spectra were measured on a Rigaku TTR-3 powder X-ray diffractometer. Instrument parameters: copper target (tube voltage 40 kV, tube current 250 mA), scintillation counter, step width 0.02°, scanning rate 0.4 (°) / min. The ZSM-5 molecular sieve synthesized by the method of Example 1 in CN1056818C was used as a standard sample, and its crystallinity was set to 100%. The relative crystallinity is expressed as a percentage of the sum of the peak areas of the five characteristic diffraction peaks at 2θ between 22.5 and 25.0° of the X-ray diffraction spectra of the obtained product and the standard sample.

[0039] 31 P MAS-NMR spectrum analysis was performed on a Bruker AVANCE III 600WB spectrometer. Instrument parameters: rotor diameter 4 mm, resonance spectrum 202.4 MHz, pulse width 0.4 μs (corresponding to 15° bevel angle), magic angle rotation speed 10 kHz. 31 P MAS-NMR spectrum characteristics, the peak area of ​​the resonance signal with a chemical shift of -30±3ppm and the peak area of ​​the resonance signal with a chemical shift of -40±3ppm were calculated after peak fitting.

[0040] 27 Al MAS-NMR spectrum analysis was performed on a Bruker AVANCE III 600WB spectrometer. Instrument parameters: rotor diameter 4 mm, resonance spectrum 156.4 MHz, pulse width 0.4 μs (corresponding to 15° bevel angle), magic angle rotation speed 12 kHz, delay time 1 s. 27 The characteristic peak at 39±3ppm of Al MAS-NMR spectrum belongs to the framework aluminum stabilized by phosphorus (distorted four-coordinate framework aluminum), and the half-peak full width of this characteristic peak is calculated after peak fitting.

[0041] X-ray photoelectron spectroscopy (XPS) was used to analyze phosphorus species on the molecular sieve surface and to investigate the valence changes of phosphorus compounds loaded on the phosphorus-modified molecular sieve after drying and calcination. The ESCALAB 250 X-ray photoelectron spectrometer from Thermo Fisher-VG was used. Instrument parameters: the excitation source was monochromatic AlKα X-ray with a power of 150 W, and the charge shift was corrected with the C1s peak (284.8 eV) from contaminated carbon.

[0042] Example 1

[0043] Take 6.9g of hypophosphorous acid and dissolve it in 145g of deionized water at 25°C, stir for 0.5h to obtain a phosphorus-containing aqueous solution, add 100g of HZSM-5 molecular sieve (nSiO2 / nAl2O3=30), and modify it by impregnation method. After impregnation at 25°C for 0.5h, move it to an oven and dry it at 120°C for 12h, and calcine it at 350°C in an air atmosphere in a muffle furnace for 2h. The obtained phosphorus-modified ZSM-5 molecular sieve sample is recorded as TCB-1.

[0044] Example 2

[0045] 6.9 g of solid hypophosphorous acid was added to 100 g of HZSM-5 molecular sieve (nSiO2 / nAl2O3=30), and the mixture was ground and mixed for 0.5 h, and then transferred to a Teflon-lined stainless steel autoclave for a melting process at a heating temperature of 40°C for 10 h. After the melting process, the sample was taken out after naturally cooling to room temperature. The above sample was calcined at 350°C for 2 h to obtain a phosphorus-containing ZSM-5 molecular sieve sample, which was recorded as TRCB-1.

[0046] Comparative Example 1

[0047] Take 13.9g of diammonium hydrogen phosphate and dissolve it in 145g of deionized water at 25°C, stir for 0.5h to obtain a phosphorus-containing aqueous solution, add 100g of HZSM-5 molecular sieve (nSiO2 / nAl2O3=30), and modify it by impregnation method. After impregnation at 25°C for 0.5h, move it to an oven and dry it at 120°C for 12h, and calcine it at 550°C in an air atmosphere in a muffle furnace for 2h. The obtained phosphorus-containing ZSM-5 molecular sieve comparison sample is recorded as DPB-1.

[0048] Comparative Example 2

[0049] Take 12.1g of phosphoric acid solution (mass fraction 85wt%) and dissolve it in 145g of deionized water at 25℃, stir for 0.5h to obtain a phosphorus-containing aqueous solution, add 100g of HZSM-5 molecular sieve (nSiO2 / nAl2O3=30), and modify it by impregnation method. After impregnation at 25℃ for 0.5h, move it to an oven and dry it at 120℃ for 12h, and calcine it at 550℃ in an air atmosphere in a muffle furnace for 2h to obtain a phosphorus-containing ZSM-5 molecular sieve comparison sample, recorded as DPB-2.

[0050] Comparative Example 3

[0051] Take 6.9g of hypophosphorous acid and dissolve it in 145g of deionized water at 25°C, stir for 0.5h to obtain a phosphorus-containing aqueous solution, add 100g of HZSM-5 molecular sieve (nSiO2 / nAl2O3=30), and modify it by impregnation method. After impregnation at 25°C for 0.5h, move it to an oven and dry it at 120°C for 12h, and calcine it at 550°C in an air atmosphere in a muffle furnace for 2h. The obtained phosphorus-modified ZSM-5 molecular sieve sample is recorded as JCB-1.

[0052] Samples TCB-1, TRCB-1, comparative samples DPB-1, DPB-2, JCB-1 31 P MAS-NMR spectrum is shown in Figure 1 . Figure 1 The characteristic peaks at chemical shifts of 0ppm, -6ppm and -15ppm are attributed to oligophosphate species such as monomeric phosphoric acid and pyrophosphate; the characteristic peaks in the range of -20 to -50ppm are attributed to polyphosphate species.

[0053] Samples TCB-1, TRCB-1, and comparative samples DPB-1, DPB-2, and JCB-1 were subjected to hydrothermal aging at 800°C, 100% steam, and 17h. 31 P MAS-NMR spectrum is shown in Figure 2 . Figure 2 The resonance signal with a chemical shift of -30±3ppm represents the tetracoordinated phosphorus species formed after stabilizing the framework aluminum species, and the resonance signal with a chemical shift of -40±3ppm represents the pentacoordinated phosphorus species formed by condensation. The peak area ratio of the -30±3ppm / -40±3ppm signal is shown in Table 1.

[0054] Figure 3 The samples TCB-1, TRCB-1, comparative samples DPB-1, DPB-2, and JCB-1 27 Al MAS-NMR spectrum.

[0055] The XRD relative crystallinity and crystal retention of samples TCB-1, TRCB-1, and comparative samples DPB-1, DPB-2, and JCB-1 before and after hydrothermal aging at 800°C, 100% water vapor, and 17h are shown in Table 2.

[0056] The phosphorus content retention rates of samples TCB-1, TRCB-1, and comparative samples DPB-1, DPB-2, and JCB-1 after washing are shown in Table 3.

[0057] Table 1

[0058] sample -30±3ppm / -40±3ppm signal peak area ratio TCB-1 1.2 TRCB-1 1.1 DPB-1 0.6 DPB-2 0.7 JCB-1 0.7

[0059] Table 2

[0060]

[0061] Table 3

[0062] sample Phosphorus content retention rate / % TCB-1 62 TRCB-1 61 DPB-1 45 DPB-2 48 JCB-1 49

[0063] Test Example 1

[0064] Samples TCB-1, TRCB-1, and comparative samples DPB-1, DPB-2, and JCB-1 were evaluated for cracking of n-tetradecane, and the microreactor evaluation conditions were: molecular sieve loading 2g, feed oil n-tetradecane, feed oil volume 1.56g, reaction temperature 550℃, and regeneration temperature 600℃ (the same below). The evaluation data are shown in Table 4.

[0065] Table 4

[0066]

[0067] Example 3

[0068] Take 3.45g of hypophosphorous acid and dissolve it in 145g of deionized water at 25°C, stir for 0.5h to obtain a phosphorus-containing aqueous solution, add 100g of HZSM-5 molecular sieve (nSiO2 / nAl2O3=30), and modify it by impregnation method. After impregnation at 25°C for 0.5h, move it to an oven and dry it at 120°C for 12h, and calcine it at 350°C in an air atmosphere in a muffle furnace for 2h. The obtained phosphorus-containing ZSM-5 molecular sieve sample is recorded as TCB-2.

[0069] Example 4

[0070] 3.45 g of solid hypophosphorous acid was added to 100 g of HZSM-5 molecular sieve (nSiO2 / nAl2O3=30), which was ground and mixed for 0.5 h and then transferred to a Teflon-lined stainless steel autoclave for a melting process at a heating temperature of 40°C for 10 h. After the melting process, the sample was taken out after naturally cooling to room temperature. The above sample was calcined at 350°C for 2 h to obtain a phosphorus-containing ZSM-5 molecular sieve sample, recorded as TRCB-2.

[0071] Comparative Example 4

[0072] Take 6.95g of diammonium hydrogen phosphate and dissolve it in 145g of deionized water at 25°C, stir for 0.5h to obtain a phosphorus-containing aqueous solution, add 100g of HZSM-5 molecular sieve (nSiO2 / nAl2O3=30), and modify it by impregnation method. After impregnation at 25°C for 0.5h, move it to an oven and dry it at 120°C for 12h, and calcine it at 550°C in an air atmosphere in a muffle furnace for 2h. The obtained phosphorus-containing ZSM-5 molecular sieve comparison sample is recorded as DPB-3.

[0073] Comparative Example 5

[0074] Take 6.05g of phosphoric acid solution (mass fraction 85wt%) and dissolve it in 145g of deionized water at 25℃, stir for 0.5h to obtain a phosphorus-containing aqueous solution, add 100g of HZSM-5 molecular sieve (nSiO2 / nAl2O3=30), and modify it by impregnation method. After impregnation at 25℃ for 0.5h, move it to an oven and dry it at 120℃ for 12h, and calcine it at 550℃ in an air atmosphere in a muffle furnace for 2h to obtain a phosphorus-containing ZSM-5 molecular sieve comparison sample, recorded as DPB-4.

[0075] Comparative Example 6

[0076] Take 3.45g of hypophosphorous acid and dissolve it in 145g of deionized water at 25°C, stir for 0.5h to obtain a phosphorus-containing aqueous solution, add 100g of HZSM-5 molecular sieve (nSiO2 / nAl2O3=30), and modify it by impregnation method. After impregnation at 25°C for 0.5h, move it to an oven and dry it at 120°C for 12h, and calcine it at 550°C in an air atmosphere in a muffle furnace for 2h. The obtained phosphorus-containing ZSM-5 molecular sieve sample is recorded as JCB-2.

[0077] Samples TCB-2, TRCB-2, comparative samples DPB-3, DPB-4, JCB-2 31 P MAS-NMR spectrum is shown in Figure 4 . Figure 4The characteristic peaks at chemical shifts of 0ppm, -6ppm and -15ppm are attributed to oligophosphate species such as monomeric phosphoric acid and pyrophosphate; the characteristic peaks in the range of -20 to -50ppm are attributed to polyphosphate species.

[0078] Samples TCB-2, TRCB-2, and comparative samples DPB-3, DPB-4, and JCB-2 were subjected to hydrothermal aging at 800°C, 100% steam, and 17h. 31 P MAS-NMR spectrum is shown in Figure 5 . Figure 5 The resonance signal with a chemical shift of -30±3ppm represents the tetracoordinated phosphorus species formed after stabilizing the framework aluminum species, and the resonance signal with a chemical shift of -40±3ppm represents the pentacoordinated phosphorus species formed by condensation. The peak area ratio of the -30±3ppm / -40±3ppm signal is shown in Table 5.

[0079] Figure 6 for 27 Al MAS-NMR spectrum

[0080] The XRD relative crystallinity and crystal retention of samples TCB-2, TRCB-2, and comparative samples DPB-3, DPB-4, and JCB-2 before and after hydrothermal aging at 800°C, 100% water vapor, and 17h are shown in Table 6.

[0081] The phosphorus content retention rates of samples TCB-2, TRCB-2, and comparative samples DPB-3, DPB-4, and JCB-2 after washing are shown in Table 7.

[0082] Table 5

[0083] sample -30±3ppm / -40±3ppm signal peak area ratio TCB-2 1.3 TRCB-2 1.2 DPB-3 0.7 DPB-4 0.7 JCB-2 0.8

[0084] Table 6

[0085]

[0086] Table 7

[0087] sample Phosphorus content retention rate / % TCB-2 70 TRCB-2 71 DPB-3 48 DPB-4 46 JCB-2 47

[0088] Test Example 2

[0089] Samples TCB-2, TRCB-2, and comparative samples DPB-3, DPB-4, and JCB-2 were evaluated for cracking of n-tetradecane, and the microreactor evaluation conditions were: molecular sieve loading 2g, feed oil n-tetradecane, feed oil volume 1.56g, reaction temperature 550℃, and regeneration temperature 600℃ (the same below). The evaluation data are shown in Table 8.

[0090] Table 8

[0091]

[0092] Example 5

[0093] Take 10.35g of hypophosphorous acid and dissolve it in 145g of deionized water at 25°C, add ammonia water to adjust the pH value of the solution to 5-9, stir for 0.5h to obtain a phosphorus-containing aqueous solution, add 100g of HZSM-5 molecular sieve (nSiO2 / nAl2O3=30), modify it by impregnation method, impregnate it at 25°C for 0.5h, then move it to an oven and dry it at 120°C for 12h, and calcine it at 350°C in an air atmosphere in a muffle furnace for 2h. The obtained phosphorus-containing ZSM-5 molecular sieve sample is recorded as TCB-3.

[0094] Example 6

[0095] 13.02 g of ammonium hypophosphite was added to 100 g of HZSM-5 molecular sieve (nSiO2 / nAl2O3=30), which was ground and mixed for 0.5 h and then transferred to a Teflon-lined stainless steel high-pressure reactor for a melting process at a heating temperature of 40°C for 10 h. After the melting process, the sample was taken out after naturally cooling to room temperature. The above sample was calcined at 350°C for 2 h to obtain a phosphorus-containing ZSM-5 molecular sieve sample, recorded as TRCB-3.

[0096] Comparative Example 7

[0097] Take 20.85g of diammonium hydrogen phosphate and dissolve it in 145g of deionized water at 25°C, stir for 0.5h to obtain a phosphorus-containing aqueous solution, add 100g of HZSM-5 molecular sieve (nSiO2 / nAl2O3=30), and modify it by impregnation method. After impregnation at 25°C for 0.5h, move it to an oven and dry it at 120°C for 12h, and calcine it at 550°C in an air atmosphere in a muffle furnace for 2h. The obtained phosphorus-containing ZSM-5 molecular sieve comparison sample is recorded as DPB-5.

[0098] Comparative Example 8

[0099] Take 18.15g of phosphoric acid solution (mass fraction 85wt%) and dissolve it in 145g of deionized water at 25℃, stir for 0.5h to obtain a phosphorus-containing aqueous solution, add 100g of HZSM-5 molecular sieve (nSiO2 / nAl2O3=30), and modify it by impregnation method. After impregnation at 25℃ for 0.5h, move it to an oven and dry it at 120℃ for 12h, and calcine it at 550℃ in an air atmosphere in a muffle furnace for 2h to obtain a phosphorus-containing ZSM-5 molecular sieve comparison sample, recorded as DPB-6.

[0100] Comparative Example 9

[0101] Take 10.35g of hypophosphorous acid and dissolve it in 145g of deionized water at 25°C, add ammonia water to adjust the pH value of the solution to 5-9, stir for 0.5h to obtain a phosphorus-containing aqueous solution, add 100g of HZSM-5 molecular sieve (nSiO2 / nAl2O3=30), and modify it by impregnation method. After impregnation at 25°C for 0.5h, move it to an oven and dry it at 120°C for 12h, and calcine it at 550°C in an air atmosphere in a muffle furnace for 2h. The obtained phosphorus-containing ZSM-5 molecular sieve sample is recorded as JCB-4.

[0102] Samples TCB-3, TRCB-3, comparative samples DPB-5, DPB-6, JCB-4 31 P MAS-NMR spectrum is shown in Figure 7 . Figure 7 The characteristic peaks at chemical shifts of 0ppm, -6ppm and -15ppm are attributed to oligophosphate species such as monomeric phosphoric acid and pyrophosphate; the characteristic peaks in the range of -20 to -50ppm are attributed to polyphosphate species.

[0103] Samples TCB-3, TRCB-3, and comparative samples DPB-5, DPB-6, and JCB-4 were subjected to hydrothermal aging at 800°C, 100% steam, and 17h. 31 P MAS-NMR spectrum is shown in Figure 8 . Figure 8 In the figure, the resonance signal with a chemical shift of -30±3ppm represents the tetracoordinated phosphorus species formed after stabilizing the framework aluminum species, and the resonance signal with a chemical shift of -40±3ppm represents the pentacoordinated phosphorus species formed by condensation. The peak area ratio of the -30±3ppm / -40±3ppm signal is shown in Table 9. Fig. 9 for 27 Al MAS-NMR spectrum

[0104] The XRD relative crystallinity and crystal retention of samples TCB-3, TRCB-3, and comparison samples DPB-5, DPB-6, and JCB-4 before and after hydrothermal aging at 800°C, 100% water vapor, and 17h are shown in Table 10.

[0105] The phosphorus content retention rates of samples TCB-3, TRCB-3, and comparative samples DPB-5, DPB-6, and JCB-4 were washed with water, as shown in Table 11.

[0106] Table 9

[0107] sample -30±3ppm / -40±3ppm signal peak area ratio TCB-3 1.2 TRCB-3 1.2 DPB-5 0.7 DPB-6 0.8 JCB-4 0.8

[0108] Table 10

[0109]

[0110] Table 11

[0111] sample Phosphorus content retention rate / % TCB-3 58 TRCB-3 55 DPB-5 42 DPB-6 41 JCB-4 45

[0112] Test Example 3

[0113] Samples TCB-3, TRCB-3, and comparative samples DPB-5, DPB-6, and JCB-4 were evaluated for cracking of n-tetradecane, respectively. Microreactor evaluation conditions: molecular sieve loading 2g, feed oil n-tetradecane, feed oil volume 1.56g, reaction temperature 550℃, regeneration temperature 600℃. Evaluation data are shown in Table 12.

[0114] Table 12

[0115]

[0116] Example 7

[0117] 1.36 g of ammonium hypophosphite was dissolved in 145 g of deionized water at 25 ° C, stirred for 0.5 h to obtain a phosphorus-containing aqueous solution, 100 g of HZSM-5 molecular sieve (nSiO2 / nAl2O3=100) was added, and modified by impregnation method. After impregnation at 25 ° C for 0.5 h, it was moved to an oven for drying at 120 ° C for 12 h, and calcined at 350 ° C in an air atmosphere in a muffle furnace for 2 h. The obtained phosphorus-containing ZSM-5 molecular sieve sample was recorded as TCB-4.

[0118] Comparative Example 10

[0119] Take 2.16g of diammonium hydrogen phosphate and dissolve it in 145g of deionized water at 25°C, stir for 0.5h to obtain a phosphorus-containing aqueous solution, add 100g of HZSM-5 molecular sieve (nSiO2 / nAl2O3=100), and modify it by impregnation method. After impregnation at 25°C for 0.5h, move it to an oven and dry it at 120°C for 12h, and calcine it at 550°C in an air atmosphere in a muffle furnace for 2h. The obtained phosphorus-containing ZSM-5 molecular sieve comparison sample is recorded as DPB-7.

[0120] Comparative Example 11

[0121] 1.36 g of ammonium hypophosphite was dissolved in 145 g of deionized water at 25 ° C, stirred for 0.5 h to obtain a phosphorus-containing aqueous solution, 100 g of HZSM-5 molecular sieve (nSiO2 / nAl2O3=100) was added, and modified by impregnation method. After impregnation at 25 ° C for 0.5 h, it was moved to an oven for drying at 120 ° C for 12 h, and calcined at 550 ° C in an air atmosphere in a muffle furnace for 2 h. The obtained phosphorus-containing ZSM-5 molecular sieve sample was recorded as JCB-5.

[0122] Example 8

[0123] 0.91g of ammonium hypophosphite was dissolved in 145g of deionized water at 25°C, stirred for 0.5h to obtain a phosphorus-containing aqueous solution, 100g of HZSM-5 molecular sieve (nSiO2 / nAl2O3=150) was added, and the solution was modified by impregnation. After impregnation at 25°C for 0.5h, the solution was moved to an oven for drying at 120°C for 12h, and calcined at 350°C in an air atmosphere in a muffle furnace for 2h. The phosphorus-containing ZSM-5 molecular sieve sample was obtained, which was recorded as TCB-5.

[0124] Comparative Example 12

[0125] Take 1.45g of diammonium hydrogen phosphate and dissolve it in 145g of deionized water at 25°C, stir for 0.5h to obtain a phosphorus-containing aqueous solution, add 100g of HZSM-5 molecular sieve (nSiO2 / nAl2O3=150), and modify it by impregnation method. After impregnation at 25°C for 0.5h, move it to an oven and dry it at 120°C for 12h, and calcine it at 550°C in an air atmosphere in a muffle furnace for 2h. The obtained phosphorus-containing ZSM-5 molecular sieve comparison sample is recorded as DPB-8.

[0126] Comparative Example 13

[0127] Take 0.91g of ammonium hypophosphite and dissolve it in 145g of deionized water at 25°C, stir for 0.5h to obtain a phosphorus-containing aqueous solution, add 100g of HZSM-5 molecular sieve (nSiO2 / nAl2O3=150), and modify it by impregnation method. After impregnation at 25°C for 0.5h, move it to an oven and dry it at 120°C for 12h, and calcine it at 550°C in an air atmosphere in a muffle furnace for 2h. The obtained phosphorus-containing ZSM-5 molecular sieve sample is recorded as JCB-6.

[0128] Sample TCB-4, comparative sample DPB-7, comparative sample JCB-5, sample TCB-5, comparative sample DPB-8, comparative sample JCB-6 31 P MAS-NMR spectrum is shown in Fig.10 . Fig.10 The characteristic peaks at chemical shifts of 0ppm, -6ppm and -15ppm are attributed to oligophosphate species such as monomeric phosphoric acid and pyrophosphate; the characteristic peaks in the range of -20 to -50ppm are attributed to polyphosphate species.

[0129] Sample TCB-4, comparative sample DPB-7, comparative sample JCB-5, sample TCB-5, comparative sample DPB-8, comparative sample JCB-6 were subjected to 800℃, 100% steam, 17h hydrothermal aging treatment respectively. 31 P MAS-NMR spectrum is shown in Fig.11 . Fig.11The resonance signal with a chemical shift of -30±3ppm represents the tetracoordinated phosphorus species formed after stabilizing the framework aluminum species, and the resonance signal with a chemical shift of -40±3ppm represents the pentacoordinated phosphorus species formed by condensation. The peak area ratio of the -30±3ppm / -40±3ppm signal is shown in Table 13.

[0130] Fig.12 for 27 Al MAS-NMR spectrum.

[0131] The XRD relative crystallinity and crystal retention of sample TCB-4, comparison sample DPB-7, comparison sample JCB-5, sample TCB-5, comparison sample DPB-8 and comparison sample JCB-6 before and after hydrothermal aging treatment at 800°C, 100% water vapor and 17h are shown in Table 14.

[0132] Sample TCB-4, comparison sample DPB-7, comparison sample JCB-5, sample TCB-5, comparison sample DPB-8, and comparison sample JCB-6 were washed with water, and the phosphorus content retention rate is shown in Table 15.

[0133] Table 13

[0134] sample -30±3ppm / -40±3ppm signal peak area ratio TCB-4 1.2 DPB-7 0.7 JCB-5 0.8 TCB-5 1.1 DPB-8 0.7 JCB-6 0.7

[0135] Table 14

[0136]

[0137] Table 15

[0138]

[0139] Test Example 4

[0140] Sample TCB-4, comparative sample DPB-7, comparative sample JCB-5, sample TCB-5, comparative sample DPB-8, and comparative sample JCB-6 were evaluated for the cracking of n-tetradecane, and the micro-reactor evaluation conditions were: molecular sieve loading 2g, feed oil n-tetradecane, oil feed volume 1.56g, reaction temperature 550°C, and regeneration temperature 600°C. The evaluation data are shown in Table 16.

[0141] Table 16

[0142]

Claims

1. A phosphorus-modified ZSM-5 molecular sieve, characterized in that: That 31 In the P MAS-NMR spectrum, the chemical shift range of the resonance signal peak is 5 to -20 ppm.

2. The molecular sieve according to claim 1, characterized in that After the molecular sieve was hydrothermally aged at 800°C and 100% steam for 17 hours, 31 In the P MAS-NMR spectrum, the ratio of the peak area of ​​the resonance signal with a chemical shift of -30±3 ppm to the peak area of ​​the resonance signal with a chemical shift of -40±3 ppm is >1, preferably 1.05 to 1.4, more preferably 1.1 to 1.

3.

3. The molecular sieve according to claim 1, characterized in that After the molecular sieve was hydrothermally aged at 800°C and 100% steam for 17 hours, 27 In the Al MAS-NMR spectrum, resonance signal peaks with chemical shifts of 39±3ppm and -12±3ppm appeared simultaneously.

4. The molecular sieve according to claim 1, characterized in that: After the molecular sieve is washed with hot water at 70° C. for 2 hours, the phosphorus content retention rate is higher than 50%, about 51-75%, and the phosphorus content retention rate is defined as P2O5 before washing / P2O5 after washing, calculated as mass percentage.

5. The molecular sieve according to claim 1, characterized in that When phosphorus and aluminum are measured in moles, the ratio between the two is 0.01 to 5.

6. The molecular sieve according to claim 5, characterized in that The ratio is 0.1-3.

7. The molecular sieve according to claim 1, characterized in that The molecular sieve is modified with a phosphorus-containing compound having a phosphorus valence state of +1 and is obtained through a step including calcination in air at 300-400°C.

8. The method for preparing the phosphorus-modified ZSM-5 molecular sieve according to any one of claims 1 to 7, characterized in that: The HZSM-5 molecular sieve is contacted and impregnated with an aqueous solution of a phosphorus-containing compound with a phosphorus valence state of +1, and then dried and air-roasted at 300-400°C to obtain a phosphorus-modified ZSM-5 molecular sieve; or the HZSM-5 molecular sieve is mixed and ground with a solid phosphorus-containing compound with a phosphorus valence state of +1 to obtain a mixture, which is heated and melted, cooled to 20-25°C, and then air-roasted at 300-400°C to obtain a phosphorus-modified ZSM-5 molecular sieve.

9. The preparation method according to claim 8, characterized in that: The impregnation has a water-to-screen weight ratio of 0.5-2 and is carried out at room temperature for 0.5-10 hours; the drying is carried out in air at 100-120°C for 2-24 hours; and the calcination is carried out at 330-370°C for 0.5-12 hours.

10. The preparation method according to claim 8, characterized in that: The calcination is carried out at 350°C.

11. The preparation method according to claim 8, characterized in that: The heating and melting treatment has a temperature higher than the melting point of the solid phosphorus-containing compound and lower than the temperature at which the solid phosphorus-containing compound decomposes or dehydrates, and the treatment time is 2 to 72 hours.

12. The preparation method according to claim 8, characterized in that: The phosphorus-containing compound with a phosphorus valence state of +1 is selected from one or more of hypophosphorous acid, ammonium hypophosphite, and hypophosphite; or, the aqueous solution of the phosphorus-containing compound with a phosphorus valence state of +1 is an aqueous solution of hypophosphorous acid adjusted to a pH value of 5-9 with ammonia water.

13. The preparation method according to claim 8, characterized in that: The molar ratio of the HZSM-5 molecular sieve to the phosphorus-containing compound with a phosphorus valence state of +1 is (0.1-2.5):1, wherein the HZSM-5 molecular sieve is calculated as aluminum and the phosphorus-containing compound is calculated as phosphorus.

14. The preparation method according to claim 8, characterized in that: The molar ratio of the HZSM-5 molecular sieve to the phosphorus-containing compound with a phosphorus valence state of +1 is (0.5-1.5):

1.

15. The phosphorus-modified ZSM-5 molecular sieve obtained by the preparation method according to any one of claims 8 to 14.

16. A catalytic cracking method, characterized in that The phosphorus-modified ZSM-5 molecular sieve according to any one of claims 1 to 7 and 15 is used as a catalyst.

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