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

Abstract

The phosphorus modified ZSM-5 molecular sieve is characterized in that, after hydrothermal aging at 800 DEG C under 100% water vapor for 17 hours, the binding energy of phosphorus element in surface phosphorus species of the molecular sieve is 134.6-134.7 eV, 27 In the spectrum of Al MAS-NMR, the full width at half maximum of the resonance signal peak with a chemical shift of 39±3ppm is 10-25ppm.

Description

Technical Field

[0001] This invention relates to a modified ZSM-5 molecular sieve and its preparation method, and more particularly to a phosphorus-modified ZSM-5 molecular sieve and its preparation method. Background Technology

[0002] ZSM-5 molecular sieve (USP3702886) is a high-silica, three-dimensional, straight-channel mesoporous molecular sieve with an MFI structure, developed by Mobil Petroleum Corporation in the United States. Its unique pore structure endows it with excellent shape-selective catalysis and isomerization performance. It also features high thermal and hydrothermal stability, high specific surface area, a wide range of silica-to-alumina ratios, unique surface acidity, and low carbon deposition. ZSM-5 molecular sieve is widely used as a catalyst and catalyst support, and has been successfully applied in alkylation, isomerization, disproportionation, catalytic cracking, methanol-to-gasoline, and methanol-to-olefins production processes.

[0003] Since 1983, ZSM-5 molecular sieves have been used as octane enhancers in catalytic cracking processes to improve the octane number and selectivity of low-carbon olefins in catalytic cracked gasoline. US3758403 first reported the use of ZSM-5 molecular sieves as an active component for enhancing propylene production; it was used in conjunction with REY as an active component in FCC catalysts. US5997728 disclosed the use of unmodified ZSM-5 molecular sieves as an additive for enhancing propylene production, but the propylene yields were not high. While HZSM-5 molecular sieves possess good shape selectivity and isomerization properties, their drawback is poor hydrothermal stability; they are prone to deactivation under harsh high-temperature hydrothermal conditions, leading to reduced catalytic performance.

[0004] In the 1980s, Mobil discovered that phosphorus could improve the hydrothermal stability of ZSM-5 molecular sieves, and that phosphorus modification of ZSM-5 molecular sieves increased the yield of low-carbon olefins. Commonly used ZSM-5 additives, activated by phosphorus, selectively convert primary cracking products (such as gasoline olefins) into C3 and C4 olefins. Post-synthesis modification of ZSM-5 molecular sieves with appropriate amounts of inorganic phosphorus compounds can stabilize the skeletal aluminum framework under harsh hydrothermal conditions.

[0005] CN 1211469A discloses a five-membered ring molecular sieve composition that produces high yields of propylene and ethylene, comprising 85-95 wt% of a five-membered ring molecular sieve, 2-10 wt% of phosphorus (based on oxides), 0.3-5 wt% of alkaline earth metals (based on oxides), and 0.3-5 wt% of transition metal elements (based on oxides). This composition yields high ethylene yields when used in catalytic thermal cracking reactions.

[0006] US5171921 discloses a phosphorus-modified ZSM-5 molecular sieve with a silicon-to-aluminum ratio of 20-60. After being impregnated with a phosphorus-containing compound and treated with steam at 500-700°C, it exhibits higher activity than untreated HZSM-5 when used in the reaction of converting C3-C20 hydrocarbons into C2-C5 olefins.

[0007] CN102166533A discloses a method for preparing phosphorus-modified ZSM-5 molecular sieves. The method involves adding the molecular sieve to a phosphorus-containing aqueous solution and reacting it for a period of time under specific pH, temperature, and pressure conditions. The resulting product is then filtered, dried, and calcined to obtain the phosphorus-modified molecular sieve. Subsequently, the phosphorus-modified molecular sieve is added to an aqueous solution containing rare earth ions and reacted for a period of time under specific temperature and pressure conditions. This is followed by filtration, washing, drying, and calcination to obtain a composite modified molecular sieve. Model catalysts prepared using this composite modified molecular sieve exhibit higher hydrothermal stability and micro-activity compared to model catalysts containing unmodified molecular sieves or those modified by other methods.

[0008] CN106994364A discloses a method for preparing phosphorus-modified ZSM-5 molecular sieves. The method involves 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 containing high alkali metal ions to obtain a mixture with a phosphorus loading of at least 0.1 wt% (based on P2O5). The mixture is then dried, calcined, and subjected to ammonium ion exchange and water washing steps to reduce the alkali metal ion content to below 0.10 wt%. Finally, it undergoes drying and hydrothermal aging at 400-1000℃ under 100% steam conditions. The phosphorus-containing ZSM-5 molecular sieve obtained by this method has a high total acid content, excellent cracking conversion rate and propylene selectivity, and a high liquefied gas yield.

[0009] Although modifying ZSM-5 molecular sieves with organic / inorganic phosphorus compounds can inhibit framework dealuminization and thus improve hydrothermal stability, the introduction of phosphorus species also plays a role in regulating the acid center properties of ZSM-5 molecular sieves, thereby improving the cracking conversion rate of long-chain alkanes and the selectivity of low-carbon olefins. However, during the roasting process of existing technologies, phosphoric acid or ammonium phosphate salts will generate large molecular phosphoric acid species such as polyphosphoric acid due to dehydration and self-polymerization. These species are easily enriched on the outer surface of the molecular sieve, clogging the pores, reducing the pore volume and specific surface area, resulting in low phosphorus aluminum activation efficiency. Therefore, phosphorus modification cannot achieve the ideal effect of improving hydrothermal stability. Summary of the Invention

[0010] Based on extensive experiments, the inventors discovered that treating ZSM-5 molecular sieves with inorganic phosphorus compounds of +1 valence, such as hypophosphoric acid and ammonium hypophosphorus salts, as a phosphorus source can promote the activation and coordination of phosphorus with skeletal aluminum. The resulting phosphorus-modified ZSM-5 molecular sieve exhibits physicochemical characteristics different from conventional phosphorus-containing ZSM-5 molecular sieves, with improved phosphorus-aluminum stability. Particularly in industrial applications, after aging, the hydrothermal stability, pyrolysis activity, and low-carbon olefin selectivity of this phosphorus-modified ZSM-5 molecular sieve are all improved. Based on this, the present invention was developed.

[0011] The purpose of this invention is to overcome the problems of unsatisfactory hydrothermal stability, pyrolysis activity and low-carbon olefin selectivity in the prior art, and to provide a phosphorus-modified ZSM-5 molecular sieve that is different from the prior art and to provide its preparation method.

[0012] To achieve the above objectives, a first aspect of the present invention is to provide a phosphorus-modified ZSM-5 molecular sieve, characterized in that, after hydrothermal aging at 800°C and 100% steam for 17 hours, the binding energy of phosphorus in the phosphorus species on the surface of the molecular sieve is 134.6–134.7 eV.

[0013] The binding energy of phosphorus in the XPS characterization results represents its chemical environment and valence state, and can indicate the degree of condensation and valence state transition of phosphorus species in the molecular sieve. In the aforementioned molecular sieve, after hydrothermal aging, the binding energy of phosphorus is 134.6–134.7 eV. In contrast, in existing technologies using phosphoric acid-modified molecular sieves, since there is no valence state transition, the binding energy remains almost unchanged after drying and aging, at 134.8–134.9 eV.

[0014] Furthermore, the molecular sieve of the present invention is subjected to hydrothermal aging at 800°C and 100% steam for 17 hours, and its properties are then measured. 27 In Al MAS-NMR spectra, the full width at half maximum (FWHM) of the resonance signal peak with a chemical shift of 39 ± 3 ppm is 10–25 ppm; preferably, it is 15–25 ppm. The resonance signal with a chemical shift of 39 ± 3 ppm represents a skeletal aluminum species stabilized after coordination with phosphorus species, i.e., a twisted four-coordinated skeletal aluminum species. A larger FWHM value of 39 ± 3 ppm indicates a greater number and variety of phosphorus-stabilized skeletal aluminum species, and the specific binding mode of the phosphorus-aluminum species may also differ. In existing technologies, the FWHM of the 39 ± 3 ppm resonance signal peak of ZSM-5 molecular sieve modified with phosphorus-containing precursors such as diammonium hydrogen phosphate or phosphoric acid (with a +5 valence) is 5–10 ppm.

[0015] The molecular sieve, when both phosphorus and aluminum are measured in molar quantities, has a ratio of 0.01 to 5, with a preferred ratio of 0.1 to 3.

[0016] In one embodiment of the molecular sieve, the molecular sieve is obtained by modification with a phosphorus-containing compound in which phosphorus has a +1 oxidation state.

[0017] To achieve the above objectives, a second aspect of the present invention provides a method for preparing the phosphorus-containing ZSM-5 molecular sieve, characterized in that: HZSM-5 molecular sieve is impregnated with an aqueous solution of a phosphorus-containing compound with a phosphorus oxidation state of +1 at room temperature (e.g., 20-25°C), followed by drying and calcination to obtain the phosphorus-containing ZSM-5 molecular sieve; or, the mixture obtained by mixing and grinding HZSM-5 molecular sieve with a solid phosphorus-containing compound with a phosphorus oxidation state of +1 is heated and melted, then cooled to room temperature (e.g., 20-25°C) and calcined to obtain the phosphorus-containing ZSM-5 molecular sieve.

[0018] The preparation method of phosphorus-containing ZSM-5 molecular sieve provided by the present invention includes two methods: impregnation with an aqueous solution of +1 valent phosphorus precursor and heating and melting treatment.

[0019] In one embodiment of the present invention, the water is impregnated in an aqueous solution at a weight ratio of 0.5 to 2 for 0.5 to 10 hours; the drying is carried out in an air atmosphere at 100 to 120°C for 2 to 24 hours; and the calcination is carried out in an air atmosphere at 200 to 800°C for 0.5 to 12 hours.

[0020] In one embodiment of the invention, a 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, hypophosphoric acid has a melting point of 26.5°C and a decomposition temperature of 130°C), for a treatment time of 2 to 72 hours.

[0021] In the preparation method provided by this invention, HZSM-5 molecular sieves are treated with phosphorus-containing compounds with a phosphorus oxidation state of +1. By selecting a phosphorus source with a relatively small +1 oxidation state, the migration process of phosphorus species into the pores of ZSM-5 molecular sieves is accelerated, thereby increasing the activation efficiency of phosphorus-aluminum species. The phosphorus-containing compounds with a phosphorus oxidation state of +1 are selected from hypophosphorous acid, ammonium hypophosphorus salts, etc., which serve as phosphorus-containing precursors. After calcination, phosphorus is converted from a +1 oxidation state to a higher oxidation state and possesses the conditions to stabilize the skeletal aluminum during the aging process.

[0022] The phosphorus-containing ZSM-5 molecular sieve provided by this invention exhibits significant coordination between phosphorus species and framework aluminum, thus fully protecting the framework aluminum. After hydrothermal aging at 800℃ and 100% steam for 17 hours, it demonstrates higher crystallinity retention (95%–110%), resulting in excellent hydrothermal stability for the phosphorus-modified ZSM-5 molecular sieve. The phosphorus-modified ZSM-5 molecular sieve of this invention can be used as a catalyst in catalytic cracking reactions. For example, in the cracking reaction of n-tetradecane, key indicators are improved compared to comparative samples, such as higher conversion rate and liquefied gas yield, while the yields of trienes (ethylene, propylene, and butene) are significantly increased. Attached Figure Description

[0023] Figure 1 For JCB-1 and DPB-1 27 Al MAS-NMR spectrum.

[0024] Figure 2 XPS (P2p Scan) spectra of JCB-1 and DPB-1.

[0025] Figure 3 For JCB-2 and DPB-3 27 Al MAS-NMR spectrum.

[0026] Figure 4 This is the XPS (P2p Scan) spectrum of JCB-2.

[0027] Figure 5 For JNB-3 and DPB-5 27 Al MAS-NMR spectrum.

[0028] Figure 6 This is the XPS (P2p Scan) spectrum of JNB-3. Detailed Implementation

[0029] The present invention will be further illustrated by the following examples, but these examples do not limit the scope of the invention.

[0030] X-ray diffraction (XRD) patterns were determined using 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°, scan rate 0.4 (°) / min. ZSM-5 molecular sieve synthesized using the method in Example 1 of CN1056818C was used as a standard, and its crystallinity was defined as 100%. Relative crystallinity was expressed as a percentage, representing the sum of the peak areas of the five characteristic diffraction peaks between 2θ and 25.0° in the X-ray diffraction patterns of the obtained product and the standard.

[0031] 27Al MAS-NMR spectral analysis was performed using a Bruker AVANCE III 600WB spectrometer. Instrument parameters: rotor diameter 4 mm, resonance spectrum 156.4 MHz, pulse width 0.4 μs (corresponding to a 15° chamfer), magic angle rotation speed 12 kHz, and delay time 1 s. 27 The Al MAS-NMR spectrum features a characteristic peak at 39±3 ppm, which is attributed to phosphorus-stable framework aluminum (twisted four-coordinate framework aluminum). The full width at half maximum (FWHM) of this characteristic peak is calculated by fitting the peaks.

[0032] X-ray photoelectron spectroscopy (XPS) was used for the analysis of phosphorus species on the surface of molecular sieves. The valence state changes of phosphorus compounds loaded on phosphorus-modified molecular sieves after drying and calcination were investigated using a Thermo Fisher-VG ESCALAB 250 X-ray photoelectron spectrometer. Instrument parameters: The excitation source was monochromatic AlKα X-rays with a power of 150 W; the charge shift was corrected using the C1s peak (284.8 eV) from contaminating carbon.

[0033] Example 1

[0034] 6.9 g of hypophosphoric acid was dissolved in 145 g of deionized water at 25 °C and stirred for 0.5 h to obtain a phosphorus-containing aqueous solution. 100 g of HZSM-5 molecular sieve (nSiO2 / nAl2O3 = 30) was added, and the solution was modified by impregnation. After impregnation at 25 °C for 0.5 h, the solution was transferred to an oven and dried at 120 °C for 12 h. The solution was then calcined in an air atmosphere in a muffle furnace at 550 °C for 2 h. The resulting phosphorus-modified ZSM-5 molecular sieve sample was designated JCB-1.

[0035] Example 2

[0036] 8.7g of ammonium hypophosphate was dissolved in 145g of deionized water at 25℃ and stirred for 0.5h to obtain a phosphorus-containing aqueous solution. 100g of HZSM-5 molecular sieve (nSiO2 / nAl2O3=30) was added, and the solution was modified by impregnation. After impregnation at 25℃ for 0.5h, the solution was transferred to an oven and dried at 120℃ for 12h. The solution was then calcined in an air atmosphere in a muffle furnace at 550℃ for 2h. The resulting phosphorus-modified ZSM-5 molecular sieve sample was designated JNB-1.

[0037] Example 3

[0038] 6.9g of solid hypophosphoric acid was added to 100g of HZSM-5 molecular sieve (nSiO2 / nAl2O3=30), and the mixture was ground and mixed for 0.5h. The mixture was then transferred to a Teflon-lined stainless steel high-pressure reactor for a melting process at 40℃ for 10h. After the process was completed, the sample was allowed to cool to room temperature naturally before being removed. The sample was then calcined at 550℃ for 2h to obtain a phosphorus-containing ZSM-5 molecular sieve sample, denoted as RCB-1.

[0039] Example 4

[0040] 8.7g of solid ammonium hypophosphite was added to 100g of HZSM-5 molecular sieve (nSiO2 / nAl2O3=30), and the mixture was ground and mixed for 0.5h. The mixture was then transferred to a Teflon-lined stainless steel high-pressure reactor for a melting process at 40℃ for 10h. After the melting process, the sample was allowed to cool to room temperature naturally before being removed. The sample was then calcined at 550℃ for 2h to obtain a phosphorus-containing ZSM-5 molecular sieve sample, denoted as RNB-1.

[0041] Comparative Example 1

[0042] 13.9g of diammonium hydrogen phosphate was dissolved in 145g of deionized water at 25℃ and stirred for 0.5h to obtain a phosphorus-containing aqueous solution. 100g of HZSM-5 molecular sieve (nSiO2 / nAl2O3=30) was added and modified by impregnation. After impregnation at 25℃ for 0.5h, the solution was transferred to an oven and dried at 120℃ for 12h. Then, it was calcined in an air atmosphere in a muffle furnace at 550℃ for 2h. The resulting phosphorus-containing ZSM-5 molecular sieve control sample was designated as DPB-1.

[0043] Comparative Example 2

[0044] 12.1 g of phosphoric acid solution (85 wt%) was dissolved in 145 g of deionized water at 25 °C and stirred for 0.5 h to obtain a phosphorus-containing aqueous solution. 100 g of HZSM-5 molecular sieve (nSiO2 / nAl2O3 = 30) was added, and the solution was modified by impregnation. After impregnation at 25 °C for 0.5 h, the solution was transferred to an oven and dried at 120 °C for 12 h. The solution was then calcined in an air atmosphere in a muffle furnace at 550 °C for 2 h. The resulting phosphorus-containing ZSM-5 molecular sieve control sample was designated as DPB-2.

[0045] The relative crystallinity and crystal retention of samples JCB-1, JNB-1, RCB-1, RNB-1, and control samples DPB-1 and DPB-2 before and after hydrothermal aging treatment at 800℃ and 100% water vapor for 17h are shown in Table 1.

[0046] Sample JCB-1 and control sample DPB-1 27 The Al MAS-NMR spectrum is shown below. Figure 1 . Figure 1 In the sample JNB-1, RCB-1, and RNB-1, the characteristic peak at a chemical shift of 39 ppm is attributed to a distorted four-coordinate framework aluminum formed by the combination of phosphorus and aluminum, i.e., a framework aluminum stabilized by phosphorus species. 27 Al MAS-NMR spectral characteristics and sample JCB-1 Figure 1 They share the same characteristics.

[0047] The full width at half maximum (FWHM) data of the characteristic peaks at 39 ppm for samples JCB-1, JNB-1, RCB-1, RNB-1, and control samples DPB-1 and DPB-2 are shown in Table 2.

[0048] XPS (P2p Scan) spectra of sample JCB-1 and control sample DPB-1 are shown below. Figure 2 In the figure, peaks of 134.2 eV and 134.6 eV represent the electron binding energies of phosphorus in the surface phosphorus species of sample JCB-1 after drying at 120℃ during preparation and after hydrothermal aging at 800℃ with 100% water vapor for 17 h, respectively. Peaks of 134.8 eV and 134.9 eV represent the corresponding electron binding energies of phosphorus in the surface phosphorus species of comparative sample DPB-1 after drying and hydrothermal aging, respectively. The XPS (P2p Scan) spectral characteristics of the electron binding energies of phosphorus in the surface phosphorus species of samples JNB-1, RCB-1, and RNB-1 after hydrothermal aging at 800℃ with 100% water vapor for 17 h are compared with those of sample JCB-1. Figure 2 They share the same characteristics.

[0049] Table 1

[0050]

[0051] Table 2

[0052] JCB-1 17 JNB-1 19 RCB-1 16 RNB-1 18 DPB-1 7 DPB-2 9

[0053] Test Example 1

[0054] JCB-1, JNB-1, RCB-1, RNB-1, DPB-1, and DPB-2 were used to evaluate the cracking of n-tetradecane. The microreactor evaluation conditions were as follows: molecular sieve loading 2g, feedstock n-tetradecane, feed rate 1.56g, reaction temperature 550℃, and regeneration temperature 600℃ (the same applies below). Evaluation data are shown in Table 3.

[0055] Table 3

[0056]

[0057] Example 5

[0058] 3.45 g of hypophosphoric acid was dissolved in 145 g of deionized water at 25 °C and stirred for 0.5 h to obtain a phosphorus-containing aqueous solution. 100 g of HZSM-5 molecular sieve (nSiO2 / nAl2O3 = 30) was added, and the solution was modified by impregnation. After impregnation at 25 °C for 0.5 h, the solution was transferred to an oven and dried at 120 °C for 12 h. The solution was then calcined in an air atmosphere in a muffle furnace at 550 °C for 2 h. The resulting phosphorus-containing ZSM-5 molecular sieve sample was designated JCB-2.

[0059] Example 6

[0060] 4.4 g of ammonium hypophosphate was dissolved in 145 g of deionized water at 25 °C and stirred for 0.5 h to obtain a phosphorus-containing aqueous solution. 100 g of HZSM-5 molecular sieve (nSiO2 / nAl2O3 = 30) was added, and the solution was modified by impregnation. After impregnation at 25 °C for 0.5 h, the solution was transferred to an oven and dried at 120 °C for 12 h. The solution was then calcined in an air atmosphere in a muffle furnace at 550 °C for 2 h. The resulting phosphorus-containing ZSM-5 molecular sieve sample was designated as JNB-2.

[0061] Example 7

[0062] 3.45g of solid hypophosphoric acid was added to 100g of HZSM-5 molecular sieve (nSiO2 / nAl2O3=30), and the mixture was ground and mixed for 0.5h. The mixture was then transferred to a Teflon-lined stainless steel high-pressure reactor for a melting process at 40℃ for 10h. After the melting process, the sample was allowed to cool to room temperature naturally before being removed. The sample was then calcined at 550℃ for 2h to obtain a phosphorus-containing ZSM-5 molecular sieve sample, denoted as RCB-2.

[0063] Example 8

[0064] 4.4g of solid ammonium hypophosphite was added to 100g of HZSM-5 molecular sieve (nSiO2 / nAl2O3=30), and the mixture was ground and mixed for 0.5h. The mixture was then transferred to a Teflon-lined stainless steel high-pressure reactor for a melting process at 40℃ for 10h. After the melting process, the sample was allowed to cool to room temperature naturally before being removed. The sample was then calcined at 550℃ for 2h to obtain a phosphorus-containing ZSM-5 molecular sieve sample, denoted as RNB-2.

[0065] Comparative Example 3

[0066] 6.95g of diammonium hydrogen phosphate was dissolved in 145g of deionized water at 25℃ and stirred for 0.5h to obtain a phosphorus-containing aqueous solution. 100g of HZSM-5 molecular sieve (nSiO2 / nAl2O3=30) was added and modified by impregnation. After impregnation at 25℃ for 0.5h, the solution was transferred to an oven and dried at 120℃ for 12h. Then, it was calcined in an air atmosphere in a muffle furnace at 550℃ for 2h. The resulting phosphorus-containing ZSM-5 molecular sieve control sample was designated as DPB-3.

[0067] Comparative Example 4

[0068] 6.05 g of phosphoric acid solution (85 wt%) was dissolved in 145 g of deionized water at 25 °C and stirred for 0.5 h to obtain a phosphorus-containing aqueous solution. 100 g of HZSM-5 molecular sieve (nSiO2 / nAl2O3 = 30) was added, and the solution was modified by impregnation. After impregnation at 25 °C for 0.5 h, the solution was transferred to an oven and dried at 120 °C for 12 h. The solution was then calcined in an air atmosphere in a muffle furnace at 550 °C for 2 h. The resulting phosphorus-containing ZSM-5 molecular sieve control sample was designated as DPB-4.

[0069] The relative crystallinity and crystal retention of samples JCB-2, JNB-2, RCB-2, RNB-2, and control samples DPB-3 and DPB-4 before and after hydrothermal aging treatment at 800℃ and 100% water vapor for 17 hours are shown in Table 4.

[0070] Sample JCB-2 and control sample DPB-3 27 The Al MAS-NMR spectrum is shown below. Figure 3 In the figure, the characteristic peak with a chemical shift of 39 ppm is attributed to the twisted four-coordinate framework aluminum formed after phosphorus and aluminum combine, i.e., the framework aluminum stabilized by phosphorus species. Samples JNB-2, RCB-2, and RNB-2... 27 Al MAS-NMR spectral characteristics and sample JCB-2 Figure 3 They share the same characteristics.

[0071] The characteristic peaks at 39 ppm of the chemical shifts of samples JCB-2, JNB-2, RCB-2, RNB-2, and comparative samples DPB-3 and DPB-4 are shown in Table 5.

[0072] The XPS (P2p Scan) spectrum of sample JCB-2 is shown below. Figure 4In the figure, the peaks of 134.3 eV and 134.7 eV represent the electron binding energy of phosphorus in the surface phosphorus species of sample JCB-2 after drying at 120℃ during the preparation process, and the electron binding energy of phosphorus in the surface phosphorus species of sample JCB-2 after hydrothermal aging at 800℃ and 100% water vapor for 17 h, respectively. The XPS (P2p Scan) spectral characteristics of the electron binding energy of phosphorus in the surface phosphorus species of samples JNB-2, RCB-2, and RNB-2 after hydrothermal aging at 800℃ and 100% water vapor for 17 h are compared with those of sample JCB-2. Figure 4 They share the same characteristics.

[0073] Table 4

[0074]

[0075] Table 5

[0076] JCB-2 17 JNB-2 19 RCB-2 18 RNB-2 19 DPB-3 8 DPB-4 8

[0077] Test Example 2

[0078] Samples JCB-2, JNB-2, RCB-2, and RNB-2 were compared with samples DPB-3 and DPB-4 for n-tetradecane cracking evaluation. The microreactor evaluation conditions were: molecular sieve loading 2g, feedstock n-tetradecane, feed rate 1.56g, reaction temperature 550℃, and regeneration temperature 600℃ (the same below). The evaluation data are shown in Table 6.

[0079] Table 6

[0080]

[0081] Example 9

[0082] 13.02 g of ammonium hypophosphite was dissolved in 145 g of deionized water at 25 °C and stirred for 0.5 h to obtain a phosphorus-containing aqueous solution. 100 g of HZSM-5 molecular sieve (nSiO2 / nAl2O3 = 30) was added, and the solution was modified by impregnation. After impregnation at 25 °C for 0.5 h, the solution was transferred to an oven and dried at 120 °C for 12 h. The solution was then calcined in an air atmosphere in a muffle furnace at 550 °C for 2 h. The resulting phosphorus-containing ZSM-5 molecular sieve sample was designated JNB-3.

[0083] Example 10

[0084] 13.02g of ammonium hypophosphate was added to 100g of HZSM-5 molecular sieve (nSiO2 / nAl2O3=30), and the mixture was ground and mixed for 0.5h. The mixture was then transferred to a Teflon-lined stainless steel high-pressure reactor for a melting process at 40℃ for 10h. After the melting process, the sample was allowed to cool to room temperature naturally before being removed. The sample was then calcined at 550℃ for 2h to obtain a phosphorus-containing ZSM-5 molecular sieve sample, denoted as RNB-3.

[0085] Example 11

[0086] 10.35g of hypophosphoric acid was dissolved in 145g of deionized water at 25℃. Ammonia was added to adjust the pH of the solution to be within the range of 5-9. The solution was stirred for 0.5h to obtain a phosphorus-containing aqueous solution. 100g of HZSM-5 molecular sieve (nSiO2 / nAl2O3=30) was added and modified by impregnation. After impregnation at 25℃ for 0.5h, the solution was transferred to an oven for drying at 120℃ for 12h. The solution was then calcined in an air atmosphere in a muffle furnace at 550℃ for 2h. The resulting phosphorus-containing ZSM-5 molecular sieve sample was designated JCB-4.

[0087] Comparative Example 5

[0088] 20.85g of diammonium hydrogen phosphate was dissolved in 145g of deionized water at 25℃ and stirred for 0.5h to obtain a phosphorus-containing aqueous solution. 100g of HZSM-5 molecular sieve (nSiO2 / nAl2O3=30) was added and modified by impregnation. After impregnation at 25℃ for 0.5h, the solution was transferred to an oven and dried at 120℃ for 12h. Then, it was calcined in an air atmosphere in a muffle furnace at 550℃ for 2h. The resulting phosphorus-containing ZSM-5 molecular sieve control sample was designated as DPB-5.

[0089] Comparative Example 6

[0090] 18.15 g of phosphoric acid solution (85 wt%) was dissolved in 145 g of deionized water at 25 °C and stirred for 0.5 h to obtain a phosphorus-containing aqueous solution. 100 g of HZSM-5 molecular sieve (nSiO2 / nAl2O3 = 30) was added, and the solution was modified by impregnation. After impregnation at 25 °C for 0.5 h, the solution was transferred to an oven and dried at 120 °C for 12 h. The solution was then calcined in an air atmosphere in a muffle furnace at 550 °C for 2 h. The resulting phosphorus-containing ZSM-5 molecular sieve control sample was designated as DPB-6.

[0091] The relative crystallinity and crystallinity retention of samples JNB-3, RNB-3, JCB-4, and control samples DPB-5 and DPB-6 before and after hydrothermal aging treatment at 800℃ and 100% water vapor for 17 hours are shown in Table 7.

[0092] Sample JNB-3 and control sample DPB-527 The Al MAS-NMR spectrum is shown below. Figure 5 In the figure, the characteristic peak at a chemical shift of 39 ppm is attributed to the twisted four-coordinate framework aluminum formed after phosphorus and aluminum combine, i.e., the framework aluminum stabilized by phosphorus species. Samples RNB-3 and JCB-4... 27 Al MAS-NMR spectral characteristics and sample JNB-3 Figure 5 They share the same characteristics.

[0093] The full width at half maximum (FWHM) data of the characteristic peaks at 39 ppm for samples JNB-3, RNB-3, JCB-4, and control samples DPB-5 and DPB-6 are shown in Table 8.

[0094] The XPS (P2p Scan) spectrum of sample JNB-3 is shown below. Figure 6 In the figure, the peaks of 134.3 eV and 134.6 eV represent the electron binding energies of phosphorus in the surface phosphorus species of sample JNB-3 after drying at 120℃ during the preparation process, and the electron binding energies of phosphorus in the surface phosphorus species of sample JNB-3 after hydrothermal aging at 800℃ and 100% water vapor for 17 h, respectively. The XPS (P2p Scan) spectral characteristics of the electron binding energies of phosphorus in the surface phosphorus species of samples RNB-3 and JCB-4 after hydrothermal aging at 800℃ and 100% water vapor for 17 h are compared with those of sample JNB-3. Figure 6 They share the same characteristics.

[0095] Table 7

[0096]

[0097] Table 8

[0098] JNB-3 19 RNB-3 20 JCB-4 19 DPB-5 7 DPB-6 9

[0099] Test Example 3

[0100] Samples JNB-3 and RNB-3, and control samples DPB-5 and DPB-6 were evaluated for n-tetradecane cracking. The microreactor evaluation conditions were: molecular sieve loading 2g, feedstock n-tetradecane, feed rate 1.56g, reaction temperature 550℃, and regeneration temperature 600℃. The evaluation data are shown in Table 9.

[0101] Table 9

[0102] Material balance / m% dry air 4.07 3.94 4.05 3.41 3.28 Liquefied gas 51.65 50.03 51.12 40.94 39.39 gasoline 24.02 23.89 23.98 23.19 23.47 diesel fuel 20.01 21.94 20.14 32.22 33.21 m% of main products in cracked gas ethylene 3.54 3.48 3.53 2.72 2.55 propylene 17.84 17.57 17.77 14.97 15.00 Total butene 17.19 16.58 17.04 14.08 14.10 Conversion rate / m% 80.05 78.46 79.87 67.01 64.51

[0103] Example 12

[0104] 1.36 g of ammonium hypophosphate was dissolved in 145 g of deionized water at 25 °C and 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 the solution was modified by impregnation. After impregnation at 25 °C for 0.5 h, the solution was transferred to an oven and dried at 120 °C for 12 h. The solution was then calcined in an air atmosphere in a muffle furnace at 550 °C for 2 h. The resulting phosphorus-containing ZSM-5 molecular sieve sample was designated JNB-5.

[0105] Comparative Example 7

[0106] 2.16 g of diammonium hydrogen phosphate was dissolved in 145 g of deionized water at 25 °C and 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 the solution was modified by impregnation. After impregnation at 25 °C for 0.5 h, the solution was transferred to an oven and dried at 120 °C for 12 h. The solution was then calcined in an air atmosphere in a muffle furnace at 550 °C for 2 h. The resulting phosphorus-containing ZSM-5 molecular sieve control sample was designated as DPB-7.

[0107] Example 13

[0108] 0.91g of ammonium hypophosphate was dissolved in 145g of deionized water at 25℃ and 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℃ for 0.5h, the solution was transferred to an oven and dried at 120℃ for 12h. The solution was then calcined in an air atmosphere in a muffle furnace at 550℃ for 2h. The resulting phosphorus-containing ZSM-5 molecular sieve sample was designated JNB-6.

[0109] Comparative Example 8

[0110] 1.45g of diammonium hydrogen phosphate was dissolved in 145g of deionized water at 25℃ and stirred for 0.5h to obtain a phosphorus-containing aqueous solution. 100g of HZSM-5 molecular sieve (nSiO2 / nAl2O3=150) was added and modified by impregnation. After impregnation at 25℃ for 0.5h, the solution was transferred to an oven and dried at 120℃ for 12h. Then, it was calcined in an air atmosphere in a muffle furnace at 550℃ for 2h. The resulting phosphorus-containing ZSM-5 molecular sieve control sample was designated as DPB-8.

[0111] The relative crystallinity and crystal retention of XRD of sample JNB-5, control sample DPB-7, JNB-6, and control sample DPB-8 before and after hydrothermal aging treatment at 800℃ and 100% water vapor for 17h are shown in Table 10. 27 Table 11 shows the full width at half maximum (FWHM) data of the characteristic peak at 39 ppm in the Al MAS-NMR spectrum.

[0112] The electron binding energies of phosphorus in the surface phosphorus species of sample JNB-5 after drying at 120℃ and after hydrothermal aging at 800℃ and 100% water vapor for 17h are 134.2eV and 134.7eV, respectively.

[0113] The electron binding energies of phosphorus in the surface phosphorus species of sample DPB-7 after drying and hydrothermal aging were 134.8 eV and 34.9 eV, respectively.

[0114] The electron binding energies of phosphorus in the surface phosphorus species of sample JNB-6 after drying at 120℃ and after hydrothermal aging at 800℃ and 100% water vapor for 17h are 134.3eV and 134.6eV, respectively.

[0115] The electron binding energies of phosphorus in the surface phosphorus species of sample DPB-8 after drying and hydrothermal aging were 134.8 eV and 135.0 eV, respectively.

[0116] Table 10

[0117]

[0118] Table 11

[0119] JNB-5 19 DPB-7 18 JNB-6 9 DPB-8 8

[0120] Test Example 4

[0121] Samples JNB-5 and JNB-6, and control samples DPB-7 and DPB-8 were evaluated for n-tetradecane cracking. The microreactor evaluation conditions were: molecular sieve loading 2g, feedstock n-tetradecane, feed rate 1.56g, reaction temperature 550℃, and regeneration temperature 600℃. The evaluation data are shown in Table 12.

[0122] Table 12

[0123] Material balance / m% dry air 3.87 3.65 3.21 3.14 Liquefied gas 18.65 17.03 17.12 11.94 gasoline 26.02 27.89 22.47 21.93 diesel fuel 51.56 53.94 58.14 64.22 m% of main products in cracked gas ethylene 1.43 1.42 1.24 2.72 propylene 9.36 8.64 8.37 6.94 Total butene 7.07 5.94 6.29 4.65 Conversion rate / m% 45.22 42.61 40.17 35.91

Claims

1. A catalytic cracking method, using phosphorus-modified ZSM-5 molecular sieve as a catalyst, characterized in that, The phosphorus-modified ZSM-5 molecular sieve, after hydrothermal aging at 800℃ and 100% steam for 17 hours, has a phosphorus binding energy of 134.6–134.7 eV in the phosphorus species on the surface of the molecular sieve. The phosphorus-modified ZSM-5 molecular sieve is obtained by contacting and impregnating HZSM-5 molecular sieve with an aqueous solution of a phosphorus-containing compound with a phosphorus valence of +1, followed by drying and calcination. Alternatively, the phosphorus-modified ZSM-5 molecular sieve is obtained by heating and melting a mixture of HZSM-5 molecular sieve and a solid phosphorus-containing compound with a phosphorus valence of +1, cooling it to room temperature, and then calcining it.

2. The catalytic cracking method according to claim 1, characterized in that, The phosphorus-modified ZSM-5 molecular sieve was subjected to hydrothermal aging at 800℃ and 100% steam for 17 hours, and its properties were measured. 27 In the Al MAS-NMR spectrum, the full width at half maximum (FWHM) of the resonance signal peak with a chemical shift of 39±3 ppm is 10–25 ppm.

3. The catalytic cracking method according to claim 1, characterized in that, The phosphorus-modified ZSM-5 molecular sieve was subjected to hydrothermal aging at 800℃ and 100% steam for 17 hours, and its properties were measured. 27 In the Al MAS-NMR spectrum, the full width at half maximum (FWHM) of the resonance signal peak with a chemical shift of 39±3 ppm is 15–25 ppm.

4. The catalytic cracking method according to claim 1, characterized in that, The phosphorus-modified ZSM-5 molecular sieve has a ratio of 0.01 to 5 when both phosphorus and aluminum are measured in molar amounts.

5. The catalytic cracking method according to claim 4, characterized in that, The phosphorus-modified ZSM-5 molecular sieve has a ratio of 0.1 to 3 when both phosphorus and aluminum are measured in molar amounts.

6. The catalytic cracking method according to claim 1, characterized in that, The impregnation is carried out at a water-to-sieve weight ratio of 0.5 to 2 for 0.5 to 10 hours at room temperature; the drying is carried out in an air atmosphere at 100 to 120°C for 2 to 24 hours; the calcination is carried out at 550°C for 0.5 to 12 hours.

7. The catalytic cracking method according to claim 1, characterized in that, The heating and melting treatment is carried out at a temperature higher than the melting point of the solid phosphorus-containing compound but lower than the temperature at which the solid phosphorus-containing compound decomposes or dehydrates, and the treatment time is 2 to 72 hours.

8. The catalytic cracking method according to claim 1, characterized in that, The phosphorus-containing compounds with a +1 oxidation state are selected from one or more hypophosphite and hypophosphite.

9. The catalytic cracking method according to claim 1, characterized in that, The aqueous solution of the phosphorus-containing compound with a phosphorus oxidation state of +1 is obtained by adjusting the pH of the hypophosphorous acid solution to 5-9 with ammonia.

10. The catalytic cracking method according to claim 1, characterized in that, The molar ratio of the HZSM-5 molecular sieve to the phosphorus-containing compound with a +1 valence 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.

11. The catalytic cracking method according to claim 1, characterized in that, The molar ratio of the HZSM-5 molecular sieve to the phosphorus-containing compound with a +1 valence is (0.5~1.5):1, wherein the HZSM-5 molecular sieve is calculated as aluminum and the phosphorus-containing compound is calculated as phosphorus.

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