Preparation method and application of phosphorus-modified ZSM-5 molecular sieve

Abstract

The present invention provides a method for preparing a phosphorus-modified ZSM-5 molecular sieve, comprising the following steps: first, a phosphorus source and a template are mixed to obtain a mixed solution A; a mixed solution B obtained by mixing a silicon source, an aluminum source, an alkali source, a seed crystal and water again is heated and kept at a constant temperature; finally, after the mixed solution A and the mixed solution B after the constant temperature are reacted, the phosphorus-modified ZSM-5 molecular sieve is obtained by roasting. The present invention introduces a phosphorus source during the reaction, and the introduced phosphorus forms a chemical bond with the skeleton aluminum atom to improve the water-resistant thermal stability of the ZSM-5 molecular sieve. The method of the present invention can avoid the miscellaneous crystals generated when directly synthesizing the phosphorus-modified ZSM-5 molecular sieve, and does not use alkali metals, simplifies the preparation steps, reduces production costs, and reduces environmental pollution. The content of phosphorus pentoxide in the ZSM-5 molecular sieve prepared by the present invention is 0.1% to 10%, and the prepared phosphorus-modified molecular sieve is an MFI structure without miscellaneous crystals.

Description

Technical Field

[0001] The invention belongs to the technical field of ZSM-5 molecular sieve modification, and relates to a preparation method and application of a phosphorus-modified ZSM-5 molecular sieve. Background Art

[0002] ZSM-5 molecular sieve is a medium-pore molecular sieve with MFI structure (USP 3702886). It has a unique pore structure, adjustable acidity and excellent shape selectivity. In 1983, ZSM-5 molecular sieve began to be used in the catalytic cracking (FCC) process. Under the harsh high-temperature hydrothermal conditions of FCC, ZSM-5 molecular sieve is prone to framework dealumination, resulting in irreversible deactivation of the molecular sieve.

[0003] Molecular sieve phosphating is a key technology to improve the hydrothermal stability of ZSM-5 molecular sieve. After phosphating, the framework aluminum of ZSM-5 molecular sieve can be stabilized under harsh hydrothermal conditions. The most widely used method is to first exchange the sodium type molecular sieve with ammonium ions to obtain ZSM-5 molecular sieve, then impregnate it with phosphoric acid or phosphate solution, and then dry and calcine it to obtain P-HZSM-5.

[0004] However, the process is complicated and the exchange process produces a large amount of wastewater, which seriously affects the environment. At the same time, during the calcination of the molecular sieve, the phosphorus species will self-aggregate to form different aggregate forms, reducing the utilization efficiency of phosphorus and blocking the molecular sieve pores. Moreover, different phosphorus compounds, such as trimethyl phosphate and triphenylphosphine, will also have similar problems.

[0005] Therefore, how to develop a preparation process for direct phosphorus-modified ZSM-5 molecular sieve without the need for ammonium exchange and solve the above-mentioned technical problems existing in the existing preparation process of phosphorus-modified ZSM-5 molecular sieve is of great significance and is also one of the focuses of widespread attention of many forward-looking front-line researchers in the industry. Summary of the invention

[0006] In view of this, the technical problem to be solved by the present invention is to provide a preparation method and application of phosphorus-modified ZSM-5 molecular sieve. The present invention introduces a phosphorus source during the reaction process, and the introduced phosphorus forms a chemical bond with the framework aluminum atom, thereby improving the hydrothermal stability of the ZSM-5 molecular sieve. The method of the present invention can avoid the miscellaneous crystals generated when the phosphorus-modified ZSM-5 molecular sieve is directly synthesized, and at the same time simplifies the preparation steps of the phosphorus-modified ZSM-5 molecular sieve, has a simple process, mild conditions, strong controllability, and is more suitable for the promotion and application of industrial production.

[0007] The present invention provides a method for preparing a phosphorus-modified ZSM-5 molecular sieve, comprising the following steps:

[0008] 1) mixing a phosphorus source and a template to obtain a mixed solution A;

[0009] The mixed solution B obtained by mixing the silicon source, the aluminum source, the alkali source, the seed crystal and the water again is heated and kept at a constant temperature;

[0010] 2) After reacting the mixed solution A and the mixed solution B after constant temperature, calcining to obtain the phosphorus-modified ZSM-5 molecular sieve.

[0011] Preferably, the phosphorus source is one or more of phosphorus tribromide, phosphorus oxybromide, phosphorus oxychloride and phosphorus trichloride;

[0012] The template is an anhydrous template;

[0013] The molar ratio of the phosphorus source to the template is 1:(1-10).

[0014] Preferably, the water content in the template is less than 100 ppm;

[0015] The template agent is one or more of triethylamine, ethylenediamine, diethylamine and n-butylamine;

[0016] The silicon source is one or more of silica sol, white carbon black and silica gel.

[0017] Preferably, the aluminum source is one or more of aluminum sulfate, aluminum chloride, aluminum hydroxide and pseudo-boehmite;

[0018] The alkali source is urea and / or ammonia water;

[0019] The seed crystal is a ZSM-5 molecular sieve seed crystal.

[0020] Preferably, the molar ratio of the silicon source to the aluminum source, calculated as SiO2 and Al2O3, is (20-1000):1;

[0021] The aluminum source and the alkali source, calculated as Al2O3 and N, have a molar ratio of 1:(2-100);

[0022] In the mixed solution B, the mass content of the seed crystals is 0.1% to 5% based on the total dry mass;

[0023] The aluminum source and water, calculated as Al2O3 and H2O, have a molar ratio of 1:(200-20000).

[0024] Preferably, the constant temperature is 100-180°C;

[0025] The constant temperature time is 0.5 to 48 hours;

[0026] The molar ratio of the mixed solution A and the mixed solution B after constant temperature is (0.1-10):1 in terms of P2O5 and Al2O3.

[0027] Preferably, the reaction temperature is 150-200°C;

[0028] The reaction time is 12 to 96 hours;

[0029] The reaction may further include washing and / or drying steps.

[0030] Preferably, the calcination temperature is 500-700°C;

[0031] The calcination time is 1 to 6 hours;

[0032] The mass content of phosphorus pentoxide in the phosphorus-modified ZSM-5 molecular sieve is 0.1% to 10%.

[0033] Preferably, in the phosphorus-modified ZSM-5 molecular sieve, phosphorus is chemically bonded to the framework aluminum atoms;

[0034] The phosphorus-modified ZSM-5 molecular sieve has an MFI structure;

[0035] The phosphorus-modified ZSM-5 molecular sieve has no impurity crystals.

[0036] The present invention also provides the use of the phosphorus-modified ZSM-5 molecular sieve prepared by the preparation method described in any one of the above technical solutions in improving the hydrothermal stability of the ZSM-5 molecular sieve.

[0037] The present invention provides a method for preparing a phosphorus-modified ZSM-5 molecular sieve, comprising the following steps: firstly, a phosphorus source and a template are mixed to obtain a mixed solution A; a silicon source, an aluminum source, an alkali source, a seed crystal and water are mixed again to obtain a mixed solution B, which is heated and kept at a constant temperature; finally, the mixed solution A and the mixed solution B after being kept at a constant temperature are reacted, and then roasted to obtain the phosphorus-modified ZSM-5 molecular sieve. Compared with the prior art, the present invention creatively designs a method for preparing a phosphorus-modified ZSM-5 molecular sieve with specific steps and processes, introduces a phosphorus source during the reaction, and the introduced phosphorus forms a chemical bond with the framework aluminum atom to improve the water and heat stability of the ZSM-5 molecular sieve. The method of the present invention can avoid the generation of impurities when directly synthesizing the phosphorus-modified ZSM-5 molecular sieve, and at the same time simplifies the preparation steps of the phosphorus-modified ZSM-5 molecular sieve.

[0038] The preparation method of phosphorus-modified ZSM-5 molecular sieve disclosed in the present invention, first silicon source, aluminum source, alkali source, seed crystal are uniformly mixed in water, then transferred to a reactor, temperature reaction, and phosphorus source is added during the reaction process, continuous crystallization, and finally phosphorus-modified ZSM-5 molecular sieve is obtained. The method introduces a phosphorus source during the reaction process, and the introduced phosphorus forms a chemical bond with the skeleton aluminum atom, thereby improving the water-resistant thermal stability of the ZSM-5 molecular sieve. Introducing a phosphorus source during the synthesis process can avoid the generation of miscellaneous crystals, and alkali metals are not used at the same time, simplifying the preparation steps of phosphorus-modified ZSM-5 molecular sieves.

[0039] The mass content of phosphorus pentoxide in the ZSM-5 molecular sieve prepared by the invention is 0.1% to 10%, and the prepared phosphorus-modified molecular sieve has an MFI structure and is free of impurity crystals; a phosphorus source is introduced during the reaction process, and the introduced phosphorus forms a chemical bond with the framework aluminum atom, thereby improving the hydrothermal stability of the ZSM-5 molecular sieve; and no alkali metal is used during the synthesis process, thereby simplifying the preparation steps of the phosphorus-modified ZSM-5 molecular sieve, reducing the production cost, and reducing environmental pollution. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] Figure 1 The XRD spectra of the molecular sieves prepared in the examples and comparative examples of the present invention are shown in FIG. DETAILED DESCRIPTION

[0041] In order to further understand the present invention, preferred embodiments of the present invention are described below in conjunction with examples, but it should be understood that these descriptions are only for further illustrating the features and advantages of the present invention, rather than limiting the claims of the invention.

[0042] All raw materials of the present invention have no particular limitation on their sources, and can be purchased from the market or prepared according to conventional methods known to those skilled in the art.

[0043] There is no particular restriction on the purity of all raw materials in the present invention. The present invention preferably uses analytically pure materials or materials with conventional purity requirements in the field of ZSM-5 molecular sieve preparation.

[0044] All raw materials and process steps of the present invention, their brands or abbreviations are conventional brands or abbreviations in the art, and each brand or abbreviation is clear and definite in the field of its related use. Those skilled in the art can purchase them from the market or prepare them by conventional methods, or implement them with corresponding equipment according to the brands, abbreviations and corresponding uses.

[0045] The present invention provides a method for preparing a phosphorus-modified ZSM-5 molecular sieve, comprising the following steps:

[0046] 1) mixing a phosphorus source and a template to obtain a mixed solution A;

[0047] The mixed solution B obtained by mixing the silicon source, the aluminum source, the alkali source, the seed crystal and the water again is heated and kept at a constant temperature;

[0048] 2) After reacting the mixed solution A and the mixed solution B after constant temperature, calcining to obtain the phosphorus-modified ZSM-5 molecular sieve.

[0049] The present invention firstly mixes a phosphorus source and a template agent to obtain a mixed solution A;

[0050] The mixed solution B obtained by mixing the silicon source, the aluminum source, the alkali source, the seed crystal and the water again is heated and kept at a constant temperature.

[0051] In the present invention, the phosphorus source is preferably one or more of phosphorus tribromide, phosphorus oxybromide, phosphorus oxychloride and phosphorus trichloride, more preferably phosphorus tribromide, phosphorus oxychloride, phosphorus trichloride or phosphorus trichloride.

[0052] In the present invention, the template is preferably an anhydrous template. Specifically, the water content in the template is preferably less than 100 ppm, more preferably less than or equal to 80 ppm, and more preferably less than or equal to 60 ppm.

[0053] In the present invention, the molar ratio of the phosphorus source to the template is preferably 1:(1-10), more preferably 1:(3-8), and more preferably 1:(5-6).

[0054] In the present invention, the template is preferably one or more of triethylamine, ethylenediamine, diethylamine and n-butylamine, more preferably triethylamine, ethylenediamine, diethylamine or n-butylamine.

[0055] In the present invention, the silicon source is preferably one or more of silica sol, white carbon black and silica gel, more preferably silica sol, white carbon black or silica gel.

[0056] In the present invention, the aluminum source is preferably one or more of aluminum sulfate, aluminum chloride, aluminum hydroxide and pseudo-boehmite, more preferably aluminum sulfate, aluminum chloride, aluminum hydroxide or pseudo-boehmite.

[0057] In the present invention, the alkali source is preferably urea and / or aqueous ammonia, more preferably urea or aqueous ammonia.

[0058] In the present invention, the seed crystal is preferably a ZSM-5 molecular sieve seed crystal.

[0059] In the present invention, the molar ratio of the silicon source to the aluminum source, calculated as SiO2 and Al2O3, is preferably (20-1000):1, more preferably (50-800):1, and more preferably (100-600):1.

[0060] In the present invention, the molar ratio of the aluminum source to the alkali source, calculated as Al2O3 and N, is preferably 1:(2-100), more preferably 1:(10-80), and more preferably 1:(30-60).

[0061] In the present invention, in the mixed solution B, the mass content of the seed crystals is preferably 0.1% to 5%, more preferably 0.5% to 4%, and more preferably 1% to 3%, based on the total dry mass.

[0062] In the present invention, the molar ratio of the aluminum source to water, calculated as Al2O3 and H2O, is preferably 1:(200-20000), more preferably (500-15000), more preferably (1000-10000), and more preferably (3000-8000).

[0063] In the present invention, the constant temperature is preferably 100-180°C, more preferably 110-170°C, more preferably 120-160°C, and more preferably 130-150°C.

[0064] In the present invention, the constant temperature time is preferably 0.5 to 48 hours, more preferably 1 to 40 hours, more preferably 5 to 35 hours, and more preferably 10 to 30 hours.

[0065] In the present invention, the mixed solution A and the mixed solution B after constant temperature are reacted, and then calcined to obtain the phosphorus-modified ZSM-5 molecular sieve.

[0066] In the present invention, the molar ratio of the mixed solution A and the mixed solution B after constant temperature, calculated as P2O5 and Al2O3, is preferably (0.1-10):1, more preferably (0.5-8):1, and more preferably (1-5):1.

[0067] In the present invention, the reaction temperature is preferably 150-200°C, more preferably 160-190°C, and even more preferably 170-180°C.

[0068] In the present invention, the reaction time is preferably 12 to 96 hours, more preferably 24 to 84 hours, and more preferably 36 to 72 hours.

[0069] In the present invention, the reaction preferably includes a washing and / or drying step. Specifically, the washing is preferably water washing.

[0070] In the present invention, the calcination temperature is preferably 500-700°C, more preferably 530-680°C, more preferably 550-650°C, and more preferably 570-630°C.

[0071] In the present invention, the calcination time is preferably 1 to 6 hours, more preferably 2 to 5 hours, and more preferably 3 to 4 hours.

[0072] In the present invention, the mass content of phosphorus pentoxide in the phosphorus-modified ZSM-5 molecular sieve is preferably 0.5% to 8%, more preferably 1% to 5%.

[0073] In the present invention, in the phosphorus-modified ZSM-5 molecular sieve, phosphorus and framework aluminum atoms are preferably chemically bonded.

[0074] In the present invention, the phosphorus-modified ZSM-5 molecular sieve is preferably of MFI structure and free of impurity crystals.

[0075] The present invention also provides the use of the phosphorus-modified ZSM-5 molecular sieve prepared by the preparation method described in any one of the above technical solutions in improving the hydrothermal stability of the ZSM-5 molecular sieve.

[0076] The present invention is to complete and refine the overall technical solution, better ensure the composition and structure of the phosphorus-modified ZSM-5 molecular sieve, and further improve the hydrothermal stability of the phosphorus-modified ZSM-5 molecular sieve. The preparation method of the phosphorus-modified ZSM-5 molecular sieve and its application can specifically include the following contents:

[0077] A phosphorus-modified ZSM-5 molecular sieve and a preparation method thereof, wherein a phosphorus source is introduced during the reaction process, and the introduced phosphorus forms a chemical bond with the framework aluminum atoms to improve the hydrothermal stability of the ZSM-5 molecular sieve. The method comprises the following steps:

[0078] a. Add the phosphorus source to the template (R) in a certain proportion, mix well, and transfer to container A;

[0079] b. The silicon source, aluminum source, alkali source, seed crystal and water are mixed uniformly in a certain proportion, and transferred to the reactor B for heating and constant temperature for a certain period of time;

[0080] c. Add the solution in container A to reactor B and react under certain conditions. After washing, drying and calcining, the product of the present invention is obtained.

[0081] Specifically, the phosphorus source (P2O5) in step a is one or a mixture of phosphorus tribromide, phosphorus oxybromide, phosphorus oxychloride, and phosphorus trichloride.

[0082] Specifically, the template (R) in step a is one or a mixture of triethylamine, ethylenediamine, diethylamine, and n-butylamine, and the template is an anhydrous template with a water content of less than 100 ppm.

[0083] Specifically, the ratio in step a is: P2O5:R=1:1-10.

[0084] Specifically, the silicon source (SiO2) in step b is one or a mixture of silica sol, white carbon black, and silica gel; the aluminum source (Al2O3) is one or a mixture of aluminum sulfate, aluminum chloride, aluminum hydroxide, and pseudo-boehmite; the alkali source (N) is one or a mixture of urea and ammonia water; and the seed is a ZSM-5 molecular sieve seed.

[0085] Specifically, the composition (molar ratio) of the components in step b is: SiO2:Al2O3:N:H2O=20~1000:1:2~100:200~20000.

[0086] Specifically, the amount of seed crystal added is 0.1-5% of the total dry basis mass.

[0087] Specifically, the reactor B in step b is heated to 100-180° C. and kept at a constant temperature for 0.5-48 hours. The reactor B is a high-pressure reactor with stirring.

[0088] Specifically, in step c, the solution in container A is added to reactor B, and the adding ratio is: P2O5:Al2O3=0.1~10:1.

[0089] Specifically, the reaction conditions in step c are: 150-200° C., constant temperature for 12-96 hours. The product slurry in step c is washed, dried, and roasted to obtain the product of the present invention.

[0090] Specifically, the phosphorus pentoxide content in the ZSM-5 molecular sieve prepared by the method is 0.1% to 10%.

[0091] Specifically, the method introduces a phosphorus source during the synthesis of the molecular sieve, and the introduced phosphorus forms a chemical bond with the framework aluminum atoms to improve the hydrothermal stability of the ZSM-5 molecular sieve.

[0092] Specifically, the method introduces a phosphorus source during the synthesis of the molecular sieve, which can avoid the generation of impurity crystals. At the same time, no alkali metal is used, which simplifies the preparation steps of the phosphorus-modified ZSM-5 molecular sieve.

[0093] Furthermore, the phosphorus source (P2O5) in step a is one or a mixture of phosphorus tribromide, phosphorus oxybromide, phosphorus oxychloride, phosphorus trichloride. In a preferred embodiment, the phosphorus source (P2O5) is one or a mixture of phosphorus oxybromide and phosphorus oxychloride.

[0094] Further, the template (R) in step a is one or a mixture of triethylamine, ethylenediamine, diethylamine, and n-butylamine, and the template is an anhydrous template with a water content of less than 100 ppm. In a preferred embodiment, the template (R) is one or a mixture of triethylamine and n-butylamine, and the water content of the template is less than 50 ppm.

[0095] Furthermore, the ratio in step a is: P2O5:R=1:1~10, and the preferred ratio is: P2O5:R=1:2~5.

[0096] Furthermore, the silicon source (SiO2) in step b is one or a mixture of silica sol, white carbon black, and silica gel, preferably one or a mixture of silica sol and silica gel, and more preferably silica sol; the aluminum source (Al2O3) is one or a mixture of aluminum sulfate, aluminum chloride, aluminum hydroxide, and pseudo-boehmite, preferably one or a mixture of aluminum sulfate and aluminum chloride, and more preferably aluminum sulfate; the alkali source (N) is one or a mixture of urea and ammonia water; and the seed is a ZSM-5 molecular sieve seed.

[0097] Furthermore, the composition (molar ratio) in step b is: SiO2:Al2O3:N:H2O=20~1000:1:2~100:200~20000, and the preferred molar ratio is: SiO2:Al2O3:N:H2O=20~80:1:2~40:200~2000.

[0098] Furthermore, the amount of seed crystals added in step b is 0.1 to 5% of the total dry basis mass.

[0099] Furthermore, in step b, the reactor B is heated to 100-180°C and kept at the constant temperature for 0.5-48 hours, and the reactor B is a high-pressure reactor with stirring. Preferably, the temperature is raised to 100-150°C and kept at the constant temperature for 12-24 hours.

[0100] Furthermore, in step c, the solution in container A is added to reactor B, and the addition ratio is: P2O5:Al2O3=0.1-10:1. Preferably, the addition ratio is: P2O5:Al2O3=0.1-5:1

[0101] Furthermore, the reaction conditions in step c are: 150-200° C., constant temperature for 12-96 hours.

[0102] Furthermore, the product slurry in step c is washed, dried and calcined to obtain the product of the present invention.

[0103] The above content of the present invention provides a method for preparing a phosphorus-modified ZSM-5 molecular sieve and its application. The present invention creatively designs a method for preparing a phosphorus-modified ZSM-5 molecular sieve with specific steps and processes, introduces a phosphorus source during the reaction, and the introduced phosphorus forms a chemical bond with the framework aluminum atom to improve the hydrothermal stability of the ZSM-5 molecular sieve. The method of the present invention can avoid the generation of impurities when directly synthesizing the phosphorus-modified ZSM-5 molecular sieve, and at the same time simplifies the preparation steps of the phosphorus-modified ZSM-5 molecular sieve.

[0104] The preparation method of phosphorus-modified ZSM-5 molecular sieve disclosed in the present invention, first silicon source, aluminum source, alkali source, seed crystal are uniformly mixed in water, then transferred to a reactor, temperature reaction, and phosphorus source is added during the reaction process, continuous crystallization, and finally phosphorus-modified ZSM-5 molecular sieve is obtained. The method introduces a phosphorus source during the reaction process, and the introduced phosphorus forms a chemical bond with the skeleton aluminum atom, thereby improving the water-resistant thermal stability of the ZSM-5 molecular sieve. Introducing a phosphorus source during the synthesis process can avoid the generation of miscellaneous crystals, and alkali metals are not used at the same time, simplifying the preparation steps of phosphorus-modified ZSM-5 molecular sieves.

[0105] The mass content of phosphorus pentoxide in the ZSM-5 molecular sieve prepared by the invention is 0.1% to 10%, and the prepared phosphorus-modified molecular sieve has an MFI structure and is free of impurity crystals; a phosphorus source is introduced during the reaction process, and the introduced phosphorus forms a chemical bond with the framework aluminum atom, thereby improving the hydrothermal stability of the ZSM-5 molecular sieve; and no alkali metal is used during the synthesis process, thereby simplifying the preparation steps of the phosphorus-modified ZSM-5 molecular sieve, reducing the production cost, and reducing environmental pollution.

[0106] In order to further illustrate the present invention, the preparation method of a phosphorus-modified ZSM-5 molecular sieve provided by the present invention and its application are described in detail below in combination with examples. However, it should be understood that these examples are implemented on the premise of the technical solution of the present invention, and detailed implementation methods and specific operating processes are given only to further illustrate the characteristics and advantages of the present invention, rather than to limit the claims of the present invention, and the protection scope of the present invention is not limited to the following examples.

[0107] Embodiments 1 to 4

[0108] See Table 1, which shows the raw materials and proportions for preparing solution A.

[0109] Table 1

[0110] Solution A Phosphorus source Template(R) Solution composition (molar ratio) A-1 Phosphorus oxybromide Triethylamine <![CDATA[P2O5:R=1:5]]> A-2 Phosphorus oxychloride n-Butylamine <![CDATA[P2O5:R=1:2]]>

[0111] According to the raw materials and proportions given in Table 1, the phosphorus source was added to the template, mixed evenly, and a solution A was prepared, which was recorded as A-1&2.

[0112] See Table 2, which shows the raw materials, proportions and crystallization conditions for the examples and comparative examples of the present invention.

[0113] Table 2

[0114]

[0115] According to the raw materials and proportions given in Table 2, aluminum sulfate, silica sol, urea or ammonia water are added to deionized water in sequence, stirred rapidly, and finally seed crystals (3% of the dry mass of the slurry) are added, mixed evenly, and a gel is obtained. The gel is transferred to an autoclave B, the autoclave is sealed, and the temperature is increased and stirred for crystallization (I). After a certain period of constant temperature, solution A is added to the reactor B and crystallization is continued (II). After the reaction is completed, the product is washed with water, dried, and roasted (600°C, roasted for 3 hours) to obtain the embodiments of the present invention, which are recorded as S-1 to S-4.

[0116] Comparative Examples 1 & 2

[0117] According to the raw materials and proportions given in Table 2, aluminum sulfate, silica sol, urea or ammonia water are added to deionized water in sequence, stirred rapidly, and finally seed crystals (3% of the dry mass of the slurry) are added and mixed evenly to obtain a gel. The gel is transferred to an autoclave B, and then solution A is added to the reactor B, stirred evenly, and the temperature is raised for crystallization (II). After the reaction is completed, the product is washed with water, dried, and calcined (600°C for 3 hours) to obtain comparative examples 1 and 2, which are recorded as: D-1&2.

[0118] The molecular sieves prepared in the examples of the present invention and the comparative examples were tested.

[0119] Hydrothermal aging conditions: 1. Temperature: 800°C; 2. Water vapor: 100%; 3. Mass space velocity: 0.1h -1 ; 4. Aging time: 20h.

[0120] See Table 3, which shows the physical properties and hydrothermal resistance of the samples of the embodiments of the present invention, comparative examples, and reference samples (seed crystals).

[0121] Table 3

[0122] Example Crystal form Crystallinity, % <![CDATA[P2O5 content (wt, %)]]> Aging crystallinity, % Crystallinity retention rate, % S-1 MFI 98.2 5.2 95.4 97.1 S-2 MFI 99.4 8.6 97.1 97.7 S-3 MFI 97.3 5.7 94.3 96.9 S-4 MFI 98.9 7.9 96.3 97.4 D-1 Amorphous 32.2 4.7 11.2 34.8 D-2 Amorphous 37.8 8.1 13.5 35.7 ZSM-5 Seed MFI 100 5.5 76.3 76.3

[0123] PS: Crystallinity retention rate = crystallinity after aging / crystallization before aging*100%.

[0124] The molecular sieves prepared in the examples of the present invention and the comparative examples were characterized.

[0125] See also Figure 1 , Figure 1 The XRD spectra of the molecular sieves prepared in the examples and comparative examples of the present invention are shown in FIG.

[0126] Depend on Figure 1 It can be seen that the samples of the examples all have MFI structure, no impurity crystals, and the phosphorus pentoxide content is in the range of 5.2-8.6%. The comparative example did not undergo the crystallization (I) process, and the obtained product was mainly an amorphous phase with a slight MFI structure.

[0127] After hydrothermal aging, the crystallinity retention rate of the example samples is higher than 96.9%, while the crystallinity retention rate of the conventional phosphorus-modified ZSM-5 molecular sieve seeds is only 76.3% after hydrothermal aging, indicating that the example samples have higher hydrothermal stability.

[0128] The above is a detailed introduction to the preparation method and application of a phosphorus-modified ZSM-5 molecular sieve provided by the present invention. Specific examples are used herein to illustrate the principles and implementation methods of the present invention. The description of the above embodiments is only used to help understand the method and core ideas of the present invention, including the best mode, and also enables any technician in the field to practice the present invention, including the manufacture and use of any device or system, and the implementation of any combined method. It should be pointed out that for ordinary technicians in this technical field, without departing from the principles of the present invention, the present invention can also be improved and modified in a number of ways, and these improvements and modifications also fall within the scope of protection of the claims of the present invention. The scope of patent protection of the present invention is defined by the claims and may include other embodiments that can be thought of by those skilled in the art. If these other embodiments have structural elements that are not different from the textual expression of the claims, or if they include equivalent structural elements that are not substantially different from the textual expression of the claims, then these other embodiments should also be included in the scope of the claims.

Claims

1. A method for preparing a phosphorus-modified ZSM-5 molecular sieve, characterized in that: The following steps are involved: 1) mixing a phosphorus source and a template to obtain a mixed solution A; The mixed solution B obtained by mixing the silicon source, the aluminum source, the alkali source, the seed crystal and the water again is heated and kept at a constant temperature; 2) After reacting the mixed solution A and the mixed solution B after constant temperature, calcining to obtain the phosphorus-modified ZSM-5 molecular sieve.

2. The preparation method according to claim 1, characterized in that: The phosphorus source is one or more of phosphorus tribromide, phosphorus oxybromide, phosphorus oxychloride and phosphorus trichloride; The template is an anhydrous template; The molar ratio of the phosphorus source to the template is 1:(1-10).

3. The preparation method according to claim 1, characterized in that: The water content in the template is less than 100 ppm; The template agent is one or more of triethylamine, ethylenediamine, diethylamine and n-butylamine; The silicon source is one or more of silica sol, white carbon black and silica gel.

4. The preparation method according to claim 1, characterized in that: The aluminum source is one or more of aluminum sulfate, aluminum chloride, aluminum hydroxide and pseudo-boehmite; The alkali source is urea and / or ammonia water; The seed crystal is a ZSM-5 molecular sieve seed crystal.

5. The preparation method according to claim 1, characterized in that: The silicon source and the aluminum source, calculated as SiO2 and Al2O3, have a molar ratio of (20-1000):1; The aluminum source and the alkali source, calculated as Al2O3 and N, have a molar ratio of 1:(2-100); In the mixed solution B, the mass content of the seed crystals is 0.1% to 5% based on the total dry mass; The aluminum source and water, calculated as Al2O3 and H2O, have a molar ratio of 1:(200-20000).

6. The preparation method according to claim 1, characterized in that: The constant temperature is 100-180°C; The constant temperature time is 0.5 to 48 hours; The molar ratio of the mixed solution A and the mixed solution B after constant temperature is (0.1-10):1 in terms of P2O5 and Al2O3.

7. The preparation method according to claim 1, characterized in that: The reaction temperature is 150-200°C; The reaction time is 12 to 96 hours; The reaction may further include washing and / or drying steps.

8. The preparation method according to claim 1, characterized in that: The calcination temperature is 500-700°C; The calcination time is 1 to 6 hours; The mass content of phosphorus pentoxide in the phosphorus-modified ZSM-5 molecular sieve is 0.1% to 10%.

9. The preparation method according to claim 1, characterized in that: In the phosphorus-modified ZSM-5 molecular sieve, phosphorus and framework aluminum atoms are chemically bonded; The phosphorus-modified ZSM-5 molecular sieve has an MFI structure; The phosphorus-modified ZSM-5 molecular sieve has no impurity crystals.

10. Use of the phosphorus-modified ZSM-5 molecular sieve prepared by the preparation method according to any one of claims 1 to 9 in improving the hydrothermal stability of the ZSM-5 molecular sieve.

Images