Modified IM-5 molecular sieve as well as preparation method and application thereof

Abstract

The invention provides a modified IM-5 molecular sieve and a preparation method and application thereof.The modified IM-5 molecular sieve comprises an IM-5 molecular sieve body and modified metal, part of the modified metal is loaded on the outer surface of the IM-5 molecular sieve body and the surfaces of pore channels of the IM-5 molecular sieve body in the form of modified metal oxide, and the modified metal is loaded on the outer surface of the IM-5 molecular sieve body in the form of modified metal oxide. The other part of modified metal enters a framework of the IM-5 molecular sieve in a form of forming chemical bonds; wherein the modified metal comprises one or a combination of more of alkali metal, alkaline earth metal and transition metal. The modified IM-5 molecular sieve provided by the invention has higher modified metal dispersity, more modified metal species enter an IM-5 molecular sieve framework, and when the modified IM-5 molecular sieve is used as a catalyst for catalyzing light hydrocarbon to prepare low-carbon olefin through catalytic cracking, the modified IM-5 molecular sieve has better cracking performance, higher reaction activity and low-carbon olefin selectivity, and the low-carbon olefin yield is high.

Description

Technical Field

[0001] The present invention relates to a modified IM-5 molecular sieve, a preparation method thereof and an application thereof, belonging to the technical field of molecular sieve preparation. Background Art

[0002] The IM-5 molecular sieve is synthesized by using a pyrrolidine-based bisquaternary ammonium salt template agent and has a two-dimensional ten-membered ring pore structure. There are relatively large finite pores in the third dimension. Its pore structure is similar to that of the ZSM-5 molecular sieve. At the same time, the molecular sieve also has a 12-membered ring cage structure, which is different from ZSM-5. Its Bronsted acid and Lewis acid amounts are close to those of the TUN structure molecular sieve, and the ratio of Bronsted acid amount to Lewis acid amount (B / L) is close to that of the ZSM-5 molecular sieve.

[0003] The IM-5 molecular sieve has shown good catalytic performance in many reactions, such as hydrocracking, catalytic cracking, etc. To expand the application of the IM-5 molecular sieve, it generally needs to be modified. However, there are few reports on the modification of the IM-5 molecular sieve, and most of them refer to the modification methods of similar molecular sieves such as ZSM-5 molecular sieve, such as metal oxide modification, non-metal oxide modification, hydrothermal treatment, etc.

[0004] For example, CN 115400790A discloses a multi-component catalyst for the oxidation of propylene to propylene oxide and a preparation method thereof. Specifically, a compound containing an active component is first mixed with ultrapure water to obtain a mixed solution; under the condition of a water bath, a porous molecular sieve carrier is impregnated into the mixed solution, and after impregnation, the porous molecular sieve carrier is taken out and ultrasonically treated at room temperature; the operations of "water bath impregnation - taking out - room temperature ultrasonic treatment" are repeated 3-5 times; the ultrasonically treated sample is dried at room temperature under vacuum and then heat-treated at a high temperature with hydrogen with a volume fraction of 5%-15% to obtain a multi-component catalyst for the oxidation of propylene to propylene oxide; the defects of this technology or the deficiencies relative to the present invention are: there are many steps and the treatment is complex; and there are a large number of active components in the water bath impregnation solution that are not loaded on the molecular sieve carrier, resulting in low utilization rate of the active components, waste of unreacted raw materials, and pollution at the same time.

[0005] CN 114715910A discloses a phosphorus and metal modified ZSM-5 molecular sieve and a preparation method thereof. Specifically, a solution of a phosphorus-containing compound and a solution of a metal compound are mixed or respectively contacted with an HZSM-5 molecular sieve, and after drying treatment, a composite modified ZSM-5 molecular sieve is obtained by hydrothermal calcination treatment under an atmosphere environment of applying external pressure and adding external water; the defects of this technology or the deficiencies relative to the present invention are: this method requires treatment under hydrothermal calcination conditions of high temperature and high pressure, and the silicon-aluminum molecular sieve material is likely to remove some framework Al of the molecular sieve during the hydrothermal treatment process of high temperature and high pressure, resulting in a decrease in the acid amount and activity of the modified molecular sieve.

[0006] CN 114247467 A discloses a dual-metal modified USY zeolite catalyst and its preparation method. First, USY zeolite powder is placed in a mixed impregnation solution of two nitrates and stirred evenly to obtain a mixed slurry. Secondly, after ultrasonic treatment of the above mixed slurry, a first drying treatment is carried out under water bath conditions to obtain a mixed block. Finally, the mixed block is successively subjected to a second drying treatment and a calcination treatment to obtain a dual-metal modified USY zeolite. The defects or deficiencies of this technology compared with the present invention are as follows: Most metal ions are located on the outer surface of the zeolite during the stirring at normal pressure and room temperature in this method, and only a small amount of metal ions can enter the zeolite framework. Moreover, two-step drying treatments are required subsequently, and the preparation steps are cumbersome and the energy consumption is high.

[0007] Therefore, providing a new type of modified IM-5 zeolite and its preparation method and application has become an urgent technical problem to be solved in this field. Summary of the Invention

[0008] In order to solve the above-mentioned disadvantages and deficiencies, an object of the present invention is to provide a modified IM-5 zeolite.

[0009] Another object of the present invention is also to provide a preparation method of the above-mentioned modified IM-5 zeolite.

[0010] Another object of the present invention is also to provide the application of the above-mentioned modified IM-5 zeolite as a catalyst in the catalytic cracking of light hydrocarbons to produce lower olefins.

[0011] In order to achieve the above objects, on the one hand, the present invention provides a modified IM-5 zeolite, wherein the modified IM-5 zeolite includes an IM-5 zeolite and a modified metal. A part of the modified metal is loaded on the outer surface of the IM-5 zeolite and the surface of its pores in the form of a modified metal oxide, and another part of the modified metal enters the framework of the IM-5 zeolite in the form of forming chemical bonds;

[0012] Wherein, the modified metal includes one or a combination of several of alkali metals, alkaline earth metals, transition metals, etc.

[0013] As a specific embodiment of the above-mentioned modified IM-5 zeolite of the present invention, based on the total weight of the IM-5 zeolite being 100%, the content of the modified metal in terms of the modified metal oxide is 0.5%-5.0%, preferably 1.0-3.0%.

[0014] On the other hand, the present invention also provides a preparation method of the above-mentioned modified IM-5 zeolite, wherein the preparation method includes:

[0015] Step (1): Mix the IM-5 molecular sieve powder evenly with an impregnating solution containing a modified metal precursor to obtain a mixed slurry, and stir the mixed slurry under high temperature and high pressure conditions;

[0016] Step (2): Perform ultrasonic treatment on the mixed slurry after the stirring treatment in Step (1);

[0017] Step (3): Evaporate the mixed slurry after the ultrasonic treatment in Step (2) to dryness, and then dry and calcine the dried mixture to obtain the modified IM-5 molecular sieve.

[0018] As a specific embodiment of the above preparation method of the present invention, the modified metal precursor is a water-soluble salt of the modified metal, including one or a combination of several of sulfates, nitrates, and chlorides of the modified metal, etc.

[0019] In the present invention, the alkali metal can be, for example, potassium, etc., the alkaline earth metal can be, for example, magnesium, etc., and the transition metal can be one or a combination of several of nickel, iron, manganese, zinc, lanthanum, etc. Correspondingly, the modified metal precursor can be, for example, one or a combination of several of sulfates, nitrates, and chlorides of modified metals such as nickel nitrate, magnesium nitrate, iron nitrate, manganese nitrate, potassium nitrate, zinc sulfate, and lanthanum nitrate.

[0020] As a specific embodiment of the above preparation method of the present invention, based on the total weight of the IM-5 molecular sieve being 100%, the addition amount of the modified metal precursor in terms of the modified metal oxide is 0.5%-5.0%, preferably 1.0-3.0%.

[0021] As a specific embodiment of the above preparation method of the present invention, the mass ratio of the IM-5 molecular sieve to water in the impregnating solution containing the modified metal precursor is 1:2-10, preferably 1:3-5. The present invention has no special requirements for the chemical composition, crystal grain size, etc. of the IM-5 molecular sieve, and can be reasonably selected and adjusted according to the actual on-site operation needs.

[0022] As a specific embodiment of the above preparation method of the present invention, in Step (1), the mixed slurry is stirred for 10-30 h under the conditions of a temperature of 100-180°C and a pressure of 0.1-1.0 MPa. Preferably, the mixed slurry is stirred for 12-20 h under the conditions of a temperature of 120-150°C and a pressure of 0.1-1.0 MPa.

[0023] As a specific embodiment of the preparation method described above of the present invention, in step (2), the temperature of the ultrasonic treatment is 40 - 80 °C, and the time is 20 - 40 min. Preferably, the temperature of the ultrasonic treatment is 40 - 60 °C, and the time is 20 - 30 min.

[0024] In steps (1) and (2) of the preparation method described above of the present invention, impregnation is carried out under high-temperature and high-pressure stirring conditions and under ultrasonic conditions respectively. On the one hand, under high-temperature and high-pressure stirring conditions, the modified metal ions in the impregnating solution are more likely to migrate into the framework of the IM-5 molecular sieve, improving the framework cation exchange degree of the IM-5 molecular sieve and modulating the acidic properties of the IM-5 molecular sieve. On the other hand, under ultrasonic conditions, the high-frequency vibration of ultrasonic waves can make the IM-5 molecular sieve particles more evenly dispersed in the impregnating solution, thereby improving the dispersion degree of the modified metal ions on the surface and in the pores of the IM-5 molecular sieve; in addition, ultrasonic waves can also accelerate the reaction between the metal ions in the impregnating solution and the cations in the framework of the IM-5 molecular sieve, improving the impregnation efficiency. Therefore, the modified IM-5 molecular sieve prepared by using the preparation method provided by the present invention has higher metal dispersion, and when it is used as a catalyst for catalytic cracking of light hydrocarbons to produce lower olefins, it has better cracking performance.

[0025] As a specific embodiment of the preparation method described above of the present invention, in step (3), the temperature of the calcination is 400 - 600 °C, and the time is 2 - 6 h. Preferably, the temperature of the calcination is 500 - 600 °C, and the time is 2 - 4 h.

[0026] The present invention does not make specific requirements on the operations and conditions such as evaporation to dryness and drying in step (3), and can be reasonably adjusted according to the actual on-site operation needs, as long as the purpose of evaporation to dryness and drying can be achieved. For example, in some embodiments of the present invention, in step (3), under water bath conditions, it is stirred to evaporate to dryness at 120 °C, and then the evaporated mixture is placed in an oven at 120 °C for drying treatment for 12 h.

[0027] On the other hand, the present invention also provides the application of the modified IM-5 molecular sieve described above as a catalyst in the catalytic cracking of light hydrocarbons to produce lower olefins.

[0028] As a specific embodiment of the application described above of the present invention, the light hydrocarbons include lower alkanes and the like.

[0029] Compared with the prior art, the beneficial technical effects that the present invention can achieve include:

[0030] (1) The preparation method of the modified IM-5 molecular sieve provided by this application adopts an impregnation method combining high-temperature pressurized stirring and ultrasonic treatment, that is, the high-temperature pressurized and ultrasonic impregnation method is used to mix and impregnate the IM-5 molecular sieve and the impregnation solution containing the modified metal precursor to obtain the modified IM-5 molecular sieve. This can improve the dispersion of metal species on the inner and outer surfaces of the IM-5 molecular sieve (that is, the surfaces of the pores contained in the IM-5 molecular sieve and the outer surface of the IM-5 molecular sieve) and the concentration of metal ions in the framework, reduce the agglomeration of the modified metal, improve the utilization rate of the modified metal, modulate the acidic properties of the IM-5 molecular sieve, and the preparation method is easy to operate.

[0031] (2) The modified IM-5 molecular sieve provided by the present invention has higher dispersion of the modified metal, and more modified metal species enter the framework of the IM-5 molecular sieve. When it is used as a catalyst for catalytic cracking of light hydrocarbons to produce lower olefins, it has better cracking performance, higher reaction activity and lower olefin selectivity, and a high yield of lower olefins. Description of the Drawings

[0032] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for use in the description of the embodiments. Obviously, the drawings in the following description are some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0033] Figure 1a It is the TEM image of S3 in Characterization Test Example 1 of the present invention.

[0034] Figure 1b It is the TEM image of D1 in Characterization Test Example 1 of the present invention.

[0035] Figure 1c It is the TEM image of D2 in Characterization Test Example 1 of the present invention.

[0036] Figure 1d It is the TEM image of D3 in Characterization Test Example 1 of the present invention.

[0037] Figure 2 It is the NH 3 -TPD images of S3, D1 and D3 in Characterization Test Example 2 of the present invention. Detailed Embodiments

[0038] It should be noted that the term "including" and any of its variations in the description, claims, and the above-mentioned drawings of the present invention are intended to cover non-exclusive inclusion. For example, a process, method, system, product, or device that includes a series of steps or units does not necessarily have to be limited to those steps or units clearly listed, but may include other steps or units that are not clearly listed or are inherent to these processes, methods, products, or devices.

[0039] The "ranges" disclosed in the present invention are given in the form of lower and upper limits. There can be one or more lower limits, and one or more upper limits. A given range is defined by selecting a lower limit and an upper limit. The selected lower limit and upper limit define the boundaries of a particular range. All ranges defined in this way are combinable, that is, any lower limit can be combined with any upper limit to form a range. For example, if ranges of 60 - 120 and 80 - 110 are listed for a specific parameter, ranges of 60 - 110 and 80 - 120 are also contemplated. In addition, if the minimum range values listed are 1 and 2, and the maximum range values listed are 3, 4, and 5, then the following ranges are all contemplated: 1 - 3, 1 - 4, 1 - 5, 2 - 3, 2 - 4, and 2 - 5.

[0040] In the present invention, unless otherwise specified, the numerical range "a - b" represents an abbreviated representation of any real number combination between a and b, where a and b are both real numbers. For example, the numerical range "0 - 5" means that all real numbers between "0 - 5" are fully listed in the present invention, and "0 - 5" is just an abbreviated representation of these numerical combinations.

[0041] In the present invention, if there is no special instruction, all the embodiments and preferred embodiments mentioned in the present invention can be combined with each other to form a new technical solution.

[0042] In the present invention, if there is no special instruction, all the technical features and preferred features mentioned in the present invention can be combined with each other to form a new technical solution.

[0043] In the present invention, if there is no special instruction, all the steps mentioned herein can be carried out sequentially or randomly, but preferably sequentially. For example, the method includes steps (a) and (b), which means that the method can include steps (a) and (b) carried out sequentially, or can also include steps (b) and (a) carried out sequentially. For example, it is mentioned that the method may further include step (c), which means that step (c) can be added to the method in any order. For example, the method can include steps (a), (b), and (c), or can also include steps (a), (c), and (b), or can also include steps (c), (a), and (b), etc.

[0044] In order to make the objectives, technical solutions and advantages of the present invention clearer and more understandable, the present invention will be further described in detail below in conjunction with the attached tables, drawings and embodiments. The following described embodiments are some embodiments of the present invention, rather than all embodiments, and are only used to illustrate the present invention and should not be construed as limiting the scope of the present invention. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without making creative efforts fall within the scope of protection of the present invention. For those conditions not specified in the embodiments, they are carried out according to conventional conditions or conditions recommended by the manufacturer. For the reagents or instruments whose manufacturers are not specified, they are all conventional products that can be obtained through commercial purchase.

[0045] For example, the IM-5 molecular sieve used in the embodiments and comparative examples of the present invention was obtained by self-preparation in the laboratory. The preparation steps were as follows: Weigh a certain amount of distilled water, sodium hydroxide and sodium aluminate and stir them evenly in a water bath at 60 °C; During the stirring process, 1,5-bis(N-methylpyrrolidinium)pentane bromide was added dropwise, and after the addition was completed, stirring was continued for 1 h; Colloidal silica was added dropwise under stirring, and after the addition was completed, stirring was continued for 2 h; The obtained mixed solution was taken out and placed in a high-pressure reaction kettle with a polytetrafluoroethylene inner liner, and dynamically crystallized at 175 °C for 144 h to obtain an IM-5 molecular sieve with a silica-alumina ratio of 32.

[0046] Nickel nitrate, magnesium nitrate, lanthanum nitrate, etc. are all hexahydrate nitrate compounds, which are of analytical purity and produced by Sinopharm.

[0047] Example 1

[0048] This example provides a modified IM-5 molecular sieve, which is prepared by a preparation method including the following specific steps:

[0049] Step 1): Dissolve 0.194 g of nickel nitrate in 40 g of deionized water. After complete dissolution, add 10 g of IM-5 molecular sieve to the solution;

[0050] Step 2): Transfer the mixture obtained in Step 1) into a high-pressure reaction kettle with a polytetrafluoroethylene inner liner, and stir at a temperature of 120 °C and a pressure of 0.2 MPa for 24 h;

[0051] Step 3): Take out the mixed solution obtained in Step 2) above and place it in an ultrasonic instrument for treatment at 40 °C for 20 min;

[0052] Step 4): Then place the mixed solution obtained in Step 3) above in a water bath at 120 °C for evaporation to dryness. Take out the dried modified sample and dry it in an oven at 120 °C for 12 h. Finally, take out the dried sample and calcine it at 400 °C for 6 h to obtain a modified IM-5 molecular sieve sample, named S1.

[0053] Example 2

[0054] This example provides a modified IM-5 molecular sieve, which is prepared by a preparation method including the following specific steps:

[0055] Step 1): Dissolve 0.388 g of nickel nitrate in 40 g of deionized water. After complete dissolution, add 10 g of IM-5 molecular sieve to the solution;

[0056] Step 2): Transfer the mixture obtained in Step 1) into a high-pressure reaction kettle with a polytetrafluoroethylene inner lining, and stir at a temperature of 120 °C and a pressure of 0.8 MPa for 24 h;

[0057] Step 3): Take out the mixed solution obtained in Step 2) above and place it in an ultrasonic instrument for treatment at 40 °C for 20 min;

[0058] Step 4): Then place the mixed solution obtained in Step 3) above in a water bath at 120 °C for evaporation to dryness. Take out the dried modified sample and put it in an oven for drying at 120 °C for 12 h. Finally, take out the dried sample and calcine it at 600 °C for 2 h to obtain a modified IM-5 molecular sieve sample, named S2.

[0059] Example 3

[0060] This example provides a modified IM-5 molecular sieve, which is prepared by a preparation method including the following specific steps:

[0061] Step 1): Dissolve 1.164 g of nickel nitrate in 40 g of deionized water. After complete dissolution, add 10 g of IM-5 molecular sieve to the solution;

[0062] Step 2): Transfer the mixture obtained in Step 1) into a high-pressure reaction kettle with a polytetrafluoroethylene inner lining, and stir at a temperature of 120 °C and a pressure of 0.5 MPa for 30 h;

[0063] Step 3): Take out the mixed solution obtained in Step 2) above and place it in an ultrasonic instrument for treatment at 40 °C for 20 min;

[0064] Step 4): Then place the mixed solution obtained in Step 3) above in a water bath at 120 °C for evaporation to dryness. Take out the dried modified sample and put it in an oven for drying at 120 °C for 12 h. Finally, take out the dried sample and calcine it at 500 °C for 4 h to obtain a modified IM-5 molecular sieve sample, named S3.

[0065] Example 4

[0066] This example provides a modified IM-5 molecular sieve, which is prepared by a preparation method including the following specific steps:

[0067] Step 1): Dissolve 1.94 g of nickel nitrate in 40 g of deionized water. After complete dissolution, add 10 g of IM-5 molecular sieve to the solution;

[0068] Step 2): Transfer the mixture obtained in Step 1) into a high-pressure reactor lined with polytetrafluoroethylene, and stir for 16 h at a temperature of 180 °C and a pressure of 0.5 MPa;

[0069] Step 3): Take out the mixed solution obtained in Step 2) above and place it in an ultrasonic instrument for treatment at 40 °C for 40 min;

[0070] Step 4): Then place the mixed solution obtained in Step 3) above in a water bath at 120 °C for evaporation to dryness. Take out the dried modified sample and put it in an oven for drying at 120 °C for 12 h. Finally, take out the dried sample and calcine it at 500 °C for 4 h to obtain a modified IM-5 molecular sieve sample, named S4.

[0071] Example 5

[0072] This example provides a modified IM-5 molecular sieve, which is prepared by a preparation method including the following specific steps:

[0073] Step 1): Weigh 0.388 g of nickel nitrate and 0.266 g of lanthanum nitrate respectively and dissolve them in 40 g of deionized water. After complete dissolution, add 10 g of IM-5 molecular sieve to the solution;

[0074] Step 2): Transfer the mixture obtained in Step 1) into a high-pressure reactor lined with polytetrafluoroethylene, and stir for 18 h at a temperature of 150 °C and a pressure of 0.2 MPa;

[0075] Step 3): Take out the mixed solution obtained in Step 2) above and place it in an ultrasonic instrument for treatment at 60 °C for 30 min;

[0076] Step 4): Then place the mixed solution obtained in Step 3) above in a water bath at 120 °C for evaporation to dryness. Take out the dried modified sample and put it in an oven for drying at 120 °C for 12 h. Finally, take out the dried sample and calcine it at 500 °C for 4 h to obtain a modified IM-5 molecular sieve sample, named S5.

[0077] Example 6

[0078] This example provides a modified IM-5 molecular sieve, which is prepared by a preparation method including the following specific steps:

[0079] Step 1): Weigh 0.64 g of magnesium nitrate and 0.266 g of lanthanum nitrate respectively and dissolve them in 40 g of deionized water. After complete dissolution, add 10 g of IM-5 molecular sieve to the solution;

[0080] Step 2): Transfer the mixture obtained in Step 1) into a high-pressure reactor with a polytetrafluoroethylene liner, and stir it at a temperature of 150 °C and a pressure of 0.5 MPa for 20 h;

[0081] Step 3): Take out the mixed solution obtained in Step 2) above and place it in an ultrasonic instrument for treatment at 40 °C for 30 min;

[0082] Step 4): Then place the mixed solution obtained in Step 3) above in a water bath at 120 °C for evaporation to dryness. Take out the dried modified sample and put it in an oven for drying at 120 °C for 12 h. Finally, take out the dried sample and calcine it at 500 °C for 4 h to obtain a modified IM-5 molecular sieve sample, named S6.

[0083] Example 7

[0084] This example provides a modified IM-5 molecular sieve, which is prepared by a preparation method including the following specific steps:

[0085] Step 1): Dissolve 0.194 g of nickel nitrate in 40 g of deionized water. After complete dissolution, add 10 g of IM-5 molecular sieve to the solution;

[0086] Step 2): Transfer the mixture obtained in Step 1) into a high-pressure reactor with a polytetrafluoroethylene liner, and stir it at a temperature of 120 °C and a pressure of 0.2 MPa for 24 h;

[0087] Step 3): Take out the mixed solution obtained in Step 2) above and place it in an ultrasonic instrument for treatment at 80 °C for 20 min;

[0088] Step 4): Then place the mixed solution obtained in Step 3) above in a water bath at 120 °C for evaporation to dryness. Take out the dried modified sample and put it in an oven for drying at 120 °C for 12 h. Finally, take out the dried sample and calcine it at 500 °C for 4 h to obtain a modified IM-5 molecular sieve sample, named S7.

[0089] Example 8

[0090] This example provides a modified IM-5 molecular sieve, which is prepared by a preparation method including the following specific steps:

[0091] Step 1): Dissolve 0.388 g of nickel nitrate in 20 g of deionized water. After complete dissolution, add 10 g of IM-5 molecular sieve to the solution;

[0092] Step 2): Transfer the mixture obtained in Step 1) into a high-pressure reactor with a polytetrafluoroethylene liner, and stir it at a reaction temperature of 120 °C and a pressure of 0.8 MPa for 24 h;

[0093] Step 3): Take out the mixture obtained in the above Step 2) and place it in an ultrasonic instrument for treatment at 40 °C for 20 min;

[0094] Step 4): Then place the mixture obtained in the above Step 3) in a water bath at 120 °C for evaporation to dryness. Take out the modified sample after evaporation to dryness and put it in an oven for drying at 120 °C for 12 h. Finally, take out the dried sample and calcine it at 500 °C for 4 h to obtain a modified IM-5 molecular sieve sample, named S8.

[0095] Example 9

[0096] This example provides a modified IM-5 molecular sieve, which is prepared by a preparation method including the following specific steps:

[0097] Step 1): Dissolve 0.388 g of nickel nitrate in 60 g of deionized water. After complete dissolution, add 10 g of IM-5 molecular sieve to the solution;

[0098] Step 2): Transfer the mixture obtained in Step 1) into a high-pressure reaction kettle with a polytetrafluoroethylene inner liner, and stir at a reaction temperature of 120 °C and a pressure of 0.8 MPa for 24 h;

[0099] Step 3): Take out the mixture obtained in the above Step 2) and place it in an ultrasonic instrument for treatment at 40 °C for 20 min;

[0100] Step 4): Then place the mixture obtained in the above Step 3) in a water bath at 120 °C for evaporation to dryness. Take out the modified sample after evaporation to dryness and put it in an oven for drying at 120 °C for 12 h. Finally, take out the dried sample and calcine it at 500 °C for 4 h to obtain a modified IM-5 molecular sieve sample, named S9.

[0101] Example 10

[0102] This example provides a modified IM-5 molecular sieve, which is prepared by a preparation method including the following specific steps:

[0103] Step 1): Dissolve 0.388 g of nickel nitrate in 100 g of deionized water. After complete dissolution, add 10 g of IM-5 molecular sieve to the solution;

[0104] Step 2): Transfer the mixture obtained in Step 1) into a high-pressure reaction kettle with a polytetrafluoroethylene inner liner, and stir at a reaction temperature of 120 °C and a pressure of 0.8 MPa for 24 h;

[0105] Step 3): Take out the mixture obtained in the above Step 2) and place it in an ultrasonic instrument for treatment at 40 °C for 20 min;

[0106] Step 4): Then, place the mixture obtained in Step 3) above in a water bath at 120 °C for evaporation to dryness. Take out the modified sample after evaporation and dry it in an oven at 120 °C for 12 h. Finally, take out the dried sample and calcine it at 500 °C for 4 h to obtain a modified IM-5 zeolite sample, named S10.

[0107] Example 11

[0108] This example provides a modified IM-5 zeolite, which is prepared by a preparation method including the following specific steps:

[0109] Step 1): Dissolve 0.215 g of potassium nitrate in 60 g of deionized water. After complete dissolution, add 10 g of IM-5 zeolite to the solution;

[0110] Step 2): Transfer the mixture obtained in Step 1) into a high-pressure reactor lined with polytetrafluoroethylene, and stir at a reaction temperature of 120 °C and a pressure of 0.8 MPa for 24 h;

[0111] Step 3): Take out the mixture obtained in Step 2) above and place it in an ultrasonic instrument for treatment at 40 °C for 20 min;

[0112] Step 4): Then, place the mixture obtained in Step 3) above in a water bath at 120 °C for evaporation to dryness. Take out the modified sample after evaporation and dry it in an oven at 120 °C for 12 h. Finally, take out the dried sample and calcine it at 600 °C for 2 h to obtain a modified IM-5 zeolite sample, named S11.

[0113] Comparative Example 1

[0114] This comparative example provides a modified IM-5 zeolite, which is prepared by a preparation method including the following specific steps:

[0115] Dissolve 1.164 g of nickel nitrate in 12.5 g of deionized water. While stirring, add the obtained solution dropwise to 10 g of IM-5 zeolite, and add dropwise while stirring;

[0116] After the addition is completed, place the sample in an oven and dry it at 120 °C for 12 h. Take out the dried sample and calcine it at 500 °C for 4 h to obtain a modified IM-5 zeolite sample, named D1.

[0117] Comparative Example 2

[0118] This comparative example provides a modified IM-5 zeolite, which is prepared by a preparation method including the following specific steps:

[0119] Dissolve 1.164 g of nickel nitrate in 40 g of deionized water. After complete dissolution, add 10 g of IM-5 zeolite to the solution;

[0120] Transfer the mixture obtained in the previous step into a high-pressure reactor lined with polytetrafluoroethylene, and stir it at a temperature of 120 °C and a pressure of 0.5 MPa for 30 h;

[0121] After that, place the mixed solution obtained in the previous step in a water bath at 120 °C for evaporation to dryness. Take out the modified sample after evaporation and dry it in an oven at 120 °C for 12 h. Finally, take out the dried sample and calcine it at 500 °C for 4 h to obtain a modified IM-5 molecular sieve sample, named D2.

[0122] Comparative Example 3

[0123] This comparative example provides a modified IM-5 molecular sieve, which is prepared by a preparation method including the following specific steps:

[0124] Dissolve 1.164 g of nickel nitrate in 40 g of deionized water. After complete dissolution, add 10 g of IM-5 molecular sieve to the solution;

[0125] Transfer the mixture obtained in the previous step into an ultrasonic instrument and treat it at 40 °C for 20 min;

[0126] After that, place the mixed solution obtained in the previous step in a water bath at 120 °C for evaporation to dryness. Take out the modified sample after evaporation and dry it in an oven at 120 °C for 12 h. Finally, take out the dried sample and calcine it at 500 °C for 4 h to obtain a modified IM-5 molecular sieve sample, named D3.

[0127] Characterization Test Example 1

[0128] In this test example, transmission electron microscopy characterization and analysis were performed on S3, D1, D2, and D3 respectively to investigate the dispersion degree and crystal grain size of the modified metal oxide. The obtained results are as Figures 1a - 1d shown. By comparison Figures 1a - 1d It can be seen that for the modified IM-5 molecular sieve sample prepared by the high-temperature pressurized stirring and ultrasonic impregnation method in Example 3 of the present invention, that is, the dispersion degree of nickel oxide in S3 is better and the crystal grain size is smaller.

[0129] Characterization Test Example 2

[0130] In this test example, NH 3 -TPD analysis was performed on S3, D1, and D3 respectively. The obtained NH 3 -TPD diagrams are as Figure 2 shown. From Figure 2It can be seen that, compared with D1 and D3, the modified IM-5 molecular sieve sample prepared by the high-temperature pressurized stirring and ultrasonic impregnation method in Example 3 of the present invention, namely S3, has more total acid amount and strong acid amount. This can indirectly prove that when preparing the modified IM-5 molecular sieve by the high-temperature pressurized stirring and ultrasonic impregnation method in Example 3, the metal ions in the impregnating solution are more likely to migrate into the IM-5 molecular sieve framework, improving the cation exchange degree of the IM-5 molecular sieve framework and modulating the acid properties of the molecular sieve. That is, in S3, more modified metal species enter the IM-5 molecular sieve framework.

[0131] Application Example 1

[0132] In this application example, the modified IM-5 molecular sieve samples obtained in Example 3, Comparative Example 1, Comparative Example 2, and Comparative Example 3 above were respectively used as catalysts to evaluate the light hydrocarbon catalytic cracking reaction on a fixed-bed micro-reactor. The reaction conditions were as follows: n-hexane was used as the raw material, the reaction temperature was 500 °C, the catalyst dosage was 1.0 g, at atmospheric pressure, and the mass space velocity was 6 h -1 , and the carrier gas was N 2 and the flow rate of the carrier gas was 80 mL / min. The evaluation process included the following specific steps: First, the modified IM-5 molecular sieve sample was pressed into tablets and sieved into 40-60 mesh particles, and the prepared modified IM-5 molecular sieve particles were dried at 120 °C; then, 1 g of the dried modified IM-5 molecular sieve particles was weighed and loaded into the reaction tube, and then activated pretreatment was carried out in a nitrogen atmosphere. The pretreatment conditions were activation at 500 °C for 2 h; after the pretreatment was completed, the light hydrocarbon raw material was injected into the reaction tube through a plunger pump to contact with the catalyst for catalytic cracking reaction to obtain light olefins. The product distribution was analyzed online by Agilent 7890A gas chromatography, and the product distribution results are shown in Table 1.

[0133] Table 1 Product distribution of n-hexane cracking catalyzed by S3, D1, D2, and D3 as catalysts

[0134]

[0135] Note: Yield of light olefins a = Yield of ethylene + propylene + butene.

[0136] From the experimental data in Table 1, it can be seen that compared with D1-D3 prepared in the comparative examples, the modified IM-5 molecular sieve sample prepared by the high-temperature pressurized stirring and ultrasonic impregnation method in Example 3 of the present invention, namely S3, has a higher n-hexane conversion rate and light olefin yield in the n-hexane catalytic cracking reaction.

[0137] As described above, the above are only specific embodiments of the present invention, and the scope of the invention cannot be limited thereby. Therefore, the replacement of equivalent components, or equivalent changes and modifications made in accordance with the scope of protection of the present invention, should still fall within the scope covered by this patent. In addition, the technical features in the present invention can be freely combined and used among technical features, between technical features and technical inventions, and between technical inventions.

Claims

1. A modified IM-5 molecular sieve, characterized in that, the modified IM-5 molecular sieve comprises an IM-5 molecular sieve and a modified metal, wherein a part of the modified metal is loaded on the outer surface of the IM-5 molecular sieve and the surface of its pores in the form of a modified metal oxide, and another part of the modified metal enters into the framework of the IM-5 molecular sieve in the form of forming chemical bonds; wherein, the modified metal comprises one or a combination of several of alkali metals, alkaline earth metals and transition metals.

2. The modified IM-5 molecular sieve according to claim 1, characterized in that, calculated based on the total weight of the IM-5 molecular sieve being 100%, the content of the modified metal calculated as the modified metal oxide is 0.5%-5.0%.

3. A preparation method of the modified IM-5 molecular sieve according to claim 1 or 2, characterized in that, the preparation method comprises: Step (1): Mix the IM-5 molecular sieve powder with an impregnating solution containing a modified metal precursor uniformly to obtain a mixed slurry, and stir the mixed slurry under high temperature and high pressure conditions; Step (2): Perform ultrasonic treatment on the mixed slurry after the stirring treatment in Step (1); Step (3): Evaporate the mixed slurry after the ultrasonic treatment in Step (2) to dryness, and then dry and calcine the dried mixture to obtain the modified IM-5 molecular sieve.

4. The preparation method according to claim 3, characterized in that, the modified metal precursor is a water-soluble salt of the modified metal, including one or a combination of several of sulfates, nitrates and chlorides of the modified metal.

5. The preparation method according to claim 3 or 4, characterized in that, calculated based on the total weight of the IM-5 molecular sieve being 100%, the addition amount of the modified metal precursor calculated as the modified metal oxide is 0.5%-5.0%.

6. The preparation method according to claim 3 or 4, characterized in that, the mass ratio of the IM-5 molecular sieve to water in the impregnating solution containing the modified metal precursor is 1:2-10.

7. The preparation method according to claim 3 or 4, characterized in that, in Step (1), the mixed slurry is stirred for 10-30 h under the conditions of a temperature of 100-180 °C and a pressure of 0.1-1.0 MPa.

8. The preparation method according to claim 3 or 4, characterized in that, in Step (2), the temperature of the ultrasonic treatment is 40-80 °C and the time is 20-40 min.

9. The preparation method according to claim 3 or 4, characterized in that, in Step (3), the calcination temperature is 400-600 °C and the time is 2-6 h.

10. Application of the modified IM-5 molecular sieve according to claim 1 or 2 as a catalyst in the catalytic cracking of light hydrocarbons to produce lower olefins.

11. The application according to claim 10, characterized in that, the light hydrocarbons include lower alkanes.

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