Ni-coated HZSM-5 catalyst as well as preparation method and application thereof

Abstract

The invention provides a Ni-coated HZSM-5 catalyst and a preparation method and application thereof, the catalyst comprises an HZSM-5 molecular sieve and nickel nanoparticles, and the nickel nanoparticles are embedded in pores or crystals of the HZSM-5 molecular sieve or loaded on the outer surface of the HZSM-5 molecular sieve. According to the invention, the nickel nanoparticles are embedded in the HZSM-5 molecular sieve, that is, most of the nickel nanoparticles are embedded in pores or crystals of the HZSM-5 molecular sieve, so that the catalytic activity and stability of the obtained catalyst can be remarkably improved, and the catalyst has excellent target product selectivity and long service life. The catalyst provided by the invention has the advantages of good low-temperature activity, easy activation of low-carbon alkanes, high selectivity of low-carbon alkanes, excellent carbon deposition resistance, effective inhibition of sintering of Ni nanoparticles, and the like.

Description

Technical Field

[0001] The present invention relates to a Ni@HZSM-5 catalyst, a preparation method and an application thereof, belonging to the technical fields of oil refining and chemical engineering. Background Art

[0002] C4 alkanes mainly come from the catalytic cracking process in the petroleum processing process. They have strong chemical stability, are difficult to activate, have low chemical utilization rate, and are basically used as fuels with low economic added value. Light olefins such as ethylene and propylene are important organic chemical raw materials, and their market demand is increasing continuously. Improving the production of light olefins has become an urgent problem to be solved. Therefore, the catalytic cracking of n-butane into light olefins with high added value has attracted wide attention.

[0003] In the early stage, HZSM-5 catalyst was used for the catalytic cracking of n-butane. Those skilled in the art improved its low-temperature catalytic cracking activity by introducing metals to form a dehydrogenation-cracking bifunctional catalyst, realizing the synergistic effect between the metal dehydrogenation active center and the acidic active center of the molecular sieve, reducing the reaction temperature, improving the activation ability of the molecular sieve for alkanes, promoting the dehydrogenation reaction of alkane molecules, and the generated butene undergoes a cracking reaction at the acidic sites of the ZSM-5 molecular sieve, improving the catalytic cracking activity of the ZSM-5 molecular sieve for alkanes, which is beneficial to improving the selectivity and yield of light olefins. Currently, the impregnation method is usually used to prepare the dehydrogenation-cracking bifunctional catalyst, which has the characteristics of simple operation and low cost, but the stability of the catalyst is not good. For the bifunctional catalyst prepared by the impregnation method, the metal particles of the dehydrogenation component are mainly supported on the surface of the catalyst, and the interaction between the metal and the support is weak, which is easy to migrate and agglomerate during the reaction, sinter into larger metal particles, and cause the catalyst to deactivate.

[0004] The development of catalysts is the key to the catalytic cracking process of light alkanes. In this regard, the applicant will briefly introduce some prior arts related to the present application.

[0005] Prior art document 1, literature source: Zhang Wenfang, Wang Pengzhao, Yang Chaohe, etc. High-temperature cracking reaction of n-butane on HZSM-5 molecular sieve [J]. Petrochemical Technology & Application, 2018, 36(06): 382-385.; related technical description: studying the high-temperature cracking reaction of n-butane on HZSM-5 molecular sieve by changing the silicon-aluminum ratio; the defect of this technology or the deficiency compared with the present invention is that the reaction temperature is high, and on the HZSM-5 molecular sieve with a low silicon-aluminum ratio, olefins are prone to undergo hydrogen transfer reaction to generate alkanes, resulting in an increase in the selectivity of light alkanes and a decrease in the selectivity of light olefins.

[0006] Prior art document 2, source: Jiang Guiyuan, Lu Jiangyin, Duan Aijun, etc. Study on the performance of transition metal Fe modified HZSM-5 zeolite in catalytic cracking of C4 alkanes to produce light olefins [C]. Catalysis Committee of Chinese Chemical Society. Proceedings of the 11th National Youth Catalysis Academic Conference (Part I). 2007: 83-84.; Technical description: This prior art studied the performance of transition metal Fe modified HZSM-5 zeolite in catalytic cracking of C4 alkanes to produce light olefins; The defect of this technology or the deficiency compared with the present invention is that the reaction temperature is high and the selectivity of light olefins has not been improved.

[0007] Prior art document 3, source: Liao Zhengkun, Dilnur·Aili, Fang Yaping, etc. Effect of potassium modification on the cracking performance of n-butane over Au / ZSM-5 catalyst [J]. Journal of Molecular Catalysis, 2023, 37(02): 118-129.; Technical description: This prior art studied the effect of potassium modification on the cracking performance of n-butane over Au / ZSM-5 catalyst; The defect of this technology or the deficiency compared with the present invention is that precious metals are used as catalysts, which are expensive.

[0008] Therefore, it has become an urgent technical problem in the field to provide a novel Ni@HZSM-5 catalyst for catalytic cracking of n-butane, its preparation method and application. Summary of the Invention

[0009] In order to solve the above-mentioned disadvantages and deficiencies, an object of the present invention is to provide a Ni@HZSM-5 catalyst.

[0010] Another object of the present invention is also to provide a preparation method of the above-mentioned Ni@HZSM-5 catalyst.

[0011] Another object of the present invention is also to provide the application of the above-mentioned Ni@HZSM-5 catalyst in the catalytic cracking of n-butane to produce small molecule olefins.

[0012] In order to achieve the above objects, on the one hand, the present invention provides a Ni@HZSM-5 catalyst, wherein the Ni@HZSM-5 catalyst comprises HZSM-5 zeolite and nickel nanoparticles, and the nickel nanoparticles are embedded in the pores or crystals of the HZSM-5 zeolite, or supported on the outer surface of the HZSM-5 zeolite.

[0013] As a specific embodiment of the catalyst described above in the present invention, the HZSM-5 molecular sieve is spherical particles of HZSM-5 molecular sieve, and the nickel nanoparticles are embedded in the pores or crystals of the HZSM-5 molecular sieve in a highly dispersed or uniformly dispersed manner, or are loaded on the outer surface of the HZSM-5 molecular sieve. Among them, most of the nickel nanoparticles are embedded in the pores or crystals of the HZSM-5 molecular sieve, and a small part of the nickel nanoparticles are not successfully embedded and are loaded on the outer surface of the HZSM-5 molecular sieve.

[0014] As a specific embodiment of the catalyst described above in the present invention, based on the total weight of the HZSM-5 molecular sieve being 100%, the content of the nickel nanoparticles is 0.1-2 wt%.

[0015] On the other hand, the present invention also provides a preparation method of the Ni@HZSM-5 catalyst described above, wherein the preparation method includes:

[0016] Step (1): Uniformly drop an aqueous solution of nickel salt on SiO 2 by the equal-volume impregnation method and mix evenly, and then obtain NiO / SiO 2 after drying and calcination; in NiO / SiO 2 , NiO is loaded on the surface of SiO 2 .

[0017] Step (2): Prepare a solution containing a template agent, an alkali, and an aluminum source, add NiO / SiO 2 to the solution and allow it to hydrolyze fully to obtain a gel-like substance;

[0018] Step (3): Subject the gel-like substance to hydrothermal crystallization, and then calcine the hydrothermal crystallization product;

[0019] Step (4): Subject the product calcined in step (3) to ion exchange with an aqueous ammonium salt solution;

[0020] Step (5): Dry the product after ion exchange in step (4) and then calcine it to obtain NiO@HZSM-5;

[0021] Step (6): Reduce NiO@HZSM-5 in a hydrogen-nitrogen mixed gas atmosphere to obtain the Ni@HZSM-5 catalyst.

[0022] As a specific embodiment of the preparation method described above in the present invention, the preparation method further includes: taking a certain mass of SiO 2 treated by pretreatment, such as ordinary drying treatment, and placing it in an eggplant-shaped flask, and then gradually drop deionized water into it while constantly shaking; when SiO 2Stop dropping when the carrier reaches the adsorption saturation critical state, weigh the mass of SiO at this time 2 , and calculate its water absorption rate. Take the average of three measurements as the average water absorption rate of SiO 2 ;

[0023] Calculate the impregnation solution required for the equal-volume impregnation method according to the average water absorption rate, that is, the volume of the aqueous solution of nickel salt, and prepare an aqueous solution of nickel salt that meets the requirements according to the results.

[0024] As a specific embodiment of the above preparation method of the present invention, in step (1), the nickel salt includes one or a combination of several of nickel chloride, nickel nitrate, nickel sulfate, etc.

[0025] As a specific embodiment of the above preparation method of the present invention, in step (1), the calcination is carried out at 350-600°C for 1-6 hours.

[0026] As a specific embodiment of the above preparation method of the present invention, in step (2), the mass ratio of the template agent, alkali, aluminum source and NiO / SiO 2 is 1-6:0.1-2:0.01-2:1-6.

[0027] As a specific embodiment of the above preparation method of the present invention, in step (2), the template agent includes tetrapropylammonium hydroxide, etc.;

[0028] The alkali includes sodium hydroxide, etc.;

[0029] The aluminum source includes one or a combination of several of aluminum isopropoxide, aluminum nitrate, aluminum sulfate, sodium metaaluminate, etc.

[0030] As a specific embodiment of the above preparation method of the present invention, in step (3), the hydrothermal crystallization temperature is 100-200°C and the time is 12-72 hours.

[0031] As a specific embodiment of the above preparation method of the present invention, in step (3), the calcination is carried out at 450-700°C for 2-8 hours.

[0032] As a specific embodiment of the above preparation method of the present invention, in step (4), the ion exchange temperature is 50-90°C, and it is carried out 1-3 times, each time for 1-3 hours.

[0033] As a specific embodiment of the above preparation method of the present invention, in step (5), the calcination is carried out at 450-700°C for 1-3 hours.

[0034] As a specific embodiment of the above-described preparation method of the present invention, in step (6), the reduction temperature is 450 - 650 °C, the flow rate of the hydrogen-nitrogen mixed gas is 10 - 50 mL / min, and based on the total volume of the hydrogen-nitrogen mixed gas being 100%, the content of hydrogen is 1 - 50%.

[0035] In another aspect, the present invention also provides the application of the above-described Ni@HZSM-5 catalyst in the catalytic cracking of n-butane to produce light olefins.

[0036] As a specific embodiment of the above-described application of the present invention, in the catalytic cracking, the temperature is 450 - 650 °C and the pressure is 0.1 - 2.5 MPa.

[0037] Compared with the prior art, the beneficial technical effects that the present invention can achieve include:

[0038] In the present invention, nickel nanoparticles are embedded in the HZSM-5 molecular sieve, that is, most of the nickel nanoparticles are embedded in the pores or crystals of the HZSM-5 molecular sieve, which can significantly improve the catalytic activity and stability of the obtained catalyst, so that the catalyst has excellent target product selectivity and long life.

[0039] The catalyst provided by the present invention has the advantages of good low-temperature activity, easy activation of light alkanes, high selectivity for light olefins, excellent anti-coking performance, and effective inhibition of sintering of Ni nanoparticles.

[0040] The Ni@HZSM-5 catalyst provided by the present invention is composed of spherical particles of HZSM-5 molecular sieve embedded with highly dispersed Ni nanoparticles. Compared with HZSM-5, the Ni@HZSM-5 catalyst exhibits excellent catalytic performance for n-butane cracking and selectivity for light olefins. This core-shell structure catalyst can not only provide a large number of Ni metal centers and Lewis center interfaces, enhancing the dehydrogenation performance of the Ni active component, but also enable the pore structure and acidity of the HZSM-5 molecular sieve to form a synergistic effect. In addition, this catalyst can also inhibit the secondary reaction of olefins and the sintering of Ni nanoparticles.

[0041] In summary, the catalyst provided by the present invention has a micro-mesoporous composite structure and dehydrogenation-cracking dual functions, realizing the multi-functional regulation of the pore structure, acid properties, and dehydrogenation activity (through metal modification) of the catalyst, showing excellent catalytic performance for n-butane cracking, and solving technical problems such as easy agglomeration and sintering inactivation of metal-loaded molecular sieve catalysts. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] 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 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 be obtained based on these drawings.

[0043] Figure 1 In Test Example 1, for the HZSM-5 prepared in Comparative Example 1, the 0.1% Ni@HZSM-5, 0.5% Ni@HZSM-5, 1% Ni@HZSM-5, and 2% Ni@HZSM-5 prepared in Examples 1 - 4, and the intermediate product 1% NiO / SiO obtained in Example 3 2 XRD patterns.

[0044] Figure 2a In Test Example 2, SEM images of the HZSM-5 prepared in Comparative Example 1.

[0045] Figures 2b - 2e Respectively, in Test Example 2, SEM images of the 0.1% Ni@HZSM-5, 0.5% Ni@HZSM-5, 1% Ni@HZSM-5, and 2% Ni@HZSM-5 prepared in Examples 1 - 4.

[0046] Figure 2f In Test Example 2, SEM images of the intermediate product 1% NiO / SiO obtained in Example 3 2 .

[0047] Figure 3 In Test Example 3, HRTEM images of the 1% Ni@HZSM-5 prepared in Example 3.

[0048] Figures 4a - 4f Graph of the cracking performance of n-butane obtained in the evaluation examples. Detailed implementation manners

[0049] It should be noted that the term "including" and any variations thereof in the description, claims, and 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 not clearly listed or inherent to these processes, methods, products, or devices.

[0050] The "ranges" disclosed in the present invention are given in the form of a lower limit and an upper limit. There may be one or more lower limits, and one or more upper limits respectively. 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 particular parameter, ranges of 60 - 110 and 80 - 120 are also contemplated. Further, 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.

[0051] In the present invention, unless otherwise stated, the numerical range "a - b" represents an abbreviated representation of any combination of real numbers between a and b, where both a and b are 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.

[0052] In the present invention, if there is no special instruction, all embodiments and preferred embodiments mentioned in the present invention can be combined with each other to form a new technical solution.

[0053] In the present invention, if there is no special instruction, all technical features and preferred features mentioned in the present invention can be combined with each other to form a new technical solution.

[0054] In the present invention, if there is no special instruction, all steps mentioned herein can be carried out in sequence or randomly, but preferably in sequence. For example, the method includes steps (a) and (b), which means that the method may include steps (a) and (b) carried out in sequence, or may also include steps (b) and (a) carried out in sequence. 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 may include steps (a), (b), and (c), or may also include steps (a), (c), and (b), or may also include steps (c), (a), and (b), etc.

[0055] In order to make the objectives, technical solutions, and advantages of the present invention more clearly understood, the present invention will be further described in detail below in conjunction with the accompanying drawings and embodiments. The following described embodiments are part of the 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. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts belong to 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 reagents or instruments without indicating the manufacturer, they are all conventional products that can be obtained through commercial purchase. For example, the aqueous solution of tetrapropylammonium hydroxide used in the embodiments is a 25 wt% aqueous solution, purchased from Shanghai Aladdin Biochemical Technology Co., Ltd.; sodium metaaluminate is of analytical grade, purchased from Shanghai Aladdin Biochemical Technology Co., Ltd.; sodium hydroxide is of analytical grade, purchased from Shanghai Macklin Biochemical Technology Co., Ltd.; nickel nitrate hexahydrate is of analytical grade, purchased from Sinopharm Chemical Reagent Co., Ltd.; ammonium chloride is of analytical grade, purchased from Shanghai Macklin Biochemical Technology Co., Ltd.; the purity of n-butane is 99.9%, purchased from Beijing Huatong Jingke Co., Ltd.; air, purchased from Zhuozhou Beiwen Industrial Gas Sales Co., Ltd.; the purity of nitrogen is 99.999%, purchased from Zhuozhou Beiwen Industrial Gas Sales Co., Ltd.; a 5 v% hydrogen-nitrogen mixture gas with a purity of 99.9%, purchased from Beijing Huatong Jingke Co., Ltd.; quartz sand (40-60 mesh), purchased from Sinopharm Chemical Reagent Co., Ltd.

[0056] Example 1

[0057] This example provides a Ni@HZSM-5 catalyst for catalyzing the cracking of n-butane, which is prepared by a preparation method including the following specific steps:

[0058] Step 1): Take 4 g of pretreated SiO 2 and place it in an eggplant-shaped flask, and then gradually add deionized water dropwise thereto while constantly shaking; when SiO 2 reaches the adsorption saturation critical state, stop dropping, and weigh the mass of SiO 2 at this time; calculate its water absorption rate according to the mass of SiO 2 before and after water absorption, measure the water absorption rate three times and take the average value as the average water absorption rate of SiO 2 ; in this example, each gram of SiO 2 absorbs 1.2 g of water.

[0059] Step 2): Calculate the volume of the impregnation solution required for the equal-volume impregnation method according to the average water absorption rate obtained in Step 1), and prepare an impregnation solution that meets the requirements according to the result. The impregnation solution used in this example is a nickel nitrate solution, and its preparation method is as follows:

[0060] Take 0.0198 g of nickel nitrate hexahydrate and dissolve it in 4.7926 g of water to prepare a 0.1 wt% nickel nitrate solution;

[0061] Step 3): Place 4 g of pretreated SiO 2 in a flask, and use the equal-volume impregnation method to evenly drip the 0.1 wt% nickel nitrate solution onto SiO 2 while continuously shaking during the process to make it mix evenly without any remaining impregnation solution; then let it stand for 24 h;

[0062] Step 4): Take out the impregnated product after drying, put it into a muffle furnace, and calcine it at 350 °C for 3 h to obtain 0.1% NiO / SiO 2 ;

[0063] Step 5): Weigh 4.92 g of a 25 wt% aqueous solution of tetrapropylammonium hydroxide and add it to 8.94 g of deionized water, stir at room temperature for 0.5 h until it is fully dissolved; then add 0.12 g of NaOH and stir again for 0.5 h; then add 0.06 g of NaAlO 2 to the solution, stir at room temperature for 1 h; finally add 4 g of 0.1% NiO / SiO 2 and continuously stir for 12 h to make it fully hydrolyze to obtain a gel-like substance;

[0064] Step 6): Place the gel-like substance in a stainless-steel hydrothermal reaction kettle with a polytetrafluoroethylene inner liner, put this stainless-steel hydrothermal reaction kettle into a rotary oven, set the reaction temperature to 100 °C, the rotation speed to 100 r / min, and carry out hydrothermal crystallization for 72 h;

[0065] Step 7): After the reaction is completed, take out the stainless-steel hydrothermal reaction kettle, centrifuge, wash, and dry the obtained solution to get a relatively pure product; then grind the obtained product into powder and calcine it in a muffle furnace at 600 °C for 2 h;

[0066] Step 8): Carry out ion exchange of the product prepared in Step 7) with an ammonium chloride aqueous solution in an oil bath at 90 °C under stirring conditions for 2 h each time, for a total of 3 times;

[0067] Step 9): After drying the ion-exchanged product, calcine it at 600 °C for 2 h to obtain a hydrogen-type molecular sieve, denoted as 0.1% NiO@HZSM-5, and place it in a desiccator for sealed storage;

[0068] Step 10): In a hydrogen-nitrogen mixed gas (with a flow rate of 30 mL / min, 5 v% H 2) 0.1% NiO@HZSM-5 was reduced at a temperature of 600 °C in an atmosphere to produce a Ni@HZSM-5 catalyst for catalyzing the cracking of n-butane, namely 0.1% Ni@HZSM-5.

[0069] Example 2

[0070] This example provides a Ni@HZSM-5 catalyst for catalyzing the cracking of n-butane, which is prepared by a preparation method including the following specific steps:

[0071] Step 1): Take 4 g of pretreated SiO 2 And place it in an eggplant-shaped flask, then slowly add deionized water drop by drop while constantly shaking; when SiO 2 Reaches the adsorption saturation critical state, stop adding drops, and weigh the mass of SiO 2 At this time; calculate its water absorption rate according to the mass of SiO 2 Before and after water absorption, measure the water absorption rate three times and take the average as the average water absorption rate of SiO 2 In this example, each gram of SiO 2 Absorbs 1.2 g of water;

[0072] Step 2): Calculate the volume of the impregnation solution required for the equal-volume impregnation method according to the average water absorption rate obtained in Step 1), and prepare an impregnation solution that meets the requirements according to the result. The impregnation solution used in this example is a nickel nitrate solution, and its preparation method is as follows:

[0073] Take 0.0991 g of nickel nitrate hexahydrate and dissolve it in 4.7632 g of water to prepare a 0.5 wt% nickel nitrate solution;

[0074] Step 3): Place 4 g of pretreated SiO 2 In a flask, and use the equal-volume impregnation method to evenly drop the 0.5 wt% nickel nitrate solution on SiO 2 While constantly shaking to make it mix evenly without remaining impregnation solution; then let it stand for 24 h;

[0075] Step 4): Take out the impregnated product after drying, put it into a muffle furnace, and calcine it at 350 °C for 3 h to obtain 0.5% NiO / SiO 2 ;

[0076] Step 5): Weigh 4.92 g of an aqueous solution of tetrapropylammonium hydroxide with a concentration of 25 wt% and add it to 8.94 g of deionized water, stir at room temperature for 0.5 h until it is fully dissolved; then add 0.12 g of NaOH and stir again for 0.5 h; then add 0.06 g of NaAlO 2Add it to the solution and stir at room temperature for 1 h; finally, add 4 g of 0.5% NiO / SiO 2 And continue to stir for 12 h to fully hydrolyze it to obtain a gel-like substance;

[0077] Step 6): Place the gel-like substance in a stainless-steel hydrothermal reaction kettle with a polytetrafluoroethylene inner liner, put the stainless-steel hydrothermal reaction kettle into a rotary oven, set the reaction temperature to 100 °C, the rotation speed to 100 r / min, and hydrothermally crystallize for 72 h;

[0078] Step 7): After the reaction is completed, take out the stainless-steel hydrothermal reaction kettle, centrifuge, wash, and dry the obtained solution to obtain a relatively pure product; then grind the obtained product into powder and calcine it in a muffle furnace at 600 °C for 2 h;

[0079] Step 8): Exchange ions of the product prepared in Step 7) with an ammonium chloride aqueous solution in an oil bath at 90 °C under stirring conditions for 2 h each time, for a total of 3 times;

[0080] Step 9): After drying the ion-exchanged product, calcine it at 600 °C for 2 h to obtain a hydrogen-type molecular sieve, denoted as 0.5% NiO@HZSM-5, and store it sealed in a desiccator;

[0081] Step 10): Reduce 0.5% NiO@HZSM-5 in an atmosphere of a hydrogen-nitrogen mixture (with a flow rate of 30 mL / min and 5 v% H 2 ) at a temperature of 600 °C to generate a Ni@HZSM-5 catalyst for catalyzing the cracking of n-butane, namely 0.5% Ni@HZSM-5.

[0082] Example 3

[0083] This example provides a Ni@HZSM-5 catalyst for catalyzing the cracking of n-butane, which is prepared by a preparation method including the following specific steps:

[0084] Step 1): Take 4 g of pretreated SiO 2 And place it in an eggplant-shaped flask, then gradually add deionized water dropwise thereto while constantly shaking; when SiO 2 reaches the adsorption saturation critical state, stop dropping, and weigh the mass of SiO 2 at this time; calculate its water absorption rate according to the mass of SiO 2 before and after water absorption, measure the water absorption rate three times and take the average value as the average water absorption rate of SiO 2 ; in this example, each gram of SiO 2 absorbs 1.2 g of water;

[0085] Step 2): Calculate the volume of the impregnation solution required for the equal-volume impregnation method based on the average water absorption rate obtained in Step 1), and prepare an impregnation solution that meets the requirements according to the result. The impregnation solution used in this example is a nickel nitrate solution, and its preparation method is as follows:

[0086] Take 0.1982 g of nickel nitrate hexahydrate and dissolve it in 4.7624 g of water to prepare a 1 wt% nickel nitrate solution;

[0087] Step 3): Place 4 g of pretreated SiO 2 in a flask, and uniformly drip the 1 wt% nickel nitrate solution onto SiO 2 by the equal-volume impregnation method. During this process, continuously shake to make it mix evenly without any remaining impregnation solution; then let it stand for 24 h;

[0088] Step 4): Take out the impregnated product after drying, put it into a muffle furnace, and calcine it at 350 °C for 3 h to obtain 1% NiO / SiO 2 ;

[0089] Step 5): Weigh 4.92 g of an aqueous solution of tetrapropylammonium hydroxide with a concentration of 25 wt% and add it to 8.94 g of deionized water. Stir at room temperature for 0.5 h until it is fully dissolved; then add 0.12 g of NaOH and stir again for 0.5 h; then add 0.06 g of NaAlO 2 to the solution and stir at room temperature for 1 h; finally, add 4 g of 1% NiO / SiO 2 and continuously stir for 12 h to make it fully hydrolyze to obtain a gel-like substance;

[0090] Step 6): Place the gel-like substance in a stainless-steel hydrothermal reaction kettle with a polytetrafluoroethylene inner liner. Place this stainless-steel hydrothermal reaction kettle in a rotary oven, set the reaction temperature to 100 °C, the rotation speed to 100 r / min, and carry out hydrothermal crystallization for 72 h;

[0091] Step 7): After the reaction is completed, take out the stainless-steel hydrothermal reaction kettle, centrifuge, wash, and dry the obtained solution to obtain a relatively pure product; then grind the obtained product into powder and calcine it in a muffle furnace at 600 °C for 2 h;

[0092] Step 8): Carry out ion exchange of the product prepared in Step 7) with an ammonium chloride aqueous solution in an oil bath at 90 °C under stirring conditions for 2 h each time, for a total of 3 times;

[0093] Step 9): After drying the ion-exchanged product, calcine it at 600 °C for 2 h to obtain a hydrogen-type molecular sieve, denoted as 1% NiO@HZSM-5, and place it in a desiccator for sealed storage;

[0094] Step 10): Reduce 1% NiO@HZSM-5 in a hydrogen-nitrogen mixed gas (with a flow rate of 30 mL / min and 5 v% H 2 ) atmosphere at a temperature of 600 °C to generate a Ni@HZSM-5 catalyst for catalyzing n-butane cracking, namely 1% Ni@HZSM-5.

[0095] Example 4

[0096] This example provides a Ni@HZSM-5 catalyst for catalyzing n-butane cracking, which is prepared by a preparation method including the following specific steps:

[0097] Step 1): Take 4 g of pretreated SiO 2 and place it in an eggplant-shaped flask, then gradually add deionized water dropwise while constantly shaking; when SiO 2 reaches the adsorption saturation critical state, stop adding drops and weigh the mass of SiO 2 at this time; calculate its water absorption rate according to the mass of SiO 2 before and after water absorption, measure the water absorption rate three times and take the average as the average water absorption rate of SiO 2 ; in this example, each gram of SiO 2 absorbs 1.2 g of water;

[0098] Step 2): Calculate the volume of the impregnation solution required for the equal-volume impregnation method according to the average water absorption rate obtained in Step 1), and prepare an impregnation solution that meets the requirements according to the result. The impregnation solution used in this example is a nickel nitrate solution, and its preparation method is as follows:

[0099] Take 0.3964 g of nickel nitrate hexahydrate and dissolve it in 4.6528 g of water to prepare a 2 wt% nickel nitrate solution;

[0100] Step 3): Load 4 g of pretreated SiO 2 into a flask, and use the equal-volume impregnation method to evenly drop the 2 wt% nickel nitrate solution on SiO 2 while constantly shaking to make it mix evenly without any remaining impregnation solution; then let it stand for 24 h;

[0101] Step 4): Take out the impregnated product after drying, put it into a muffle furnace, and calcine it at 350 °C for 3 h to obtain 2% NiO / SiO 2 ;

[0102] Step 5): Weigh 4.92 g of an aqueous solution of tetrapropylammonium hydroxide with a concentration of 25 wt% and add it to 8.94 g of deionized water, stir at room temperature for 0.5 h until it is fully dissolved; then add 0.12 g of NaOH and stir again for 0.5 h; then add 0.06 g of NaAlO2 Add it to the solution and stir at room temperature for 1 h; finally, add 4 g of 2% NiO / SiO 2 and continue stirring for 12 h to allow it to hydrolyze fully to obtain a gel-like substance;

[0103] Step 6): Place the gel-like substance in a stainless-steel hydrothermal reactor with a polytetrafluoroethylene inner liner, place the stainless-steel hydrothermal reactor in a rotary oven, set the reaction temperature to 100 °C, the rotation speed to 100 r / min, and carry out hydrothermal crystallization for 72 h;

[0104] Step 7): After the reaction is completed, take out the stainless-steel hydrothermal reactor, centrifuge, wash, and dry the obtained solution to obtain a relatively pure product; then grind the obtained product into powder and calcine it in a muffle furnace at 600 °C for 2 h;

[0105] Step 8): Exchange ions of the product prepared in Step 7) with an ammonium chloride aqueous solution in an oil bath at 90 °C under stirring conditions for 2 h each time, for a total of 3 times;

[0106] Step 9): After drying the ion-exchanged product, calcine it at 600 °C for 2 h to obtain a hydrogen-type molecular sieve, denoted as 2% NiO@HZSM-5, and store it sealed in a desiccator;

[0107] Step 10): Reduce 2% NiO@HZSM-5 in a hydrogen-nitrogen mixed gas (with a flow rate of 30 mL / min and 5 v% H 2 ) atmosphere at a temperature of 600 °C to generate a Ni@HZSM-5 catalyst for catalyzing n-butane cracking, namely 2% Ni@HZSM-5.

[0108] Example 5

[0109] This example provides a Ni@HZSM-5 catalyst for catalyzing n-butane cracking, which is prepared by a preparation method including the following specific steps:

[0110] Step 1): Take 4 g of pretreated SiO 2 and place it in an eggplant-shaped flask, then add deionized water dropwise thereto while constantly shaking; when SiO 2 reaches the adsorption saturation critical state, stop dropping, and weigh the mass of SiO 2 at this time; calculate its water absorption rate according to the mass of SiO 2 before and after water absorption, measure the water absorption rate three times, take the average value, and use it as the average water absorption rate of SiO 2 ; in this example, each gram of SiO 2 absorbs 1.2 g of water;

[0111] Step 2): Calculate the volume of the impregnation solution required for the equal-volume impregnation method based on the average water absorption rate obtained in Step 1), and prepare an impregnation solution that meets the requirements according to the result. The impregnation solution used in this example is nickel chloride solution, and its preparation method is as follows:

[0112] Take 0.0089 g of nickel chloride and dissolve it in 4.7926 g of water to prepare a 0.1 wt% nickel chloride solution;

[0113] Step 3): Place 4 g of pretreated SiO 2 in a flask, and evenly drop 0.1 wt% nickel chloride solution on SiO 2 by the equal-volume impregnation method. During this process, continuously shake to make it mix evenly without any remaining impregnation solution; then let it stand for 12 h;

[0114] Step 4): Take out the impregnated product after drying, put it into a muffle furnace, and calcine it at 600 °C for 6 h to obtain 0.1% NiO / SiO 2 ;

[0115] Step 5): Weigh 4.92 g of 25 wt% tetrapropylammonium hydroxide aqueous solution and add it to 8.94 g of deionized water, stir at room temperature for 0.5 h until it is fully dissolved; then add 0.12 g of NaOH and stir again for 0.5 h; then add 0.06 g of NaAlO 2 to the solution, stir at room temperature for 1 h; finally add 4 g of 0.1% NiO / SiO 2 and continuously stir for 12 h to make it fully hydrolyze to obtain a gel-like substance;

[0116] Step 6): Place the gel-like substance in a stainless-steel hydrothermal reaction kettle with a polytetrafluoroethylene inner liner, put this stainless-steel hydrothermal reaction kettle into a rotary oven, set the reaction temperature to 180 °C, the rotation speed to 100 r / min, and carry out hydrothermal crystallization for 72 h;

[0117] Step 7): After the reaction is completed, take out the stainless-steel hydrothermal reaction kettle, centrifuge, wash, and dry the obtained solution to obtain a relatively pure product; then grind the obtained product into powder and calcine it in a muffle furnace at 450 °C for 2 h;

[0118] Step 8): Carry out ion exchange on the product prepared in Step 7) with ammonium chloride aqueous solution in an oil bath at 90 °C under stirring conditions for 2 h each time, for a total of 3 times;

[0119] Step 9): After drying the ion-exchanged product, calcine it at 450 °C for 1 h to obtain a hydrogen-type molecular sieve, denoted as 0.1% NiO@HZSM-5, and store it sealed in a desiccator;

[0120] Step 10): Reduce 0.1% NiO@HZSM-5 in an atmosphere of a hydrogen-nitrogen mixture (with a flow rate of 30 mL / min and 5 v% H 2 ) at a temperature of 450 °C to generate a Ni@HZSM-5 catalyst for catalyzing n-butane cracking, denoted as C5-0.1% Ni@HZSM-5.

[0121] Example 6

[0122] This example provides a Ni@HZSM-5 catalyst for catalyzing n-butane cracking, which is prepared by a preparation method including the following specific steps:

[0123] Step 1): Take 4 g of pretreated SiO 2 and place it in an eggplant-shaped flask, then slowly add deionized water drop by drop while constantly shaking; when SiO 2 reaches the adsorption saturation critical state, stop adding drops, and weigh the mass of SiO 2 at this time; calculate its water absorption rate according to the mass of SiO 2 before and after water absorption, measure the water absorption rate three times and take the average as the average water absorption rate of SiO 2 ; in this example, each gram of SiO 2 absorbs 1.2 g of water.

[0124] Step 2): Calculate the volume of the impregnation solution required for the equal-volume impregnation method according to the average water absorption rate obtained in Step 1), and prepare an impregnation solution that meets the requirements according to the result. The impregnation solution used in this example is a nickel sulfate solution, and its preparation method is as follows:

[0125] Take 0.0895 g of nickel sulfate hexahydrate and dissolve it in 4.7632 g of water to prepare a 0.5 wt% nickel nitrate solution;

[0126] Step 3): Load 4 g of pretreated SiO 2 into a flask, and use the equal-volume impregnation method to evenly drip the 0.5 wt% nickel sulfate solution onto SiO 2 while constantly shaking to make it mix evenly without any remaining impregnation solution; then let it stand for 48 h;

[0127] Step 4): Take out the impregnated product after drying, put it into a muffle furnace, and calcine it at 350 °C for 1 h to obtain 0.5% NiO / SiO 2 ;

[0128] Step 5): Weigh 4.92 g of an aqueous solution of tetrapropylammonium hydroxide with a concentration of 25 wt% and add it to 8.94 g of deionized water. Stir at room temperature for 0.5 h until it is fully dissolved; then add 0.12 g of NaOH and stir again for 0.5 h; then add 0.06 g of NaAlO 2 to the solution and stir at room temperature for 1 h; finally, add 4 g of 0.5% NiO / SiO 2 and continuously stir for 12 h to allow it to fully hydrolyze to obtain a gel-like substance;

[0129] Step 6): Place the gel-like substance in a stainless-steel hydrothermal reaction kettle with a polytetrafluoroethylene inner liner. Place this stainless-steel hydrothermal reaction kettle in a rotary oven, set the reaction temperature to 100 °C, the rotation speed to 100 r / min, and carry out hydrothermal crystallization for 12 h;

[0130] Step 7): After the reaction is completed, take out the stainless-steel hydrothermal reaction kettle, centrifuge, wash, and dry the obtained solution to obtain a relatively pure product; then grind the obtained product into powder and calcine it in a muffle furnace at 700 °C for 8 h;

[0131] Step 8): Exchange the ions of the product prepared in Step 7 with an aqueous ammonium chloride solution in an oil bath at 90 °C under stirring conditions for 2 h each time, for a total of 3 times;

[0132] Step 9): After drying the ion-exchanged product, calcine it at 700 °C for 1 h to obtain a hydrogen-type molecular sieve, denoted as 0.5% NiO@HZSM-5, and store it sealed in a desiccator;

[0133] Step 10): Reduce 0.5% NiO@HZSM-5 in an atmosphere of a hydrogen-nitrogen mixture (with a flow rate of 30 mL / min and 5 v% H 2 ) at a temperature of 650 °C to generate a Ni@HZSM-5 catalyst for catalyzing the cracking of n-butane, denoted as C6-0.5% Ni@HZSM-5.

[0134] Comparative Example 1

[0135] This comparative example provides an HZSM-5 molecular sieve catalyst, which is prepared by a preparation method including the following specific steps:

[0136] Step 1): Weigh 4.92 g of an aqueous solution of tetrapropylammonium hydroxide with a concentration of 25 wt% and add it to 8.94 g of deionized water. Stir at room temperature for 0.5 h until it is fully dissolved; then add 0.12 g of NaOH and stir again for 0.5 h; then add 0.06 g of NaAlO 2 to the solution and stir at room temperature for 1 h; finally, add 4 g of SiO 2Stir continuously for 12 h to fully hydrolyze it and obtain a gel-like substance;

[0137] Step 2): Place the gel-like substance in a stainless-steel hydrothermal reaction kettle with a PTFE inner liner, put the stainless-steel hydrothermal reaction kettle into a rotary oven, set the reaction temperature to 100 °C, and set an appropriate rotation speed, and perform hydrothermal crystallization for 72 h;

[0138] Step 3): After the reaction is completed, take out the stainless-steel hydrothermal reaction kettle, centrifuge, wash, and dry the obtained solution to obtain a relatively pure product; then grind the obtained product into powder and calcine it in a muffle furnace at 600 °C for 2 h;

[0139] Step 4): Exchange ions of the product prepared in Step 3) with an ammonium chloride aqueous solution in an oil bath at 90 °C under stirring conditions for 2 h each time, for a total of 3 times;

[0140] Step 5): After drying the ion-exchanged product, calcine it at 600 °C for 2 h to obtain a hydrogen-type molecular sieve, denoted as HZSM-5, and store it sealed in a desiccator.

[0141] Comparative Example 2

[0142] This comparative example provides a Ni / HZSM-5 catalyst for catalyzing n-butane cracking, which is prepared by a preparation method including the following specific steps:

[0143] Step 1): Take 0.1982 g of nickel nitrate hexahydrate and dissolve it in 4.7624 g of water to prepare a 1 wt% nickel nitrate solution;

[0144] Step 2): Take 4 g of the HZSM-5 molecular sieve catalyst prepared in Comparative Example 1 and place it in a flask. Using the equal-volume impregnation method, evenly drop the 1 wt% nickel nitrate solution on the HZSM-5 molecular sieve, and continuously oscillate during this period to make it mix evenly without any remaining impregnation solution; then let it stand for 24 h;

[0145] Step 3): Take out the product obtained after impregnation after drying it, and put it into a muffle furnace and calcine it at 350 °C for 3 h to obtain 1% NiO / HZSM-5;

[0146] Step 4): Reduce 1% NiO / HZSM-5 in a hydrogen-nitrogen mixed gas (with a flow rate of 30 mL / min and 5 v% H 2 ) atmosphere at a temperature of 550 °C to generate a Ni / HZSM-5 catalyst for catalyzing n-butane cracking, that is, 1% Ni / HZSM-5. In 1% Ni / HZSM-5, most of the nickel nanoparticles are loaded on the surface of the HZSM-5 molecular sieve and cannot be embedded in the pores or crystal lattices of the HZSM-5 molecular sieve.

[0147] Test Example 1

[0148] In this test example, the HZSM-5 prepared in Comparative Example 1, 0.1% Ni@HZSM-5, 0.5% Ni@HZSM-5, 1% Ni@HZSM-5 and 2% Ni@HZSM-5 prepared in Examples 1-4, and the intermediate product 1% NiO / SiO obtained in Example 3 were respectively 2 subjected to XRD analysis, and the obtained XRD patterns are as Figure 1 shown. As can be seen from Figure 1 , characteristic diffraction peaks belonging to the typical MFI structure (PDF#44-0003) appeared in both HZSM-5 and Ni@HZSM-5 molecular sieves at 2θ = 7.94°, 8.80°, 23.10°, 23.42° and 23.98°. At the same time, as can be seen from Figure 1 , compared with the pure HZSM-5 molecular sieve, the diffraction peak intensity of Ni@HZSM-5 after introducing metal Ni decreased in the range of 8-10°, indicating that the Ni metal modification process damaged the HZSM-5 structure to a certain extent. For Ni@HZSM-5 molecular sieves with different Ni contents, no NiO diffraction peak was found in their XRD patterns, indicating that the amount of introduced metal Ni was low or evenly dispersed in the HZSM-5 molecular sieve support. As can be seen from Figure 1 , a relatively broad scattering peak appeared at about 2θ = 22° in the 1% NiO / SiO 2 sample, which was caused by the scattering of amorphous SiO 2 , and no characteristic peak of NiO appeared, indicating that the NiO loading was low and NiO was evenly distributed on the surface of SiO 2 .

[0149] Test Example 2

[0150] In this test example, the HZSM-5 prepared in Comparative Example 1, 0.1% Ni@HZSM-5, 0.5% Ni@HZSM-5, 1% Ni@HZSM-5 and 2% Ni@HZSM-5 prepared in Examples 1-4, and the intermediate product 1% NiO / SiO 2 were subjected to SEM analysis, and the obtained SEM images are respectively as Figures 2a - 2f shown. As can be seen from Figure 2a , the surface of the HZSM-5 molecular sieve particles is smooth, the morphology of the molecular sieve is in a "spherical" structure, and the particle size distribution is relatively uniform, with an average particle size of 2.32 μm. Figures 2b - 2e are SEM images of Ni@HZSM-5 molecular sieves with different Ni contents. As can be seen from them, the morphology basically did not change after loading Ni metal, and with the increase of Ni loading, the particle size of the catalyst changed insignificantly.Figure 2f is the SEM image of the intermediate product 1% NiO / SiO obtained in Example 3 2 From which it can be seen that it is a smooth spherical shape with an average particle size of 22.19 μm.

[0151] Test Example 3

[0152] This test example conducts HRTEM analysis on 1% Ni@HZSM-5 prepared in Example 3, and the obtained HRTEM image is as Figure 3 shown. From Figure 3 it can be seen that in 1% Ni@HZSM-5, nickel is uniformly embedded in the HZSM-5 molecular sieve structure, and only a small part of Ni is not successfully encapsulated, which is consistent with the XRD characterization results as Figure 1 shown.

[0153] Evaluation Example 1

[0154] This evaluation example uses a fixed-bed micro-reactor to evaluate the performance of the fixed-bed catalytic cracking (n-butane catalytic cracking) of HZSM-5 prepared in Comparative Example 1, D-1% Ni@HZSM-5 prepared in Comparative Example 2, 0.1% Ni@HZSM-5, 0.5% Ni@HZSM-5, 1% Ni@HZSM-5, and 2% Ni@HZSM-5 prepared in Examples 1 - 4, specifically including:

[0155] The catalyst dosage is 200 mg, and the quartz sand dosage is 2 g. Before starting the reaction, it is heated from room temperature to 550 °C in an N 2 atmosphere at a flow rate of 30 mL / min to blow out all impurities. Each of the above catalysts is purged for 30 min in an air atmosphere at 30 mL / min, and then purged for 5 min in an N 2 atmosphere. Then, it is pre-reduced for 30 min in a hydrogen-nitrogen mixed gas (5 v% H 2 ) atmosphere at 30 mL / min, and finally purged for 5 min with an N 2 atmosphere at 36 mL / min.

[0156] The n-butane feed flow rate is 4 mL / min, and the nitrogen feed flow rate is 36 mL / min. They are mixed and enter the reactor. The reactor is heated to 600 °C at a heating rate of 10 °C / min, and the system pressure is 101 kPa. The product analysis is carried out using a gas chromatograph analyzer, and on-line analysis is performed using an Al 2 O 3 type capillary column. The injector temperature is 180 °C, the detector is a flame ionization detector (FID), the detector temperature is 120 °C, and the area normalization method is used for quantification.

[0157] The n-butane cracking performance graph obtained in this evaluation example is asFigures 4a - 4f As shown. From Figures 4a - 4f It can be seen that compared with the pure HZSM-5 and Ni / ZSM-5 catalysts, the catalytic cracking activity of the Ni@HZSM-5 catalyst with a core-shell structure provided in the embodiments of the present invention is significantly improved, the ethylene selectivity is significantly increased, and the selectivity of other light olefins decreases slightly. The Ni@ZSM-5 core-shell structure can not only provide a large number of Ni metal center and Lewis center interfaces, enhance their synergistic effect, but also inhibit the secondary reaction of olefins; in addition, it can effectively inhibit the sintering of Ni nanoparticles.

[0158] From Figures 4a - 4f It can also be seen that with the increase of the Ni loading amount, the conversion rate of n-butane and the ethylene selectivity show a trend of first increasing and then decreasing. When the Ni loading amount is 1%, the catalyst achieves the best activity.

[0159] As described above, only the specific embodiments of the present invention are given, and the scope of the invention implementation cannot be limited by them. Therefore, the replacement of equivalent components or the equivalent changes and modifications made according to the scope of the present invention patent protection 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 Ni@HZSM-5 catalyst, It is characterized in that The catalyst comprises HZSM-5 molecular sieve and nickel nanoparticles. The nickel nanoparticles are embedded in the pores or crystals of the HZSM-5 molecular sieve, or are loaded on the outer surface of the HZSM-5 molecular sieve.

2. The catalyst according to claim 1, It is characterized in that Based on the total weight of the HZSM-5 molecular sieve being 100%, the content of the nickel nanoparticles is 0.1-2wt%.

3. The method for preparing the Ni@HZSM-5 catalyst according to claim 1 or 2, It is characterized in that The preparation method comprises: Step (1): Use the equal volume impregnation method to evenly drop the aqueous solution of nickel salt on the SiO 2 After being dried and calcined, NiO / SiO 2 ; Step (2): Prepare a solution containing a template, an alkali and an aluminum source, and mix NiO / SiO 2 adding into the solution and fully hydrolyzing it to obtain a gel-like substance; Step (3): subjecting the gel-like substance to hydrothermal crystallization, and then calcining the hydrothermal crystallization product; Step (4): subjecting the calcined product of step (3) to ion exchange with an aqueous ammonium salt solution; Step (5): drying and calcining the product after ion exchange in step (4) to obtain NiO@HZSM-5; Step (6): reducing NiO@HZSM-5 in a hydrogen-nitrogen mixed gas atmosphere to obtain a Ni@HZSM-5 catalyst.

4. The preparation method according to claim 3, It is characterized in that In step (1), the nickel salt includes one or a combination of nickel chloride, nickel nitrate and nickel sulfate.

5. The preparation method according to claim 3 or 4, It is characterized in that In step (1), the calcination is performed at 350-600° C. for 1-6 hours.

6. The preparation method according to claim 3, It is characterized in that In step (2), the template, alkali, aluminum source and NiO / SiO 2 The mass ratio is 1-6:0.1-2:0.01-2:1-6.

7. The preparation method according to claim 3 or 6, It is characterized in that In step (2), the template comprises tetrapropylammonium hydroxide; The base includes sodium hydroxide; The aluminum source includes one or a combination of aluminum isopropoxide, aluminum nitrate, aluminum sulfate and sodium metaaluminate.

8. The preparation method according to claim 3, It is characterized in that In step (3), the hydrothermal crystallization temperature is 100-200° C. and the time is 12-72 hours.

9. The preparation method according to claim 3 or 8, It is characterized in that In step (3), the calcination is performed at 450-700° C. for 2-8 hours.

10. The preparation method according to claim 3, It is characterized in that In step (4), the ion exchange is carried out at a temperature of 50-90° C. for 1-3 times, each time for 1-3 hours.

11. The preparation method according to claim 3 or 10, It is characterized in that In step (5), the calcination is performed at 450-700° C. for 1-3 h.

12. The preparation method according to claim 3, It is characterized in that In step (6), the reduction temperature is 450-650° C., the flow rate of the hydrogen-nitrogen mixed gas is 10-50 mL / min, and the content of hydrogen is 1-50% based on the total volume of the hydrogen-nitrogen mixed gas as 100%.

13. Use of the Ni@HZSM-5 catalyst according to claim 1 or 2 in catalytic cracking of n-butane to produce small molecule olefins.

14. The use according to claim 13, It is characterized in that The temperature of the catalytic cracking is 450-650°C and the pressure is 0.1-2.5MPa.

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