Propane dehydrogenation catalyst as well as preparation method and application thereof

Abstract

The invention provides a propane dehydrogenation catalyst and a preparation method and application thereof.The propane dehydrogenation catalyst comprises a hydrogen type mesoporous and microporous composite hierarchical pore molecular sieve carrier and a cobalt active component, a part of the cobalt active component is loaded on the surface of the hydrogen type mesoporous and microporous composite hierarchical pore molecular sieve carrier in the form of CoO nanoparticles, and the cobalt active component is loaded on the surface of the cobalt active component in the form of CoO nanoparticles. The other part of the cobalt active component enters a framework of the hydrogen type mesoporous and microporous composite hierarchical pore molecular sieve carrier in a form of forming chemical bonds and forms a Co < 2 + >-O-Si structure; the total weight of the hydrogen type mesoporous and microporous composite hierarchical pore molecular sieve carrier is 100%, and the content of the cobalt active component is 0.1-7wt% in terms of cobalt element. The propane dehydrogenation catalyst provided by the invention has excellent propane dehydrogenation reaction catalysis activity and stability.

Description

Technical Field

[0001] The invention relates to a propane dehydrogenation catalyst and a preparation method and application thereof, belonging to the technical field of petrochemical industry. Background Art

[0002] As the basic raw material for many organic chemical products, propylene is widely used in various fields such as rubber, medicine and textiles. Propane dehydrogenation to propylene technology (PDH) has the advantages of short process flow, high propylene selectivity, environmental friendliness and low overall cost, and has received continuous attention and development. Propane dehydrogenation is a strong endothermic reaction and needs to be carried out under high temperature conditions. However, high reaction temperatures can easily cause deep dehydrogenation and cracking of propylene, which not only reduces the propylene yield but also causes carbon deposition and deactivation of the catalyst. Therefore, it is necessary to develop a propane dehydrogenation catalyst with high activity, high selectivity and strong stability.

[0003] Currently, the propane dehydrogenation catalysts used in industry are mainly Pt and Cr catalysts. However, the precious metal Pt is expensive, and the high price of Cr is toxic to the human body and the environment. The transition metal Co is abundant and non-toxic. Studies have found that the molecular sieve catalyst synthesized with metal Co as the active phase has good propane dehydrogenation reaction activity. The tetracoordinated Co 2+ It can effectively activate the propane CH bond to generate propylene and hydrogen. However, the catalyst loaded with Co by the impregnation method using traditional microporous, mesoporous or macroporous molecular sieves as carriers faces problems such as unclear catalytic active sites, poor metal dispersion, and easy sintering and carbon deposition leading to rapid catalyst deactivation.

[0004] As the basis of catalyst composition, the carrier has a crucial influence on catalytic activity and stability. The components of traditional molecular sieves are relatively simple: the intrinsic pores of microporous molecular sieves are narrow, which limits the substrate transmission and easily causes carbon deposition and deactivation of the catalyst; it is difficult to anchor the active components in mesoporous or macroporous molecular sieves, and it is impossible to avoid sintering of active sites. At present, a large number of studies are focused on the method of introducing mesopores into microporous molecular sieve crystals to prepare multi-level pore molecular sieves with at least two pores (intrinsic micropore channels and mesopores). Compared with traditional molecular sieves, multi-level pore molecular sieves can not only improve the carbon holding capacity of the carrier due to their mesopores, but also the multi-level pores are conducive to the mass transfer of substrates and products, thereby inhibiting carbon deposition, effectively improving the activity and stability of propane dehydrogenation catalysts.

[0005] The preparation of isolated stable Co-based active center catalysts has always been a research difficulty. Metal-loaded molecular sieves prepared by traditional supporting methods are prone to uneven metal nanoparticle size, poor dispersibility, unclear active sites, and ultimately poor catalytic performance. At present, the main method in this field is to improve the dispersibility of Co by adding metal additives, but there are still problems such as poor propane conversion and propylene selectivity, poor catalytic activity or poor catalyst stability. Molecular sieve encapsulated metal catalysts prepared with metal chelates as raw materials can implant Co into the molecular sieve skeleton and use the internal microporous structure of the molecular sieve to effectively inhibit the aggregation of metal particles, thereby improving its catalytic reaction performance. However, there are defects such as long hydrothermal time, high hydrothermal temperature, large amount of template agent, and burning out of the template agent will cause environmental pollution during the in-situ synthesis of the catalyst.

[0006] Therefore, providing a novel propane dehydrogenation catalyst and a preparation method and application thereof has become a technical problem that needs to be solved urgently in the art. Summary of the invention

[0007] In order to solve the above-mentioned shortcomings and deficiencies, an object of the present invention is to provide a propane dehydrogenation catalyst.

[0008] Another object of the present invention is to provide a method for preparing the above-mentioned propane dehydrogenation catalyst.

[0009] Another object of the present invention is to provide the use of the above propane dehydrogenation catalyst in the dehydrogenation of propane to propylene.

[0010] In order to achieve the above objectives, on the one hand, the present invention provides a propane dehydrogenation catalyst, wherein the propane dehydrogenation catalyst comprises a hydrogen-type mesoporous composite multi-level porous molecular sieve carrier and a cobalt active component, wherein a portion of the cobalt active component is loaded on the surface of the hydrogen-type mesoporous composite multi-level porous molecular sieve carrier in the form of CoO nanoparticles, and another portion of the cobalt active component enters the skeleton of the hydrogen-type mesoporous composite multi-level porous molecular sieve carrier in the form of forming a chemical bond and forms CoO nanoparticles. 2+ -O-Si structure;

[0011] Based on the total weight of the hydrogen-type mesoporous and microporous composite multi-level porous molecular sieve carrier being 100%, the content of the cobalt active component in terms of cobalt element is 0.1-7wt%.

[0012] As a specific embodiment of the propane dehydrogenation catalyst described above in the present invention, the molar ratio of divalent cobalt to trivalent cobalt in the propane dehydrogenation catalyst is greater than 3.

[0013] On the other hand, the present invention provides a method for preparing the above-mentioned propane dehydrogenation catalyst, wherein the preparation method comprises the following steps:

[0014] Step (1): using an alkali treatment solution to treat pure silicon molecular sieve Silicalite-1, and then subjecting the alkali treatment product to ion exchange with an ammonium salt, and then drying and calcining the ion exchange product to obtain a hydrogen-type mesoporous and microporous composite multi-level pore molecular sieve;

[0015] Step (2): fully dissolving the cobalt salt and the hydrogen-type mesoporous composite multi-level porous molecular sieve in an ammonia solution, and adjusting the pH value of the system so that the cobalt ions are adsorbed on the surface of the hydrogen-type mesoporous composite multi-level porous molecular sieve and enter the cavities of its skeleton, and then drying and calcining the obtained solid precipitate to obtain the propane dehydrogenation catalyst.

[0016] In the preparation method described above, pure silicon molecular sieve Silicalite-1 can be prepared by conventional methods. For example, in some embodiments of the present invention, pure silicon molecular sieve Silicalite-1 can be prepared by hydrothermal crystallization method. The preparation method includes the following specific steps:

[0017] The silicon source, the structure directing agent and water are uniformly mixed to obtain a mixed solution, the mixed solution is hydrothermally crystallized, and the crystallized product is washed, dried and calcined to obtain the pure silicon molecular sieve Silicalite-1.

[0018] The silicon source includes one or a combination of tetraethyl orthosilicate, solid silica gel, white carbon black and silica sol, and the structure directing agent includes one or a combination of tetrapropylammonium salts and / or tetraethylammonium salts such as tetrapropylammonium hydroxide (TPAOH), tetrapropylammonium chloride, tetraethylammonium hydroxide and tetraethylammonium chloride.

[0019] The molar ratio of the silicon source, the structure directing agent and water calculated as SiO2 is 1:(0.1-0.5):(5-50).

[0020] The hydrothermal crystallization temperature is 100-190° C., preferably 170° C., and the time is 24-96 h, preferably 72 h.

[0021] As a specific embodiment of the preparation method described above in the present invention, the alkaline treatment solution includes a sodium hydroxide aqueous solution, a tetrapropylammonium hydroxide aqueous solution or a tetraethylammonium hydroxide aqueous solution.

[0022] As a specific embodiment of the preparation method described above, the concentration of the alkaline treatment solution is 0.01-1 mol / L, and the mass ratio of pure silicon molecular sieve Silicalite-1 to the alkaline treatment solution is 1:5-15.

[0023] As a specific embodiment of the above preparation method of the present invention, when the alkaline treatment solution is a sodium hydroxide aqueous solution, its concentration is 0.01-0.3 mol / L.

[0024] As a specific embodiment of the above preparation method of the present invention, the temperature of the alkali treatment is room temperature-100°C, and the time is 1-6h.

[0025] As a specific embodiment of the preparation method described above, step (1) further comprises washing the alkali-treated product to neutrality and then exchanging ions between the alkali-treated product and an ammonium salt. The washing liquid used in the washing may be, for example, deionized water.

[0026] As a specific embodiment of the preparation method described above, in step (1), the temperature of ion exchange is not higher than 100° C. In a preferred embodiment of the present invention, ion exchange can be repeated multiple times to make the exchange more complete, and the ammonium salt used in ion exchange can be, for example, ammonium chloride.

[0027] As a specific embodiment of the preparation method described above, in step (1) and step (2), the drying temperature is 60-120° C. The present invention does not make specific requirements on the drying time, which can be reasonably determined according to the actual operation needs on site, as long as the purpose of drying the target product can be achieved.

[0028] As a specific embodiment of the preparation method described above of the present invention, in step (1) and step (2), the calcination is carried out by heating the temperature from room temperature to 500-600°C at a heating rate of 0.5-5°C / min and keeping the temperature for 2-8h.

[0029] As a specific embodiment of the preparation method described above of the present invention, in step (2), the pH value of the system is adjusted to 10.5-11.5.

[0030] As a specific embodiment of the preparation method described above in the present invention, step (2) specifically includes first dissolving the cobalt salt in an ammonia solution and then adjusting the pH value of the system to 10.5-11.5, then adding a hydrogen-type mesoporous composite multi-level pore molecular sieve and allowing it to fully dissolve and then adjusting the pH value of the system to 10.5-11.5 again, and then drying and calcining the obtained solid precipitate to obtain the propane dehydrogenation catalyst.

[0031] In some embodiments of the present invention, in step (2), the pH value of the system can be adjusted to 10.5-11.5 by adding ammonia water to the system.

[0032] As a specific embodiment of the preparation method described above, the cobalt salt includes one or a combination of cobalt nitrate hexahydrate, cobalt chloride hexahydrate, cobalt acetate, cobalt carbonyl, Co-EDTA complex and cobalt acetylacetonate complex.

[0033] As a specific embodiment of the above preparation method of the present invention, the mass concentration of the ammonia solution is 1-2%.

[0034] As a specific embodiment of the preparation method described above, step (2) further comprises centrifuging the solution obtained after adjusting the pH value of the system to 10.5-11.5, and then drying and calcining the solid precipitate obtained after the centrifugation.

[0035] The present invention first uses an alkali treatment liquid to perform alkali treatment and desiliconization on pure silicon molecular sieve Silicalite-1, and obtains a hydrogen-type mesoporous composite multi-level pore molecular sieve by adjusting the alkali treatment conditions, including the type of alkali, the treatment time, etc., and at the same time, a large number of hydroxyl defects are generated in the molecular sieve. Then, a strong electrostatic adsorption method is used to prepare a propane dehydrogenation catalyst. During the preparation process, the pH value of the system is accurately controlled to generate a strong electrostatic adsorption effect between the charged metal precursor ions and the molecular sieve carrier with opposite electrical properties, thereby forming a stable structure, preventing metal aggregation, forming highly dispersed nanoparticles, and realizing that Co enters the molecular sieve framework to form Co 2+ -O-Si structure.

[0036] In another aspect, the present invention also provides use of the above-mentioned propane dehydrogenation catalyst in the dehydrogenation of propane to produce propylene.

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

[0038] (1) The present invention uses an alkali treatment solution to treat pure silicon molecular sieve Silicalite-1 to obtain a hydrogen-type mesoporous composite multi-level pore molecular sieve. Compared with the traditional single-pore molecular sieve carrier, the multi-level pore structure in the hydrogen-type mesoporous composite multi-level pore molecular sieve is conducive to the mass transfer between the substrate and the product, thereby inhibiting the generation of carbon deposition, and at the same time, it can also improve the carbon holding capacity of the carrier, which is conducive to improving the stability of the catalyst. Specifically, the catalyst was tested for stability for 12 hours, and the deactivation rate was only 0.033h -1 , compared with the Co-based catalysts reported in existing literature (J.Am.Chem.Soc.2022,144(27),12127-12137., J.Catal.2015,322,24-37. and ACS Applied Materials&Interfaces,2023,15(11):14250-14260., etc.), it shows better stability.

[0039] (2) The present invention uses a hydrogen-type mesoporous composite multi-level porous molecular sieve as a carrier and adopts a strong electrostatic adsorption method to prepare a propane dehydrogenation catalyst. The propane dehydrogenation catalyst has the advantages of highly dispersed metals, small nanoparticles and high stability, while the active metal dispersion of the catalyst synthesized by the traditional impregnation method is low and it is easy to agglomerate and deactivate. Compared with the in-situ hydrothermal synthesis, the strong electrostatic adsorption method used in the present invention does not require a high temperature and high pressure environment, thereby reducing environmental pollution and lowering production costs.

[0040] (3) The propane dehydrogenation catalyst provided by the present invention uses a hydrogen-type mesoporous composite multi-level porous molecular sieve as a carrier, a portion of the cobalt active component is loaded on the surface of the hydrogen-type mesoporous composite multi-level porous molecular sieve carrier in the form of CoO nanoparticles, and another portion of the cobalt active component enters the skeleton of the hydrogen-type mesoporous composite multi-level porous molecular sieve carrier in the form of forming chemical bonds and forms CoO nanoparticles. 2+ -O-Si structure, that is, the active site of the propane dehydrogenation catalyst is a four-coordinated Co 2+ The active sites of the catalyst prepared by impregnating cobalt salt with pure silicon molecular sieve Silicalite-1 as the carrier are Co3O4 sites. This is because: 1) the surface of the hydrogen-type mesoporous composite multi-level porous molecular sieve carrier prepared after alkali treatment has a large number of defect sites, which can well anchor Co species and improve the interaction between the carrier and the metal component, thereby improving the dispersion of Co; 2) the skeleton of the hydrogen-type mesoporous composite multi-level porous molecular sieve carrier prepared after alkali treatment will form holes. When the catalyst is prepared by strong electrostatic adsorption method, Co atoms are successfully chemically bonded to the molecular sieve framework to form a four-coordinated Co 2+ ; However, the surface defect sites and cavities in the framework of pure silicon molecular sieve Silicalite-1 that has not been treated with alkali are relatively few, so the Co species loaded on the surface of the carrier are unevenly dispersed, the particle size is relatively large, and only a small amount of Co enters the molecular sieve framework, and mainly exists on the surface of the molecular sieve in the form of Co3O4. Compared with the Co3O4 sites produced by impregnation with pure silicon molecular sieve Silicalite-1 as a carrier, the catalyst provided by the present invention has four-coordinated Co 2+ The active sites make it more efficient in propane dehydrogenation activity, and the propane conversion rate can be increased by 40% under the same reaction conditions.

[0041] In summary, the propane dehydrogenation catalyst provided by the present invention has excellent catalytic propane dehydrogenation reaction activity and stability. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0043] Figure 1a This is the scanning electron microscope image of S-1.

[0044] Figure 1b This is a scanning electron microscope image of SN-0.05.

[0045] Figure 1c This is the scanning electron microscope image of 0.5Co / S1.

[0046] Figure 1d This is the scanning electron microscope image of 0.5Co / SN-0.05.

[0047] Figure 1e Transmission electron microscope image of 0.5Co / SN-0.05

[0048] Figure 1f-1h This is the elemental surface scan of 0.5Co / SN-0.05.

[0049] Figure 1i-1k This is the elemental surface scan of 0.5Co / S1.

[0050] Figure 2 X-ray diffraction (XRD) patterns of S-1, SN-0.05, 0.5Co / S1 and 0.5Co / SN-0.05.

[0051] Figure 3 These are the N2 physical adsorption-desorption isotherms of S-1, SN-0.05, 0.5Co / S1 and 0.5Co / SN-0.05.

[0052] Figure 4 These are the Raman spectra of 0.5Co / S1 and 0.5Co / SN-0.05.

[0053] Figure 5 X-ray photoelectron spectra of 0.5Co / S1 and 0.5Co / SN-0.05.

[0054] Figure 6 This is the performance diagram of propane dehydrogenation reaction catalyzed by 0.5Co / S1 and 0.5Co / SN-0.05 catalysts.

[0055] Figure 7 This is a stability test diagram of propane dehydrogenation reaction catalyzed by 0.5Co / SN-0.05 catalyst.

[0056] Figure 8 This is a regeneration test diagram of propane dehydrogenation reaction catalyzed by 0.5Co / SN-0.05 catalyst. DETAILED DESCRIPTION

[0057] It should be noted that the term "comprises" and any variations thereof in the specification and claims of the present invention and the above-mentioned drawings are intended to cover non-exclusive inclusions. For example, a process, method, system, product or device that includes a series of steps or units is not necessarily limited to those steps or units clearly listed, but may include other steps or units that are not clearly listed or inherent to these processes, methods, products or devices.

[0058] "Scope" disclosed in the present invention is given in the form of lower limit and upper limit. It can 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, i.e. any lower limit can be combined with any upper limit to form a range. For example, for a specific parameter, a range of 60-120 and 80-110 is listed, and it is understood that a range of 60-110 and 80-120 is also expected. 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 can all be expected: 1-3, 1-4, 1-5, 2-3, 2-4 and 2-5.

[0059] In the present invention, unless otherwise specified, the numerical range "ab" represents an abbreviation of any real number combination between a and b, where a and b are real numbers. For example, the numerical range "0-5" means that all real numbers between "0-5" have been listed in the present invention, and "0-5" is just an abbreviation of these numerical combinations.

[0060] In the present invention, unless otherwise specified, all embodiments and preferred embodiments mentioned in the present invention can be combined with each other to form a new technical solution.

[0061] In the present invention, unless otherwise specified, all technical features and preferred features mentioned in the present invention can be combined with each other to form a new technical solution.

[0062] In the present invention, unless otherwise specified, all steps mentioned herein may be performed sequentially or randomly, but are preferably performed sequentially. For example, the method includes steps (a) and (b), which means that the method may include steps (a) and (b) performed sequentially, or may include steps (b) and (a) performed sequentially. For example, the method may further include step (c), which means that step (c) may be added to the method in any order, for example, the method may include steps (a), (b) and (c), or may include steps (a), (c) and (b), or may include steps (c), (a) and (b), etc.

[0063] In order to make the purpose, technical scheme and advantages of the present invention clearer, the present invention is further described in detail below in conjunction with the attached table, drawings and examples. 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 regarded as limiting the scope of the present invention. Based on the embodiments in the present invention, all other embodiments obtained by ordinary technicians in the field without making creative work are within the scope of protection of the present invention. If the specific conditions are not specified in the embodiments, they are carried out according to the normal conditions or the conditions recommended by the manufacturer. If the manufacturer is not specified in the reagents or instruments used, they are all conventional products that can be purchased commercially.

[0064] Example 1

[0065] This embodiment provides a propane dehydrogenation catalyst, which is prepared by a preparation method comprising the following specific steps:

[0066] Preparation of pure silicon molecular sieve Silicalite-1:

[0067] Step 1: Weigh 22.5 g of deionized water and 19.5 g of TPAOH (25 wt%) and mix the two, then stir at a temperature of 50° C. and a rotation speed of 500 r / min for 10 min to mix the two uniformly to obtain a mixed solution;

[0068] Step 2: Weigh 12.5 g of TEOS and slowly add it to the above mixed solution, then stir at 50° C. for 6 h to obtain a mixture;

[0069] Step 3: The mixture was transferred into a 100 ml autoclave, and the autoclave was placed in an oven for hydrothermal crystallization, wherein the hydrothermal crystallization temperature was 170° C. and the crystallization time was 72 h;

[0070] Step 4: After the autoclave is cooled to room temperature, the slurry is taken out and centrifuged and washed with deionized water until the pH value is neutral.

[0071] Step 5: Place the centrifuged sample in an oven and dry it at 80°C for 12 hours, then calcine it at 550°C for 6 hours to obtain pure silicon molecular sieve Silicalite-1, recorded as S-1.

[0072] Preparation of hydrogen-type mesoporous and microporous composite hierarchical pore molecular sieves:

[0073] Step 6: Weigh 8 g of the above S-1, 80 g of deionized water and 0.16 g of NaOH and mix them, then stir at 50° C. for 3 h to obtain a slurry;

[0074] Step 7: Take out the slurry and centrifuge it, and wash the solid precipitate obtained by centrifugation with deionized water until it is neutral;

[0075] Step 8: Weigh 80 g of deionized water and 2.14 g of NH4Cl and mix them evenly to obtain an aqueous solution of ammonium chloride. Add the solid precipitate obtained in step 7 to the aqueous solution of ammonium chloride and stir at 90° C. for 1 h to perform ion exchange.

[0076] Step 9: Take out the slurry obtained in step 8 and centrifuge it, wash the solid precipitate obtained by centrifugation with deionized water until it is neutral, and repeat step 8 to perform ion exchange.

[0077] Step 10: Take out the slurry obtained in step 9 and centrifuge it, wash the solid precipitate obtained by centrifugation with deionized water until the pH value is neutral, and then place the obtained sample at 80°C for drying for 12 hours, and finally heat it from room temperature to 550°C at a heating rate of 2°C / min and calcine at this temperature for 4 hours to obtain a hydrogen-type mesoporous composite multi-level pore molecular sieve, denoted as SN-0.05, where "0.05" refers to the concentration of the sodium hydroxide aqueous solution used in this embodiment, i.e. 0.05 mol / L.

[0078] Preparation of propane dehydrogenation catalyst:

[0079] Weigh 0.0370 g of cobalt nitrate hexahydrate and stir and dissolve it in 3.7 mL of 1% ammonia solution, then adjust the pH value of the solution to 11 by dropping ammonia, add 1.5 g of the above SN-0.05 and stir until dissolved, adjust the pH value of the solution to 11 by dropping ammonia again, continue stirring for 2 hours, centrifuge twice at 8000 r / min, each time for 5 minutes, collect the solid and dry it at 80°C for 12 hours, finally heat it from room temperature to 550°C at a heating rate of 2°C / min and calcine it at this temperature for 4 hours to obtain a propane dehydrogenation catalyst, recorded as 0.5Co / SN-0.05, based on the total weight of SN-0.05 as 100%, the content of the cobalt active component in terms of cobalt element is 0.5wt%.

[0080] Example 2

[0081] This embodiment provides a propane dehydrogenation catalyst, which is prepared by a preparation method comprising the following specific steps:

[0082] Preparation of hydrogen-type mesoporous and microporous composite hierarchical pore molecular sieves:

[0083] Step 1: 8 g of S-1 prepared in Example 1, 73.5 g of deionized water and 6.5 g of TPAOH were weighed and mixed, and then stirred at 50° C. for 3 h to obtain a slurry;

[0084] Step 2: Take out the slurry and centrifuge it, and wash the solid precipitate obtained by centrifugation with deionized water until it is neutral;

[0085] Step 3: Weigh 80 g of deionized water and 2.14 g of NH4Cl and mix them evenly to obtain an aqueous solution of ammonium chloride. Add the solid precipitate obtained in step 7 to the aqueous solution of ammonium chloride and stir at 90° C. for 1 h to perform ion exchange.

[0086] Step 4: Take out the slurry obtained in step 3 and centrifuge it, wash the solid precipitate obtained by centrifugation with deionized water until it is neutral, and repeat step 3 to perform ion exchange.

[0087] Step 5: Take out the slurry obtained in step 4 and centrifuge it. Use deionized water to wash the solid precipitate obtained by centrifugation until the pH value is neutral. Then place the obtained sample at 80°C for drying for 12 hours. Finally, heat it from room temperature to 550°C at a heating rate of 2°C / min and calcine it at this temperature for 4 hours to obtain a hydrogen-type mesoporous composite multi-level pore molecular sieve, denoted as SN-0.1, where "0.1" refers to the concentration of the TPAOH aqueous solution used in this embodiment, i.e. 0.1 mol / L.

[0088] Preparation of propane dehydrogenation catalyst:

[0089] Weigh 0.0370 g of cobalt nitrate hexahydrate and stir and dissolve it in 3.7 mL of 1% ammonia solution, then adjust the pH value of the solution to 11 by dropping ammonia water, add 1.5 g of the above SN-0.1 and stir until dissolved, adjust the pH value of the solution to 11 by dropping ammonia water again, continue stirring for 2 hours, centrifuge twice at 8000 r / min, each time for 5 minutes, collect the solid and dry it at 80°C for 12 hours, finally heat it from room temperature to 550°C at a heating rate of 2°C / min and calcine at this temperature for 4 hours to obtain a propane dehydrogenation catalyst, recorded as 0.5Co / SN-0.1, based on the total weight of SN-0.1 as 100%, the content of the cobalt active component in terms of cobalt element is 0.5wt%.

[0090] Example 3

[0091] This embodiment provides a propane dehydrogenation catalyst, which is prepared by a preparation method comprising the following specific steps:

[0092] 0.0302 g of cobalt chloride hexahydrate was weighed and stirred and dissolved in 3.7 mL of ammonia solution with a mass concentration of 1%, and then the pH value of the solution was adjusted to 10.5 by dropping ammonia water, and then 1.5 g of SN-0.05 prepared in Example 1 was added and stirred until dissolved, and the pH value of the solution was adjusted to 10.5 by dropping ammonia water again. After stirring for 2 hours, the solution was centrifuged twice at 8000 r / min, each time for 5 minutes, and the solid was collected and dried at 80° C. for 12 hours, and then heated from room temperature to 550° C. at a heating rate of 2° C. / min and calcined at this temperature for 4 hours to obtain a propane dehydrogenation catalyst, recorded as C3-0.5Co / SN-0.05, and the total weight of SN-0.05 was 100%, and the content of the cobalt active component in terms of cobalt element was 0.5wt%.

[0093] Comparative Example 1

[0094] This comparative example provides a propane dehydrogenation catalyst, which is prepared by a conventional impregnation method, and the preparation method comprises the following steps:

[0095] Preparation of pure silicon molecular sieve Silicalite-1:

[0096] Step 1: Weigh 22.5 g of deionized water and 19.5 g of TPAOH (25 wt%) and mix the two, then stir at a temperature of 50° C. and a rotation speed of 500 r / min for 10 min to mix the two uniformly to obtain a mixed solution;

[0097] Step 2: Weigh 12.5 g of TEOS and slowly add it to the above mixed solution, then stir at 50° C. for 6 h to obtain a mixture;

[0098] Step 3: The mixture was transferred into a 100 ml autoclave, and the autoclave was placed in an oven for hydrothermal crystallization, wherein the hydrothermal crystallization temperature was 170° C. and the crystallization time was 72 h;

[0099] Step 4: After the autoclave is cooled to room temperature, the slurry is taken out and centrifuged and washed with deionized water until the pH value is neutral.

[0100] Step 5: Place the centrifuged sample in an oven and dry it at 80°C for 12 hours, then calcine it at 550°C for 6 hours to obtain pure silicon molecular sieve Silicalite-1, recorded as S-1.

[0101] That is, in Comparative Example 1, the preparation method of pure silicon molecular sieve Silicalite-1 is the same as that of Example 1.

[0102] Preparation of propane dehydrogenation catalyst:

[0103] Step 6: Weigh 1.5 g of the above S-1, 0.0370 g of cobalt nitrate hexahydrate and 1.5 g of deionized water, mix them and perform equal volume impregnation, and let stand overnight;

[0104] Step 7: Place the product obtained after the impregnation in step 6 in an oven and dry it at 80°C for 12 hours, and then calcine it at 550°C for 4 hours to obtain the propane dehydrogenation catalyst, recorded as 0.5Co / S1, with the total weight of S-1 being 100%, and the content of the cobalt active component in terms of cobalt element being 0.5wt%.

[0105] Comparative Example 2

[0106] This comparative example provides a propane dehydrogenation catalyst, which is prepared by a conventional impregnation method, and the preparation method comprises the following steps:

[0107] Preparation of pure silicon molecular sieve Silicalite-1:

[0108] Step 1: Weigh 22.5 g of deionized water and 19.5 g of TPAOH (25 wt%) and mix the two, then stir at a temperature of 50° C. and a rotation speed of 500 r / min for 10 min to mix the two uniformly to obtain a mixed solution;

[0109] Step 2: Weigh 12.5 g of TEOS and slowly add it to the above mixed solution, then stir at 50° C. for 6 h to obtain a mixture;

[0110] Step 3: The mixture was transferred into a 100 ml autoclave, and the autoclave was placed in an oven for hydrothermal crystallization, wherein the hydrothermal crystallization temperature was 170° C. and the crystallization time was 72 h;

[0111] Step 4: After the autoclave is cooled to room temperature, the slurry is taken out and centrifuged and washed with deionized water until the pH value is neutral.

[0112] Step 5: Place the centrifuged sample in an oven and dry it at 80°C for 12 hours, then calcine it at 550°C for 6 hours to obtain pure silicon molecular sieve Silicalite-1, recorded as S-1.

[0113] Preparation of hydrogen-type mesoporous and microporous composite hierarchical pore molecular sieves:

[0114] Step 6: Weigh 8 g of the above S-1, 80 g of deionized water and 0.16 g of NaOH and mix them, then stir at 50° C. for 3 h to obtain a slurry;

[0115] Step 7: Take out the slurry and centrifuge it, and wash the solid precipitate obtained by centrifugation with deionized water until it is neutral;

[0116] Step 8: Weigh 80 g of deionized water and 2.14 g of NH4Cl and mix them evenly to obtain an aqueous solution of ammonium chloride. Add the solid precipitate obtained in step 7 to the aqueous solution of ammonium chloride and stir at 90° C. for 1 h to perform ion exchange.

[0117] Step 9: Take out the slurry obtained in step 8 and centrifuge it, wash the solid precipitate obtained by centrifugation with deionized water until it is neutral, and repeat step 8 to perform ion exchange.

[0118] Step 10: Take out the slurry obtained in step 9 and centrifuge it, wash the solid precipitate obtained by centrifugation with deionized water until the pH value is neutral, and then place the obtained sample at 80°C for drying for 12 hours, and finally heat it from room temperature to 550°C at a heating rate of 2°C / min and calcine at this temperature for 4 hours to obtain a hydrogen-type mesoporous composite multi-level pore molecular sieve, denoted as SN-0.05, where "0.05" refers to the concentration of the sodium hydroxide aqueous solution used in this embodiment, i.e. 0.05 mol / L.

[0119] That is, in Comparative Example 1, the preparation method of the pure silicon molecular sieve Silicalite-1 and the hydrogen-type mesoporous composite multi-level pore molecular sieve is the same as that of Example 1.

[0120] Preparation of propane dehydrogenation catalyst:

[0121] Step 11: Weigh 1.5 g of the above SN-0.05, 0.0370 g of cobalt nitrate hexahydrate and 1.5 g of deionized water, mix them and perform equal volume impregnation, and let stand overnight;

[0122] Step 12: The product obtained after the impregnation in step 11 is placed in an oven and dried at 80° C. for 12 hours, and then calcined at 550° C. for 4 hours to obtain the propane dehydrogenation catalyst, recorded as D2-0.5Co / SN-0.05. The total weight of SN-0.05 is 100%, and the content of the cobalt active component in terms of cobalt element is 0.5wt%.

[0123] Comparative Example 3

[0124] This comparative example provides a propane dehydrogenation catalyst, which is prepared by a conventional impregnation method, and the preparation method comprises the following steps:

[0125] Preparation of pure silicon molecular sieve Silicalite-1:

[0126] Step 1: Weigh 22.5 g of deionized water and 19.5 g of TPAOH (25 wt%) and mix the two, then stir at a temperature of 50° C. and a rotation speed of 500 r / min for 10 min to mix the two uniformly to obtain a mixed solution;

[0127] Step 2: Weigh 12.5 g of TEOS and slowly add it to the above mixed solution, then stir at 50° C. for 6 h to obtain a mixture;

[0128] Step 3: The mixture was transferred into a 100 ml autoclave, and the autoclave was placed in an oven for hydrothermal crystallization, wherein the hydrothermal crystallization temperature was 170° C. and the crystallization time was 72 h;

[0129] Step 4: After the autoclave is cooled to room temperature, the slurry is taken out and centrifuged and washed with deionized water until the pH value is neutral.

[0130] Step 5: Place the centrifuged sample in an oven and dry it at 80°C for 12 hours, then calcine it at 550°C for 6 hours to obtain pure silicon molecular sieve Silicalite-1, recorded as S-1.

[0131] That is, in Comparative Example 1, the preparation method of pure silicon molecular sieve Silicalite-1 is the same as that of Example 1.

[0132] Preparation of propane dehydrogenation catalyst:

[0133] Step 6: Weigh 0.0370 g of cobalt nitrate hexahydrate and stir it to dissolve in 3.7 mL of 1% ammonia solution, then adjust the pH value of the solution to 11 by dropping ammonia water, add 1.5 g of the above S-1 and stir until dissolved, adjust the pH value of the solution to 11 by dropping ammonia water again, continue stirring for 2 hours, centrifuge twice at 8000 r / min, 5 minutes each time, collect the solid and dry it at 80°C for 12 hours, finally heat it from room temperature to 550°C at a heating rate of 2°C / min and calcine at this temperature for 4 hours to obtain a propane dehydrogenation catalyst, recorded as D3-0.5Co / S1, based on the total weight of S-1 as 100%, the content of cobalt active component in terms of cobalt element is 0.5wt%.

[0134] Comparative Example 4

[0135] This comparative example provides a propane dehydrogenation catalyst, which is prepared by a preparation method comprising the following specific steps:

[0136] The preparation of pure silicon molecular sieve Silicalite-1 is the same as in Example 1;

[0137] The preparation of the hydrogen-type mesoporous composite multi-level pore molecular sieve is different from that of Example 1 in that the amount of NaOH used is different, including:

[0138] Weigh 8 g of the above S-1, 80 g of deionized water and 1.6 g of NaOH and mix them, then stir at 50° C. for 3 h to obtain a slurry;

[0139] Step 7: Take out the slurry and centrifuge it, and wash the solid precipitate obtained by centrifugation with deionized water until it is neutral;

[0140] Step 8: Weigh 80 g of deionized water and 2.14 g of NH4Cl and mix them evenly to obtain an aqueous solution of ammonium chloride. Add the solid precipitate obtained in step 7 to the aqueous solution of ammonium chloride and stir at 90° C. for 1 h to perform ion exchange.

[0141] Step 9: Take out the slurry obtained in step 8 and centrifuge it, wash the solid precipitate obtained by centrifugation with deionized water until it is neutral, and repeat step 8 to perform ion exchange.

[0142] Step 10: Take out the slurry obtained in step 9 and centrifuge it, wash the solid precipitate obtained by centrifugation with deionized water until the pH value is neutral, and then place the obtained sample at 80°C for drying for 12 hours, and finally heat it from room temperature to 550°C at a heating rate of 2°C / min and calcine at this temperature for 4 hours to obtain a hydrogen-type mesoporous composite multi-level pore molecular sieve, denoted as SN-0.5, where "0.5" refers to the concentration of the sodium hydroxide aqueous solution used in this embodiment, i.e. 0.5 mol / L.

[0143] Preparation of propane dehydrogenation catalyst:

[0144] Weigh 0.0370 g of cobalt nitrate hexahydrate and stir and dissolve it in 3.7 mL of 1% ammonia solution, then adjust the pH value of the solution to 11 by dropping ammonia water, add 1.5 g of the above SN-0.5 and stir until dissolved, adjust the pH value of the solution to 11 by dropping ammonia water again, continue stirring for 2 hours, centrifuge twice at 8000 r / min, each time for 5 minutes, collect the solid and dry it at 80°C for 12 hours, finally heat it from room temperature to 550°C at a heating rate of 2°C / min and calcine at this temperature for 4 hours to obtain a propane dehydrogenation catalyst, recorded as D4-0.5Co / SN-0.5, based on the total weight of SN-0.5 as 100%, the content of the cobalt active component in terms of cobalt element is 0.5wt%.

[0145] Comparative Example 5

[0146] This comparative example provides a propane dehydrogenation catalyst, which is prepared by a preparation method comprising the following specific steps:

[0147] The preparation of pure silicon molecular sieve Silicalite-1 and hydrogen-type mesoporous composite multi-level pore molecular sieve is the same as that in Example 1:

[0148] Preparation of propane dehydrogenation catalyst:

[0149] 0.0370 g of cobalt nitrate hexahydrate was weighed and stirred and dissolved in 3.7 mL of ammonia solution with a mass concentration of 1%, and then the pH value of the solution was adjusted to 9 by dropping ammonia water, and then 1.5 g of SN-0.05 prepared in Example 1 was added and stirred until dissolved, and the pH value of the solution was adjusted to 9 by dropping ammonia water again. After continuing to stir for 2 hours, the solution was centrifuged twice at 8000 r / min, each time for 5 minutes, and the solid was collected and dried at 80° C. for 12 hours, and finally heated from room temperature to 550° C. at a heating rate of 2° C. / min and calcined at this temperature for 4 hours to obtain a propane dehydrogenation catalyst, recorded as D5-0.5Co / SN-0.05, and the total weight of SN-0.05 was 100%, and the content of the cobalt active component in terms of cobalt element was 0.5wt%.

[0150] Characterization Test Example 1

[0151] In this characterization test example, S-1, SN-0.05, 0.5Co / S1 and 0.5Co / SN-0.05 were analyzed by scanning electron microscope. The obtained scanning electron microscope images are as follows: Figure 1a-1d As shown; In this test example, TEM analysis was also performed on 0.5Co / SN-0.05, and EDS analysis was performed on 0.5Co / S1 and 0.5Co / SN-0.05, respectively. The TEM image of 0.5Co / SN-0.05 is shown in Figure 1e As shown, the elemental surface scan of 0.5Co / SN-0.05 is shown in the figure Figure 1f-1h As shown, the elemental surface scan of 0.5Co / S1 is as follows Figure 1i-1k shown.

[0152] from Figure 1a It can be seen that S-1 is in the shape of a flat hexagonal prism. The basic morphology of the SN-0.05 sample obtained after alkali treatment of S-1 remains unchanged, but the edges of the prisms are obviously blurred, and unlike the smooth surface of S-1, the surface of the SN-0.05 sample is rough and has "gullies", such as Figure 1b As shown, the loading of Co did not significantly affect the morphology of S-1 and SN-0.05 samples, as shown in Figure 1d and Figure 1e shown.

[0153] from Figure 1e The transmission electron micrograph shown clearly shows the mesoporous structure present in the SN-0.05 sample obtained after alkali treatment.

[0154] from Figure 1f-1hIt can be seen that the surface Co species (should be CoO) of 0.5Co / SN-0.05 are small particles with relatively uniform size, which are highly dispersed on the multi-level porous molecular sieve support of hydrogen-type mesoporous composite. No large particles and agglomeration are found, which indicates that the surface Co species in 0.5Co / SN-0.05 catalyst has better dispersion. Figure 1i-1k It can be seen that the Co species (should be Co3O4) on the surface of 0.5Co / S1 is unevenly dispersed and has a large particle size.

[0155] Characterization Test Example 2

[0156] In this characterization test example, X-ray diffraction analysis was performed on S-1, SN-0.05, 0.5Co / S1 and 0.5Co / SN-0.05, and the obtained X-ray diffraction (XRD) patterns were as follows: Figure 2 As shown. Figure 2 It can be seen that the typical characteristic peaks belonging to the MFI framework structure appeared between 2θ=22.5-25° for S-1 and SN-0.05 molecular sieves after alkali treatment, and no other impurity crystal peaks appeared, indicating that the prepared samples were all pure phase S-1 molecular sieves, the area of ​​SN-0.05 at 2θ=22.5-25° was taken as I, the area of ​​S-1 at 2θ=22.5-25° was taken as I0, the relative crystallinity was (I / I0)×100%, and the relative crystallinity of S-1 was set as 100%. From the calculation results, it can be seen that the crystallinity of the SN-0.05 sample treated with 0.05mol / L NaOH alkali solution is better, 90% higher.

[0157] from Figure 2 It can also be seen that both 0.5Co / S1 and 0.5Co / SN-0.05 have typical five-finger peaks belonging to the MFI skeleton structure, and no other impurity peaks appear. The diffraction peak heights of the two catalysts are basically the same, indicating that the loading of Co has no effect on the crystal structure of the carrier. No relevant diffraction peaks of Co species were detected in the two catalysts, indicating that the Co species are evenly distributed on the surface of the carrier.

[0158] Characterization Test Example 3

[0159] In this characterization test example, S-1, SN-0.05, 0.5Co / S1 and 0.5Co / SN-0.05 were subjected to N2 physical adsorption and desorption isotherms. The obtained N2 physical adsorption and desorption isotherms are shown in the figure. Figure 3 As shown. Figure 3 It can be seen that 0.5Co / S1 is a typical type I adsorption isotherm, indicating that the carrier used by the catalyst is a traditional microporous molecular sieve, while the N2 physical adsorption-desorption isotherm of 0.5Co / SN-0.05 shows an obvious hysteresis loop, which belongs to the type V adsorption isotherm, proving that the carrier used by the catalyst is in a multi-level porous state.

[0160] Characterization Test Example 4

[0161] In this characterization test example, Raman spectra of 0.5Co / S1 and 0.5Co / SN-0.05 were analyzed respectively. The obtained Raman spectra are shown in the figure below. Figure 4 As shown. Figure 4 It can be seen that the two samples have a -1 and 800cm -1 There are two obvious adsorption bands at 465 cm-1, which corresponds to the MFI topology of the molecular sieve. -1 、593cm -1 and 680cm -1 New Raman bands appeared, which were attributed to Co3O4 species; at 1046cm -1 A weaker framework Co 2+ -O-Si asymmetric stretching vibration peak, this is because there are also some holes in S-1, and a small amount of Co will enter the skeleton after impregnation with cobalt salt; while the 0.5Co / SN-0.05 catalyst has a peak at 1046cm -1 and 1160cm -1 Stronger vibration peaks appeared, which indicated that Co atoms were more incorporated into the molecular sieve framework in the 0.5Co / SN-0.05 catalyst.

[0162] Characterization Test Example 5

[0163] In this characterization test example, 0.5Co / S1 and 0.5Co / SN-0.05 were analyzed by X-ray photoelectron spectroscopy. The obtained X-ray photoelectron spectra (XPS spectra) are shown as follows: Figure 5 As shown. Figure 5 As can be seen, the 0.5Co / S1 catalyst shows Co 2+ and Co 3+ The two spin-orbit doublets and their broad satellite peaks, of which the peak at 781.5 eV is attributed to Co 2+ , the peak at 780.0 eV is attributed to Co 3+ , and Co 2+ / Co 3+ (the molar ratio of the two) is 1.51; the 0.5Co / SN-0.05 catalyst also shows the corresponding 2+ and Co 3+ characteristic peaks, but among them Co 2+ / Co 3+ The molar ratio of the two is 3.39. This indicates that the Co species in the 0.5Co / SN-0.05 catalyst is mainly tetracoordinated Co 2+The Co species in 0.5Co / S1 catalyst are mostly Co3O4 species.

[0164] Catalyst Performance Evaluation Example

[0165] In this example, the performance of 0.5Co / SN-0.05, 0.5Co / SN-0.1, C3-0.5Co / SN-0.05, 0.5Co / S1, D2-0.5Co / SN-0.05, D3-0.5Co / S1, D4-0.5Co / SN-0.5 and D5-0.5Co / SN-0.05 provided by Examples 1 to 3 of the present invention and Comparative Examples 1 to Comparative Examples was evaluated for propane dehydrogenation to propylene, including:

[0166] The catalyst was pressed into tablets and then ground and sieved. The 40-60 mesh portion was taken and the evaluation experiment was carried out in a continuous flow fixed bed reactor. Specifically, 0.2 g of the sieved catalyst was loaded into a quartz tube with an inner diameter of 6 mm. The temperature in the tube was programmed by a tubular resistance furnace and a temperature controller. The temperature was first programmed from room temperature to 580° C. in a nitrogen atmosphere. At 580° C., a H2 / N2 mixed gas containing 20v% H2 was introduced to reduce and activate the catalyst for 40 min at a total flow rate of 5 ml / min. Subsequently, a C3H8 / N2 mixed gas containing 5.04v% C3H8 was introduced to carry out propane dehydrogenation to propylene reaction at a total flow rate of 10 ml / min. After 10 min of reaction, the reaction was analyzed online by a gas chromatograph.

[0167] The catalyst regeneration method includes: after the catalyst reacts for 2 hours according to the above process, air is introduced at a temperature of 580°C for calcination for 1 hour at a flow rate of 10 ml / min, then H2 / N2 mixed gas containing 20v% H2 is introduced for reduction activation for 40 minutes at a total flow rate of 5 ml / min, and then C3H8 / N2 mixed gas containing 5.04v% C3H8 is introduced for propane dehydrogenation to propylene reaction at a total flow rate of 10 ml / min, and after reacting for 10 minutes, online analysis is performed using a gas chromatograph. Regeneration is then performed every 2 hours of reaction.

[0168] The laboratory uses a Linghua 9890B gas chromatograph with a TCD detector.

[0169] The performance of 0.5Co / S1 and 0.5Co / SN-0.05 catalysts for propane dehydrogenation is shown in the figure below. Figure 6 As shown. Figure 6 It can be seen that compared with the 0.5Co / S1 catalyst prepared in Comparative Example 1, the 0.5Co / SN-0.05 catalyst synthesized in Example 1 of the present invention exhibits higher catalytic performance.

[0170] The stability test of 0.5Co / SN-0.05 catalyst for propane dehydrogenation reaction is shown in the figure Figure 7 As shown. Figure 7 It can be seen that the initial conversion rate of the 0.5Co / SN-0.05 catalyst synthesized in Example 1 of the present invention is as high as 59%, and the selectivity is 98%. After 12h stability test, the conversion rate is still maintained at 50%, the selectivity is still 98%, and the deactivation rate is 0.033h -1 , indicating that the 0.5Co / SN-0.05 catalyst has good reaction stability.

[0171] The regeneration test of 0.5Co / SN-0.05 catalyst for propane dehydrogenation reaction is shown in the figure Figure 8 As shown. Figure 8 It can be seen that after the 0.5Co / SN-0.05 catalyst synthesized in Example 1 of the present invention was regenerated three times, the initial conversion rate could still reach 58%, and the selectivity was 97%, which was equivalent to the activity of the fresh catalyst, indicating that the 0.5Co / SN-0.05 catalyst had good regeneration performance.

[0172] The average propane conversion rate and average propylene selectivity data of each catalyst provided by Examples 1 to 3 of the present invention and Comparative Examples 1 to Comparative Examples are shown in Table 1 below.

[0173] Table 1

[0174]

[0175]

[0176] As can be seen from Table 1, compared with the 0.5Co / S1 catalyst and the D3-0.5Co / S1 catalyst prepared by the conventional impregnation method and the strong electrostatic adsorption method respectively in Comparative Examples 1 and 3 using pure silicon molecular sieve Silicalite-1 as the carrier, the average propane conversion rate of the 0.5Co / SN-0.05 catalyst prepared by the strong electrostatic adsorption method using the hydrogen-type mesoporous composite multi-level pore molecular sieve as the carrier in Example 1 of the present invention is significantly improved, and the average propylene selectivity is slightly improved; while compared with the D2-0.5Co / SN-0.05 catalyst prepared by the conventional impregnation method using the hydrogen-type mesoporous composite multi-level pore molecular sieve as the carrier in Comparative Example 2, the average propane conversion rate of the 0.5Co / SN-0.05 catalyst provided in Example 1 of the present invention is only slightly improved, and the average propylene selectivity is slightly improved.

[0177] By comparing the above results, it can be seen that the use of the hydrogen-type mesoporous composite multi-level pore molecular sieve obtained by alkali treatment as the catalyst carrier and the use of the strong electrostatic adsorption method to prepare the catalyst in the embodiments of the present invention can both improve the average propane conversion rate and the average propylene selectivity of the obtained catalyst, but the former contributes more to the improvement of the average propane conversion rate and the average propylene selectivity.

[0178] It can also be seen from Table 1 that when the alkali treatment liquid used in the alkali treatment is an aqueous sodium hydroxide solution, the average propane conversion rate and the average propylene selectivity of the catalyst prepared by using an aqueous sodium hydroxide solution with a concentration of 0.05 mol / L in Example 1 of the present invention are as high as 57% and 98%, respectively, while the average propane conversion rate and the average propylene selectivity of the catalyst prepared by using an aqueous sodium hydroxide solution with a concentration of 0.5 mol / L in Comparative Example 4 are only 48% and 95%, respectively, which indicates that the concentration of the alkali treatment liquid used in the alkali treatment affects the activity and selectivity of the prepared catalyst, and when the alkali treatment liquid is an aqueous sodium hydroxide solution, its concentration is in the range of 0.01-0.3 mol / L to achieve the purpose of the present invention and achieve the beneficial technical effects shown above;

[0179] It can also be seen from Table 1 that in Comparative Example 1, the pH value of the system during the preparation of the catalyst by the strong electrostatic adsorption method was only 9, and the average propane conversion rate and the average propylene selectivity of the prepared catalyst were only 53% and 97%, respectively. In Example 1 of the present invention, the pH value of the system during the preparation of the catalyst by the strong electrostatic adsorption method was controlled to 11, and the average propane conversion rate and the average propylene selectivity of the prepared catalyst were improved, reaching 57% and 98%, respectively. This shows that the pH value of the system during the preparation of the catalyst by the strong electrostatic adsorption method will also affect the activity and selectivity of the prepared catalyst. Only when the pH value is within the range of 10.5-11.5 can the purpose of the present invention be achieved and the beneficial technical effects shown above be achieved.

[0180] The above is only a specific embodiment of the present invention, and cannot be used to limit the scope of the invention. Therefore, the replacement of equivalent components, or equivalent changes and modifications made according to the protection scope of the patent of the present invention, should still fall within the scope of this patent. In addition, the technical features of the present invention can be freely combined with each other, with each other and with each other, and with each other.

Claims

1. A propane dehydrogenation catalyst, characterized in that: The propane dehydrogenation catalyst comprises a hydrogen-type mesoporous composite multi-level porous molecular sieve carrier and a cobalt active component, wherein a part of the cobalt active component is loaded on the surface of the hydrogen-type mesoporous composite multi-level porous molecular sieve carrier in the form of CoO nanoparticles, and another part of the cobalt active component enters the skeleton of the hydrogen-type mesoporous composite multi-level porous molecular sieve carrier in the form of forming chemical bonds and forms CoO nanoparticles. 2+ -O-Si structure; Based on the total weight of the hydrogen-type mesoporous and microporous composite multi-level porous molecular sieve carrier being 100%, the content of the cobalt active component in terms of cobalt element is 0.1-7wt%.

2. The propane dehydrogenation catalyst according to claim 1, characterized in that In the propane dehydrogenation catalyst, the molar ratio of divalent cobalt to trivalent cobalt is greater than 3.

3. The method for preparing a propane dehydrogenation catalyst according to claim 1 or 2, characterized in that: The preparation method comprises: Step (1): using an alkali treatment solution to treat pure silicon molecular sieve Silicalite-1, and then subjecting the alkali treatment product to ion exchange with an ammonium salt, and then drying and calcining the ion exchange product to obtain a hydrogen-type mesoporous and microporous composite multi-level pore molecular sieve; Step (2): fully dissolving the cobalt salt and the hydrogen-type mesoporous composite multi-level porous molecular sieve in an ammonia solution, and adjusting the pH value of the system so that the cobalt ions are adsorbed on the surface of the hydrogen-type mesoporous composite multi-level porous molecular sieve and enter the cavities of its skeleton, and then drying and calcining the obtained solid precipitate to obtain the propane dehydrogenation catalyst.

4. The preparation method according to claim 3, characterized in that: The alkaline treatment solution includes a sodium hydroxide aqueous solution, a tetrapropylammonium hydroxide aqueous solution or a tetraethylammonium hydroxide aqueous solution.

5. The preparation method according to claim 3 or 4, characterized in that: The concentration of the alkaline treatment liquid is 0.01-1 mol / L, and the mass ratio of pure silicon molecular sieve Silicalite-1 to the alkaline treatment liquid is 1:5-15.

6. The preparation method according to claim 5, characterized in that: When the alkaline treatment solution is a sodium hydroxide aqueous solution, its concentration is 0.01-0.3 mol / L.

7. The preparation method according to claim 3 or 4, characterized in that: The temperature of the alkali treatment is room temperature-100°C, and the time is 1-6h.

8. The preparation method according to claim 3 or 4, characterized in that: In step (1), the temperature of ion exchange is not higher than 100°C.

9. The preparation method according to claim 3 or 4, characterized in that: In step (1) and step (2), the drying temperature is 60-120°C.

10. The preparation method according to claim 3 or 4, characterized in that: In step (1) and step (2), the calcination is carried out by heating the temperature from room temperature to 500-600°C at a heating rate of 0.5-5°C / min and keeping the temperature for 2-8h.

11. The preparation method according to claim 3, characterized in that: In step (2), the pH value of the system is adjusted to 10.5-11.

5.

12. The preparation method according to claim 3 or 11, characterized in that: Step (2) specifically comprises first dissolving the cobalt salt in an ammonia solution and then adjusting the pH value of the system to 10.5-11.5, then adding a hydrogen-type mesoporous composite multi-level pore molecular sieve and allowing it to fully dissolve and then adjusting the pH value of the system to 10.5-11.5 again, and then drying and calcining the obtained solid precipitate to obtain the propane dehydrogenation catalyst.

13. The preparation method according to claim 3, characterized in that: The cobalt salt includes one or a combination of cobalt nitrate hexahydrate, cobalt chloride hexahydrate, cobalt acetate, cobalt carbonyl, Co-EDTA complex and cobalt acetylacetonate complex.

14. The preparation method according to claim 3 or 13, characterized in that: The mass concentration of the ammonia solution is 1-2%.

15. Use of the propane dehydrogenation catalyst according to claim 1 or 2 in the production of propylene by dehydrogenation of propane.

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