A propane dehydrogenation catalyst, a preparation method and application thereof

Abstract

The application provides a propane dehydrogenation catalyst and a preparation method and application thereof, wherein the propane dehydrogenation catalyst comprises a hydrogen-type mesopore-combined multi-level pore 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 mesopore-combined multi-level pore molecular sieve carrier in the form of CoO nanoparticles, and the other part of the cobalt active component enters the framework of the hydrogen-type mesopore-combined multi-level pore molecular sieve carrier in the form of chemical bonds and forms Co 2+ -O-Si structure; and the content of the cobalt active component in terms of cobalt elements is 0.1-7 wt% based on 100% of the total weight of the hydrogen-type mesopore-combined multi-level pore molecular sieve carrier. The propane dehydrogenation catalyst provided by the application has excellent catalytic propane dehydrogenation reaction activity and stability.

Description

TECHNICAL FIELD

[0001] The present application relates to a kind of propane dehydrogenation catalyst and its preparation method and application, belong to petrochemical technical field. BACKGROUND

[0002] Propylene is widely used in rubber, medicine and textile and other fields as the basic raw material of many organic chemical products.Propane dehydrogenation to propylene technology (PDH) has the advantages of short process, high propylene selectivity, environmental friendliness and low comprehensive cost, and has been continuously concerned and developed.Propane dehydrogenation is a strong endothermic reaction, which needs to be carried out at high temperature.However, high reaction temperature is easy to cause deep dehydrogenation and cracking of propylene, which not only reduces the yield of propylene but also leads to 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-based and Cr-based catalysts.However, noble metal Pt is expensive, and high-priced Cr is toxic to the human body and the environment.Transition metal Co is abundant and non-toxic, and some studies have found that molecular sieve catalysts synthesized with metal Co as active phase have good propane dehydrogenation reaction activity, and Co 2+ can effectively activate the C-H bond of propane to generate propylene and hydrogen.However, the catalysts with traditional microporous, mesoporous or macroporous molecular sieves as carriers and loaded with Co by impregnation method face problems such as unclear catalytic active sites, poor metal dispersion, easy sintering and carbon deposition, and rapid deactivation of the catalyst.

[0004] The carrier, as the basis of the catalyst composition, has a crucial influence on catalytic activity and stability.The traditional molecular sieve has relatively single composition: the intrinsic pore channel of microporous molecular sieve is narrow, which limits the transmission of the substrate and easily causes carbon deposition and deactivation of the catalyst;mesoporous or macroporous molecular sieve is difficult to anchor active components and cannot avoid sintering of active sites.At present, a large number of studies focus on the method of introducing mesopores into the microporous molecular sieve crystal to prepare hierarchical pore molecular sieves with at least two pores (intrinsic microporous channels and mesopores).Compared with traditional molecular sieves, hierarchical pore molecular sieves have mesopores, which not only can improve the carbon capacity of the carrier, but also are beneficial to the mass transfer of the substrate and product, thereby inhibiting carbon deposition and effectively improving the activity and stability of the propane dehydrogenation catalyst.

[0005] It has been a research difficulty to prepare isolated stable Co-based active center catalysts. The metal-loaded molecular sieves prepared by traditional loading methods are prone to cause uneven particle size of metal nanoparticles, poor dispersibility, unclear active sites, and ultimately poor catalytic performance. At present, the main method in the field is to add metal promoters to improve the dispersibility of Co, but there are still problems such as poor propane conversion rate and propylene selectivity, poor catalytic activity, and poor catalyst stability. The molecular sieve encapsulated metal catalyst prepared by using metal chelates as raw materials can realize the implantation of Co into the molecular sieve framework, effectively inhibit the aggregation of metal particles by using the internal microporous structure of the molecular sieve, and further improve the catalytic reaction performance, but there are defects such as long hydrothermal time, high hydrothermal temperature, large amount of template agent, and environmental pollution caused by burning out the template agent during in-situ synthesis of the catalyst.

[0006] Therefore, it has become a technical problem to be solved in the field to provide a novel propane dehydrogenation catalyst and a preparation method and application thereof. SUMMARY

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

[0008] Another object of the present application is also to provide a preparation method of the above-mentioned propane dehydrogenation catalyst.

[0009] Still another object of the present application is also to provide the application of the above-mentioned propane dehydrogenation catalyst in propane dehydrogenation to prepare propylene.

[0010] In order to achieve the above objects, on the one hand, the present application provides a propane dehydrogenation catalyst, wherein the propane dehydrogenation catalyst comprises a hydrogen-type mesopore-combined hierarchical pore 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 mesopore-combined hierarchical pore molecular sieve carrier in the form of CoO nanoparticles, and another part of the cobalt active component enters the framework of the hydrogen-type mesopore-combined hierarchical pore molecular sieve carrier in the form of chemical bond and forms Co 2+ -O-Si structure;

[0011] The content of the cobalt active component in terms of cobalt element is 0.1-7wt% based on 100% of the total weight of the hydrogen-type mesopore-combined hierarchical pore molecular sieve carrier.

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

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

[0014] Step (1): the pure silicon molecular sieve Silicalite-1 is treated with an alkaline treatment solution, and then the treated product is ion-exchanged with an ammonium salt, and the ion-exchanged product is dried and calcined to obtain a hydrogen-type mesoporous composite multi-level pore molecular sieve;

[0015] Step (2): the cobalt salt and the hydrogen-type mesoporous composite multi-level pore molecular sieve are fully dissolved in an ammonia solution, and the pH value of the system is adjusted to allow the cobalt ions to be adsorbed on the surface of the hydrogen-type mesoporous composite multi-level pore molecular sieve and enter the cavities in the framework of the hydrogen-type mesoporous composite multi-level pore molecular sieve, and then the obtained solid precipitate is dried and calcined to obtain the propane dehydrogenation catalyst.

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

[0017] The silicon source, the structure directing agent and water are mixed uniformly to obtain a mixed solution, the mixed solution is subjected to hydrothermal crystallization, and then 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 several of tetraethyl orthosilicate, solid silica gel, white carbon black and silica sol, and the structure directing agent includes one or a combination of several of tetrapropylammonium hydroxide (TPAOH), tetrapropylammonium chloride, tetraethylammonium hydroxide and tetraethylammonium chloride, tetrapropylammonium salt and / or tetraethylammonium salt.

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

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

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

[0022] As a specific embodiment of the preparation method described above, the concentration of the alkaline treatment solution is 0.01-1mol / L, and the mass ratio of the 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 application, when the alkali treatment solution is a sodium hydroxide aqueous solution, the concentration thereof is 0.01-0.3 mol / L.

[0024] As a specific embodiment of the above preparation method of the present application, the temperature of the alkali treatment is normal temperature-100℃, and the time is 1-6 h.

[0025] As a specific embodiment of the above preparation method of the present application, step (1) further comprises washing the alkali treatment product to neutral and then ion exchanging the alkali treatment product with an ammonium salt. The washing liquid used in the washing may be, for example, deionized water, etc.

[0026] As a specific embodiment of the above preparation method of the present application, in step (1), the temperature of the ion exchange is not higher than 100℃. In a more preferred embodiment of the present application, the ion exchange may be repeated for multiple times to make the exchange more sufficient. The ammonium salt used in the ion exchange may be, for example, ammonium chloride, etc.

[0027] As a specific embodiment of the above preparation method of the present application, in steps (1) and (2), the temperature of the drying is 60-120℃. The present application does not make specific requirements on the time of the drying, which may 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 above preparation method of the present application, in steps (1) and (2), the calcination is to heat the product from room temperature to 500-600℃ at a heating rate of 0.5-5℃ / min, and to keep the temperature for 2-8 h.

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

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

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

[0032] As a specific embodiment of the above preparation method of the present application, the cobalt salt comprises one or a combination of the following: 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 application, the ammonia solution has a mass concentration of 1-2%.

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

[0035] The present application first uses an alkali treatment solution to perform alkali treatment desilication on pure silicon molecular sieve Silicalite-1, and by adjusting the alkali treatment conditions, including the type of alkali, the treatment time, etc., a hydrogen-type mesoporous composite multi-level pore molecular sieve is prepared, and at the same time, a large number of hydroxyl defects are generated in the molecular sieve. Then, a propane dehydrogenation catalyst is prepared by using a strong electrostatic adsorption method, and in 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 electric properties, thereby forming a stable structure and preventing metal aggregation, forming highly dispersed nanoparticles, and realizing the entry of Co into the molecular sieve framework to form Co 2+ -O-Si structure.

[0036] In another aspect, the present application also provides the use of the above propane dehydrogenation catalyst in the preparation of propylene from propane dehydrogenation.

[0037] Compared with the prior art, the present application can achieve the following beneficial technical effects:

[0038] (1) The present application uses an alkali treatment solution to perform alkali treatment on 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 beneficial to the mass transfer of substrates and products, thereby inhibiting the generation of carbon deposition, and at the same time, it can also improve the carbon capacity of the carrier, which is beneficial to improving the stability of the catalyst. Specifically, the deactivation rate of the catalyst is only 0.033h -1 after 12h stability test, which shows better stability compared with the Co-based catalysts reported in the prior art (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.).

[0039] (2) The present application uses a hydrogen-type mesoporous composite multi-level pore molecular sieve as a carrier to prepare a propane dehydrogenation catalyst by a strong electrostatic adsorption method. The propane dehydrogenation catalyst has the advantages of high metal dispersion, small nano-particle size and high stability. The active metal dispersion of a catalyst synthesized by a traditional impregnation method is low and easy to agglomerate and deactivate. Compared with an in-situ hydrothermal method, the strong electrostatic adsorption method used in the present application does not require a high-temperature and high-pressure environment, reduces environmental pollution and reduces production costs.

[0040] (3) The propane dehydrogenation catalyst provided by the present application uses a hydrogen-type mesoporous composite multi-level pore molecular sieve as a carrier. A part of the cobalt active component is loaded on the surface of the hydrogen-type mesoporous composite multi-level pore molecular sieve carrier in the form of CoO nano-particles. Another part of the cobalt active component enters the framework of the hydrogen-type mesoporous composite multi-level pore molecular sieve carrier in the form of a chemical bond and forms Co 2+ -O-Si structure, that is, the active site of the propane dehydrogenation catalyst is a four-coordinated Co 2+ , while the active site of a catalyst prepared by impregnating a cobalt salt on a pure silicon molecular sieve Silicalite-1 carrier is a Co3O4 site. This is because: 1) the surface of the hydrogen-type mesoporous composite multi-level pore 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 degree of Co, 2) the framework of the hydrogen-type mesoporous composite multi-level pore molecular sieve carrier prepared after alkali treatment will form cavities. When the catalyst is prepared by a strong electrostatic adsorption method, Co atoms successfully combine into the molecular sieve framework in the form of a chemical bond to form a four-coordinated Co 2+ ; while the surface defect sites and cavities in the framework of the pure silicon molecular sieve Silicalite-1 that has not been treated with alkali are less, so that the Co species loaded on the surface of the carrier are not uniformly dispersed, the particle size is large, and only a small amount of Co enters the molecular sieve framework, mainly existing in the form of Co3O4 on the surface of the molecular sieve. Compared with the Co3O4 site generated by impregnation on a pure silicon molecular sieve Silicalite-1 carrier, the catalyst provided by the present application has a four-coordinated Co 2+ active site, which makes it have higher 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 application has excellent catalytic propane dehydrogenation reaction activity and stability. BRIEF DESCRIPTION OF DRAWINGS

[0042] In order to make the technical solutions in the embodiments of the present application or the prior art clearer, the accompanying drawings needed in the embodiments will be briefly introduced below. Obviously, the accompanying drawings in the following description are some embodiments of the present application, and other drawings can be obtained by those skilled in the art without any creative effort based on these drawings.

[0043] Figure 1a Scanning electron micrograph of S-1.

[0044] Figure 1b Scanning electron micrograph of SN-0.05.

[0045] Figure 1c Scanning electron micrograph of 0.5Co / S1.

[0046] Figure 1d Scanning electron micrograph of 0.5Co / SN-0.05.

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

[0048] Figures 1f-1h Elemental mapping of 0.5Co / SN-0.05.

[0049] Figures 1i-1k Elemental mapping 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 N2physisorption desorption isotherms of S-1, SN-0.05, 0.5Co / S1 and 0.5Co / SN-0.05.

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

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

[0054] Figure 6 Performance of 0.5Co / S1 and 0.5Co / SN-0.05 catalysts in catalyzing propane dehydrogenation reaction.

[0055] Figure 7 Stability test of 0.5Co / SN-0.05 catalyst in catalyzing propane dehydrogenation reaction.

[0056] Figure 8 Figure 4 is a graph of the regeneration test of the 0.5 Co / SN-0.05 catalyst for the dehydrogenation of propane. DETAILED DESCRIPTION

[0057] It has to be understood that the term "comprising", or variations such as "comprise" or "comprises", as used in the present specification is used in the sense of "including", and / or "comprising", and not by way of "consisting only of" or "consisting of". It is further understood that the term "comprising" is not used in the sense of "excluding" or "not including".

[0058] The ranges disclosed herein are given using the format "from x to y", in which x and y are real numbers. For a range including x and / or y, and including the endpoints, there are no lower or upper limits. In other words, "from x to y" indicates that a range from any explicitly recited minimum value (if any) to any explicitly recited maximum value (if any). When no minimum or maximum, or no minimum and maximum, are explicitly recited, those limits are 0 or positive infinity. In addition, it is specifically intended that the minimum and maximum values given are included in the range. It is also specifically intended that any intervening values and intervening ranges are included in the range. For values which are less than one, or components of a range which are less than one, "up to" the indicated number of digits is specifically contemplated. For example, "up to 90%" means 0, 1, 2, 3, 4, 5, 6, 7, 8, or 9, and any ranges or combinations thereof.

[0059] In the present application, unless otherwise stated, the numerical range "a-b" indicates a shorthand for the inclusion of any and all integers between (and including) a and b, in which a and b are real numbers. For example, the numerical range "0-5" indicates that all real numbers between (and including) "0-5" have been listed in the present application, "0-5" is just a shorthand for these numerical combinations.

[0060] In the present application, all the embodiments and preferred embodiments mentioned in the present application can be combined with each other to form new technical solutions, unless otherwise stated.

[0061] In the present application, all the technical features and preferred features mentioned in the present application can be combined with each other to form new technical solutions, unless otherwise stated.

[0062] In the present application, if not otherwise specified, all the steps mentioned herein can be carried out in sequence or randomly, but preferably in sequence. For example, the method comprises steps (a) and (b), which means that the method can comprise steps (a) and (b) in sequence, or steps (b) and (a) in sequence. For example, the method mentioned herein can further comprise step (c), which means that step (c) can be added to the method in any sequence, for example, the method can comprise steps (a), (b) and (c), or steps (a), (c) and (b), or steps (c), (a) and (b), etc.

[0063] In order to make the objectives, technical solutions and advantages of the present application clearer, the present application will be further described in detail below in combination with the accompanying tables, drawings and examples. The examples described below are part of the examples of the present application, but not all the examples, and are only used to illustrate the present application, and should not be regarded as limiting the scope of the present application. Based on the examples in the present application, all the other examples obtained by those skilled in the art without making creative efforts fall within the scope of protection of the present application. If the specific conditions are not mentioned in the examples, the conventional conditions or the conditions recommended by the manufacturer are used. If the reagents or instruments used are not mentioned by the manufacturer, they are all conventional products that can be purchased on the market.

[0064] Example 1

[0065] The present example 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 them, then stir them at a temperature of 50°C and a rotation speed of 500 r / min for 10 min to make them uniformly mixed 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 a temperature of 50°C for 6 h to obtain a mixture;

[0069] Step 3: transfer the above mixture into a 100 ml autoclave, and place the autoclave in an oven for hydrothermal crystallization, wherein the temperature for hydrothermal crystallization is 170°C, and the crystallization time is 72 h;

[0070] Step 4: after the autoclave is cooled to room temperature, the slurry is taken out and sequentially subjected to centrifugation, washing with deionized water until the pH value is neutral,

[0071] Step 5: The centrifuged sample was placed in an oven and dried at 80°C for 12 h, and then calcined at 550°C for 6 h to obtain pure silicon molecular sieve Silicalite-1, denoted as S-1.

[0072] Preparation of hydrogen-type mesoporous composite hierarchical pore molecular sieve:

[0073] Step 6: 8 g of S-1, 80 g of deionized water and 0.16 g of NaOH were weighed and mixed, and then stirred at 50°C for 3 h to obtain a slurry.

[0074] Step 7: The slurry was taken out and centrifuged, and the solid precipitate obtained by centrifugation was washed to neutral with deionized water.

[0075] Step 8: 80 g of deionized water and 2.14 g of NH4Cl were weighed and mixed to obtain an ammonium chloride aqueous solution, and the solid precipitate obtained in step 7 was added to the ammonium chloride aqueous solution and stirred at 90°C for 1 h for ion exchange.

[0076] Step 9: The slurry obtained in step 8 was taken out and centrifuged, and the solid precipitate obtained by centrifugation was washed to neutral with deionized water, and then ion exchange was repeated in step 8.

[0077] Step 10: The slurry obtained in step 9 was taken out and centrifuged, and the solid precipitate obtained by centrifugation was washed to neutral with deionized water, and then the obtained sample was dried at 80°C for 12 h, and finally heated at a temperature increasing rate of 2°C / min from room temperature to 550°C and calcined at this temperature for 4 h to obtain a hydrogen-type mesoporous composite hierarchical pore molecular sieve, denoted as SN-0.05, wherein "0.05" refers to the concentration of the sodium hydroxide aqueous solution used in this example, i.e. 0.05 mol / L.

[0078] Preparation of propane dehydrogenation catalyst:

[0079] 0.0370 g of cobalt nitrate hexahydrate was weighed and dissolved in 3.7 mL of 1% ammonia water solution by stirring, and then the pH value of the solution was adjusted to 11 by adding ammonia water, 1.5 g of the above SN-0.05 was added and stirred until dissolved, the pH value of the solution was again adjusted to 11 by adding ammonia water, and then the solution was stirred for 2 h, and then centrifuged at 8000 r / min for 2 times, 5 min each time, and the solid was collected and dried at 80°C for 12 h, and finally heated at a temperature increasing rate of 2°C / min from room temperature to 550°C and calcined at this temperature for 4 h to obtain a propane dehydrogenation catalyst, denoted as 0.5Co / SN-0.05, wherein the content of cobalt active component calculated as cobalt element is 0.5 wt% based on the total weight of SN-0.05 as 100%.

[0080] Example 2

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

[0082] Preparation of hydrogen type mesoporous composite multi-level pore molecular sieve:

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

[0084] Step 2: the slurry is taken out and centrifuged, and the solid obtained by centrifugation is washed to neutral with deionized water;

[0085] Step 3: 80 g of deionized water and 2.14 g of NH4Cl are weighed and uniformly mixed to obtain an ammonium chloride aqueous solution, and the solid precipitate obtained in step 7 is added into the ammonium chloride aqueous solution and stirred at 90 DEG C for 1 h to perform ion exchange;

[0086] Step 4: the slurry obtained in step 3 is taken out and centrifuged, and the solid obtained by centrifugation is washed to neutral with deionized water, and ion exchange is performed again by repeating step 3.

[0087] Step 5: the slurry obtained in step 4 is taken out and centrifuged, and the solid obtained by centrifugation is washed to neutral with deionized water, and then the obtained sample is placed at 80 DEG C and dried for 12 h, finally, the temperature is increased from room temperature to 550 DEG C at a temperature increasing rate of 2 DEG C / min, and calcination is performed at the temperature for 4 h to obtain a hydrogen type mesoporous composite multi-level pore molecular sieve, which is recorded as SN-0.1, wherein “0.1” refers to the concentration of the TPAOH aqueous solution used in the embodiment, that is, 0.1 mol / L.

[0088] Preparation of a propane dehydrogenation catalyst:

[0089] 0.0370 g of cobalt nitrate hexahydrate is weighed and dissolved in 3.7 mL of 1% ammonia water solution by stirring, then the pH value of the solution is adjusted to 11 by dropwise adding ammonia water, 1.5 g of the above SN-0.1 is added and stirred until dissolved, the pH value of the solution is adjusted to 11 again by dropwise adding ammonia water, and after continuous stirring for 2 h, the solid is collected by centrifugation twice at 8000 r / min for 5 min each time, and then dried at 80 DEG C for 12 h, finally, the temperature is increased from room temperature to 550 DEG C at a temperature increasing rate of 2 DEG C / min, and calcination is performed at the temperature for 4 h to obtain a propane dehydrogenation catalyst, which is recorded as 0.5Co / SN-0.1, wherein the content of the cobalt active component in terms of cobalt element is 0.5 wt% based on 100% of the total weight of SN-0.1.

[0090] Embodiment 3

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

[0092] A 0.0302 g of cobalt chloride hexahydrate was weighed and dissolved in 3.7 mL of 1% ammonia water solution by stirring, and then the pH of the solution was adjusted to 10.5 by dropwise addition of ammonia water, 1.5 g of SN-0.05 prepared in Example 1 was added and stirred until dissolved, the pH of the solution was again adjusted to 10.5 by dropwise addition of ammonia water, and after stirring for 2 h, the solid was collected by centrifugation twice at 8000 r / min for 5 min each time, and dried at 80°C for 12 h, and then the temperature was increased from room temperature to 550°C at a rate of 2°C / min and calcined at this temperature for 4 h to obtain a propane dehydrogenation catalyst, which is denoted as C3-0.5Co / SN-0.05, and the content of the cobalt active component was 0.5 wt% as cobalt element based on the total weight of SN-0.05 as 100%.

[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 silica molecular sieve Silicalite-1:

[0096] Step 1: 22.5 g of deionized water and 19.5 g of TPAOH (25 wt%) were weighed and mixed, and then stirred at a temperature of 50°C and a speed of 500 r / min for 10 min to make them uniformly mixed to obtain a mixed solution;

[0097] Step 2: 12.5 g of TEOS was weighed and slowly added to the above mixed solution, and then stirred at a temperature of 50°C for 6 h to obtain a mixture;

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

[0099] Step 4: After the autoclave was cooled to room temperature, the slurry was taken out and sequentially subjected to centrifugation, washing with deionized water until the pH value was neutral,

[0100] Step 5: The centrifuged sample was placed in an oven and dried at 80°C for 12 h, and then calcined at 550°C for 6 h to obtain a pure silica molecular sieve Silicalite-1, which is denoted as S-1.

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

[0102] Preparation of a propane dehydrogenation catalyst:

[0103] Step 6: 1.5 g of S-1, 0.0370 g of cobalt nitrate hexahydrate and 1.5 g of deionized water were weighed and mixed, and then impregnated with an equal volume, and left to stand overnight;

[0104] Step 7: The product obtained after impregnation in Step 6 was placed in an oven and dried at 80°C for 12 h, and then calcined at 550°C for 4 h to obtain the propane dehydrogenation catalyst, which was recorded as 0.5Co / S1, and the content of the cobalt active component was 0.5 wt% in terms of cobalt element, based on the total weight of S-1 being 100%.

[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 silica molecular sieve Silicalite-1:

[0108] Step 1: 22.5 g of deionized water and 19.5 g of TPAOH (25 wt%) were weighed and mixed, and then stirred at a temperature of 50°C and a speed of 500 r / min for 10 min to make them uniformly mixed to obtain a mixed solution;

[0109] Step 2: 12.5 g of TEOS was weighed and slowly added to the above mixed solution, and then stirred at a temperature of 50°C for 6 h to obtain a mixture;

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

[0111] Step 4: After the autoclave was cooled to room temperature, the slurry was taken out and sequentially subjected to centrifugation, washing with deionized water until the pH value was neutral,

[0112] Step 5: The centrifuged sample was placed in an oven and dried at 80°C for 12 h, and then calcined at 550°C for 6 h to obtain the pure silica molecular sieve Silicalite-1, which was recorded as S-1.

[0113] Preparation of hydrogen-type micro-porous composite multi-level pore molecular sieve:

[0114] Step 6: 8 g of S-1, 80 g of deionized water and 0.16 g of NaOH were weighed and mixed, and then stirred at 50°C for 3 h to obtain a slurry;

[0115] Step 7: The slurry was taken out and centrifuged, and the solid precipitate obtained by centrifugation was washed with deionized water until it was neutral;

[0116] Step 8: Take 80 g of deionized water and 2.14 g of NH4CI, mix them to obtain an ammonium chloride aqueous solution, add the solid precipitate obtained in step 7 into the ammonium chloride aqueous solution, 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, wash the solid precipitate obtained by centrifugation to neutral with deionized water, and repeat step 8 to perform ion exchange.

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

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

[0120] Preparation of a propane dehydrogenation catalyst:

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

[0122] Step 12: Place the product obtained after impregnation in step 11 in an oven and dry at 80°C for 12 h, and then calcine at 550°C for 4 h to obtain the propane dehydrogenation catalyst, which is denoted as D2-0.5Co / SN-0.05, and the content of the cobalt active component, calculated as cobalt element, is 0.5 wt% based on the total weight of SN-0.05 as 100%.

[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: Take 22.5 g of deionized water and 19.5 g of TPAOH (25 wt%) and mix them, then stir at a temperature of 50°C and a rotation speed of 500 r / min for 10 min to mix them uniformly to obtain a mixed solution;

[0127] Step 2: 12.5 g of TEOS was weighed and slowly added into the above mixture, followed by stirring at 50℃ for 6h to obtain a mixture;

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

[0129] Step 4: After the autoclave was cooled to room temperature, the slurry was taken out and sequentially subjected to centrifugation, washing with deionized water until the pH value was neutral,

[0130] Step 5: The centrifuged sample was placed in an oven and dried at 80℃ for 12h, and then calcined at 550℃ for 6h to obtain pure silicon molecular sieve Silicalite-1, denoted as S-1.

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

[0132] Preparation of a propane dehydrogenation catalyst:

[0133] Step 6: 0.0370 g of cobalt nitrate hexahydrate was weighed and dissolved in 3.7 mL of 1% ammonia water solution by stirring, and then the pH value of the solution was adjusted to 11 by dropwise addition of ammonia water, 1.5 g of the above S-1 was then added and stirred until dissolved, the pH value of the solution was again adjusted to 11 by dropwise addition of ammonia water, and the stirring was continued for 2h, followed by centrifugation at 8000r / min for 2 times, 5min each time, the solid was collected and dried at 80℃ for 12h, and finally the temperature was raised from room temperature to 550℃ at a rate of 2℃ / min and calcined at this temperature for 4h to obtain a propane dehydrogenation catalyst, denoted as D3-0.5Co / S1, wherein the content of cobalt active component was 0.5wt% in terms of cobalt element based on 100% of the total weight of S-1.

[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 was the same as that of Example 1;

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

[0138] 8g of the above S-1, 80g of deionized water and 1.6g of NaOH were weighed and mixed, followed by stirring at 50℃ for 3h to obtain a slurry;

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

[0140] Step 8: Take 80 g of deionized water and 2.14 g of NH4Cl, mix them evenly to obtain an ammonium chloride aqueous solution, add the solid precipitate obtained in Step 7 into the ammonium chloride aqueous solution, 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, and wash the obtained solid precipitate with deionized water until neutral, and then repeat Step 8 to perform ion exchange.

[0142] Step 10: Take out the slurry obtained in Step 9 and centrifuge, and wash the obtained solid precipitate with deionized water until the pH value is neutral, then dry the obtained sample at 80°C for 12 h, and finally heat from room temperature to 550°C at a heating rate of 2°C / min and calcine at the temperature for 4 h to obtain a hydrogen-type meso-microporous composite hierarchical pore molecular sieve, which is denoted as SN-0.5, wherein “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 a propane dehydrogenation catalyst:

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

[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 meso-microporous composite hierarchical pore molecular sieve is the same as in Example 1:

[0148] Preparation of a propane dehydrogenation catalyst:

[0149] Example 1 was added and stirred until dissolved, the pH of the solution was adjusted to 9 by dropwise addition of ammonia water, and the stirring was continued for 2 h. The solid was collected by centrifugation twice at 8000 r / min for 5 min each time, and dried at 80°C for 12 h. Finally, the temperature was increased from room temperature to 550°C at a rate of 2°C / min and calcined at this temperature for 4 h to obtain a propane dehydrogenation catalyst, which was denoted as D5-0.5Co / SN-0.05, and the content of the active component of cobalt, as measured by the element cobalt, was 0.5 wt% based on the total weight of SN-0.05, which was taken as 100%.

[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 subjected to scanning electron microscopy analysis, and the obtained scanning electron micrographs are shown in Figures Figures 1a-1d In this characterization test example, 0.5Co / SN-0.05 was subjected to transmission electron microscopy analysis, and 0.5Co / S1 and 0.5Co / SN-0.05 were subjected to EDS analysis, respectively. The transmission electron micrograph of 0.5Co / SN-0.05 is shown in Figure Figure 1e The element mapping of 0.5Co / SN-0.05 is shown in Figure Figures 1f-1h The element mapping of 0.5Co / S1 is shown in Figure Figures 1i-1k

[0152] As can be seen from Figures Figure 1a , S-1 has a flat hexagonal prism shape. The basic morphology of the SN-0.05 sample obtained after alkali treatment of S-1 does not change, but the edges of the prism are obviously blurred, and unlike the smooth surface of S-1, the surface of the SN-0.05 sample is rough and has “gullies”, as shown in Figure Figure 1b The morphology of S-1 and SN-0.05 samples is not significantly affected after loading Co, as shown in Figures Figure 1d and Figure 1e

[0153] As can be seen from the transmission electron micrograph shown in Figure Figure 1e , the mesoporous structure present in the SN-0.05 sample obtained after alkali treatment can be clearly seen.

[0154] As can be seen from the transmission electron micrograph shown in Figure Figures 1f-1h ​​It can be seen that the surface Co species (should be CoO) of 0.5Co / SN-0.05 are relatively uniform small particles, highly dispersed on the hierarchical porous molecular sieve support of hydrogen-type mesoporous microporous composite. No large particles or agglomeration were found, indicating that the surface Co species in the 0.5Co / SN-0.05 catalyst have better dispersion. Figures 1i-1k As can be seen, the Co species (should be Co3O4) on the 0.5Co / S1 surface are unevenly dispersed and have large particle sizes.

[0155] Characterization Test Example 2

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

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

[0158] Characterization Test Example 3

[0159] In this characterization test example, N2 physical adsorption-desorption isotherms were tested for S-1, SN-0.05, 0.5Co / S1, and 0.5Co / SN-0.05, respectively. The obtained N2 physical adsorption-desorption isotherms are shown below. Figure 3 As shown. From Figure 3 As can be seen, 0.5Co / S1 is a typical Type I adsorption isotherm, indicating that the catalyst uses a traditional microporous molecular sieve as its support. However, the N2 physical adsorption-desorption isotherm of 0.5Co / SN-0.05 shows a clear hysteresis loop, which is a Type V adsorption isotherm, proving that the catalyst uses a multi-level porous support.

[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, and the obtained Raman spectra are shown below. Figure 4 As shown. From Figure 4 As can be seen from this, the two samples are at approximately 370cm. -1 and 800cm -1 Two distinct adsorption bands appear at 465 cm⁻¹, corresponding to the topology of the molecular sieve MFI. The 0.5Co / S1 catalyst exhibits this characteristic at 465 cm⁻¹. -1 593cm -1 and 680cm -1 New Raman bands appeared, which belong to the Co3O4 species; at 1046 cm -1 A weaker skeleton Co appears at this location. 2+ The asymmetric stretching vibration peak of -O-Si is due to the presence of some vacancies in S-1, and the introduction of a small amount of Co into the framework after impregnation with cobalt salt; while the 0.5Co / SN-0.05 catalyst shows a peak at 1046 cm⁻¹. -1 and 1160cm -1 Stronger vibrational peaks were observed, indicating 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] This characterization test example performed X-ray photoelectron spectroscopy (XPS) analysis on 0.5Co / S1 and 0.5Co / SN-0.05, respectively. The obtained XPS spectra are shown below. Figure 5 As shown. From Figure 5 As can be seen from this, the 0.5Co / S1 catalyst exhibits Co 2+ and Co 3+ The two spin orbital double peaks and their broad satellite peaks, with the peak at 781.5 eV 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 a corresponding Co... 2+ and Co 3+ The characteristic peaks, but Co among them 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 are mainly tetracoordinated Co. 2+It exists in various forms, and the Co species in the 0.5Co / S1 catalyst are mostly Co3O4 species.

[0164] Catalyst performance evaluation examples

[0165] This embodiment evaluates the propane dehydrogenation performance of propylene production from Examples 1-3 and Comparative Examples 1-3, using 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. The evaluation includes:

[0166] The catalyst was compressed into tablets, ground, and sieved. The 40-60 mesh fraction was used for evaluation experiments 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 inside the tube was controlled by a tubular resistance furnace and a temperature controller. The temperature was first increased from room temperature to 580 °C in a nitrogen atmosphere. At 580 °C, a H2 / N2 mixture containing 20 vol% 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 mixture containing 5.04 vol% C3H8 was introduced to carry out the propane dehydrogenation to propylene reaction at a total flow rate of 10 ml / min. After 10 min of reaction, the reaction was analyzed online using a gas chromatograph.

[0167] The catalyst regeneration method includes: after the catalyst has reacted according to the above process for 2 hours, it is calcined at 580℃ with air for 1 hour at a flow rate of 10 ml / min. Then, a H2 / N2 mixture containing 20 vol% H2 is introduced for reduction activation for 40 minutes at a total flow rate of 5 ml / min. Next, a C3H8 / N2 mixture containing 5.04 vol% C3H8 is introduced for propane dehydrogenation to propylene reaction at a total flow rate of 10 ml / min. After 10 minutes of reaction, the reaction is analyzed online using a gas chromatograph. Regeneration is then performed every 2 hours thereafter.

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

[0169] The performance of the 0.5Co / S1 and 0.5Co / SN-0.05 catalysts in the propane dehydrogenation reaction is shown in the figure below. Figure 6 As shown. From this 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 results of the 0.5Co / SN-0.05 catalyst for propane dehydrogenation are shown in the figure below. Figure 7 As shown. From this Figure 7 It can be seen that the 0.5Co / SN-0.05 catalyst synthesized in Example 1 of this invention has an initial conversion rate as high as 59% and a selectivity of 98%. After a 12-hour stability test, the conversion rate still remains at 50%, the selectivity is still 98%, and the deactivation rate is 0.033 hours. -1 This indicates that the 0.5Co / SN-0.05 catalyst has good reaction stability.

[0171] The regenerability test graph of propane dehydrogenation catalyzed by the 0.5Co / SN-0.05 catalyst is shown in the figure below. Figure 8 As shown. From this Figure 8 It can be seen that the 0.5Co / SN-0.05 catalyst synthesized in Example 1 of the present invention can still achieve an initial conversion rate of 58% and a selectivity of 97% after three regenerations, which is comparable to the activity of the fresh catalyst. This indicates that the 0.5Co / SN-0.05 catalyst has good regeneration performance.

[0172] The average propane conversion and average propylene selectivity of each catalyst provided in Examples 1-3 and Comparative Examples 1-3 of this invention 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 D3-0.5Co / S1 catalyst prepared by conventional impregnation method and strong electrostatic adsorption method respectively using pure silica molecular sieve Silicalite-1 as support in Comparative Examples 1 and 3, the 0.5Co / SN-0.05 catalyst prepared by strong electrostatic adsorption method using hydrogen-type mesoporous composite hierarchical porous molecular sieve as support in Example 1 of this invention shows a significantly improved average propane conversion and a slightly improved average propylene selectivity. Compared with the D2-0.5Co / SN-0.05 catalyst prepared by conventional impregnation method using hydrogen-type mesoporous composite hierarchical porous molecular sieve as support in Comparative Example 2, the 0.5Co / SN-0.05 catalyst provided in Example 1 of this invention shows only a small increase in average propane conversion and a slightly improved average propylene selectivity.

[0177] Compared with the above results, it can be seen that both the alkali treatment and the strong electrostatic adsorption method can improve the average propane conversion and the average propylene selectivity of the catalyst, but the former has a greater contribution to the average propane conversion and the average propylene selectivity.

[0178] It can also be seen from Table 1 that when the alkali treatment solution is a sodium hydroxide aqueous solution, the average propane conversion and the average propylene selectivity of the catalyst prepared by using the sodium hydroxide aqueous solution with a concentration of 0.05 mol / L in Example 1 of the present application are as high as 57% and 98%, respectively, while the average propane conversion and the average propylene selectivity of the catalyst prepared by using the sodium hydroxide aqueous 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 solution will affect the activity and selectivity of the prepared catalyst, and when the alkali treatment solution is a sodium hydroxide aqueous solution, the concentration thereof should be in the range of 0.01-0.3 mol / L to achieve the purpose of the present application and obtain the beneficial technical effects as shown above.

[0179] It can also be seen from Table 1 that the pH value of the system during the preparation of the catalyst by the strong electrostatic adsorption method in Comparative Example 1 is only 9, and the average propane conversion and the average propylene selectivity of the catalyst prepared thereby are only 53% and 97%, respectively, while the pH value of the system during the preparation of the catalyst by the strong electrostatic adsorption method in Example 1 of the present application is controlled to 11, and the average propane conversion and the average propylene selectivity of the catalyst prepared thereby are both improved, and can reach 57% and 98%, respectively, which indicates 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, and the pH value should be in the range of 10.5-11.5 to achieve the purpose of the present application and obtain the beneficial technical effects as shown above.

[0180] The above description is only specific embodiments of the present application, and cannot limit the scope of the present application, so that the replacement of equivalent components or equivalent changes and modifications made within the scope of the patent protection of the present application should still belong to the scope covered by the present patent. In addition, the technical features in the present application, between technical features, between technical features and technical inventions, and between technical inventions can be freely combined.

Claims

1. A method for preparing a propane dehydrogenation catalyst, characterized in that, The preparation method includes: Step (1): After treating the pure silica molecular sieve Silicalite-1 with an alkaline solution, the alkaline treatment product is subjected to ion exchange with ammonium salt. The ion-exchange product is then dried and calcined to obtain a multi-level porous molecular sieve with hydrogen-type mesoporous and microporous structures. The concentration of the alkaline treatment solution is 0.01-1 mol / L, and the mass ratio of the pure silica molecular sieve Silicalite-1 to the alkaline treatment solution is 1:5-15. When the alkaline treatment solution is an aqueous solution of sodium hydroxide, its concentration is 0.01-0.3 mol / L. Step (2): The cobalt salt and hydrogen-type mesoporous composite hierarchical porous molecular sieve are fully dissolved in an ammonia solution, and the pH value of the system is adjusted so that cobalt ions are adsorbed on the surface of the hydrogen-type mesoporous composite hierarchical porous molecular sieve and enter the cavities of its framework. The resulting solid precipitate is then dried and calcined to obtain the propane dehydrogenation catalyst. In step (2), the pH value of the system is adjusted to 10.5-11.

5.

2. The preparation method according to claim 1, characterized in that, The propane dehydrogenation catalyst comprises a hydrogen-type mesoporous-microporous composite hierarchical porous molecular sieve support and a cobalt active component. A portion of the cobalt active component is supported on the surface of the hydrogen-type mesoporous-microporous composite hierarchical porous molecular sieve support in the form of CoO nanoparticles, while another portion of the cobalt active component enters the framework of the hydrogen-type mesoporous-microporous composite hierarchical porous molecular sieve support by forming chemical bonds and forming CoO nanoparticles. 2+ -O-Si structure; The cobalt active component, calculated as cobalt element, is 0.1-7 wt% based on the total weight of the hydrogen-type mesoporous microporous composite hierarchical porous molecular sieve support (100%).

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

4. The preparation method according to any one of claims 1-3, characterized in that, The alkaline treatment solution includes an aqueous solution of sodium hydroxide, an aqueous solution of tetrapropylammonium hydroxide, or an aqueous solution of tetraethylammonium hydroxide.

5. The preparation method according to any one of claims 1-3, characterized in that, The alkaline treatment is performed at a temperature of room temperature to 100°C for 1-6 hours.

6. The preparation method according to any one of claims 1-3, characterized in that, In step (1), the temperature of ion exchange is not higher than 100℃.

7. The preparation method according to any one of claims 1-3, characterized in that, In steps (1) and (2), the drying temperature is 60-120°C.

8. The preparation method according to any one of claims 1-3, characterized in that, In steps (1) and (2), the calcination is to raise the temperature from room temperature to 500-600℃ at a heating rate of 0.5-5℃ / min and hold it for 2-8 hours.

9. The preparation method according to any one of claims 1-3, characterized in that, Step (2) specifically includes first dissolving the cobalt salt in an ammonia solution and adjusting the pH of the system to 10.5-11.5, then adding a multi-level porous molecular sieve of hydrogen-type mesoporous microporous composite and dissolving it completely, then adjusting the pH of the system to 10.5-11.5 again, and then drying and calcining the obtained solid precipitate to obtain the propane dehydrogenation catalyst.

10. The preparation method according to claim 1, characterized in that, The cobalt salt includes one or a combination of several of the following: cobalt nitrate hexahydrate, cobalt chloride hexahydrate, cobalt acetate, cobalt carbonyl, Co-EDTA complex, and cobalt acetylacetonate complex.

11. The preparation method according to claim 1 or 10, characterized in that, The mass concentration of the ammonia solution is 1-2%.

12. The application of the propane dehydrogenation catalyst prepared by the method of any one of claims 1-11 in the production of propylene from propane dehydrogenation.

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