Linear alkane dehydrogenation catalyst and linear alkane dehydrogenation process

Abstract

This invention discloses a catalyst and method for dehydrogenating straight-chain alkanes. The catalyst comprises a support complex and a dehydrogenation active component supported on the support complex. The support complex includes Al and a Group IVB metal element. The physicochemical characteristics of the support complex include a particle size distribution range of 3-35 micrometers based on Dx(50), and the dehydrogenation active component element is selected from Group IVB metal elements. The catalyst of this invention is used for the dehydrogenation of straight-chain alkanes, particularly in the dehydrogenation conversion of C6-C13 straight-chain alkanes, at a reaction temperature of 400-500°C, a reaction pressure of 0.1-3 MPa, and a liquid hourly space velocity of 5-30 h⁻¹. ‑1 Under certain conditions, contact occurs, resulting in a dehydrogenation reaction with a selectivity of over 89%.

Description

Technical Field

[0001] This invention relates to catalysts and methods for the dehydrogenation of straight-chain alkanes. Background Technology

[0002] Linear-chain olefins with 6, especially 9 or more carbon atoms, are very economical compounds and are widely used as basic materials for intermediates in the preparation of biodegradable detergents, pharmaceuticals, plastics, and synthetic rubber. Linear-chain alkanes with 6-13 or more carbon atoms can be converted into corresponding linear olefins through dehydrogenation. In this process, hydrogen and the gasified linear-chain alkane are contacted with a dehydrogenation catalyst, followed by reaction at high temperature and pressure. During the dehydrogenation reaction, it is necessary to increase the reaction rate of the feedstock to suppress side reactions such as cracking, coke formation, and isomerization, thereby increasing the selectivity of linear olefins.

[0003] Currently, the catalysts used for the dehydrogenation of straight-chain alkanes to produce straight-chain olefins, and subsequently alkylbenzenes, are primarily noble metal catalysts. These catalysts for straight-chain alkane dehydrogenation reactions use platinum group metals as the active component, some metals from Group III, Group V, and Group VI as the secondary active component, and alkali metals and alkaline earth metals as promoters. Furthermore, these straight-chain alkane dehydrogenation reactions require catalysts with large pore sizes and high porosity to facilitate internal diffusion of reactants and thus fully utilize the active component.

[0004] CN1017779B proposes a solid, particulate, porous support as a dehydrogenation catalyst, on which 0.05% to 1% by weight of platinum, 0.1% to 1% by weight of tin, and 0% to 1% by weight of an alkali metal are deposited. When a mixed gas stream of straight-chain alkanes and hydrogen is introduced into the reactor at a molar ratio of 1:1 to 15:1 and the reaction is carried out at 400–550 °C, the conversion rate of straight-chain alkanes reaches a maximum of 18.5%, and the selectivity reaches a maximum of 90%.

[0005] CN87101513A discloses a catalyst for the dehydrogenation of saturated hydrocarbons. In its preparation, an aqueous solution of aluminum trichloride is used. At a temperature of 60℃~80℃, the solution is first neutralized with ammonia to a pH of 7.5~8.5. The resulting aluminum hydroxide slurry is washed with water, acidified, and then pelletized in an oil-ammonia column. After drying and calcination, alumina microspheres are formed. These microspheres are then subjected to steam treatment to obtain a macroporous catalyst support. Finally, platinum, tin, lithium, and other active components are impregnated using a co-impregnation method to obtain the final catalyst sample. However, this process involves large equipment investment, easy loss of alkali metals, and the preparation process produces corrosive and toxic liquids that pollute the environment.

[0006] CN102441378A discloses a dehydrogenation catalyst for straight-chain alkanes, particularly for C6-C6 hydrocarbons. 30A catalyst for the dehydrogenation of straight-chain alkanes to monoolefins is presented. This catalyst not only has a simple preparation process but also possesses a large specific surface area and pore volume. The reaction conditions are: gauge pressure 1.0 MPa, inlet temperature 480 °C, and liquid hourly space velocity 20 h⁻¹. -1 Under a hydrogen / alkane molar ratio of 5:1, the dehydrogenation catalyst achieves a maximum alkane conversion rate of 19.3% and an olefin selectivity of 94%. However, due to the large amount of hydrogen required, the operation is complex and expensive.

[0007] As can be seen from the publicly available technologies, although existing precious metal catalysts have been improved and optimized to varying degrees, their conversion rate for straight-chain alkanes is still low, and the improvement effect has not reached the expected goal. Summary of the Invention

[0008] The purpose of this invention is to overcome the problem of low selectivity of existing straight-chain alkane dehydrogenation catalysts and to provide a novel straight-chain alkane dehydrogenation catalyst with advantages such as good olefin selectivity.

[0009] According to a first aspect of the present invention, the present invention provides a straight-chain alkane dehydrogenation catalyst, the catalyst comprising: a support complex and a dehydrogenation active component supported on the support complex, the support complex comprising Al and a Group IVB metal element, the physicochemical characteristics of the support complex comprising: a particle size distribution range of 3-35 micrometers based on Dx(50), and the dehydrogenation active component element selected from Group IVB metal elements.

[0010] According to a second aspect of the present invention, the present invention provides a method for dehydrogenating straight-chain alkanes, the method comprising: carrying out a dehydrogenation reaction of straight-chain alkanes in the presence of a catalyst, said catalyst comprising the straight-chain alkane dehydrogenation catalyst of the present invention;

[0011] Preferably, the conditions for the dehydrogenation reaction include: a reaction temperature of 400-500℃, a reaction pressure of 0.1-3 MPa, and a liquid hourly space velocity (LISH) of 5-30 h⁻¹ for straight-chain alkanes. -1 ;

[0012] Preferably, the straight-chain alkane is a C6-C13 alkane, and more preferably a C6 alkane.

[0013] The support of this invention has advantages such as excellent particle size distribution and a specific Theta alumina crystal form. The catalyst of this invention has high olefin selectivity.

[0014] The catalyst of this invention is used for the dehydrogenation of straight-chain alkanes, particularly the dehydrogenation conversion of C6 alkanes, at a reaction temperature of 400–500 °C, a reaction pressure of 0.1–3 MPa, and a liquid hourly space velocity of 5–30 h⁻¹. -1 Under certain conditions, contact occurs, resulting in a dehydrogenation reaction with an olefin selectivity of over 89%. Detailed Implementation

[0015] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0016] This invention provides a straight-chain alkane dehydrogenation catalyst, comprising: a support composite and a dehydrogenation active component supported on the support composite. The support composite comprises Al and a Group IVB metal element. The physicochemical characteristics of the support composite include: a particle size distribution range of 3-35 micrometers based on Dx(50), and the dehydrogenation active component element selected from Group IVB metal elements. The novel composite support of this invention, after loading the active component, gives the catalyst advantages such as high activity and good stability.

[0017] In this invention, the range of types of dehydrogenation active components is relatively wide. This invention is described exemplarily, but does not limit the scope of the invention. Preferably, the dehydrogenation active component element is selected from one or more of Cr, Mo, and W, and more preferably Cr.

[0018] In this invention, the amount of dehydrogenation active component can be selected from a wide range, and commonly used amounts can be applied to this invention. For this invention, it is preferred that the elemental content of the dehydrogenation active component, based on the total weight of the catalyst, is 5-25%, preferably 10-20%.

[0019] According to a preferred embodiment of the present invention, the dehydrogenation catalyst further comprises: an alkali metal promoter, based on the total weight of the catalyst, having an elemental content of 0.1-5%, preferably 0.3-2.5%, more preferably 0.3-0.8%.

[0020] According to a preferred embodiment of the present invention, preferably, the alkali metal auxiliary is selected from at least one of Li, Na, K, and Cs, preferably Na and / or K, more preferably Na and K; more preferably a mixture of Na and K, wherein the content of one of them is not less than 10% by weight; more preferably, the weight ratio of Na to K is 0.7-0.9:1.

[0021] In this invention, the mass ratio of the group IVB metal element to Al can be selected within a wide range. This is an illustrative example, but does not limit the scope of the invention. According to a preferred embodiment of the invention, the molar ratio of the group IVB metal element to Al is 0.003 to 0.1, preferably 0.009 to 0.08, and more preferably 0.01 to 0.04.

[0022] According to the present invention, the carrier composite contains oxygen, and the group IVB metal element and Al exist in the carrier composite in an oxidized form.

[0023] According to a preferred embodiment of the present invention, the carrier composite has a particle size distribution of 5-20 micrometers, calculated as Dx(50).

[0024] According to a preferred embodiment of the present invention, the alumina in the carrier composite has a Theta crystal structure, and the content of Theta phase alumina (θ-Al2O3) ranges from 30% to 60% based on the total weight of alumina.

[0025] In this invention, the Group IVB metal element is selected from one or more of Ti, Zr, and Hf, preferably Zr. Other elements may also be introduced as needed.

[0026] According to a preferred embodiment of the present invention, the alumina in the carrier composite has a Theta crystal structure, and the content of Theta phase alumina is 10-65% by weight of the total alumina, preferably 10-60%.

[0027] According to a preferred embodiment of the present invention, the grain size in the Theta phase alumina is relatively narrow, concentrated in the range of 5–20 nm, preferably 7–18 nm.

[0028] All carriers possessing the characteristics of this invention can achieve the objectives of this invention, and there are no special requirements for their preparation methods. According to one embodiment of this invention, the preparation method of the carrier composite includes: I) forming an alkaline solution with an Al source and a Group IVB metal element source; II) adding alumina and aging; then separating the solid and liquid phases, drying, and calcining. Using the aforementioned preferred preparation method, a carrier composite possessing the characteristics and advantages of this invention can be synthesized.

[0029] In this invention, the proportion of each material in step I) can be selected within a wide range. The following is an illustrative description, but it does not limit the scope of this invention. According to a preferred embodiment of this invention, the molar ratio of Al source: Group IVB metal source: deionized water: alkali is (10-100): 1: (10-500): (30-80).

[0030] In this invention, the content of deionized water includes the amount introduced alone or along with other raw materials. This is known to those skilled in the art.

[0031] In this invention, the alkaline solution only needs to meet the alkalinity requirement; there are no special requirements for its alkalinity value.

[0032] In this invention, there are no special requirements for the type of Al source; various substances are applicable to this invention, such as water-soluble aluminum sources. The following is an illustrative description, but it does not limit the scope of this invention. According to one embodiment of this invention, the Al source includes one or more of aluminum nitrate nonahydrate, aluminum sulfate, aluminum isopropoxide, and aluminum sol.

[0033] In this invention, there are no special requirements for the type of Group IVB metal source, and various substances are applicable to this invention. The following is an illustrative description, but it does not limit the scope of this invention. According to one embodiment of this invention, the Group IVB metal source is selected from Group IVB metal source soluble compounds, preferably selected from Group IVB metal source soluble salts. When it is Zr, it is preferably zirconium nitrate hexahydrate and / or zirconium oxychloride octahydrate.

[0034] In this invention, the range of base substances that can be selected is relatively wide, and commonly used bases can be applied to this invention. The following is an illustrative description of this invention, but it does not limit the scope of this invention. Preferably, the base is selected from organic amines and / or inorganic ammonia.

[0035] In this invention, the range of types of organic amines that can be selected is relatively wide. Commonly used organic amines can all be used in this invention, such as ethylamine, propylamine, dimethylamine, ethylenediamine, dipropylamine, butylamine, diethylamine, diisopropylamine, hexamethylenediamine, monoethanolamine, diethanolamine, triethanolamine, 3-propanolamine, monoisopropanolamine, diisopropanolamine, triisopropanolamine, 1,2-dimethylpropylamine, sec-butylamine, ethylenediamine, 1,2-propanediamine, 1,4-butanediamine, tetramethylammonium hydroxide, tetraethylammonium hydroxide, and tetrapropylammonium hydroxide, or one or more of these.

[0036] In this invention, the step of mixing the Al source and the Group IVB metal source to form an alkaline solution has no special requirements; the main purpose is to achieve uniform mixing. For example, appropriate heating or dropwise addition can be used to achieve uniform mixing. The following is an illustrative description, but it does not limit the scope of the invention. The mixing step includes:

[0037] i) Under conditions of 20-50℃, such as 20℃, 25℃, 30℃, 35℃, 40℃, 45℃, and 50℃, add aluminum source and zirconium source to deionized water in proportion and stir thoroughly to dissolve;

[0038] ii) Add an alkaline solution dropwise to the solution obtained in step i), and continue stirring for 1-3 hours after adding the solution, for example, 1 hour, 2 hours, or 3 hours.

[0039] In this invention, there are no special requirements for the source of alumina. For this invention, it is preferred that the alumina be small-pore alumina, preferably with a pore size of 0.1-5 μm, and more preferably 0.5-1 μm.

[0040] In this invention, the morphology of the alumina is preferred and there are no special requirements; for example, it can be γ-alumina.

[0041] This allows for the further optimization of the performance of the obtained composite carrier.

[0042] In this invention, the range of selectable amounts of alumina is relatively wide. This is an illustrative example, but it does not limit the scope of the invention. For this invention, the preferred amount of alumina is: based on the total molar amount of aluminum in the catalyst, the molar amount of alumina, calculated as aluminum element, is 1 to 60%, preferably 8 to 50%.

[0043] In this invention, there are no special requirements for aging conditions, but preferred aging conditions include: standing for 6-24 hours, for example, 6 hours, 8 hours, 10 hours, 12 hours, 14 hours, 16 hours, 18 hours, 20 hours, 22 hours, and 24 hours.

[0044] According to a preferred embodiment of the present invention, the aging is preferably carried out in the presence of polyallyl alcohol with an average molecular weight of 200-2500, preferably 400-1025, and the amount of polyallyl alcohol used is 0.1-5% based on the total weight of the aging solution. In the examples, an average molecular weight of 1025 is used as an example, and the amount added is 0.5% of the solution weight, but this does not limit the scope of the present invention.

[0045] In this invention, there are no special requirements for the drying and calcination conditions. The following is an illustrative description, but it does not limit the scope of the invention.

[0046] According to one embodiment of the present invention, the drying conditions include: a temperature of 80-120°C and a time of 12-24 hours, for example, 12 hours, 14 hours, 16 hours, 18 hours, 20 hours, or 24 hours.

[0047] According to a preferred embodiment of the present invention, the calcination conditions include: a temperature of 500-750°C, for example, 500°C, 550°C, 600°C, 650°C, 700°C, and 750°C; and a time of 2-12 hours, for example, 2 hours, 4 hours, 6 hours, 8 hours, 10 hours, and 12 hours.

[0048] According to a preferred embodiment of the present invention, the method includes:

[0049] i) Under conditions of 20-50℃, such as 20℃, 25℃, 30℃, 35℃, 40℃, 45℃, and 50℃, add aluminum source and zirconium source to deionized water in proportion and stir thoroughly to dissolve;

[0050] ii) Add an alkaline solution dropwise to the solution obtained in step i), and continue stirring for 1-3 hours after adding the solution, for example, 1 hour, 2 hours, or 3 hours;

[0051] iii) Add aluminum oxide to the solution in step ii) in proportion, continue stirring for 2-6 hours, for example 2 hours, 4 hours, 6 hours, and let stand and age for 6-24 hours, for example 6 hours, 8 hours, 10 hours, 12 hours, 14 hours, 16 hours, 18 hours, 20 hours, 22 hours, 24 hours;

[0052] iiii) Pour the precipitate obtained in step iii) into a centrifuge, centrifuge, wash with deionized water more than three times, dry the filter cake at 80-120℃ for 12-24h, and then calcine at 500-750℃ for 2-12h.

[0053] According to a preferred embodiment of the present invention, in step iii), polyallyl alcohol with a molecular weight of 200-2500, preferably 400-1025, is added, and the amount of polyallyl alcohol is 0.1-5% based on the total weight of the solution.

[0054] The carrier prepared using the aforementioned preferred embodiments exhibits the best performance.

[0055] This invention does not impose any special requirements on the preparation method of the catalyst. Instead, this invention provides a method for preparing the dehydrogenation catalyst, which includes:

[0056] (1) Prepare the carrier complex according to the method of the present invention;

[0057] (2) The dehydrogenation active component source, optionally an alkali metal auxiliary source, is loaded onto the carrier composite by impregnation, followed by drying and calcination.

[0058] In this invention, there are no special requirements for the impregnation method. The impregnation method is an equal-volume impregnation method. Preferably, the equal-volume impregnation is performed by spraying.

[0059] In this invention, there are no special requirements for the drying and calcination conditions. The following is an illustrative description, but it does not limit the scope of the invention.

[0060] According to one embodiment of the present invention, the drying conditions include a temperature of 80-120°C and a time of 12-24 hours.

[0061] According to a preferred embodiment of the present invention, the calcination conditions include: a temperature of 500-750°C and a time of 2-12 hours.

[0062] The dehydrogenation catalyst of the present invention has good activity and is particularly suitable for the dehydrogenation of straight alkanes.

[0063] This invention provides a method for dehydrogenating straight-chain alkanes, the method comprising: carrying out a dehydrogenation reaction of straight-chain alkanes in the presence of a catalyst, wherein the catalyst comprises the dehydrogenation catalyst described in this invention.

[0064] In this invention, there are no special requirements for the dehydrogenation reaction conditions. The following is an illustrative description, but it does not limit the scope of the invention.

[0065] According to one embodiment of the present invention, preferably, the conditions for the dehydrogenation reaction include: a reaction temperature of 400-500°C, a reaction pressure of 0.1-3 MPa, and a liquid hourly space velocity (LISH) of 5-30 h⁻¹ for straight-chain alkanes. -1 .

[0066] The dehydrogenation reaction of the present invention is suitable for the dehydrogenation of various straight-chain alkanes, such as C6-C13 alkanes, preferably C6 alkanes, and more preferably n-hexane.

[0067] This invention does not impose special requirements on the reactor used for the dehydrogenation reaction. For example, an isothermal bed reactor can be used, such as a quartz tube with an inner diameter of Ф10mm, an outer diameter of Ф16mm, and a length of 600mm. The raw material is fed into a preheating zone for preheating and vaporization by adjusting the flow rate using a liquid mass flow meter, and then into the reaction zone for premixing with hydrogen. Both the heating and reaction sections of the reactor are heated by electric heating wires. After the reaction, the material passes through a condenser and is then analyzed by liquid chromatography. Simultaneously, a heating coupler can be installed in the middle of the catalyst bed to monitor temperature changes during the reaction in real time.

[0068] The present invention will be described in detail below through examples. In the following examples, the particle size distribution of the bimetallic oxide support was obtained by dry testing using a Malvern particle size analyzer, the crystal form of the bimetallic oxide support was obtained by XRD analysis combined with the instrument configuration identification software TOPAS, and the average pore size distribution of the oxide was obtained by the BET method. All of these are well known techniques in the art and will not be described in detail in the present invention. All raw materials used are commercially available analytical grade products from China National Pharmaceutical Group.

[0069] In this invention, the method for testing the grain size in Theta phase alumina is to import the XRD spectrum of the test sample into the TOPAS software, set the grain parameters of the phase, perform spectrum identification, ensure that the set parameters coincide with the actual spectrum, and run the software after confirming that there are no errors to obtain the grain size.

[0070] In this invention, the method for testing the content of Theta phase alumina is to import the XRD spectrum of the test sample into the TOPAS software, set the calculation parameters of Theta phase, make the fitted spectrum coincide with the actual spectrum, and after confirming that there are no errors, run the software to obtain the proportion of Theta phase in the sample.

[0071] In the embodiments and comparative examples of the present invention,

[0072] Conversion rate of straight-chain alkanes (%) = (mass of straight-chain alkanes in reactants - mass of straight-chain alkanes in reaction products) ÷ mass of straight-chain alkanes in reactants × 100%;

[0073] Olefin selectivity (%) = Actual yield of olefins ÷ Theoretical yield of olefins × 100%, by mass.

[0074] In the embodiments and comparative examples of this invention, the analysis of the gas composition in the dehydrogenation reaction was performed on a gas chromatograph, model 7890A, purchased from Agilent Technologies.

[0075] The particle size of ZrO2-Al2O3 support was analyzed using a Malvern 3000 particle size analyzer. The test method is as follows: First, the particle size analyzer was cleaned, the test parameters were set, the Venturi tube was set according to the standard value, the test pressure was 2 bar, the test powder was added, the file name was set, and the test was started. The instrument automatically completed the background scan and three parallel tests of the powder. After the test, the test data was processed through the editing option to obtain the Dx(50) particle size of the composite oxide support.

[0076] The catalysts used in the following examples and comparative examples were used for dehydrogenation reactions: 10 grams of dehydrogenation catalyst were weighed and placed in an isothermal bed reactor, which consisted of a quartz tube with an inner diameter of Ф10 mm, an outer diameter of Ф16 mm, and a length of 600 mm. Hexane was introduced into the preheating zone for preheating and vaporization using a liquid mass flow meter, and then premixed with hydrogen in the reaction zone. Both the heating and reaction sections of the reactor were heated by heating wires to reach 450°C, under atmospheric pressure and a liquid hourly space velocity of 15 h⁻¹. -1 After reacting for 1 hour under the specified conditions, the material was condensed and then analyzed by liquid chromatography. A heating coupler was placed in the middle of the catalyst bed to monitor the temperature changes during the reaction in real time.

[0077] Example 1

[0078] Preparation of the carrier complex:

[0079] Weigh 75g of aluminum nitrate nonahydrate, 3.4g of zirconium nitrate, 18g of deionized water, and 10.2g of ammonia (25wt%).

[0080] At 30°C, aluminum nitrate and zirconium nitrate were dissolved in deionized water and stirred thoroughly until dissolved; ammonia water was slowly added dropwise while stirring for 2 hours.

[0081] Then slowly add 5 grams of γ-alumina with a pore size distribution of 0.5-1 micrometer, continue stirring for 3 hours, and let stand for 12 hours to age; put the sol into a 50-liter centrifuge for filtration, wash it three times with deionized water, transfer it to an oven and dry it at 80℃ for 12 hours, and then put it into a muffle furnace and calcine it at 600℃ for 4 hours to obtain an Al2O3 composite oxide carrier. The Dx(50) particle size of the composite oxide carrier is 7.2 micrometers, which contains 35% θ-Al2O3 by weight of alumina, and the θ-Al2O3 crystal size is 7.8 nm.

[0082] Preparation of dehydrogenation catalysts:

[0083] Weigh 15.8 g of chromium nitrate and 0.33 g of sodium nitrate, dissolve them in 10 g of deionized water to obtain a solution containing the active components. Add the solution to 20 g of composite alumina support to ensure full contact, then dry it in an oven at 80 °C for 12 h, and then calcine it in a muffle furnace at 600 °C for 4 h to obtain the catalyst sample. The results are shown in Table 1.

[0084] Performance evaluation:

[0085] For the dehydrogenation reaction: Weigh 10 grams of dehydrogenation catalyst and place it in an isothermal bed reactor, which is a 600 mm long quartz tube with an inner diameter of Ф10 mm and an outer diameter of Ф16 mm. Adjust the flow rate of n-hexane using a liquid mass flow meter, and introduce it into the preheating zone for preheating and vaporization. Then, it enters the reaction zone and is premixed with hydrogen. Both the heating and reaction sections of the reactor are heated by electric heating wires to reach 450 °C, under atmospheric pressure and a liquid hourly space velocity of 15 h⁻¹. -1 After reacting for 1 hour under the specified conditions, the material was condensed and then analyzed by liquid chromatography. A heating coupler was placed in the middle of the catalyst bed to monitor the temperature changes during the reaction in real time.

[0086] Comparative Example 1

[0087] When preparing the carrier composite, no porous alumina was added, and the amount of aluminum source aluminum nitrate nonahydrate was increased so that the carrier was calculated as aluminum and the amount was the same as in Example 1. The other components, contents and preparation process were the same as in Example 1. The resulting carrier Dx(50) had a particle size distribution of 40 micrometers. The results are shown in Table 1.

[0088] Performance evaluation:

[0089] For the dehydrogenation reaction: Weigh 10 grams of dehydrogenation catalyst and place it in an isothermal bed reactor, which is a 600 mm long quartz tube with an inner diameter of Ф10 mm and an outer diameter of Ф16 mm. Adjust the flow rate of n-hexane using a liquid mass flow meter, and introduce it into the preheating zone for preheating and vaporization. Then, it enters the reaction zone and is premixed with hydrogen. Both the heating and reaction sections of the reactor are heated by electric heating wires to reach 450 °C, under atmospheric pressure and a liquid hourly space velocity of 15 h⁻¹. -1 After reacting for 1 hour under the specified conditions, the material was condensed and then analyzed by liquid chromatography. A heating coupler was placed in the middle of the catalyst bed to monitor the temperature changes during the reaction in real time.

[0090] Example 2

[0091] The method is the same as in Example 1, except that the preparation steps of the carrier are as follows:

[0092] Weigh 225.1 g of aluminum nitrate nonahydrate, 3.4 g of zirconium nitrate, 36 g of deionized water and 52 g of ammonia water (concentration 25 wt%).

[0093] At 30°C, aluminum nitrate and zirconium nitrate were dissolved in deionized water and stirred thoroughly until dissolved; ammonia water was slowly added dropwise while stirring for 1 hour.

[0094] Then slowly add 5 grams of alumina with a pore size distribution of 0.5-1 micrometer, continue stirring for 4 hours, and let it stand for 12 hours to age. Filter the sol in a 50-liter centrifuge, wash it three times with deionized water, transfer it to an oven and dry it at 80℃ for 12 hours, and then calcine it in a muffle furnace at 650℃ for 4 hours to obtain the Al2O3 composite oxide carrier.

[0095] The composite oxide carrier has a Dx(50) particle size of 16 micrometers, of which θ-Al2O3 accounts for 45% of the total weight of alumina and the θ-Al2O3 grain size is 8.2 nm.

[0096] The catalyst preparation process was the same as in Example 1, and the results are shown in Table 1.

[0097] Performance evaluation:

[0098] For the dehydrogenation reaction: Weigh 10 grams of dehydrogenation catalyst and place it in an isothermal bed reactor, which is a 600mm long quartz tube with an inner diameter of Ф10mm and an outer diameter of Ф16mm. Adjust the flow rate of n-hexane using a liquid mass flow meter, and introduce it into the preheating zone for preheating and vaporization. Then, it enters the reaction zone and is premixed with hydrogen. Both the heating and reaction sections of the reactor are heated by electric heating wires to reach 450℃, under atmospheric pressure and a liquid hourly space velocity of 15h⁻¹. -1 After reacting for 1 hour under the specified conditions, the material was condensed and then analyzed by liquid chromatography. A heating coupler was placed in the middle of the catalyst bed to monitor the temperature changes during the reaction in real time.

[0099] Example 3

[0100] The method is the same as in Example 1, except that the preparation steps of the carrier are as follows:

[0101] Weigh 375.1 g of aluminum nitrate nonahydrate, 3.4 g of zirconium nitrate, 54 g of deionized water, and 31.5 g of ammonia (25 wt%).

[0102] At 30°C, aluminum nitrate and zirconium nitrate are dissolved in deionized water and stirred thoroughly until dissolved.

[0103] In the subsequent preparation process, the standing time was increased to 24 hours, while the calcination temperature was 620℃ and the calcination time was 6 hours, with other parameters remaining unchanged.

[0104] The obtained composite oxide support has a Dx(50) particle size of 11 micrometers, of which θ-Al2O3 accounts for 58% of the total weight of alumina and the θ-Al2O3 grain size is 9.5 nm.

[0105] The catalyst preparation process was the same as in Example 1, and the results are shown in Table 1.

[0106] Performance evaluation:

[0107] For the dehydrogenation reaction: Weigh 10 grams of dehydrogenation catalyst and place it in an isothermal bed reactor, which is a 600mm long quartz tube with an inner diameter of Ф10mm and an outer diameter of Ф16mm. Adjust the flow rate of n-hexane using a liquid mass flow meter, and introduce it into the preheating zone for preheating and vaporization. Then, it enters the reaction zone and is premixed with hydrogen. Both the heating and reaction sections of the reactor are heated by electric heating wires to reach 450℃, under atmospheric pressure and a liquid hourly space velocity of 15h⁻¹. -1 After reacting for 1 hour under the specified conditions, the material was condensed and then analyzed by liquid chromatography. A heating coupler was placed in the middle of the catalyst bed to monitor the temperature changes during the reaction in real time.

[0108] Example 4

[0109] The method of Example 1 was followed, except that 5 grams of alumina with a pore size of 1-2 micrometers was added to the aging step, and the other conditions were the same, resulting in a composite oxide carrier with a Dx(50) particle size of 14 micrometers. The θ-Al2O3 accounted for 40% of the total weight of alumina, and the θ-Al2O3 crystal size was 11.5 nm.

[0110] The catalyst preparation process was the same as in Example 1, and the results are shown in Table 1.

[0111] Performance evaluation:

[0112] For the dehydrogenation reaction: Weigh 10 grams of dehydrogenation catalyst and place it in an isothermal bed reactor, which is a 600mm long quartz tube with an inner diameter of Ф10mm and an outer diameter of Ф16mm. Adjust the flow rate of n-hexane using a liquid mass flow meter, and introduce it into the preheating zone for preheating and vaporization. Then, it enters the reaction zone and is premixed with hydrogen. Both the heating and reaction sections of the reactor are heated by electric heating wires to reach 450℃, under atmospheric pressure and a liquid hourly space velocity of 15h⁻¹. -1 After reacting for 1 hour under the specified conditions, the material was condensed and then analyzed by liquid chromatography. A heating coupler was placed in the middle of the catalyst bed to monitor the temperature changes during the reaction in real time.

[0113] Example 5

[0114] The method of Example 1 was followed, except that the amount of alumina used was 10 grams, while other conditions remained unchanged. The resulting composite oxide support had a Dx(50) particle size of 12.5 micrometers, of which θ-Al2O3 accounted for 43% by weight of the total alumina, and the θ-Al2O3 grain size was 8.5 nm.

[0115] The catalyst preparation process was the same as in Example 1, and the results are shown in Table 1.

[0116] Performance evaluation:

[0117] For the dehydrogenation reaction: Weigh 10 grams of dehydrogenation catalyst and place it in an isothermal bed reactor, which is a 600 mm long quartz tube with an inner diameter of Ф10 mm and an outer diameter of Ф16 mm. Adjust the flow rate of n-hexane using a liquid mass flow meter, and introduce it into the preheating zone for preheating and vaporization. Then, it enters the reaction zone and is premixed with hydrogen. Both the heating and reaction sections of the reactor are heated by electric heating wires to reach 450 °C, under atmospheric pressure and a liquid hourly space velocity of 15 h⁻¹. -1 After reacting for 1 hour under the specified conditions, the material was condensed and then analyzed by liquid chromatography. A heating coupler was placed in the middle of the catalyst bed to monitor the temperature changes during the reaction in real time.

[0118] Example 6

[0119] The method of Example 1 was followed, except that the amounts of each substance were as follows: 750.3 g of aluminum nitrate nonahydrate, 3.4 g of zirconium nitrate, 36 g of deionized water, and 52.6 g of ammonia (concentration of 25 wt%) were weighed. The preparation conditions remained unchanged, and the resulting composite oxide support had a Dx(50) particle size of 20 micrometers, of which θ-Al2O3 accounted for 25% of the total weight of aluminum oxide and had a grain size of 5.8 nm.

[0120] The catalyst preparation process was the same as in Example 1, and the results are shown in Table 1.

[0121] Performance evaluation:

[0122] For the dehydrogenation reaction: Weigh 10 grams of dehydrogenation catalyst and place it in an isothermal bed reactor, which is a 600 mm long quartz tube with an inner diameter of Ф10 mm and an outer diameter of Ф16 mm. Adjust the flow rate of n-hexane using a liquid mass flow meter, and introduce it into the preheating zone for preheating and vaporization. Then, it enters the reaction zone and is premixed with hydrogen. Both the heating and reaction sections of the reactor are heated by electric heating wires to reach 450 °C, under atmospheric pressure and a liquid hourly space velocity of 15 h⁻¹. -1 After reacting for 1 hour under the specified conditions, the material was condensed and then analyzed by liquid chromatography. A heating coupler was placed in the middle of the catalyst bed to monitor the temperature changes during the reaction in real time.

[0123] Example 7

[0124] The method of Example 1 was followed, except that the composite oxide carrier was left to stand for 72 hours and the other conditions were the same. The particle size of Dx(50) was 27 micrometers, of which θ-Al2O3 accounted for 65% of the total weight of alumina and the grain size was 10.6 nm.

[0125] The catalyst preparation process was the same as in Example 1, and the results are shown in Table 1.

[0126] Performance evaluation:

[0127] For the dehydrogenation reaction: Weigh 10 grams of dehydrogenation catalyst and place it in an isothermal bed reactor, which is a 600 mm long quartz tube with an inner diameter of Ф10 mm and an outer diameter of Ф16 mm. Adjust the flow rate of n-hexane using a liquid mass flow meter, and introduce it into the preheating zone for preheating and vaporization. Then, it enters the reaction zone and is premixed with hydrogen. Both the heating and reaction sections of the reactor are heated by electric heating wires to reach 450 °C, under atmospheric pressure and a liquid hourly space velocity of 15 h⁻¹. -1 After reacting for 1 hour under the specified conditions, the material was condensed and then analyzed by liquid chromatography. A heating coupler was placed in the middle of the catalyst bed to monitor the temperature changes during the reaction in real time.

[0128] Example 8

[0129] The method of Example 1 was followed, except that 0.5% of polyallyl alcohol with an average molecular weight of 1025 (added together with γ-alumina) was added to the aging solution by weight of the solution. Other conditions were the same, and the resulting composite oxide carrier had a Dx(50) particle size of 34 micrometers, of which θ-Al2O3 accounted for 10% of the total weight of alumina and the grain size was 18 nm.

[0130] The catalyst preparation process was the same as in Example 1, and the results are shown in Table 1.

[0131] Performance evaluation:

[0132] For the dehydrogenation reaction: Weigh 10 grams of dehydrogenation catalyst and place it in an isothermal bed reactor, which is a 600 mm long quartz tube with an inner diameter of Ф10 mm and an outer diameter of Ф16 mm. Adjust the flow rate of n-hexane using a liquid mass flow meter, and introduce it into the preheating zone for preheating and vaporization. Then, it enters the reaction zone and is premixed with hydrogen. Both the heating and reaction sections of the reactor are heated by electric heating wires to reach 450 °C, under atmospheric pressure and a liquid hourly space velocity of 15 h⁻¹. -1 After reacting for 1 hour under the specified conditions, the material was condensed and then analyzed by liquid chromatography. A heating coupler was placed in the middle of the catalyst bed to monitor the temperature changes during the reaction in real time.

[0133] Example 9

[0134] The method is the same as in Example 1, except that the catalyst preparation process simultaneously introduces the promoters K and Na:

[0135] Specifically, 15.8 g of chromium nitrate, 0.16 g of sodium nitrate, and 0.13 g of potassium nitrate were weighed and dissolved in 10 g of deionized water to obtain a solution containing the active components. The solution was added to 20 g of composite alumina support to ensure full contact. The solution was then dried in an oven at 80 °C for 12 h and calcined in a muffle furnace at 600 °C for 4 h to obtain the catalyst sample. The results are shown in Table 1.

[0136] Performance evaluation:

[0137] For the dehydrogenation reaction: Weigh 10 grams of dehydrogenation catalyst and place it in an isothermal bed reactor, which is a 600 mm long quartz tube with an inner diameter of Ф10 mm and an outer diameter of Ф16 mm. Adjust the flow rate of n-hexane using a liquid mass flow meter, and introduce it into the preheating zone for preheating and vaporization. Then, it enters the reaction zone and is premixed with hydrogen. Both the heating and reaction sections of the reactor are heated by electric heating wires to reach 450 °C, under atmospheric pressure and a liquid hourly space velocity of 15 h⁻¹. -1 After reacting for 1 hour under the specified conditions, the material was condensed and then analyzed by liquid chromatography. A heating coupler was placed in the middle of the catalyst bed to monitor the temperature changes during the reaction in real time.

[0138] Table 1

[0139]

[0140]

[0141] The preferred embodiments of the present invention have been described in detail above; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combinations of various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.

Claims

1. A straight-chain alkane dehydrogenation catalyst, characterized in that, The catalyst comprises: a support complex and a dehydrogenation active component supported on the support complex, the support complex comprising Al and a Group IVB metal element, the physicochemical characteristics of the support complex comprising: a particle size distribution range of 3-35 micrometers based on Dx (50), and the dehydrogenation active component element selected from Group IVB metal elements; The alumina in the carrier composite has a crystal structure including the Theta crystal form, and the content of the Theta crystal phase alumina ranges from 10% to 65% based on the total weight of alumina; the grain size of the Theta crystal phase alumina ranges from 5 to 20 nm. The molar ratio of Group IVB metals to Al is 0.003 to 0.1; In the carrier complex, the group IVB metal element and Al exist in their oxidized form.

2. The dehydrogenation catalyst according to claim 1, wherein, The dehydrogenation active component element is one or more of Cr, Mo, and W; and / or The elemental content of the dehydrogenation active component, based on the total weight of the catalyst, is 5-25% (elemental).

3. The dehydrogenation catalyst according to claim 2, wherein, The active element for dehydrogenation is Cr; and / or The elemental content of the dehydrogenation active component, based on the total weight of the catalyst, is 10-20% (elemental).

4. The dehydrogenation catalyst according to claim 1, wherein, The dehydrogenation catalyst further includes: 0.1-5% alkali metal promoter by weight of the catalyst.

5. The dehydrogenation catalyst according to claim 4, wherein, The content of alkali metal promoters, calculated by element, is 0.3-2.5% based on the total weight of the catalyst.

6. The dehydrogenation catalyst according to claim 5, wherein, The content of alkali metal promoters, calculated by element, is 0.3-0.8% based on the total weight of the catalyst.

7. The dehydrogenation catalyst according to claim 4, wherein, The alkali metal auxiliaries are selected from at least one of Li, Na, K, and Cs.

8. The dehydrogenation catalyst according to claim 7, wherein, The alkali metal auxiliaries are Na and / or K.

9. The dehydrogenation catalyst according to claim 8, wherein, The alkali metal auxiliaries are a mixture of Na and K, with a Na to K weight ratio of 0.7-0.9:

1.

10. The dehydrogenation catalyst according to claim 1, wherein, The carrier complex has a particle size distribution of 5-20 μm, based on Dx(50); and / or Group IVB metals are selected from one or more of Ti, Zr, and Hf.

11. The dehydrogenation catalyst according to claim 1, wherein, The molar ratio of Group IVB metals to Al is 0.009–0.08; and / or The carrier complex has a particle size distribution of 5-20 μm, based on Dx(50); and / or The metal element in Group IVB is Zr.

12. The dehydrogenation catalyst according to claim 11, wherein, The molar ratio of Group IVB metals to Al is 0.01 to 0.

04.

13. The dehydrogenation catalyst according to claim 1, wherein, The content of Theta crystalline alumina ranges from 10% to 60% based on the total weight of alumina.

14. The dehydrogenation catalyst according to claim 1, wherein, The grain size of theta-phase alumina ranges from 7 to 18 nm.

15. The dehydrogenation catalyst according to any one of claims 1-14, wherein the method for preparing the support complex comprises: I) Form an alkaline solution from the Al source and the Group IVB metal source; II) Add alumina and age; Then, solid-liquid separation, drying, and calcination were carried out.

16. The dehydrogenation catalyst according to claim 15, wherein, In step II), The pore size of alumina is 0.1-5 μm; and / or Alumina dosage: Based on the total molar amount of aluminum in the catalyst, the molar amount of alumina, calculated as elemental aluminum, is 1-60%; and / or The aluminum oxide is γ-alumina; and / or The aging conditions include: standing still for 6-24 hours.

17. The dehydrogenation catalyst according to claim 16, wherein, In step II), The pore size of alumina is 0.5-1 μm; and / or Alumina dosage: Based on the total molar amount of aluminum in the catalyst, the molar amount of alumina, calculated as elemental aluminum, is 8-50%; and / or The aging process is carried out in the presence of polyallyl alcohol with an average molecular weight of 200-2500, and the amount of polyallyl alcohol used is 0.1-5% based on the total weight of the aging solution.

18. The dehydrogenation catalyst according to claim 17, wherein, In step II), The aging process was carried out in the presence of polyallyl alcohol with an average molecular weight of 400-1025.

19. The dehydrogenation catalyst according to claim 15, wherein, Methods for preparing the carrier complex include: i) Under conditions of 20-50℃, add the Al source and the Group IVB metal element source to deionized water in proportion and stir thoroughly to dissolve; ii) Add an alkaline solution dropwise to the solution obtained in step i), and continue stirring for 1-3 hours after adding the solution; iii) Add aluminum oxide to the solution in step ii) in proportion, continue stirring for 2-6 hours, and let stand and age for 6-24 hours; iiii) Pour the precipitate obtained in step iii) into a centrifuge, centrifuge, wash with deionized water more than three times, dry the filter cake at 80-120℃ for 12-24h, and then calcine at 500-750℃ for 2-12h.

20. The dehydrogenation catalyst according to claim 19, wherein, In step iii), add polyallyl alcohol with a molecular weight of 200-2500. The amount of polyallyl alcohol used is 0.1-5% based on the total weight of the solution.

21. The dehydrogenation catalyst according to claim 20, wherein, In step iii), polyallyl alcohol with a molecular weight of 400-1025 is added.

22. A method for dehydrogenating straight-chain alkanes, characterized in that, The method includes: performing a dehydrogenation reaction on a straight-chain alkane in the presence of a catalyst, said catalyst comprising a straight-chain alkane dehydrogenation catalyst according to any one of claims 1-21.

23. The method according to claim 22, wherein, The conditions for the dehydrogenation reaction include: a reaction temperature of 400-500℃, a reaction pressure of 0.1-3 MPa, and a liquid hourly space velocity (LISH) of 5-30 h⁻¹ for straight-chain alkanes. -1 .

24. The method according to claim 22, wherein, The straight-chain alkane is a C6-C13 alkane.

25. The method according to claim 24, wherein, The straight-chain alkane is a C6 alkane.

26. The method according to claim 25, wherein, The straight-chain alkane is n-hexane.

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