Straight-chain alkane dehydrogenation catalyst and straight-chain alkane dehydrogenation method

Abstract

The invention discloses a straight-chain alkane dehydrogenation catalyst and a straight-chain alkane dehydrogenation method.The catalyst comprises a carrier compound and a dehydrogenation active component loaded on the carrier compound, the carrier compound comprises Al and IVB group metal elements, and the physical and chemical characteristics of the carrier compound are as follows: the particle size distribution range is 3-35 micrometers in terms of Dx (50), and the particle size distribution range is 1-5 micrometers in terms of Dx (50). The dehydrogenation active component elements are selected from VIB group metal elements. The catalyst provided by the invention is used for dehydrogenation of straight-chain alkanes, especially in the dehydrogenation conversion process of C6-C13 straight-chain alkanes, contact is carried out under the conditions that the reaction temperature is 400-500 DEG C, the reaction pressure is 0.1-3 MPa and the liquid hourly space velocity is 5-30 h <-1 >, a dehydrogenation reaction is carried out, and the selectivity reaches 89% or above.

Description

Technical Field

[0001] The present invention relates to a linear alkane dehydrogenation catalyst and a linear alkane dehydrogenation method. Background Art

[0002] Straight-chain olefins with 6, especially 9 or more carbon atoms are very economical compounds, which are widely used as basic materials for preparing intermediates of biodegradable detergents, drugs, plastics, synthetic rubbers, etc. Straight-chain alkanes with 6-13 or more carbon atoms are used to produce corresponding linear olefins by adopting a dehydrogenation method. In this process, hydrogen and gasified straight-chain alkanes are contacted with a dehydrogenation catalyst, and then reacted at high temperature and a certain pressure. During the dehydrogenation reaction, it is necessary to increase the reaction rate of the raw materials to suppress the occurrence of side reactions such as cracking, coke generation, isomerization, etc., thereby increasing the selectivity of linear olefins.

[0003] At present, the catalysts for the dehydrogenation of straight-chain alkanes to produce straight-chain olefins and then alkylbenzenes are mainly noble metal catalysts. The catalysts used in this type of straight-chain alkane dehydrogenation reaction use platinum group noble metals as active components, some metals in Group III, Group V and Group VI as second active components, and alkali metals and alkaline earth metals as additives. On the other hand, this type of straight-chain alkane dehydrogenation reaction requires the catalyst to have a large pore size and high porosity to facilitate the internal diffusion of the reactants, thereby fully utilizing the active components.

[0004] CN1017779B proposes a solid, granular, porous carrier to constitute 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 flow of straight-chain alkane and hydrogen is introduced into a reactor at a molar ratio of 1:1 to 15:1 and reacted at 400-550°C, the conversion rate of the straight-chain alkane is as high as 18.5% and the selectivity is as high as 90%.

[0005] CN87101513A discloses a catalyst for dehydrogenation of saturated hydrocarbons. In the preparation, an aqueous solution of aluminum chloride is used. At a temperature of 60°C to 80°C, it is first neutralized with ammonia water to a pH value of 7.5 to 8.5. The resulting aluminum hydroxide slurry is washed with water, acidified and pelletized in an oil-ammonia column, dried and calcined to form alumina pellets, which are then treated with steam to obtain a macroporous catalyst carrier. Active components such as platinum, tin, and lithium are then impregnated by a co-impregnation method to obtain a final catalyst sample. However, the process requires large equipment investment, alkali metals are easily lost, and the products of the preparation process are corrosive and toxic liquids that pollute the environment.

[0006] CN102441378A discloses a linear alkane dehydrogenation catalyst, especially for C6~C 30The catalyst for the dehydrogenation of straight-chain alkanes to produce monoolefins has a simple preparation process and a large specific surface area and pore volume. At a reaction pressure of 1.0 MPa, an inlet temperature of 480°C, and a liquid hourly volume space velocity of 20 h -1 Under the condition of hydrogen / alkane molar ratio of 5:1, the conversion rate of dehydrogenation catalyst to alkane is up to 19.3%, and the olefin selectivity is 94%. Due to the large amount of hydrogen, the operation process is complicated and the cost is high.

[0007] It can be seen from the currently disclosed technologies that although the existing precious metal catalysts have been improved and optimized to varying degrees, the conversion rate of straight-chain alkanes is still relatively low, and the improvement effect has not achieved the expected goal. Summary of the invention

[0008] The purpose of the present invention is to overcome the problem of low selectivity of linear alkane dehydrogenation catalysts in the prior art and to provide a novel linear alkane dehydrogenation catalyst having the advantages of good olefin selectivity and the like.

[0009] According to the first aspect of the present invention, the present invention provides a straight-chain alkane dehydrogenation catalyst, which comprises: a carrier complex and a dehydrogenation active component loaded on the carrier complex, the carrier complex comprises Al and a Group IVB metal element, and the physicochemical characteristics of the carrier complex include: a particle size distribution range of 3-35 microns based on Dx(50), and the dehydrogenation active component elements are selected from Group VIB 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: subjecting straight-chain alkanes to a dehydrogenation reaction in the presence of a catalyst, wherein the catalyst comprises the straight-chain alkanes dehydrogenation catalyst of the present invention;

[0011] 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 linear alkane liquid hourly space velocity of 5-30 h -1 ;

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

[0013] The carrier of the present invention has advantages such as excellent particle size distribution and specific Theta alumina crystal form, etc. The catalyst of the present invention has high olefin selectivity.

[0014] The catalyst of the present invention is used for dehydrogenation of straight-chain alkanes, especially in the dehydrogenation and conversion process of C6 alkanes, at a reaction temperature of 400-500°C, a reaction pressure of 0.1-3MPa, and a liquid hourly space velocity of 5-30 hours. -1 The contact is carried out under the conditions of , dehydrogenation reaction occurs, and the olefin selectivity reaches more than 89%. DETAILED DESCRIPTION

[0015] The endpoints and any values ​​of the ranges disclosed in this article 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 each range, the endpoint values ​​of each range and the individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed in this article.

[0016] The present invention provides a linear alkane dehydrogenation catalyst, which comprises: a carrier composite and a dehydrogenation active component loaded on the carrier composite, wherein the carrier composite comprises Al and a metal element of Group IVB, and the physicochemical characteristics of the carrier composite include: a particle size distribution range of 3-35 microns in terms of Dx(50), and the dehydrogenation active component element is selected from a metal element of Group VIB. After the novel composite carrier of the present invention is loaded with the active component, the catalyst has the advantages of high activity and good stability.

[0017] In the present invention, the types of dehydrogenation active components can be selected from a wide range. For the present invention, this is exemplified but does not limit the scope of the present invention. Preferably, the dehydrogenation active component element is selected from one or more of Cr, Mo, and W, and more preferably Cr.

[0018] In the present invention, the dosage of the dehydrogenation active component can be selected in a wide range, and the commonly used dosage can be applicable to the present invention. For the present invention, the dehydrogenation active component element content is preferably 5-25% by weight, preferably 10-20% by weight, based on the total weight of the catalyst.

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

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

[0021] In the present invention, the mass ratio of the Group IVB metal element to Al can be selected in a wide range, which is illustrative but not limiting the scope of the present invention. According to a preferred embodiment of the present 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 element, and the Group IVB metal element and Al in the carrier composite exist in an oxidized form.

[0023] According to a preferred embodiment of the present invention, the carrier complex has a particle size distribution of 5-20 microns based on Dx(50).

[0024] According to a preferred embodiment of the present invention, the crystal structure of the aluminum oxide in the carrier composite includes a Theta crystal structure, and the content of the Theta crystal phase aluminum oxide (θ-Al2O3) is in the range of 30 to 60% based on the total weight of the aluminum oxide.

[0025] In the present 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 crystal structure of the aluminum oxide in the carrier composite includes a Theta crystal structure, and the content of the Theta crystal phase aluminum oxide is in the range of 10 to 65%, preferably 10 to 60%, based on the total weight of the aluminum oxide.

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

[0028] The carriers with the characteristics of the present invention can achieve the purpose of the present invention, and there is no special requirement for their preparation methods. According to one embodiment of the present invention, the preparation method of the carrier composite comprises: I) forming an alkaline solution with an Al source and a Group IVB metal element source; II) adding alumina and aging; then solid-liquid separation, drying, and roasting. The carrier composite with the advantages of the characteristics of the present invention can be synthesized by using the above preferred preparation method.

[0029] In the present invention, in step I), the dosage ratio of each material can be selected in a wide range, which is exemplified below, but does not limit the scope of the present invention. According to a preferred embodiment of the present invention, the molar ratio of Al source: Group IVB metal source: deionized water: alkali is = (10-100): 1: (10-500): (30-80).

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

[0031] The alkaline solution in the present invention only needs to meet the alkalinity requirement, and there is no special requirement for its alkalinity value.

[0032] In the present invention, there is no special requirement for the type of Al source, and various substances are suitable for the present invention, such as a water-soluble aluminum source. The following exemplary description does not limit the scope of the present invention. According to one embodiment of the present invention, the Al source includes one or more of aluminum nitrate nonahydrate, aluminum sulfate, aluminum isopropoxide and aluminum sol.

[0033] In the present invention, there is no special requirement for the type of the Group IVB metal source, and various substances are applicable to the present invention. The following exemplary description is not intended to limit the scope of the present invention. According to one embodiment of the present invention, the Group IVB metal source is selected from a soluble compound of a Group IVB metal source, preferably a soluble salt of a Group IVB metal source, and when it is Zr, it is preferably zirconium nitrate hexahydrate and / or zirconium oxychloride octahydrate.

[0034] In the present invention, the base used can be selected from a wide range of materials, and commonly used bases can be applicable to the present invention. The following exemplary description is given for the present invention, but the scope of the present invention is not limited thereto. Preferably, the base is selected from organic amines and / or inorganic ammonia.

[0035] In the present invention, the optional range of types of the organic amine substances is relatively wide, and commonly used organic amine substances can be applicable to the present invention, for example, one or more of 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-propylenediamine, 1,4-butylenediamine, tetramethylammonium hydroxide, tetraethylammonium hydroxide and tetrapropylammonium hydroxide.

[0036] In the present invention, there is no special requirement for the step of mixing the Al source and the Group IVB metal source to form an alkaline solution. The main purpose is to mix them evenly. For example, the materials can be mixed evenly by appropriate heating and dripping. The following exemplary description, but not limiting the scope of the present invention, includes the following steps:

[0037] i) adding an aluminum source and a zirconium source to deionized water in proportion at 20-50° C., for example, 20° C., 25° C., 30° C., 35° C., 40° C., 45° C., or 50° C., and stirring to dissolve;

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

[0039] In the present invention, there is no special requirement for the source of alumina. For the present invention, the alumina is preferably small-pore alumina, and the pore size of the alumina is preferably 0.1-5 μm, preferably 0.5-1 μm.

[0040] In the present invention, the form of the aluminum oxide is not particularly limited, and it is preferably γ-alumina, for example.

[0041] This can further achieve optimal performance of the obtained composite carrier.

[0042] In the present invention, the optional range of the amount of aluminum oxide is relatively wide, which is illustrative but not limiting. For the present invention, the preferred amount of aluminum oxide is: based on the total molar amount of aluminum in the catalyst, the molar amount of aluminum oxide calculated as aluminum element is 1 to 60%, preferably 8 to 50%.

[0043] In the present invention, there is no special requirement for the aging conditions. The preferred aging conditions include: standing and aging 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, preferably, the aging is carried out in the presence of polyallyl alcohol having 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 embodiment, the average molecular weight of 1025 is used as an exemplary illustration, and the added amount is 0.5% of the weight of the solution, but the scope of the present invention is not limited thereby.

[0045] In the present invention, there is no special requirement for the conditions of drying and roasting, and the following is an exemplary description, but the scope of the present invention is not limited thereby.

[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 h, for example, 12 h, 14 h, 16 h, 18 h, 20 h, or 24 h.

[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, 750°C; a time of 2-12h, for example, 2h, 4h, 6h, 8h, 10h, 12h.

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

[0049] i) adding an aluminum source and a zirconium source to deionized water in proportion at 20-50° C., for example, 20° C., 25° C., 30° C., 35° C., 40° C., 45° C., or 50° C., and stirring to dissolve;

[0050] ii) adding a base solution dropwise to the solution obtained in step i), and continuing stirring for 1-3 hours after the addition, for example, 1 hour, 2 hours, or 3 hours;

[0051] iii) adding aluminum oxide to the solution in step ii) in proportion, continuing stirring for 2-6 hours, for example, 2 hours, 4 hours, 6 hours, standing still and aging 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) pouring the precipitate obtained in step iii) into a centrifuge, centrifuging, washing with deionized water for more than three times, drying the filter cake at 80-120° C. for 12-24 hours, and then calcining at 500-750° C. for 2-12 hours.

[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 the polyallyl alcohol is 0.1-5% based on the total weight of the solution.

[0054] The carrier prepared by the aforementioned preferred embodiment has the best performance.

[0055] The present invention has no special requirements for the preparation method of the catalyst. According to the present invention, a preparation method of the dehydrogenation catalyst is provided, and the preparation method comprises:

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

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

[0058] In the present invention, there is no special requirement for the impregnation method, which is an exemplary description but does not limit the scope of the present invention. The impregnation method is an equal volume impregnation method. Preferably, the equal volume impregnation is performed by a spraying method.

[0059] In the present invention, there is no special requirement for the conditions of drying and roasting, and the following is an exemplary description, but the scope of the present invention is not limited thereby.

[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 h.

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

[0063] The present invention provides a method for dehydrogenating straight-chain alkanes, which comprises: subjecting the straight-chain alkanes to a dehydrogenation reaction in the presence of a catalyst, wherein the catalyst comprises the dehydrogenation catalyst described in the present invention.

[0064] In the present invention, there is no special requirement for the dehydrogenation reaction conditions, which are described below for exemplary purposes, but the scope of the present invention is not limited thereby.

[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 linear alkane liquid hourly space velocity of 5-30 h -1 .

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

[0067] The present invention has no special requirements for the reactor used for the dehydrogenation reaction. For example, an isothermal bed reactor is used, for example, a quartz tube with an inner diameter of 10 mm and an outer diameter of 16 mm, and a length of 600 mm. The raw material is adjusted in flow by a liquid mass flow meter, enters a preheating zone for preheating and vaporization, and then enters a reaction zone for premixing with hydrogen. The heating section and the reaction section of the reactor are both heated by electric heating wires. After the reacted material passes through a condenser, it enters a liquid chromatogram for composition analysis. At the same time, a heating couple can be heated in the middle of the catalyst bed to monitor the temperature change 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 carrier is obtained by dry testing using a Malvern particle size analyzer, the crystal form of the bimetallic oxide carrier is obtained by XRD analysis combined with instrument configuration identification software TOPAS, and the average pore size distribution of the oxide is obtained by the BET method, which are all well-known techniques in the art and are not described in detail in the present invention; the raw materials used are all analytically pure products commercially available from China Pharmaceutical Group.

[0069] In the present invention, the test method for the grain size in theta crystalline phase alumina is to import the XRD spectrum of the test sample into the TOPAS software, set the grain parameters of the crystalline phase, perform spectrum recognition, ensure that the set parameters coincide with the actual spectrum, run the software after confirmation, and obtain the grain size.

[0070] In the present invention, the test method for the Theta crystalline phase alumina content is to import the test sample XRD spectrum into the TOPAS software, set the calculation parameters of the Theta crystalline phase, make the fitting spectrum coincide with the actual spectrum, run the software after confirmation, and obtain the proportion of the Theta crystalline phase in the sample.

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

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

[0073] Olefin selectivity (%) = actual olefin production / theoretical olefin production × 100%, by mass.

[0074] In the examples and comparative examples of the present 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 the ZrO2-Al2O3 carrier was analyzed by Malvern 3000 particle size analyzer. The test method is as follows: first clean the particle size analyzer and set the test parameters, where the Venturi tube is set according to the standard value, the test pressure is 2 bar, add the test powder, set the file name, click to start the test, the instrument automatically completes the background scan and three powder parallel tests, and after the test, the test data is processed through the editing option to obtain the Dx (50) particle size of the composite oxide carrier.

[0076] The catalysts of the following examples and comparative examples are used for dehydrogenation reaction: 10 grams of dehydrogenation catalyst are weighed and placed in an isothermal bed reactor, wherein the reactor is a quartz tube with an inner diameter of 10 mm and an outer diameter of 16 mm, and a length of 600 mm. The flow rate of n-hexane is adjusted by a liquid mass flowmeter, and it enters the preheating zone for preheating and vaporization, and then enters the reaction zone for premixing with hydrogen. The heating section and the reaction section of the reactor are heated by electric heating wires to 450°C. At a pressure of normal pressure and a liquid hourly space velocity of 15h -1 After the reaction is continued for 1 hour under the conditions, the material passes through a condenser and enters a liquid chromatography for analysis of its composition. A heating couple is placed in the middle of the catalyst bed to monitor the temperature change during the reaction in real time.

[0077] Example 1

[0078] Preparation of carrier complex:

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

[0080] At 30°C, dissolve aluminum nitrate and zirconium nitrate in deionized water and stir thoroughly to dissolve; slowly add ammonia water dropwise while stirring for 2 hours;

[0081] Then slowly add 5 grams of γ-alumina with a pore size distribution of 0.5-1 micron, continue stirring for 3 hours, and let it stand for 12 hours; filter the sol in a 50-liter centrifuge, add deionized water to wash three times, transfer to an oven to dry at 80°C for 12 hours, and then place it in a muffle furnace and calcine at 600°C for 4 hours to obtain an Al2O3 composite oxide carrier, the Dx(50) particle size of the composite oxide carrier is 7.2 microns, wherein the θ-Al2O3 accounts for 35% of the total weight of alumina, and the θ-Al2O3 grain size is 7.8nm;

[0082] Preparation of dehydrogenation catalyst:

[0083] Weigh 15.8 grams of chromium nitrate and 0.33 grams of sodium nitrate, dissolve in 10 grams of deionized water to obtain a solution containing active components, add the solution to 20 grams of composite alumina support to make them fully contact, then dry in an oven at 80°C for 12 hours, move into a muffle furnace and calcine at 600°C for 4 hours to obtain a catalyst sample. The results are shown in Table 1;

[0084] Performance evaluation:

[0085] For dehydrogenation reaction: weigh 10 grams of dehydrogenation catalyst and put it into an isothermal bed reactor, where the reactor is a quartz tube with an inner diameter of 10 mm and an outer diameter of 16 mm, and a length of 600 mm. The flow of n-hexane is adjusted by a liquid mass flow meter, and it enters the preheating zone for preheating and vaporization, and then enters the reaction zone for premixing with hydrogen. The heating section and the reaction section of the reactor are heated by electric heating wires to 450°C. At normal pressure and a liquid hourly space velocity of 15h -1 After the reaction is continued for 1 hour under the conditions, the material passes through a condenser and enters a liquid chromatography for analysis of its composition. A heating couple is placed in the middle of the catalyst bed to monitor the temperature change during the reaction in real time.

[0086] Comparative Example 1

[0087] When preparing the carrier composite, small pore alumina is not added, and the amount of aluminum source of aluminum nitrate nonahydrate is increased so that the carrier is calculated in terms of aluminum. The amount used is consistent with that in Example 1. The remaining components, contents and preparation process are the same as in Example 1. As a result, the particle size distribution of the obtained carrier Dx(50) is 40 microns. The results are shown in Table 1.

[0088] Performance evaluation:

[0089] For dehydrogenation reaction: weigh 10 grams of dehydrogenation catalyst and put it into an isothermal bed reactor, where the reactor is a quartz tube with an inner diameter of 10 mm and an outer diameter of 16 mm, and a length of 600 mm. The flow of n-hexane is adjusted by a liquid mass flow meter, and it enters the preheating zone for preheating and vaporization, and then enters the reaction zone for premixing with hydrogen. The heating section and the reaction section of the reactor are heated by electric heating wires to 450°C. At normal pressure and a liquid hourly space velocity of 15h -1 After the reaction is continued for 1 hour under the conditions, the material passes through a condenser and enters a liquid chromatography for analysis of its composition. A heating couple is placed in the middle of the catalyst bed to monitor the temperature change during the reaction in real time.

[0090] Example 2

[0091] According to the method of Example 1, the difference is 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 aqueous ammonia (concentration 25 wt%);

[0093] At 30°C, dissolve aluminum nitrate and zirconium nitrate in deionized water and stir thoroughly to dissolve; slowly add ammonia water dropwise while stirring for 1 hour;

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

[0095] The Dx(50) particle size of the composite oxide carrier is 16 microns, of which θ-Al2O3 accounts for 45% based on 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. The results are shown in Table 1.

[0097] Performance evaluation:

[0098] For dehydrogenation reaction: weigh 10 grams of dehydrogenation catalyst and put it into an isothermal bed reactor, where the reactor is a quartz tube with an inner diameter of 10 mm and an outer diameter of 16 mm, and a length of 600 mm. The flow of n-hexane is adjusted by a liquid mass flow meter, and it enters the preheating zone for preheating and vaporization, and then enters the reaction zone for premixing with hydrogen. The heating section and the reaction section of the reactor are heated by electric heating wires to 450°C. At normal pressure and a liquid hourly space velocity of 15h -1 After the reaction is continued for 1 hour under the conditions, the material passes through a condenser and enters a liquid chromatography for analysis of its composition. A heating couple is placed in the middle of the catalyst bed to monitor the temperature change during the reaction in real time.

[0099] Example 3

[0100] According to the method of Example 1, the difference is that the preparation steps of the carrier are as follows:

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

[0102] At 30°C, dissolve aluminum nitrate and zirconium nitrate in deionized water and stir thoroughly to dissolve.

[0103] In the subsequent preparation process, the standing time is increased to 24 h, and the roasting temperature is 620° C., the roasting time is 6 h, and the other parameters remain unchanged.

[0104] The Dx(50) particle size of the obtained composite oxide carrier is 11 microns, wherein θ-Al2O3 accounts for 58% based on 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. The results are shown in Table 1.

[0106] Performance evaluation:

[0107] For dehydrogenation reaction: weigh 10 grams of dehydrogenation catalyst and put it into an isothermal bed reactor, where the reactor is a quartz tube with an inner diameter of 10 mm and an outer diameter of 16 mm, and a length of 600 mm. The flow of n-hexane is adjusted by a liquid mass flow meter, and it enters the preheating zone for preheating and vaporization, and then enters the reaction zone for premixing with hydrogen. The heating section and the reaction section of the reactor are heated by electric heating wires to 450°C. At normal pressure and a liquid hourly space velocity of 15h -1 After the reaction is continued for 1 hour under the conditions, the material passes through a condenser and enters a liquid chromatography for analysis of its composition. A heating couple is placed in the middle of the catalyst bed to monitor the temperature change during the reaction in real time.

[0108] Example 4

[0109] The method of Example 1 is followed, except that 5 grams of alumina with a pore size of 1-2 microns is added to the aging step, and other conditions are the same, to obtain a composite oxide carrier with a Dx(50) particle size of 14 microns, of which θ-Al2O3 accounts for 40% of the total weight of alumina, and the θ-Al2O3 grain size is 11.5nm.

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

[0111] Performance evaluation:

[0112] For dehydrogenation reaction: weigh 10 grams of dehydrogenation catalyst and put it into an isothermal bed reactor, where the reactor is a quartz tube with an inner diameter of 10 mm and an outer diameter of 16 mm, and a length of 600 mm. The flow of n-hexane is adjusted by a liquid mass flow meter, and it enters the preheating zone for preheating and vaporization, and then enters the reaction zone for premixing with hydrogen. The heating section and the reaction section of the reactor are heated by electric heating wires to 450°C. At normal pressure and a liquid hourly space velocity of 15h -1 After the reaction is continued for 1 hour under the conditions, the material passes through a condenser and enters a liquid chromatography for analysis of its composition. A heating couple is placed in the middle of the catalyst bed to monitor the temperature change during the reaction in real time.

[0113] Example 5

[0114] The method of Example 1 was followed, except that the amount of alumina was 10 g, and other conditions remained unchanged. The Dx(50) particle size of the obtained composite oxide support was 12.5 μm, wherein θ-Al2O3 accounted for 43% of the total weight of alumina, and the θ-Al2O3 grain size was 8.5 nm.

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

[0116] Performance evaluation:

[0117] For dehydrogenation reaction: weigh 10 grams of dehydrogenation catalyst and put it into an isothermal bed reactor, where the reactor is a quartz tube with an inner diameter of 10 mm and an outer diameter of 16 mm, and a length of 600 mm. The flow of n-hexane is adjusted by a liquid mass flow meter, and it enters the preheating zone for preheating and vaporization, and then enters the reaction zone for premixing with hydrogen. The heating section and the reaction section of the reactor are heated by electric heating wires to 450°C. At normal pressure and a liquid hourly space velocity of 15h -1 After the reaction is continued for 1 hour under the conditions, the material passes through a condenser and enters a liquid chromatography for analysis of its composition. A heating couple is placed in the middle of the catalyst bed to monitor the temperature change during the reaction in real time.

[0118] Example 6

[0119] The method of Example 1 is followed, except that the amounts of the substances used are: 750.3 g aluminum nitrate nonahydrate, 3.4 g zirconium nitrate, 36 g deionized water and 52.6 g ammonia water (concentration of 25 wt%). The preparation conditions remain unchanged, and the Dx(50) particle size of the obtained composite oxide support is 20 μm, wherein θ-Al2O3 accounts for 25% of the total weight of aluminum oxide, and the grain size is 5.8 nm.

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

[0121] Performance evaluation:

[0122] For dehydrogenation reaction: weigh 10 grams of dehydrogenation catalyst and put it into an isothermal bed reactor, where the reactor is a quartz tube with an inner diameter of 10 mm and an outer diameter of 16 mm, and a length of 600 mm. The flow of n-hexane is adjusted by a liquid mass flow meter, and it enters the preheating zone for preheating and vaporization, and then enters the reaction zone for premixing with hydrogen. The heating section and the reaction section of the reactor are heated by electric heating wires to 450°C. At normal pressure and a liquid hourly space velocity of 15h -1 After the reaction is continued for 1 hour under the conditions, the material passes through a condenser and enters a liquid chromatography for analysis of its composition. A heating couple is placed in the middle of the catalyst bed to monitor the temperature change during the reaction in real time.

[0123] Example 7

[0124] The method of Example 1 is followed, except that the composite oxide carrier is aged for 72 hours and the other conditions are the same, and the Dx(50) particle size of the composite oxide carrier is 27 microns, wherein θ-Al2O3 accounts for 65% of the total weight of alumina and the grain size is 10.6 nm.

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

[0126] Performance evaluation:

[0127] For dehydrogenation reaction: weigh 10 grams of dehydrogenation catalyst and put it into an isothermal bed reactor, where the reactor is a quartz tube with an inner diameter of 10 mm and an outer diameter of 16 mm, and a length of 600 mm. The flow of n-hexane is adjusted by a liquid mass flow meter, and it enters the preheating zone for preheating and vaporization, and then enters the reaction zone for premixing with hydrogen. The heating section and the reaction section of the reactor are heated by electric heating wires to 450°C. At normal pressure and a liquid hourly space velocity of 15h -1 After the reaction is continued for 1 hour under the conditions, the material passes through a condenser and enters a liquid chromatography for analysis of its composition. A heating couple is placed in the middle of the catalyst bed to monitor the temperature change during the reaction in real time.

[0128] Example 8

[0129] The method of Example 1 is followed, except that: 0.5% of the weight of the solution is added to the aging solution with an average molecular weight of 1025 polyallyl alcohol (added together with γ-alumina), and other conditions are the same. The Dx(50) particle size of the obtained composite oxide carrier is 34 microns, of which θ-Al2O3 accounts for 10% based on the total weight of alumina, and the grain size is 18nm.

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

[0131] Performance evaluation:

[0132] For dehydrogenation reaction: weigh 10 grams of dehydrogenation catalyst and put it into an isothermal bed reactor, where the reactor is a quartz tube with an inner diameter of 10 mm and an outer diameter of 16 mm, and a length of 600 mm. The flow of n-hexane is adjusted by a liquid mass flow meter, and it enters the preheating zone for preheating and vaporization, and then enters the reaction zone for premixing with hydrogen. The heating section and the reaction section of the reactor are heated by electric heating wires to 450°C. At normal pressure and a liquid hourly space velocity of 15h -1 After the reaction is continued for 1 hour under the conditions, the material passes through a condenser and enters a liquid chromatography for analysis of its composition. A heating couple is placed in the middle of the catalyst bed to monitor the temperature change during the reaction in real time.

[0133] Example 9

[0134] The method of Example 1 is followed, except that the catalyst preparation process simultaneously introduces additives K and Na:

[0135] The details are as follows: 15.8 grams of chromium nitrate, 0.16 grams of sodium nitrate and 0.13 grams of potassium nitrate were weighed and dissolved in 10 grams of deionized water to obtain a solution containing active components. The solution was added to 20 grams of the composite alumina carrier to allow sufficient contact, and then dried in an oven at 80°C for 12 hours, transferred to a muffle furnace and calcined at 600°C for 4 hours to obtain a catalyst sample. The results are shown in Table 1.

[0136] Performance evaluation:

[0137] For dehydrogenation reaction: weigh 10 grams of dehydrogenation catalyst and put it into an isothermal bed reactor, where the reactor is a quartz tube with an inner diameter of 10 mm and an outer diameter of 16 mm, and a length of 600 mm. The flow of n-hexane is adjusted by a liquid mass flow meter, and it enters the preheating zone for preheating and vaporization, and then enters the reaction zone for premixing with hydrogen. The heating section and the reaction section of the reactor are heated by electric heating wires to 450°C. At normal pressure and a liquid hourly space velocity of 15h -1 After the reaction is continued for 1 hour under the conditions, the material passes through a condenser and enters a liquid chromatography for analysis of its composition. A heating couple is placed in the middle of the catalyst bed to monitor the temperature change during the reaction in real time.

[0138] Table 1

[0139]

[0140]

[0141] The preferred embodiments of the present invention are described in detail above, but the present invention is not limited thereto. Within the technical concept of the present invention, the technical solution of the present invention can be subjected to a variety of simple modifications, including the combination of various technical features in any other suitable manner, and these simple modifications and combinations should also be regarded as the contents disclosed by the present invention and belong to the protection scope of the present invention.

Claims

1. A linear alkane dehydrogenation catalyst, characterized in that: The catalyst comprises: a carrier composite and a dehydrogenation active component loaded on the carrier composite, wherein the carrier composite comprises Al and a metal element of Group IVB, and the physicochemical characteristics of the carrier composite comprise: a particle size distribution range of 3-35 microns based on Dx(50), and the dehydrogenation active component element is selected from a metal element of Group VIB.

2. The dehydrogenation catalyst according to claim 1, wherein The dehydrogenation active component element is one or more of Cr, Mo, and W, more preferably Cr; and / or The content of the dehydrogenation active component elements is 5 to 25%, preferably 10 to 20%, based on the total weight of the catalyst.

3. The dehydrogenation catalyst according to claim 1 or 2, wherein The dehydrogenation catalyst further comprises: an alkali metal promoter in an amount of 0.1-5%, preferably 0.3-2.5%, more preferably 0.3-0.8%, based on the total weight of the catalyst, as an element; Preferably, the alkali metal additive is selected from at least one of Li, Na, K, and Cs, preferably Na and / or K; more preferably, it is a mixture of Na and K, and the content of one of them is not less than 10 wt %; more preferably, the weight ratio of Na to K is 0.7-0.9:

1.

4. The dehydrogenation catalyst according to any one of claims 1 to 3, wherein The molar ratio of the Group IVB metal element to Al is 0.003 to 0.1, preferably 0.009 to 0.08, more preferably 0.01 to 0.04; and / or The Group IVB metal element and Al in the carrier composite are present in an oxidized form; and / or The carrier complex has a particle size distribution of 5-20 microns based on Dx(50); and / or The Group IVB metal element is selected from one or more of Ti, Zr and Hf, preferably Zr.

5. The dehydrogenation catalyst according to any one of claims 1 to 4, wherein The crystalline structure of the aluminum oxide in the carrier composite includes a Theta crystalline structure, and the content of the Theta crystalline aluminum oxide is in the range of 10 to 65%, preferably 10 to 60%, based on the total weight of the aluminum oxide; Preferably, the grain size of the Theta crystalline alumina is in the range of 5 to 20 nm, preferably 7 to 18 nm.

6. The dehydrogenation catalyst according to any one of claims 1 to 5, wherein the preparation method of the carrier composite comprises: 1) forming an alkaline solution with an Al source and a Group IVB metal element source; II) adding alumina and aging; Then the solid and liquid are separated, dried and roasted; Preferably, In step I), The molar ratio of Al source: Group IVB metal source: deionized water: alkali is = (10-100): 1: (10-500): (30-80).

7. The dehydrogenation catalyst according to claim 6, wherein In step II), The pore size of the aluminum oxide is 0.1-5 μm, preferably 0.5-1 μm; and / or The amount of aluminum oxide used: based on the total mole of aluminum in the catalyst, the molar amount of aluminum oxide calculated as aluminum element is 1 to 60%, preferably 8 to 50%; and / or Alumina is γ-alumina; and / or The aging conditions include: standing still, aging for 6-24h; Preferably, the aging is carried out in the presence of polyallyl alcohol having 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 aged solution.

8. The dehydrogenation catalyst according to claim 6 or 7, wherein The method for preparing the carrier complex comprises: i) adding Al source and Group IVB metal element source into deionized water in proportion at 20-50° C. and stirring thoroughly to dissolve; ii) adding a base solution dropwise to the solution obtained in step i), and continuing stirring for 1-3 hours after the addition; iii) adding aluminum oxide to the solution in step ii) in proportion, continuing stirring for 2-6 hours, and allowing to stand for 6-24 hours; iiii) pouring the precipitate obtained in step iii) into a centrifuge, centrifuging, washing with deionized water for more than three times, drying the filter cake at 80-120° C. for 12-24 hours, and then calcining at 500-750° C. for 2-12 hours.

9. The dehydrogenation catalyst according to claim 8, wherein In step iii), polyallyl alcohol having a molecular weight of 200-2500, preferably 400-1025, is added in an amount of 0.1-5% based on the total weight of the solution.

10. A method for dehydrogenating straight-chain alkanes, characterized in that: The method comprises: subjecting a straight-chain alkane to a dehydrogenation reaction in the presence of a catalyst, wherein the catalyst comprises the straight-chain alkane dehydrogenation catalyst according to any one of claims 1 to 9; 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 linear alkane liquid hourly space velocity of 5-30 h -1 ; Preferably, the straight-chain alkane is a C6-C13 alkane, preferably a C6 alkane, and more preferably n-hexane.

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