A propane dehydrogenation catalyst, a preparation method and application thereof

Abstract

The application discloses a propane dehydrogenation catalyst and a preparation method and application thereof, and relates to the technical field of catalysts. The propane dehydrogenation catalyst comprises an alumina carrier and an active component, the alumina carrier contains a composite additive in a skeleton lattice, the composite additive is a metal element in the form of an oxide, and the metal element comprises at least two of Ca, Mg, Fe, Zr, Na, K, Y, Ga, Ce and Gd. The propane dehydrogenation catalyst has the alumina as a carrier body and the metal element as a composite additive, and through the synergistic effect of the composite additive and the alumina carrier, the activity and stability of the catalyst are improved.

Description

Technical Field

[0001] This invention relates to the field of catalysts, and more particularly to a propane dehydrogenation catalyst, its preparation method, and its application. Background Technology

[0002] Propylene, as an important basic feedstock in the petrochemical industry, is widely used in the production of various chemical products such as polypropylene, acrylonitrile, and propylene oxide. With the rapid development of downstream industries, market demand for propylene continues to rise. Propane dehydrogenation, due to its wide availability of raw materials and high selectivity for propylene, has become one of the mainstream technologies for increasing propylene production.

[0003] Catalysts are the core of propane dehydrogenation technology, and their performance directly determines reaction efficiency, product yield, and industrial economics. Existing propane dehydrogenation catalysts mostly use alumina as a support, supporting active components such as chromium-based and platinum-based catalysts. However, traditional alumina supports suffer from limited specific surface area and unreasonable pore structure, leading to poor dispersion of active components. Simultaneously, under high-temperature dehydrogenation reaction conditions, catalysts are prone to carbon deposition and sintering of active components, resulting in a rapid decline in catalyst activity and insufficient stability. This severely impacts the continuity and economy of industrial production and increases catalyst replacement costs. Summary of the Invention

[0004] The purpose of this invention is to overcome the shortcomings of existing technologies and provide a propane dehydrogenation catalyst, its preparation method, and its application. The propane dehydrogenation catalyst of this invention uses alumina as the main support and metal elements as composite additives. Through the synergistic effect of the composite additives and the alumina support, the activity and stability of the catalyst are improved.

[0005] To achieve the above objectives, the technical solution adopted by the present invention is as follows: In a first aspect, the present invention provides a propane dehydrogenation catalyst, comprising an alumina support and an active component, wherein the framework of the alumina support contains a composite additive; the composite additive is a metal element existing in the form of an oxide, wherein the metal element includes at least two selected from Ca, Mg, Fe, Zr, Na, K, Y, Ga, Ce, and Gd.

[0006] Preferably, the metallic element includes at least three of the following: Ca, Mg, Fe, Zr, Na, K, Y, Ga, Ce, and Gd.

[0007] Preferably, the metallic elements include Ga, Mg, and Na.

[0008] Preferably, the metallic element includes at least two of Fe, Zr, K, and Y.

[0009] Preferably, the metallic element includes at least two of Fe, Na, and Ce.

[0010] Preferably, the metallic element includes at least two of Ca, Ga, and Gd.

[0011] Preferably, the composite additive includes GaO2, MgO, and Na2O, and the mass ratio of GaO2, MgO, and Na2O is (1-3):1:(2-3), for example, it can be 1:1:2, 1.5:1:2, 2:1:2, 2.5:1:2, 3:1:2, 1.5:1:2.4, or any two of these values.

[0012] Preferably, the composite additive includes Fe2O3, ZrO2, Y2O3, and K2O, and the mass ratio of Fe2O3, ZrO2, Y2O3, and K2O is (1~3):(2~4):(2~4):1, for example, 1:2:2:1, 1:2:3:1, 1:2:4:1, 1:3:2:1, 1:3:3:1, 1:3:4:1, 1:4:2:1, 1:4:3:1, 1:4:4:1, 2 :2:2:1, 2:2:3:1, 2:2:4:1, 2:3:2:1, 2:3:3:1, 2:3:4:1, 2:4:2:1, 2:4:3:1, 2:4:4:1, 3:2:2:1, 3:2:3:1, 3:2:4:1, 3:3:2:1, 3:3:3:1, 3:3:4:1, 3:4:2:1, 3:4:3:1, 3:4:4:1, or a range consisting of any two of these values.

[0013] Preferably, the composite additive includes Ce2O3, Na2O, and Fe2O3, and the mass ratio of Ce2O3, Na2O, and Fe2O3 is (3~6):1:(2~4), for example, it can be 3:1:2, 3:1:3, 3:1:4, 4:1:2, 4:1:3, 4:1:4, 5:1:2, 5:1:3, 5:1:4, 6:1:2, 6:1:3, 6:1:4, or any range of two of these values.

[0014] Preferably, the composite additive includes Gd2O3 and CaO, and the mass ratio of Gd2O3 to CaO is 1:(1~5), for example, it can be 1:1, 1:1.5, 1:2, 1:2.5, 1:3, 1:3.5, 1:4, 1:4.5, 1:5 or any two of these values.

[0015] Preferably, the composite additive exists in the form of its corresponding nitrate, carbonate, bicarbonate, or hydroxide, including but not limited to Ca(NO3)2, CaCO3, Ca(HCO3)2, Ca(OH)2, Mg(NO3)2, MgCO3, Mg(HCO3)2, Mg(OH)2, Fe(NO3)3, Fe2(CO3)3, Fe(HCO3)3, Fe(OH)3, Fe(NO3)2, FeCO3, Fe(HCO3)2, Fe(OH)2, Zr(NO3)2, etc. )4. Zr(CO3)2, Zr(HCO3)4, Zr(OH)4, NaNO3, Na2CO3, NaHCO3, NaOH, KNO3, K2CO3, KHCO3, KOH, Y(NO3)3, Y2(CO3)3, Y (HCO3)3, Ga(NO3)4, Ga(CO3)2, Ga(HCO3)4, Ce(NO3)3, Ce2(CO3)3, Ce(HCO3)3, Gd(NO3)3, Gd2(CO3)3, Gd(HCO3)3.

[0016] Preferably, the mass of the alumina support accounts for 60% to 90% of the mass of the propane dehydrogenation catalyst, for example, it can be 60%, 65%, 70%, 75%, 80%, 85%, 90%, or any two of these values.

[0017] Preferably, the active ingredient is a chromium-based or platinum-based oxide.

[0018] Preferably, the active ingredient, calculated as an oxide, accounts for 10% to 30% of the mass of the propane dehydrogenation catalyst, for example, it can be a range of 10%, 12%, 14%, 16%, 18%, 20%, 22%, 24%, 26%, 28%, 30%, or any two of these values. The present invention uses X-ray fluorescence spectrometry (XRF) to determine the mass percentage of the active ingredient.

[0019] Preferably, the composite additive, calculated as an oxide, accounts for 0.05% to 2% of the mass of the propane dehydrogenation catalyst, for example, it can be 0.05%, 0.1%, 0.2%, 0.4%, 0.5%, 0.7%, 0.8%, 1%, 1.2%, 1.5%, 1.8%, 2%, or any two of these values. The mass percentage of the composite additive is determined using X-ray fluorescence spectrometry (XRF).

[0020] Preferably, the mass percentage of alumina in the alumina carrier is 98% to 99.9%, for example, it can be 98%, 98.5%, 99%, 99.5%, 99.9% or any two of these values.

[0021] Preferably, the mass percentage of the composite additive in the alumina carrier is 0.05% to 2.0%, for example, it can be 0.05%, 0.1%, 0.2%, 0.5%, 0.6%, 0.8%, 1.0%, 1.2%, 1.5%, 1.8%, 2.0%, or any two of these values.

[0022] The alumina carrier comprises alumina and composite additives, with a total mass percentage of 100%.

[0023] Preferably, the specific surface area of ​​the propane dehydrogenation catalyst is 85-95 m². 2 / g, with a pore size of 7.0~7.5 nm.

[0024] Preferably, the mass of a single additive in the composite additive is 0.01% to 1% of the mass of the alumina carrier, for example, it can be 0.01%, 0.05%, 0.1%, 0.15%, 0.2%, 0.25%, 0.3%, 0.35%, 0.4%, 0.45%, 0.5%, 0.55%, 0.6%, 0.7%, 0.8%, 0.9%, 1%, or any two of these values.

[0025] This invention can precisely adjust the surface properties and pore structure of the carrier by controlling the amount of a single additive in the composite additive, thereby improving the catalytic performance after loading the active ingredient.

[0026] Secondly, this invention also discloses a method for preparing a propane dehydrogenation catalyst, comprising the following steps: (1) Add aluminum hydroxide and composite additives to water and mix evenly to obtain a suspension. Then adjust the pH of the solution to 3~5, transfer it to a reaction vessel, and crystallize it at 80~120℃ for 12~24 h. After crystallization, filter, wash, dry and calcine the product in the reaction vessel to obtain an alumina carrier. (2) The alumina support is immersed in a solution containing active ingredients, and then dried and calcined to obtain a propane dehydrogenation catalyst.

[0027] Preferably, the mixing time in step (1) is 2 to 4 hours.

[0028] Preferably, the drying temperature in step (1) is 60~80℃ and the drying time is 6~12 h.

[0029] Preferably, in step (1), the calcination temperature is 500~800℃, the heating rate is 2~5℃ / min, and the calcination time is 4~6 h.

[0030] Preferably, the mass of the active ingredient in step (2) is 5% to 40% of the mass of the alumina carrier, for example, it can be 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40% or any two of these values.

[0031] Preferably, the solution containing the active ingredient in step (2) includes at least one of chromium nitrate solution, ammonium dichromate solution, and chromic acid solution.

[0032] Preferably, the drying temperature in step (2) is 60~150℃ and the drying time is 5~6 h.

[0033] Preferably, the roasting temperature in step (2) is 400~800℃ and the roasting time is 2~6 h.

[0034] Thirdly, the present invention also discloses the application of a propane dehydrogenation catalyst as a propane dehydrogenation catalyst.

[0035] Compared with the prior art, the beneficial effects of the present invention are as follows: 1. Synergistic enhancement of activity and stability, resulting in excellent catalytic performance: This invention uses a composite additive composed of metal elements to modify the alumina support. Through the synergistic effect of the additive, support, and active ingredients, on the one hand, due to the Al... 3+ The significant difference in radius between metal ions and alumina ions causes changes in the alumina interface when metal ions enter the crystal lattice, thus affecting the grain growth orientation. Therefore, by controlling the amount of composite additives added, the surface properties and pore structure of the support are optimized by changing the grain growth orientation and the interface bonding mode, improving the dispersibility of active ingredients, reducing the activation energy of propane dehydrogenation, and significantly improving propane conversion and propylene yield. On the other hand, since metal ions can form stable interfacial bonds with alumina support when they enter the crystal lattice, changing the surface acidity can effectively inhibit the formation of carbon deposits and sintering of active ingredients during high-temperature reactions, greatly improving the stability of the catalyst.

[0036] 2. Flexible selection of additives and wide compatibility: The composite additives described in this invention cover a variety of metal nitrates, carbonates, bicarbonates, hydroxides and other forms, and multiple combinations can be flexibly selected according to actual catalytic needs; at the same time, the addition range of composite additives is clearly controlled, which can accurately match the loading requirements of different active ingredients (platinum group, chromium group, etc.), and is compatible with a variety of industrial reaction devices such as fixed bed and moving bed, with a wide range of application scenarios.

[0037] 3. The preparation process is simple and controllable, and easy to scale up industrially: The alumina carrier of the present invention only requires five steps to prepare: "additive mixing - suspension adjustment - crystallization - filtration and drying - calcination". The process steps are simple; the key parameters of each step are reasonable and easy to control, and no complex equipment is required; at the same time, the amount of composite additives added is small and the raw material cost is low. It can be directly adapted to the existing industrial production process and has good prospects for industrial application.

[0038] 4. Excellent economic efficiency and practicality: The improved stability of the propane dehydrogenation catalyst described in this invention extends its service life, reduces the frequency of catalyst replacement in industrial production, and lowers replacement costs and production downtime losses. Moreover, the catalyst preparation adopts mature processes such as conventional impregnation and precipitation methods, which do not require large-scale modification of existing production equipment, further reducing the threshold and cost of industrial application. Detailed Implementation

[0039] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions in the embodiments of this application will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments in this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0040] In this application, the technical features described in an open-ended manner include both closed technical solutions consisting of the listed features and open technical solutions that include the listed features.

[0041] In this application, numerical ranges are referred to as continuous unless otherwise specified, and include the minimum and maximum values ​​of the range, as well as every value between the minimum and maximum values. Furthermore, when the range refers to integers, it includes every integer between the minimum and maximum values ​​of the range. Additionally, when multiple ranges are provided to describe a feature or characteristic, the ranges may be merged. In other words, unless otherwise specified, all ranges disclosed herein should be understood to include any and all subranges to which they are incorporated.

[0042] Unless otherwise specified, all components and raw materials used in the embodiments and comparative examples of this invention are commercially available, and the same type of components and raw materials are used in each parallel experiment.

[0043] Example 1 A method for preparing a propane dehydrogenation catalyst includes the following steps: (1) Preparation of alumina support: S1: Weigh 100g of aluminum hydroxide powder (the aluminum hydroxide powder contains unavoidable silica impurities, China Aluminum AH-1), add composite additives (Ga(NO3)4 0.03g, NaNO3 0.04g and Mg(NO3)2 0.02g), mix and stir for 2h to ensure that the composite additives are fully in contact with the aluminum hydroxide powder and are evenly dispersed; S2: Add 300 mL of deionized water to the mixture obtained in step S1, stir to form a uniform suspension, then adjust the pH of the system to 3 with dilute nitric acid, transfer to a reaction vessel, and crystallize at 80°C for 24 h. S3: After crystallization, filter the product in the reactor, wash the resulting filter cake with deionized water until neutral, and then dry it at 60°C for 12 hours. S4: Place the dried product in a muffle furnace and heat it to 500℃ at a heating rate of 2℃ / min. Calcine for 6 hours to remove easily decomposable components from the composite additives and obtain the alumina carrier.

[0044] (2) Preparation of propane dehydrogenation catalyst: The alumina support prepared above was impregnated in a 30% chromium nitrate solution using an equal-volume impregnation method, and 20 wt% Cr (based on the mass of the alumina support) was loaded onto it. After impregnation for 12 h, it was dried at 80 °C for 6 h and calcined at 550 °C for 4 h to obtain a propane dehydrogenation catalyst.

[0045] In this embodiment, the propane dehydrogenation catalyst comprises the following components by mass percentage: GaO2: 0.03%; MgO: 0.02%; Al2O3: 82.03%; Cr2O3: 17.71%; SiO2: 0.17%; Na2O: 0.04%.

[0046] Example 2 A method for preparing a propane dehydrogenation catalyst includes the following steps: (1) Preparation of alumina support: S1: Weigh 100g of aluminum hydroxide powder (aluminum hydroxide powder contains unavoidable silica impurities, China Aluminum AH-1), add composite additives (Fe(NO3)3 0.4g, Zr(NO3)4 0.3g, Y(NO3)3 0.4g and KNO3 0.3g), mix and stir for 4h to ensure that the composite additives are fully in contact with the aluminum hydroxide powder and are evenly dispersed; S2: Add 400 mL of deionized water to the mixture obtained in step S1, stir to form a uniform suspension, then adjust the pH of the system to 5 with dilute nitric acid, transfer to a reaction vessel, and crystallize at 120°C for 12 h. S3: After crystallization, filter the product in the reactor, wash the resulting filter cake with deionized water until neutral, and then dry it at 80°C for 6 hours. S4: Place the dried product in a muffle furnace and heat it to 600℃ at a heating rate of 5℃ / min. Calcine for 4 hours to remove easily decomposable components from the composite additives and obtain the alumina carrier.

[0047] (2) Preparation of propane dehydrogenation catalyst: The alumina support prepared above was impregnated in a 25% ammonium dichromate solution using an equal-volume impregnation method, and 15 wt% Cr (based on the mass of the alumina support) was loaded. The pH was adjusted to 8 with ammonia water, and after precipitation for 2 hours, the mixture was filtered. The filter cake was dried at 80°C for 8 hours and calcined at 600°C for 5 hours to obtain the propane dehydrogenation catalyst.

[0048] In this embodiment, the propane dehydrogenation catalyst comprises the following components by mass percentage: Fe2O3: 0.27%; ZrO2: 0.42%; Y2O3: 0.38%; K2O: 0.12%; Al2O3: 84.93%; Cr2O3: 13.76%; SiO2: 0.12%.

[0049] Example 3 A method for preparing a propane dehydrogenation catalyst includes the following steps: (1) Preparation of alumina support: S1: Weigh 100g of aluminum hydroxide powder (the aluminum hydroxide powder contains unavoidable silica impurities, China Aluminum AH-1), add composite additives (Ce2(CO3)3 0.4g, NaHCO3 0.1g and FeCO3 0.2g), mix and stir for 3h to ensure that the composite additives are fully in contact with the aluminum hydroxide powder and are evenly dispersed; S2: Add 350 mL of deionized water to the mixture obtained in step S1, stir to form a uniform suspension, then adjust the pH of the system to 4 with dilute nitric acid, transfer to a reaction vessel, and crystallize at 100 °C for 18 h. S3: After crystallization, filter the product in the reactor, wash the resulting filter cake with deionized water until neutral, and then dry it at 70°C for 9 hours. S4: Place the dried product in a muffle furnace and heat it to 550°C at a heating rate of 3°C / min. Calcine for 5 hours to remove easily decomposable components from the composite additives and obtain the alumina carrier.

[0050] (2) Preparation of propane dehydrogenation catalyst: The alumina support prepared above was impregnated in a 35% chromic acid solution using an equal-volume impregnation method, and 25 wt% Cr (based on the mass of the alumina support) was loaded onto it. After impregnation for 10 h, it was dried at 75 °C for 7 h and calcined at 500 °C for 5 h to obtain a propane dehydrogenation catalyst.

[0051] In this embodiment, the propane dehydrogenation catalyst comprises the following components by mass percentage: Ce2O3: 0.40%; Na2O: 0.07%; Fe2O3: 0.21%; Al2O3: 75.86%; Cr2O3: 23.36%; SiO2: 0.10%.

[0052] Example 4 A method for preparing a propane dehydrogenation catalyst includes the following steps: (1) Preparation of alumina support: S1: Weigh 100g of aluminum hydroxide powder (the aluminum hydroxide powder contains unavoidable silica impurities, China Aluminum AH-1), add composite additives (Gd(NO3)30.02g, CaCO30.05g), mix and stir for 2h to ensure that the composite additives are fully in contact with the aluminum hydroxide powder and are evenly dispersed. S2: Add 300 mL of deionized water to the mixture obtained in step S1, stir to form a uniform suspension, then adjust the pH of the system to 3 with dilute nitric acid, transfer to a reaction vessel, and crystallize at 80°C for 24 h. S3: After crystallization, filter the product in the reactor, wash the resulting filter cake with deionized water until neutral, and then dry it at 60°C for 12 hours. S4: Place the dried product in a muffle furnace and heat it to 500℃ at a heating rate of 2℃ / min. Calcine for 6 hours to remove easily decomposable components from the composite additives and obtain the alumina carrier.

[0053] (2) Preparation of propane dehydrogenation catalyst: The alumina support prepared above was impregnated in a 30% chromium nitrate solution using an equal-volume impregnation method, and 20 wt% Cr (based on the mass of the alumina support) was loaded onto it. After impregnation for 12 h, it was dried at 80 °C for 6 h and calcined at 550 °C for 4 h to obtain a propane dehydrogenation catalyst.

[0054] In this embodiment, the propane dehydrogenation catalyst comprises the following components by mass percentage: Gd2O3: 0.02%; CaO: 0.05%; Al2O3: 80.52%; Cr2O3: 19.32%; SiO2: 0.09%.

[0055] Example 5 The difference from Example 1 lies in the preparation of the alumina support in step (1): S1: Weigh 100g of aluminum hydroxide powder (the aluminum hydroxide powder contains unavoidable silica impurities, China Aluminum AH-1), add composite additives (Ga(NO3)40.45g, NaNO30.72g and Mg(NO3)20.33g), mix and stir for 2h to ensure that the composite additives are fully in contact with the aluminum hydroxide powder and are evenly dispersed.

[0056] Comparative Example 1 The difference from Example 1 is that the propane dehydrogenation catalyst is prepared as follows: S1: Add the composite additives (Ga(NO3)4 0.03g, NaNO3 0.04g and Mg(NO3)2 0.02g) to a 30% chromium nitrate solution and mix thoroughly to obtain a mixed solution; S2: Using the equal volume impregnation method, 100g of aluminum hydroxide powder (which contains unavoidable silica impurities, China Aluminum AH-1) was added to a mixed solution for impregnation, and 20wt% Cr (based on the mass of the alumina carrier) was loaded. After impregnation for 12h, it was dried at 80℃ for 6h and calcined at 550℃ for 4h to obtain the propane dehydrogenation catalyst.

[0057] Comparative Example 2 The difference from Example 1 is that the alumina support in step (1) is prepared as follows: S1: Weigh 100g of aluminum hydroxide powder (aluminum hydroxide powder contains unavoidable silica impurities, China Aluminum AH-1), dissolve the composite additive (Ga(NO3)4 0.03g, NaNO3 0.04g and Mg(NO3)2 0.02g) in 300mL of deionized water, mix well to obtain the composite additive solution; S2: Then, the aluminum hydroxide powder is immersed in the composite additive solution and dried at 60°C for 12 hours. After drying, it is placed in a muffle furnace and heated to 500°C at a heating rate of 2°C / min. It is then calcined for 6 hours to remove the easily decomposable components in the composite additive, thus obtaining the alumina carrier.

[0058] Comparative Example 3 The difference from Example 1 is that in step (1), stannous nitrate of equal mass is used to replace NaNO3 and Mg(NO3)2 in the composite additive.

[0059] Comparative Example 4 The difference from Example 1 is that in step (1), Mg(NO3)2 is used to replace Ga(NO3)4 and NaNO3 in the composite additive.

[0060] Comparative Example 5 The difference from Example 1 is that in step (1), Ga(NO3)4 is used in place of Mg(NO3)2 and NaNO3 in the composite additive.

[0061] Comparative Example 6 The difference from Example 1 is that in step (1), NaNO3 of equal mass is used to replace Ga(NO3)4 and Mg(NO3)2 in the composite additive.

[0062] Comparative Example 7 The difference from Example 1 is that in step (1), Ti(NO3)4 of equal mass is used to replace Ga(NO3)4 in the composite additive.

[0063] 1. Catalyst performance testing: The PDH catalytic performance of the prepared propane dehydrogenation catalyst samples was evaluated using a fixed-bed reactor. The specific procedure was as follows: 5g of sample particles were weighed and loaded into a Φ18×2mm quartz tube reactor. First, reduction was performed at 600℃ in a hydrogen atmosphere (42mL / min) for 10 min. Then, the vacuum pump was turned on to reduce the reaction pressure to 0.5 MPa, and the propane feed gas was switched (space velocity 1 h⁻¹) for 1 h. Afterward, N₂ was purged for 1 min, followed by air regeneration for 20 min to complete a single cycle of the reaction. During the reaction, the reactor outlet was sampled and analyzed every 5 min using an online gas chromatograph (GC-F80, Zhejiang Fuli Analytical Instrument Co., Ltd.). Each sample was cycled 15 times. The propane conversion (C) and propylene selectivity (S) were calculated using formulas ①~②. ①C = ((M_i propane - M_o propane) / M_i propane) * 100%; ②S = (M_0 propylene / (M_i propane - M_o propane)) * 100%; Where M_i is the mass ratio of propane in a single feed, M_o is the mass ratio of propane in the effluent, M_0 is the mass ratio of propylene, and the average conversion and selectivity of a single cycle are calculated as the average of 15 samples taken over 1 hour.

[0064] 2. Physical characterization of the catalyst: Nitrogen adsorption-desorption curves were characterized using a TriStar II PLUS 3030 physical adsorption instrument from Micron Technology. Specific surface area was calculated using the BET method, and pore volume and average pore size were calculated using the BJH model.

[0065] 3. Catalyst composition characterization: XRF characterization was performed using a Rigaku ZSX Primus IV X-ray fluorescence spectrometer, with Rh as the target source and Cu and Kα rays as the incident light sources. The catalyst powder was mixed with boric acid and pressurized to 20 tons under hydraulic pressure to form discs for testing.

[0066] X-ray photoelectron spectroscopy (XPS): The surface elemental composition, valence state, and relative abundance of the catalyst samples were analyzed using a Thermo Fisher Scientific VG ESCALAB 250 X-ray photoelectron spectroscopy (EPS) system. The electron binding energy was corrected using the C 1s peak (284.8 eV) of elemental carbon. Peak positions were used to determine whether metal elements had entered the alumina framework lattice. The Al 2p position in alumina is approximately 74.5 eV; doping caused a shift to a higher position, while loading caused a shift to a lower position.

[0067] The test results of the above embodiments and comparative examples are shown in Tables 1 and 2.

[0068] Table 1. Mass percentage (%) of each component in the propane dehydrogenation catalyst According to the XPS test results in Table 1, the metal elements in Examples 1-5 entered the framework lattice of alumina. In contrast, in Comparative Examples 1 and 2, since no crystallization treatment was performed, the metal elements were mainly loaded on the surface of the alumina.

[0069] Table 2 As shown in Examples 1-5 of Table 2, the propane dehydrogenation catalyst, when used in the propane dehydrogenation reaction, achieves a propane conversion rate of over 48% and a propylene selectivity of over 89% after 24 hours of reaction; after 100 hours of reaction, the propane conversion rate reaches over 45%, and the carbon deposition is below 0.9 wt%. This indicates that the propane dehydrogenation catalyst of the present invention has excellent propane dehydrogenation activity and can improve the propane conversion rate; at the same time, it has good stability and can effectively inhibit carbon deposition and sintering of active components during long-term high-temperature dehydrogenation reactions, thus extending the catalyst's service life.

[0070] Comparing Comparative Examples 1-2 with Example 1, it can be seen that in Comparative Example 1, the composite additive and active ingredient were first mixed into a solution before impregnating the aluminum hydroxide powder without crystallization treatment. In Comparative Example 2, the composite additive was prepared into a solution before impregnating the aluminum hydroxide powder without crystallization treatment. The dehydrogenation activity of the propane dehydrogenation catalysts in Comparative Examples 1-2 was not as good as that in Example 1. This indicates that the present invention can effectively suppress the formation of carbon deposits and the sintering of active ingredients during the high-temperature reaction process by having specific metal elements enter the alumina lattice in the form of composite additives to form stable interfacial bonds, thereby improving the propane dehydrogenation activity and thus improving the propane conversion rate.

[0071] Comparing Comparative Examples 4-6 with Example 1, it can be seen that using a single additive in the composite additive will affect the activity of the catalyst. This indicates that the composite additive described in this invention can only improve the propane dehydrogenation activity and thus improve the propane conversion rate by using a composite additive with at least two specific metal elements.

[0072] Comparing Comparative Examples 3 and 7 with Example 1, it can be seen that in Comparative Example 3, stannous nitrate was used to replace NaNO3 and Mg(NO3)2, and in Comparative Example 7, Ti(NO3)4 was used to replace GaO2 and was combined with MgO and Na2O. The dehydrogenation activity of the propane dehydrogenation catalysts in Comparative Examples 3 and 7 was not as good as that in Example 1, indicating that not all additives can achieve the effect of the present invention.

[0073] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the essence and scope of the technical solutions of the present invention.

Claims

1. A propane dehydrogenation catalyst, characterized in that, It includes an alumina carrier and an active ingredient. The framework lattice of the alumina carrier contains a composite additive, which is a metal element existing in the form of an oxide. The metal element includes at least two of Ca, Mg, Fe, Zr, Na, K, Y, Ga, Ce, and Gd.

2. The propane dehydrogenation catalyst according to claim 1, characterized in that, The metallic element includes at least three of the following: Ca, Mg, Fe, Zr, Na, K, Y, Ga, Ce, and Gd. Alternatively, the metallic elements include Ga, Mg, and Na; Alternatively, the metallic element includes at least two of Fe, Zr, K, and Y; Alternatively, the metallic element includes at least two of Fe, Na, and Ce; Alternatively, the metallic element may include at least two of Ca, Ga, and Gd.

3. The propane dehydrogenation catalyst according to claim 2, characterized in that, The composite additive includes GaO2, MgO, and Na2O, and the mass ratio of GaO2, MgO, and Na2O is (1-3):1:(2-3). Alternatively, the composite additive includes Fe2O3, ZrO2, Y2O3 and K2O, and the mass ratio of Fe2O3, ZrO2, Y2O3 and K2O is (1~3):(2~4):(2~4):1; Alternatively, the composite additive includes Ce2O3, Na2O, and Fe2O3, and the mass ratio of Ce2O3, Na2O, and Fe2O3 is (3~6):1:(2~4). Alternatively, the composite additive may include Gd2O3 and CaO, and the mass ratio of Gd2O3 to CaO is 1:(1~5).

4. The propane dehydrogenation catalyst according to claim 1, characterized in that, The alumina support accounts for 60% to 90% of the mass of the propane dehydrogenation catalyst; And / or, calculated as oxides, the active ingredient accounts for 10% to 30% of the mass of the propane dehydrogenation catalyst.

5. The propane dehydrogenation catalyst according to claim 1, characterized in that, The alumina carrier contains 98% to 99.9% alumina by mass, and the composite additive contains 0.05% to 2.0% alumina by mass.

6. The propane dehydrogenation catalyst according to claim 1, characterized in that, The propane dehydrogenation catalyst has a pore size of 7.0~7.5 nm.

7. A method for preparing a propane dehydrogenation catalyst according to any one of claims 1-6, characterized in that, Includes the following steps: (1) Add aluminum hydroxide and composite additives to water and mix evenly to obtain a suspension. Then adjust the pH of the solution to 3~5, transfer it to a reaction vessel, and crystallize it at 80~120℃ for 12~24 h. After crystallization, filter, wash, dry and calcine the product in the reaction vessel to obtain an alumina carrier. (2) The alumina support is immersed in a solution containing active ingredients, and then dried and calcined to obtain a propane dehydrogenation catalyst.

8. The method for preparing the propane dehydrogenation catalyst according to claim 7, characterized in that, In step (1), the drying temperature is 60~80℃ and the drying time is 6~12 h; And / or, in step (1), the calcination temperature is 500~800℃, the heating rate is 2~5℃ / min, and the calcination time is 4~6h.

9. The method for preparing the propane dehydrogenation catalyst according to claim 7, characterized in that, In step (2), the mass of the active ingredient is 5% to 40% of the mass of the alumina carrier; And / or, the solution containing the active ingredient in step (2) includes at least one of chromium nitrate solution, ammonium dichromate solution, and chromic acid solution; And / or, in step (2), the drying temperature is 60~150℃ and the drying time is 5~6 h; And / or, the roasting temperature in step (2) is 400~800℃ and the roasting time is 2~6 h.

10. The use of the propane dehydrogenation catalyst according to any one of claims 1-6 as a propane dehydrogenation catalyst.

Images