A propane oxidative dehydrogenation catalyst containing two-dimensional nanostructures and a method for preparing the same

Abstract

The application discloses a propane oxidative dehydrogenation catalyst containing two-dimensional nano structures and a preparation method thereof, and belongs to the technical field of industrial catalysis. The preparation method of the propane oxidative dehydrogenation catalyst containing two-dimensional nano structures comprises the following steps: placing an ionic compound containing boron in hydrochloric acid at 25-50 DEG C for 24-168 h for peeling, and washing and drying the product to obtain the propane oxidative dehydrogenation catalyst containing two-dimensional nano structures. The method has the advantages of simple process route, low equipment requirement and easy scale-up production. The prepared propane oxidative dehydrogenation catalyst is mainly composed of amorphous boron nanosheets and surface-oxidized boron oxide, can be used without activation, has high stability, good catalytic activity, and a good industrial application prospect. Specifically, under the reaction condition of 530 DEG C, the catalyst can be stably operated for 100 h, the propane conversion rate is maintained at 39.8%, the olefin yield is maintained at 32.6%, and the olefin selectivity can reach 81.9%.

Description

Technical Field

[0001] This invention relates to the field of industrial catalysis technology, specifically to a propane oxidative dehydrogenation catalyst containing a two-dimensional nanostructure and its preparation method. Background Technology

[0002] Propylene, as an important chemical raw material, is widely used in fine chemicals, pharmaceuticals, and polymers, primarily in the production of polypropylene, propylene oxide, acrylonitrile, and acrylic acid. Currently, the main sources of propylene in the market are naphtha cracking and direct propane dehydrogenation. However, these methods are technically complex, involve high reaction temperatures, and consume significant energy. In contrast, propane oxidative dehydrogenation is an exothermic reaction with a low reaction temperature and a simpler process. Furthermore, the catalyst operates in an oxidizing atmosphere, preventing carbon buildup and facilitating its long-term use. Therefore, propane oxidative dehydrogenation has a better market prospect.

[0003] In recent years, scientists have discovered that non-metallic boron-based catalysts exhibit excellent catalytic performance in the oxidative dehydrogenation of propane. For example, in 2016, Hermans et al. found that commercial hexagonal boron nitride (h-BN) showed a 14% propane conversion and a 79% propylene selectivity in the oxidative dehydrogenation of propane to propylene (Grant, JT et al. Selective oxidative dehydrogenation of propane to propene using boron nitride catalysts, Science (2016), doi:10.1126 / science.aaf7885). Subsequently, Chaturbedy et al. designed a boron nitride (BN) catalyst with a high specific surface area, which exhibited a propane conversion of 52% and a propylene selectivity of 53%. However, the catalyst's stability could only be maintained for 5 hours (Chaturbedy, P. et al. Oxidative dehydrogenation of propane over a high surface area boron nitride catalyst: exceptional selectivity for olefins at high conversion, ACS Omega (2018), doi:10.1021 / acsomega.7b01489). Furthermore, Cao et al. also found that h-BN was prone to deactivation at high temperatures. Therefore, they used atomic layer deposition (ALD) to deposit an indium oxide (In₂O₃) layer on the surface of h-BN to improve the stability of the h-BN catalyst (Cao, L. et al. Antiexfoliating h-BN). In2O3 catalyst for oxidativedehydrogenation of propane in a high-temperature and water-rich environment, Journal of the American Chemical Society (2023), doi:10.1021 / jacs.2c12136).

[0004] Chinese patent document CN110668407A discloses a method for preparing rod-shaped hexagonal boron nitride foam. The invention uses boric acid and melamine as raw materials and utilizes polymerized boric acid and melamine precursors to generate porous rod-shaped hexagonal boron nitride foam during high-temperature annealing. The foam is composed of rod-shaped hexagonal boron nitride structures with interconnected pores (approximately 100 nm). This pore structure is conducive to gas flow and diffusion and has good potential as a heterogeneous catalyst.

[0005] Although h-BN is considered the most promising catalyst for the oxidative dehydrogenation of propane, its stability is poor, and improving the stability of h-BN catalysts is technically complex, has low yield, and is not conducive to large-scale production and industrial use. Therefore, there is an urgent need to develop a catalyst for the oxidative dehydrogenation of propane with good stability and high catalytic activity. Summary of the Invention

[0006] This invention provides a method for preparing a propane oxidative dehydrogenation catalyst containing a two-dimensional nanostructure. The method has a simple process route and low equipment requirements. The prepared propane oxidative dehydrogenation catalyst can operate stably at 530℃ for 100 hours, with the propane conversion rate maintained at 39.8% and the olefin (propylene + ethylene) yield reaching 32.6%, and the olefin selectivity reaching 81.9%, showing good prospects for industrial application.

[0007] The specific technical solution adopted is as follows:

[0008] A method for preparing a propane oxidative dehydrogenation catalyst containing a two-dimensional nanostructure includes the following steps: placing a boron-containing ionic compound in hydrochloric acid at 25-50°C for 24-168 hours for exfoliation, and washing and drying the product to obtain the propane oxidative dehydrogenation catalyst containing a two-dimensional nanostructure.

[0009] After etching with hydrochloric acid, the interspersed metal layers in the boron-containing ionic compound are stripped away, transforming it into an amorphous structure containing a large number of boron nanosheets. Due to the absence of metal in the structure, a large amount of boron is oxidized, thus providing sufficient active sites for the subsequent propane oxidative dehydrogenation reaction.

[0010] Preferably, the boron-containing ionic compound includes MgB2 or AlB2.

[0011] Preferably, the concentration of the hydrochloric acid is 1-12 mol / L, and the ratio of the boron-containing ionic compound to the hydrochloric acid is 1 g: 100-400 mL. Under the above-mentioned preferred preparation conditions, the prepared propane oxidative dehydrogenation catalyst exhibits high catalytic activity and good stability.

[0012] Preferably, the stripping process is carried out under an inert gas atmosphere, specifically a nitrogen atmosphere. A nitrogen atmosphere helps prevent premature oxidation of the product catalyst during use.

[0013] Preferably, stirring is used during the hydrochloric acid stripping process to ensure complete stripping, and the stirring speed is preferably 300-500 r / min.

[0014] The present invention also provides a method for preparing a propane oxidative dehydrogenation catalyst containing a two-dimensional nanostructure, and the resulting propane oxidative dehydrogenation catalyst containing a two-dimensional nanostructure.

[0015] The propane oxidative dehydrogenation catalyst containing a two-dimensional nanostructure is mainly composed of amorphous boron nanosheets and surface-oxidized boron oxide, and can be used without activation.

[0016] Preferably, the particle size of the propane oxidative dehydrogenation catalyst containing a two-dimensional nanostructure is 80-100 mesh.

[0017] The present invention also provides a method for producing propylene by propane dehydrogenation, wherein a propane-containing feed gas is passed into a reactor containing the aforementioned propane oxidative dehydrogenation catalyst with a two-dimensional nanostructure, and the reaction is carried out to obtain propylene.

[0018] Preferably, in the method for producing propylene from propane dehydrogenation, C3H8 and O2 are used as reactant gases, N2 is used as equilibrium gas, the flow ratio of C3H8 to O2 is 0.5-2:1, the space velocity is 6000-24000 mL / (gh), the reaction temperature is 500-540℃, and the reaction pressure is 0.1 MPa.

[0019] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0020] (1) Compared with boron-based catalysts in the prior art, the method of the present invention uses hydrochloric acid to etch boron-containing ionic compounds to obtain propane oxidative dehydrogenation catalyst. The preparation method is simple, the equipment requirements are low, and it is easy to scale up production.

[0021] (2) The propane oxidative dehydrogenation catalyst with two-dimensional nanostructures provided by the present invention is obtained by hydrochloric acid exfoliation of boron-containing ionic compounds. It contains a large number of boron nanosheet structures. Due to the absence of the metal layer, the highly electronegative boron is easily oxidized, thereby forming a large number of active sites BO. x This lays the foundation for subsequent propane oxidative dehydrogenation and avoids the additional activation process required for boron-based catalysts.

[0022] (3) The propane oxidative dehydrogenation catalyst with two-dimensional nanostructure provided by the present invention has high stability and good catalytic activity. It can effectively reduce the reaction temperature of propane oxidative dehydrogenation. Under the reaction conditions of 530℃, the yield of olefin (propylene + ethylene) of the catalyst can reach 32.6%, the propane conversion rate can reach 39.8%, and the olefin selectivity can reach 81.9%. Attached Figure Description

[0023] Figure 1 The image shows a TEM image of the propane oxidative dehydrogenation catalyst Mg-BNSs with a two-dimensional nanostructure prepared in Example 1. In the image, A is a multilayer nanosheet structure of Mg-BNSs, B is a single-layer nanosheet structure of Mg-BNSs, and C is a selected area diffraction pattern of A.

[0024] Figure 2 The image shows the X-ray diffraction pattern of Mg-BNSs, a propane oxidative dehydrogenation catalyst with a two-dimensional nanostructure, prepared in Example 1.

[0025] Figure 3 This is a schematic diagram of the catalytic performance of the propane oxidative dehydrogenation catalyst Mg-BNSs with a two-dimensional nanostructure prepared in Example 1. In the diagram, A is the catalytic performance data of Mg-BNSs at 530℃, and B is the long-term stability data of Mg-BNSs at 530℃.

[0026] Figure 4 This is a TEM image of Al-BNSs, a propane oxidative dehydrogenation catalyst with a two-dimensional nanostructure, prepared in Example 2.

[0027] Figure 5 This is a schematic diagram of the long-term catalytic stability of the propane oxidative dehydrogenation catalyst Al-BNSs with two-dimensional nanostructures prepared in Example 2 at 530°C.

[0028] Figure 6 This is a schematic diagram of the long-term catalytic stability of the propane oxidative dehydrogenation catalyst h-BN in Comparative Example 1 at 530℃.

[0029] Figure 7 This is a schematic diagram showing the catalytic performance of the propane oxidative dehydrogenation catalyst MgB2 in Comparative Example 2 at different temperatures.

[0030] Figure 8This is a schematic diagram showing the long-term catalytic stability of the propane oxidative dehydrogenation catalyst AlB2 in Comparative Example 3 at 530℃. Detailed Implementation

[0031] In view of the deficiencies of the prior art, the inventors of this case, through long-term research and extensive practice, have proposed the technical solution of this invention. The technical solution of this invention will be clearly and completely described below. Obviously, the described embodiments are only some, not all, of the embodiments of this invention. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0032] In the examples and comparative examples, magnesium diboride (MgB2) was purchased from Ron Company, aluminum diboride (AlB2) was purchased from Shanghai Jizhi Biochemical Technology Co., Ltd., hydrochloric acid was purchased from Sinopharm Chemical Reagent Co., Ltd., and hexagonal boron nitride (h-BN) was purchased from Ron Company.

[0033] Example 1

[0034] 1 g of magnesium diboride (MgB2) was dissolved in a three-necked flask containing 100 mL of hydrochloric acid (12 mol / L). The flask was placed in an oil bath at a constant temperature of 30°C, and magnetic stirring was started under a nitrogen atmosphere at a speed of 400 r / min. The reaction was continued for 24 h for stripping. The product was washed twice with ethanol and dried in a vacuum drying oven to obtain the propane oxidative dehydrogenation catalyst containing a two-dimensional nanostructure (denoted as Mg-BNSs).

[0035] The propane oxidative dehydrogenation reaction was carried out in an atmospheric pressure flow reactor. The Mg-BNSs catalyst was ground and sieved, and 50 mg of 80-100 mesh Mg-BNSs catalyst was placed in a quartz tube. C3H8 and O2 were introduced as reactant gases, and N2 was introduced as the equilibrium gas at a flow rate of 20 mL / min. The reactor temperature was then programmed to rise to 530 °C using electronic temperature control. The flow ratio of C3H8 to O2 was 1:1 (molar ratio), the space velocity was 24000 mL / (gh), and the reaction pressure was 0.1 MPa. The product was monitored in real time by gas chromatography.

[0036] TEM images of the propane oxidative dehydrogenation catalyst Mg-BNSs containing two-dimensional nanostructures prepared in this embodiment are shown below. Figure 1 As shown in A, after MgB2 is etched with hydrochloric acid, Mg-BNSs exhibits a multilayer nanosheet stacked structure. Figure 1 B in the text represents a monodisperse Mg-BNSs nanosheet structure. Figure 1 The C in the figure proves that the structure of the nanosheets is mainly amorphous. Its X-ray diffraction (XRD) pattern is shown below. Figure 2As shown, due to the removal of the metal layer, the strong electronegativity of the boron layer makes it readily combine with oxygen, thus forming trace amounts of boron oxide (B₂O₃, B₆O). The catalytic performance of this Mg-BNSs catalyst for the oxidative dehydrogenation of propane is as follows: Figure 3 As shown in Figure A, this catalyst, at 530°C, achieves a propane conversion of 39.8%, a propylene selectivity of 63.5%, and an ethylene selectivity of 18.4%. Figure 3 As shown in B, the catalyst maintains stability at 530°C for up to 100 hours and still retains an olefin (propylene + ethylene) selectivity of over 80%, with an olefin yield of up to 32.6%.

[0037] Example 2

[0038] 1 g of aluminum diboride (AlB2) was dissolved in a three-necked flask containing 100 mL of hydrochloric acid (12 mol / L). The flask was placed in an oil bath at a constant temperature of 30°C, and magnetic stirring was started under a nitrogen atmosphere at a speed of 400 r / min. The reaction was continued for 24 h for exfoliation. The product was washed twice with ethanol and dried in a vacuum drying oven to obtain the propane oxidative dehydrogenation catalyst containing a two-dimensional nanostructure (denoted as Al-BNSs).

[0039] The propane oxidative dehydrogenation reaction was carried out in an atmospheric pressure flow reactor. The Al-BNSs catalyst was ground and sieved, and 50 mg of 80-100 mesh Al-BNSs catalyst was placed in a quartz tube. C3H8 and O2 were introduced as reactant gases, and N2 was introduced as the equilibrium gas at a flow rate of 20 mL / min. The reactor temperature was then programmed to rise to 530 °C using electronic temperature control. The flow ratio of reactant gases C3H8 to O2 was 1:1 (molar ratio), the space velocity was 24000 mL / (gh), and the reaction pressure was 0.1 MPa. The product was monitored in real time by gas chromatography.

[0040] TEM images of the propane oxidative dehydrogenation catalyst Al-BNSs containing two-dimensional nanostructures prepared in this embodiment are shown below. Figure 4 As shown, after AlB2 was etched with hydrochloric acid, Al-BNSs also formed a nanosheet structure; the performance of Al-BNSs catalyst for propane oxidative dehydrogenation is as follows: Figure 5 As shown, the catalyst achieves a propane conversion rate of 42% and an olefin (propylene + ethylene) selectivity of up to 80% at 530℃, with an olefin yield of up to 33.6%, and can operate stably for up to 100 hours under reaction conditions at 530℃.

[0041] Example 3

[0042] 1 g of magnesium diboride (MgB2) was dissolved in a three-necked flask containing 100 mL of hydrochloric acid (12 mol / L). The flask was placed in an oil bath at a constant temperature of 30 °C, and magnetic stirring was started under a nitrogen atmosphere at a stirring speed of 400 r / min. The reaction was carried out for 168 h for stripping. The product after the reaction was washed twice with ethanol and dried in a vacuum drying oven to obtain the propane oxidative dehydrogenation catalyst containing a two-dimensional nanostructure.

[0043] The propane oxidative dehydrogenation reaction was carried out on an atmospheric pressure flow reactor. The catalyst obtained in the above steps was ground and sieved. 50 mg of the catalyst with a mesh size of 80-100 was placed in a quartz tube. C3H8 and O2 were introduced as reaction gases, and N2 was introduced as the equilibrium gas at a flow rate of 20 mL / min. The reactor temperature was then programmed to rise to 530 °C using electronic temperature control. The flow ratio of C3H8 to O2 was 1:1 (molar ratio), the space velocity was 24000 mL / (gh), and the reaction pressure was 0.1 MPa. The product was monitored in real time by gas chromatography.

[0044] Example 4

[0045] 1 g of magnesium diboride (MgB2) was dissolved in a three-necked flask containing 100 mL of hydrochloric acid (2 mol / L). The flask was placed in an oil bath at a constant temperature of 50 °C, and magnetic stirring was started under a nitrogen atmosphere at a stirring speed of 400 r / min. The reaction was continued for 24 h for stripping. The product after the reaction was washed twice with ethanol and dried in a vacuum drying oven to obtain the propane oxidative dehydrogenation catalyst containing a two-dimensional nanostructure.

[0046] The propane oxidative dehydrogenation reaction was carried out on an atmospheric pressure flow reactor. The catalyst obtained in the above steps was ground and sieved. 50 mg of the catalyst with a mesh size of 80-100 was placed in a quartz tube. C3H8 and O2 were introduced as reaction gases, and N2 was introduced as the equilibrium gas at a flow rate of 20 mL / min. The reactor temperature was then programmed to rise to 530 °C using electronic temperature control. The flow ratio of C3H8 to O2 was 1:1 (molar ratio), the space velocity was 24000 mL / (gh), and the reaction pressure was 0.1 MPa. The product was monitored in real time by gas chromatography.

[0047] Comparative Example 1

[0048] The propane oxidative dehydrogenation reaction was carried out on an atmospheric pressure flow reactor. A commercially available hexagonal boron nitride (h-BN) catalyst was ground and sieved. 50 mg of 80-100 mesh h-BN catalyst was placed in a quartz tube, and C3H8 and O2 were introduced as reactant gases, with N2 as the equilibrium gas, at a flow rate of 20 mL / min. The reactor temperature was then controlled to rise to 530 °C, with a C3H8 to O2 flow rate ratio of 1:1 (molar ratio), a space velocity of 24000 mL / (gh), and a reaction pressure of 0.1 MPa. The product was monitored in real time by gas chromatography.

[0049] The long-term stability catalytic performance of the commercial catalyst h-BN in this comparative example for the oxidative dehydrogenation of propane is as follows: Figure 6 As shown, the catalyst was operated at a reaction temperature of 530°C for 14 hours, and the propane conversion rate decreased from 26% to 16%.

[0050] Comparative Example 2

[0051] The propane oxidative dehydrogenation reaction was carried out on an atmospheric pressure flow reactor. Purchased MgB2 material was ground and sieved. 50 mg of 80-100 mesh MgB2 material was placed in a quartz tube. C3H8 and O2 were introduced as reaction gases, and N2 was introduced as the equilibrium gas at a flow rate of 20 mL / min. The reactor temperature was then controlled to rise to 500℃-540℃. The flow ratio of reaction gases C3H8 and O2 was 1:1 (molar ratio), the space velocity was 24000 mL / (gh), and the reaction pressure was 0.1 MPa. The product was monitored in real time by gas chromatography.

[0052] The catalyst in this comparative example exhibits the following catalytic conversion performance for the oxidative dehydrogenation of propane: Figure 7 As shown, the catalyst achieves a propane conversion rate of only 7% under high-temperature reaction conditions of 540°C.

[0053] Comparative Example 3

[0054] The propane oxidative dehydrogenation reaction was carried out on an atmospheric pressure flow reactor. The purchased AlB2 material was ground and sieved. 50 mg of 80-100 mesh AlB2 material was placed in a quartz tube, and C3H8 and O2 were introduced as reaction gases, with N2 as the equilibrium gas. The flow rate was 20 mL / min. The reactor temperature was then controlled to rise to 530 °C. The flow ratio of C3H8 to O2 was 1:1 (molar ratio), the space velocity was 24000 mL / (gh), and the reaction pressure was 0.1 MPa. The product was monitored in real time by gas chromatography.

[0055] The catalyst in this comparative example exhibits long-term stability catalytic performance for the oxidative dehydrogenation of propane under reaction conditions of 530℃, as shown in the following figure. Figure 8 As shown, the catalyst was operated at a reaction temperature of 530℃ for 70 h, during which the propane conversion decreased from 37% to 26%.

[0056] The embodiments described above provide a detailed explanation of the technical solutions of the present invention. It should be understood that the above descriptions are merely specific embodiments of the present invention and are not intended to limit the present invention. Any modifications, additions, or similar substitutions made within the scope of the principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for producing propylene by propane dehydrogenation, characterized in that, Propane-containing feed gas is passed into a reactor containing a propane oxidative dehydrogenation catalyst with a two-dimensional nanostructure, and the reaction is carried out to obtain propylene. The preparation method of the propane oxidative dehydrogenation catalyst containing two-dimensional nanostructures includes the following steps: placing a boron-containing ionic compound in hydrochloric acid at 25-50 °C for 24-168 h for exfoliation, and washing and drying the product to obtain the propane oxidative dehydrogenation catalyst containing two-dimensional nanostructures. The boron-containing ionic compound is selected from MgB2 or AlB2; The concentration of the hydrochloric acid is 1-12 mol / L, and the ratio of the boron-containing ionic compound to the hydrochloric acid is 1 g: 100-400 mL; The stripping process is carried out in an inert gas atmosphere, namely a nitrogen atmosphere. During the peeling process, stirring is performed at a speed of 300-500 r / min. C3H8 and O2 were used as reactants, and N2 was used as the equilibrium gas. The molar ratio of C3H8 to O2 was 0.5-2:1, the space velocity was 6000-24000 mL / (gh), the reaction temperature was 500-540 ℃, and the reaction pressure was 0.1 MPa.

2. The method for producing propylene from propane by dehydrogenation according to claim 1, characterized in that, The propane oxidative dehydrogenation catalyst containing a two-dimensional nanostructure has a particle size of 80-100 mesh.

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