High-stability boron-based catalyst based on rare earth ion bridging anchoring and preparation method and low-carbon alkane dehydrogenation application thereof

Abstract

The invention discloses a high-stability boron-based catalyst based on rare earth ion bridging anchoring and a preparation method and low-carbon alkane dehydrogenation application thereof.The catalyst comprises a gamma-Al2O3 carrier, a rare earth metal oxide intermediate layer and a B2O3 active component, the rare earth metal oxide intermediate layer and the B2O3 active component are sequentially loaded on the carrier, rare earth metal is at least one of Gd, Ce, La and Y, and the B2O3 active component is a boron oxide active component. The loading capacity of the rare earth metal oxide in the catalyst is 5-30%, and the loading capacity of B2O3 is 5-35%. According to the preparation method, a rare earth ion mediated bridging anchoring system is constructed, so that the problem of weak interface bonding force between a traditional alumina carrier and a B-O active phase is solved, rare earth elements are adopted to form high-density anchoring sites on the surface of the carrier, further B2O3 is loaded, a B2O3 active phase-rare earth bridge-carrier three-dimensional stable framework is formed, and the B2O3 active phase-rare earth bridge-carrier three-dimensional stable structure is formed. The catalyst provided by the invention has high stability in low-carbon alkane dehydrogenation, and has important industrial application prospects.

Description

Technical Field

[0001] The present invention relates to the technical field of thermal catalysis, and particularly to a preparation technology of a highly stable boron-based catalyst based on rare earth ion bridging and anchoring and its application in the dehydrogenation of light alkanes. Background Art

[0002] As one of the most important basic raw materials in modern petrochemical industry, propylene is mainly used for the production of high-value-added chemicals such as polypropylene (accounting for 65%) and acrylonitrile (12%) (Green Chemistry, 2021, 23(24): 9747-9799). Currently, about 70% of the propylene supply in the industry depends on naphtha steam cracking and refinery FCC by-product processes. However, these two technical routes have inherent defects such as low propylene yield (usually <25%) and high energy consumption (>25 GJ / ton of propylene) (Fuel, 2022, 321: 124089; Chemical reviews 114.20 (2014): 10613-10653; Chem. Rev., 2014, 114, 10613-10653).

[0003] Among many propane conversion processes, the propane oxidative dehydrogenation (ODHP) technology exhibits significant advantages due to its unique reaction mechanism: by introducing an oxidant, this technology can break the thermodynamic equilibrium limitation, and the single-pass conversion rate can be increased to more than 50%; the oxidative reaction environment can effectively inhibit carbon deposition, and the continuous operation time of the catalyst is extended by 5-8 times compared with the direct dehydrogenation process; at the same time, the exothermic reaction characteristics reduce the comprehensive energy consumption by 30-40%. These technical and economic advantages make ODHP regarded as the next-generation propane conversion technology with the most potential for industrialization.

[0004] In terms of the selection of catalyst systems, although traditional transition metal oxides (such as V-Mo-Fe-based catalysts) have relatively high intrinsic activity, their strong oxidizing property leads to serious over-oxidation problems. The propylene selectivity is generally lower than 60%, and the active components are prone to sintering at high temperatures. In contrast, boron-based catalysts exhibit unique catalytic performance advantages in the propane oxidative dehydrogenation reaction. Specifically: i) Selectivity advantage: Due to the strong C-H bond activation ability of transition metal oxide catalysts, propane is often over-oxidized to produce CO xBy-products, and the propylene selectivity is generally less than 60%; while boron-based catalysts (such as B2O3, h-BN, etc.) can effectively inhibit deep oxidation due to their moderate surface acidity and special B-O active sites, and the propylene selectivity can be increased to more than 80% (Science, 2016, 354(6319): 1570-1573.); ii) Anti-coking performance: Transition metal catalysts are prone to deactivate due to coking during the reaction and usually require frequent regeneration; while the boric acid species formed on the surface of boron-based materials can inhibit carbon deposition and significantly extend the catalyst life. iii) Structural stability: Transition metal oxides are prone to phase transformation or sintering at high temperatures, while boron species can form a stable dispersed structure on the carrier surface, such as BO3 triangular units or BO4 tetrahedrons, which is beneficial to maintaining the stability of active sites (Angewandte Chemie International Edition, e202507525; Catalysis Today, 2022, 402: 248-258.). However, there are still two key technical bottlenecks in existing boron-based catalysts: one is the insufficient density of active sites, resulting in a low volume-time space yield; the other is that boron species are prone to volatilization and loss at high temperatures, seriously affecting the long-term stability of the catalyst.

[0005] To address the above technical problems, the present invention constructs an anchoring site using a rare earth metal-alumina composite carrier. Utilizing the interfacial structure formed by rare earth metals and the γ-Al2O3 carrier, a high-density anchoring site is provided for boron species; adopting a crystal growth technology controlled by gradient temperature, the highly dispersed B2O3 is successfully achieved, and excellent catalytic performance (propane conversion rate > 40%, olefin selectivity > 80%) and long-term stability (stable operation at 520 °C > 200 h) are demonstrated in the oxidative dehydrogenation of propane (ODHP) reaction, providing key material support for the industrial application of ODHP technology. Summary of the Invention

[0006] The present invention aims to solve the technical problems existing in supported boron oxide catalysts in the prior art, such as low dispersion, insufficient exposure of active sites, and poor high-temperature stability, and provides a highly stable boron-based catalyst based on rare earth ion bridging anchoring and a preparation method thereof.

[0007] To address the aforementioned technical problems, the present invention is achieved through the following technical solutions: A highly stable boron-based catalyst based on rare earth ion bridging anchoring, comprising a γ-Al2O3 carrier, a rare earth metal oxide intermediate layer sequentially loaded on the carrier, and a B2O3 active component, wherein the rare earth metal is at least one of Gd, Ce, La, and Y, the loading amount of the rare earth metal oxide in the catalyst is 5-30%, and the loading amount of B2O3 is 5-35%.

[0008] Further, the loading amount of rare earth metal oxide in the catalyst is 15-20%, and the loading amount of B2O3 is 10-33%.

[0009] Further, the specific surface area of the γ-Al2O3 is 50-300 m² / g, and the average pore diameter is 15-25 nm.

[0010] The preparation method of a highly stable boron-based catalyst based on rare earth ion bridging and anchoring includes the following steps: S1: Prepare an aqueous solution of nitrate of rare earth metal M, where rare earth metal M is at least one of Gd, Ce, La, and Y, to obtain solution A; S2: Immerse the γ-Al2O3 support in solution A of step S1, dry it after sufficient immersion, and then transfer it to a muffle furnace for high-temperature calcination to obtain a support precursor modified with rare earth metal M oxide; S3: Immerse the precursor of step S2 in boric acid aqueous solution, dry it after sufficient immersion, and then transfer it to a muffle furnace for high-temperature calcination to obtain the final catalyst.

[0011] Further, in step S2 or S3, the calcination temperature is 400-700 °C, and the calcination time is 1-4 h.

[0012] Further, in step S2 or S3, the calcination temperature is 500-600 °C, and the calcination time is 1-3 h.

[0013] The present invention also discloses the application of the highly stable boron-based catalyst based on rare earth ion bridging and anchoring in the catalytic oxidative dehydrogenation reaction of light alkanes.

[0014] Further, the light alkane is propane. The catalyst is loaded into a fixed-bed reactor, and the reaction gas is a C3H8-O2-N2 mixed gas with a volume ratio of 1:(0.5-1.5):(1-9). At the catalytic reaction temperature, the reaction gas is introduced into the catalyst bed layer to carry out the catalytic oxidative dehydrogenation reaction of propane. The catalytic reaction temperature is 450-550 °C, the reaction pressure is atmospheric pressure, and the reaction space velocity is 10000-40000 mL / (g cat ·h).

[0015] Further, the catalytic reaction temperature is 520-525 °C, and the reaction space velocity is 15000-20000 mL / (g cat ·h).

[0016] The beneficial effects of the present invention are as follows: 1) The present invention innovatively overcomes the key technical problems of low dispersion, poor thermal stability, and insufficient catalytic activity of existing boron oxide catalysts, and successfully develops a supported boron oxide catalyst with high dispersion characteristics. This catalyst exhibits excellent catalytic performance (propane conversion rate > 40%, olefin selectivity > 80%) and long-term stability (stable operation at 520 °C for > 200 h) in the oxidative dehydrogenation of propane (ODHP) reaction, providing a breakthrough solution for the industrial application of boron-based catalytic materials and having important value for promoting the development of low-carbon alkane efficient conversion technology.

[0017] 2) This invention patent proposes a new strategy for designing highly stable catalysts based on the strengthening of rare earth ion interfacial bonding. By constructing a "rare earth ion-mediated bridging and anchoring" system, the problem of weak interfacial binding force between traditional alumina carriers and B-O active phases is solved. Specifically, the surface island modification technology of rare earth elements (such as Gd, Ce, La, Y, etc.) is adopted to form high-density anchoring sites on the carrier surface, and the chemical locking of active sites is achieved through the B-O-REE-Al quaternary bridge bonding structure, where REE represents rare earth metals, forming a three-dimensional stabilization framework of "B2O3 active phase - rare earth bridge - carrier", and this catalyst has good catalytic stability. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 is the N2 adsorption-desorption isotherm of γ-Al2O3 and the corresponding pore size distribution curve.

[0019] Figure 2A is the average reaction result of the 10 wt%B2O3 / γ-La2O3 catalyst in Example 1 within 2 h of catalytic reaction at temperatures of 470 °C and 490 °C.

[0020] Figure 2B is the average reaction result of the 10 wt%B2O3 / γ-Gd2O3 catalyst in Example 1 within 2 h of catalytic reaction at a temperature of 470 °C.

[0021] Figure 2C is the reaction result of the 10 wt%B2O3 / γ-Y2O3 catalyst in Example 1 at different catalytic temperatures with the reaction time.

[0022] Figure 2D is the reaction result of the 10 wt%B2O3 / γ-CeO2 catalyst in Example 1 at different catalytic temperatures with the reaction time.

[0023] Figure 3 is the average reaction result of 7 catalysts with different B2O3 loadings in Example 2 within 2 h of catalytic reaction at a temperature of 520 °C.

[0024] Figure 4A These are the reaction results of the catalytic temperature, propane conversion, and target product selectivity of the 33 wt%B2O3 - 5 wt%CeO2 / γ-Al2O3 catalyst in Example 3 at different catalytic times.

[0025] Figure 4B These are the reaction results of the catalytic temperature, propane conversion, and target product selectivity of the 33 wt%B2O3 - 10 wt%CeO2 / γ-Al2O3 catalyst in Example 3 at different catalytic times.

[0026] Figure 4C These are the reaction results of the catalytic temperature, propane conversion, and target product selectivity of the 33 wt%B2O3 - 20 wt%CeO2 / γ-Al2O3 catalyst in Example 3 at different catalytic times.

[0027] Figure 4D These are the reaction results of the catalytic temperature, propane conversion, and target product selectivity of the 33 wt%B2O3 - 30 wt%CeO2 / γ-Al2O3 catalyst in Example 3 at different catalytic times.

[0028] Figure 5 These are the catalytic reaction temperature conditions and reaction results of the catalytic reaction of the 33 wt% B2O3 - 10 wt% MgO / γ-Al2O3 catalyst in Comparative Example 1 at different catalytic times.

[0029] Figure 6 These are the catalytic reaction temperature conditions and reaction results of the catalytic reaction of the 33 wt% B2O3 - 10 wt% ZrO2 / γ-Al2O3 catalyst in Comparative Example 2 at different catalytic times.

[0030] Figure 7 These are the catalytic reaction temperature conditions and reaction results of the catalytic reaction of the 33 wt%B2O3 - 10wt%ZnO / γ-Al2O3 catalyst in Comparative Example 3 at different catalytic times.

[0031] Figures 2C - 2D , Figures 4A - 4D and Figures 5 - 7 In, the selectivity on the vertical axis represents the total olefin selectivity of "propylene + ethylene". Detailed implementation manners

[0032] It should be noted that the embodiments described in this article are only exemplary embodiments of the technical solutions of the present invention, and do not represent an exhaustive list of the protection scope. The detailed description of the embodiments in this part is intended to help understand the core principles and implementation methods of the present invention, rather than limiting the scope of the claims. It should be understood that based on the technical concepts disclosed in this specification, any technical solutions obtained by those skilled in the art through equivalent substitution, conventional experiments, or technical extension without creative efforts should be regarded as falling within the protection scope of the present invention.

[0033] In the following examples, a fixed-bed reactor and an on-line gas chromatography system were used for real-time detection (fixed-bed model and manufacturer: Betterwork Xiamen Baidewo Intelligent Technology Co., Ltd.; on-line chromatography model and manufacturer: GC2060 Shanghai Ruimin Instruments Co., Ltd.).

[0034] The N2 adsorption-desorption isotherms and the corresponding pore size distribution curves of the γ-Al2O3 carriers used in the examples and comparative examples of the present invention are as Figure 1 shown. It can be seen that the specific surface area of γ-Al2O3 is 129.6 m² / g, the average pore diameter is 20.6 nm, and the type of adsorption-desorption curve is: type II.

[0035] Example 1. Catalytic experiment comparison of catalysts with different carriers 1. Preparation of catalysts with different metal oxide carriers, including the following steps: a) Preparation of boric acid solution: Weigh 177.6 mg of boric acid (H3BO3) and dissolve it in 8 mL of deionized water at 80 °C, stir until completely dissolved to obtain a boric acid solution.

[0036] b) Excessive volume impregnation: Add 1 g of the carrier to the above boric acid solution, continuously stir in a water bath at 80 °C until the water is completely evaporated.

[0037] c) Drying and calcination: Place the impregnated sample in a hot air drying oven at 80 °C and dry for 12 h, then transfer it to a muffle furnace, heat it to 550 °C at a heating rate of 5 °C / min, and calcine at this temperature for 2 h, and naturally cool to room temperature to finally prepare the catalyst.

[0038] According to the above catalyst preparation process, when the carrier in step b) is La2O3, Gd2O3, Y2O3, or CeO2 respectively, a series of catalysts with different carriers are prepared: 10 wt%B2O3 / La2O3, 10 wt%B2O3 / Gd2O3, 10 wt%B2O3 / Y2O3, 10 wt%B2O3 / CeO2.

[0039] 2. Propane oxidative dehydrogenation activity test The catalytic performance was evaluated using a fixed-bed reactor (quartz tube inner diameter 6 mm). 100 mg of the catalyst was mixed with an equal mass of quartz sand (60 - 80 mesh) and loaded in the middle of the reaction tube, and then heated to the catalytic reaction temperature. The reaction gas composition was C3H8:O2:N2 (volume ratio = 1:1:4), and the total flow rate was 30 mL / min, with nitrogen as the dilution gas. The reaction mass space velocity (WHSV) was 18,000 mL / (g cat ·h). The reaction products were monitored in real time by on-line gas chromatography (equipped with TCD and FID detectors).

[0040] According to the above catalytic reaction process, the average reaction results of the 10 wt%B2O3 / γ-La2O3 catalyst within 2 h of catalytic reaction at catalytic reaction temperatures of 470 °C and 490 °C are shown in Figure 2A shown. The average reaction results of the 10 wt%B2O3 / γ-Gd2O3 catalyst within 2 h of catalytic reaction at a catalytic reaction temperature of 470 °C are shown in Figure 2B shown.

[0041] The reaction results of the 10 wt%B2O3 / γ-Y2O3 catalyst at different catalytic temperatures with reaction time are shown in Figure 2C . From Figure 2C it can be seen that after 32.5 h of catalytic reaction time, the propane conversion rate decreased rapidly, indicating that the 10 wt%B2O3 / γ-Y2O3 catalyst has insufficient stability.

[0042] The reaction results of the 10 wt%B2O3 / γ-CeO2 catalyst at different catalytic temperatures with reaction time are shown in Figure 2D .

[0043] From Figures 2A - 2D the comparison of the reaction results, it can be seen that compared with La2O3 or Gd2O3 supports, when the catalyst support is selected as Y2O3 or CeO2, the catalyst has better catalytic activity for the dehydrogenation of light alkanes to olefins.

[0044] Example 2: Preparation of x wt%B2O3-20 wt%CeO2 / γ-Al2O3 (where x = 0, 5, 10, 15, 20, 25, 33) catalysts and testing of propane oxidative dehydrogenation performance 1. Preparation of 20 wt%CeO2 / γ-Al2O3 support 1) Preparation of the precursor solution: 504.6 mg of cerium nitrate hexahydrate (Ce(NO3)3·6H2O, purity ≥99.9%) was accurately weighed and dissolved in 900 μL of deionized water, and ultrasonic treatment was carried out for 5 min until completely dissolved to obtain a cerium precursor solution.

[0045] 2) Equal-volume impregnation: 1.0 g of γ-Al2O3 support was respectively impregnated in the above solutions and left standing at room temperature for 12 h to ensure sufficient adsorption.

[0046] 3) Drying and calcination treatment: The impregnated samples were transferred to a forced-air drying oven and dried at 80 °C for 12 h. Subsequently, they were placed in a programmable-temperature muffle furnace and heated from room temperature to 550 °C at a heating rate of 5 °C / min, calcined at a constant temperature of 2 h, and then cooled with the furnace to obtain 20 wt% CeO2 / γ-Al2O3 support.

[0047] 2. Preparation of x wt% B2O3-20 wt% CeO2 / γ-Al2O3 catalyst a) Preparation of boric acid solution: 0 mg, 88.8 mg, 177.6 mg, 266.4 mg, 355.3 mg, 444.1 mg, 586.2 mg of boric acid (H3BO3) were respectively weighed and dissolved in 8 mL of deionized water at 80 °C, stirred until completely dissolved to obtain boric acid solutions with different concentrations.

[0048] b) Over-volume impregnation: 1 g of 20 wt% CeO2 / γ-Al2O3 support was added to each of the above solutions, and continuously stirred in an 80 °C water bath until the water was completely evaporated.

[0049] c) Drying and calcination: The over-impregnated samples were dried in an 80 °C forced-air drying oven for 12 h, then transferred to a muffle furnace, heated to 550 °C at a heating rate of 5 °C / min, and calcined at this temperature for 2 h, and naturally cooled to room temperature. Finally, 7 catalysts with different loadings of B2O3 were prepared: 20 wt% CeO2 / γ-Al2O3, 5 wt% B2O3-20 wt% CeO2 / γ-Al2O3, 10 wt% B2O3-20 wt% CeO2 / γ-Al2O3, 15 wt% B2O3-20 wt% CeO2 / γ-Al2O3, 20 wt% B2O3-20 wt% CeO2 / γ-Al2O3, 25 wt% B2O3-20 wt% CeO2 / γ-Al2O3, 33 wt% B2O3-20 wt% CeO2 / γ-Al2O3.

[0050] 3. Propane oxidative dehydrogenation activity test The catalytic performance was evaluated using a fixed-bed reactor (quartz tube inner diameter 6 mm). 100 mg of the catalyst was mixed with an equal mass of quartz sand (60-80 mesh) and filled in the middle of the reaction tube. The reaction gas composition was C3H8:O2:N2 (volume ratio = 1:1:4), and the total flow rate was 30 mL / min, with nitrogen as the dilution gas. The reaction mass space velocity (WHSV) was 18,000 mL / (g cat·h), the reaction temperature was controlled at 520 °C. The reaction products were monitored in real time by on-line gas chromatography (equipped with TCD and FID detectors).

[0051] According to the above catalytic reaction process, the average reaction results of 7 catalysts with different B2O3 loadings within 2 h at a catalytic reaction temperature of 520 °C are as Figure 3 shown. Figure 3 It shows the influence law of catalysts with different B2O3 loadings on the catalytic performance of propane oxidative dehydrogenation. When no B2O3 was loaded (0 wt%), the catalyst showed a significant tendency of deep oxidation (CO x selectivity > 80 wt%). With the increase of B2O3 loading, the deep oxidation activity of the catalyst was gradually inhibited. It is worth noting that when the loading reached 33 wt%, the system showed the optimal catalytic performance: the CO x selectivity was significantly reduced to below 10 wt%, while the olefin selectivity was increased to above 80 wt%. This result indicates that a B2O3 loading of 33 wt% can effectively regulate the reaction path, maximizing the yield of the target product while suppressing side reactions, so it was determined as the optimal loading condition.

[0052] Example 3: Preparation and propane oxidative dehydrogenation performance test of 33 wt%B2O3-x wt%CeO2 / γ-Al2O3, x = 5, 10, 20, 30 catalysts 1. Catalyst preparation 1) Preparation of precursor solutions: 126.2 mg, 252.3 mg, 504.6 mg and 756.9 mg of cerium nitrate hexahydrate (Ce(NO3)3·6H2O, purity ≥ 99.9%) were accurately weighed respectively, and each was dissolved in 900 μL of deionized water, and ultrasonically treated for 5 min until completely dissolved to obtain a series of cerium precursor solutions.

[0053] 2) Equal-volume impregnation: 1.0 g of γ-Al2O3 support was impregnated in the above solutions respectively, and left standing at room temperature for 12 h to ensure sufficient adsorption.

[0054] 3) Drying and calcination treatment: The impregnated samples were transferred to a forced-air drying oven and dried at 80 °C for 12 h. Then they were placed in a programmable temperature-controlled muffle furnace and heated from room temperature to 550 °C at a heating rate of 5 °C / min, and calcined at a constant temperature for 2 h and then cooled with the furnace to obtain a series of catalyst supports with different CeO2 loadings: 5 wt%CeO2 / γ-Al2O3, 10 wt%CeO2 / γ-Al2O3, 20wt%CeO2 / γ-Al2O3, 30 wt%CeO2 / γ-Al2O3.

[0055] 4) Then, dissolve 586.2 mg of boric acid (H3BO3) in 8 mL of deionized water at 80 °C, and stir until completely dissolved to obtain a boric acid solution. Add 1 g of catalyst supports with different CeO2 loadings to the above boric acid solution. The supports are 5wt%CeO2 / γ-Al2O3, 10 wt%CeO2 / γ-Al2O3, 20 wt%CeO2 / γ-Al2O3, or 30 wt%CeO2 / γ-Al2O3 supports. Continuously stir in a water bath at 80 °C until the water is completely evaporated.

[0056] 5) Finally, place the obtained samples in a hot air drying oven at 80 °C and dry for 12 h. Then transfer them to a muffle furnace, heat up to 550 °C at a heating rate of 5 °C / min, and calcine at this temperature for 2 h. Naturally cool to room temperature to finally prepare a series of catalysts with different CeO2 loadings: 33wt%B2O3-5wt%CeO2 / γ-Al2O3, 33wt%B2O3-10wt%CeO2 / γ-Al2O3, 33wt%B2O3-20wt%CeO2 / γ-Al2O3, 33 wt%B2O3-30 wt%CeO2 / γ-Al2O3.

[0057] 2. Propane oxidative dehydrogenation activity test The catalytic performance was evaluated using a fixed-bed reactor (quartz tube inner diameter 6 mm). Mix 100 mg of the catalyst with an equal mass of quartz sand (60-80 mesh) and load it in the middle of the reaction tube, then heat up to the catalytic reaction temperature. The reaction gas composition is C3H8:O2:N2 (volume ratio = 1:1:4), and the total flow rate is 30 mL / min, with nitrogen as the dilution gas. The reaction mass space velocity (WHSV) is 18,000 mL / (g cat ·h). The reaction products were monitored in real time by on-line gas chromatography (equipped with TCD and FID detectors).

[0058] According to the above catalytic reaction process, the reaction results of the catalytic temperature, propane conversion rate, and target product selectivity of the 33 wt%B2O3-5 wt%CeO2 / γ-Al2O3 catalyst at different catalytic times are shown in Figure 4A the figure. Figure 4AThe catalytic performance and stability of the 33 wt% B2O3-5 wt% CeO2 / γ-Al2O3 catalyst at different reaction temperatures are presented. At the initial stage of the catalytic reaction, as the temperature increased from 490 °C to 520 °C, the propane conversion rate increased significantly from 6.5% to 43.0%, while the olefin selectivity remained at a high level of approximately 82.0% - 91.4%. However, after the cyclic test (60 h) at 520 °C, the catalyst gradually deactivated, and the propane conversion rate decreased from 43.0% to 36.0%, indicating that the stability of the catalyst under high-temperature conditions still needs to be optimized.

[0059] According to the above catalytic reaction process, the reaction results of the catalytic temperature, propane conversion rate, and target product selectivity of the 33 wt%B2O3-10 wt%CeO2 / γ-Al2O3 catalyst at different catalytic times are shown in Figure 4B the figure. Figure 4B The catalytic performance and stability of the 33 wt% B2O3-10 wt% CeO2 / γ-Al2O3 catalyst at different reaction temperatures are presented. At the initial stage of the catalytic reaction, as the temperature increased from 490 °C to 520 °C, the propane conversion rate increased significantly from 4.0% to 43.0%, while the olefin selectivity remained at a high level of approximately 80.0% - 91.0%. However, after the cyclic test (20 h) at 520 °C, the catalyst gradually deactivated, and the propane conversion rate decreased from 43.0% to 35.0%, indicating that the stability of the catalyst under high-temperature conditions still needs to be optimized.

[0060] According to the above catalytic reaction process, the reaction results of the catalytic temperature, propane conversion rate, and target product selectivity of the 33 wt%B2O3-20 wt%CeO2 / γ-Al2O3 catalyst at different catalytic times are shown in Figure 4C the figure. Figure 4C The catalytic performance and long-term stability of the 33 wt% B2O3-20 wt% CeO2 / γ-Al2O3 catalyst at different reaction temperatures are presented. As the reaction temperature increased from 490 °C to 520 °C, the propane conversion rate increased significantly from 6.0% to 45.0%, and at the same time, the olefin selectivity remained at a high level of approximately 80.0% - 89.0%. It is worth noting that after a 200-h long-term cyclic test at 520 °C, no obvious deactivation of the catalyst occurred, and the propane conversion rate only decreased slightly from 43.0% to 39.0%, indicating that the catalyst has excellent stability under high-temperature conditions.

[0061] According to the above catalytic reaction process, the reaction results of the catalytic temperature, propane conversion rate, and target product selectivity of the 33 wt%B2O3-30 wt%CeO2 / γ-Al2O3 catalyst at different catalytic times are shown in Figure 4D the figure.Figure 4D The catalytic performance of the 33 wt% B2O3-30 wt% CeO2 / γ-Al2O3 catalyst in the temperature range of 490-530 °C is shown. At the initial stage of the catalytic reaction, in the range of 490-520 °C, the propane conversion rate increased from 4.6% to 15.6%, while the olefin selectivity remained at a high level of 83.0%-90.0%. It is worth noting that only when the temperature rose to 530 °C did the propane conversion rate increase significantly to 44.0%, indicating that the low-temperature activity of this catalyst still needs to be optimized.

[0062] In summary, the 33 wt% B2O3-20 wt% CeO2 / γ-Al2O3 catalyst is the best catalyst.

[0063] Figures 4A - 4D In, the situation where the conversion rate and selectivity are 0 means that the catalytic reaction has stopped running for a period of time.

[0064] Comparative Example 1: Preparation of 33 wt%B2O3-10 wt%MgO / γ-Al2O3 catalyst and testing of its propane oxidative dehydrogenation performance I. Preparation of 10 wt% MgO / γ-Al2O3 support a) Accurately weigh 1055.0 mg of magnesium nitrate hexahydrate (Mg(NO3)2·6H2O, purity ≥99.9%) and dissolve it in 1.0 mL of deionized water. Ultrasonically treat for 5 min until completely dissolved to obtain a magnesium precursor solution; b) Use the equal-volume impregnation method to load the above solution onto 1.0 g of γ-Al2O3 support and let it stand at room temperature for 12 h; c) Place the sample in a forced-air drying oven and dry it at 80 °C for 12 h; d) Program the temperature increase in a muffle furnace at a rate of 5 °C / min to 550 °C, keep it at a constant temperature for 2 h, and then cool it with the furnace to obtain 10 wt% MgO / γ-Al2O3 support.

[0065] II. Preparation of 33 wt%B2O3-10 wt%MgO / γ-Al2O3 support a) Weigh 586.2 mg of boric acid (H3BO3, purity ≥99.5%) and dissolve it in 8.0 mL of 80 °C ultrapure water. Stir magnetically (500 rpm) until completely dissolved; b) Add 1.0 g of the above-prepared 10 wt% MgO / γ-Al2O3 support and stir in a water bath at 80 °C (300 rpm) until the solution is completely evaporated to dryness; c) Place the sample in a forced-air drying oven and dry it at 80 °C for 12 hours; d) The temperature was programmed to rise to 550 °C at a heating rate of 5 °C / min in a muffle furnace, and after holding for 2 hours at a constant temperature, it was cooled with the furnace to finally obtain a 33 wt% B2O3-10 wt% MgO / γ-Al2O3 catalyst.

[0066] III. Propane oxidative dehydrogenation activity test The catalytic performance was evaluated using a fixed-bed reactor (quartz tube inner diameter 6 mm). 100 mg of the catalyst was mixed with an equal mass of quartz sand (60-80 mesh) and loaded in the middle of the reaction tube, and the temperature was raised to the catalytic reaction temperature. The reaction gas composition was C3H8:O2:N2 (volume ratio = 1:1:4), and the total flow rate was 30 mL / min, with nitrogen as the dilution gas. The reaction mass space velocity (WHSV) was 18,000 mL / (g cat ·h), and the reaction products were monitored in real time by an on-line gas chromatograph (equipped with TCD and FID detectors).

[0067] The catalytic reaction temperature conditions and reaction results of the 33 wt% B2O3-10 wt% MgO / γ-Al2O3 catalyst of Comparative Example 1 at different catalytic times are summarized in Figure 5 In. From Figure 5 It can be seen that for the catalyst of Comparative Example 1 at 525 °C, the propane conversion rate decreased from about 50% to about 38% after 51 hours, and deep oxidation occurred simultaneously. Then the temperature was lowered to 520 °C for the catalytic reaction test, and it was found that the propane conversion rate decreased from 46% to 40% after 28 hours. As the temperature decreased, deep oxidation was not inhibited, and the catalytic activity also decreased. Therefore, the catalytic effect of the catalyst with MgO as the intermediate layer is not good.

[0068] Comparative Example 2: Preparation of 33 wt%B2O3-10 wt%ZrO2 / γ-Al2O3 catalyst and propane oxidative dehydrogenation performance test 1. Preparation of 10 wt% ZrO2 / γ-Al2O3 support a) Accurately weigh 470.6 mg of zirconium nitrate pentahydrate (Zr(NO3)2·5H2O, purity ≥99.9%) and dissolve it in 1.0 mL of deionized water, and ultrasonically treat it for 5 minutes until completely dissolved to obtain a zirconium precursor solution; b) The above solution was loaded onto 1.0 g of γ-Al2O3 support by the equal-volume impregnation method and left to stand at room temperature for 12 h; c) The sample was placed in a forced-air drying oven and dried at 80 °C for 12 h; d) The temperature was programmed to rise to 550 °C at a heating rate of 5 °C / min in a muffle furnace, and after holding for 2 h at a constant temperature, it was cooled with the furnace to obtain a 10 wt% ZrO2 / γ-Al2O3 support.

[0069] 2. Preparation of 33 wt%B2O3-10 wt% ZrO2 / γ-Al2O3 support a) Weigh 586.2 mg of boric acid (H3BO3, purity ≥ 99.5%) and dissolve it in 8.0 mL of ultrapure water at 80 °C. Stir magnetically (500 rpm) until completely dissolved; b) Add 1.0 g of the 10 wt% ZrO2 / γ-Al2O3 support prepared above, and stir in a water bath at 80 °C (300 rpm) until the solution is completely evaporated to dryness; c) Place the sample in a forced-air drying oven and dry it at 80 °C for 12 h; d) Program the temperature to rise to 550 °C at a rate of 5 °C / min in a muffle furnace, keep it at a constant temperature for 2 h, and then cool it with the furnace. Finally, obtain the 33 wt% B2O3-10 wt% ZrO2 / γ-Al2O3 catalyst.

[0070] 3. Propane oxidative dehydrogenation activity test The catalytic performance was evaluated using a fixed-bed reactor (quartz tube inner diameter 6 mm). Take 100 mg of the catalyst and mix it with an equal mass of quartz sand (60-80 mesh), and then load it in the middle of the reaction tube. Heat it up to the catalytic reaction temperature. The reaction gas composition is C3H8:O2:N2 (volume ratio = 1:1:4), and the total flow rate is 30 mL / min, where nitrogen is used as the dilution gas. The reaction mass space velocity (WHSV) is 18,000 mL / (g cat ·h). The reaction products were monitored in real time by on-line gas chromatography (equipped with TCD and FID detectors).

[0071] The catalytic reaction temperature conditions and reaction results of the 33 wt% B2O3-10 wt% ZrO2 / γ-Al2O3 catalyst in Comparative Example 2 at different catalytic times are summarized in Figure 6 .

[0072] Comparative Example 3: Preparation of 33 wt%B2O3-10 wt%ZnO / γ-Al2O3 catalyst and propane oxidative dehydrogenation performance test 1. Preparation of 10wt%ZnO / γ-Al2O3 support a) Accurately weigh 455.0 mg of zinc nitrate hexahydrate (Zn(NO3)2·6H2O, purity ≥ 99.9%) and dissolve it in 1.0 mL of deionized water. Ultrasonically treat it for 5 minutes until completely dissolved to obtain a zinc precursor solution; b) Use the equal-volume impregnation method to load the above solution onto 1.0 g of γ-Al2O3 support and let it stand at room temperature for 12 h; c) Place the sample in a forced-air drying oven and dry it at 80 °C for 12 h; d) Heat the sample in a muffle furnace at a heating rate of 5 °C / min to 550 °C, keep it at a constant temperature for 2 h, and then cool it down with the furnace to obtain a 10 wt% ZnO / γ-Al2O3 support.

[0073] 2. Preparation of 2.33 wt%B2O3-10 wt% ZnO / γ-Al2O3 support a) Weigh 586.2 mg of boric acid (H3BO3, purity ≥99.5%) and dissolve it in 8.0 mL of ultrapure water at 80 °C. Stir magnetically (500 rpm) until it is completely dissolved. b) Add 1.0 g of the 10 wt% ZnO / γ-Al2O3 support prepared above, and stir in a water bath at 80 °C (300 rpm) until the solution is completely evaporated. c) Place the sample in a forced-air drying oven and dry it at 80 °C for 12 h. d) Heat the sample in a muffle furnace at a heating rate of 5 °C / min to 550 °C, keep it at a constant temperature for 2 h, and then cool it down with the furnace to finally obtain a 33 wt%B2O3-10wt%ZnO / γ-Al2O3 catalyst.

[0074] 3. Activity test for oxidative dehydrogenation of propane The catalytic performance was evaluated using a fixed-bed reactor (quartz tube inner diameter 6 mm). Mix 100 mg of the catalyst with an equal mass of quartz sand (60-80 mesh) and load it in the middle of the reaction tube. Heat it up to the catalytic reaction temperature. The reaction gas composition is C3H8:O2:N2 (volume ratio = 1:1:4), and the total flow rate is 30 mL / min, where nitrogen is used as the dilution gas. The reaction mass space velocity (WHSV) is 18,000 mL / (g cat ·h). The reaction products were monitored in real time by on-line gas chromatography (equipped with TCD and FID detectors), and the catalytic performance data are as Figure 7 shown.

[0075] The catalytic reaction temperature conditions and reaction results of the 33 wt%B2O3-10wt%ZnO / γ-Al2O3 catalyst in Comparative Example 3 at different catalytic times are summarized in Figure 7 as follows.

Claims

1. A highly stable boron-based catalyst based on rare earth ion bridging and anchoring, characterized in that The catalyst comprises a γ-Al2O3 carrier, a rare earth metal oxide intermediate layer sequentially loaded on the carrier, and a B2O3 active component. The rare earth metal is at least one of Gd, Ce, La, and Y. The loading amount of the rare earth metal oxide in the catalyst is 5-30%, and the loading amount of B2O3 is 5-35%.

2. The highly stable boron-based catalyst based on rare earth ion bridging and anchoring according to claim 1, characterized in that The loading amount of rare earth metal oxide in the catalyst is 15-20%, and the loading amount of B2O3 is 10-33%.

3. A highly stable boron-based catalyst based on rare earth ion bridging and anchoring as described in claim 1, characterized in that The specific surface area of the γ-Al2O3 is 50-300 m2 / g, and the average pore diameter is 15-25 nm.

4. The preparation method of a highly stable boron-based catalyst based on rare-earth ion bridging and anchoring according to claim 1, characterized in that The following steps are involved: S1: preparing an aqueous solution of a nitrate of a rare earth metal M, wherein the rare earth metal M is at least one of Gd, Ce, La, and Y, to obtain a solution A; S2: impregnating the γ-Al2O3 support in solution A of step S1, drying after sufficient impregnation, and then transferring to a muffle furnace for high-temperature calcination to obtain a support precursor modified with a rare earth metal M oxide; S3: The precursor of step S2 is immersed in a boric acid aqueous solution, dried after sufficient immersion, and then transferred to a muffle furnace for high-temperature calcination to obtain the final catalyst.

5. The preparation method of a highly stable boron-based catalyst based on rare earth ion bridging and anchoring according to claim 4, characterized in that In step S2 or S3, the calcination temperature is 400-700° C., and the calcination time is 1-4 hours.

6. The preparation method of a highly stable boron-based catalyst based on rare earth ion bridging and anchoring according to claim 5, characterized in that In step S2 or S3, the calcination temperature is 500-600° C., and the calcination time is 1-3 hours.

7. Use of a high-stability boron-based catalyst based on rare earth ion bridging anchoring as claimed in claim 1 in catalyzing the oxidative dehydrogenation reaction of light alkanes.

8. The application according to claim 7, wherein The low-carbon alkane is propane. The catalyst is loaded into a fixed-bed reactor, and the reaction gas is a C3H8-O2-N2 mixed gas with a volume ratio of 1:(0.5 - 1.5):(1 - 9). At the catalytic reaction temperature, the reaction gas is passed into the catalyst bed for the catalytic oxidative dehydrogenation reaction of propane. The catalytic reaction temperature is 450 - 550 °C, the reaction pressure is atmospheric pressure, and the reaction space velocity is 10000 - 40000 mL / (g cat ·h).

9. The application according to claim 8, characterized in that The reaction temperature is 520 - 525 °C, and the reaction space velocity is 15000 - 20000 mL / (g cat ·h).

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