A non-noble metal dehydrogenation catalyst for n-octane dehydrogenation and a preparation method thereof

Abstract

The application discloses a non-noble metal dehydrogenation catalyst for n-octane dehydrogenation and a preparation method thereof, and belongs to the field of catalysis technology.The catalyst is a composite oxide catalyst, and comprises a first metal, a second metal, a third metal and an additive; the first metal is selected from at least one of Fe, Ni, Zn, Mg, Mn, Ti and Cu, the second metal is selected from at least one of Ce, Zr, La, Mo and W, the third metal is selected from at least one of Al, In, Ti, La and Mg, and the additive is selected from at least one of Li, Na, K, Ca and Mg; the molar content of the first metal is 20% to 80%, the molar content of the second metal is 10% to 60%, the molar content of the third metal is 20% to 80%, and the molar content of the additive is 1% to 10%, based on the total molar amount of metal elements.The catalyst has good activity and stability in the n-octane dehydrogenation reaction through the synergistic effect of multiple components, the total selectivity of C8 dehydrogenation products can reach 84.98% to 90.29%, the preparation process is simple and controllable, the cost is low, and the catalyst is suitable for industrial production.

Description

Technical Field

[0001] This invention belongs to the field of catalysis technology, specifically relating to a non-precious metal dehydrogenation catalyst for the dehydrogenation of n-octane and its preparation method. This invention also relates to the application of this catalyst in the dehydrogenation of n-octane to prepare C8 olefins and C8 aromatics. Background Technology

[0002] The dehydrogenation of long-chain n-alkanes to produce long-chain monoolefins is an important reaction process in the petrochemical and coal chemical industries. This reaction has a long history of research and application in the petrochemical industry. As early as the early 1960s, UOP in the United States developed a catalytic system suitable for the dehydrogenation of long-chain alkanes to obtain long-chain monoolefins, a key intermediate required for the synthesis of straight-chain alkylbenzenes. In the 1980s and 1990s, to break through foreign technological blockades in this field, my country successively developed long-chain alkane dehydrogenation catalysts with superior performance and fully realized the domestic production of such catalysts.

[0003] n-Octane (C8), a key representative of long-chain n-alkanes, produces C8 olefins and C8 aromatics through dehydrogenation. C8 aromatics (such as xylene and ethylbenzene) are important basic chemical raw materials, widely used in the production of synthetic resins, synthetic rubber, and synthetic fibers. They are also used in the preparation of fine chemicals such as dyes, pharmaceuticals, and pesticides, and can serve as a component of high-octane gasoline, effectively improving its anti-knock properties. Furthermore, styrene, as a crucial organic chemical monomer, is used in the production of polystyrene and its copolymers (approximately 80%), playing a key role in the synthetic resin and synthetic rubber industries. Therefore, the dehydrogenation of n-octane to produce C8 olefins and C8 aromatics represents a catalytic conversion process with significant industrial application value.

[0004] In the dehydrogenation technology of long-chain n-alkanes, platinum-based noble metal catalysts are widely used. For example, the DEH series catalysts from UOP in the United States, and the NDC and DF series catalysts from China, all use Pt as the main active component. Based on this, researchers have developed Pt-Sn bimetallic catalysts or multimetallic catalysts modified with other components, with Al2O3, SiO2, and other porous materials as supports. Patent CN104248982A reports a long-chain alkane dehydrogenation catalyst with La-modified Al2O3 as the support; by impregnating active components such as Pt, Sn, and K, its reaction activity and stability are significantly better than those of the unmodified La catalyst. Patent CN112934230A discloses a low-Pt long-chain alkane dehydrogenation catalyst using Pt-Ni-Fe as the composite active component and alkali metals as promoters, which can effectively reduce the Pt loading. Patent CN119909702A discloses a high-density long-chain alkane dehydrogenation catalyst, which uses mesoporous and microporous Al2O3 as a support to support a composition of Pt, Sn, Ni, Fe, and alkali metals or their oxides. Patent CN120961206A provides a Pt-Sn bimetallic catalyst, which precisely loads Sn and Pt using atomic layer deposition technology, thereby significantly improving the catalytic activity and aromatic selectivity of alkane aromatization.

[0005] However, catalysts with precious metal Pt as the main active component have the following drawbacks: First, platinum is expensive, resulting in high catalyst costs; second, under the high-temperature reaction conditions of direct dehydrogenation of long-chain alkanes, platinum-based catalysts are prone to side reactions such as carbon deposition and cracking, requiring the introduction of large amounts of hydrogen during the reaction to suppress deep dehydrogenation and carbon deposition, thus increasing operating costs; third, platinum-based catalysts are prone to sintering and poisoning, and the regeneration process often uses chlorination oxidation, which places high demands on the materials of the equipment.

[0006] To overcome the aforementioned shortcomings of noble metal catalysts, researchers have begun exploring non-noble metal catalytic systems in recent years. Patent CN121819832A discloses a non-noble metal long-chain alkane dehydrogenation catalyst with CeO2 and transition metals M (Fe, Co, Ni) as the main active components. However, its active site type is limited, making it difficult to simultaneously achieve the dual functions of CH bond activation and C / C bond retention in the n-octane dehydrogenation reaction, resulting in insufficient selectivity for the target product. Patent CN117654527A discloses a catalyst for the dehydrogenation of C6-C8 straight-chain alkanes to aromatics, with CrO2 as the active component. x VO x MoO x or WO x Of these, Cr is toxic, V and Mo are easily reduced under reaction conditions leading to decreased activity, and there are no reports of this catalyst being used to simultaneously produce olefins and aromatics with high selectivity.

[0007] Therefore, there is an urgent need to develop a non-precious metal dehydrogenation catalyst for n-octane dehydrogenation. This catalyst should have good catalytic activity, excellent selectivity for C8 olefins and C8 aromatics, and a stable service life. At the same time, the preparation process should be simple and inexpensive, making it suitable for industrial production applications. Summary of the Invention

[0008] To address the shortcomings of existing platinum-based catalysts for n-octane dehydrogenation, such as high cost, sintering, and carbon deposition, and the insufficient catalytic activity and target product selectivity of existing non-precious metal catalysts in the n-octane dehydrogenation reaction, this invention provides a non-precious metal dehydrogenation catalyst for n-octane dehydrogenation. This catalyst exhibits good stability and environmental friendliness, and its preparation method is simple, economical, has a short process, and is easily scaled up for production.

[0009] To achieve the above objectives, the present invention adopts the following technical solution: A non-precious metal dehydrogenation catalyst for the dehydrogenation of n-octane, wherein the catalyst is a composite oxide catalyst comprising a first metal, a second metal, a third metal, and an additive; The first metal is selected from at least one of iron (Fe), nickel (Ni), zinc (Zn), magnesium (Mg), manganese (Mn), titanium (Ti), and copper (Cu); The second metal is selected from at least one of cerium (Ce), zirconium (Zr), lanthanum (La), molybdenum (Mo), and tungsten (W); The third metal is selected from at least one of aluminum (Al), indium (In), titanium (Ti), lanthanum (La), and magnesium (Mg); The additive is selected from at least one of lithium (Li), sodium (Na), potassium (K), calcium (Ca) and magnesium (Mg).

[0010] Based on the total molar amount of metal elements in the composite oxide catalyst, the molar content of the first metal is 20%~80%; the molar content of the second metal is 5%~60%; the molar content of the third metal is 20%~80%; and the molar content of the additive is 1%~10%.

[0011] Preferably, the first metal is selected from at least one of manganese, zinc and copper; the second metal is selected from at least one of cerium, zirconium and lanthanum; and the third metal is selected from at least one of aluminum and titanium.

[0012] Preferably, the first metal is manganese, the second metal is cerium, and the third metal is aluminum.

[0013] Preferably, the first metal is copper, the second metal is zirconium, and the third metal is titanium.

[0014] Preferably, the first metal is zinc, the second metal is zirconium, and the third metal is aluminum.

[0015] Preferably, the first metal is manganese, the second metal is zirconium, and the third metal is aluminum.

[0016] Preferably, the first metal is zinc, the second metal is magnesium, and the third metal is aluminum.

[0017] This invention constructs a multi-component composite oxide, utilizing the differences in valence state, coordination number, and ionic radius of different metal elements to induce lattice distortion and form a specific crystal structure, thereby generating a large number of defect sites on the material surface, including lattice defects, structural distortions, and oxygen vacancies. These surface defect sites can simultaneously provide protons (Brønsted acid sites) and accept electron pairs (Lewis acid sites) in the catalytic reaction, constituting active centers on the composite oxide surface. Studies have shown that the properties of these surface defect sites are closely related to dehydrogenation activity. Based on this, this invention can effectively control the type and density of surface defect sites by adjusting the types and ratios of metal elements in the composite oxide, thereby achieving systematic optimization of dehydrogenation performance.

[0018] Accordingly, the present invention also provides a method for preparing the above-mentioned non-noble metal dehydrogenation catalyst for n-octane dehydrogenation, employing a co-precipitation method, a sol-gel method, or an impregnation method to ensure uniform distribution of the active components on the surface of the composite oxide catalyst. The method includes the following steps: (1) Dissolution of metal salts: Dissolve the first metal, the second metal, the third metal and the metal salts corresponding to the additives in a solvent to obtain a mixed metal solution; (2) Preparation of catalyst: The metal mixed solution in step (1) is prepared into a catalyst precursor by co-precipitation, sol-gel or impregnation method; (3) Drying and calcination: The catalyst precursor obtained in step (2) is dried at 80℃~150℃ for 6~48 hours, and then calcined at 300℃~600℃ for 2~12 hours to obtain the catalyst.

[0019] Preferably, the metal salt in step (1) is a nitrate or chloride of the corresponding metal.

[0020] Preferably, the solvent in step (1) is selected from a single solvent or a mixture of solvents such as methanol, ethanol, acetone, water, nitric acid and hydrochloric acid.

[0021] Preferably, the precipitant used in the co-precipitation method in step (2) is selected from one or more of ammonia, hydroxide solution and carbonate.

[0022] Preferably, the reagents used in the sol-gel method in step (2) are selected from one or more of organic acids, polymers and chelating agents.

[0023] This invention also provides the application of the above-mentioned non-precious metal catalyst in the dehydrogenation reaction of n-octane. The dehydrogenation reaction is carried out in a fixed-bed reactor under the following conditions: atmospheric pressure, reaction temperature 420–550 °C, and n-octane liquid hourly space velocity (LHSV) of 2–20 h⁻¹. -1 The molar ratio of dilution gas to n-octane is 2-20:1, and the dilution gas is selected from one or more of hydrogen, nitrogen, and carbon dioxide. Before the reaction, if the catalyst requires reduction, reduction is carried out in a fixed bed at a temperature of 420-500℃ for 1-3 hours. The tail gas and condensed liquid products after the reaction are quantified by gas chromatography.

[0024] Compared with the prior art, the present invention has the following beneficial effects: 1. This invention provides a non-precious metal composite oxide catalyst. By designing a quaternary synergistic catalytic system of a first metal, a second metal, a third metal, and an additive, it replaces the traditional platinum-based precious metal catalyst, constructing a novel catalytic system that combines lower cost, excellent catalytic activity, and good operational stability. Compared with existing non-precious metal catalysts (such as the CeO2-M two-component system disclosed in CN121819832A), this invention, by introducing a third metal and an alkali metal / alkaline earth metal additive, forms a richer multi-component synergistic effect, significantly improving the catalyst's dehydrogenation activity and product selectivity.

[0025] 2. The catalyst of this invention is particularly suitable for the dehydrogenation reaction of n-octane, and can convert n-octane into target products such as C8 olefins and C8 aromatics with high selectivity. Example data shows that the catalyst of this invention achieves a total selectivity of 84.98%~90.29% for the C8 dehydrogenation products (C8 olefins + C8 aromatics) in the n-octane dehydrogenation reaction, realizing the efficient and directional conversion of n-octane.

[0026] 3. The catalyst of this invention is prepared by conventional co-precipitation method, sol-gel method or impregnation method. The process is simple and controllable, and there is no need to use expensive surfactants or complex hydrothermal reflux equipment. The preparation conditions are mild, the energy consumption is low, and it is easy to realize industrial scale-up production.

[0027] 4. This invention effectively solves the technical problem of lacking dedicated high-efficiency non-precious metal catalysts in the field of n-octane dehydrogenation. It has the advantages of reliable catalytic performance and strong process adaptability, and is suitable for industrial application. Attached Figure Description

[0028] Figure 1Transmission electron microscopy (TEM) image and element-mapping diagram of the catalyst prepared in Example 3. Figure 2 The ammonia-programmed temperature desorption (NH3-TPD) curves of Examples 1, 3, 4 and Comparative Example 1 are compared. Detailed Implementation

[0029] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to specific embodiments. It should be understood that the embodiments described herein are for illustrative purposes only and are not intended to limit the invention. All other embodiments obtained by those skilled in the art based on the disclosure of this invention without inventive effort are within the scope of protection of this invention.

[0030] The performance evaluation of the catalysts of this invention follows the following general principles, unless otherwise specified: Catalyst evaluation method: The evaluation was conducted in a micro fixed-bed reactor. The catalyst loading was 0.25 mL, and the reaction conditions were: atmospheric pressure, temperature 480 °C, and liquid hourly space velocity (LHSV) of n-octane 4 h⁻¹. -1 The dilution gas (one or more of hydrogen, nitrogen, and carbon dioxide) was used in a molar ratio of 10:1 to n-octane. Before the reaction, the catalyst was reduced with hydrogen at 480°C for 2 hours in a fixed-bed reactor. The liquid products after the reaction were analyzed by gas chromatography, and the conversion of n-octane and the selectivity of each product were calculated using the normalization method.

[0031] The calculation methods for n-octane conversion and the selectivity of each product are as follows: n-Octane conversion rate (%) = (moles of n-octane consumed in the reaction / moles of n-octane in the feed) × 100%; C8 olefin selectivity (%) = (moles of C8 olefins generated / moles of n-octane consumed in the reaction) × 100%; C8 aromatic selectivity (%) = (moles of C8 aromatics produced / moles of n-octane consumed in the reaction) × 100%; Total C8 dehydrogenation product selectivity (%) = C8 olefin selectivity + C8 aromatic selectivity; Crack product selectivity (%) = (moles of C1~C7 crack products generated / moles of n-octane consumed in the reaction) × 100%.

[0032] Example 1 This embodiment uses MnCeAlO x The composite oxide catalyst was prepared by ammonia co-precipitation.

[0033] (1) Weigh 8.94 g of 50% manganese nitrate solution (equivalent to 2.50 g of Mn), 8.44 g of aluminum nitrate (equivalent to 0.60 g of Al), and 1.09 g of cerium nitrate (equivalent to 0.35 g of Ce), dissolve them in an appropriate amount of deionized water, sonicate for 20 minutes until completely dissolved, and continue stirring for 30 minutes to obtain a mixed metal solution.

[0034] (2) Add an appropriate amount of 15% ammonia water to the solution obtained in step (1) and adjust the pH value to 8 to 8.5 to ensure that all components are completely precipitated.

[0035] (3) Filter the precipitate obtained in step (2), wash it three times each with deionized water and ethanol, and then dry it at 120°C. Then weigh 0.064 g of potassium chloride (equivalent to 0.034 g of K) and dissolve it in an appropriate amount of water. Immerse an equal volume of the potassium chloride solution on the dried solid.

[0036] (4) The solid obtained in step (3) is dried at 120°C overnight, heated to 550°C at 5°C / min, calcined for 6 hours, and then naturally cooled to obtain the composite oxide catalyst.

[0037] (5) The final molar amounts of manganese, cerium and aluminum account for 50%, 5% and 45% of the total molar amounts of the metal, respectively.

[0038] Example 2 This embodiment uses CuZrTiO x The composite oxide catalyst was prepared by potassium carbonate co-precipitation.

[0039] (1) Weigh 6.04 g of copper nitrate (equivalent to 1.59 g of Cu), 1.07 g of zirconium nitrate (equivalent to 0.31 g of Zr), and 17.3 g of titanium trichloride solution (15~20%) (equivalent to 1.35 g of Ti), dissolve them in an appropriate amount of deionized water, sonicate for 20 minutes until completely dissolved, and continue stirring for 30 minutes to obtain a metal mixed solution.

[0040] (2) Add an appropriate amount of 5% potassium carbonate solution to the solution obtained in step (1) and adjust the pH value to approximately 7 to ensure that all components are completely precipitated.

[0041] (3) The precipitate obtained in step (2) is thoroughly washed with deionized water and ethanol, and the filtrate is dried at 120°C overnight until no chloride ions are detected by silver nitrate solution.

[0042] (4) The precipitate obtained in step (3) is heated to 550°C at 5°C / min and calcined for 6 hours. After natural cooling, CuZrTiO is obtained. x Composite oxide catalyst.

[0043] (5) The final molar amounts of copper, zirconium and titanium account for 50%, 5% and 45% of the total molar amount of metal, respectively.

[0044] Example 3 This embodiment uses ZnZrAlO x The composite oxide catalyst was prepared using the citric acid sol-gel method.

[0045] (1) Weigh 6.24 g of zinc nitrate (equivalent to 1.48 g of Zn), 5.37 g of zirconium nitrate (equivalent to 1.55 g of Zr), 4.69 g of aluminum nitrate (equivalent to 0.33 g of Al), and 18 g of citric acid, dissolve them in an appropriate amount of deionized water, sonicate for 20 minutes until completely dissolved, and continue stirring for 30 minutes to obtain a metal mixed solution.

[0046] (2) Transfer the solution obtained in step (1) into a rotary evaporator and evaporate it at 60°C under reduced pressure until it becomes a viscous gel.

[0047] (3) The gel obtained in step (2) was dried at 120°C for 6 hours, then transferred to a muffle furnace and heated to 550°C at 5°C / min for 6 hours. After natural cooling, ZnZrAlO was obtained. x Composite oxide catalyst.

[0048] (5) The final molar amounts of zinc, zirconium and aluminum account for 46%, 27% and 27% of the total molar amounts of the metal, respectively.

[0049] Based on the transmission electron microscopy (TEM) images and elemental mapping results of the catalyst ( Figure 1 As can be seen, the components are uniformly distributed on the catalyst surface, indicating the formation of a composite oxide, and no obvious single oxide phase was observed.

[0050] Example 4 This embodiment uses MnZrAlO x The composite oxide catalyst was prepared by potassium carbonate co-precipitation.

[0051] (1) Weigh 8.94 g of 50% manganese nitrate solution (equivalent to 2.50 g of Mn), 3.15 g of zirconium nitrate (equivalent to 0.91 g of Zr), and 7.50 g of aluminum nitrate (equivalent to 0.53 g of Al), dissolve them in an appropriate amount of deionized water, sonicate for 20 minutes until completely dissolved, and continue stirring for 30 minutes to obtain a mixed metal solution.

[0052] (2) Add an appropriate amount of 5% potassium carbonate solution to the solution obtained in step (1) and adjust the pH value to approximately 8 to ensure that all components are completely precipitated.

[0053] (3) The precipitate obtained in step (2) is thoroughly washed with deionized water and ethanol and dried overnight at 120°C.

[0054] (4) The precipitate obtained in step (3) is placed in a muffle furnace and heated to 550°C at a rate of 5°C / min. It is then calcined for 6 hours and naturally cooled to obtain MnZrAlO. x Composite oxide catalyst.

[0055] (5) The final molar amounts of manganese, zirconium and aluminum account for 48%, 14% and 38% of the total molar amounts of the metal, respectively.

[0056] Example 5 This embodiment uses ZnMgAlO x The composite oxide catalyst was prepared by ammonia co-precipitation.

[0057] (1) Weigh 2.48 g of zinc nitrate (equivalent to 0.59 g of Zn), 2.14 g of magnesium nitrate (equivalent to 0.20 g of Mg), and 3.13 g of aluminum nitrate (equivalent to 0.22 g of Al), dissolve them in an appropriate amount of deionized water, sonicate for 20 minutes until completely dissolved, and continue stirring for 30 minutes to obtain a metal mixed solution.

[0058] (2) Add an appropriate amount of 15% ammonia water to the solution obtained in step (1) to adjust the pH value to be greater than 8, so as to ensure that all components are completely precipitated.

[0059] (3) Filter the precipitate obtained in step (2), wash it three times each with deionized water and ethanol, and then dry it at 120°C. Then weigh 0.058 g of sodium chloride (equivalent to 0.023 g of Na) and dissolve it in an appropriate amount of water. Immerse an equal volume of the sodium chloride solution on the dried solid.

[0060] (4) The solid obtained in step (3) is dried at 120°C overnight, heated to 550°C at 5°C / min, calcined for 6 hours, and then naturally cooled to obtain ZnMgAlO. x Composite oxide catalyst.

[0061] (5) The final molar amounts of zinc, magnesium and aluminum account for 33%, 33% and 34% of the total molar amounts of the metal, respectively.

[0062] Comparative Example 1 This comparative example is ZnAlO x The composite oxide catalyst was prepared by ammonia co-precipitation.

[0063] (1) Weigh 7.44g of zinc nitrate and 9.38g of aluminum nitrate, dissolve them in an appropriate amount of deionized water, sonicate for 20 minutes until completely dissolved, and continue stirring for 30 minutes.

[0064] (2) Add an appropriate amount of 15% ammonia water to the solution obtained in step (1) and adjust the pH value to between 8 and 8.5 to ensure that all components are completely precipitated.

[0065] (3) The material obtained in step (2) is dried at 120°C for 6 hours, then transferred to a muffle furnace and heated to 550°C at 5°C / min for 6 hours. After natural cooling, the catalyst is obtained.

[0066] (4) The final molar amounts of zinc and aluminum account for 50% and 50% of the total molar amounts of the metal, respectively.

[0067] The results of comparing the ammonia-temperature programmed desorption (NH3-TPD) curves of Examples 1, 3, and 4 with those of Comparative Example 1 are as follows: Figure 2 As shown in the figure, the NH3-TPD curves of the catalysts in each embodiment all show two desorption peaks, located in the low-temperature region (approximately 150°C) and the high-temperature region (approximately 600°C), respectively, corresponding to the weak acid centers and strong acid centers on the catalyst surface; while Comparative Example 1 only has one desorption peak in the low-temperature region, indicating that it only has weak acid centers. Further comparison of the integral area of ​​the low-temperature desorption peak (i.e., the amount of weak acid) shows that the order is: Example 3 > Example 4 > Example 1, and the peak intensity of each embodiment is much greater than that of Comparative Example 1, indicating that the amount of weak acid in the catalysts of the embodiments is significantly higher than that of the comparative example, and in the embodiments, the amount of weak acid decreases in the order of Examples 3, 4, and 1. In addition, the low-temperature desorption peak of Example 3 is slightly biased towards the high-temperature direction, indicating that the weak acid strength of this catalyst is also enhanced.

[0068] Comparative Example 2 This comparative example is MgAlO x The composite oxide catalyst was prepared by the citric acid sol-gel method.

[0069] (1) Weigh 3.21g magnesium nitrate, 4.69g aluminum nitrate and 7.5g citric acid and dissolve them in an appropriate amount of deionized water. Sonicate for 20 minutes until completely dissolved and continue stirring for 30 minutes.

[0070] (2) The solution obtained in step (1) is transferred into a rotary evaporator and evaporated at 60°C under reduced pressure until it becomes viscous.

[0071] (3) The substance obtained in step (2) was dried at 120°C overnight, then transferred to a muffle furnace and heated to 650°C at 5°C / min for 8 hours. After natural cooling, the catalyst was obtained.

[0072] (4) The final molar amounts of magnesium and aluminum account for 50% and 50% of the total molar amounts of the metal, respectively.

[0073] Comparative Example 3 This comparative example is MnAlO x The composite oxide catalyst was prepared by ammonia co-precipitation.

[0074] (1) Weigh 8.94g of 50% manganese nitrate solution and 9.38g of aluminum nitrate, dissolve them in an appropriate amount of deionized water, sonicate for 20 minutes until completely dissolved, and continue stirring for 30 minutes.

[0075] (2) Add an appropriate amount of 5% potassium carbonate solution to the solution obtained in step (1) to adjust the pH value to approximately 8, ensuring that all components are completely precipitated. (3) The material obtained in step (2) is dried at 120°C for 6 hours, then transferred to a muffle furnace and heated to 550°C at 5°C / min for 6 hours. After natural cooling, the catalyst is obtained.

[0076] (4) The final molar amounts of manganese and aluminum account for 50% and 50% of the total molar amounts of the metal, respectively.

[0077] The catalysts prepared in Examples 1-5 and Comparative Examples 1-3 were evaluated for their performance in the n-octane dehydrogenation reaction according to the aforementioned evaluation method. The resulting catalytic performance data are summarized in Table 1.

[0078] Table 1. Reaction performance of n-octane dehydrogenation catalyst The results in Table 1 show that: The non-precious metal composite oxide catalysts prepared in Examples 1-5 of this invention all exhibited good catalytic performance in the dehydrogenation reaction of n-octane. The n-octane conversion rate was 4.37%~6.74%, the total selectivity of C8 dehydrogenation products (C8 olefins + C8 aromatics) was 84.98%~90.29%, and the selectivity of cracking products was only 9.72%~15.01%. Among them, Example 3 showed the highest total selectivity of C8 dehydrogenation products, reaching 90.29%; Example 4 showed the highest selectivity of C8 aromatics, reaching 70.71%, indicating that the catalyst has excellent aromatization performance.

[0079] In contrast, the catalysts prepared in Comparative Examples 1-3, containing only two metal components, exhibited octane conversion rates of only 0.94%–1.01%, total selectivity for C8 dehydrogenation products of only 33.26%–40.26%, and a high selectivity for cracking products of 59.74%–66.74%. This demonstrates that the quaternary synergistic catalytic system constructed by introducing a second metal, a third metal, and an additive significantly enhances the octane dehydrogenation activity and target product selectivity of the catalyst, while effectively suppressing the occurrence of cracking side reactions.

[0080] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A non-precious metal dehydrogenation catalyst for the dehydrogenation of n-octane, characterized in that, The catalyst is a composite oxide catalyst, comprising a first metal, a second metal, a third metal, and an additive; The first metal is selected from at least one of iron, nickel, zinc, magnesium, manganese, titanium, and copper; The second metal is selected from at least one of cerium, zirconium, lanthanum, molybdenum, and tungsten; The third metal is selected from at least one of aluminum, indium, titanium, lanthanum, and magnesium; The additive is selected from at least one of lithium, sodium, potassium, calcium and magnesium; Based on the total molar amount of metal elements in the composite oxide catalyst, the molar content of the first metal is 20%~80%, the molar content of the second metal is 5%~60%, the molar content of the third metal is 20%~80%, and the molar content of the additive is 1%~10%.

2. The catalyst according to claim 1, characterized in that, The first metal is selected from at least one of manganese, zinc and copper; the second metal is selected from at least one of cerium, zirconium and lanthanum; and the third metal is selected from at least one of aluminum and titanium.

3. The catalyst according to claim 1, characterized in that, The first metal is manganese, the second metal is cerium, and the third metal is aluminum.

4. The catalyst according to claim 1, characterized in that, The first metal is copper, the second metal is zirconium, and the third metal is titanium.

5. The catalyst according to claim 1, characterized in that, The first metal is zinc, the second metal is zirconium, and the third metal is aluminum.

6. The catalyst according to claim 1, characterized in that, The first metal is manganese, the second metal is zirconium, and the third metal is aluminum.

7. The catalyst according to claim 1, characterized in that, The first metal is zinc, the second metal is magnesium, and the third metal is aluminum.

8. A method for preparing a non-noble metal dehydrogenation catalyst for n-octane dehydrogenation as described in any one of claims 1-7, characterized in that, Includes the following steps: (1) Dissolve the first metal, the second metal, the third metal and the metal salt corresponding to the additive in a solvent to obtain a metal mixed solution; (2) The metal mixed solution from step (1) is prepared into a catalyst precursor by means of co-precipitation, sol-gel method or impregnation method; (3) The catalyst precursor obtained in step (2) is dried at 80℃~150℃ for 6~48 hours and then calcined at 300℃~600℃ for 2~12 hours to obtain the catalyst.

9. The preparation method according to claim 8, characterized in that, The metal salt mentioned in step (1) is a nitrate or chloride of the corresponding metal; the solvent is selected from a single solvent or a mixture of solvents such as methanol, ethanol, acetone, water, nitric acid and hydrochloric acid; the precipitant used in the co-precipitation method in step (2) is selected from one or more of ammonia, hydroxide solution and carbonate; the reagent used in the sol-gel method is selected from one or more of organic acid, polymer and chelating agent.

10. The application of a non-noble metal dehydrogenation catalyst as described in any one of claims 1-7 in the dehydrogenation reaction of n-octane, characterized in that, The dehydrogenation reaction is carried out in a fixed-bed reactor under the following conditions: atmospheric pressure, reaction temperature 420-550℃, and n-octane liquid hourly space velocity 2-20 h⁻¹. -1 The molar ratio of dilution gas to n-octane is 2 to 20:1, and the dilution gas is selected from one or more of hydrogen, nitrogen and carbon dioxide.

Images