Chromium-based high-entropy oxide catalyst and application thereof in preparation of propylene through propane dehydrogenation
By preparing a chromium-based high-entropy oxide catalyst with low chromium content, the problems of environmental pollution and carbon deposition deactivation of chromium-based catalysts were solved, achieving high activity and stable propane dehydrogenation effect, which is suitable for industrial applications.
Patent Information
- Application Number
- CN202411646590.5
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-11-18
- Publication Date
- 2026-05-19
AI Technical Summary
Existing industrial chromium-based catalysts have high chromium content, leading to environmental pollution and health hazards. At the same time, the catalysts are prone to carbon buildup and deactivation, requiring frequent regeneration, and Pt-based catalysts are expensive.
Chromium-based high-entropy oxide catalysts with low chromium content were prepared by adjusting the molar ratio and composition of chromium, cobalt and other metal elements, and then loading them onto supports such as molecular sieves using co-impregnation or mechanical ball milling methods to form high-entropy oxides, thereby improving catalytic activity and stability.
The reduced chromium content improves the propane dehydrogenation activity and stability of the catalyst, reduces toxicity and carbon buildup issues, and makes it suitable for industrial scale-up.
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Abstract
Description
Technical Field
[0001] This invention relates to the preparation of a chromium-based high-entropy oxide catalyst and its application in the dehydrogenation of propane to propylene, belonging to the fields of catalysis and chemical engineering. Technical Background
[0002] In recent years, the demand for propylene has grown rapidly, and propylene production capacity has continued to expand rapidly. Propylene production via propane-to-propylene (PDH) from abundant shale gas has become an important route for propylene production. Currently, Pt(Sn) / Al2O3 and Cr2O3 / Al2O3 catalysts are industrially available. Pt-based catalysts suffer from problems such as high cost, sintering, and carbon buildup. Cr-based catalysts, on the other hand, are inexpensive and have relatively high activity, attracting widespread attention. However, chromium (Cr...) 6+ The high toxicity of chromium-based catalysts remains a major concern. Furthermore, industrial chromium-based catalysts often contain high levels of chromium (up to 20% Cr₂O₃), severely polluting the environment and posing a threat to human health. Additionally, industrial chromium-based catalysts are prone to carbon buildup during PDH reactions, leading to rapid catalyst deactivation and requiring frequent regeneration. Therefore, reducing Cr content and improving catalyst activity and stability are key research directions for chromium-based catalysts.
[0003] Existing research indicates that reducing the Cr content leads to insufficient active species and a decrease in PDH activity. Therefore, designing synergistic active species to improve catalytic activity is an important method. High-entropy oxides possess unique geometric and electronic structures, high thermal stability, and other properties, showing broad application prospects in CO oxidation and electrocatalysis. Therefore, this invention provides a method for preparing a chromium-based high-entropy oxide catalyst and its application in propane dehydrogenation to propylene. By constructing suitable chromium-based high-entropy oxides and utilizing their numerous active sites, multi-element synergistic effects, and high structural stability, it is expected to stabilize active species and thus improve PDH activity. Summary of the Invention
[0004] To address the drawbacks of high chromium oxide content and high toxicity in industrial chromium-based catalysts, this invention provides the preparation of a low-chromium high-entropy oxide catalyst and its application in propane dehydrogenation to propylene. A low-chromium, highly active propane dehydrogenation catalyst is prepared by controlling the composition, content, and preparation method of the chromium-based high-entropy catalyst. The synthesis method of this invention is simple, reduces the amount of chromium used, and improves the catalytic activity and stability of the chromium-based catalyst in propane dehydrogenation.
[0005] The present invention aims to provide a chromium-based high-entropy oxide catalyst, the catalyst comprising a Cr-containing high-entropy oxide and a support, wherein the Cr-containing high-entropy oxide has the composition CrCoMO. xM is at least three of Mg, Ca, V, Ni, Zn, Zr, Cu, Mn, Ga, and Sn; the molar ratio of Cr to Co is 1:2 to 8:1; and the molar ratio of the sum of M elements to the sum of Cr and Co elements is 1:3 to 3:1. The mass percentage of Cr-containing high-entropy oxides in the catalyst is 1 to 8%, and the mass fraction of Cr in the catalyst is less than 2%.
[0006] Based on the above technical solution, preferably, the molar ratio of each element in M to any other element is 1:2 to 2:1, and more preferably, the molar ratio of each element in M is close to equimolar.
[0007] Based on the above technical solution, preferably, the molar ratio of Cr to Co is 1:2 to 3:1.
[0008] Based on the above technical solution, preferably, M is at least three of Mg, Zn, Zr, Mn, Ga, and Sn.
[0009] Based on the above technical solution, preferably, the mass percentage of Cr-containing high-entropy oxides in the catalyst is 1-5%.
[0010] Based on the above technical solution, preferably, the mass fraction of Cr in the catalyst is 0.1-1.2%, more preferably 0.1-0.6%.
[0011] Based on the above technical solution, preferably, the carrier is one or more of molecular sieves, oxides, and nitrides.
[0012] Based on the above technical solution, preferably, the molecular sieve is one or more of MFI type or dealuated Beta type molecular sieves; the MFI type is one or more of S-1 and TS-1; preferably, the molar ratio of Si to Ti in the TS-1 molecular sieve is 10 to 60:1; the oxide is one or more of Al2O3, SiO2, mesoporous MCM-41, SBA-15, TiO2, ZrO2 and CeO2; the nitride is one or more of carbon nitride, boron nitride and silicon nitride.
[0013] The present invention also aims to provide a method for preparing the above-mentioned chromium-based high-entropy oxide catalyst, wherein the method for preparing the chromium-based high-entropy oxide catalyst is a co-impregnation method or a mechanical ball milling method.
[0014] Based on the above technical solution, preferably, the co-impregnation method includes the following steps:
[0015] (1) Dissolve the Cr-containing high-entropy oxide precursor material in water or ethanol solvent and stir for 0.5 to 2 hours; then add the mixed solution dropwise to the carrier, sonicate for 0.5 to 3 hours, stir for 2 to 5 hours, let stand for 12 to 24 hours, and then dry at 60 to 150°C for 4 to 24 hours.
[0016] (2) The catalyst prepared in step (1) is calcined at 550-800℃ for 2-10 hours to obtain the target catalyst.
[0017] Based on the above technical solution, preferably, in step (1), the mass ratio of the carrier to water or ethanol solvent is 1:0.4 to 2.
[0018] Based on the above technical solution, preferably, the mechanical ball milling method includes the following steps:
[0019] (1) Place the Cr-containing high-entropy oxide precursor material and the carrier in a ball mill jar, add water or ethanol solvent, or do not add any solvent, and ball mill for 3 to 10 hours;
[0020] (2) Dry the powder after ball milling in step (1) at 60-100℃ and grind it evenly;
[0021] (3) The supported catalyst prepared in step (2) is calcined at 600-800℃ for 2-10h to obtain the target catalyst.
[0022] Based on the above technical solution, preferably, in step (1), when water or ethanol solvent is added, the mass ratio of the carrier to water or ethanol solvent is 1:0.4 to 2.
[0023] Based on the above technical solution, the preferred Cr-containing high-entropy oxide precursor material is one or more of the following: metal nitrates, chlorides, acetates, carbonates, citrates, acetylacetone salts, and oxides.
[0024] Based on the above technical solution, preferably, when the cobalt-based high-entropy oxide contains V, oxalic acid needs to be added to the cobalt-based high-entropy oxide precursor material, wherein the molar ratio of V to oxalic acid is 1:1 to 3.
[0025] Another object of the present invention is to provide the application of the above-mentioned chromium-based high-entropy catalyst in the propane dehydrogenation to propylene reaction, wherein the reaction conditions are: reaction temperature 520-650℃, reaction pressure 0.01-0.1 MPa, and propane mass hourly space velocity 0.4-50 h⁻¹. -1 Preferably, the propane concentration is 10-80%.
[0026] Beneficial effects:
[0027] Compared with existing technologies, the propane dehydrogenation to propylene catalyst obtained by the method of this invention has the advantages of low cost and low chromium content, and exhibits catalytic activity superior to that of pure chromium-based metal oxides, while also improving catalyst stability. The preparation method provided by this invention is simple, widely applicable, and easy to scale up industrially. Attached Figure Description
[0028] This invention appendix Figure 1 , of which:
[0029] Figure 1 This is a performance comparison between Comparative Examples 1, 2, and 3 and Examples 1 and 2. Detailed Implementation
[0030] The following specific embodiments will further illustrate the content of the present invention and should not be construed as limiting the present invention in any way.
[0031] Comparative Example 1
[0032] Dissolve 0.21 g of chromium nitrate hexahydrate in 3.0 mL of water and stir for 1 h; add the above mixed solution dropwise to 3.96 g of TS-1 molecular sieve (Si / Ti molar ratio 30, specific surface area 440 m²). 2 The catalyst was ultrasonicated for 0.5 h, stirred for 2 h, allowed to stand for 10 h, and then dried in a 70 °C oven for 12 h. The prepared catalyst was calcined at 600 °C for 3 h. 0.5 g of the catalyst was used in the propane dehydrogenation to propylene reaction, with 50% propane (diluted with nitrogen) as the feed gas, at a reaction temperature of 580 °C, a reaction pressure of 0.1 MPa, and a mass hourly space velocity (HHSV) of 2.4 h⁻¹. -1 The propane conversion rate was 24.2%, the propylene selectivity was 88.8%, and the propylene space-time yield was [missing information]. Performance comparison Figure 1 As shown.
[0033] Comparative Example 2
[0034] Dissolve 0.42 g of chromium nitrate hexahydrate in 5.0 mL of water and stir for 1 h; add the above mixed solution dropwise to 3.92 g of TS-1 molecular sieve (Si / Ti molar ratio 30, specific surface area 440 m²). 2 The catalyst was ultrasonicated for 0.5 h, stirred for 2 h, allowed to stand for 10 h, and then dried in a 70 °C oven for 12 h. The prepared catalyst was calcined at 600 °C for 3 h. 0.5 g of the catalyst was used in the propane dehydrogenation to propylene reaction, with 50% propane (diluted with nitrogen) as the feed gas, at a reaction temperature of 580 °C, a reaction pressure of 0.1 MPa, and a mass hourly space velocity (HHSV) of 2.4 h⁻¹. -1 The propane conversion rate was 32.1%, the propylene selectivity was 82.3%, and the propylene space-time yield was [missing information]. Performance comparison Figure 1 As shown. After 3 hours of reaction, the propane conversion rate was 23.8%, the propylene selectivity was 85.7%, and the propylene space-time yield was [missing value]. The catalyst deactivation rate was 0.146 h⁻¹. -1 .
[0035] Comparative Example 3
[0036] Dissolve 0.42 g of chromium nitrate hexahydrate in 2.0 mL of water and stir for 1 h; add the above mixed solution dropwise to 1.52 g of TS-1 molecular sieve (Si / Ti molar ratio 30, specific surface area 440 m²). 2 The catalyst was ultrasonicated for 0.5 h, stirred for 2 h, allowed to stand for 10 h, and then dried in a 70 °C oven for 12 h. The prepared catalyst was calcined at 600 °C for 3 h. 0.5 g of the catalyst was used in the propane dehydrogenation to propylene reaction, with 50% propane (diluted with nitrogen) as the feed gas, at a reaction temperature of 580 °C, a reaction pressure of 0.1 MPa, and a mass hourly space velocity (HHSV) of 2.4 h⁻¹. -1 The propane conversion rate was 28.0%, the propylene selectivity was 87.6%, and the propylene space-time yield was [missing information]. Performance comparison Figure 1 As shown.
[0037] Example 1
[0038] 0.156 g of chromium nitrate hexahydrate, 0.113 g of cobalt nitrate hexahydrate, 0.116 g of zinc nitrate hexahydrate, 0.167 g of zirconium nitrate pentahydrate, and 0.10 g of magnesium nitrate hexahydrate were dissolved in 15.0 mL of water and stirred for 1 h. Then, the above mixed solution was added dropwise to 7.6 g of TS-1 (Si / Ti molar ratio 30, specific surface area 440 m²). 2 The catalyst was ultrasonicated in a molecular sieve (g) for 0.5 h, then stirred for 2 h, allowed to stand for 10 h, and then dried in a 70 °C oven for 12 h. The prepared catalyst was calcined at 600 °C for 3 h. 0.5 g of the catalyst was used in a propane dehydrogenation to propylene reaction. The reactant gas was 50% propane (diluted with nitrogen), the reaction temperature was 580 °C, the reaction pressure was 0.1 MPa, and the mass hourly space velocity (HHSV) was 2.4 h⁻¹. -1 The propane conversion rate was 33.7%, the propylene selectivity was 92.4%, and the propylene space-time yield was [missing information]. Performance comparison Figure 1 As shown. After 3 hours of reaction, the propane conversion rate was 27.7%, the propylene selectivity was 92.0%, and the propylene space-time yield was [missing value]. The catalyst deactivation rate is 0.100 h⁻¹. -1 .
[0039] Example 2
[0040] Dissolve 0.156 g of chromium nitrate hexahydrate, 0.113 g of cobalt nitrate hexahydrate, 0.116 g of zinc nitrate hexahydrate, 0.107 g of manganese nitrate tetrahydrate, and 0.10 g of magnesium nitrate hexahydrate in 5.0 mL of water and stir for 1 h. Then, add the above mixed solution dropwise to 3.8 g of TS-1 (Si / Ti molar ratio 30, specific surface area 440 m²). 2The catalyst was ultrasonicated in a molecular sieve (g) for 0.5 h, then stirred for 2 h, allowed to stand for 16 h, and then dried in an oven at 80 °C for 12 h. The prepared catalyst was calcined at 600 °C for 3 h. 0.5 g of the catalyst was used in a propane dehydrogenation to propylene reaction. The reactant gas was 50% propane (diluted with nitrogen), the reaction temperature was 580 °C, the reaction pressure was 0.1 MPa, and the mass hourly space velocity (HHSV) was 2.4 h⁻¹. -1 The propane conversion rate was 36.1%, the propylene selectivity was 89.2%, and the propylene space-time yield was [missing information]. Performance comparison Figure 1 As shown. After 3 hours of reaction, the propane conversion rate was 31.3%, the propylene selectivity was 91.0%, and the propylene space-time yield was [missing value]. The catalyst deactivation rate was 0.076 h⁻¹. -1 .
[0041] Example 3
[0042] 0.156 g of chromium nitrate hexahydrate, 0.113 g of cobalt nitrate hexahydrate, 0.116 g of zinc nitrate hexahydrate, 0.167 g of zirconium nitrate pentahydrate, 0.05 g of copper nitrate hexahydrate, and 0.05 g of gallium nitrate hydrate were dissolved in 9 mL of ethanol and stirred for 2 h. Then, the above mixed solution was added dropwise to 5.2 g of mesoporous MCM-41 (specific surface area 830 m² / g). 2 The catalyst was ultrasonicated for 1 hour, stirred for 2 hours, allowed to stand for 10 hours, and then dried in a 70°C oven for 12 hours. The prepared catalyst was calcined at 600°C for 3 hours. 0.5 g of the catalyst was used in the propane dehydrogenation to propylene reaction. The reactant gas was 50% propane (diluted with nitrogen), the reaction temperature was 580°C, the reaction pressure was 0.1 MPa, and the mass hourly space velocity (HHSV) was 2.4 h⁻¹. -1 The propane conversion rate was 30.3%, the propylene selectivity was 92.8%, and the propylene space-time yield was [missing information].
[0043] Example 4
[0044] 0.156g chromium nitrate hexahydrate, 0.113g cobalt nitrate hexahydrate, 0.116g zinc nitrate hexahydrate, 0.167g zirconium nitrate pentahydrate, 0.08g stannous chloride dihydrate, and 5.2g S-1 molecular sieve (specific surface area 460m²) were added. 2 The powder (g) was placed in a ball mill jar, 12.0g of ethanol was added, and the mixture was ball-milled for 7 hours. The powder was then dried at 80℃ and ground until homogeneous; subsequently, it was calcined at 650℃ for 3 hours. 0.5g of the catalyst was used in a propane dehydrogenation reaction to produce propylene. The reactant gas was 50% propane (diluted with nitrogen), the reaction temperature was 580℃, the reaction pressure was 0.1MPa, and the mass hourly space velocity (HHSV) was 2.4 h⁻¹. -1 The propane conversion rate was 36.3%, the propylene selectivity was 87.5%, and the propylene space-time yield was [missing information].
[0045] Example 5
[0046] 0.156g of chromium nitrate hexahydrate, 0.113g of cobalt nitrate hexahydrate, 0.167g of zirconium nitrate pentahydrate, 0.02g of magnesium nitrate hexahydrate, 0.05g of gallium nitrate hydrate, 0.116g of zinc nitrate hexahydrate, and 5.2g of SBA-15 (specific surface area 400m²) were added. 2 The powder (g) was placed in a ball mill jar, 10.0g of water was added, and the mixture was ball milled for 5 hours. The powder was then dried at 80℃ and ground until homogeneous; subsequently, it was calcined at 650℃ for 3 hours. 0.15g of the catalyst was used in a propane dehydrogenation reaction to produce propylene. The reactant gas was 25% propane (diluted with nitrogen), the reaction temperature was 580℃, the reaction pressure was 0.1MPa, and the mass hourly space velocity (HHSV) was 7.9 h⁻¹. -1 The propylene selectivity was 86.2%, and the propylene space-time yield was [missing information].
[0047] In Comparative Examples 1-3, the Cr mass fractions were 0.7%, 1.4%, and 3.4%, respectively, and the Cr mass fractions in the examples were all less than 0.6%. From the above performance comparison, it can be seen that the PDH activity of the chromium-based high-entropy oxide catalyst designed in this invention is superior to that of the single chromium oxide catalysts in the comparative examples. Simultaneously, the deactivation rate of the high-entropy oxide catalyst is also significantly lower than that of the single chromium oxide catalysts in the comparative examples. In summary, the chromium-based high-entropy oxide catalyst designed in this invention reduces the content of toxic chromium, improves the propane dehydrogenation activity of the chromium-based oxide catalyst, and enhances the stability of the catalyst.
Claims
1. A chromium-based high-entropy oxide catalyst, characterized in that: The catalyst comprises a Cr-containing high-entropy oxide and a support, wherein the Cr-containing high-entropy oxide has the composition CrCoMO. x M is at least three of Mg, Ca, V, Ni, Zn, Zr, Cu, Mn, and Ga; the molar ratio of Cr to Co is 1:2 to 8:1; and the molar ratio of the sum of M elements to the sum of Cr and Co elements is 1:3 to 3:
1. The mass percentage of Cr-containing high-entropy oxides in the catalyst is 1 to 8%, and the mass percentage of Cr in the catalyst is less than 2%.
2. The chromium-based high-entropy oxide catalyst according to claim 1, characterized in that: The molar ratio of each element in M to any other element is 1:2 to 2:
1.
3. The chromium-based high-entropy oxide catalyst according to claim 1, characterized in that: The carrier is one or more of molecular sieves, oxides, and nitrides.
4. The chromium-based high-entropy oxide catalyst according to claim 3, characterized in that: The molecular sieve is one or more of MFI type or dealuated Beta type molecular sieves, wherein the MFI type molecular sieve is one or more of S-1 and TS-1; the oxide is one or more of Al2O3, SiO2, mesoporous MCM-41, SBA-15, TiO2, ZrO2 and CeO2; and the nitride is one or more of carbon nitride, boron nitride and silicon nitride.
5. The method for preparing the chromium-based high-entropy oxide catalyst according to any one of claims 1-4, characterized in that: The chromium-based high-entropy oxide catalyst is prepared by co-impregnation or mechanical ball milling.
6. The preparation method according to claim 5, characterized in that: The co-impregnation method includes the following steps: (1) Dissolve the Cr-containing high-entropy oxide precursor material in water or ethanol solvent and stir for 0.5 to 2 hours; then add the resulting mixed solution dropwise to the carrier, sonicate for 0.5 to 3 hours, stir for 2 to 5 hours, let stand for 12 to 24 hours, and then dry at 60 to 150°C for 4 to 24 hours. (2) The catalyst prepared in step (1) is calcined at 550-800℃ for 2-10 hours to obtain the target catalyst.
7. The preparation method according to claim 5, characterized in that: The mechanical ball milling method includes the following steps: (1) Place the Cr-containing high-entropy oxide precursor material and the carrier in a ball mill jar, add water or ethanol solvent, or do not add any solvent, and ball mill for 3 to 10 hours; (2) Dry the powder after ball milling in step (1) at 60-100℃ and grind it evenly; (3) The supported catalyst prepared in step (2) is calcined at 600-800℃ for 2-10h to obtain the target catalyst.
8. The preparation method according to claim 6 or 7, characterized in that: The precursor materials of Cr-containing high-entropy oxides are one or more of the following: metal nitrates, chlorides, acetates, carbonates, citrates, acetylacetone salts, oxalates, and oxides. In step (1) of the co-impregnation method, the mass ratio of the carrier to water or ethanol solvent is 1:0.4-2; In step (1) of the mechanical ball milling method, when water or ethanol solvent is added, the mass ratio of the carrier to water or ethanol solvent is 1:0.4 to 2.
9. The application of the chromium-based high-entropy oxide catalyst according to any one of claims 1-4 in the propane dehydrogenation to propylene reaction.
10. The application according to claim 9, characterized in that: The reaction conditions were: reaction temperature 520–650℃, reaction pressure 0.01–0.1 MPa, and propane mass hourly space velocity (HHSV) 0.4–50 h⁻¹. -1 .