A na-modified cobalt-iron solid solution catalyst, its preparation and use in the synthesis of higher alcohols and higher alkenes from synthesis gas

Abstract

This invention discloses a method for preparing a highly efficient Na-modified solid solution catalyst and its application in the synthesis of higher alcohols and co-production of higher olefins from syngas. The catalyst comprises a solid solution component and an auxiliary component, wherein the solid solution component is a cobalt-iron solid solution, and the auxiliary component is elemental sodium or an oxide. The reactive centers are the cobalt-iron solid solution, cobalt and cobalt carbide or cobalt oxide species, and elemental sodium or an oxide. This invention provides a novel method for preparing a Na-modified cobalt-iron solid solution catalyst and its application, which exhibits high activity and high C content. 6+ alcohols and C 5+ The reaction exhibits olefin selectivity and stability, with operating temperatures ranging from 200 to 350°C and reaction pressures between 0.5 MPa and 10 MPa. The catalyst structure is stable during the reaction, the preparation method is simple and easily reproducible, facilitating industrial application.

Description

Technical Field

[0001] This invention relates to a method for preparing a highly efficient Na-modified solid solution catalyst and its application in syngas reforming, specifically for the highly selective preparation of higher alcohols and co-production of higher olefins from syngas. Particularly, it relates to a Na-CoFeO catalyst. X Preparation methods and applications of catalysts. Background Technology

[0002] Higher alcohols typically refer to alcohols containing six or more carbon atoms. They are important components in the chemical, pharmaceutical, and energy sectors and have significant economic value. The traditional route for producing higher alcohols from petroleum is a complex chemical process, primarily involving the cracking of petroleum into low-carbon olefins, followed by polymerization into long-chain olefins, hydroformylation of the long-chain olefins into aldehydes, and further hydrogenation to alcohols. Compared to traditional synthetic routes, the one-step synthesis of higher alcohols via syngas conversion is a more efficient, relatively simple, and environmentally friendly process. Long-chain olefins typically refer to linear α-olefins with five or more carbon atoms. They are important organic raw materials used as comonomers for various types of polyethylene and in the synthesis of high-quality lubricants and plasticizers. The main production method for long-chain α-olefins is the ethylene oligomerization reaction via the petroleum route. With the continuous depletion of petroleum resources, non-petroleum routes for olefin production have attracted considerable attention. This route mainly utilizes carbon-containing resources such as coal, natural gas, and biomass to produce syngas, which is then used to directly or indirectly produce olefins. However, this reaction process is complex. CO and H2 are difficult to activate and crack during the reaction, resulting in generally low catalyst activity. Furthermore, the reaction produces a series of byproducts such as methane, carbon dioxide, and alkanes, leading to low selectivity for higher alcohols and olefins. Therefore, designing catalysts to regulate the reaction network and achieve synergistic effects among different active sites to preferentially convert syngas into higher alcohols and olefins remains challenging.

[0003] Currently applied patents have investigated various types of catalysts for the synthesis of higher alcohols. Patent CN102500374B reports a copper-based multimetal nanocatalyst prepared by self-reduction, distributed reduction, and simultaneous reduction methods, which improves the C... 2+ And C 6+ The selectivity of alcohols is low. However, the CO conversion rate in this patent document is low, and the selectivity and yield of total alcohols and olefins are low. At the same time, a large amount of CO2 byproducts are generated during the reaction. Patent CN102319575A discloses a method with higher C... 5+Alcohol-selective Cu-Fe catalysts are low-cost, simple to prepare, and stable. However, the alcohols obtained by these catalysts are concentrated in C1-C4 alcohols, with low selectivity for higher alcohols. Patent CN 105664964 B reports a Cu and Co mixed oxide catalyst for the production of higher alcohols from syngas. This catalyst has the advantages of high activity and high total alcohol selectivity; however, metallic copper is prone to agglomeration and deactivation during the reaction, resulting in a short catalyst lifetime. In summary, the syngas-to-higher alcohol catalysts reported in current patents generally suffer from low syngas conversion rates, low selectivity for higher alcohols and olefins, and catalyst instability, requiring further improvement. Summary of the Invention

[0004] The objective of this invention is to prepare Na-CoFeO by employing a co-current titration strategy with a special precipitant and nitrate. X This solid solution catalyst enhances CO adsorption and carbon chain insertion through oxygen vacancies, thereby improving CO conversion and selectivity for higher alcohols and olefins. The carbonization of cobalt and iron into carbides during the reaction inhibits hydrogenation, reducing CH4 formation. Furthermore, the strong interaction between the bimetallic compounds facilitates control and stability of the active reaction sites, further enhancing catalyst stability. No significant deactivation was observed in the catalyst after 1000 hours of reaction.

[0005] Na-CoFeO X Preparation process of solid solution catalysts:

[0006] (1) Dissolve the soluble salts of Co and Fe in 20-100 ml of ethanol at a metal molar ratio of 5:1-50:1 to prepare a mixture;

[0007] The soluble salts of Co are one or more of cobalt nitrate, cobalt acetate, cobalt sulfate, and cobalt hydrochloride; the soluble salts of Fe are one or more of ferric nitrate, ferric acetate, ferric chloride, and ferrous sulfate.

[0008] (2) Prepare a 0.1 mol / L to 10 mol / L precipitant aqueous solution, wherein the precipitant is one or more of potassium hydroxide, ammonium chloride, ammonium carbonate and sodium hydroxide.

[0009] (3) Add 0.5-3g of Na soluble salt to the mixture after step (1) and sonicate at 35-50℃ for 6-10 hours. Then add the solution from steps (1) and (2) dropwise at 50-150℃ using a peristaltic pump with a flow rate of 0.01ml / min-0.5ml / min, pH=7-10.

[0010] Soluble salts of Na include one or more of sodium nitrate, sodium chloride, sodium carbonate, and sodium sulfate.

[0011] (4) The mixture after step (3) is subjected to rotary evaporation at 50-100℃ for 5-15 hours, and then washed and filtered with deionized water to obtain filter cake;

[0012] (5) Dry the filter cake obtained in step (4) under vacuum at 50-100℃ for 5-20 hours, and then dry it at a gas hourly space velocity of 2000-4000 h⁻¹. -1 Na-CoFeO was obtained by calcination at 600-1100℃ for 5-15 hours under an argon atmosphere. X Solid solution catalyst.

[0013] The Na-CoFeO X Solid solution catalysts can be used in syngas reforming reactions to produce higher alcohols and co-produce higher olefins. The catalyst is first loaded into the isothermal zone of a reaction tube, which is then filled entirely with quartz sand. Before use, the catalyst is reduced and activated in hydrogen or a hydrogen-inert gas mixture at 300–600°C for 1–50 h at a gas hourly space velocity (GHSV) of 200–10000 h⁻¹. -1 After activation, adjust to the specified reaction conditions, wherein the volume ratio of H2 to CO in the syngas is 0.5–10, the reaction temperature is 180–350℃, the reaction pressure is 0.5–10 MPa, and the syngas space velocity is 500–8000 h⁻¹. -1 .

[0014] The beneficial effects of this invention are: it proposes a novel method for preparing co-current titration solid solution catalysts, and successfully prepares Na-CoFeO. X This catalyst was developed and applied to the reaction of syngas reforming to produce higher alcohols and co-producing higher olefins. The catalyst utilizes oxygen vacancies to enhance CO adsorption and carbon chain insertion, thereby improving CO conversion and the selectivity for higher alcohols and olefins. The carbonization of cobalt and iron into carbides during the reaction inhibits hydrogenation, reducing CH4 formation. Furthermore, the strong interaction between the bimetallic compounds facilitates the control and stability of the active reaction sites, thus improving catalyst stability. No significant deactivation was observed in the catalyst after 1000 hours of reaction.

[0015] This catalyst exhibits high activity and high C content. 6+ alcohols and C 5+ The reaction exhibits olefin selectivity and stability, with operating temperatures ranging from 200 to 350°C and reaction pressures between 0.5 MPa and 10 MPa. The catalyst structure is stable during the reaction, the preparation method is simple and easily reproducible, facilitating industrial application. Detailed Implementation

[0016] To better understand the present invention, the technical solution of the present invention will be described in detail below with reference to the embodiments. The embodiments given do not limit the scope of protection of the present invention.

[0017] Example 1

[0018] (1) Take 2g of cobalt nitrate hexahydrate and 0.3g of ferric acetate and dissolve them in 30ml of ethanol and mix them evenly.

[0019] (2) Dissolve 1.5g of ammonium chloride and 2g of sodium hydroxide in deionized water to prepare a precipitant with a total concentration of 3mol / L.

[0020] (3) Add 1g of sodium nitrate to the mixture after treatment in step (1) and sonicate at 50°C for 6 hours to obtain a mixture. Then, add the mixture and the solution from step (2) to the same container using a peristaltic pump with a co-current dripping strategy at 100°C and a flow rate of 0.1ml / min until pH=8.

[0021] (4) The mixture after step (3) is subjected to rotary evaporation at 50°C for 10 hours, and then washed and filtered with deionized water to obtain filter cake.

[0022] (5) The obtained filter cake was vacuum dried at 80℃ for 12h, and finally dried under an argon atmosphere with a space velocity of 3000h. -1 Na-CoFeO was obtained by calcination at 800℃ for 10 hours. X catalyst.

[0023] The catalyst was first activated at 400°C for 5 hours under hydrogen conditions with a gas space velocity of 2000 h⁻¹. -1 The reaction was carried out at a H2 to CO volume ratio of 3, a reaction temperature of 250℃, a reaction pressure of 5MPa, and a syngas space velocity of 6000h. -1 The reaction was carried out under the specified conditions, and the results are shown in Table 1.

[0024] Example 2

[0025] (1) Take 3g of cobalt acetate and 0.8g of iron acetate and dissolve them in 50ml of ethanol and mix them evenly.

[0026] (2) Dissolve 2.3g of ammonium chloride and 3g of sodium hydroxide in deionized water to prepare a 5mol / L precipitant.

[0027] (3) Add 1.5g of sodium nitrate to the mixture after treatment in step (1) and sonicate at 50°C for 6 hours to obtain a mixture. Then, add the mixture and the solution from step (2) to the same container using a peristaltic pump with a co-current dripping strategy at 60°C at a flow rate of 0.1ml / min until the pH is 7.5.

[0028] (4) The mixture after step (3) is subjected to rotary evaporation at 50°C for 10 hours, and then washed and filtered with deionized water to obtain filter cake.

[0029] (5) The obtained filter cake was vacuum dried at 80℃ for 12h, and finally dried under an argon atmosphere with a space velocity of 4000h. -1 Na-CoFeO was obtained by calcination at 800℃ for 10 hours. X catalyst.

[0030] The catalyst was first activated at 500°C for 5 hours under hydrogen conditions with a gas space velocity of 1000 h⁻¹. -1 The reaction was carried out at a H2 to CO volume ratio of 5, a reaction temperature of 260℃, a reaction pressure of 5 MPa, and a syngas space velocity of 4000 h⁻¹. -1 The reaction was carried out under the specified conditions, and the results are shown in Table 1.

[0031] Example 3

[0032] (1) Take 2g of cobalt hydrochloride and 0.5g of ferric nitrate and dissolve them in 50ml of ethanol and mix them evenly.

[0033] (2) Dissolve 5g of ammonium carbonate in deionized water to prepare a 5mol / L precipitant.

[0034] (3) Add 2.0g of sodium nitrate to the mixture after treatment in step (1) and sonicate at 50°C for 6 hours to obtain a mixture. Then, add the mixture and the solution from step (2) to the same container using a peristaltic pump with a co-current dripping strategy at 80°C and a flow rate of 0.5ml / min until pH=9.

[0035] (4) The mixture after step (3) is subjected to rotary evaporation at 50°C for 10 hours, and then washed and filtered with deionized water to obtain filter cake.

[0036] (5) The obtained filter cake was vacuum dried at 80℃ for 12h, and finally dried under an argon atmosphere with a space velocity of 4000h. -1 Na-CoFeO was obtained by calcination at 900℃ for 10 hours. X Catalyst. The catalyst was first activated at 500℃ for 5 hours under hydrogen conditions with a gas space velocity of 1000 h⁻¹. -1 The reaction was carried out at a H2 to CO volume ratio of 2, a reaction temperature of 240℃, a reaction pressure of 5MPa, and a syngas space velocity of 4000h⁻¹. -1 The reaction was carried out under the specified conditions, and the results are shown in Table 1.

[0037] Example 4

[0038] (1) Dissolve 3g of cobalt sulfate and 0.8g of ferric chloride in 50ml of ethanol and mix well.

[0039] (2) Dissolve 4.5g of ammonium chloride in deionized water to prepare a 4mol / L precipitant.

[0040] (3) Add 1.0g of sodium carbonate to the mixture after treatment in step (1) and sonicate at 50°C for 6 hours to obtain a mixture. Then, add the mixture and the solution from step (2) to the same container using a peristaltic pump with a co-current dripping strategy at 80°C and a flow rate of 0.3ml / min until pH=8.

[0041] (4) The mixture after step (3) is subjected to rotary evaporation at 70°C for 10 hours, and then washed and filtered with deionized water to obtain filter cake.

[0042] (5) The obtained filter cake was vacuum dried at 80℃ for 12h, and finally dried under an argon atmosphere with a space velocity of 3000h. -1 Na-CoFeO was obtained by calcination at 800℃ for 10 hours. X Catalyst. The catalyst was first activated at 500°C for 5 hours under hydrogen conditions with a gas space velocity of 500 h⁻¹. -1 The reaction was carried out at a H2 to CO volume ratio of 5, a reaction temperature of 280℃, a reaction pressure of 6MPa, and a syngas space velocity of 4000 h⁻¹. -1 The reaction was carried out under the specified conditions, and the results are shown in Table 1.

[0043] Example 5

[0044] (1) Dissolve 5g of cobalt acetate and 1.5g of ferric chloride in 80ml of ethanol and mix well.

[0045] (2) Dissolve 3.5g of potassium hydroxide and 4g of ammonium chloride in deionized water to prepare an 8mol / L precipitant.

[0046] (3) Add 1.5g of sodium chloride to the mixture after treatment in step (1) and sonicate at 50°C for 6 hours to obtain a mixture. Then, add the mixture and the solution from step (2) to the same container using a peristaltic pump with a co-current dripping strategy at 80°C and a flow rate of 0.2ml / min until pH=7.

[0047] (4) The mixture after step (3) is subjected to rotary evaporation at 70°C for 15 hours, and then washed and filtered with deionized water to obtain filter cake.

[0048] (5) The obtained filter cake was vacuum dried at 80℃ for 12h, and finally dried under an argon atmosphere with a space velocity of 4000h. -1 Na-CoFeO was obtained by calcination at 1000℃ for 10 hours. X Catalyst. The catalyst was first activated at 600℃ for 5 hours under hydrogen conditions with a gas space velocity of 500 h⁻¹. -1The reaction was carried out at a H2 to CO volume ratio of 1, a reaction temperature of 280℃, a reaction pressure of 6MPa, and a syngas space velocity of 4000 h⁻¹. -1 The reaction was carried out under the specified conditions, and the results are shown in Table 1.

[0049] Example 6

[0050] (1) Dissolve 4g of cobalt acetate and 0.5g of iron acetate in 50ml of ethanol and mix well.

[0051] (2) Dissolve 6g of sodium hydroxide in deionized water to prepare a 5mol / L precipitant.

[0052] (3) Add 2.0g of sodium nitrate to the mixture after treatment in step (1) and sonicate at 50°C for 6 hours to obtain a mixture. Then, add the mixture and the solution from step (2) to the same container using a peristaltic pump with a co-current dripping strategy at 100°C and a flow rate of 0.2ml / min until pH=9.

[0053] (4) The mixture after step (3) is subjected to rotary evaporation at 80°C for 8 hours, and then washed and filtered with deionized water to obtain filter cake.

[0054] (5) The obtained filter cake was vacuum dried at 70℃ for 12h, and finally dried under an argon atmosphere with a space velocity of 3000h. -1 Na-CoFeO was obtained by calcination at 800℃ for 10 hours. X Catalyst. The catalyst was first activated at 500°C for 5 hours under hydrogen conditions with a gas space velocity of 800 h⁻¹. -1 The reaction was carried out at a H2 to CO volume ratio of 3, a reaction temperature of 280℃, a reaction pressure of 6MPa, and a syngas space velocity of 4000 h⁻¹. -1 The reaction was carried out under the specified conditions, and the results are shown in Table 1.

[0055] Comparative Example 1

[0056] (1) Dissolve 4g of cobalt acetate and 0.5g of ferric acetate in 50ml of deionized water and mix.

[0057] (2) After ultrasonic treatment of the obtained mixture for 5 hours, add 2g of sodium nitrate. Mix well after stirring.

[0058] (3) Add 5 mol / L urea aqueous solution to carry out precipitation reaction, filter and wash to obtain filter cake;

[0059] (4) The obtained filter cake was dried in air at 70°C for 12 hours, and finally dried under a nitrogen atmosphere with a space velocity of 3000 h⁻¹. -1 The Na-CoFe catalyst was obtained by calcination at 800℃ for 10 h. This catalyst was then activated at 500℃ for 5 h under hydrogen atmosphere with a gas space velocity of 1000 h⁻¹. -1The reaction was carried out at a H2 to CO volume ratio of 3, a reaction temperature of 280℃, a reaction pressure of 6MPa, and a syngas space velocity of 4000 h⁻¹. -1 The reaction was carried out under the specified conditions, and the results are shown in Table 1.

[0060] Comparative Example 2

[0061] (1) Dissolve 5g of cobalt acetate and 1.5g of sodium chloride in 10ml of deionized water;

[0062] (2) Add 8g of iron oxide carrier for impregnation;

[0063] (3) The obtained solid was dried in air at 80°C for 12 hours, and finally dried under a nitrogen atmosphere with a space velocity of 4000 h⁻¹. -1 The Na-Co / Fe3O4 catalyst was obtained by calcination at 1000℃ for 10 hours.

[0064] The catalyst was first activated at 600℃ for 5 hours under hydrogen conditions with a gas space velocity of 2000 h⁻¹. -1 The reaction was carried out at a H2 to CO volume ratio of 5, a reaction temperature of 280℃, a reaction pressure of 6MPa, and a syngas space velocity of 4000 h⁻¹. -1 The reaction was carried out under the specified conditions, and the results are shown in Table 1.

[0065] Table 1. Evaluation of the performance of the catalyst in the CO hydrogenation reaction and analysis of the products.

[0066]

[0067] As can be seen from Table 1, compared with the traditional catalyst preparation methods of Comparative Examples 1 and 2, the co-current titration solid solution catalyst preparation method used in the embodiments of the present invention successfully prepared Na-CoFeO. X Catalysts enhance CO adsorption and carbon chain insertion through oxygen vacancies, thereby increasing CO conversion and selectivity for higher alcohols and olefins. The carbonization of cobalt and iron into carbides during the reaction inhibits hydrogenation, reducing CH4 formation. Furthermore, the strong interactions between bimetallic compounds facilitate control and stability of the active reaction sites, further improving catalyst stability.

[0068] The specific embodiments of the present invention have been described above. It should be noted that the present invention is not limited to the specific embodiments described above. All modifications, equivalent substitutions, improvements, etc., made within the principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for preparing a Na-modified cobalt-iron solid solution catalyst, characterized in that: The preparation process includes: (1) Dissolve soluble salts of Co and soluble salts of Fe in 20-100 ml of ethanol at a metal molar ratio of 5:1-50:1 to prepare a mixture; wherein the mass concentration of Co is 0.5 mg / ml-100 mg / ml; (2) Prepare an aqueous solution of 0.1 mol / L to 10 mol / L precipitant; (3) Add 0.5-3g of soluble Na salt to 50g of the mixture treated in step (1), and sonicate at 35-50℃ for 6-10 hours to obtain a mixture. Then, add the mixture and the solution from step (2) dropwise into the same container using a co-current dropwise addition strategy, and sonicate at 50-150℃. o C was added dropwise at a flow rate of 0.01 ml / min to 0.5 ml / min until the pH reached 7-10, to obtain a precipitate mixture; (4) The mixture after step (3) is heated at 50-100°C. o C. Perform rotary evaporation for 5-15 hours, then wash with water and filter to obtain filter cake; (5) Dry the filter cake obtained in step (4), and then calcine it at 600-1100℃ for 5-15h under an inert atmosphere to obtain Na-CoFeO. X Solid solution catalyst.

2. The preparation method according to claim 1, characterized in that, The soluble salts of Co are one or more of cobalt nitrate, cobalt acetate, cobalt sulfate, and cobalt hydrochloride; the soluble salts of Fe are one or more of ferric nitrate, ferric acetate, ferric chloride, and ferrous sulfate.

3. The preparation method according to claim 1, characterized in that, The soluble salts of Na are one or more of sodium nitrate, sodium chloride, sodium carbonate, and sodium sulfate; the inert atmosphere is one or more of helium, nitrogen, and argon.

4. The preparation method according to claim 1, characterized in that, The precipitant is one or more of potassium hydroxide, ammonium carbonate, and sodium hydroxide; Step (5) Dry the filter cake obtained in step (4) under vacuum at 50-100℃ for 5-20 hours, and then dry it at a gas hourly space velocity of 2000-4000 h⁻¹. -1 Na-CoFeO was obtained by calcination at 600-1100℃ for 5-15 hours under an argon atmosphere. X Solid solution catalyst.

5. A catalyst prepared according to any one of claims 1-4.

6. The catalyst according to claim 5, characterized in that: The catalyst consists of a solid solution component and an auxiliary component, wherein the solid solution component is a cobalt-iron solid solution, the auxiliary component is elemental sodium or an oxide, and the reactive centers are cobalt-iron solid solution, cobalt and cobalt carbide or cobalt oxide species, and elemental sodium or an oxide.

7. The application of the catalyst according to claim 5 or 6 in the preparation of higher alcohols and co-production of higher olefins in a catalytic syngas conversion reaction.

8. The application according to claim 7, characterized in that, The catalyst precursor is reduced and activated before use. The reducing gas is hydrogen or a mixture of hydrogen and nitrogen, with a hydrogen to nitrogen volume ratio of 1% to 99%. The reduction and activation temperature is 300 to 600℃, the reduction and activation time is 1 to 50 hours, and the gas space velocity is 200 to 10000 h⁻¹. -1 .

9. The application according to claim 7 or 8, characterized in that: The volume ratio of H2 to CO in the syngas is 0.5–10, the reaction temperature is 180–350 °C, the reaction pressure is 0.5–10 MPa, and the syngas space velocity is 500–8000 h⁻¹. -1 .

10. The application according to claim 7 or 8, characterized in that, Higher alcohols refer to alcohols with six or more carbon atoms, while higher olefins refer to α-olefins with five or more carbon atoms.

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