Solid acid catalyst, preparation and use in bioethanol dehydration

Abstract

This invention relates to a solid acid catalyst, its preparation, and its application in the catalytic dehydration of bioethanol to ethylene. The active component of the catalyst comprises two parts: (1) a main catalyst and (2) a co-catalyst. This invention utilizes a suitable amount of chelating agent to chelate with the metal in the heteropolyacid, thereby inhibiting the aggregation of heteropolyacid particles and improving dispersion; and by introducing other functional groups to modulate the acid strength and acid density of the catalyst, it inhibits the formation of carbon deposits, thus improving the stability of the catalyst. The catalyst prepared under mild conditions and with a stable and controllable process, the resulting catalyst has advantages such as low reaction temperature, high activity, good stability, and strong resistance to carbon deposition.

Description

Technical Field

[0001] This invention relates to a catalytic method for the dehydration of bioethanol to produce bioethylene, specifically a catalytic dehydration method for bioethanol on an oxyacid-modified heteropolyacid catalyst. Background Technology

[0002] Ethylene, as an important chemical raw material, can be used to synthesize important chemical products such as polyethylene, ethylene oxide, polyvinyl chloride, PET, and ethylbenzene. In my country, ethylene is mainly produced through naphtha cracking and coal-to-olefins (CTO) processes, with large-scale plants exceeding one million tons per year. Using ethanol dehydration to produce ethylene can overcome the constraints of oil and gas resources, enabling flexible small- to medium-scale production of high-purity ethylene and meeting market demand. Ethanol can be produced from biomass, industrial waste gas, coal, and solid waste through fermentation or thermochemical conversion processes, providing a wide range of raw material sources. Producing bioethylene from bioethanol is of great significance for reducing greenhouse gas emissions and achieving dual-carbon goals. Bioethanol dehydration to ethylene technology has a simple reaction process, is suitable for small-scale production, is environmentally friendly, and can partially or completely replace petroleum-based ethylene, possessing significant economic value and energy strategic importance.

[0003] Developing efficient and stable solid acid catalysts is crucial for the dehydration of bioethanol to ethylene. Catalysts mainly include activated alumina, molecular sieves, and heteropoly acids. Activated alumina requires high temperature and low space velocity operation, resulting in high energy consumption and low equipment utilization. Patent CN101244971A reports a method for using a nano-molecular sieve catalyst to catalyze the dehydration of bioethanol to ethylene, requiring a lower reaction temperature and achieving higher ethanol conversion and ethylene selectivity. However, this process requires a carrier gas, the catalyst has poor stability, and the catalyst preparation conditions are stringent, with difficulty in controlling crystallinity. These issues limit its further industrial application. Patents CN105709822A and CN106944139A disclose a method for catalyzing the dehydration of ethanol to ethylene using heteropoly acid ammonium salts, but this method is prone to carbon deposition, leading to a decrease in activity.

[0004] By introducing an appropriate amount of chelating agent to chelate with the metals in heteropolyacids, the aggregation of heteropolyacid particles is inhibited, and the dispersion is improved. Furthermore, by introducing other functional groups to modulate the acid strength and density of the catalyst, the formation of coke deposits is suppressed, thereby improving the catalyst's stability. This method provides mild catalyst preparation conditions, a stable and controllable process, and the resulting catalyst exhibits advantages such as low reaction temperature, high activity, good stability, and strong resistance to coke deposition, making it applicable to acid catalysis fields such as alcohol dehydration. Summary of the Invention

[0005] The problem to be solved by the present invention is to provide a method for preparing a catalyst for the dehydration of bioethanol to bioethylene with mild reaction conditions, controllable preparation process and simple steps. The catalyst has the advantages of mild reaction conditions, high activity and good stability at high space velocities. It can be applied to acid-catalyzed alcohol dehydration reaction and has broad application prospects.

[0006] The technical solution is as follows:

[0007] The method for preparing a highly active and stable catalyst for the dehydration of bioethanol to bioethylene according to the present invention includes the following steps:

[0008] Preferably, the raw materials for the main catalyst and the co-catalyst are prepared into a solution using a co-impregnation method, impregnated onto a γ-Al₂O₃ support, aged for 8-16 hours, dried at 110-130℃ for 6-18 hours, and calcined at 200-400℃ for 2-8 hours to obtain a highly stable catalyst for the dehydration of bioethanol to bioethylene. The addition of the co-catalyst is a key step in this invention. Its functions are: by introducing an appropriate amount of chelating agent, it chelates with the metal in the heteropolyacid, inhibiting the agglomeration of heteropolyacid particles and improving dispersion; by introducing other functional groups, it modulates the acid strength and acid density of the catalyst, inhibiting the formation of carbon deposits, thereby improving the stability of the catalyst.

[0009] Preferably, the support is γ-Al₂O₃ with the following properties: specific surface area 200±50 m² / g. 2 / g, pore volume 0.6±0.2mL / g, average pore size 8±2nm.

[0010] Preferably, the co-catalyst is EDTA, and the molar ratio of EDTA to the heteropolyacid coordination metal is 1:40.

[0011] Preferably, the active component is phosphotungstic acid, and the content of the active component is 10-40 wt%.

[0012] Application of a highly active and stable heteropolyacid catalyst in the dehydration of bioethanol to bioethylene.

[0013] Preferably, a fixed-bed reactor is used, with bioethanol as the feedstock, a reaction temperature of 220-280℃, a reaction pressure of 0.5-1.5 MPa, and a mass hourly space velocity (WHSV) of 1-20 h⁻¹ based on ethanol. -1 .

[0014] Beneficial technical effects

[0015] 1. This invention prepares a bioethanol dehydration catalyst by co-impregnating an additive and an active component. The steps are simple, the conditions are mild, and the process is controllable. The prepared catalyst has the advantages of low reaction temperature, high activity, good stability, and strong resistance to carbon deposition. The reaction process is simple, controllable, and easy to operate, and has broad application prospects.

[0016] 2. By introducing an appropriate amount of chelating agent, chelation occurs with the metals in the heteropolyacid, inhibiting the aggregation of heteropolyacid particles, promoting the dispersion of active components, and improving reaction activity; by introducing other functional groups to modulate the acid strength and acid density of the catalyst, the formation of carbon deposits is inhibited, thereby improving the stability of the catalyst. Detailed Implementation

[0017] To provide a more detailed description of the present invention, several specific implementation examples are given below, but the present invention is not limited to these embodiments.

[0018] Example 1

[0019] (1) Catalyst preparation: Weigh 1.67g H3PW 12 O 40 • 24H2O and 0.102g EDTA were dissolved in 10mL of deionized water to form an impregnation solution. The impregnation solution was added dropwise to 5.0g γ-Al2O3 support under constant stirring. The mixture was aged at room temperature for 12h, dried at 120℃ for 12h, and calcined at 300℃ for 4h in nitrogen (flow rate 50mL / min) to obtain the catalyst, which was designated as catalyst 1. The content of heteropoly acid was 25wt% (molar ratio of EDTA to W was 1:20).

[0020] (2) Catalyst evaluation: The reaction was carried out in a fixed-bed tubular reactor with bioethanol as the feedstock. The reaction temperature was 240℃, the reaction pressure was 1.0 MPa, and the mass hourly space velocity was 10 h⁻¹. -1 After gas-liquid separation, the products were analyzed by gas chromatography to determine their composition and content. The tail gas flow rate was monitored and statistically analyzed using a flow meter. The conversion rate of ethanol and the selectivity of ethylene and diethyl ether were calculated by combining the reaction results of the gas and liquid phases.

[0021] Comparative Example 1

[0022] Comparative Example 1 differs from Example 1 (the process and conditions are the same as in Example 1) in that the impregnation solution does not contain EDTA, but otherwise it is exactly the same as in Example 1; the resulting catalyst is referred to as Catalyst 2.

[0023] Example 2: Different types of chelating agents – NTA

[0024] Example 2 differs from Example 1 (the process and conditions are the same as in Example 1) in that 0.102g of EDTA in the impregnation solution is replaced with 0.067g of NTA, while the rest is exactly the same as in Example 1; the resulting catalyst is designated as catalyst 3.

[0025] Example 3: Different types of chelating agents – DEG

[0026] Compared with Example 1 (the process and conditions are the same as in Example 1), Example 3 differs in that 0.102g of EDTA in the impregnation solution is replaced with 0.057g of DEG, while the rest is exactly the same as in Example 1; the resulting catalyst is designated as Catalyst 4.

[0027] Example 4: Different types of chelating agents – CA

[0028] Compared with Example 1 (the process and conditions are the same as in Example 1), Example 4 differs in that 0.102g of EDTA in the impregnation solution is replaced with 0.067g of CA, while the rest is exactly the same as in Example 1; the resulting catalyst is designated as Catalyst 5.

[0029] Example 5: Different types of chelating agents – CTAB

[0030] Example 5 differs from Example 1 (the process and conditions are the same as in Example 1) in that 0.102g of EDTA in the impregnation solution is replaced with 0.127g of CTAB, while the rest is exactly the same as in Example 1; the resulting catalyst is designated as Catalyst 6.

[0031] Example 6: Different molar ratio of chelating agent to heteropolyacid coordination metal—1:10

[0032] Compared with Example 1 (the process and conditions are the same as in Example 1), Example 6 differs in that the EDTA content in the impregnation solution is 0.204 g, while the rest is exactly the same as in Example 1; the catalyst prepared is designated as Catalyst 7, in which the content of heteropoly acid is 25 wt% (the molar ratio of EDTA to W is 1:10).

[0033] Example 7: Different molar ratio of chelating agent to heteropolyacid coordination metal—1:40

[0034] Compared with Example 1 (the process and conditions are the same as in Example 1), Example 7 differs in that the EDTA content in the impregnation solution is 0.051 g, while the rest is exactly the same as in Example 1; the catalyst prepared is designated as Catalyst 8, in which the content of heteropoly acid is 25 wt% (the molar ratio of EDTA to W is 1:40).

[0035] Example 8: Different loading of active ingredients—10wt%

[0036] Example 8 differs from Example 1 (the process and conditions are the same as in Example 1) in that the impregnation solution contains 0.56g of H3PW. 12 O 40 • 24H2O and 0.034g EDTA, the rest is exactly the same as in Example 1; the resulting catalyst is designated as Catalyst 9, wherein the content of heteropoly acid is 10wt% (the molar ratio of EDTA to W is 1:20).

[0037] Example 9: Different loading of active ingredients—40wt%

[0038] Example 9 differs from Example 1 (which uses the same process and conditions) in that the impregnation solution contains 3.33 g of H3PW. 12 O 40 • 24H2O and 0.203g EDTA, the rest is exactly the same as in Example 1; the resulting catalyst is designated as Catalyst 10, wherein the content of heteropoly acid is 40wt% (the molar ratio of EDTA to W is 1:20).

[0039] Example 10: Different impregnation order – first heteropoly acid, then chelating agent

[0040] (1) Weigh 1.67g H3PW 12 O 40 • 24H2O was dissolved in 10mL of deionized water to form impregnation solution A. Impregnation solution A was added dropwise to 5.0g of γ-Al2O3 support under constant stirring. The mixture was aged at room temperature for 12h, dried at 120℃ for 12h, and calcined at 300℃ for 4h in nitrogen (flow rate 50mL / min) to obtain the catalyst precursor. (2) 0.102g of EDTA was weighed and dissolved in 10mL of deionized water to form impregnation solution B. The impregnation solution was added dropwise to the catalyst precursor obtained in step (1) under constant stirring. The mixture was aged at room temperature for 12h, dried at 120℃ for 12h, and calcined at 300℃ for 4h in nitrogen (flow rate 50mL / min) to obtain the catalyst, which was designated as catalyst 11. The remaining processes and conditions were exactly the same as in Example 1.

[0041] Example 11: Different impregnation order - chelating agent first, then heteropoly acid

[0042] (1) Weigh 0.102g of EDTA and dissolve it in 10mL of deionized water to form impregnation solution A. Add impregnation solution A dropwise to 5.0g of γ-Al2O3 support while stirring continuously. Let it mature at room temperature for 12h, dry it at 120℃ for 12h, and calcine it at 300℃ for 4h in nitrogen (flow rate 50mL / min) to obtain the catalyst precursor; (2) Weigh 1.67g of H3PW 12 O 40 • 24H2O was dissolved in 10 mL of deionized water to form impregnation solution B. The impregnation solution was added dropwise to the catalyst precursor obtained in step (1) under constant stirring. The catalyst was aged at room temperature for 12 h, dried at 120 °C for 12 h, and calcined at 300 °C for 4 h in nitrogen (flow rate 50 mL / min) to obtain the catalyst, which was designated as catalyst 12. The remaining processes and conditions were exactly the same as in Example 1.

[0043] Example 12: Different ripening time, drying temperature, and time

[0044] Compared with Example 1 (the process and conditions are the same as in Example 1), Example 12 differs in that the support is SiO2, the aging time is 8h, the drying temperature is 110℃, and the drying time is 18h. The rest is exactly the same as in Example 1. The catalyst obtained is designated as Catalyst 13.

[0045] Example 13: Different ripening time, drying temperature, and time

[0046] Compared with Example 1 (the process and conditions are the same as in Example 1), Example 13 differs in that the support is TiO2, the aging time is 8h, the drying temperature is 130℃, and the drying time is 6h. The rest is exactly the same as in Example 1. The catalyst obtained is designated as Catalyst 14.

[0047] Example 14: Different roasting temperatures, times, and atmospheres

[0048] Compared with Example 1 (the process and conditions are the same as in Example 1), Example 14 differs in that the support is CeO2, the calcination temperature is 400℃, the calcination time is 2h, and the calcination atmosphere is argon. The rest is exactly the same as in Example 1. The catalyst obtained is designated as Catalyst 15.

[0049] Example 15: Different roasting temperatures and times

[0050] Compared with Example 1 (the process and conditions are the same as in Example 1), Example 15 is different in that the support is ASA, the calcination temperature is 200°C, and the calcination time is 8h. The rest is exactly the same as in Example 1. The catalyst obtained is designated as Catalyst 16.

[0051] Example 16: Different types of active components – phosphotungstic acid

[0052] Example 16 differs from Example 1 (the process and conditions are the same as in Example 1) in that the impregnation solution contains 1.67g of H4SiW. 12 O 40 The catalyst prepared was 24H2O and 0.102g EDTA, and the rest was exactly the same as in Example 1; the catalyst was designated as Catalyst 17.

[0053] Comparative Example 2

[0054] Comparative Example 2 differs from Example 16 (the process and conditions are the same as in Example 1) in that the impregnation solution does not contain EDTA, but otherwise it is exactly the same as in Example 16; the resulting catalyst is designated as Catalyst 18.

[0055] Example 17: Different types of active components – phosphomolybdic acid

[0056] Example 17 differs from Example 1 (the process and conditions are the same as in Example 1) in that the impregnation solution contains 1.67 g of H3PMo. 12 O 40 • 24H2O and 0.16g EDTA, the rest is exactly the same as in Example 1; the resulting catalyst is designated as Catalyst 19.

[0057] Comparative Example 3

[0058] Comparative Example 3 differs from Example 17 (the process and conditions are the same as in Example 1) in that the impregnation solution does not contain EDTA, but otherwise it is exactly the same as in Example 17; the resulting catalyst is designated as Catalyst 20.

[0059] The table below lists the reaction evaluation results of the catalysts prepared by the method described in this invention.

[0060]

[0061] As can be seen from Examples 1 and 1 Comparative Example 1, Examples 16 and 2 Comparative Example 2, Examples 17 and 3 Comparative Example 3, the addition of chelating agents is beneficial to improving the stability of ethanol dehydration to ethylene; as can be seen from Examples 1 and 2-5, citric acid has the best effect; as can be seen from Examples 1, 10 and 11, the effect is best when chelating agents and heteropoly acids are co-impregnated; as can be seen from Examples 1, 6-9 and 12-15, the preparation conditions of Example 1 are optimal.

Claims

1. The application of a modified heteropolyacid catalyst in the catalytic dehydration of bioethanol to produce ethylene, the catalyst comprising a main catalyst, a co-catalyst, and a support, wherein the main catalyst is a heteropolyacid with a content of 5-50 wt%; the co-catalyst is a chelating agent with a molar ratio of the chelating agent to the heteropolyacid coordination metal of 1 / 5-1 / 80; the remaining components are the support; the main catalyst is one or more of silicotungstic acid, phosphotungstic acid, and phosphomolybdic acid; The cocatalyst is one or more of ethylenediaminetetraacetic acid, aminotriacetic acid, dihydroxyethylglycine, citric acid, and hexadecyltrimethylammonium bromide.

2. The application according to claim 1, characterized in that: The heteropoly acid content is 10-40 wt%; the co-catalyst is a chelating agent, and the molar ratio of the chelating agent to the heteropoly acid coordination metal is 1 / 10-1 / 40.

3. The application according to claim 1, characterized in that: In the catalyst, the support is one or more of γ-Al2O3, SiO2, TiO2, CeO2, and ASA; the main catalyst and the co-catalyst are supported on the support.

4. The application according to claim 1, characterized in that: The main catalyst content in the catalyst is 5-50 wt%.

5. The application according to claim 4, characterized in that: The content of the main catalyst in the catalyst is 10-40 wt%.

6. The application according to claim 1, characterized in that: In the catalyst, the molar ratio of chelating agent to heteropolyacid coordination metal is 1:5 to 1:

80.

7. The application according to claim 6, characterized in that: In the catalyst, the molar ratio of chelating agent to heteropolyacid coordination metal is 1:10-1:

40.

8. The application according to claim 1, characterized in that: The catalyst was prepared by the equal volume impregnation method. The impregnation methods for the main catalyst and the co-catalyst were (1) impregnating the heteropoly acid first and then impregnating the chelating agent, or (2) impregnating the heteropoly acid and the chelating agent together, or (3) impregnating the chelating agent first and then impregnating the heteropoly acid.

9. The application according to claim 8, characterized in that: In method (1), the heteropoly acid aqueous solution is first impregnated onto the support, aged for 8-16 h, dried at 110-130 ℃ for 6-18 h, and calcined at 200-400 ℃ for 2-8 h in an inert atmosphere to obtain the catalyst precursor; then the chelating agent aqueous solution is impregnated onto the above catalyst precursor, aged for 8-16 h, dried at 110-130 ℃ for 6-18 h, and calcined at 200-400 ℃ for 2-8 h in an inert atmosphere to obtain the catalyst.

10. The application according to claim 8, characterized in that: In method (2), a mixed solution of chelating agent and heteropoly acid is impregnated onto the support, aged for 8-16 h, dried at 110-130 ℃ for 6-18 h, and calcined at 200-400 ℃ for 2-8 h in an inert atmosphere to obtain the catalyst.

11. The application according to claim 8, characterized in that: In method (3), the chelating agent aqueous solution is first impregnated onto the support, aged for 8-16 h, dried at 110-130 ℃ for 6-18 h, and calcined at 200-400 ℃ for 2-8 h in an inert atmosphere to obtain the catalyst precursor; then the heteropoly acid aqueous solution is impregnated onto the above catalyst precursor, aged for 8-16 h, dried at 110-130 ℃ for 6-18 h, and calcined at 200-400 ℃ for 2-8 h in an inert atmosphere to obtain the catalyst.

12. The application according to claim 1, characterized in that: A fixed-bed reactor was used, with bioethanol as the feedstock. The reaction temperature was 200-350 °C, and the reaction pressure was 0.1-2 MPa. The mass hourly space velocity (WHSV) was 0.5-20 h⁻¹ (based on ethanol). -1 .

13. The application according to claim 12, characterized in that: A fixed-bed reactor was used, with bioethanol as the feedstock. The reaction temperature was 220-280 °C, and the reaction pressure was 0.5-1.5 MPa. The mass hourly space velocity (WHSV) was 1-10 h⁻¹ based on ethanol. -1 .

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