Solid acid catalyst, preparation and application in bioethanol dehydration

Abstract

The invention relates to a solid acid catalyst, preparation and application of the solid acid catalyst in catalyzing dehydration of bioethanol to prepare ethylene. The active components of the catalyst comprise two parts: (1) a main catalyst and (2) a co-catalyst. According to the invention, the chelating agent with a proper content is loaded and is chelated with metal in heteropolyacid, so that heteropolyacid particles are inhibited from being agglomerated, and the dispersity is improved; other functional groups are introduced to modulate the acid strength and the acid density of the catalyst and inhibit the generation of carbon deposition, so that the stability of the catalyst is improved. The preparation conditions of the catalyst are mild, the process is stable and controllable, and the prepared catalyst has the advantages of being low in reaction temperature, high in activity, good in stability, high in carbon deposition resistance and the like.

Description

Technical Field

[0001] The invention relates to a catalytic method for dehydrating bioethanol to prepare bioethylene, and in particular to a catalytic dehydration method for bioethanol on an oxygen-containing acid-modified heteropolyacid catalyst. Background Art

[0002] As an important chemical raw material, ethylene can be used to synthesize important chemical products such as polyethylene, ethylene oxide, polyvinyl chloride, PET, and ethylbenzene. my country mainly produces ethylene through naphtha cracking and coal-to-methanol olefins process. The scale of the plant is large, and the production capacity exceeds one million tons per year. The use of ethanol dehydration to ethylene technology can get rid of the constraints of oil and gas resources, realize the flexible production of small and medium-sized high-purity ethylene, and meet the market demand for small and medium-sized ethylene. Ethanol can be produced through fermentation or thermochemical conversion processes from biomass, industrial waste gas, coal, solid waste, etc., and the raw materials come from a wide range of sources. The preparation of bio-ethylene using bioethanol as raw material is of great significance for reducing greenhouse gas emissions and achieving dual carbon goals. The technology of bioethanol dehydration to ethylene has a simple reaction process, is suitable for small-scale production, is environmentally friendly, can partially or completely replace petroleum ethylene, and has important economic value and energy strategic significance.

[0003] The development of efficient and stable solid acid catalysts is the key to the production of ethylene by dehydration of bioethanol. The catalysts mainly include activated alumina, molecular sieves and heteropoly acids. Activated alumina needs to be operated at high temperature and low space velocity, with high unit energy consumption and low equipment utilization. Patent CN101244971A reports a method for catalyzing the dehydration of bioethanol to produce ethylene using a nanomolecular sieve catalyst. The required reaction temperature is low, the ethanol conversion rate and ethylene selectivity are high, but the process requires the introduction of carrier gas, the catalyst stability is poor, the catalyst preparation conditions are harsh, and the crystallinity is difficult to control. These problems limit its further industrial application. Patents CN105709822A and CN106944139A disclose a method for catalyzing the dehydration of ethanol to produce ethylene using heteropoly acid ammonium salts, but it is easy to generate carbon deposits, resulting in decreased activity.

[0004] By introducing a suitable amount of chelating agent, chelating with the metal in the heteropoly acid, the agglomeration of heteropoly acid particles is inhibited and the dispersion is improved; by introducing other functional groups to adjust the acid strength and acid density of the catalyst, the formation of carbon deposition is inhibited, thereby improving the stability of the catalyst. The preparation conditions of the catalyst in this method are mild, the process is stable and controllable, and the prepared catalyst has the advantages of low reaction temperature, high activity, good stability, and strong resistance to carbon deposition, and can be applied 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 dehydrating bioethanol to produce bioethylene with mild reaction conditions, controllable preparation process and simple steps. The prepared catalyst has the advantages of mild reaction conditions, high activity and good stability at high space velocity, can be applied to acid-catalyzed alcohol dehydration reactions and has broad application prospects.

[0006] The technical solution is:

[0007] The method for preparing a high-activity and stable catalyst for dehydrating bioethanol to produce bioethylene of the present invention comprises the following steps:

[0008] Preferably, the raw materials of the main catalyst and the co-catalyst are prepared into a solution by a co-impregnation method, impregnated onto a γ-Al2O3 carrier, aged for 8-16 hours, dried at 110-130°C for 6-18 hours, and roasted at 200-400°C for 2-8 hours to obtain a high-stability catalyst for dehydration of bioethanol to bioethylene. Adding a co-catalyst is a key step of the present invention, and its functions are: by introducing a suitable amount of chelating agent, chelating with the metal in the heteropoly acid, inhibiting the agglomeration of heteropoly acid particles and improving the dispersion; by introducing other functional groups to adjust 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 carrier is γ-Al2O3, and the properties are: specific surface area 200±50m 2 / g, pore volume 0.6±0.2mL / g, average pore diameter 8±2nm.

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

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

[0012] The invention discloses an application of a highly active and stable heteropolyacid catalyst in the dehydration reaction of bioethanol to bioethylene.

[0013] Preferably, a fixed bed reactor is used, the raw material is bioethanol, the reaction temperature is 220-280°C, the reaction pressure is 0.5-1.5MPa, and the mass space velocity is 1-20h in terms of ethanol. -1 .

[0014] Beneficial technical effects

[0015] 1. The present invention prepares a bioethanol dehydration catalyst by co-impregnation of an auxiliary agent and an active component, and 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, strong resistance to carbon deposition, etc. 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 metal in the heteropolyacid, inhibiting the agglomeration of heteropolyacid particles, promoting the dispersion of active components, and improving reaction activity; by introducing other functional groups to adjust the acid strength and acid density of the catalyst, the formation of carbon deposits is inhibited, thereby improving the stability of the catalyst. DETAILED DESCRIPTION

[0017] In order to further explain the present invention in detail, several specific implementation cases are given below, but the present invention is not limited to these embodiments.

[0018] Example 1

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

[0020] (2) Catalyst evaluation: The catalyst was evaluated in a fixed bed tubular reactor. The raw material was bioethanol. The reaction temperature was 240°C, the reaction pressure was 1.0 MPa, and the mass space velocity was 10 h -1 After gas-liquid separation, the products were respectively sent to gas chromatography for analysis of composition and content. The tail gas flow rate was monitored and counted by a flow meter. The conversion rate of ethanol and the selectivity of ethylene and ether were calculated based on the comprehensive reaction results of the gas-liquid phase.

[0021] Comparative Example 1

[0022] Comparative Example 1 is compared with Example 1 (the process and conditions are the same as Example 1), except that the impregnation solution does not contain EDTA, and the rest is exactly the same as Example 1; the prepared catalyst is recorded as Catalyst 2.

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

[0024] Compared with Example 1 (the process and conditions are the same as Example 1), Example 2 is different in that 0.102g EDTA in the impregnation solution is replaced by 0.067g NTA, and the rest is exactly the same as Example 1; the prepared catalyst is recorded 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 Example 1), Example 3 is different in that 0.102g EDTA in the impregnation solution is replaced by 0.057g DEG, and the rest is exactly the same as Example 1; the prepared catalyst is recorded 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 Example 1), Example 4 is different in that 0.102g EDTA in the impregnation solution is replaced by 0.067g CA, and the rest is exactly the same as Example 1; the prepared catalyst is recorded as Catalyst 5.

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

[0030] Compared with Example 1 (the process and conditions are the same as Example 1), Example 5 is different in that 0.102g EDTA in the impregnation solution is replaced by 0.127g CTAB, and the rest is exactly the same as Example 1; the prepared catalyst is recorded as Catalyst 6.

[0031] Example 6: Chelating agent and heteropolyacid coordinated metal molar ratio is different - 1:10

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

[0033] Example 7: Different molar ratios of chelating agent and heteropolyacid coordinated metal—1:40

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

[0035] Example 8: Different active component loadings—10 wt%

[0036] Example 8 is compared with Example 1 (the process and conditions are the same as Example 1), except that the impregnation solution contains 0.56g H3PW 12 O 40 ·24H2O and 0.034gEDTA, and the rest are exactly the same as in Example 1; the obtained catalyst is recorded as Catalyst 9, in which the content of heteropolyacid is 10wt% (the molar ratio of EDTA to W is 1:20).

[0037] Example 9: Different active component loadings—40 wt%

[0038] Example 9 is compared with Example 1 (process and conditions are the same as Example 1), except that the impregnation solution contains 3.33g H3PW 12 O 40 · 24H2O and 0.203g EDTA, and the rest is exactly the same as in Example 1; the obtained catalyst is recorded as catalyst 10, in which 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 1.67 g H3PW 12 O 40 ·24H2O was dissolved in 10mL deionized water to form an impregnation solution A, which was added dropwise to 5.0g of γ-Al2O3 carrier under constant stirring, aged at room temperature for 12h, dried at 120℃ for 12h, and calcined at 300℃ in nitrogen (flow rate 50mL / min) for 4h to obtain a catalyst precursor; (2) 0.102g of EDTA was weighed and dissolved in 10mL deionized water to form an impregnation solution B, which was added dropwise to the catalyst precursor obtained in step (1) under constant stirring, aged at room temperature for 12h, dried at 120℃ for 12h, and calcined at 300℃ in nitrogen (flow rate 50mL / min) for 4h to obtain a catalyst, which was recorded as catalyst 11. The remaining processes and conditions were exactly the same as those in Example 1.

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

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

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

[0044] Compared with Example 1 (the process and conditions are the same as Example 1), Example 12 is different in that the carrier is SiO2, the aging time is 8 hours, the drying temperature is 110°C, and the drying time is 18 hours. The rest is exactly the same as Example 1; the prepared catalyst is recorded as Catalyst 13.

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

[0046] Compared with Example 1 (the process and conditions are the same as Example 1), Example 13 is different in that the carrier is TiO2, the aging time is 8 hours, the drying temperature is 130°C, and the drying time is 6 hours. The rest is exactly the same as Example 1; the prepared catalyst is recorded as Catalyst 14.

[0047] Example 14: Calcination temperature, time and atmosphere are different

[0048] Compared with Example 1 (the process and conditions are the same as Example 1), Example 14 is different in that the carrier is CeO2, the calcination temperature is 400°C, the calcination time is 2h, the calcination atmosphere is argon, and the rest is exactly the same as Example 1; the prepared catalyst is recorded as Catalyst 15.

[0049] Example 15: Calcination temperature and time are different

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

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

[0052] Example 16 is compared with Example 1 (process and conditions are the same as Example 1), except that the impregnation solution contains 1.67g H4SiW 12 O 40 ·24H2O and 0.102g EDTA, and the rest is exactly the same as in Example 1; the prepared catalyst is recorded as Catalyst 17.

[0053] Comparative Example 2

[0054] Compared with Example 16 (the process and conditions are the same as Example 1), Comparative Example 2 is different in that the impregnation solution does not contain EDTA, and the rest is exactly the same as Example 16; the prepared catalyst is recorded as Catalyst 18.

[0055] Example 17: Different types of active ingredients - phosphomolybdic acid

[0056] Example 17 is compared with Example 1 (process and conditions are the same as Example 1), except that the impregnation solution contains 1.67g H3PMo 12 O 40 ·24H2O and 0.16g EDTA, and the rest is exactly the same as in Example 1; the obtained catalyst is recorded as Catalyst 19.

[0057] Comparative Example 3

[0058] Comparative Example 3 is compared with Example 17 (the process and conditions are the same as Example 1), except that the impregnation solution does not contain EDTA, and the rest is exactly the same as Example 17; the prepared catalyst is recorded as Catalyst 20.

[0059] The following table lists the reaction evaluation results of the catalyst prepared by the method of the present invention:

[0060]

[0061] It can be seen from Example 1 and Comparative Example 1, Example 16 and Comparative Example 2, and Example 17 and Comparative Example 3 that the addition of a chelating agent is beneficial to improving the stability of ethanol dehydration to ethylene; it can be seen from Examples 1 and 2-5 that citric acid has the best effect; it can be seen from Examples 1, 10, and 11 that the best effect is achieved when the chelating agent and heteropolyacid are co-impregnated; it can be seen from Examples 1, 6-9, and 12-15 that the preparation conditions of Example 1 are the best.

Claims

1. A high-stability solid acid catalyst for dehydrating bioethanol to produce bioethylene, comprising a main catalyst, a co-catalyst and a carrier, wherein the main catalyst is a heteropoly acid with a content of 5-50wt%, preferably 10-40wt%; the co-catalyst is a chelating agent, and the molar ratio of the chelating agent to the heteropoly acid coordinated metal is 1 / 5-1 / 80, preferably 1 / 10-1 / 40; and the remaining components are carriers.

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

3. The method according to claim 1, characterized in that: In the catalyst, the main catalyst is one or more of silicotungstic acid (coordinating metal is tungsten), phosphotungstic acid (coordinating metal is tungsten) and phosphomolybdic acid (coordinating metal is molybdenum), and the content is 5-50wt%, preferably 10-40wt%.

4. The method according to claim 1, characterized in that: In the catalyst, the co-catalyst is a chelating agent, including one or more of ethylenediaminetetraacetic acid (EDTA), aminotriacetic acid (NTA), dihydroxyethylglycine (DEG), citric acid (CA) and hexadecyltrimethylammonium bromide (CTAB), and the molar ratio of the chelating agent to the heteropolyacid coordinated metal is 1:5-1:80, preferably 1:10-1:

40.

5. The method according to claim 1, characterized in that: The catalyst is prepared by an equal volume impregnation method. The impregnation method of the main catalyst and the co-catalyst is (1) impregnating the heteropoly acid first and then the chelating agent, or (2) impregnating the heteropoly acid and the chelating agent together, or (3) impregnating the chelating agent first and then the heteropoly acid.

6. The method according to claim 5, characterized in that: In method (1), the heteropolyacid aqueous solution is first impregnated onto the carrier, aged for 8-16 hours, dried at 110-130°C for 6-18 hours, and calcined at 200-400°C in an inert atmosphere (such as nitrogen and / or argon) for 2-8 hours to obtain a catalyst precursor; then the chelating agent aqueous solution is impregnated onto the catalyst precursor, aged for 8-16 hours, dried at 110-130°C for 6-18 hours, and calcined at 200-400°C in an inert atmosphere (such as nitrogen and / or argon) for 2-8 hours to obtain a catalyst.

7. The method according to claim 5, characterized in that: In method (2), a mixed solution of a chelating agent and a heteropolyacid is impregnated onto a carrier, aged for 8-16 hours, dried at 110-130° C. for 6-18 hours, and calcined at 200-400° C. for 2-8 hours in an inert atmosphere (eg, nitrogen and / or argon) to obtain a catalyst.

8. The method according to claim 5, characterized in that: In method (3), the chelating agent aqueous solution is first impregnated onto the carrier, aged for 8-16 hours, dried at 110-130°C for 6-18 hours, and calcined at 200-400°C in an inert atmosphere (such as nitrogen and / or argon) for 2-8 hours to obtain a catalyst precursor; then the heteropolyacid aqueous solution is impregnated onto the above catalyst precursor, aged for 8-16 hours, dried at 110-130°C for 6-18 hours, and calcined at 200-400°C in an inert atmosphere (such as nitrogen and / or argon) for 2-8 hours to obtain a catalyst.

9. Use of a modified heteropolyacid catalyst in catalyzing the dehydration of bioethanol to produce ethylene, characterized in that: The catalyst used is prepared by any preparation method described in claims 1-8.

10. The method according to claim 9, characterized in that: A fixed bed reactor is used, the raw material is bioethanol, the reaction temperature is 200-350°C, preferably 220-280°C; the reaction pressure is 0.1-2MPa, preferably 0.5-1.5MPa; based on ethanol, the mass space velocity is 0.5-20h -1 , preferably 1-10h -1 .

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