A method for regenerating a supported heteropolyacid catalyst

Abstract

The present invention relates to a method for regenerating a deactivated supported heteropolyacid catalyst. This method utilizes a fixed-bed reactor to introduce an oxidizing gas and water vapor for heat treatment, thereby regenerating the catalyst in situ. The introduced oxidizing gas, at high temperature, restores the valence state of the reduced coordinated metals in the deactivated heteropolyacid and removes carbon deposits on the surface of the heteropolyacid catalyst. The water vapor also facilitates the restoration of the #imgabs0# acid centers on the catalyst surface. When the regenerated catalyst is used in a bioethanol dehydration reaction, its catalytic performance is restored. This regeneration method enables in-situ treatment, operates under mild reaction conditions, does not destroy the Keggin structure of the heteropolyacid catalyst, and provides a stable, controllable, and reproducible process.

Description

Technical Field

[0001] The present invention relates to a method for regenerating a supported heteropolyacid catalyst, in particular to a method for regenerating a supported heteropolyacid catalyst used for catalyzing the dehydration of bioethanol to prepare ethylene. Background Art

[0002] Ethylene can be used to synthesize important chemical products such as polyethylene, ethylene oxide, polyvinyl chloride, PET, and ethylbenzene, and is a key indicator of a country's petrochemical industry capabilities. Ethanol can be produced from biomass, industrial waste gas, coal, and solid waste through fermentation or thermochemical conversion processes. Ethanol dehydration to ethylene technology offers flexible small- to medium-scale production of high-purity ethylene. Its simple reaction process, easy product separation, and environmental friendliness allow for the partial or complete replacement of petroleum-based ethylene, making it a valuable economic and strategic energy resource. The key lies in the development of efficient catalysts. Heterogeneous catalysts used for ethanol dehydration to ethylene primarily include activated alumina, molecular sieves, and heteropolyacids. Activated alumina offers high mechanical strength and selectivity, but it also has high reaction temperatures, low space velocities, high specific energy consumption, and low equipment utilization. Ethanol dehydration catalyzed by molecular sieves offers lower reaction temperatures, high ethanol conversion rates, and high ethylene selectivity. However, the process requires a carrier gas and suffers from poor catalyst stability, limiting further industrial application. Patents CN 105709822 A and CN 106944139 A disclose a method for producing ethylene by dehydrating ethanol using a heteropolyacid ammonium salt as a catalyst. However, when using these unmodified catalysts for ethanol dehydration to produce ethylene, their activity decreases over time due to reduction of coordinating atoms or carbon deposition on the surface.

[0003] Patent US4471062 discloses a method for regenerating a deactivated heteropolyacid catalyst, which comprises first purging with an inert gas and then introducing a nitrogen oxide compound at 100-400°C to treat the catalyst; Patent CN1451478A discloses a method in which a mixed gas consisting of molecular oxygen, water vapor and nitrogen is introduced every six months or one year to activate the catalyst online at 290-400°C; Patent US4814305 reports a method in which a deactivated catalyst is dispersed in water, treated with ammonia water, dried, treated with pyridine, and then dried and calcined to obtain a regenerated catalyst; Patent CN10554593A first treats the deactivated catalyst at 350°C, then mixes it with water, nitrate and ammonium ions, and then heat-treats it at 100°C. After drying and calcining twice, the regenerated catalyst is obtained; Patent CN100490975C first mixes the deactivated catalyst with water, nitrate and ammonium ions, treats it at 70°C for 5 hours, and then dries, shapes and calcines it to obtain a regenerated catalyst. These traditional methods are cumbersome and the regenerated catalysts cannot show satisfactory activity recovery. Therefore, it is necessary to provide a new method for regenerating supported heteropolyacid catalysts to solve the existing problems.

[0004] The present invention has developed a method for regenerating a deactivated supported heteropolyacid catalyst. The method uses a fixed bed reactor, introduces a mixture of oxidizing gas and water vapor, and performs high-temperature treatment to regenerate the catalyst in situ. The introduced oxidizing gas can not only restore the valence state of the reduced coordinated metal in the deactivated heteropolyacid, but also remove carbon deposits on the surface of the heteropolyacid catalyst; the high-temperature water vapor is conducive to restoring the catalyst surface. Acid centers. When the regenerated catalyst is used in the bioethanol dehydration reaction, catalytic performance is restored. This regeneration method enables in-situ treatment, mild reaction conditions, and does not destroy the Keggin structure of the heteropolyacid catalyst. The process is stable, controllable, and reproducible. Summary of the Invention

[0005] The problem to be solved by the present invention is to provide a method for regenerating a supported heteropolyacid catalyst with in-situ treatment, mild reaction conditions, controllable preparation process and simple steps. The regenerated catalyst recovers its catalytic activity in the ethanol dehydration reaction and has broad application prospects.

[0006] The technical solution is:

[0007] The method for regenerating a supported heteropolyacid catalyst of the present invention adopts a fixed bed reactor. After the system temperature is adjusted to the required treatment temperature, the system pressure is reduced to normal pressure, and oxidizing gas and water vapor are introduced for heat treatment to regenerate the catalyst in situ.

[0008] Preferably, the oxidizing gas introduced is one or more of oxygen, air or carbon dioxide, with a flow rate of 10-50 mL / min; the heat treatment temperature is 250-350° C.; and the heat treatment time is 4-12 h.

[0009] The flow rate of water vapor is 10-50 mL / min; the temperature of heat treatment is 150-200° C.; and the heat treatment time is 2-8 h.

[0010] In the deactivated supported heteropolyacid catalyst, the active component is one of silicotungstic acid, phosphotungstic acid or phosphomolybdic acid; and the carrier is silicon oxide, aluminum oxide, titanium oxide or silicon-aluminum composite oxide.

[0011] The regenerated catalyst is used to carry out the dehydration of bioethanol to ethylene. A fixed bed reactor is used, the raw material is bioethanol, the reaction temperature is 240°C, the reaction pressure is 1.0 MPa, and the mass space velocity is 10 h -1 .

[0012] Beneficial technical effects

[0013] 1. The present invention adopts a fixed bed reactor, uses oxidizing gas to restore the valence state of coordinated atoms, removes carbon deposits on the surface of supported heteropolyacids, and uses water vapor to restore the surface of the catalyst. Acid center to achieve catalyst regeneration;

[0014] 2. The present invention has mild operating conditions, low temperature, does not destroy the Keggin structure of the heteropoly acid, the reaction process is simple, controllable and easy to operate, and can realize in-situ treatment of the catalyst, which has broad application prospects. DETAILED DESCRIPTION

[0015] In order to further illustrate the present invention in detail, several specific implementation cases are given below, but the present invention is not limited to these embodiments.

[0016] Reference Example 1

[0017] (1) Preparation of fresh silica-supported silicotungstic acid catalyst: 10 g silica support was weighed and added to 10 mL of 4.29 g H4SiW 12 O 40 The catalyst was prepared by aging in a 24H2O aqueous solution at room temperature for 12 h, drying at 120°C for 12 h, and calcining in air at 250°C for 4 h to obtain a catalyst, designated as catalyst 1. The content of the active component, silicotungstic acid, was 30 wt%.

[0018] (2) Catalyst evaluation: 1.0 g of catalyst 1 was loaded into 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 were calculated based on the comprehensive reaction results of the gas-liquid phase.

[0019] Reference Example 2:

[0020] Catalyst stabilization experiment: The fresh catalyst prepared in Reference Example 1 was used in the bioethanol dehydration reaction. After 800 h of reaction, a deactivated catalyst was obtained, which was recorded as Catalyst 2.

[0021] Example 1

[0022] (1) Catalyst regeneration: According to the evaluation conditions in Reference Example 1, 1.0 g of the fresh catalyst prepared in Reference Example 1 was used. After 800 h of reaction, a deactivated catalyst (Catalyst 2 of Reference Example 2) was obtained. The temperature was adjusted to 300°C, the system pressure was reduced to normal pressure, and carbon dioxide (at a flow rate of 30 mL / min) was introduced for 8 h. After that, the temperature was lowered to 180°C and water vapor (at a flow rate of 30 mL / min) was introduced for 4 h to obtain a regenerated catalyst, which was recorded as Catalyst 3.

[0023] (2) Catalyst evaluation: The reaction conditions and data processing were the same as those in Reference Example 1.

[0024] Example 2: Adjusting gas type and flow rate

[0025] Compared with Example 1, Example 2 differs in that the oxidizing gas introduced is air at a flow rate of 50 mL / min, and the rest is exactly the same as Example 1; the prepared catalyst is recorded as Catalyst 4.

[0026] Example 3: Adjusting gas type and flow rate

[0027] Compared with Example 1, Example 3 differs in that the oxidizing gas introduced is oxygen and the flow rate is 10 mL / min. The rest is exactly the same as Example 1; the prepared catalyst is recorded as Catalyst 5.

[0028] Example 4: Adjusting the carbon dioxide treatment temperature and time

[0029] Compared with Example 1, Example 4 differs in that the heat treatment temperature of carbon dioxide is 250° C. and the heat treatment time is 12 h. The rest is exactly the same as Example 1. The obtained catalyst is recorded as Catalyst 6.

[0030] Example 5: Adjusting the carbon dioxide treatment temperature and time

[0031] Compared with Example 1, Example 5 differs in that the heat treatment temperature of carbon dioxide is 350° C. and the heat treatment time is 4 h. The rest is exactly the same as Example 1. The prepared catalyst is recorded as Catalyst 7.

[0032] Example 6: Adjusting the water vapor heat treatment temperature, time and gas flow rate

[0033] Compared with Example 1, Example 6 differs in that the water vapor flow rate is 10 mL / min and the heat treatment time is 8 h. The rest is exactly the same as Example 1; the prepared catalyst is recorded as Catalyst 8.

[0034] Example 7: Adjusting the water vapor heat treatment temperature, time and gas flow rate

[0035] Compared with Example 1, Example 7 differs in that the heat treatment temperature is 150° C. and the heat treatment time is 8 h. The rest is exactly the same as Example 1. The obtained catalyst is recorded as Catalyst 9.

[0036] Example 8: Adjusting the water vapor heat treatment temperature, time and gas flow rate

[0037] Compared with Example 1, Example 8 differs in that the heat treatment temperature is 200° C. and the gas flow rate is 10 mL / min. The rest is exactly the same as Example 1; the prepared catalyst is recorded as Catalyst 10.

[0038] Example 9: Adjusting the water vapor heat treatment temperature, time and gas flow rate

[0039] Compared with Example 1, Example 9 differs in that the heat treatment temperature is 150° C. and the gas flow rate is 50 mL / min. The rest is exactly the same as Example 1; the prepared catalyst is recorded as Catalyst 11.

[0040] Example 10: Adjusting the steam heat treatment temperature, time and gas flow rate

[0041] Compared with Example 1, Example 10 differs in that the heat treatment temperature is 200° C. and the heat treatment time is 8 h. The rest is exactly the same as Example 1. The obtained catalyst is recorded as Catalyst 12.

[0042] Example 11: Adjusting the steam heat treatment temperature, time and gas flow rate

[0043] Compared with Example 1, Example 11 differs in that the gas flow rate is 50 mL / min and the heat treatment time is 8 h. The rest is exactly the same as Example 1; the prepared catalyst is recorded as Catalyst 13.

[0044] Reference Example 3

[0045] Compared with Reference Example 1, Reference Example 3 differs in that the carrier is a silicon-aluminum composite oxide (silicon content is 30 wt%), and the rest is exactly the same as Reference Example 1; the prepared catalyst is recorded as Catalyst 14.

[0046] Reference Example 4

[0047] Catalyst stabilization experiment: The fresh catalyst prepared in Reference Example 3 was used in the bioethanol dehydration reaction. After 800 h of reaction, a deactivated catalyst was obtained, which was recorded as Catalyst 15.

[0048] Example 12

[0049] Compared with Example 1, Example 12 is different in that the treatment object is the deactivated catalyst 15, and the rest is exactly the same as Example 1; the prepared catalyst is recorded as catalyst 16.

[0050] Reference Example 5

[0051] Compared with Reference Example 1, Reference Example 5 differs in that the active component is phosphotungstic acid and the carrier is alumina. The rest is exactly the same as Reference Example 1; the prepared catalyst is recorded as Catalyst 17.

[0052] Reference Example 6

[0053] Catalyst stabilization experiment: The fresh catalyst prepared in Reference Example 5 was used in the bioethanol dehydration reaction. After 800 h of reaction, a deactivated catalyst was obtained, which was recorded as Catalyst 18.

[0054] Example 13

[0055] Compared with Example 1, Example 12 is different in that the treatment object is the deactivated catalyst 18, and the rest is exactly the same as Example 1; the prepared catalyst is recorded as catalyst 19.

[0056] Reference Example 7

[0057] Compared with Reference Example 1, Reference Example 7 differs in that the active component is phosphomolybdic acid and the carrier is titanium oxide. The rest is exactly the same as Reference Example 1; the prepared catalyst is recorded as Catalyst 20.

[0058] Reference Example 8

[0059] Catalyst stabilization experiment: The fresh catalyst prepared in Reference Example 7 was used in the bioethanol dehydration reaction. After 800 h of reaction, a deactivated catalyst was obtained, which was recorded as Catalyst 21.

[0060] Example 14

[0061] Compared with Example 1, Example 12 differs in that the treatment object is the deactivated catalyst 21, and the rest is exactly the same as Example 1; the prepared catalyst is recorded as catalyst 22.

[0062] The following table lists the reaction evaluation results of the catalyst prepared by the method of the present invention

[0063] catalyst Example Ethanol conversion rate / % Ethylene selectivity / % 1 Reference Example 1 87.1 58.2 2 Reference Example 2 71.9 33.4 3 Example 1 87.0 58.1 4 Example 2 83.8 51.8 5 Example 3 76.1 42.1 6 Example 4 84.1 51.9 7 Example 5 86.8 56.3 8 Example 6 85.1 56.1 9 Example 7 80.2 45.5 10 Example 8 80.9 47.9 11 Example 9 80.6 48.0 12 Example 10 81.5 50.8 13 Example 11 85.8 56.5 14 Reference Example 3 67.8 37.9 15 Reference Example 4 52.2 20.3 16 Example 12 66.9 37.6 17 Reference Example 5 60.8 35.7 18 Reference Example 6 45.6 19.1 19 Example 13 60.6 35.5 20 Reference Example 7 62.2 36.8 21 Reference Example 8 46.4 20.1 22 Example 14 61.9 36.6

[0064] It can be seen from Example 1 and Reference Examples 1 and 2 that the activity of the catalyst can be restored after regeneration by heat treatment with oxidizing gas and water vapor, respectively; it can be seen from Examples 1-3 that carbon dioxide is more effective than air and oxygen; it can be seen from Examples 1 and 4-11 that the conditions of Example 1 are optimal, and excessively high / low gas flow rate, treatment temperature and treatment time are not conducive to the complete recovery of catalyst performance; it can be seen from Examples 12-14 and Reference Examples 3-8 that the regeneration method is also applicable to silicotungstic acid, phosphotungstic acid and phosphomolybdic acid loaded on silicon-aluminum composite oxides, alumina and titanium oxide, and the catalyst performance is restored after regeneration.

Claims

1. A method for regenerating a deactivated supported heteropolyacid catalyst and its use in a bioethanol dehydration reaction, characterized in that: The regeneration method uses a fixed bed reactor. After the system temperature is adjusted to the required treatment temperature, the system pressure is reduced to normal pressure, and carbon dioxide and water vapor are introduced in sequence to regenerate the catalyst in situ. The flow rate of the introduced carbon dioxide is 5-100 mL / min relative to 1.0 g of the supported heteropolyacid catalyst; the heat treatment temperature is 200-400°C; the heat treatment time is 4-16 h; the flow rate of the water vapor is 10-50 mL / min relative to 1.0 g of the supported heteropolyacid catalyst, excluding 10 mL / min and 50 mL / min; the heat treatment temperature is 150-200°C, excluding 150°C and 200°C; the heat treatment time is 2-8 h, excluding 2 h and 8 h; the active component in the deactivated supported heteropolyacid catalyst is one or more of silicotungstic acid, phosphotungstic acid or phosphomolybdic acid.

2. The use according to claim 1, characterized in that: The flow rate of the introduced carbon dioxide is 10-50 mL / min relative to 1.0 g of the supported heteropolyacid catalyst; the heat treatment temperature is 250-350° C.; and the heat treatment time is 8-12 h.

3. The use according to claim 1, characterized in that: The carrier is one or more of silicon oxide, aluminum oxide, titanium oxide or silicon-aluminum composite oxide; the content of the active component is 5-50wt%.

4. The use according to claim 1, characterized in that: A fixed bed reactor is used, the raw material is bioethanol, the reaction temperature is 200-350 ℃; the reaction pressure is 0.1-2 MPa; the mass space velocity is 0.5-20 h-1 in terms of ethanol. -1 .

5. The use according to claim 4, characterized in that: The reaction temperature is 220-280°C; the reaction pressure is 0.5-1.5 MPa.

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