Regeneration method of supported heteropolyacid catalyst

Abstract

The invention relates to a regeneration method of a supported heteropolyacid deactivated catalyst. According to the method, a fixed bed reactor is adopted, oxidizing gas and water vapor are introduced for heat treatment, and the catalyst is regenerated in situ. The introduced oxidizing gas can recover the valence state of the reduced coordination metal in the inactivated heteropolyacid at high temperature, and also can remove carbon deposition on the surface of the heteropolyacid catalyst; the water vapor is beneficial to recovery of # imgabs0 # acid center on the surface of the catalyst. When the regenerated catalyst is used for catalyzing the dehydration reaction of bioethanol, the catalytic performance is recovered. According to the regeneration method, in-situ treatment can be realized, the reaction condition is mild, the Keggin structure of the heteropolyacid catalyst is not damaged, the process is stable and controllable, and the repeatability is good.

Description

Technical Field

[0001] The invention relates to a method for regenerating a supported heteropolyacid catalyst, and in particular to a method for regenerating a supported heteropolyacid catalyst 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, ethylbenzene, etc., and is an important indicator of a country's petrochemical level. Ethanol can be produced by fermentation or thermochemical conversion of biomass, industrial waste gas, coal, solid waste, etc. The technology of ethanol dehydration to ethylene can flexibly produce small and medium-scale high-purity ethylene. The reaction process is simple, the reaction products are easy to separate, and it is environmentally friendly. It can partially or completely replace petroleum ethylene, which has important economic value and energy strategic significance. The key is to develop efficient catalysts. The multiphase catalysts used for ethanol dehydration to ethylene mainly include activated alumina, molecular sieves and heteropoly acids. Activated alumina has high mechanical strength and good selectivity, but the reaction temperature is high, the space velocity is low, the unit energy consumption is high, and the utilization rate of equipment is low. The molecular sieve-catalyzed ethanol dehydration reaction temperature is low, the ethanol conversion rate is high, and the ethylene selectivity is high, but the process requires the introduction of carrier gas, and there are still problems such as poor catalyst stability, which limits further industrial application. Patents CN 105709822 A and CN 106944139 A disclose a method for preparing ethylene by dehydrating ethanol using heteropolyacid ammonium salt as a catalyst. However, when the unmodified catalyst is used for preparing ethylene by dehydrating ethanol, the activity of the catalyst decreases as the reaction time increases due to the reduction of the coordinated atoms or the formation of carbon deposits on the surface.

[0003] Patent US4471062 discloses a method for regenerating a deactivated heteropolyacid catalyst, which first uses an inert gas to purge, and then introduces a nitrogen oxide compound to treat the catalyst at 100-400°C; Patent CN1451478A discloses a method, which introduces a mixed gas consisting of molecular oxygen, water vapor and nitrogen every six months or one year, and activates the catalyst online at 290-400°C; Patent US4814305 reports a method, which disperses the deactivated catalyst in water, adds ammonia water for treatment, adds pyridine for treatment after drying, and then obtains a regenerated catalyst after drying and roasting; 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, and obtains the regenerated catalyst after drying and roasting twice; Patent CN100490975C first mixes the deactivated catalyst with water, nitrate and ammonium ions, treats it at 70°C for 5h, and then obtains the regenerated catalyst through drying, molding and roasting. These traditional methods are complicated and the regenerated catalysts cannot show satisfactory activity recovery effects. 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 supported heteropoly acid deactivated catalyst. The method uses a fixed bed reactor, introduces a mixed gas of oxidizing gas and water vapor, and treats the catalyst in situ at high temperature. The introduced oxidizing gas can not only restore the valence state of the reduced coordinated metal in the deactivated heteropoly acid, but also remove the carbon deposits on the surface of the heteropoly acid catalyst; the high-temperature water vapor is conducive to restoring the catalyst surface. Acid center. When the regenerated catalyst is used in the bioethanol dehydration reaction, the catalytic performance is restored. The regeneration method can achieve in-situ treatment, mild reaction conditions, does not destroy the Keggin structure of the heteropolyacid catalyst, and the process is stable and controllable with good repeatability. 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 the catalytic activity of 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 respectively 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.; 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 heteropoly acid 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 reaction of dehydrating bioethanol to produce ethylene. A fixed bed reactor is used, the raw material is bioethanol, the reaction temperature is 240°C, the reaction pressure is 1.0MPa, and the mass space velocity is 10h in terms of ethanol. -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 heteropolyacids, and the reaction process is simple, controllable, and easy to operate. It can realize in-situ treatment of catalysts and has broad application prospects. DETAILED DESCRIPTION

[0015] 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.

[0016] Reference Example 1

[0017] (1) Preparation of fresh silica-supported silicotungstic acid catalyst: 10 g silica carrier was weighed and added to 10 mL of 4.29 g H4SiW 12 O 40 ·In 24H2O aqueous solution, the catalyst was aged at room temperature for 12 h, dried at 120°C for 12 h, and calcined in air at 250°C for 4 h to obtain a catalyst, which was 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, and the conversion rate of ethanol and the selectivity of ethylene were calculated based on the comprehensive gas-liquid reaction results.

[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 reacting for 800 h, 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, carbon dioxide (flow rate of 30 mL / min) was introduced for 8 h, and then the temperature was reduced to 180 °C and water vapor (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 is different in that the oxidizing gas introduced is air with 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 is different 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 is different 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 prepared catalyst is recorded as Catalyst 6.

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

[0031] Compared with Example 1, Example 5 is different 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 steam 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, the heat treatment time is 8 h, and the rest is exactly the same as Example 1; the prepared catalyst is recorded as Catalyst 8.

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

[0035] The difference between Example 7 and Example 1 is 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 steam heat treatment temperature, time and gas flow rate

[0037] Compared with Example 1, Example 8 is different 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 steam heat treatment temperature, time and gas flow rate

[0039] Compared with Example 1, Example 9 is different 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 is different 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 prepared 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 is different in that the gas flow rate is 50 mL / min, the heat treatment time is 8 h, and 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, and 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] Embodiment 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, and 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] Embodiment 14

[0061] Compared with Example 1, Example 12 is different 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 Embodiment 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 Embodiment 13 60.6 35.5 20 Reference Example 7 62.2 36.8 21 Reference Example 8 46.4 20.1 22 Embodiment 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 rates, treatment temperatures and treatment times 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 with 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, characterized in that: A fixed bed reactor is used. 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 in sequence to regenerate the catalyst in situ.

2. The method according to claim 1, characterized in that: The oxidizing gas introduced is one or more of oxygen, air or carbon dioxide, and the flow rate is 5-100 mL / min, preferably 10-50 mL / min, relative to 1.0 g of the supported heteropolyacid catalyst; the heat treatment temperature is 200-400° C., preferably 250-350° C.; the heat treatment time is 4-16 h, preferably 8-12 h.

3. The method according to claim 1 or 2, characterized in that: Relative to 1.0 g of supported heteropolyacid catalyst, the flow rate of water vapor is 5-100 mL / min, preferably 10-50 mL / min; the heat treatment temperature is 100-250° C., preferably 150-200° C.; the heat treatment time is 1-12 h, preferably 2-8 h.

4. The method according to claim 1, characterized in that: In the deactivated supported heteropolyacid catalyst, the active component is one or more of silicotungstic acid, phosphotungstic acid or phosphomolybdic acid; 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%.

5. Use of a regenerated heteropolyacid catalyst in a bioethanol dehydration reaction, characterized in that: The catalyst used is obtained by the regeneration method described in any one of claims 1-4.

6. The use according to claim 5, 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 .

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