Method for preparing tetrahydropyrrole by catalyzing tetrahydrofuran amination through rare earth metal ion doped gamma-aluminum oxide

Abstract

The method for preparing tetrahydropyrrole by catalyzing tetrahydrofuran amination through rare earth metal ion doped gamma-aluminum oxide comprises the following steps: S1, adding gamma-aluminum oxide into a rare earth chloride aqueous solution, fully mixing, and soaking at 80 DEG C for 5-10 hours; removing moisture, washing the gamma-aluminum oxide with deionized water, and roasting to obtain the rare earth metal ion doped gamma-aluminum oxide catalyst. And S2, loading the catalyst obtained in the step S1 into a fixed bed reactor, heating to 250-450 DEG C, and continuously introducing tetrahydrofuran and ammonia gas to obtain tetrahydropyrrole. The catalyst disclosed by the invention has relatively high mechanical strength and catalytic activity, and the yield and selectivity of tetrahydropyrrole are relatively high; in-situ activation and regeneration can be carried out, the use cost is low, and the industrial value is very high.

Description

Technical Field

[0001] The invention relates to the field of chemical raw material synthesis, in particular to a method for preparing tetrahydropyrrole by catalyzing amination of tetrahydrofuran by rare earth metal ion-doped gamma-alumina. Background Art

[0002] Tetrahydropyrrole is a cyclic secondary amine, which is a colorless or light yellow transparent liquid with a special smell. It turns yellow when exposed to light or moist air and is easily soluble in water and ethanol. Tetrahydropyrrole naturally exists in the leaves of plants such as tobacco and carrots, and is widely used in medicine, pesticides, organic synthesis, coatings and daily chemicals. At present, the synthesis method of tetrahydropyrrole mainly uses 1,4-butanediol, 1,4-succinonitrile, 1,4-butanediamine and tetrahydrofuran as raw materials for preparation. Among them, the route of preparing tetrahydropyrrole using tetrahydrofuran as raw material has the advantages of simple reaction process, low equipment investment, low raw material cost and high atomic utilization rate, showing a very high research value.

[0003] From the perspective of reaction mechanism, no matter which compound is used as raw material, the preparation of tetrahydropyrrole belongs to the category of Lewis acid catalytic reaction mechanism. Therefore, for a long time, the industry has been continuously screening and optimizing catalysts from the perspective of acidic carriers and corresponding loaded metal ions in order to obtain higher catalytic activity and selectivity. 2+ ,Co 2+ Catalysts containing metal ions have been shown to be useful for catalyzing the reaction of tetrahydrofuran to prepare tetrahydropyrrole (US Pat. No. 2,525,584; Applied Chemical Industry, 2007, 36, 913-915). However, all of the reported catalysts have the disadvantages of low yield or low selectivity of the prepared tetrahydropyrrole.

[0004] CN 112521346A reports an acidic zeolite molecular sieve catalyst HZSM-5, which can continuously catalyze the amination of tetrahydrofuran and successfully realize the synthesis of tetrahydropyrrole. The method has a high conversion rate and a total yield of 23% to 80%. CN101948450A prepares a Cu-ZSM-5 catalyst by loading copper nitrate on a ZSM-5 molecular sieve, which can catalyze the continuous amination of tetrahydrofuran to obtain the desired tetrahydropyrrole under relatively mild conditions. Although both of the above two schemes have certain application prospects, the ZSM-5 molecular sieve and catalyst used therein have disadvantages such as low mechanical compressive strength and poor selectivity. Therefore, it is crucial to develop a catalyst that is more suitable for the catalytic amination of tetrahydrofuran to prepare tetrahydropyrrole.

[0005] On the other hand, the rare earth industry is a dominant industry in my country. Not only are rare earth resources abundant, but the resources are widely distributed and the minerals are complete. At the same time, my country's rare earth industry chain and overall processing technology are also leading the world. Rare earth metal elements are ranked in the IIIB group of the periodic table, referred to as Ln. They include scandium with atomic number 21 and yttrium with atomic number 39, as well as lanthanide elements (from lanthanum with atomic number 57 to lutetium with atomic number 71), a total of 17 elements. The ionic radius of rare earth elements is relatively large, and their coordination number is much higher than that of general transition metals. They often show higher activity and selectivity in catalytic reactions. Secondly, rare earth metal ions have strong Lewis acidity, which is very suitable for a series of reactions with acidic catalytic mechanisms. Strong Lewis acidity is also conducive to the careful and precise control of the acidity and catalytic performance of the catalyst by changing the amount of rare earth metal ion doping. Summary of the invention

[0006] The present invention aims to solve the existing problems and provide a method for preparing tetrahydropyrrole by catalyzing amination of tetrahydrofuran by rare earth metal ion-doped γ-alumina.

[0007] In order to achieve the above object, the technical solution adopted by the present invention comprises the following steps:

[0008] S1 Preparation of catalyst: Add γ-alumina (γ-Al2O3) to a rare earth chloride aqueous solution, mix thoroughly and soak at 80°C for 5 to 10 hours; remove moisture and wash the γ-alumina (γ-Al2O3) with a small amount of deionized water, and calcine to obtain a rare earth metal ion-doped γ-alumina catalyst Ln-γ-Al2O3; S2 Synthesis of tetrahydropyrrole: The rare earth metal ion-doped γ-alumina catalyst Ln-γ-Al2O3 obtained in S1 is loaded into a fixed bed reactor, heated to 250 to 450°C, and continuously introduced tetrahydrofuran and ammonia to obtain tetrahydropyrrole.

[0009] Preferably, in S1, the rare earth chloride is LaCl3(H2O) x ,CeCl3(H2O) x ,PrCl3(H2O) x ,NdCl3(H2O) x ,SmCl3(H2O) x ,EuCl3(H2O) x ,GdCl3(H2O) x ,ErCl3(H2O) x ,TmCl3(H2O) x and YCl3(H2O) x A combination of one or more of .

[0010] Preferably, in S1, the calcination temperature is 350-750° C. or 450-550° C.; and the calcination time is 2-8 hours or 4-6 hours.

[0011] Preferably, in S1, the rare earth chloride LnCl3(H2O) x The mass ratio of γ-alumina γ-Al2O3 is 0.1% to 25% or 3.5 to 6.5%.

[0012] Preferably, in S2, the heating temperature during the synthesis of tetrahydropyrrole is 310-350°C.

[0013] Preferably, in S2, the molar ratio of ammonia to tetrahydrofuran is 1:1 to 20:1 or 4:1 to 8:1.

[0014] Preferably, in S2, after the crude product is obtained by reaction, it is further condensed, dried and distilled to obtain the final product of tetrahydropyrrole.

[0015] Compared with the prior art, the invention prepares a rare earth metal ion-doped γ-alumina catalyst, and continuously catalyzes amination of tetrahydrofuran in a fixed bed reactor to finally synthesize tetrahydropyrrole; the catalyst of the invention has high mechanical strength and catalytic activity, high yield and selectivity of tetrahydropyrrole; and can be activated and regenerated in situ, has low use cost, and has high industrial value. DETAILED DESCRIPTION

[0016] The above scheme is further described below in conjunction with specific examples. The present invention provides a method for preparing tetrahydropyrrole by amination of tetrahydrofuran catalyzed by rare earth metal ion-doped γ-alumina, which specifically includes the following steps:

[0017] S1. Preparation of catalyst: prepare a rare earth chloride aqueous solution of a certain concentration, add γ-alumina (γ-Al2O3), mix thoroughly and soak at 80°C for 5 to 10 hours; remove water and wash the γ-alumina (γ-Al2O3) with a small amount of deionized water, and obtain a rare earth metal ion-doped γ-Al2O3 catalyst (Ln-γ-Al2O3) by calcination;

[0018] S2 synthesis of tetrahydropyrrole: the rare earth metal ion-doped γ-alumina catalyst Ln-γ-Al2O3 catalyst obtained in S1 is loaded into a fixed bed reactor, heated to a set temperature, and tetrahydrofuran and ammonia are continuously introduced to obtain a crude product; and then the desired tetrahydropyrrole product is obtained through subsequent operations such as condensation, drying and distillation.

[0019] Further, the rare earth chloride is LaCl3(H2O) x ,CeCl3(H2O) x,PrCl3(H2O) x ,NdCl3(H2O) x ,SmCl3(H2O) x ,EuCl3(H2O) x ,GdCl3(H2O) x ,ErCl3(H2O) x ,TmCl3(H2O) x and YCl3(H2O) x One or more of the following, especially preferably LaCl3(H2O) x .

[0020] Furthermore, the calcination temperature during the preparation of the catalyst in S1 is 350-750° C., preferably 450-550° C., and the calcination time is 2-8 hours, preferably 4-6 hours.

[0021] Furthermore, doping with rare earth metal chloride (LnCl3(H2O) x ) and γ-Al2O3 in a mass ratio of 0.1% to 25%, preferably 3.5 to 6.5%.

[0022] Further, the reaction temperature in the tetrahydropyrrole synthesis process in S2 is in the range of 250 to 450° C., preferably 310 to 350° C. The molar ratio of ammonia to tetrahydrofuran is 1:1 to 20:1, preferably 4:1 to 8:1. Preferred embodiments of the present invention are as follows:

[0023] Embodiment 1:

[0024] 2.0g LaCl3(H2O) x Dissolve in 100 mL of water, add 48 g of γ-Al2O3 powder, stir and soak at 80°C for 5 hours, and then slowly evaporate the water. Wash the γ-Al2O3 powder with 10 mL of deionized water and fully dry it at 120°C. Burn the solid at 500°C under nitrogen for 5 hours to obtain the desired La-γ-Al2O3 catalyst.

[0025] Subsequently, the required amount of La-γ-Al2O3 was placed in a fixed bed reactor (14 mm*1100 mm), nitrogen was introduced, and the set temperature was raised to 320°C. After reaching the set temperature, the metering pump was turned on and tetrahydrofuran (liquid space velocity was 0.4 h -1 ) and ammonia, the molar ratio of ammonia to tetrahydrofuran is controlled at 6: 1. The mixture after the reaction is condensed to obtain a crude tetrahydropyrrole.

[0026] The crude tetrahydropyrrole product is successively dried with NaOH and molecular sieves and then distilled to obtain a pure product with a gas phase purity of 98.6% (the yield based on tetrahydrofuran is 88.5%).

[0027] Embodiment 2:

[0028] 2.0g LaCl3(H2O) x Dissolve in 100 mL of water, add 48 g of γ-Al2O3 powder, stir and soak at 80°C for 5 hours, and then slowly evaporate the water. Wash the γ-Al2O3 powder with 10 mL of deionized water and fully dry it at 120°C. Burn the solid at 500°C under nitrogen for 5 hours to obtain the desired La-γ-Al2O3 catalyst.

[0029] Subsequently, the required amount of La-γ-Al2O3 was placed in a fixed bed reactor (14 mm*1100 mm), nitrogen was introduced, and the set temperature was raised to 320°C. After reaching the set temperature, the metering pump was turned on and tetrahydrofuran (liquid space velocity was 0.4 h -1 ) and ammonia, the molar ratio of ammonia to tetrahydrofuran is controlled at 8:1. The reaction mixture is condensed to obtain a crude tetrahydropyrrole.

[0030] The crude tetrahydropyrrole product is successively dried with NaOH and molecular sieves and then distilled to obtain a pure product with a gas phase purity of 99.0% (the yield based on tetrahydrofuran is 85.9%).

[0031] Embodiment 3:

[0032] 0.7g LaCl3(H2O) x Dissolve in 100 mL of water, add 49.3 g of γ-Al2O3 powder, stir and soak at 80°C for 5 hours, and then slowly evaporate the water. Wash the γ-Al2O3 powder with 10 mL of deionized water and fully dry it at 120°C. Burn the solid at 520°C under nitrogen for 5 hours to obtain the desired La-γ-Al2O3 catalyst.

[0033] Subsequently, the required amount of La-γ-Al2O3 was placed in a fixed bed reactor (14 mm*1100 mm), nitrogen was introduced, and the set temperature was raised to 320°C. After reaching the set temperature, the metering pump was turned on and tetrahydrofuran (liquid space velocity was 0.4 h -1 ) and ammonia, the molar ratio of ammonia to tetrahydrofuran is controlled at 6: 1. The mixture after the reaction is condensed to obtain a crude tetrahydropyrrole.

[0034] The crude tetrahydropyrrole product is successively dried with NaOH and molecular sieves and then distilled to obtain a pure product with a gas phase purity of 98.9% (the yield based on tetrahydrofuran is 73.2%).

[0035] Embodiment 4:

[0036] 1.8g GdCl3(H2O) x Dissolve in 100 mL of water, add 43.2 g of γ-Al2O3 powder, stir and soak at 80°C for 5 hours, and then slowly evaporate the water. Wash the γ-Al2O3 powder with 10 mL of deionized water and dry it at 120°C. Burn the solid at 500°C under nitrogen for 5 hours to obtain the desired Gd-γ-Al2O3 catalyst.

[0037] Subsequently, the required amount of Gd-γ-Al2O3 was placed in a fixed bed reactor (14 mm*1100 mm), nitrogen was introduced, and the set temperature was raised to 350°C. After reaching the set temperature, the metering pump was turned on and tetrahydrofuran (liquid space velocity was 0.4 h -1 ) and ammonia, the molar ratio of ammonia to tetrahydrofuran is controlled at 6: 1. The mixture after the reaction is condensed to obtain a crude tetrahydropyrrole.

[0038] The crude tetrahydropyrrole product is successively dried with NaOH and molecular sieves and then distilled to obtain a pure product with a gas phase purity of 96.9% (the yield based on tetrahydrofuran is 79.8%).

[0039] Embodiment 5:

[0040] 2.0g LaCl3(H2O) x Dissolve in 100 mL of water, add 48 g of γ-Al2O3 powder, stir and soak at 80°C for 5 hours, and then slowly evaporate the water. Wash the γ-Al2O3 powder with 10 mL of deionized water and fully dry it at 120°C. Burn the solid at 500°C under nitrogen for 5 hours to obtain the desired La-γ-Al2O3 catalyst.

[0041] Subsequently, the required amount of La-γ-Al2O3 was placed in a fixed bed reactor (14 mm*1100 mm), nitrogen was introduced, and the set temperature was raised to 370°C. After reaching the set temperature, the metering pump was turned on and tetrahydrofuran (liquid space velocity was 0.4 h -1 ) and ammonia, the molar ratio of ammonia to tetrahydrofuran is controlled at 6: 1. The mixture after the reaction is condensed to obtain a crude tetrahydropyrrole.

[0042] The crude tetrahydropyrrole product is successively dried with NaOH and molecular sieves and then distilled to obtain a pure product with a gas phase purity of 99.3% (the yield based on tetrahydrofuran is 80.3%).

Claims

1. A method for preparing tetrahydropyrrole by catalyzing the amination of tetrahydrofuran by rare earth metal ion-doped γ-alumina, characterized in that The steps include: S1: preparing a catalyst: adding γ-alumina to a rare earth chloride aqueous solution, mixing thoroughly and soaking at 80° C. for 5 to 10 hours; removing water and washing the γ-alumina with deionized water, and calcining to obtain a rare earth metal ion-doped γ-alumina catalyst; S2 Synthesis of tetrahydropyrrole: The catalyst obtained in S1 is loaded into a fixed bed reactor, heated to 250-450°C, and tetrahydrofuran and ammonia are continuously introduced to obtain tetrahydropyrrole.

2. The method according to claim 1, characterized in that: In S1, the rare earth chloride is LaCl3(H2O) x ,CeCl3(H2O) x ,PrCl3(H2O) x ,NdCl3(H2O) x ,SmCl3(H2O) x ,EuCl3(H2O) x ,GdCl3(H2O) x ,ErCl3(H2O) x ,TmCl3(H2O) x and YCl3(H2O) x A combination of one or more of .

3. The method according to claim 1, characterized in that: In S1, the calcination temperature is 350-750° C. or 450-550° C.; and the calcination time is 2-8 hours or 4-6 hours.

4. The method according to claim 1, characterized in that: In S1, the mass ratio of rare earth chloride to γ-alumina is 0.1% to 25% or 3.5 to 6.5%.

5. The method according to claim 1, characterized in that: In S2, the heating temperature during the synthesis of tetrahydropyrrole is 310-350°C.

6. The method according to claim 1, characterized in that: In S2, the molar ratio of ammonia to tetrahydrofuran is 1:1 to 20:1 or 4:1 to 8:

1.

7. The method according to claim 1, characterized in that: In S2, after the crude product is obtained by reaction, it is further condensed, dried and distilled to obtain the final product of tetrahydropyrrole.