Preparation method of 2-pyrrolidone

Abstract

The invention discloses a preparation method of 2-pyrrolidone, and belongs to the technical field of fine chemical engineering and catalysis. According to the method, maleimide is taken as a raw material, and 2-pyrrolidone is prepared by hydrogenation reaction under mild conditions in a 1, 4-dioxane solvent by utilizing the synergistic effect of a main catalyst Raney nickel and a cocatalyst rare earth Lewis compound; the mass ratio of 1, 4-dioxane to maleimide is (10: 1)-(2: 1), the mass ratio of maleimide to a Raney nickel catalyst is (1000: 1)-(100: 1), the molar ratio of maleimide to a rare earth Lewis compound is 1: 1, the hydrogen pressure is 2-4MPa, the reaction temperature is 140-180 DEG C, reacting for 16-24 hours, filtering and recovering Raney nickel after the reaction, and carrying out reduced pressure distillation to separate a solvent and a product, and the rare earth compound is recycled after being purified. According to the method, selective hydrogenation is achieved through the synergistic effect of the composite catalyst, the product yield reaches 95.3%-99.5%, the purity is larger than or equal to 99.2%, compared with a traditional method, the condition is mild, use of precious metal catalysts is avoided, the catalyst and the solvent can be recycled, and the production cost and pollution are reduced.

Description

Technical Field

[0001] This invention belongs to the field of fine chemicals and catalysis technology, specifically relating to a method for the selective hydrogenation of maleimide to 2-pyrrolidone in 1,4-dioxane using a composite catalytic system composed of Raney nickel and rare earth metal Lewis acidic compounds. Background Technology

[0002] 2-Pyrrolidone is an important pentamer compound with excellent chemical stability, good solubility, and broad chemical reactivity, making it widely used in coatings, adhesives, inks, textile auxiliaries, pesticides, and pharmaceuticals. Patent CN1258528C reports the preparation of 2-pyrrolidone by reacting γ-butyrolactone with ammonia. The reaction is carried out at 275-300℃ and 140-180 bar absolute pressure, with a yield of 94.3%. However, this method suffers from drawbacks such as high temperature, high pressure, and high energy consumption. Patent CN108709087B utilizes the waste residue generated during the production of N-vinylpyrrolidone as a raw material to prepare 2-pyrrolidone. Although the process does not involve unit reactions, the low concentration of the product in the raw material and its limited availability restrict its large-scale production application. The literature J.Am.Chem.Soc.[2015,137(14):4851] reports the synthesis of 2-pyrrolidone from tetrahydropyrrole in a mixed solvent of dioxane and toluene using (AcrPNPiPr)RuH(CO)Cl as a catalyst, with a product yield of approximately 59%. However, this technique involves numerous catalyst preparation steps and expensive raw materials. Patent CN108727243A describes the preparation of 2-pyrrolidone from pyroglutamic acid (II), which also suffers from a low product yield (60%). It is evident that the above methods for preparing 2-pyrrolidone suffer from drawbacks such as high reaction temperature, high cost of the catalytic system, small scale, or low product yield, limiting their industrial-scale application.

[0003] This application proposes a highly efficient and selective catalytic hydrogenation method for the preparation of 2-pyrrolidone. The method uses 1,4-dioxane as a solvent and employs a composite catalytic system composed of the non-precious metal Raney nickel and a rare-earth Lewis acid compound to catalyze the selective hydrogenation of maleimide to prepare 2-pyrrolidone. During the reaction, Raney nickel exhibits excellent catalytic performance on the double bonds and carbonyl groups of the substrate. Simultaneously, the rare-earth Lewis acid compound can coordinate and complex with one of the carbonyl groups of the substrate (once a carbonyl group is complexed, the inductive effect of this complexation reduces the reactivity of the other carbonyl group in the complexation reaction, inhibiting further complexation). This coordination complex allows the lone pair electrons of oxygen to be accepted by the empty orbitals of the Lewis acid, leading to a significant increase in the positive charge of the carbonyl carbon. Simultaneously, the complexation increases the polarity of the C=O bond of the carbonyl group, lengthens the bond length (approaching a single bond), and makes it easier to break, thus lowering the hydrogenation transition state energy and accelerating the hydrogenation reaction. Furthermore, once the carbonyl group has undergone hydrogenation, the byproduct water will react with the rare earth Lewis acidic compound in the form of a hydrate, thus preventing the rare earth Lewis acidic compound from continuing its complexation reaction. This prevents the other carbonyl group from undergoing further hydrogenation and reduction, thereby completing the selective hydrogenation reaction of the two carbonyl groups of the reaction substrate to produce the target product 2-pyrrolidone. Summary of the Invention

[0004] This invention replaces the traditional method for preparing 2-pyrrolidone by reacting γ-butyrolactone with ammonia. It proposes a method using maleimide as a raw material to produce 2-pyrrolidone, solving the problems of complex synthetic routes and low yields in existing methods. This invention utilizes the synergistic catalytic effect of the main catalyst and co-catalyst to achieve selective hydrogenation of one of the two carbonyl groups of the substrate, yielding 2-pyrrolidone in high yield. Furthermore, it enables the recycling of the main catalyst and solvent, reducing production costs and environmental pollution.

[0005] Based on the above, the present invention relates to a method for preparing 2-pyrrolidone, characterized by comprising the following steps: 1,4-dioxane to maleimide are added to a pressure reactor at a mass ratio of 10:1-2:1, maleimide to Raney nickel catalyst is 1000:1-100:1, and maleimide to rare earth Lewis compound is 1:1; hydrogen is introduced into the reactor to replace air 3-5 times; subsequently, hydrogen is introduced until the pressure is reached. The reaction was carried out at a pressure of 2-4 MPa and heated to 140-180℃ for 16-24 h. After the reaction was completed, the Raney nickel catalyst was separated by filtration and recycled. The filtrate was distilled under reduced pressure to obtain the solvent 1,4-dioxane and the product 2-pyrrolidone. The obtained 1,4-dioxane could be recycled after dehydration. The yield of the product 2-pyrrolidone was 95.3-99.5% and the purity was ≥99.2%. The residue in the reactor was mainly rare earth Lewis acidic compounds.

[0006] The Raney nickel catalyst is characterized in that it needs to be pre-activated with a 10% sodium hydroxide solution for 0.5-1 h.

[0007] The present invention is characterized in that the rare earth Lewis compound cocatalyst is one of cerium oxide, lanthanum oxide, scandium oxide, yttrium oxide, scandium chloride, and yttrium chloride.

[0008] The present invention is characterized in that the separated Raney nickel catalyst is regenerated by the following steps: ultrasonic cleaning with 5% sodium hydroxide solution for 30 min, washing with deionized water until pH=7-8, vacuum drying, activation at 300℃ in a hydrogen atmosphere for 2 h, and then recycling.

[0009] The present invention is characterized in that the residue in the reactor mainly consists of rare earth Lewis acidic compounds, which can be recycled after purification through the following steps: 1-3 times the mass of the residue is dissolved in deionized water, and the mixture is extracted three times with an equal volume of chloroform to extract organic matter. The raffinate is dehydrated and dried to obtain the rare earth Lewis acidic compounds, which are then recycled. The chloroform in the extract is recovered by atmospheric distillation and reused. The present invention utilizes a composite catalytic system composed of Raney nickel and rare earth Lewis compounds, exhibiting excellent synergistic catalytic performance. Compared with traditional reaction conditions, the conditions are milder, and the product yield is high. The main catalyst, Raney nickel, replaces the precious metal catalyst and has good reusability, resulting in low catalyst cost.

[0010] This invention solves this technical problem through the following technical solution:

[0011] The specific technical solution is illustrated using scandium chloride, a rare earth Lewis acidic compound and a co-catalyst.

[0012] 30g of maleimide, 0.3g of Raney nickel catalyst, scandium chloride (an equimolar amount of rare earth Lewis acidic compound) as a co-catalyst, and 300g of 1,4-dioxane were added to a high-pressure sealed reactor. The air inside the reactor was replaced three times with hydrogen, and the reactor was then purged with hydrogen at a pressure of 4MPa. The material inside the reactor was heated to 180℃ and kept at this temperature with stirring for 24 hours. The reactor was then cooled in a hot water bath and then cooled to room temperature. The pressure was released, and the reaction mixture was filtered to obtain Raney nickel. The filtrate was distilled under reduced pressure to obtain the solvent 1,4-dioxane and the product 2-pyrrolidone. The product purity was ≥99.2% and the yield was 99.5%. The reactor residue was dissolved in about 1.5 times its mass of deionized water and extracted three times with an equal volume of chloroform. The extracts were combined, distilled to obtain chloroform, and reused. The raffinate was dehydrated to obtain scandium chloride, which was also reused.

[0013] Compared with traditional methods, the present invention is characterized by:

[0014] 1. This invention utilizes the synergistic catalytic effect of a composite catalytic system composed of a main catalyst and a co-catalyst to achieve selective hydrogenation of the reaction substrate to prepare the target product.

[0015] 2. The present invention has a short reaction route, high selectivity and yield of the target product, few by-products, and high yield.

[0016] 3. The reusability of the main and co-catalysts obtained by separation and purification after the reaction in this invention. Specific implementation methods

[0017] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0018] Example 1: 30g of maleimide, 0.3g of Raney nickel catalyst, scandium chloride (an equimolar amount of rare earth Lewis acidic compound) as a co-catalyst, and 180g of 1,4-dioxane were added to a high-pressure sealed reactor. The air inside the reactor was replaced with hydrogen three times, and hydrogen was introduced into the reactor at a pressure of 4MPa. The material inside the reactor was heated to 180°C and kept at this temperature with stirring for 20 hours. The reactor was then cooled in a hot water bath and then cooled to room temperature. The pressure was released, and the reaction mixture was filtered to obtain Raney nickel. The filtrate was distilled under reduced pressure to obtain the solvent 1,4-dioxane and the product 2-pyrrolidone. The product purity was ≥99.2% and the yield was 99.2%. The reactor residue was dissolved in about 1.5 times its mass of deionized water and extracted three times with an equal volume of chloroform. The extracts were combined, distilled to obtain chloroform, and reused. The raffinate was dehydrated to obtain scandium chloride, which was also reused.

[0019] Comparative Example 1: This comparative example provides a method for preparing 2-pyrrolidone. The difference between this method and the example is that the comparative example only uses Raney nickel as a catalyst. The specific dosage is as follows: 30g of maleimide, 0.3g of Raney nickel catalyst, and 300g of 1,4-dioxane are added to a high-pressure sealed reactor. The air inside the reactor is replaced with hydrogen three times. Hydrogen is introduced into the reactor at a pressure of 4MPa. The material inside the reactor is heated to 180°C and kept at that temperature with stirring for 24 hours. The reactor is then cooled in a hot water bath and cooled to room temperature. The pressure is released, and the reaction mixture is filtered to obtain Raney nickel. The filtrate is distilled under reduced pressure to obtain the solvent 1,4-dioxane and the product 2-pyrrolidone, with a yield of 68.5%.

[0020] Comparative Example 2: This comparative example provides a method for preparing 2-pyrrolidone. The difference between this method and the example is that the comparative example only uses scandium chloride, a rare earth Lewis acidic compound, as a reaction catalyst in the same molar amount as maleimide. The specific amounts are as follows: 30g of maleimide, scandium chloride in the same molar amount as maleimide, and 300g of 1,4-dioxane are added to a high-pressure sealed reactor. The air inside the reactor is replaced with hydrogen three times. Hydrogen is introduced into the reactor at a pressure of 4MPa. The material inside the reactor is heated to 180°C and kept at this temperature with stirring for 24 hours. The reactor is then cooled in a hot water bath and cooled to room temperature. The pressure is released, the reaction mixture is filtered, and the filtrate is distilled under reduced pressure to obtain the solvent 1,4-dioxane and the product 2-pyrrolidone, with a yield of 15.5%.

[0021] Example 2: 30g of maleimide, 0.03g of Raney nickel catalyst, cerium oxide (a rare earth Lewis acid compound) as an equimolar co-catalyst to maleimide, and 300g of 1,4-dioxane were added to a high-pressure sealed reactor. The air inside the reactor was replaced with hydrogen three times, and hydrogen was introduced into the reactor at a pressure of 2MPa. The material inside the reactor was heated to 140°C and kept at this temperature with stirring for 16 hours. The reactor was then cooled in a hot water bath and then cooled to room temperature. The pressure was released, and the reaction mixture was filtered to obtain Raney nickel. The filtrate was distilled under reduced pressure to obtain the solvent 1,4-dioxane and the product 2-pyrrolidone. The product purity was ≥99.2% and the yield was 95.5%. The reactor residue was dissolved in about 1.5 times its mass of deionized water and extracted three times with an equal volume of chloroform. The extracts were combined, distilled to obtain chloroform, and reused. The raffinate was dehydrated to obtain cerium oxide, which was also reused.

[0022] Example 3: 30g of maleimide, 0.05g of Raney nickel catalyst, cerium oxide (a rare earth Lewis acid compound) as an equimolar amount of maleimide co-catalyst, and 60g of 1,4-dioxane were added to a high-pressure sealed reactor. The air inside the reactor was replaced with hydrogen three times, and the reactor was purged with hydrogen at a pressure of 3MPa. The material inside the reactor was heated to 160°C and kept at this temperature with stirring for 16 hours. The reactor was then cooled in a hot water bath and then cooled to room temperature. The pressure was released, and the reaction mixture was filtered to obtain Raney nickel. The filtrate was distilled under reduced pressure to obtain the solvent 1,4-dioxane and the product 2-pyrrolidone. The product purity was ≥99.2% and the yield was 96.5%. The reactor residue was dissolved in about 1.5 times its mass of deionized water and extracted three times with an equal volume of chloroform. The extracts were combined, distilled to obtain chloroform, and reused. The raffinate was dehydrated to obtain cerium oxide, which was also reused.

[0023] Example 4: 30g of maleimide, 0.05g of Raney nickel catalyst, lanthanum oxide (an equimolar amount of rare earth Lewis acid compound co-catalyst), and 300g of 1,4-dioxane were added to a high-pressure sealed reactor. The air inside the reactor was replaced with hydrogen three times, and hydrogen was introduced into the reactor at a pressure of 4MPa. The material inside the reactor was heated to 180°C and kept at this temperature with stirring for 20 hours. The reactor was then cooled in a hot water bath and then cooled to room temperature. The pressure was released, and the reaction mixture was filtered to obtain Raney nickel. The filtrate was distilled under reduced pressure to obtain the solvent 1,4-dioxane and the product 2-pyrrolidone. The product purity was ≥99.2% and the yield was 97.9%. The reactor residue was dissolved in about 1.5 times its mass of deionized water and extracted three times with an equal volume of chloroform. The extracts were combined, distilled to obtain chloroform, and reused. The raffinate was dehydrated to obtain lanthanum oxide, which was also reused.

[0024] Example 5: 30g of maleimide, 0.3g of Raney nickel catalyst, scandium oxide (an equimolar amount of rare earth Lewis acidic compound) as a co-catalyst, and 300g of 1,4-dioxane were added to a high-pressure sealed reactor. The air inside the reactor was replaced with hydrogen three times, and the reactor was purged with hydrogen at a pressure of 4MPa. The material inside the reactor was heated to 180°C and kept at that temperature with stirring for 16 hours. The reactor was then cooled in a hot water bath and then cooled to room temperature. The pressure was released, and the reaction mixture was filtered to obtain Raney nickel. The filtrate was distilled under reduced pressure to obtain the solvent 1,4-dioxane and the product 2-pyrrolidone. The product purity was ≥99.2% and the yield was 97.5%. The reactor residue was dissolved in about 1.5 times its mass of deionized water and extracted three times with an equal volume of chloroform. The extracts were combined, distilled to obtain chloroform, and reused. The raffinate was dehydrated to obtain scandium oxide, which was also reused.

[0025] Example 6: 30g of maleimide, 0.3g of Raney nickel catalyst, yttrium oxide (an equimolar amount of rare earth Lewis acidic compound co-catalyst), and 300g of 1,4-dioxane were added to a high-pressure sealed reactor. The air inside the reactor was replaced with hydrogen three times, and the reactor was purged with hydrogen at a pressure of 3MPa. The material inside the reactor was heated to 160°C and kept at this temperature with stirring for 20 hours. The reactor was then cooled in a hot water bath and then cooled to room temperature. The pressure was released, and the reaction mixture was filtered to obtain Raney nickel. The filtrate was distilled under reduced pressure to obtain the solvent 1,4-dioxane and the product 2-pyrrolidone. The product purity was ≥99.2% and the yield was 96.2%. The reactor residue was dissolved in about 1.5 times its mass of deionized water and extracted three times with an equal volume of chloroform. The extracts were combined, distilled to obtain chloroform, and reused. The raffinate was dehydrated to obtain yttrium oxide, which was also reused.

[0026] Example 7: 30g of maleimide, 0.3g of Raney nickel catalyst, yttrium chloride (an equimolar amount of rare earth Lewis acidic compound) as a co-catalyst, and 60g of 1,4-dioxane were added to a high-pressure sealed reactor. The air inside the reactor was replaced with hydrogen three times, and hydrogen was introduced into the reactor at a pressure of 3MPa. The material inside the reactor was heated to 180°C and kept at this temperature with stirring for 16 hours. The reactor was then cooled in a hot water bath and then cooled to room temperature. The pressure was released, and the reaction mixture was filtered to obtain Raney nickel. The filtrate was distilled under reduced pressure to obtain the solvent 1,4-dioxane and the product 2-pyrrolidone. The product purity was ≥99.2% and the yield was 97.2%. The reactor residue was dissolved in about 1.5 times its mass of deionized water and extracted three times with an equal volume of chloroform. The extracts were combined, distilled to obtain chloroform, and reused. The raffinate was dehydrated to obtain yttrium chloride, which was also reused.

[0027] Example 8: 30g of maleimide, 0.3g of Raney nickel catalyst, yttrium chloride (an equimolar amount of rare earth Lewis acidic compound) as a co-catalyst, and 180g of 1,4-dioxane were added to a high-pressure sealed reactor. The air inside the reactor was replaced with hydrogen three times, and the reactor was purged with hydrogen at a pressure of 4MPa. The material inside the reactor was heated to 180°C and kept at that temperature with stirring for 16 hours. The reactor was then cooled in a hot water bath and then cooled to room temperature. The pressure was released, and the reaction mixture was filtered to obtain Raney nickel. The filtrate was distilled under reduced pressure to obtain the solvent 1,4-dioxane and the product 2-pyrrolidone. The product purity was ≥99.2% and the yield was 98.2%. The reactor residue was dissolved in about 1.5 times its mass of deionized water and extracted three times with an equal volume of chloroform. The extracts were combined, distilled to obtain chloroform, and reused. The raffinate was dehydrated to obtain yttrium chloride, which was also reused.

[0028] Example 9: 30g of maleimide, 0.3g of Raney nickel catalyst, lanthanum oxide (an equimolar amount of rare earth Lewis acidic compound) as a co-catalyst to maleimide, and 180g of 1,4-dioxane were added to a high-pressure sealed reactor. The air inside the reactor was replaced with hydrogen three times, and hydrogen was introduced into the reactor at a pressure of 4MPa. The material inside the reactor was heated to 180°C and kept at this temperature with stirring for 16 hours. The reactor was then cooled in a hot water bath and then cooled to room temperature. The pressure was released, and the reaction mixture was filtered to obtain Raney nickel. The filtrate was distilled under reduced pressure to obtain the solvent 1,4-dioxane and the product 2-pyrrolidone. The product purity was ≥99.2% and the yield was 99.1%. The reactor residue was dissolved in about 1.5 times its mass of deionized water and extracted three times with an equal volume of chloroform. The extracts were combined, distilled to obtain chloroform, and reused. The raffinate was dehydrated to obtain lanthanum oxide, which was also reused.

[0029] Example 10: The solid Raney nickel catalyst recovered in Example 1 was ultrasonically cleaned with 5% sodium hydroxide solution for 30 min, washed with deionized water until pH=7-8, vacuum dried, and activated at 300℃ for 2 h in a hydrogen atmosphere. It was then added to a high-pressure sealed reactor along with the dehydrated co-catalyst scandium chloride, 30 g maleimide, and 180 g 1,4-dioxane. The air inside the reactor was replaced three times with hydrogen, and the reactor was then purged with hydrogen at a pressure of 4 MPa. The material inside the reactor was heated to 180℃ and held at that temperature. After stirring for 20 hours, the reactor was cooled in a hot water bath, then cooled to room temperature, and the pressure was released. The reaction mixture was filtered to obtain Raney nickel. The filtrate was distilled under reduced pressure to obtain solvent 1,4-dioxane and product 2-pyrrolidone. The product purity was ≥99.2% and the yield was 98.6%. The catalyst recovered in this example was reused 16 times under the same experimental conditions. The 2-pyrrolidone obtained from the 16 reuses had a yield ≥98% and a purity ≥99.2%.

[0030] Example 11: The solid Raney nickel catalyst recovered in Example 2 was ultrasonically cleaned with 5% sodium hydroxide solution for 30 min, washed with deionized water until pH=7-8, vacuum dried, and activated at 300℃ for 2 h in a hydrogen atmosphere. It was then added to a high-pressure sealed reactor along with the dehydrated co-catalyst cerium chloride, 30 g of maleimide, and 300 g of 1,4-dioxane. The air inside the reactor was replaced three times with hydrogen. The reactor was then purged with hydrogen at a pressure of 2 MPa. The material inside the reactor was heated to 140℃ and held at that temperature. After stirring for 16 hours, the reactor was cooled in a hot water bath, then cooled to room temperature, and the pressure was released. The reaction mixture was filtered to obtain Raney nickel. The filtrate was distilled under reduced pressure to obtain solvent 1,4-dioxane and product 2-pyrrolidone. The product purity was ≥99.2% and the yield was 95.3%. The catalyst recovered in this example was reused 16 times under the same experimental conditions. The yield of 2-pyrrolidone obtained from the 16 reuses was ≥95% and the purity was ≥99.2% in all cases.

Claims

1. A method for preparing 2-pyrrolidone, characterized in that... Includes the following steps: The 1,4-dioxane to maleimide mass ratio was 10:1-2:1, the maleimide to Raney nickel catalyst mass ratio was 1000:1-100:1, and the maleimide to rare earth Lewis acid compound molar ratio was 1:

1. Hydrogen gas was introduced into the reactor to replace the air 3-5 times, followed by hydrogen purging to a pressure of 2-4 MPa. The reactor was heated to 140-180℃ and held at this temperature for 16-24 hours. After the reaction, the Raney nickel catalyst was filtered out and recycled. The filtrate was distilled under reduced pressure to obtain the solvent 1,4-dioxane and the product 2-pyrrolidone. The obtained 1,4-dioxane could be recycled after dehydration. The yield of the product 2-pyrrolidone was 95.3-99.5%, and the purity was ≥99.2%. The residue in the reactor mainly consisted of rare earth Lewis acid compounds.

2. The method according to claim 1, characterized in that, The Raney nickel catalyst needs to be pre-activated with a 10% sodium hydroxide solution for 0.5-1 hour.

3. The method according to claim 1, characterized in that, The rare earth Lewis compound cocatalyst is one of cerium oxide, lanthanum oxide, scandium oxide, yttrium oxide, scandium chloride, and yttrium chloride.

4. The method according to claim 1, characterized in that, The separated Raney nickel catalyst was regenerated by the following steps: ultrasonic cleaning with 5% sodium hydroxide solution for 30 min, washing with deionized water until pH=7-8, vacuum drying, activation at 300℃ in a hydrogen atmosphere for 2 h, and then recycling.

5. The method according to claim 1, characterized in that, The residue in the reactor mainly consists of rare earth Lewis acidic compounds. After purification through the following steps, it can be recycled: add 1-3 times the mass of the residue to deionized water to dissolve it, and then extract the organic matter with an equal volume of chloroform. After dehydration and drying, the raffinate phase yields the rare earth Lewis acidic compounds, which are then recycled. The chloroform phase is recovered by atmospheric distillation and reused.