A kind of synthetic method of lactam

Abstract

The present invention belongs to the field of chemical technology, and specifically relates to a method for synthesizing lactam. In a fixed bed reactor, a heterocyclic compound containing an unsaturated N-C bond, CO, and H2 are used as raw materials, and a catalytic reaction occurs under the action of a solid-supported heteropoly acid to obtain a lactam. The present invention proposes a new route for synthesizing lactam, which has a simple technical process and good industrial application prospects.

Description

Technical Field

[0001] The invention belongs to the technical field of chemical engineering, and particularly relates to a method for synthesizing lactam. Background Art

[0002] Lactams are common cyclic structures in organic compounds, forming a ring with the structure R1-CONH-R2 (R1 and R2 are alkyl groups). Lactam rings are crucial for maintaining the antimicrobial activity of certain compounds. Lactams typically have four to seven members, such as caprolactam. Caprolactam is a key monomer in the preparation of the important polymer material nylon 6, which is widely used in clothing, automotive, defense, aerospace, and other fields. Currently, the industrial synthesis of caprolactam uses the cyclohexanone oxime Beckmann rearrangement process.

[0003] Chinese patent CN111116444B discloses a method for synthesizing caprolactam, which uses a photoirradiation method to prepare a transition metal single-atom catalyst and applies it to the synthesis of caprolactam from cyclohexanone oxime. The materials are added in a certain ratio to obtain caprolactam in a vacuum reactor.

[0004] Chinese patent CN106518746B discloses a method for preparing caprolactam, which adopts micro-reaction continuous flow technology, with an organic solution of cyclohexanone oxime as one phase and an organic solvent of 1,1-dichlorocycloheptatriene as another phase, which are pumped into a micro mixer for mixing, and then enter a microreactor through a pipeline for reaction to synthesize caprolactam.

[0005] In addition, researchers are actively exploring new caprolactam synthesis routes. Chinese patent CN111217750A discloses a method for preparing caprolactam. Using a transition metal catalyst on an acidic carrier, lysine, α-amino-ε-caprolactam and its salts, α-(N,N-dimethylamino)-ε-caprolactam and its salts, and other biomass-derived raw materials, caprolactam can be produced under certain reaction conditions from lysine. Summary of the Invention

[0006] The purpose of the present invention is to provide a new lactam synthesis route with simple process.

[0007] The main feature of the present invention is that it combines organic chemical industry and coal chemical industry through the innovation of raw materials and catalytic materials, and realizes a new process route for synthesizing lactams by reacting heterocyclic compounds containing unsaturated NC bonds with synthesis gas (CO+H2).

[0008] The present invention provides a method for synthesizing lactams, which is achieved through the following technical solution:

[0009] A method for synthesizing lactam comprises the following steps: using a heterocyclic compound containing an unsaturated NC bond, CO and H2 as raw materials, and carrying out a catalytic reaction under the action of a catalyst in a fixed bed reactor to obtain the lactam.

[0010] Generally, the heterocyclic compound containing an unsaturated NC bond is one of pyrrole, pyridine, and 1H-azaphene.

[0011] The catalyst is a solid-supported heteropoly acid, which is one of phosphotungstic acid, silicotungstic acid, phosphomolybdic acid and silicomolybdic acid. The carrier of the solid-supported heteropoly acid catalyst is one of aluminum oxide, silicon oxide and activated carbon.

[0012] The mass percentage of the heteropoly acid in the catalyst is 0.5% to 10%.

[0013] The heterocyclic compound containing an unsaturated NC bond can be fed directly, or dissolved in a solvent and fed in the form of a solution.

[0014] The solvent is one of water, alcohol and ether.

[0015] The catalytic reaction is carried out at a temperature of 300-400°C, CO and H2 are introduced, and the system pressure is increased to 2-8 MPa; the heterocyclic compound is pumped into the reactor to undergo a catalytic reaction, and the volume space velocity of the heterocyclic compound is 0.1-2 h -1 The tail gas at the reactor outlet is cooled with water at 0-5°C and the crude lactam is collected.

[0016] The catalytic reaction raw materials satisfy the following requirements: the molar ratio of CO to heterocyclic compound is 1.1-1.5; the molar ratio of H2 to heterocyclic compound is 2.5-10.

[0017] The present invention uses an unsaturated heterocyclic compound containing an NC bond to react with synthesis gas (CO+H2), combining organic chemical industry with coal chemical industry. The process is simple and effective, and opens up a new route for lactam synthesis. DETAILED DESCRIPTION

[0018] The following examples are only used to further explain the content and effects of the present invention, rather than to limit the present invention.

[0019] Example 1

[0020] A phosphotungstic acid / activated carbon catalyst (catalyst specification is φ3×3mm cylindrical) with an acid mass fraction of 0.5% was added to a fixed bed tubular reactor (inner diameter = 35mm). The catalyst was first heated at a space velocity of 1500h -1 The N2 atmosphere was treated at 200℃ for 1h, then N2 was switched to CO+H2 mixed gas, the temperature was raised to 300℃, and the pressure was raised to 8MPa. Then the air velocity was pumped in at 0.1h -1Pyrrole: The raw materials satisfy a CO / heterocyclic compound molar ratio of 1.1 and a H2 / heterocyclic compound molar ratio of 2.5. The tail gas at the reactor outlet is cooled with 5°C water and the crude lactam product is collected. Chromatographic analysis and quantitative calculations indicate a 75% pyrrole conversion and 95% valerolactam selectivity.

[0021] Example 2

[0022] A 1% acid mass fraction of silicotungstic acid / alumina catalyst (catalyst specification is φ3×5mm cylindrical) was added to a fixed bed tubular reactor (inner diameter = 35mm). The catalyst was first heated at a space velocity of 1500h -1 The N2 atmosphere was treated at 200℃ for 1h, then N2 was switched to CO+H2 mixed gas, the temperature was raised to 320℃, and the pressure was raised to 6MPa. Then the air velocity was pumped in at 0.5h -1 A pyridine-water solution (40% pyridine by weight) was prepared using a CO / heterocyclic compound molar ratio of 1.3 and a H2 / heterocyclic compound molar ratio of 4. The reactor outlet exhaust was cooled with 2°C water and the crude lactam product was collected. Chromatographic analysis and quantitative calculations revealed a pyridine conversion of 83% and a caprolactam selectivity of 97%.

[0023] Example 3

[0024] A 5% acid mass fraction of phosphomolybdic acid / silicon oxide catalyst (catalyst specification is φ3mm sphere) was added to a fixed bed tubular reactor (inner diameter = 35mm). The catalyst was first heated at a space velocity of 1500h -1 The N2 atmosphere was treated at 200℃ for 1h, then N2 was switched to CO+H2 mixed gas, the temperature was raised to 340℃, and the pressure was raised to 4MPa. Then the air velocity was pumped in at 0.8h -1 1H-azepine: The raw materials satisfy a CO / heterocyclic compound molar ratio of 1.4 and a H2 / heterocyclic compound molar ratio of 6. The tail gas at the reactor outlet is cooled with 2°C water and the crude lactam product is collected. Chromatographic analysis and quantitative calculations indicate a 1H-azepine conversion of 85% and an enantholactam selectivity of 94%.

[0025] Example 4

[0026] A silicomolybdic acid / activated carbon catalyst (catalyst specification is φ5mm sphere) with an acid mass fraction of 8% was added to a fixed bed tubular reactor (inner diameter = 35mm). The catalyst was first heated at a space velocity of 1500h -1 The N2 atmosphere was treated at 200℃ for 1h, then N2 was switched to CO+H2 mixed gas, the temperature was raised to 360℃, and the pressure was raised to 3MPa. Then the air velocity was pumped in for 1h. -1Pyridine, the raw material satisfies a CO / heterocyclic compound molar ratio of 1.5 and a H2 / heterocyclic compound molar ratio of 8. The tail gas at the reactor outlet is cooled with 2°C water and the crude lactam product is collected. Chromatographic analysis and quantitative calculations indicate a pyridine conversion of 86% and a caprolactam selectivity of 95%.

[0027] Example 5

[0028] A 10% acid mass fraction of phosphotungstic acid / alumina catalyst (catalyst specification is φ5mm sphere) was added to a fixed bed tubular reactor (inner diameter = 35mm). The catalyst was first heated at a space velocity of 1500h -1 The N2 atmosphere was treated at 200℃ for 1h, then N2 was switched to CO+H2 mixed gas, the temperature was raised to 380℃, and the pressure was raised to 2MPa. Then the air velocity was pumped in for 1.2h. -1 Pyridine, the raw material satisfies a CO / heterocyclic compound molar ratio of 1.5 and a H2 / heterocyclic compound molar ratio of 10. The tail gas at the reactor outlet is cooled with 2°C water and the crude lactam product is collected. Chromatographic analysis and quantitative calculation show a pyridine conversion of 82% and a caprolactam selectivity of 96%.

[0029] Example 6

[0030] A 10% acid mass fraction of phosphotungstic acid / alumina catalyst (catalyst specification is φ5mm sphere) was added to a fixed bed tubular reactor (inner diameter = 35mm). The catalyst was first heated at a space velocity of 1500h -1 The N2 atmosphere was treated at 200℃ for 1h, then N2 was switched to CO+H2 mixed gas, the temperature was raised to 400℃, and the pressure was raised to 5MPa. Then the air velocity was pumped in for 1.4h. -1 Pyridine, the raw material satisfies a CO / heterocyclic compound molar ratio of 1.5 and a H2 / heterocyclic compound molar ratio of 6. The tail gas at the reactor outlet is cooled with 2°C water and the crude lactam product is collected. Chromatographic analysis and quantitative calculation show a pyridine conversion of 86% and a caprolactam selectivity of 97%.

[0031] Example 7

[0032] A 10% acid mass fraction of phosphotungstic acid / alumina catalyst (catalyst specification is φ5mm sphere) was added to a fixed bed tubular reactor (inner diameter = 35mm). The catalyst was first heated at a space velocity of 1500h -1 The N2 atmosphere was treated at 200℃ for 1h, then N2 was switched to CO+H2 mixed gas, the temperature was raised to 360℃, and the pressure was raised to 5MPa. Then the air velocity was pumped in for 1.6h. -1Pyridine, the raw material satisfies a CO / heterocyclic compound molar ratio of 1.5 and a H2 / heterocyclic compound molar ratio of 7. The tail gas at the reactor outlet is cooled with 2°C water and the crude lactam product is collected. Chromatographic analysis and quantitative calculation show a pyridine conversion of 88% and a caprolactam selectivity of 96%.

[0033] Example 8

[0034] A 10% acid mass fraction of phosphotungstic acid / alumina catalyst (catalyst specification is φ5mm sphere) was added to a fixed bed tubular reactor (inner diameter = 35mm). The catalyst was first heated at a space velocity of 1500h -1 The N2 atmosphere was treated at 200℃ for 1h, then N2 was switched to CO+H2 mixed gas, the temperature was raised to 360℃, and the pressure was raised to 5MPa. Then the air velocity was pumped in for 2h. -1 Pyridine, the raw material satisfies a CO / heterocyclic compound molar ratio of 1.5 and a H2 / heterocyclic compound molar ratio of 8. The tail gas at the reactor outlet is cooled with 2°C water and the crude lactam product is collected. Chromatographic analysis and quantitative calculations indicate a pyridine conversion of 91% and a caprolactam selectivity of 97%.

Claims

1. A method for synthesizing lactam, characterized in that: In a fixed bed reactor, a heterocyclic compound containing an unsaturated NC bond, CO and H2 are used as raw materials, and a catalytic reaction occurs under the action of a catalyst to obtain lactam; the catalytic reaction has a reaction temperature of 300-400°C, CO and H2 are introduced, and the system pressure is increased to 2-8MPa; the heterocyclic compound is pumped into the reactor for a catalytic reaction, and the volume space velocity of the heterocyclic compound is 0.1-2h -1 , the tail gas at the reactor outlet is cooled with water at 0-5°C, and a crude lactam product is collected; the catalytic reaction raw materials satisfy that the molar ratio of CO / heterocyclic compound is 1.1-1.5; the molar ratio of H2 / heterocyclic compound is 2.5-10; the heterocyclic compound containing unsaturated NC bonds is one of pyrrole, pyridine, and 1H-azaquinone, the raw material is pyrrole, and the crude valerolactam product is obtained; the raw material is pyridine, and the crude caprolactam product is obtained; the raw material is 1H-azaquinone, and the crude enantholactam product is obtained; the catalyst is a solid-supported heteropolyacid, and the solid-supported heteropolyacid is one of phosphotungstic acid, silicotungstic acid, phosphomolybdic acid, and silicomolybdic acid.

2. The synthesis method according to claim 1, characterized in that The carrier of the immobilized heteropolyacid catalyst is one of aluminum oxide, silicon oxide and activated carbon.

3. The synthesis method according to claim 1, characterized in that The mass percentage of the heteropoly acid in the catalyst is 0.5% to 10%.

4. The synthesis method according to claim 1, characterized in that The heterocyclic compound containing NC bonds is fed directly, or dissolved in a solvent and fed in the form of a solution.

5. The synthesis method according to claim 4, characterized in that The solvent is one of water, alcohol and ether.