A method for preparing piperazine by cyclization of ethylenediamine

Abstract

The present invention provides a method for efficiently preparing piperazine by cyclization of ethylenediamine. A catalyst is filled in a fixed-bed reactor, purged with nitrogen, and then activated by hydrogen. The reaction is carried out using ethylenediamine as the raw material. The catalyst comprises a dealuminated mordenite carrier, an active component, and an auxiliary agent. The active component is a polyacid, and the auxiliary agent is a transition metal. The mass percentage of the active component in the catalyst is 0.10% to 0.80%, and the mass percentage of the auxiliary agent is 0.10% to 5.00%. The present invention is used to prepare piperazine while simultaneously co-producing triethylenediamine, which has high economic value, with low by-products. The conversion rate of ethylenediamine reaches 97%, the selectivity of piperazine reaches 68%, the selectivity of triethylenediamine reaches 25%, and the total selectivity of piperazine and triethylenediamine reaches 93%. The present invention has the advantages of simple operation, few by-products, and low catalyst cost, and can be used for large-scale industrial production.

Description

Technical Field

[0001] The invention belongs to the technical field of piperazine preparation and relates to a method for efficiently preparing piperazine through cyclization of ethylenediamine. Background Art

[0002] Piperazine is a six-membered heterocyclic compound containing two symmetrical nitrogen atoms. Its aqueous solution is weakly alkaline and readily soluble in water. The two opposing nitrogen atoms within the six-membered ring of piperazine provide a large polar surface area, relative structural rigidity, and additional hydrogen bond acceptors and donors, all of which enhance target affinity and specificity, improving water solubility. Due to its unique chemical structure, it is widely used in the pharmaceutical field. Furthermore, the two nitrogen atoms of piperazine can be substituted to connect the two parts of a drug and can also serve as an accessory to adjust the drug's physical and chemical properties. In addition to its widespread use in the pharmaceutical field, piperazine can also be used to synthesize textile dyeing and finishing auxiliaries, preservatives, and antioxidants.

[0003] Existing piperazine production methods are categorized by raw material type, including the chloroethanol method, diethylenetriamine method, hydroxyethylethylenediamine method, ethylenediamine method, and ethanolamine method. Patent CN202011224912 discloses a method for preparing piperazine and ethylenediamine from hydroxyethylethylenediamine. The method involves reacting the hydroxyethyl group with an ammonia source in the presence of hydrogen and a catalyst. Metal modification is employed, resulting in a conversion rate of 95% and a piperazine selectivity of 80% under varying contact conditions. However, the reaction is limited by the availability of an ammonia source, resulting in a complex reaction process that is unsuitable for large-scale industrial production. Patent CN 114436993 A discloses a method for preparing piperazine. In the presence of hydrogen and a catalyst, N-hydroxyethylpiperazine and / or N-aminoethylpiperazine are contacted with an ammonia source for reaction. The catalyst comprises a support, an active component supported on the support, and an optional auxiliary agent. The active component comprises cobalt and / or nickel, and the auxiliary agent is a combination of at least one Group VIB metal, at least one Group IB metal, and at least one Group IIB metal. This method can achieve a piperazine selectivity of 80%, but the high reaction pressure presents certain risks, and the production cost of using N-hydroxyethylpiperazine and / or N-aminoethylpiperazine as the reaction raw materials is high. Currently, the existing ethanolamine process for preparing ethylenediamine and piperazine produces a large number of byproducts, including hydroxyethylethylenediamine, hydroxyethylpiperazine, and N-aminoethylpiperazine, which require significant energy for separation and significantly reduce the piperazine yield. Therefore, there is a need to develop a new piperazine production route to improve piperazine yield and selectivity. Summary of the Invention

[0004] In order to solve the above problems, the present invention provides a method for efficiently preparing piperazine by cyclization of ethylenediamine. The method has high ethylenediamine conversion rate, high piperazine selectivity, simple operation method, and can co-produce triethylenediamine with high economic value, with few by-products, thus realizing large-scale industrialization.

[0005] The technical solutions of the present invention are as follows:

[0006] A method for efficiently preparing piperazine through cyclization of ethylenediamine comprises: filling a catalyst in a fixed-bed reactor, purging with nitrogen, and then introducing hydrogen for activation; and carrying out a reaction using ethylenediamine as a raw material. The catalyst comprises a dealuminated mordenite carrier, an active component, and an auxiliary agent, wherein the active component is a polyacid and the auxiliary agent is a transition metal; the mass percentage of the active component in the catalyst is 0.10%-0.80%, and the mass percentage of the auxiliary agent is 0.10%-5.00%.

[0007] The polyacid is phosphotungstic acid, phosphomolybdic acid or phosphomolybdic vanadium, preferably phosphomolybdic acid.

[0008] The transition metal is one or more of Cu, Ru, Cr, Ni and Mn.

[0009] The catalyst is prepared by using natural mordenite as a matrix and undergoing ion exchange, dealumination, polyacid modification by an impregnation method, and transition metal modification.

[0010] The preparation method of the catalyst comprises the steps of:

[0011] 1) Ion exchange

[0012] Add natural mordenite and 0.5-5 mol / L ammonium salt solution into a flask, react at 60-90°C for 2-5 hours, filter, wash, and dry, and repeat the above steps 2-3 times to obtain ion-exchanged mordenite; the mass ratio of natural mordenite to ammonium salt solution is 1:2-5;

[0013] dealumination

[0014] The ion-exchanged mordenite is treated with a dilute acid solution at room temperature for 2-8 hours, and then dried and calcined to obtain dealuminated mordenite.

[0015] Polyacid modification

[0016] Prepare a polyacid solution, impregnate the dealuminated mordenite at room temperature for 6-10 hours, filter, dry and calcine to obtain a polyacid-modified catalyst;

[0017] Transition metal modification

[0018] Prepare a transition metal salt solution, impregnate the polyacid-modified catalyst at room temperature for 6-10 hours, filter, dry and calcine to obtain the transition metal-modified catalyst.

[0019] The amine salt is NH4Cl, NH4NO3 or NH4NO3, preferably NH4Cl, and the concentration of the NH4Cl solution is 2-4 mol / L.

[0020] The dilute acid is one of citric acid, nitric acid and acetic acid, preferably citric acid, and the concentration of the citric acid solution is 2 mol / L.

[0021] The concentration of the polyacid solution is 0.20%-0.50%, and the concentration of the transition metal salt solution is 0.50%-3.00%.

[0022] The reaction temperature is 120-380 °C, the pressure is 0.2-3 MPa, and the mass space velocity is 0.1-3 h -1 The preferred reaction temperature is 280-350 °C, the pressure is 0.2-1.0 MPa, and the mass space velocity is 0.2-1.2 h -1 , achieving high conversion rate, high yield and high selectivity.

[0023] The beneficial effects of the present invention are that, using the inexpensive and readily available natural mordenite zeolite molecular sieve as the matrix, the catalyst aluminum atoms are reduced, the specific surface area is increased, and the acidity is weakened through ion exchange, weak acid dealumination, polyacid modification, and metal modification. The introduction of the polyacid changes the original catalyst pore size, effectively preventing the generation of some large-volume byproducts and improving product selectivity. Furthermore, a synergistic effect occurs between the polyacid and the transition metal adjuvant to generate active sites with weaker acidity, thereby enhancing reaction activity. The present invention can be used to prepare piperazine while simultaneously co-producing triethylenediamine, which has high economic value, with low byproducts, a conversion rate of ethylenediamine of 97%, a selectivity of piperazine of 68%, a selectivity of triethylenediamine of 25%, and a total selectivity of piperazine and triethylenediamine of 93%. The present invention has the advantages of simple operation, few byproducts, and a low catalyst price. DETAILED DESCRIPTION Example 1

[0024] Natural mordenite and a 2 mol / L ammonium salt solution were placed in a flask at a mass ratio of 1:2.5. The stirring system was activated and the reaction was carried out at 65°C for 3 h. The mixture was then filtered, washed, and dried at 80°C. This process was repeated twice to obtain the ion-exchanged zeolite. The ion-exchanged mordenite was treated with a 2 mol / L citric acid solution at room temperature for 4 h, dried at 80°C, and calcined at 550°C to obtain dealuminated mordenite. A solution of phosphomolybdic acid (0.2% by mass of the catalyst) was prepared and impregnated with the dealuminated mordenite at room temperature for 10 h. The solution was then filtered, dried at 80°C, and calcined at 350°C for 4 h to obtain a polyacid-modified catalyst, designated HPW-cat. A solution of copper nitrate (0.5% by mass of the catalyst) was prepared and impregnated with the catalyst at room temperature for 8 h. The solution was then filtered, dried at 80°C, and calcined at 550°C for 4 h to obtain a transition metal-modified catalyst, designated HPW-Cu-cat. Example 2

[0025] The catalyst HPW-Cu-cat obtained in Example 1 was filled in the constant temperature section of a fixed bed reactor, purged with nitrogen, and then activated with hydrogen. Ethylenediamine was used as the raw material. The reaction temperature was 320°C, the reactor top pressure was 0.5 MPa, and the mass space velocity was 0.4 h -1 The reaction was carried out under 40°C / 60°C conditions, with samples collected from the product collection tank every two hours and analyzed by gas chromatography. At 8 hours, the ethylenediamine conversion was 95%, the piperazine selectivity in the product was 49%, the triethylenediamine selectivity was 30%, and the combined selectivity of piperazine and triethylenediamine was 79%. Example 3

[0026] The catalyst HPW-Cu-cat obtained in Example 1 was filled in the constant temperature section of a fixed bed reactor, purged with nitrogen, and then activated with hydrogen. Using ethylenediamine as the raw material, the reaction temperature was 340°C, the reactor top pressure was 0.5 MPa, and the mass space velocity was 0.6 h -1 The reaction was carried out under 40°C / 100°C conditions, with samples collected from the product collection tank every two hours and analyzed by gas chromatography. At 8 hours, the ethylenediamine conversion was 97%, the piperazine selectivity in the product was 68%, the triethylenediamine selectivity was 25%, and the combined selectivity of piperazine and triethylenediamine was 93%. Example 4

[0027] The catalyst HPW-Cu-cat obtained in Example 1 was filled in the constant temperature section of a fixed bed reactor, purged with nitrogen, and then activated with hydrogen. Ethylenediamine was used as the raw material. The reaction temperature was 360°C, the reactor top pressure was 0.5 MPa, and the mass space velocity was 0.8 h -1 The reaction was carried out under 40°C / 100°C conditions, with samples collected from the product collection tank every two hours and analyzed by gas chromatography. At 8 hours, the ethylenediamine conversion was 86%, the piperazine selectivity in the product was 58%, the triethylenediamine selectivity was 27%, and the combined selectivity of piperazine and triethylenediamine was 85%.

[0028] Comparative Example 1

[0029] The dealuminated mordenite catalyst obtained in Example 1 was filled into the constant temperature section of a fixed bed reactor, purged with nitrogen, and then activated with hydrogen. Ethylenediamine was used as the raw material, and the reaction temperature was 340°C, the reactor top pressure was 0.5 MPa, and the mass space velocity was 0.6 h -1 The reaction was carried out under 40°C / 60°C conditions, with samples collected from the product collection tank every two hours and analyzed by gas chromatography. At 8 hours, the ethylenediamine conversion was 57%, the piperazine selectivity in the product was 26%, the triethylenediamine selectivity was 14%, and the combined selectivity of piperazine and triethylenediamine was 40%.

[0030] Comparative Example 2

[0031] The catalyst HPW-cat obtained in Example 1 was filled in the constant temperature section of a fixed bed reactor, purged with nitrogen, and then activated with hydrogen. Ethylenediamine was used as the raw material. The reaction temperature was 340°C, the reactor top pressure was 0.5 MPa, and the mass space velocity was 0.6 h -1 The reaction was carried out under 40°C / 60°C conditions, with samples collected from the product collection tank every two hours and analyzed by gas chromatography. At 8 hours, the ethylenediamine conversion was 73%, the piperazine selectivity in the product was 49%, the triethylenediamine selectivity was 33%, and the combined selectivity of piperazine and triethylenediamine was 82%.

[0032] Comparative Example 3

[0033] A copper nitrate solution was prepared and impregnated with the dealuminated mordenite obtained in Example 1 at room temperature for 8 h at a catalyst mass percentage of 0.5%. The liquid was then filtered, dried at 80°C and calcined at 550°C for 4 h to obtain the catalyst Cu-cat. The catalyst Cu-cat was placed in the constant temperature section of a fixed bed reactor, purged with nitrogen, and then activated with hydrogen. Ethylenediamine was used as the raw material and the reaction temperature was 340°C, the reactor top pressure was 0.5 MPa, and the mass space velocity was 0.6 h -1 The reaction was carried out under 40°C / 60°C conditions, with samples collected from the product collection tank every two hours and analyzed by gas chromatography. At 8 hours, the ethylenediamine conversion was 69%, the piperazine selectivity in the product was 44%, the triethylenediamine selectivity was 35%, and the combined selectivity of piperazine and triethylenediamine was 79%.

Claims

1. A method for preparing piperazine by cyclization of ethylenediamine, characterized in that: A catalyst is filled in a fixed bed reactor, purged with nitrogen, and then activated by introducing hydrogen. The reaction is carried out using ethylenediamine as a raw material. The catalyst comprises a dealuminated mordenite carrier, an active component, and an additive. The active component is a polyacid, and the additive is a transition metal. The mass percentage of the active component in the catalyst is 0.10%-0.80%, and the mass percentage of the additive is 0.10%-5.00%. The polyacid is phosphotungstic acid, and the transition metal is Cu. The preparation method of the catalyst comprises the following steps: 1) Ion exchange Add natural mordenite and 0.5-5 mol / L ammonium salt solution into a flask, react at 60-90°C for 2-5 hours, filter, wash, and dry, and repeat the above steps 2-3 times to obtain ion-exchanged mordenite; the mass ratio of natural mordenite to ammonium salt solution is 1:2-5; 2) Dealumination The ion-exchanged mordenite is treated with a dilute acid solution at room temperature for 2-8 hours, and then dried and calcined to obtain dealuminated mordenite. 3) Polyacid modification Prepare a polyacid solution, impregnate the dealuminated mordenite at room temperature for 6-10 hours, filter, dry and calcine to obtain a polyacid-modified catalyst; 4) Transition metal modification Prepare a transition metal salt solution, impregnate the polyacid-modified catalyst at room temperature for 6-10 hours, filter, dry and calcine to obtain the transition metal-modified catalyst.

2. The method for preparing piperazine by cyclization of ethylenediamine according to claim 1, wherein: The ammonium salt is NH4Cl or NH4NO3.

3. The method for preparing piperazine by cyclization of ethylenediamine according to claim 1, wherein: The dilute acid is one of citric acid, nitric acid and acetic acid.

4. The method for preparing piperazine by cyclization of ethylenediamine according to claim 1, wherein: The concentration of the polyacid solution is 0.20%-0.50%, and the concentration of the transition metal salt solution is 0.50%-3.00%.

5. The method for preparing piperazine by cyclization of ethylenediamine according to claim 1, wherein: The reaction temperature is 120-380 °C, the pressure is 0.2-3 MPa, and the mass space velocity is 0.1-3 h -1 .