Process for the preparation of hexamethylenediamine by aminolysis

Abstract

This invention relates to the field of hexamethylenediamine production technology and discloses a method for preparing hexamethylenediamine by ammonolysis. The method includes the following steps: (1) ammonolyzing a high-boiling-point amine with a boiling point above 200℃ to obtain an ammonolysis product; (2) separating the ammonolysis product to obtain a C6 amine stream containing hexamethylenediamine, a component with a boiling point of 230-300℃, and a heavy component, and then returning the component with a boiling point of 230-300℃ to step (1) for further ammonolysis. The method of this invention achieves comprehensive utilization of high-boiling-point amines in the hexanediamine ammoniation reaction product through ammonolysis, improves the yield of hexamethylenediamine, and overcomes the current situation of insufficient hexamethylenediamine production capacity.

Description

Technical Field

[0001] This invention relates to the field of hexamethylenediamine production technology, and specifically to a method for preparing hexamethylenediamine by ammonolysis. Background Technology

[0002] Hexamethylenediamine, with the molecular formula C6H 16 Hexamethylenediamine (H2) is the main raw material for the production of Nylon 66. In addition, H2 is widely used in aerospace (polyurethane materials), mining (oilfield demulsifiers), agriculture (pesticides), and construction (concrete additives). With the expanding applications of H2 and increasing demand from downstream products, the supply of raw material H2 is gradually falling short of demand.

[0003] CN114433113A developed a nickel and / or cobalt, molybdenum, copper, and zinc catalyst for the amination of alcohols, which dehydrates hexanediol under hydrogen-containing conditions to produce hexanediamine. This method has the advantages of simple process, non-toxic materials, environmentally friendly emissions, and high inherent safety. However, the yield is low, and the reaction generates a large amount of high-boiling-point amines. Direct discharge of these high-boiling-point amines not only causes environmental pollution but also wastes resources. Therefore, the inventors propose a method to further ammonolyze high-boiling-point amines to obtain hexanediamine. Summary of the Invention

[0004] The purpose of this invention is to overcome the problem of resource waste caused by high-boiling-point amines in the production of hexamethylenediamine in the existing technology, and to provide a method for preparing hexamethylenediamine by ammonolysis.

[0005] To achieve the above objectives, a first aspect of the present invention provides a method for preparing hexamethylenediamine via ammonolysis, the method comprising the following steps:

[0006] (1) Ammonolysis of high-boiling-point amines with boiling points above 200℃ yields the ammonolysis products;

[0007] (2) Separate the ammonolysis product to obtain a C6 amine stream containing hexamethylenediamine, a component with a boiling point of 230-300℃ and a heavy component, and then return the component with a boiling point of 230-300℃ to step (1) to continue ammonolysis.

[0008] A second aspect of the present invention provides a system for preparing hexamethylenediamine by ammonolysis in the first aspect. The system comprises: an ammonolysis reactor for ammonolyzing a high-boiling-point amine to obtain an ammonolysis product; a pre-separation unit for separating ammonia and hydrogen from the ammonolysis product to obtain a pre-separated product and a stream containing ammonia and hydrogen; and an ammonolysis product purification unit for separating the pre-separated product to obtain a C6 amine stream containing hexamethylenediamine, a component with a boiling point of 230-300°C, and a heavy component.

[0009] The method of this invention achieves comprehensive utilization of high-boiling-point amines in the hexanediamine amination product through ammonolysis, thereby increasing the yield of hexanediamine and overcoming the current situation of insufficient hexanediamine production capacity. In a preferred embodiment, this invention utilizes an ammonolysis catalyst with a long lifespan, low reaction temperature, and high hexanediamine conversion rate. Attached Figure Description

[0010] Figure 1 This is a schematic diagram of a preferred method for preparing hexamethylenediamine according to the present invention.

[0011] Explanation of reference numerals in the attached figures

[0012] 1-Ammonolysis reactor; 2-Pre-separation unit; 3-Hydrogen compressor; 4-Ammonolysis product purification unit; 11-High-boiling-point amines; 12-Fresh hydrogen; 13-Fresh ammonia; 14-C6 amine stream containing hexamethylenediamine; 15-Components with boiling points of 230-300℃; 16-Heavy components; 17-Solvent Detailed Implementation

[0013] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0014] In this invention, C6 amine refers to an amine compound with 6 carbon atoms, and C12 amine refers to an amine compound with 12 carbon atoms.

[0015] Besides hexanediamine, the products of hexanediol ammoniation also include cycloheximine, aminohexanol, and a certain amount of amine dimers. The amine dimers have high boiling points and are difficult to utilize. If the amine dimers could be fully utilized, the economic efficiency of the hexanediol ammoniation reaction would be improved. Therefore, this invention provides a method for preparing hexanediamine via ammonolysis, the method comprising the following steps:

[0016] (1) Ammonolysis of high-boiling-point amines with boiling points above 200℃ yields the ammonolysis products;

[0017] (2) Separate the ammonolysis product to obtain a C6 amine stream containing hexamethylenediamine, a component with a boiling point of 230-300℃ and a heavy component (boiling point above 300℃), and then return the component with a boiling point of 230-300℃ to step (1) to continue ammonolysis.

[0018] According to the present invention, preferably, the boiling point of the high-boiling-point amine is 200-400°C, more preferably 230-300°C.

[0019] According to the present invention, ammonolysis is preferably carried out in the presence of ammonia and hydrogen, wherein the weight ratio of ammonia to high-boiling-point amine is 3.5-12:1, preferably 6-9.5:1; and the weight ratio of hydrogen to high-boiling-point amine is 0.01-0.2:1, preferably 0.02-0.1:1.

[0020] According to the present invention, preferably, the ammonolysis temperature is 140-260°C, more preferably 150-255°C; the ammonolysis pressure is 10-24 MPaG, more preferably 11-22 MPaG; and the liquid hourly space velocity of the high-boiling-point amine is 0.05-7 h⁻¹. -1 Preferably, it is 0.09-1.9h. -1 .

[0021] According to the present invention, preferably, the high-boiling-point amine is provided by an amination product containing a high-boiling-point amine, said amination product containing a C12 amine and at least one selected from cyclohexylimine, aminohexanol, and hexanediol. The high-boiling-point amine in the present invention is derived from the amination product generated by the amination of hexanediol, after the removal of hexanediamine, ammonia, hydrogen, and most of the cyclohexylimine and aminohexanol. More preferably, the high-boiling-point amine contains 40-99% by weight of C12 amine, 0-10% by weight of the total content of cyclohexylimine and aminohexanol, and 0-30% by weight of hexanediol. The high-boiling-point amine may also contain small amounts of other components (e.g., caprolactam).

[0022] According to the present invention, in order to further promote the ammonolysis reaction, increase the yield of hexamethylenediamine, and avoid the solidification of high-boiling-point amines, the ammonolysis reaction is preferably carried out in the presence of a solvent, wherein the concentration of the high-boiling-point amine in the mixture of the high-boiling-point amine and the solvent is 30-80% by weight.

[0023] According to the present invention, in order to further improve the yield of hexamethylenediamine, preferably, the solvent is selected from at least one of tetrahydrofuran, 1,4-dioxane, n-hexane and cyclohexane.

[0024] According to the present invention, preferably, the method for separating ammonolysis products includes: pre-separating the ammonolysis products to obtain a pre-separated product and a stream containing ammonia and hydrogen, wherein the stream containing ammonia and hydrogen is returned to step (1) as recycled ammonia and hydrogen; and then separating the pre-separated product to obtain a C6 amine stream containing hexamethylenediamine, a component with a boiling point of 230-300°C, and a heavy component.

[0025] According to the present invention, in order to ensure the effective recovery rate of hydrogen and ammonia, reduce losses caused by hydrogen and ammonia being carried into subsequent equipment, and reduce overall energy consumption, the pre-separation method is preferably selected from at least one of flash evaporation, distillation separation, and membrane separation. The pre-separation method can include at least two stages of flash evaporation, with the flash pressure decreasing in a gradient from 1-6 MPaG to 0.1-4 MPaG. The pre-separation method can also be a combination of at least one stage of flash evaporation and distillation, with the flash pressure decreasing in a gradient from 1-6 MPaG to 0.1-4 MPaG, and the liquid phase after flash evaporation then undergoing distillation. The distillation operating conditions include: a theoretical plate number of 6-20 and a pressure of 0-3 MPaG. Using the above-described pre-separation method, the hydrogen recovery rate is preferably greater than 99%, and the ammonia recovery rate is preferably greater than 98%.

[0026] Although the ammonolysis process consumes ammonia, and some hydrogen is lost during the hydrogen and ammonia recovery process, in order to ensure the weight ratio of hydrogen and ammonia to high-boiling-point amines during the ammonolysis process, fresh hydrogen and fresh ammonia are also added while returning the recovered hydrogen and ammonia to step (1).

[0027] According to the present invention, preferably, the pre-separated product is separated at least once in a distillation column, and the conditions for separating the pre-separated product include: a theoretical plate number of 10-50 and a pressure of -0.1 MPaG to 1 MPaG.

[0028] According to the present invention, preferably, the C6 amine stream containing hexamethylenediamine contains hexamethylenediamine and at least one of cyclohexylimine, aminohexanol and hexanediol; more preferably, the C6 amine stream containing hexamethylenediamine contains, excluding the solvent, 30-80% by weight of hexamethylenediamine, 10-60% by weight of cyclohexylimine, 0-10% by weight of aminohexanol and 0-40% by weight of hexanediol.

[0029] The ammonolysis products can be pre-separated and separated as described above, or they can be directly fed into the ammonia hydrogen recovery unit for the preparation of hexanediamine from hexanediol for pre-separation and separation.

[0030] In this invention, the ammonolysis catalyst can be prepared by the following method:

[0031] (1) Preparation of carrier: A mixture of boehmite, silica sol and calcium nitrate is contacted with an aqueous solution containing nitric acid and phosphoric acid, and then kneaded, dried and calcined in sequence;

[0032] (2) The carrier is immersed in an aqueous solution containing nickel sulfate, lanthanum acetate and indium nitrate, dried at 100-140℃ for 2-6 hours, and then calcined at 350-450℃ for 2-6 hours.

[0033] According to the preparation method of the ammonolysis catalyst of this invention, preferably, in step (1), the amount of silica sol is 0.6-0.8g, the amount of calcium nitrate is 0.1-0.4g, and the amount of aqueous solution containing nitric acid and phosphoric acid is 0.2-0.5g, relative to each gram of boehmite.

[0034] According to the preparation method of the ammonolysis catalyst of the present invention, preferably, in step (1), the aqueous solution containing nitric acid and phosphoric acid has a nitric acid content of 10-25% by weight and a phosphoric acid content of 5-15% by weight.

[0035] According to the preparation method of the ammonolysis catalyst of the present invention, preferably, in step (1), the drying temperature is 100-140℃ and the drying time is 1-6h.

[0036] According to the preparation method of the ammonolysis catalyst of the present invention, preferably, in step (2), the amount of nickel sulfate is 0.6-0.85g, the amount of lanthanum acetate is 0.06-0.08g, and the amount of indium nitrate is 0.055-0.065g relative to each gram of support.

[0037] According to the preparation method of the ammonolysis catalyst of the present invention, preferably, in step (2), the concentration of nickel sulfate in the aqueous solution containing nickel sulfate, lanthanum acetate and indium nitrate is 20-25% by weight, the concentration of lanthanum acetate is 1.5-2.5% by weight, and the concentration of indium nitrate is 1.5-2.5% by weight. The impregnation method is preferably an equal-volume impregnation method, and the impregnation can be carried out in multiple stages.

[0038] A second aspect of the present invention provides a system for preparing hexamethylenediamine by ammonolysis in the first aspect. The system comprises: an ammonolysis reactor 1 for ammonolyzing a high-boiling-point amine to obtain an ammonolysis product; a pre-separation unit 2 for separating ammonia and hydrogen from the ammonolysis product to obtain a pre-separated product and a stream containing ammonia and hydrogen; and an ammonolysis product purification unit 4 for separating the pre-separated product to obtain a C6 amine stream containing hexamethylenediamine, a component with a boiling point of 230-300°C, and a heavy component.

[0039] According to the present invention, preferably, the pre-separation unit 2 further includes a hydrogen compressor for compressing hydrogen.

[0040] The following combination Figure 1The method and system operation of preparing hexamethylenediamine by ammonolysis according to the present invention are described as follows: Solvent 17 and high-boiling-point amine 11 are fed into ammonolysis reactor 1 for ammonolysis reaction to obtain ammonolysis product. The ammonolysis product is sent to pre-separation unit 2 for pre-separation to recover hydrogen and ammonia from the ammonolysis product. The pre-separated product and the material containing hydrogen and ammonia are separated. The material containing hydrogen and ammonia is condensed to obtain liquid ammonia and gaseous hydrogen. The liquid ammonia and the replenished fresh ammonia 13 are directly returned to ammonolysis reactor 1. The gaseous hydrogen and the fresh hydrogen 12 are compressed by hydrogen compressor 3 and then returned to ammonolysis reactor 1. The pre-separated product is sent to ammonolysis product purification unit 4 for separation to obtain C6 amine stream 14 containing hexamethylenediamine, component 15 with a boiling point of 230-300℃ and heavy component 16. Component 15 with a boiling point of 230-300℃ is directly returned to ammonolysis reactor 1.

[0041] According to the present invention, there is no particular limitation on the type of ammonolysis reactor, as long as it enables ammonolysis to proceed. Preferably, the ammonolysis reactor is selected from at least one of fixed bed, autoclave and trickle bed, but it can also be other reactors that ensure stable operation of the reaction.

[0042] The present invention will be described in detail below through embodiments. In the following embodiments,

[0043] C12 amine conversion rate:

[0044] C6 amine selectivity:

[0045]

[0046] Preparation Example 1

[0047] Preparation of ammonolysis catalysts via a multi-step impregnation method:

[0048] (1) Weigh the pseudoboehmite (produced by the aluminum sulfate method, with a specific surface area of ​​310 m²). 2 The mixture consisted of 94.2 g of a mixture with a pore volume of 1.19 ml / g, 72.5 g of silica sol (JN-40), and 25.26 g of calcium nitrate tetrahydrate. The pseudoboehmite was placed in a kneader. The weighed silica sol and calcium nitrate tetrahydrate were added to 24.77 g of water to prepare a solution, which was then added to the kneader and thoroughly stirred with the pseudoboehmite. An aqueous solution consisting of 16.51 g of water, 4.71 g of nitric acid, and 2.83 g of phosphoric acid was then added and thoroughly stirred. The mixture was then kneaded and extruded into a clover shape, dried at 120°C for 4 hours, and then calcined in a muffle furnace at 900°C for 6 hours. After cooling, the carrier was obtained.

[0049] (2) Add 100.77g of nickel sulfate hexahydrate (industrial grade, purity 98%), 5.69g of lanthanum acetate monohydrate and 5.96g of indium nitrate pentahydrate to 134.78mL of water to prepare an aqueous solution. Load the solution onto the 73.25g carrier obtained in step (1) using the equal volume impregnation method in two separate steps. After each impregnation, dry at 120℃ for 4 hours. After the two impregnations are completed, calcine at 390℃ for 4 hours.

[0050] Example 1

[0051] This embodiment is used to illustrate the use of... Figure 1 The process shown is used to prepare hexamethylenediamine.

[0052] A high-boiling-point amine was isolated from the product of hexanediamine preparation by ammoniation of hexanediol. The boiling point of the high-boiling-point amine was 230-300℃. The content of C12 amine in the high-boiling-point amine was 77.2% by weight, the content of aminohexanol was 0.3% by weight, and the content of hexanediol was 11.5% by weight.

[0053] (1) After dissolving the high-boiling-point amine in the solvent 1,4-dioxane, it was mixed with ammonia and hydrogen and heated to 170°C and pressurized to 12 MPaG. The mixture was then fed into an ammonolysis reactor 1 packed with the ammonolysis catalyst of Preparation Example 1 and subjected to ammonolysis under hydrogen conditions to obtain the ammonolysis product. The weight ratio of ammonia to high-boiling-point amine was 7.9:1, the weight ratio of hydrogen to high-boiling-point amine was 0.05:1, and the liquid hourly space velocity (LHSV) of the feed was 0.8 h⁻¹ based on the high-boiling-point amine. -1 The concentration of the high-boiling-point amine in the mixture of the high-boiling-point amine and the solvent was 64.1% by weight.

[0054] (2) The ammonolysis products are sent to the pre-separation unit 2 for pre-separation to obtain liquid products and gaseous phases containing ammonia and hydrogen. The gaseous phase containing ammonia and hydrogen is condensed to obtain hydrogen (gas phase) and recycled ammonia (liquid phase). The hydrogen and replenished fresh hydrogen are compressed to obtain recycled hydrogen. The recycled ammonia, recycled hydrogen and replenished fresh ammonia are returned to the ammonolysis reactor 1. The specific process of pre-separation is as follows: The ammonolysis products are sequentially passed through 3 flash tanks for 3-stage vacuum flash evaporation to recover hydrogen. The pressures of the first to the third flash tanks are set to 9 MPaG, 5 MPaG and 2 MPaG respectively. The gaseous phases at the top of the three flash tanks are cooled to 45°C and then separated into gas and liquid phases. The gaseous phases obtained from the gas-liquid separation are pressurized to the ammoniation reaction pressure and returned to the ammonolysis reactor. The liquid phases obtained from the gas-liquid separation are returned to each stage of vacuum flash tank. The liquid phase at the bottom of the third vacuum flash tank enters the deammoniation distillation column from the top of the deammoniation distillation column for distillation. The deammoniation distillation column has 15 trays and the operating pressure at the top is 2 MPaG. For energy saving and consumption reduction, no condenser is installed at the top of the deammoniation distillation column. The material at the top of the column is sent back to the inlet of the ammonium hydrolysis reactor, and the material at the bottom of the column is subjected to subsequent purification.

[0055] The bottom feed from the deammoniation distillation column is sent to the ammonolysis product refining unit 4 for separation to obtain a C6 amine stream containing hexamethylenediamine, a component with a boiling point of 230-300℃, and a heavy component. Specifically, the bottom feed from the deammoniation distillation column is sent to a roughing column for distillation. A C6 amine stream containing hexamethylenediamine is obtained at the top of the column. The component with a boiling point of 230-300℃ is collected from the side stream, while the heavy component (boiling point above 300℃) is discharged from the bottom. The operating conditions of the roughing column include a bottom temperature of 223.4℃, a reflux ratio of 6, a top operating pressure of -0.09 MPaG, and 40 trays. The component with a boiling point of 230-300℃ is returned to step 1 for further ammonolysis.

[0056] The component with a boiling point of 230-300℃ contains 1.4 wt% hexanediol, 98.2 wt% C12 amine, and 0.4 wt% other components.

[0057] The C6 amine stream containing hexamethylenediamine contained 36.6 wt% hexamethylenediamine, 19.1 wt% cycloheximine, 0.3 wt% aminohexanol, 10.2 wt% hexanediol, 30.5 wt% solvent, and 3.3 wt% other components. The hexamethylenediamine stream was fed into a purification column for purification, and the hexamethylenediamine product (99.5 wt% purity) was collected at the top of the column.

[0058] The system ran continuously until it reached a stable state, with a high-boiling-point amine conversion rate of 72.9% and a C6 amine selectivity of 83.6%.

[0059] Example 2

[0060] The method of Example 1 was followed, except that the composition of the high-boiling-point amine was different, wherein the content of C12 amine was 67.1% by weight, the content of aminohexanol was 0.5% by weight, and the content of hexanediol was 16.4% by weight.

[0061] The ammonolysis product purification unit (4) separates the product into a stream containing hexamethylenediamine, a component with a boiling point of 230-300℃, and a heavy component. The operating conditions of the crude fractionation column include a bottom temperature of 230.5℃, a reflux ratio of 5, an operating pressure of -0.09MPaG at the top of the column, and 36 trays.

[0062] The component with a boiling point of 230-300℃ contains 0.3% by weight of hexanediol, 98.9% by weight of C12 amine, and 0.8% by weight of other components.

[0063] The C6 amine stream containing hexamethylenediamine contained 39.9 wt% hexamethylenediamine, 12.7 wt% cycloheximine, 0.5 wt% aminohexanol, 16.1 wt% hexanediol, 24.2 wt% solvent, and 6.6 wt% other components.

[0064] The system ran continuously until it reached a stable state, with a high-boiling-point amine conversion rate of 67.1% and a C6 amine selectivity of 78.3%.

[0065] The preferred embodiments of the present invention have been described in detail above; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combinations of various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.

Claims

1. A process for the production of hexamethylenediamine by aminolysis, characterized in that, The method includes the following steps: (1) A high-boiling-point amine with a boiling point above 200℃ is subjected to ammonolysis to obtain ammonolysis products; wherein, the content of C12 amine in the high-boiling-point amine is 40-99% by weight, the total content of cyclohexylimine and aminohexanol is 0-10% by weight, and the content of hexanediol is 0-30% by weight; wherein, the source of the high-boiling-point amine is the ammonolysis product generated by the ammonolysis of hexanediol, after removing hexanediamine, ammonia and hydrogen, as well as most of the cyclohexylimine and aminohexanol, the remaining components; (2) Separate the ammonolysis product to obtain a C6 amine stream containing hexamethylenediamine, a component with a boiling point of 230-300℃ and a heavy component, and then return the component with a boiling point of 230-300℃ to step (1) to continue ammonolysis; C6 amines refer to amine compounds with 6 carbon atoms, and C12 amines refer to amine compounds with 12 carbon atoms. The ammonolysis catalyst was prepared according to the following method: (1) Preparation of carrier: The mixture of boehmite, silica sol and calcium nitrate is contacted with an aqueous solution containing nitric acid and phosphoric acid, and then kneaded, dried and calcined in sequence; (2) The carrier is immersed in an aqueous solution containing nickel sulfate, lanthanum acetate and indium nitrate, dried at 100-140℃ for 2-6 hours, and then calcined at 350-450℃ for 2-6 hours.

2. The method of claim 1, wherein, High-boiling-point amines have boiling points of 200-400℃.

3. The method of claim 2, wherein, High-boiling-point amines have a boiling point of 230-300℃.

4. The method of claim 1, wherein, Ammonolysis is carried out in the presence of ammonia and hydrogen, with the weight ratio of ammonia to high-boiling-point amines being 3.5-12:1 and the weight ratio of hydrogen to high-boiling-point amines being 0.01-0.2:

1.

5. The method of claim 4, wherein, Ammonolysis is carried out in the presence of ammonia and hydrogen, with the weight ratio of ammonia to high-boiling-point amines being 6-9.5:1 and the weight ratio of hydrogen to high-boiling-point amines being 0.02-0.1:

1.

6. The method of claim 1, wherein, The temperature for ammonolysis is 140-260℃; the pressure for ammonolysis is 10-24 MPaG; and the liquid hourly space velocity (LHSV) for high-boiling-point amines is 0.05-7 h⁻¹. -1 .

7. The method according to claim 6, wherein, The temperature for ammonolysis is 150-255℃; the pressure for ammonolysis is 11-22 MPaG; and the liquid hourly space velocity (LHSV) for high-boiling-point amines is 0.09-1.9 h⁻¹. -1 .

8. The method of claim 1, wherein, The ammonolysis reaction is carried out in the presence of a solvent, and the concentration of the high-boiling amine in the mixture of the high-boiling amine and the solvent is 30-80% by weight.

9. The method of claim 8, wherein, The solvent is selected from at least one of tetrahydrofuran, 1,4-dioxane, n-hexane, and cyclohexane.

10. The method of claim 4, wherein, The method for separating ammonolysis products includes: pre-separating the ammonolysis products to obtain pre-separated products and a stream containing ammonia and hydrogen, wherein the stream containing ammonia and hydrogen is returned to step (1) as recycled ammonia and hydrogen; and then separating the pre-separated products to obtain a C6 amine stream containing hexamethylenediamine, a component with a boiling point of 230-300℃, and a heavy component.

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