Process and system for preparing mixed diamine through catalytic hydrogenation

Abstract

The invention relates to the technical field of organic matter preparation, in particular to a process and system for preparing mixed diamine through catalytic hydrogenation.The process comprises the following steps that a nickel-based catalyst is prepared into a catalyst solution through methyl alcohol, mixed dinitrobenzene, methyl alcohol and the catalyst solution are sequentially added into a hydrogenation reaction kettle, hydrogen is compressed to 1.6-1.8 MPa and then introduced into the hydrogenation reaction kettle, and the mixed dinitrobenzene and the methyl alcohol are added into the hydrogenation reaction kettle; and controlling the reaction temperature and pressure, reacting for 4-8 hours to obtain a reducing solution, separating the reducing solution from the catalyst, dealcoholizing, and purifying to obtain a mixed diamine product. According to the nickel-based catalyst, the selectivity of catalytic hydrogenation reaction can be improved, the catalytic activity of the catalyst is improved, and the catalytic hydrogenation reaction can be carried out at lower temperature and pressure, so that the energy consumption and the cost are reduced.

Description

Technical Field

[0001] The invention relates to the technical field of organic matter preparation, and in particular to a process and a system for preparing mixed diamines by catalytic hydrogenation. Background Art

[0002] Mixed diamines, also known as phenylenediamines, are an important class of aromatic diamine organic compounds with three isomers, namely o-phenylenediamine (1,2-phenylenediamine), m-phenylenediamine (1,3-phenylenediamine) and p-phenylenediamine (1,4-phenylenediamine). Mixed diamines are often used as dye intermediates, mainly for the synthesis of aramid, azo dyes, sulfur dyes and acid dyes. In addition to the dye field, the polymerization products of mixed diamines can enhance the toughness, heat resistance and chemical stability of materials, and are thus widely used in rubber, plastics, coatings and other fields. In addition, mixed diamines are also key ingredients in the production of fur dyes, rubber antioxidants and photo developers.

[0003] In the prior art, Raney nickel or nickel is often used as a catalyst for hydrogenation reduction to produce phenylenediamine. However, the preparation of Raney nickel catalyst usually involves the reaction of nickel-aluminum alloy with concentrated sodium hydroxide solution, which produces a large amount of waste water and waste residue. In addition, Raney nickel catalyst is easily oxidized and burned in the air, which increases the cost of use and safety risks. In practical use, nickel catalyst is prone to deactivation, and it is difficult to recycle scrapped nickel catalyst, and the catalytic efficiency of nickel catalyst is low. Summary of the invention

[0004] In order to solve the problems mentioned in the above background technology, the present invention provides a process and system for preparing mixed diamines by catalytic hydrogenation.

[0005] In order to achieve the above object, the present invention adopts the following technical solutions: A process for preparing mixed diamines by catalytic hydrogenation comprises the following steps: Mixed dinitrobenzene (including 90-92% of m-dinitrobenzene, 7-8% of o-dinitrobenzene and 2-3% of p-dinitrobenzene), methanol and nickel-based catalyst are sequentially added into a hydrogenation reactor, hydrogen is compressed to 1.6-1.8MPa and then introduced into the hydrogenation reactor, the reaction temperature and pressure are controlled, and the reaction is carried out for 4-8h to obtain a reducing liquid, and the reducing liquid after reduction is separated and recovered from the catalyst by a cross-flow circulation group, and the catalyst is returned to the catalyst mixing kettle for recycling, and the reducing liquid containing alcohol is distilled at normal pressure to recover methanol for recycling, and after distillation and purification at normal pressure, a mixed diamine product is obtained.

[0006] Further, the nickel-based catalyst comprises the following steps to prepare: S1, adding polyvinyl pyrrolidone and N, N-dimethylformamide into a reaction kettle, introducing nitrogen protection, heating, adding 4-picolinic acid and dicyclohexylcarbodiimide while hot, continuing to stir and react, cooling to room temperature after the reaction is completed, filtering, and obtaining a graft copolymer solution; S2. Transfer the graft copolymer solution to another reactor, add water to dilute to 10-20%, add nickel sulfate (NiSO4·6H2O) under stirring, adjust the pH value, heat up and stir to react, cool to room temperature, add sodium dodecyl sulfate, continue stirring for 15-20 minutes, let stand for 1-3 hours, centrifuge, wash, and dry to obtain a nickel-based catalyst.

[0007] Furthermore, the feed mass ratio of mixed dinitrobenzene, methanol and nickel-based catalyst is (5-6):(2-4):(1-3).

[0008] Furthermore, the reaction temperature is 45-105°C and the pressure is 0.6-1.8MPa.

[0009] Furthermore, in step S1, the heating temperature is 40-50° C., the heating time is 30-60 min, the stirring speed is 50-100 rpm, and the stirring reaction time is 2-4 h.

[0010] Furthermore, in step S1, the mass ratio of polyvinyl pyrrolidone, N,N-dimethylformamide, 4-picolinic acid and dicyclohexylcarbodiimide is (1.5-1.9):5:(2-2.5):(0.1-0.3).

[0011] Furthermore, in step S2, the mass ratio of the graft copolymer solution, nickel sulfate and sodium dodecyl sulfate is (1-3): (6-10): (0.05-0.1).

[0012] Furthermore, in step S2, the pH value is adjusted to 7.0-8.0, the heating temperature is 70-80° C., the stirring speed is 100-200 rpm, and the stirring reaction time is 3-6 h.

[0013] According to another aspect of the present invention, there is provided a system for preparing mixed diamines by catalytic hydrogenation, comprising a catalyst preparation unit, a hydrogen compression unit, a hydrogenation reaction unit, a catalyst recovery unit and a dealcoholization unit, wherein the catalyst preparation unit comprises a feeding hopper, a catalyst kettle and a catalyst mixing kettle, the hydrogen compression unit comprises a hydrogen compressor, the hydrogenation reaction unit comprises at least one hydrogenation reactor, the catalyst recovery unit comprises a catalyst settler and a cross-flow circulation group, and the dealcoholization unit comprises a de-methanolation tower.

[0014] Beneficial effects of the present invention: 1. In the nickel-based catalyst prepared by the present invention, polyvinyl pyrrolidone-4-pyridine carboxylic acid graft copolymer is used as a carrier and a ligand to effectively load nickel sulfate as a catalytic active center. This composite catalyst system shows excellent stability and dispersibility in catalytic hydrogenation reactions, and significantly improves the catalytic activity of nickel ions. Nickel ions are uniformly dispersed in the graft copolymer matrix through coordination or chelation, effectively avoiding agglomeration, and ensuring the high utilization rate and catalytic activity of nickel ions. The complex network structure formed by the graft copolymer not only provides abundant binding sites for nickel ions, but also enhances the dispersibility of the catalyst. At the same time, the polymer chain of polyvinyl pyrrolidone effectively resists the agglomeration and deactivation of the catalyst during the reaction, and the rich pore structure inside the catalyst greatly promotes the diffusion and mass transfer of reactant molecules, increases the contact area between the active site and the reactant molecules, thereby improving the service life of the catalyst and the selectivity of the mixed diamine.

[0015] 2. In the technical solution of the present invention, the nickel-based catalyst changes the reaction path and improves the selectivity of the catalytic hydrogenation reaction by interacting with the reactants. Among them, the 4-pyridine carboxylic acid ligand can stabilize the reaction intermediates, thereby promoting the formation of the target product mixed diamine. In addition, the nickel-based catalyst prepared by the present invention can inhibit particle agglomeration while having stable active sites, prolonging the service life of the catalyst and reducing the frequency and cost of replacing the catalyst. DETAILED DESCRIPTION

[0016] The technical solution of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0017] Unless otherwise specified, the raw materials used in the present invention are all from conventional products purchased from the market. Nickel sulfate is nickel sulfate hexahydrate, and polyvinyl pyrrolidone is PVP-K30.

[0018] Preparation Example 1 The nickel-based catalyst is prepared by the following steps: S1, add 1.5kg polyvinyl pyrrolidone and 5kg N,N-dimethylformamide into a reaction kettle, introduce nitrogen protection, heat at 40°C for 30min, add 2kg 4-picolinic acid and 0.1kg dicyclohexylcarbodiimide while hot, continue stirring at 50rpm for 2h, after the reaction is completed, cool to room temperature, filter, and obtain a graft copolymer solution; S2. Transfer 1 kg of the graft copolymer solution to another reactor, add water to dilute it to 10% of the original volume, add 6 kg of nickel sulfate while stirring, adjust the pH value to 7.0, heat to 70 ° C and stir at 100 rpm for 3 hours, cool to room temperature, add 0.05 kg of sodium dodecyl sulfate, continue stirring for 15 minutes, let stand for 1 hour, centrifuge, wash, and dry to obtain a nickel-based catalyst.

[0019] Preparation Example 2 The nickel-based catalyst is prepared by the following steps: S1, 1.7 kg polyvinyl pyrrolidone and 5 kg N, N-dimethylformamide were added to a reaction kettle, nitrogen was introduced for protection, and the reaction kettle was heated at 45 ° C for 45 min. 2.2 kg 4-picolinic acid and 0.2 kg dicyclohexylcarbodiimide were added while hot, and the reaction was continued at a stirring speed of 60 rpm for 3 h. After the reaction was completed, the reaction kettle was cooled to room temperature and filtered to obtain a graft copolymer solution; S2. Transfer 2 kg of the graft copolymer solution to another reactor, add water to dilute it to 12% of the original volume, add 7 kg of nickel sulfate while stirring, and adjust the pH value to 7.5, raise the temperature to 75 ° C and stir at a speed of 150 rpm for 4 hours, cool to room temperature, add 0.08 kg of sodium dodecyl sulfate, continue stirring for 18 minutes, let it stand for 2 hours, centrifuge, wash, and dry to obtain a nickel-based catalyst.

[0020] Preparation Example 3 The nickel-based catalyst is prepared by the following steps: S1, 1.9 kg polyvinyl pyrrolidone and 5 kg N, N-dimethylformamide were added to a reaction kettle, nitrogen was introduced for protection, and the mixture was heated at 50° C. for 60 min. 2.5 kg 4-pyridinecarboxylic acid and 0.3 kg dicyclohexylcarbodiimide were added while hot, and the mixture was stirred at 100 rpm for 4 h. After the reaction was completed, the mixture was cooled to room temperature and filtered to obtain a graft copolymer solution; S2. Transfer 3 kg of the graft copolymer solution to another reactor, add water to dilute it to 20% of the original volume, add 10 kg of nickel sulfate while stirring, adjust the pH value to 8.0, heat to 80 ° C and stir at 200 rpm for 6 hours, cool to room temperature, add 0.1 kg of sodium dodecyl sulfate, continue stirring for 20 minutes, let stand for 3 hours, centrifuge, wash, and dry to obtain a nickel-based catalyst. Example 1

[0021] A process for preparing mixed diamines by catalytic hydrogenation comprises the following steps: 5 kg of mixed dinitrobenzene (90.1% of m-dinitrobenzene, 7.4% of o-dinitrobenzene, and 2.5% of p-dinitrobenzene), 2 kg of methanol and 1 kg of the nickel-based catalyst prepared in Example 1 were added to a hydrogenation reactor in sequence. The hydrogen was compressed to 1.6 MPa and then introduced into the hydrogenation reactor. The reaction temperature was controlled to 45° C. and the pressure was 0.6 MPa. The reaction was carried out for 4 hours to obtain a reduced liquid. After the reduction, the reduced liquid was separated and recovered from the catalyst by a cross-flow circulation group. The catalyst was returned to the catalyst mixing kettle for recycling. The reduced liquid containing alcohol was distilled at normal pressure to recover methanol for recycling. After distillation and purification at normal pressure, a mixed diamine product was obtained. Example 2

[0022] A process for preparing mixed diamines by catalytic hydrogenation comprises the following steps: 5.4 kg of mixed dinitrobenzene (90.2% of m-dinitrobenzene, 7.1% of o-dinitrobenzene, 2.7% of p-dinitrobenzene), 2.45 kg of methanol and 1.9 kg of the nickel-based catalyst prepared in Example 2 were added to the hydrogenation reactor in sequence, and the hydrogen was compressed to 1.7 MPa and then introduced into the hydrogenation reactor. The reaction temperature was controlled to be 70° C. and the pressure was 1.0 MPa. The reaction was carried out for 6 hours to obtain a reduced liquid. After the reduction, the reduced liquid was separated and recovered from the catalyst by a cross-flow circulation group. The catalyst was returned to the catalyst mixing kettle for recycling. The reduced liquid containing alcohol was distilled at normal pressure to recover methanol for recycling. After distillation and purification at normal pressure, a mixed diamine product was obtained. Example 3

[0023] A process for preparing mixed diamines by catalytic hydrogenation comprises the following steps: 5.5 kg of mixed dinitrobenzene (90.0% of m-dinitrobenzene, 7.2% of o-dinitrobenzene, and 2.8% of p-dinitrobenzene), 2.5 kg of methanol and 2 kg of the nickel-based catalyst prepared in Example 2 were added to a hydrogenation reactor in sequence. The hydrogen was compressed to 1.7 MPa and then introduced into the hydrogenation reactor. The reaction temperature was controlled to 80° C. and the pressure was 1.2 MPa. The reaction was carried out for 6 hours to obtain a reduced liquid. After reduction, the reduced liquid was subjected to catalyst separation and recovery through a cross-flow circulation group. The catalyst was returned to the catalyst mixing kettle for recycling. The reduced liquid containing alcohol was subjected to atmospheric distillation to recover methanol for recycling. After distillation and purification under atmospheric pressure, a mixed diamine product was obtained. Example 4

[0024] A process for preparing mixed diamines by catalytic hydrogenation comprises the following steps: 6 kg of mixed dinitrobenzene (90.7% of m-dinitrobenzene, 7.2% of o-dinitrobenzene, and 2.1% of p-dinitrobenzene), 4 kg of methanol and 3 kg of the nickel-based catalyst prepared in Example 3 were added to a hydrogenation reactor in sequence. The hydrogen was compressed to 1.8 MPa and then introduced into the hydrogenation reactor. The reaction temperature was controlled to be 102° C. and the pressure was 1.8 MPa. The reaction was carried out for 8 hours to obtain a reduced liquid. After reduction, the reduced liquid was subjected to catalyst separation and recovery through a cross-flow circulation group. The catalyst was returned to the catalyst mixing kettle for recycling. The reduced liquid containing alcohol was subjected to atmospheric distillation to recover methanol for recycling. After distillation and purification under atmospheric pressure, a mixed diamine product was obtained.

[0025] Comparative Example 1 The difference between this comparative example and Example 1 is that nickel sulfate is used instead of the nickel-based catalyst prepared in the Preparation Example, and the remaining steps are the same as those in Example 1.

[0026] Comparative Example 2 The difference between this comparative example and Example 2 is that 4-pyridinecarboxylic acid is used instead of the nickel-based catalyst prepared in the preparation example, and the remaining steps are the same as those in Example 2.

[0027] Comparative Example 3 The difference between this comparative example and Example 3 is that Raney nickel is used instead of the nickel-based catalyst prepared in the Preparation Example, and the remaining steps are the same as those in Example 3.

[0028] The specifications of the nickel-based catalysts prepared in Preparation Examples 1-3 are shown in Table 1: Table 1. Specifications of the nickel-based catalysts of Preparation Examples 1-3

[0029] serial number Nickel crystal size (µm) <![CDATA[Specific surface area (m 2 / g)]]> <![CDATA[Bulk density (g / cm 3 ).]]> Pore ​​volume (mL / g) Preparation Example 1 <![CDATA[6.2×10 -3 ]]> 157 0.68 0.49 Preparation Example 2 <![CDATA[6.2×10 -3 ]]> 152 0.66 0.51 Preparation Example 3 <![CDATA[6.1×10 -3 ]]> 163 0.67 0.56 The yield and purity of Examples 1-3 and Comparative Examples 1-3 are shown in Table 2: Table 2. Purity and yield results of Examples 1-4 and Comparative Examples 1-3

[0030] serial number Yield (%) purity(%) Example 1 92.5 99.1 Example 2 92.6 99.1 Example 3 93.1 99.2 Example 4 93.4 99.2 Comparative Example 1 62.7 80.9 Comparative Example 2 69.2 86.3 Comparative Example 3 89.3 99.2

[0031] As shown in Table 1, the nickel crystal size of the nickel-based catalysts in Preparation Examples 1-3 is maintained at the nanometer level, the nickel crystal size of Preparation Examples 1-3 changes slightly but is generally stable, and the specific surface area shows certain fluctuations, but is maintained at a high level, which is conducive to providing more active sites for reactant molecules to adsorb and react. Bulk density and pore volume jointly affect the mass transfer efficiency and reaction kinetics of the catalyst.

[0032] As shown in Table 2, the catalytic hydrogenation reaction of the nickel-based catalyst obtained in the preparation examples of Examples 1-4 all achieved a high yield and purity. Comparative Examples 1-3 use different catalysts to significantly affect the performance of catalytic hydrogenation reactions. Comparative Example 1 uses nickel sulfate as a catalyst, and the yield and purity are greatly reduced, which may be because nickel sulfate itself does not have efficient catalytic activity and cannot provide stable nano-scale nickel crystals and abundant active sites like homemade nickel-based catalysts. Comparative Example 2 uses 4-pyridinecarboxylic acid as a catalyst. Although it contains certain catalytically active components (such as pyridine rings), the yield and purity are still low, which may be because its catalytic activity is far less than that of the nickel-based catalyst in the preparation example. Comparative Example 3 uses Raney nickel as a catalyst, and the yield is improved but still lower than that of the homemade nickel-based catalyst, while the purity is comparable to that of the embodiment, which may be because although Raney nickel is also a commonly used hydrogenation catalyst, its catalytic activity and selectivity may not be as good as those of specially designed homemade nickel-based catalysts.

[0033] In summary, the nickel-based catalyst prepared in Preparation Examples 1-3 exhibits a significant catalytic effect in the production of mixed diamines, so that the mixed diamines prepared in Examples 1-4 have higher purity and yield.

[0034] In the description of the specification, the description with reference to the terms "preparation example", "embodiment", "various embodiments" and the like means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or preparation example are included in at least one embodiment or preparation example of the present invention. In this specification, the schematic representation of the above terms does not necessarily refer to the same embodiment or preparation example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or preparation examples in a suitable manner.

[0035] The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can make equivalent replacements or changes according to the technical scheme and inventive concept of the present invention within the technical scope disclosed by the present invention, which should be covered by the protection scope of the present invention.

Claims

1. A process for preparing mixed diamines by catalytic hydrogenation, characterized in that: The following steps are involved: Add mixed dinitrobenzene, methanol and nickel-based catalyst to a hydrogenation reactor in sequence, compress hydrogen to 1.6-1.8 MPa and then pass it into the hydrogenation reactor, control the reaction temperature and pressure, react for 4-8 hours to obtain a reduced liquid, separate the reduced liquid from the catalyst, dealcoholize and purify to obtain a mixed diamine product; Among them, nickel-based catalyst The method comprises the following steps: S1, adding polyvinyl pyrrolidone and N, N-dimethylformamide into a reaction kettle, introducing nitrogen protection, heating, adding 4-picolinic acid and dicyclohexylcarbodiimide while hot, continuing to stir and react, cooling to room temperature after the reaction is completed, filtering, and obtaining a graft copolymer solution; S2. Transfer the graft copolymer solution to another reactor, add water to dilute to 10-20%, add nickel sulfate while stirring, adjust the pH value, heat and stir to react, cool to room temperature, add sodium dodecyl sulfate, continue stirring for 15-20 minutes, let stand for 1-3 hours, centrifuge, wash, and dry to obtain a nickel-based catalyst.

2. A process for preparing mixed diamines by catalytic hydrogenation according to claim 1, characterized in that: The feed mass ratio of mixed dinitrobenzene, methanol and nickel-based catalyst is (5-6):(2-4):(1-3).

3. A process for preparing mixed diamines by catalytic hydrogenation according to claim 1, characterized in that: The reaction temperature is 45-102°C and the pressure is 0.6-1.8MPa.

4. A process for preparing mixed diamines by catalytic hydrogenation according to claim 1, characterized in that: In step S1, the heating temperature is 40-50° C., the heating time is 30-60 min, the stirring speed is 50-100 rpm, and the stirring reaction time is 2-4 h.

5. The process for preparing mixed diamines by catalytic hydrogenation according to claim 1, characterized in that: In step S1, the mass ratio of polyvinyl pyrrolidone, N,N-dimethylformamide, 4-picolinic acid and dicyclohexylcarbodiimide is (1.5-1.9):5:(2-2.5):(0.1-0.3).

6. The process for preparing mixed diamines by catalytic hydrogenation according to claim 1, characterized in that: In step S2, the mass ratio of the graft copolymer solution, nickel sulfate and sodium dodecyl sulfate is (1-3): (6-10): (0.05-0.1).

7. The process for preparing mixed diamines by catalytic hydrogenation according to claim 1, characterized in that: In step S2, the pH value is adjusted to 7.0-8.0, the heating temperature is 70-80° C., the stirring speed is 100-200 rpm, and the stirring reaction time is 3-6 hours.

8. A system for preparing mixed diamines by catalytic hydrogenation, using the process for preparing mixed diamines by catalytic hydrogenation as claimed in any one of claims 1 to 7, characterized in that: The invention comprises a catalyst preparation unit, a hydrogen compression unit, a hydrogenation reaction unit, a catalyst recovery unit and a dealcoholization unit, wherein the catalyst preparation unit comprises a feeding hopper, a catalyst kettle and a catalyst mixing kettle, the hydrogen compression unit comprises a hydrogen compressor, the hydrogenation reaction unit comprises at least one hydrogenation reaction kettle, the catalyst recovery unit comprises a catalyst settler and a cross-flow circulation group, and the dealcoholization unit comprises a de-methanolation tower.