Process for rectifying and decoking o-phenylenediamine

Abstract

The invention discloses an o-phenylenediamine rectification decoking process, and belongs to the field of chemical preparation. The method specifically comprises the following steps: rectifying a crude product o-phenylenediamine twice, carrying out condensation recovery on tar containing p-phenylenediamine, carrying out cooling crystallization, carrying out centrifugal collection, adding an antioxidant, melting, and dehydrating to obtain o-phenylenediamine; and centrifuging to obtain a mixed solution containing p-phenylenediamine, crystallizing again to obtain p-phenylenediamine, and recycling waste liquid after solid-liquid separation. The o-phenylenediamine rectification decoking process provided by the invention improves the yield and content of the o-phenylenediamine finished product, does not change color for a long time in an air atmosphere, improves the utilization rate of resources, and has good reference significance and application prospects in industrial production research.

Description

Technical Field

[0001] The invention belongs to the field of chemical preparation, and in particular relates to a process for rectifying and decoking o-phenylenediamine. Background Art

[0002] O-phenylenediamine is a traditional fine chemical intermediate, mainly used in pesticide production, and is a raw material for preparing carbendazim and methyl thiophanate. In the prior art, the mature process route is: using o-nitrochlorobenzene as a raw material, reacting with concentrated ammonia water to generate o-nitroaniline, and then using alkali sulfide to reduce it to o-phenylenediamine. The content of o-phenylenediamine in the crude material prepared by this synthesis process is about 92%, and its impurities mainly include ammonia and alkali sulfide contained in the crystals. The o-nitrochlorobenzene raw material contains a small amount of p-nitrochlorobenzene, which is generated after the reaction, and needs to be refined before it can be used as a chemical raw material.

[0003] Crude amine contains 95% o-phenylenediamine and the rest is 5% tar. Tar is mainly composed of p-phenylenediamine, macromolecular impurities and polymers. Macromolecular impurities and polymers have large molecular weights and high boiling points, which are very different from the boiling points of o-phenylenediamine. They are most easily separated in a high vacuum decoking tower. The boiling point of p-phenylenediamine is similar to that of o-phenylenediamine, which is difficult to separate, but not easy to clog the tower. Since the raw material contains about 5% tar, if it is not treated, the tar will enter the distillation system, causing the packing and internal parts to be clogged. Once the plant is stopped for treatment, it will be very troublesome; at the same time, the melting point of the material is 103°C, and the pipeline is very easy to condense and clog when treated at room temperature. Therefore, a decoking process must be designed to remove the tar before entering the original distillation system.

[0004] The patent application with publication number CN102757351 A discloses a method for continuous purification and refining of o-toluenediamine, which uses two towers in series for distillation, and the crude o-toluenediamine is respectively passed through a low-removal tower to remove the front fraction, and then separated from o-toluenediamine and m-toluenediamine through product tower distillation. The application has a certain purification effect, but in the distillation process, due to the presence of a small amount of p-nitrochlorobenzene in the raw material, a byproduct p-phenylenediamine is generated in the reaction. The amino group in o-phenylenediamine is easily oxidized to generate hydroperoxide in the air, and the generated free radical intermediates will further react to generate various more complex macromolecular impurities. At the same time, o-phenylenediamine will be oxidized to o-phenylenediamine, and then further react with o-phenylenediamine to generate a polymer. Summary of the invention

[0005] The object of the present invention is to provide a process for rectifying and decoking o-phenylenediamine to improve the purity of the finished o-phenylenediamine.

[0006] The purpose of the present invention can be achieved through the following technical solutions:

[0007] A process for decoking o-phenylenediamine by distillation, comprising the following steps:

[0008] S1, cutting the crude o-phenylenediamine into pieces and putting them into a distillation tower for vacuum distillation to remove the front fraction and part of the tar to obtain a crude o-phenylenediamine liquid; the tar contains p-phenylenediamine;

[0009] S2. Under vacuum conditions, placing the crude o-phenylenediamine liquid into a distillation tower for secondary vacuum distillation, condensing and recovering, to obtain liquid o-phenylenediamine;

[0010] S3, mixing liquid o-phenylenediamine with deionized water, heating and stirring under nitrogen protection to obtain an o-phenylenediamine aqueous solution; cooling the o-phenylenediamine aqueous solution for crystallization, centrifuging to obtain crude o-phenylenediamine crystals and a mixed solution containing p-phenylenediamine; melting the crude o-phenylenediamine crystals, heating and stirring under nitrogen protection until completely melted, adding an antioxidant and stirring evenly, and dehydrating to obtain o-phenylenediamine;

[0011] The mixed liquid containing p-phenylenediamine is crystallized again, and p-phenylenediamine and waste liquid are obtained through solid-liquid separation; the waste liquid is recovered and mixed with the liquid o-phenylenediamine in S3 for reuse.

[0012] Furthermore, the distillation temperature in S1 is 125-140°C, and the distillation temperature in S2 is 150-160°C.

[0013] Furthermore, the mass ratio of the liquid o-phenylenediamine to deionized water is 1-1.5:1.5-2.

[0014] Furthermore, the temperature of the cooling crystallization is 50°C to 80°C.

[0015] Furthermore, the antioxidant is one of sodium bisulfite, sodium sulfite and sodium hydrosulfide.

[0016] Furthermore, the mass ratio of the antioxidant to the crude o-phenylenediamine crystals is 0.2-0.4 g:100 g.

[0017] Furthermore, the recrystallization temperature is 45-55°C.

[0018] Beneficial effects of the present invention:

[0019] (1) The o-phenylenediamine distillation and decoking process adopted by the present invention adopts continuous distillation and collects different components according to their different boiling points, which can continuously separate and remove the front fraction and most of the tar, thereby improving the purity of o-phenylenediamine, mainly removing macromolecular substances that are easy to clog the tower, and preventing the distillation system fillers and internals from clogging.

[0020] (2) The present invention adopts a crystallization method to further purify liquid o-phenylenediamine, and can separate o-phenylenediamine and p-phenylenediamine without high temperature, and recover the mixed liquid containing p-phenylenediamine to obtain the p-phenylenediamine product, thereby reducing the loss of o-phenylenediamine in the distillation and decoking process, and also reducing the amount of water used, thereby improving the utilization rate of resources. On the other hand, the purity of o-phenylenediamine is improved while reducing the amount of antioxidant used, which greatly prolongs the time for o-phenylenediamine to turn yellow when exposed to air. DETAILED DESCRIPTION

[0021] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only 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.

[0022] Example 1

[0023] This embodiment provides a process for decoking o-phenylenediamine by distillation, comprising the following steps:

[0024] S1, slice the crude o-phenylenediamine and put it into a distillation tower for vacuum distillation at a distillation temperature of 135° C., remove the front fraction and tar, and obtain a crude o-phenylenediamine liquid; the tar contains p-phenylenediamine;

[0025] S2. Under vacuum conditions, placing the crude o-phenylenediamine liquid into a distillation tower for secondary vacuum distillation at a distillation temperature of 155° C., condensing and recovering to obtain liquid o-phenylenediamine;

[0026] S3, mixing liquid o-phenylenediamine and deionized water in a mass ratio of 1:1.5, heating and stirring under nitrogen protection to obtain an o-phenylenediamine aqueous solution; cooling the o-phenylenediamine aqueous solution at 60° C. for crystallization, centrifuging to obtain crude o-phenylenediamine crystals and a mixed solution containing p-phenylenediamine; melting the crude o-phenylenediamine crystals, heating and stirring under nitrogen protection until completely melted, adding 0.2wt% sodium bisulfite and stirring evenly, and obtaining o-phenylenediamine after dehydration.

[0027] The mixed liquid containing p-phenylenediamine is crystallized again at 45° C., and p-phenylenediamine and waste liquid are obtained through solid-liquid separation; the waste liquid is recovered and mixed with the liquid o-phenylenediamine in S3 for reuse.

[0028] Example 2

[0029] Compared with Example 1, the difference between this embodiment and Example 1 is that the "distillation temperature is 135°C" in S1 is changed to "distillation temperature is 125°C"; the "distillation temperature is 155°C" in S2 is changed to "distillation temperature is 150°C"

[0030] The remaining raw materials and preparation process remain the same as in Example 1.

[0031] Example 3

[0032] The present embodiment is different from the embodiment 1 in that the "distillation temperature is 135° C." in S1 is changed to "distillation temperature is 140° C." and the "distillation temperature is 155° C." in S2 is changed to "distillation temperature is 160° C.".

[0033] The remaining raw materials and preparation process remain the same as in Example 1.

[0034] Example 4

[0035] The present embodiment is different from the embodiment 1 in that the “mass ratio of liquid o-phenylenediamine to deionized water is 1:1.5” in S3 is changed to “mass ratio of liquid o-phenylenediamine to deionized water is 1:2”.

[0036] The remaining raw materials and preparation process remain the same as in Example 1.

[0037] Example 5

[0038] The present embodiment is different from the embodiment 1 in that the “crystallization by cooling down at 60° C.” in S3 is changed to “crystallization by cooling down at 50° C.”

[0039] The remaining raw materials and preparation process remain the same as in Example 1.

[0040] Example 6

[0041] The present embodiment is different from the embodiment 1 in that the “crystallization by cooling down at 60° C.” in S3 is changed to “crystallization by cooling down at 80° C.”

[0042] The remaining raw materials and preparation process remain the same as in Example 1.

[0043] Example 7

[0044] The present embodiment is different from the embodiment 1 in that the sodium bisulfite in S3 is replaced with sodium sulfite.

[0045] The remaining raw materials and preparation process remain the same as in Example 1.

[0046] Example 8

[0047] The present embodiment is different from the embodiment 1 in that the "0.2 wt % sodium bisulfite" in S3 is changed to "0.4 wt % sodium bisulfite".

[0048] The remaining raw materials and preparation process remain the same as in Example 1.

[0049] Comparative Example 1

[0050] S1, slice the crude o-phenylenediamine and put it into a distillation tower for vacuum distillation at a distillation temperature of 135° C., remove the front fraction and tar, and obtain a crude o-phenylenediamine liquid; the tar contains p-phenylenediamine;

[0051] S2, mixing crude o-phenylenediamine liquid with deionized water in a mass ratio of 1:1.5, heating and stirring under nitrogen protection to obtain an o-phenylenediamine aqueous solution; cooling the o-phenylenediamine aqueous solution at 45° C. for crystallization, centrifuging to obtain crude o-phenylenediamine crystals and a mixed solution containing p-phenylenediamine; melting the crude o-phenylenediamine crystals, heating and stirring under nitrogen protection until completely melted, adding 0.2wt% sodium bisulfite and stirring evenly, and obtaining o-phenylenediamine after dehydration.

[0052] The mixed liquid containing p-phenylenediamine is crystallized again at 45° C., and p-phenylenediamine and waste liquid are obtained through solid-liquid separation; the waste liquid is recovered and mixed with the liquid o-phenylenediamine in S3 for reuse.

[0053] Comparative Example 2

[0054] S1, slice the crude o-phenylenediamine and put it into a distillation tower for vacuum distillation at a distillation temperature of 135° C., remove the front fraction and tar, and obtain a crude o-phenylenediamine liquid; the tar contains p-phenylenediamine;

[0055] S2. Under vacuum conditions, placing the crude o-phenylenediamine liquid into a distillation tower for secondary vacuum distillation at a distillation temperature of 155° C., condensing and recovering to obtain liquid o-phenylenediamine; adding 0.2 wt % of sodium bisulfite and stirring evenly, and obtaining o-phenylenediamine after dehydration.

[0056] Comparative Example 3

[0057] S1, slice the crude o-phenylenediamine and put it into a distillation tower for vacuum distillation at a distillation temperature of 135° C., remove the front fraction and tar, and obtain a crude o-phenylenediamine liquid; the tar contains p-phenylenediamine;

[0058] S2. Under vacuum conditions, placing the crude o-phenylenediamine liquid into a distillation tower for secondary vacuum distillation at a distillation temperature of 155° C., condensing and recovering to obtain liquid o-phenylenediamine;

[0059] S3. Mix liquid o-phenylenediamine and deionized water in a mass ratio of 1:1.5, heat and stir under nitrogen protection to obtain an o-phenylenediamine aqueous solution; cool the o-phenylenediamine aqueous solution down at 45° C. for crystallization, centrifuge to obtain crude o-phenylenediamine crystals and a mixed solution containing p-phenylenediamine; melt the crude o-phenylenediamine crystals, heat and stir under nitrogen protection until completely melted, and dehydrate to obtain o-phenylenediamine.

[0060] The mixed liquid containing p-phenylenediamine is crystallized again at 45° C., and p-phenylenediamine and waste liquid are obtained through solid-liquid separation; the waste liquid is recovered and mixed with the liquid o-phenylenediamine in S3 for reuse.

[0061] Comparative Example 4

[0062] S1, slice the crude o-phenylenediamine and put it into a distillation tower for vacuum distillation at a distillation temperature of 135° C., remove the front fraction and tar, and obtain a crude o-phenylenediamine liquid; the tar contains p-phenylenediamine;

[0063] S2. In an air atmosphere, placing the crude o-phenylenediamine liquid into a distillation tower for secondary vacuum distillation at a distillation temperature of 155° C., condensing and recovering to obtain liquid o-phenylenediamine;

[0064] S3, mixing liquid o-phenylenediamine and deionized water in a mass ratio of 1:1.5, heating and stirring in an air atmosphere to obtain an o-phenylenediamine aqueous solution; cooling the o-phenylenediamine aqueous solution at 45° C. for crystallization, centrifuging to obtain crude o-phenylenediamine crystals; melting the crude o-phenylenediamine crystals, heating and stirring in an air atmosphere until completely melted, adding 0.2 wt % of sodium bisulfite, stirring evenly, and dehydrating to obtain o-phenylenediamine.

[0065] The mixed liquid containing p-phenylenediamine is crystallized again at 45° C., and p-phenylenediamine and waste liquid are obtained through solid-liquid separation; the waste liquid is recovered and mixed with the liquid o-phenylenediamine in S3 for reuse.

[0066] Comparative Example 5

[0067] S1, slice the crude o-phenylenediamine and put it into a distillation tower for vacuum distillation at a distillation temperature of 135° C., remove the front fraction and tar, and obtain a crude o-phenylenediamine liquid; the tar contains p-phenylenediamine;

[0068] S2. Under vacuum conditions, placing the crude o-phenylenediamine liquid into a distillation tower for secondary vacuum distillation at a distillation temperature of 155° C., condensing and recovering to obtain liquid o-phenylenediamine;

[0069] S3, mixing liquid o-phenylenediamine and deionized water in a mass ratio of 1:1.5, heating and stirring under nitrogen protection to obtain an o-phenylenediamine aqueous solution; cooling the o-phenylenediamine aqueous solution at 60° C. for crystallization, centrifuging to obtain crude o-phenylenediamine crystals and a mixed solution containing p-phenylenediamine; melting the crude o-phenylenediamine crystals, heating and stirring under nitrogen protection until completely melted, adding 0.2wt% sodium bisulfite and stirring evenly, and obtaining o-phenylenediamine after dehydration.

[0070] Comparative Example 6

[0071] The difference between this comparative example and Example 1 is that the sodium bisulfite in S3 is replaced by sodium sulfide.

[0072] The remaining raw materials and preparation process remain the same as in Example 1.

[0073] The yield, content and color change time of Examples 1 to 8 and Comparative Examples 1 to 6 were tested, wherein the yield = (o-phenylenediamine / crude o-phenylenediamine) * 100%; the color change time was tested at room temperature (20-25° C.) and humidity (40%-60%);

[0074] The results are shown in Table 1:

[0075] Table 1

[0076]

[0077]

[0078] Based on Table 1, the amount of antioxidant required to be added to Comparative Examples 1 to 4 to achieve the color change standard of the embodiment was tested and recorded, and the results are shown in Table 2:

[0079] Table 2

[0080] project Antioxidant (g) Color change time (h) content(%) Comparative Example 1 0.8 79 98.72 Comparative Example 2 1 78 98.68 Comparative Example 3 0.2 80 99.74 Comparative Example 4 2 77 97.88

[0081] As can be seen from Table 1, the comparison between Examples 2-3, 5-6 and Example 1 mainly reflects the influence of distillation temperature and crystallization temperature on yield and content; the comparison between Examples 4, 7-8 and Example 1 is only the replacement of raw materials within a reasonable range, and the final test results also show that they are almost the same. Compared with Example 1, in Comparative Example 1, after not performing secondary distillation, the macromolecular substances and polymers in the crude o-phenylenediamine will enter the next step, which will eventually lead to a decrease in the quality of the o-phenylenediamine product; in Comparative Example 2, no crystallization step is performed, which will make it difficult to remove p-phenylenediamine with a boiling point close to that of o-phenylenediamine, and will also lead to a decrease in the quality of the o-phenylenediamine product, which is specifically manifested in a decrease in content and discoloration in a shorter time; Compared with Example 1, Comparative Example 3 is mainly reflected in that without the addition of antioxidants, o-phenylenediamine changes color quickly in the air; Comparative Example 4 reflects the process of decoking in the distillation of o-phenylenediamine. The necessity of maintaining a vacuum and an inert gas atmosphere in the process is discussed; the difference between Comparative Example 5 and Example 1 is whether the mixed liquid containing p-phenylenediamine is recycled. After the waste liquid is recycled, not only the p-phenylenediamine product is obtained, but also the loss of o-phenylenediamine in the distillation and decoking process is reduced, and the water consumption is reduced, thereby improving the utilization rate of resources; the difference between Comparative Example 6 and Example 1 is that sodium sulfide is used as an antioxidant. Although sodium sulfide can prevent o-phenylenediamine from being oxidized to a certain extent, it reacts with oxygen to generate water and toxic gas sulfur dioxide, which is not conducive to the use and preservation of o-phenylenediamine.

[0082] It can be seen from Table 2 that although adding too much antioxidant can also achieve the effect of keeping o-phenylenediamine from changing color for a long time, it also reduces the content of o-phenylenediamine and reduces the product quality.

[0083] In summary, the o-phenylenediamine distillation and decoking process provided by the present invention improves the yield and content of the o-phenylenediamine finished product, does not change color for a long time in an air atmosphere, and improves the utilization rate of resources, and has good application prospects.

[0084] It should be noted that, in this article, relational terms such as first and second, etc. are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "include", "comprise" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device.

[0085] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A process for decoking o-phenylenediamine by distillation, characterized in that: The steps include: S1, cutting the crude o-phenylenediamine into pieces and putting them into a distillation tower for vacuum distillation to remove the front fraction and part of the tar to obtain a crude o-phenylenediamine liquid; the tar contains p-phenylenediamine; S2. Under vacuum conditions, placing the crude o-phenylenediamine liquid into a distillation tower for secondary vacuum distillation, condensing and recovering, to obtain liquid o-phenylenediamine; S3, mixing liquid o-phenylenediamine with deionized water, heating and stirring under nitrogen protection to obtain an o-phenylenediamine aqueous solution; cooling the o-phenylenediamine aqueous solution for crystallization, centrifuging to obtain crude o-phenylenediamine crystals and a mixed solution containing p-phenylenediamine; melting the crude o-phenylenediamine crystals, heating and stirring under nitrogen protection until completely melted, adding an antioxidant and stirring evenly, and dehydrating to obtain o-phenylenediamine; The mixed liquid containing p-phenylenediamine is crystallized again at 45-55° C., and p-phenylenediamine and waste liquid are obtained through solid-liquid separation; the waste liquid is recovered and mixed with the liquid o-phenylenediamine in S3 for reuse.

2. A process for decoking by distillation of o-phenylenediamine according to claim 1, characterized in that: The distillation temperature in S1 is 125-140°C, and the distillation temperature in S2 is 150-160°C.

3. A process for decoking by distillation of o-phenylenediamine according to claim 1, characterized in that: The mass ratio of the liquid o-phenylenediamine to deionized water is 1-1.5:1.5-2.

4. A process for decoking by distillation of o-phenylenediamine according to claim 1, characterized in that: The temperature of the cooling crystallization is 50°C to 80°C.

5. A process for decoking by distillation of o-phenylenediamine according to claim 1, characterized in that: The antioxidant is one of sodium bisulfite, sodium sulfite and sodium hydrosulfide.

6. A process for decoking by distillation of o-phenylenediamine according to claim 1, characterized in that: The mass ratio of the antioxidant to the crude o-phenylenediamine crystals is 0.2-0.4 g:100 g.

7. A process for decoking by distillation of o-phenylenediamine according to claim 1, characterized in that: The recrystallization temperature is 45-55°C.

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