A clean production process for cationic dyes

Abstract

The invention discloses a clean production process for cationic dyes. A parent substance and dimethyl sulfate undergo a methylation reaction, followed by expansion and hydrolysis. Salt and zinc chloride are added for transformation and crystallization. After crystallization, the product and mother liquor wastewater are filtered. Zinc chloride and sodium chloride are added to the mother liquor wastewater obtained after crystallization for neutralization. After nanofiltration, the concentrated solution is applied to the hydrolysis and expansion process of the next batch. The wastewater after nanofiltration enters a biochemical treatment system. The clean production process of the invention can solve the problems of generating and applying crystallization wastewater, reduce wastewater treatment costs, increase product yield, reduce wastewater generation and salt usage, and recover a small amount of cationic dye dissolved in the wastewater.

Description

Technical Field

[0001] The invention belongs to the technical field of dye production, relates to the clean production of dyes, and in particular to a clean production process of cationic dyes which can improve product yield and reduce wastewater treatment costs. Background Art

[0002] Cationic dyes are a type of textile dye, specialized for dyeing and printing polyacrylonitrile, fabrics, and blends made with other fibers. They feature vibrant colors, excellent performance, ease of use, and high exhaustion rates. However, cationic dyes generate large volumes of wastewater with complex composition, high COD and salt content, and low pH.

[0003] The synthesis process of Basic Red 46 is as follows: the parent body and dimethyl sulfate undergo methylation reaction, followed by hydrolysis, and then salt and zinc chloride are added for transformation crystallization. After crystallization, the finished product and wastewater are obtained by filtration.

[0004] Normal Basic Red 46 crystallization produces excessive wastewater and is difficult to treat. The water used for hydrolysis and expansion is essential during the reaction. The small volume results in incomplete hydrolysis of the material, resulting in an abnormal, oily morphology that prevents subsequent crystallization. The large volume also increases wastewater production. The original wastewater treatment solution involved multiple-effect evaporation, with the precipitated salt recovered and landfilled, but this method consumes excessive energy. Summary of the Invention

[0005] In order to solve the above problems, the present invention provides a clean production process for cationic dyes. The clean production process of the present invention can solve the problems of the generation and application of crystallization wastewater, reduce the cost of wastewater treatment, and at the same time increase the yield of the product, reduce the amount of wastewater generated and the amount of salt used, and recover a small amount of cationic dye dissolved in the wastewater.

[0006] In order to achieve the above object, the present invention adopts the following technical solutions:

[0007] A clean production process for cationic dyes comprises the following steps: a mother body and dimethyl sulfate undergo a methylation reaction, followed by expansion and hydrolysis, and the addition of salt and zinc chloride for transformation and crystallization. After crystallization, the mother liquid wastewater is filtered to obtain a finished product and mother liquid wastewater. Soda ash is added to the mother liquid wastewater obtained after crystallization for neutralization, and after nanofiltration treatment, the concentrated liquid is applied to the hydrolysis and expansion process of the next batch. The wastewater after nanofiltration enters a biochemical treatment system.

[0008] As a preferred solution of the present invention, when applied, the amount of sodium chloride added is 20%-30% of the original amount.

[0009] As a preferred embodiment of the present invention, after the nanofiltration treatment, the temperature of the concentrated liquid is 20°C-40°C.

[0010] As a preferred solution of the present invention, when applied, the amount of zinc chloride added is 70-80% of the original amount.

[0011] As a preferred embodiment of the present invention, the concentrated liquid after nanofiltration treatment is concentrated by 30%.

[0012] As a preferred embodiment of the present invention, the mother liquor wastewater contains 9 wt% of sodium chloride, 3 wt% of methanol, 3 wt% of zinc chloride, 2 wt% of magnesium sulfate, and 4 wt% of other organic dyes.

[0013] As a preferred embodiment of the present invention, the wastewater after nanofiltration contains 6 wt % of sodium chloride, 6 wt % of methanol, 0.5 wt % of magnesium sulfate, 0.2 wt % of zinc chloride, and 0.2 wt % of other organic impurities.

[0014] As a preferred solution of the present invention, the number of applications is 1-5 times.

[0015] Compared with the prior art, the present invention has the following beneficial effects:

[0016] 1) The clean production process of the present invention can reduce wastewater treatment costs and raw material costs by approximately RMB 5,000 per ton of finished dye synthesized.

[0017] 2) The clean production process of the present invention saves water. For every ton of dry powder synthesized, 6 tons of water is saved and 1 ton of solid waste landfill is reduced.

[0018] 3) The clean production process of the present invention can increase the yield by 5-8%.

[0019] 4) The clean production process of the present invention can effectively reduce the concentration of small molecular organic matter such as methanol generated in the system. This part of methanol enters the boiling water after nanofiltration and enters the biochemical system to provide nutrients for biochemical bacteria. At the same time, the dye in the mother liquor wastewater can be effectively recovered, so that the entire production system reaches a dynamic balance. DETAILED DESCRIPTION

[0020] In order to make the technical means, creative features, purpose and efficacy of the present invention easy to understand, the present invention is further described below in conjunction with specific examples, but the following examples are only preferred embodiments of the present invention, not all. Based on the examples in the embodiments, other embodiments obtained by those skilled in the art without making creative work are within the scope of protection of the present invention. The experimental methods in the following examples, unless otherwise specified, are conventional methods, and the materials, reagents, etc. used in the following examples, unless otherwise specified, can be obtained from commercial channels.

[0021] The clean production process of the cationic dye of the present invention is an improvement made on the basis of the existing preparation of the cationic dye.

[0022] The existing synthesis of cationic dyes is to undergo a methylation reaction between a parent body and dimethyl sulfate, followed by hydrolysis, and then add salt and zinc chloride for transformation crystallization. After crystallization, the finished product and wastewater are obtained by filtration.

[0023] The main reaction equation is as follows:

[0024]

[0025] The hydrolysis and side reaction equations are as follows:

[0026]

[0027] The present invention recovers and reuses the wastewater generated in the process (which contains 9% sodium chloride, 3% methanol, 3% zinc chloride, 2% magnesium sulfate, and 4% other organic dyes), thereby reducing the amount of wastewater generated and the amount of salt used, and recovering a small amount of cationic dyes dissolved in the wastewater.

[0028] During the synthesis process, based on a single batch feed amount of 2.5 kmol, a single batch produces 2 tons of crystalline dye filter cake, with a dry yield of 1 ton of dry powder, wherein the filter cake has a solid content of 50% and contains 1 ton of crystallization mother liquor water.

[0029] In a single batch, 3 tons of material was methylated and 6 tons of material was hydrolyzed and expanded. The temperature was raised to 60°C, and a certain amount of zinc chloride and 10% volume of sodium chloride were added. The material was cooled to 40-45°C under stirring, and crystallized. The dye cake was obtained by filtration.

[0030] During the crystallization process, the total weight is 10 tons, of which 2 tons are filter cakes, 8 tons are mother liquor water, and 6 tons are used in subsequent batches. It is necessary to treat and concentrate about 2 tons of wastewater with membranes. The salt content of the mother liquor water is 10%, and its salt content is mainly sodium chloride. In subsequent batches, a certain amount of zinc chloride (reactant) is still added according to the process. According to the salt content of the mother liquor water, the use of sodium chloride and zinc chloride is reduced. In actual application, the sodium chloride added to each batch of materials is about 20% of the original amount, and the zinc chloride is about 80% of the original amount.

[0031] The membrane wastewater and concentrate are used in the next batch and are hydrolyzed and expanded before crystallization. The COD content of the membrane effluent is significantly reduced and can be discharged after biochemical treatment. The nanofiltration membrane uses imported nanofiltration membrane (GH8040). The mother liquor temperature after nanofiltration treatment is 30-40℃, which can be applied to subsequent batch expansion, which can reduce energy loss.

[0032] During the nanofiltration process, the concentration of small organic molecules, such as methanol, generated in the system can be effectively reduced. This methanol enters the membrane wastewater and the biochemical system, providing nutrients for biochemical bacteria. Simultaneously, the dye in the applied mother liquor is effectively recovered, achieving a dynamic equilibrium in the entire production system. Following these improvements, the product yield of the entire production system can be significantly improved.

[0033] The present invention is the best solution found by the inventors after comparing several solutions:

[0034] Specifically:

[0035] Option 1: The mother liquor water is concentrated by distillation, and the methanol is recovered and reused.

[0036] Option 2: The mother liquor water is evaporated by multiple effects and then reused.

[0037] Option 3: The mother liquor water is treated by nanofiltration membrane, the wastewater discharged from the membrane is applied, and the concentrated liquid is spray-dried.

[0038] The present invention: the mother liquor water is treated by nanofiltration membrane, concentrated in a small amount, and the concentrated liquid is used to perform biochemical treatment on the wastewater passing through the membrane.

[0039] Comparison Conclusion: All Schemes 1-3 have significant drawbacks. Scheme 1 requires high equipment requirements for methanol recovery, requires a large investment, and has no significant benefits (the methanol concentration in the wastewater is low and the amount is small); Scheme 2 consumes a lot of energy; and Scheme 3 is costly and has no significant benefits. The technical solution of the present invention only requires a set of membrane treatment equipment to perfectly solve the problem of wastewater generation and utilization, reducing wastewater treatment costs while increasing yield.

[0040] Example 1

[0041] Based on the existing preparation method, the methylation reaction of the Basic Red 46 product reaches the end point, and the concentrated crystallization wastewater is added to expand the volume by 70%. Hydrolysis is carried out, salt is added, and zinc chloride crystallization is filtered to obtain the finished product and mother liquor wastewater. Soda ash is added to the mother liquor wastewater obtained after crystallization for neutralization. After nanofiltration treatment, the concentrated liquid is used for the hydrolysis and expansion process of the next batch. The wastewater after nanofiltration enters the biochemical treatment system.

[0042] When applied, the amount of sodium chloride added is 20%-30% of the original amount.

[0043] After nanofiltration treatment, the temperature of the concentrated liquid is 20°C-40°C.

[0044] When applied, the amount of zinc chloride added is 70-80% of the original amount.

[0045] This embodiment is a laboratory test.

[0046] The results were shown in Table 1.

[0047] Table 1. Wastewater application results

[0048] batch Yield / g Color Light Nylon staining Normal synthesis 1 97.8 Brilliant 4+Red 4+Blue 2+ qualified Normal synthesis 2 98.3 Bright 2+Red 2+Blue 1+ qualified Normal synthesis 3 97.9 Bright 2+Red 2+Blue 1+ qualified The first batch of wastewater application 105.9 Bright 3+Red 3+Blue 2+ qualified Second batch of wastewater reuse 105.8 Bright 2+Red 3+Blue 3+ qualified The third batch of wastewater application 106.2 Bright 3+Red 3+Blue 2+ qualified

[0049] As can be seen from Table 1, before and after the application of wastewater, the yield was significantly increased by 6-8%, and the color light was 1-2 levels bluer, which had little impact.

[0050] Example 2

[0051] Based on the existing preparation method, the methylation reaction of the Basic Red 46 product reaches the end point, and the concentrated crystallization wastewater is added to expand the volume by 70%. Hydrolysis is carried out, salt is added, and zinc chloride crystallization is filtered to obtain the finished product and mother liquor wastewater. Soda ash is added to the mother liquor wastewater obtained after crystallization for neutralization. After nanofiltration treatment, the concentrated liquid is used for the hydrolysis and expansion process of the next batch. The wastewater after nanofiltration enters the biochemical treatment system.

[0052] When applied, the amount of sodium chloride added is 20%-30% of the original amount.

[0053] After nanofiltration treatment, the temperature of the concentrated liquid is 20°C-40°C.

[0054] When applied, the amount of zinc chloride added is 70-80% of the original amount.

[0055] This embodiment is a workshop production.

[0056] The results were shown in Table 2.

[0057] Table 2. Wastewater application results

[0058]

[0059] As shown in Table 2, after the workshop applied the wastewater, the color light became 1-2 levels bluer and the yield increased by 5-8%.

[0060] The above description is only a preferred embodiment of the present invention and does not limit the present invention in any form or substance. It should be pointed out that ordinary technicians in this technical field can make several improvements and supplements without departing from the method of the present invention. These improvements and supplements should also be regarded as the scope of protection of the present invention. Any equivalent changes, modifications and evolutions made by technicians familiar with this profession without departing from the spirit and scope of the present invention by using the technical content disclosed above are all equivalent embodiments of the present invention; at the same time, any equivalent changes, modifications and evolutions made to the above embodiments based on the essential technology of the present invention are still within the scope of the technical solution of the present invention.

Claims

1. A clean production process for cationic dyes, wherein the matrix and dimethyl sulfate undergo methylation reaction, followed by expansion and hydrolysis, and sodium chloride and zinc chloride are added for transformation and crystallization, and after crystallization, the finished product and mother liquor wastewater are obtained by filtration, characterized in that: Soda ash is added to the mother liquor wastewater obtained after crystallization for neutralization. After nanofiltration treatment, the concentrated liquid is used in the hydrolysis and expansion process of the next batch. The wastewater after nanofiltration enters the biochemical treatment system; When applied, the amount of sodium chloride added is 20%-30% of the original amount; After the nanofiltration treatment, the temperature of the concentrated liquid is 20° C.-40° C.; When applying, the amount of zinc chloride added is 70%-80% of the original amount; The wastewater after nanofiltration contains 6wt% of sodium chloride, 6wt% of methanol, 0.5wt% of magnesium sulfate, 0.2wt% of zinc chloride, and 0.2wt% of other organic impurities; The number of applications is 1-5 times.

2. A clean production process for cationic dyes according to claim 1, characterized in that, The concentrate after nanofiltration was concentrated by 30%.

3. A clean production process for cationic dyes according to claim 1, characterized in that, The mother liquid wastewater contains 9 wt % of sodium chloride, 3 wt % of methanol, 3 wt % of zinc chloride, 2 wt % of magnesium sulfate and 4 wt % of other organic dyes.

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