Method for preparing 2, 3-dichloro-1, 4-naphthoquinone from DCB alkaline wastewater and application

Abstract

The invention provides a method for preparing 2, 3-dichloro-1, 4-naphthoquinone from DCB alkaline wastewater and application, and the method comprises the following steps: neutralizing the alkaline wastewater generated by hydrogenation reduction reaction in the DCB production process to be acidic by hydrochloric acid, then adding FeCl as a catalyst, introducing chlorine gas to carry out oxidation reaction on 2, 3-dichloro-1, 4-naphthol in the solution, and separating the 2, 3-dichloro-1, 4-naphthoquinone from the 2, 3-dichloro-1, 4-naphthoquinone in the solution to obtain the 2, 3-dichloro-1, 4-naphthoquinone. And reacting to generate 2, 3-dichloro-1, 4-naphthoquinone which is insoluble in water. And filtering the reacted 2, 3-dichloro-1, 4-naphthoquinone through a filter, and washing the filtered 2, 3-dichloro-1, 4-naphthoquinone with hot water to obtain a 2, 3-dichloro-1, 4-naphthoquinone product with the purity of 98% or above. The product can be used as an auxiliary agent in a DCB hydrogenation reduction reaction, plays a role in inhibiting side reactions, and can be reused in the production process. According to the method, waste discharge is effectively reduced, the production cost is reduced, waste recycling and resource circulation are achieved, and sustainable development of industrial production is facilitated. The process is simple and economic, is suitable for large-scale popularization and application, and has remarkable environmental protection benefits and economic benefits.

Description

Technical Field

[0001] The invention relates to the technical field of pigment intermediate wastewater treatment, and in particular to a method for preparing 2,3-dichloro-1,4-naphthoquinone from DCB alkaline wastewater and application thereof. Background Art

[0002] DCB (3,3'-dichlorobenzidine) is an important intermediate in the production of dichlorobenzidine-based yellow organic pigments, and is widely used in inks, paints, rubber, plastics and other fields. The production process of DCB involves complex chemical reactions, among which the hydrogenation reduction reaction will produce a large amount of alkaline wastewater containing 2,3-dichloro-1,4-naphthol. These wastewaters contain high concentrations of organic matter and COD (chemical oxygen demand), which cause serious pollution to the environment. If they are discharged directly without treatment, it will not only increase the environmental pressure of industrial production, but also may bring environmental regulatory risks. Therefore, how to effectively treat this type of high-COD wastewater has become a major problem in existing technologies.

[0003] Traditionally, this type of alkaline wastewater is usually treated by catalytic oxidation. However, this method has the following problems: High treatment cost: Although the catalytic oxidation method can effectively decompose organic matter, the catalysts and oxidants it uses are relatively expensive, which leads to an increase in the overall wastewater treatment cost and increases the production burden of the enterprise.

[0004] Waste of resources: Organic components in wastewater, such as 2,3-dichloro-1,4-naphthol, are valuable compounds in themselves. Traditional decomposition treatment methods fail to recycle these organic substances, but instead completely oxidize them, failing to achieve resource recycling.

[0005] Environmental pressure: With increasingly stringent environmental regulations, industrial enterprises are facing more stringent emission standards. The treatment technology of high COD wastewater needs to be optimized to reduce pollution to the environment and reduce the legal risks faced by enterprises due to excessive emissions.

[0006] In summary, in the prior art, the treatment methods for alkaline wastewater generated in the DCB production process mainly focus on high-cost catalytic oxidation methods or simple chemical treatment methods, which have the following obvious defects: Failure to achieve resource recycling: 2,3-Dichloro-1,4-naphthol in alkaline wastewater is a valuable organic matter, but the existing technology treats it as waste and fails to achieve effective recovery and recycling, resulting in waste of resources.

[0007] Low treatment efficiency: The traditional wastewater treatment process has limited treatment efficiency under high COD concentration conditions, and the organic matter in the wastewater is difficult to completely decompose, and certain pollutants may still remain.

[0008] Environmental issues: Existing treatment methods usually fail to effectively solve environmental problems. After treatment, wastewater may still contain high concentrations of residual substances, which still poses a pollution risk to the environment when discharged.

[0009] High cost operation: The existing process not only requires high-cost chemicals, but also involves complex process flows, resulting in high overall operating costs, especially in large-scale industrial production.

[0010] In addition, 2,3-dichloro-1,4-naphthoquinone, as a key inhibitor in the DCB hydrogenation reduction reaction, can effectively inhibit the occurrence of side reactions and improve reaction efficiency. However, due to its high market price, the cost of adding 2,3-dichloro-1,4-naphthoquinone to produce one ton of DCB is high, which increases the overall production cost. Therefore, how to reduce the cost of using 2,3-dichloro-1,4-naphthoquinone and reduce the generation of by-product waste has become the focus of the industry. Summary of the invention

[0011] The technical problem to be solved by the present invention is to provide a method for preparing 2,3-dichloro-1,4-naphthoquinone from DCB alkaline wastewater, so as to solve the problems of high alkaline wastewater treatment cost, resource waste and environmental pollution in the prior art, and to provide an environmentally friendly preparation method for resource recycling.

[0012] In order to solve the above technical problems, the present invention provides a method for preparing 2,3-dichloro-1,4-naphthoquinone from DCB alkaline wastewater, comprising the following steps: S1: After the alkaline wastewater produced by the DCB hydrogenation reduction reaction is neutralized to acidity, FeCL3 catalyst is added and then the temperature is raised to 90-95°C; S2: Under continuous stirring, introducing chlorine gas into the wastewater treated in step S1 to generate water-insoluble 2,3-dichloro-1,4-naphthoquinone which precipitates in a crystalline state to obtain a reaction solution; S3: After the step S2 is completed, the reaction solution is filtered to obtain a 2,3-dichloro-1,4-naphthoquinone filter cake, and the filter cake is washed with hot water to obtain a 2,3-dichloro-1,4-naphthoquinone product, thereby completing the preparation.

[0013] A method for preparing 2,3-dichloro-1,4-naphthoquinone from DCB alkaline wastewater in the present application has the following advantages compared with the prior art: In the prior art, the treatment of alkaline wastewater is usually treated by catalytic oxidation for decomposition. However, the present application neutralizes the wastewater to acidity with hydrochloric acid, adds FeCL3 catalyst, and then introduces chlorine to oxidize 2,3-dichloro-1,4-naphthol in the wastewater to 2,3-dichloro-1,4-naphthoquinone. This improvement transforms the originally complex wastewater treatment process into a resource recovery process, so that the by-products are effectively utilized; the present invention adjusts the pH value of the wastewater to acidity by adding hydrochloric acid, and uses chlorine to oxidize 2,3-dichloro-1,4-naphthoquinone in the wastewater to 2,3-dichloro-1,4-naphthoquinone under acidic conditions; since 2,3-dichloro-1,4-naphthoquinone is insoluble in water, a high-purity product can be obtained through simple filtering and washing steps. Through the method of the present invention, the recovery rate of 2,3-dichloro-1,4-naphthoquinone is improved and the complexity of wastewater treatment is reduced; and the purity of the generated 2,3-dichloro-1,4-naphthoquinone can reach more than 98%, which meets the requirements of production and use; the method of the present invention reduces the demand for raw materials and reduces the discharge of waste, and has significant economic benefits and environmental advantages.

[0014] As a preferred solution, in step S1, the alkaline wastewater is neutralized by adding a hydrochloric acid solution to the alkaline wastewater, and the concentration of the hydrochloric acid solution is 30-35%. After the neutralization, the pH of the wastewater is 1.0-1.5.

[0015] Compared with the prior art, the current production method of 2,3-dichloro-1,4-naphthoquinone products is mainly: using 1,4-naphthoquinone as a raw material, introducing chlorine into a solvent for chlorination reaction, and then purifying to obtain the product. The present invention adopts this technical solution to quickly neutralize the alkaline substances in the wastewater to an acidic environment, which provides suitable reaction conditions for the subsequent oxidation reaction of FeCl3 catalyst and chlorine, and promotes the oxidation reaction of organic matter more thoroughly through the acidic environment, ensuring the efficient conversion of 2,3-dichloro-1,4-naphthoquinone.

[0016] As a preferred solution, in step S1, the concentration of the hydrochloric acid solution is 31%.

[0017] As a preferred solution, in step S1, the added mass of the FeCL3 catalyst is 1-2% of the 2,3-dichloro-1,4-naphthoquinone product in the wastewater.

[0018] Compared with the prior art, the above technical solution achieves precise control of the amount of the catalyst by controlling the amount of FeCl3 catalyst added to 1-2% of the 2,3-dichloro-1,4-naphthoquinone product in the wastewater, thereby avoiding adverse reactions caused by excessive or insufficient catalysts. FeCl3 as a catalyst can effectively promote the conversion of reactants and improve reaction efficiency, and within the addition range, the catalyst can fully play its role without causing side reactions or waste of materials due to excessive amount; the efficient progress of the reaction is ensured, while the generation of by-products is reduced and the purity of 2,3-dichloro-1,4-naphthoquinone is improved; the amount of FeCl3 catalyst forms an optimal ratio with the target reaction substance in the wastewater, so that the catalyst can maximize its catalytic effect, while avoiding the negative impact of excessive catalyst on system stability, cost and environmental burden; this precise amount of catalyst added not only ensures a high reaction rate and a high conversion rate, but also can further reduce the cost of treating wastewater and the amount of by-products generated, especially improves the yield and purity of 2,3-dichloro-1,4-naphthoquinone, reduces unnecessary reaction steps and material consumption, and makes the entire process more economical and environmentally friendly.

[0019] As a preferred solution, in step S2, the chlorine gas is introduced for 4-5 hours, and the amount introduced is 1.2-1.5 times the weight of 2,3-dichloro-1,4-naphthol in the alkaline wastewater.

[0020] Compared with the prior art, the present invention controls the time and amount of chlorine gas introduced, and adopts the above-mentioned chlorine gas introduction parameters to ensure the full oxidation reaction, and completes the oxidation of organic matter by a sufficient amount of chlorine gas participating in the reaction to generate high-purity, water-insoluble 2,3-dichloro-1,4-naphthoquinone crystals, and further controls the reaction time to make the reaction more sufficient. The time and amount of chlorine gas introduction directly determine the oxidation effect of the reaction. Too short a chlorine gas introduction time or insufficient introduction amount will lead to a decrease in conversion rate, and vice versa, it will affect the purity of the generated product.

[0021] As a preferred solution, in step S3, the temperature of the hot water is 60-65°C, and the hot water is added quantitatively, and its mass is 5-10% of the alkaline wastewater.

[0022] Compared with the prior art, the preferred scheme of the present invention adopts hot water washing, which can effectively remove impurities and ensure the purity of the filter cake. The impurities are dissolved by moderate hot water, especially in the temperature range of 60-65°C, which ensures that the product purity reaches more than 98%, avoiding the impact of impurities on product quality.

[0023] As a preferred solution, in step S3, the purity of the 2,3-dichloro-1,4-naphthoquinone product is greater than 98%.

[0024] Compared with the prior art, the method of the present invention can obtain a high-purity product, and by precisely controlling each reaction step, it is ensured that the product does not contain unnecessary impurities. The final technical effect is that the high-purity 2,3-dichloro-1,4-naphthoquinone product can be directly reused in the DCB hydrogenation reduction reaction, reducing the demand and cost of external raw materials.

[0025] As a preferred solution, the reaction process of steps S1-S2 includes: .

[0026] Compared with the prior art, the above reaction process of the present invention can realize the efficient conversion of 2,3-dichloro-1,4-naphthol through the effective action of FeCl3 catalyst, and optimize the reaction conditions by controlling the reaction temperature and the amount of chlorine gas introduced to ensure the generation of high-purity 2,3-dichloro-1,4-naphthoquinone. At the same time, by optimizing various parameters, the present invention realizes the transformation of waste into treasure in wastewater treatment, and forms an environmentally friendly and economical process route.

[0027] Compared with the prior art, the above-mentioned reaction process of the present invention has the following advantages: Environmental protection and resource recycling: The existing method of directly treating wastewater is changed to recovering 2,3-dichloro-1,4-naphthol in the wastewater and oxidizing it to 2,3-dichloro-1,4-naphthoquinone, so that the waste can be reused as a resource, waste emissions can be reduced, and production costs can be reduced.

[0028] Cost reduction: Through the treatment process of the present invention, the external purchase of expensive additives is reduced, and the required additives are prepared by utilizing the components in the DCB wastewater, thereby achieving recycling and reducing production costs.

[0029] Simple and efficient: This method is simple to operate and uses conventional industrial means such as hydrochloric acid neutralization and chlorine oxidation. The purity of the produced 2,3-dichloro-1,4-naphthoquinone is higher than 98%, which can be directly used for hydrogenation reduction reaction, reducing external processing links and improving production efficiency.

[0030] The present invention also provides an application of the 2,3-dichloro-1,4-naphthoquinone prepared by the preparation method, which comprises reusing the 2,3-dichloro-1,4-naphthoquinone prepared by the preparation method as an auxiliary agent in a DCB hydrogenation reduction reaction.

[0031] Compared with the prior art, the application of 2,3-dichloro-1,4-naphthoquinone prepared by the above preparation method in the present application has the following advantages: the above application in the present invention replaces the high cost and waste of resources of externally purchased auxiliary agents in the prior art with the recycling of 2,3-dichloro-1,4-naphthol in wastewater to prepare auxiliary agents, and recovers 2,3-dichloro-1,4-naphthoquinone from wastewater and reuses it as a reaction auxiliary agent in the DCB hydrogenation reduction reaction, thereby reducing production costs and reducing dependence on external raw materials. The production cost is significantly reduced, waste emissions are reduced, and resource recycling is achieved. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 This is the gas chromatography analysis diagram of 2,3-dichloro-1,4-naphthoquinone produced from DCB alkaline wastewater. DETAILED DESCRIPTION

[0033] First, those skilled in the art should understand that these implementations are only used to explain the technical principles of the embodiments of the present application, and are not intended to limit the protection scope of the embodiments of the present application. Those skilled in the art can make adjustments to them as needed to adapt to specific application scenarios.

[0034] The present invention provides a method for preparing 2,3-dichloro-1,4-naphthoquinone from DCB alkaline wastewater, comprising the following steps: S1: After the alkaline wastewater produced by the DCB hydrogenation reduction reaction is neutralized to acidity, FeCL3 catalyst is added and then the temperature is raised to 90-95°C; S2: Under continuous stirring, introducing chlorine gas into the wastewater treated in step S1 to generate water-insoluble 2,3-dichloro-1,4-naphthoquinone which precipitates in a crystalline state to obtain a reaction solution; S3: After the step S2 is completed, the reaction solution is filtered to obtain a 2,3-dichloro-1,4-naphthoquinone filter cake, and the filter cake is washed with hot water to obtain a 2,3-dichloro-1,4-naphthoquinone product, thereby completing the preparation.

[0035] As a preferred solution, in step S1, the alkaline wastewater is neutralized by adding a hydrochloric acid solution to the alkaline wastewater, and the concentration of the hydrochloric acid solution is 30-35%. After the neutralization, the pH of the wastewater is 1.0-1.5.

[0036] As a preferred solution, in step S1, the concentration of the hydrochloric acid solution is 31%.

[0037] As a preferred solution, in step S1, the added mass of the FeCL3 catalyst is 1-2% of the 2,3-dichloro-1,4-naphthoquinone product in the wastewater.

[0038] As a preferred solution, in step S2, the chlorine gas is introduced for 4-5 hours, and the amount introduced is 1.2-1.5 times the weight of 2,3-dichloro-1,4-naphthol in the alkaline wastewater.

[0039] As a preferred solution, in step S3, the temperature of the hot water is 60-65°C, and the hot water is added quantitatively, and its mass is 5-10% of the alkaline wastewater.

[0040] As a preferred solution, in step S3, the purity of the 2,3-dichloro-1,4-naphthoquinone product is greater than 98%.

[0041] As a preferred solution, the reaction process of steps S1-S2 includes: .

[0042] The present invention also provides an application of the 2,3-dichloro-1,4-naphthoquinone prepared by the preparation method, which comprises reusing the 2,3-dichloro-1,4-naphthoquinone prepared by the preparation method as an auxiliary agent in a DCB hydrogenation reduction reaction.

[0043] The above technical solution of the present invention is further described below in combination with specific reaction conditions and reaction equipment: Example 1 S1: Install a 3L four-necked flask with stirring in a water bath, add 2000mL of alkaline wastewater produced by DCB hydrogenation reduction reaction, start stirring, add 31% hydrochloric acid to neutralize to pH=1.0, then add 0.3g of FeCL3 catalyst, and heat to 90℃ in a water bath; S2: Slowly pass chlorine through a glass tube inserted into the four-necked flask under the liquid, control the chlorine introduction rate at 6g / h, complete the chlorine introduction time in 5 hours, control the reaction temperature at 90-95°C, and pass 30g of chlorine in total.

[0044] S3: After the chlorine gas is passed, the 2,3-dichloro-1,4-naphthoquinone precipitate in the reaction solution is filtered through a Buchner funnel, and then the filter cake is washed with 100 mL of 60°C hot water. The weight of the obtained filter cake after drying is 21.5 grams. The purity of the sample after gas chromatography is 98.87%: Example 2 S1: Install a 3L four-necked flask with stirring in a water bath, add 2000mL of alkaline wastewater produced by DCB hydrogenation reduction reaction, start stirring, add 31% hydrochloric acid to neutralize to pH=1.4, then add 0.4g of FeCL3 catalyst, and heat to 95℃ in a water bath; S2: Slowly pass chlorine through a glass tube inserted into the four-necked flask under the liquid, control the chlorine gas flow rate at 6g / h, the chlorine flow time is completed in 4 hours, control the reaction temperature at 90-95°C, and the total amount of chlorine gas passed is 24g.

[0045] S3: After the chlorine gas is passed, the 2,3-dichloro-1,4-naphthoquinone precipitate in the reaction solution is filtered through a Buchner funnel, and then the filter cake is washed with 100 mL of 60°C hot water. The weight of the obtained filter cake after drying is 21 grams. The purity of the sample after gas chromatography is 98.86%.

[0046] Example 3 S1: Install a 3L four-necked flask with stirring in a water bath, add 2000mL of alkaline wastewater produced by DCB hydrogenation reduction reaction, start stirring, add 31% hydrochloric acid to neutralize to pH=1.5, then add 0.4g of FeCL3 catalyst, and heat to 95℃ in a water bath; S2: Chlorine was slowly introduced through a glass tube inserted into the four-necked flask. The amount of chlorine introduced was controlled at 6 g / h. The chlorine introduction time was completed in 4.5 hours. The reaction temperature was controlled at 90-95°C. A total of 27 g of chlorine was introduced.

[0047] S3: After the chlorine gas is passed, the 2,3-dichloro-1,4-naphthoquinone precipitate in the reaction solution is filtered through a Buchner funnel, and then the filter cake is washed with 100 mL of 65°C hot water. The weight of the obtained filter cake after drying is 22 grams. The purity of the sample after gas chromatography is 98.92%.

[0048] Through the above examples, it is also further explained that the present invention provides a method and application for preparing 2,3-dichloro-1,4-naphthoquinone from DCB alkaline wastewater. The method effectively utilizes 2,3-dichloro-1,4-naphthol in the alkaline wastewater generated in the DCB production process, and successfully converts it into high-purity 2,3-dichloro-1,4-naphthoquinone by neutralization with hydrochloric acid, oxidation with chlorine, and catalysis with FeCl3. The product can not only be reused as an auxiliary agent in the DCB hydrogenation reduction reaction, but also reduces waste discharge, reduces production costs, and realizes the resource recycling of industrial wastewater. Compared with the prior art, the present invention has significant advantages: by changing the high-cost wastewater treatment method in the prior art to the resource utilization of organic matter in the wastewater, the present invention shows superiority in environmental protection and economic benefits, and by carrying out an effective catalytic oxidation reaction under acidic conditions, the reaction yield is high, the product purity reaches more than 98%, and the generated 2,3-dichloro-1,4-naphthoquinone can be recycled and used in the production process, forming a closed-loop production chain. This not only further reduces the procurement cost of additives, but also reduces the dependence on external additives.

[0049] Therefore, the present invention provides a sustainable wastewater treatment and resource recycling solution for the pigment intermediate production field, has high industrial application prospects, and can contribute to the green development of the industry.

[0050] In the description of the present application, the description with reference to the terms "one embodiment", "some embodiments", "in the present embodiment", "specific example", or "some examples" etc. means that the specific features, mechanisms, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present application. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, mechanisms, materials or characteristics described may be combined in a suitable manner in any one or more embodiments or examples. In addition, those skilled in the art may combine and combine the different embodiments or examples described in this specification and the features of the different embodiments or examples, without contradiction.

[0051] The above is only a specific implementation of the present application, but the protection scope of the present application is not limited thereto. Any changes or substitutions that can be easily thought of by a person skilled in the art within the technical scope disclosed in the present application should be included in the protection scope of the present application. Therefore, the protection scope of the present application shall be based on the protection scope of the claims.

Claims

1. A method for preparing 2,3-dichloro-1,4-naphthoquinone from DCB alkaline wastewater, characterized in that: The following steps are involved: S1: After the alkaline wastewater produced by the DCB hydrogenation reduction reaction is neutralized to acidity, FeCL3 catalyst is added and then the temperature is raised to 90-95°C; S2: Under continuous stirring, introducing chlorine gas into the wastewater treated in step S1 to generate water-insoluble 2,3-dichloro-1,4-naphthoquinone which precipitates in a crystalline state to obtain a reaction solution; S3: After the step S2 is completed, the reaction solution is filtered to obtain a 2,3-dichloro-1,4-naphthoquinone filter cake, and the filter cake is washed with hot water to obtain a 2,3-dichloro-1,4-naphthoquinone product, thereby completing the preparation.

2. The method for preparing 2,3-dichloro-1,4-naphthoquinone from DCB alkaline wastewater according to claim 1, characterized in that: In the step S1, the alkaline wastewater is neutralized by adding a hydrochloric acid solution to the alkaline wastewater, and the concentration of the hydrochloric acid solution is 30-35%. After the neutralization, the pH of the wastewater is 1.0-1.

5.

3. The method for preparing 2,3-dichloro-1,4-naphthoquinone from DCB alkaline wastewater according to claim 2, characterized in that: In step S1, the concentration of the hydrochloric acid solution is 31%.

4. The method for preparing 2,3-dichloro-1,4-naphthoquinone from DCB alkaline wastewater according to claim 1, characterized in that: In the step S1, the added mass of the FeCL3 catalyst is 1-2% of the 2,3-dichloro-1,4-naphthoquinone product in the wastewater.

5. The method for preparing 2,3-dichloro-1,4-naphthoquinone from DCB alkaline wastewater according to claim 1, characterized in that: In the step S2, the chlorine gas is introduced for 4-5 hours, and the amount introduced is 1.2-1.5 times the weight of 2,3-dichloro-1,4-naphthol in the alkaline wastewater.

6. The method for preparing 2,3-dichloro-1,4-naphthoquinone from DCB alkaline wastewater according to claim 1, characterized in that: In step S3, the temperature of the hot water is 60-65° C., and the hot water is added quantitatively, and its mass is 5-10% of the alkaline wastewater.

7. The method for preparing 2,3-dichloro-1,4-naphthoquinone from DCB alkaline wastewater according to claim 1, characterized in that: In step S3, the purity of the 2,3-dichloro-1,4-naphthoquinone product is greater than 98%.

8. The method for preparing 2,3-dichloro-1,4-naphthoquinone from DCB alkaline wastewater according to claim 1, characterized in that: The reaction process of steps S1-S2 includes: 。 9. Use of 2,3-dichloro-1,4-naphthoquinone obtained by any one of the preparation methods of claims 1 to 8, characterized in that: The application includes using the 2,3-dichloro-1,4-naphthoquinone prepared by any one of the preparation methods of claims 1 to 8 as an auxiliary agent in the DCB hydrogenation reduction reaction.

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